Anyone use an ACR?

[psneeld]

Thank you as always for great info, posts and a great refetence site..

....but.....what I got at the time was not what I wanted so I use an on/ off switch instead as you suggest...not as some aware of as a good compromise.

Unfortunately when I bought it...there was no indication this would be an issue.

Now as tech comes out, I do a lot more research first.

Anyone want to buy a small, earlier model ACR, lightly used...

 

[JDCAVE]

CMS: Thanks for another one of your extremely informative posts! I am however pleased that it supports my own layman's understanding.

Your preamble suggests to me that use of an ACR under situations where the charging voltage is fluctuating may be problematic. That would seem to be true during solar charging when the incoming current might be less than the outgoing loads from the systems on the house bank, such as refrigeration. I observed this last summer with my solar system. While I have the Blue Seas ACR, I have pretty much disabled its use and rely instead on the Mastervolt Battery mate to charge my house bank. That means that my solar panels are only used to charge the house bank when on the hook.

CMS: "For what it is worth a number of years ago I ran an experiment with a 55HP diesel where the alternator was disabled, on purpose. This was done to figure out how many starts one could achieve off the single G-31 "deep cycle" battery. After starting that motor 42 times, I grew tired and gave up. The next morning the resting voltage of the single G-31 "deep cycle", after starting the motor 42 times, had rebounded to a resting OCV of 12.57V"

I inadvertently ran a similar experiment during my first year of boat ownership: My old-school shipwright told me to never combined the house and starter bank and neither one of us understood the function of the Blue Sea ACR, so I switched it to the manual "off" position. I was under the mistaken impression that the Start battery was being charged with the Balmar Duocharge but that was being used to charge the thruster bank instead. I had just replaced the start batteries with 2 new Group 24's in parallel. I operated the boat for a week, starting the engine and raising an lowering the anchor WITH NO CHARGING SOURCE TO THE START BATTERY. I had a young marine electrician come aboard to look over my system and he determined that the starter bank was at 12.5 volts. I installed a small Prosport 6 to charge the starter bank while on shore power and a Mastervolt Battery Mate to charge the house and start batteries from the alternator source. The Blue Seas ACR is redundant should the Mastervolt fail for some reason.

Jim

 

[Delfin]

#4 In almost every installation, on a cruising boat with disparate sized battery banks, charge sources current should feed the house bank first & not the start bank. This prevents relay cycling because it allows the larger house bank to attain the combine voltage before combining with the much smaller, and almost always nearly fully charged, start battery.

#5 Feeding house first also results in faster charging & better voltage sense accuracy of the house bank. When you avoid relay cycling, the house bank charges faster. With less voltage drop between the charge source and the house battery pos terminal, that comes from not sticking a relay, multiple terminals and two more fuses it is path, the charge performance of the house bank is improved.

Blue Sea doesn't help get this point across with their wiring diagram, which shows an outboard motor alternator connected first to the starter bank, then a second battery. Both batteries are shown to be the same, with no other charging sources so it is correct under those circumstances. However, with cruising boats you have a large house bank and a small starter bank with additional charge sources. As you say, connecting charge sources first to the house bank makes the most sense.

If you are practicing good battery management, and have even the minimum suggested charge current for an AGM battery (Lifeline recommends a bare minimum of 20% of Ah capacity or .2C) this is simply a non-issue.

In just 2 minutes of charging, at .2C / 20% of Ah capacity beginning from 50% SOC, the AGM battery voltage is already at the “combine level” for a Blue Sea ACR. Once at 13.0V the relay has a delay of 90 seconds before combining/paralleling the banks. So, from 50% SOC with a .2C charge rate, it will take approx 3:30 for the relay to combine with the start battery and begin charging it. 90 seconds of this 3:30 is a built in timer delay in the ACR logic. In other words in just 2 minutes you're house bank is already at the combine/parallel level if charging at .2C with AGM batteries. Bump the charge current to .25 -.4C (where it really should be for AGM's) and the bank is attaining combine voltage almost instantly.

They key here is the presumption that .2C is the minimum acceptable charge current for an AGM bank. Sounds like Insequent has that, but Delfin certainly did not. With a 1284 24vdc Northstar AGM bank and a 120 amp (detuned) alternator, I was half that, and I presume that explains why I never saw the combine voltage reached for a hour or two. BTW, that bank lasted 10 years through hundreds and hundreds of cycles and was still going strong when I replaced it with LiFePO4. And, it seems the opinion that high C rates are best isn't shared by all manufacturers:

Optima: "Low and slow is best. A low amp charger (one to 12 amps) is generally the best choice for charging any lead-acid battery. It's quicker to charge at higher amperage, but it also can generate a lot of heat, which reduces the life of a battery, just like the heat of summer."

Victron views .2C as the maximum, not the minimum: "The charge current should preferably not exceed 0,2C (20A for a 100Ah battery).The temperature of a battery will increase by more than 10°C if the charge current exceeds 0,2C. Therefore temperature compensation is required if the charge current exceeds 0,2C."

 

[JDCAVE]

They key here is the presumption that .2C is the minimum acceptable charge current for an AGM bank. Sounds like Insequent has that, but Delfin certainly did not. With a 1284 24vdc Northstar AGM bank and a 120 amp (detuned) alternator, I was half that...

I'm about half that too: 125 amptech alternator on the engine and a 125 amp charging system on the Magnum 2812 for my 1175 amp hour house bank, which I think loosely works out to a 0.1 C. Now I rarely let my bank go below 80% SOC based on the 1175 input for the house bank. It's 4 years old now, so probably less than that.

Jim

 

[FlyWright]

Same here...I run a 660AH LA bank with a 55A shore charger. The shore charger gets powered by the Honda generator on the hook. This equates to 0.08C and typically requires a 3 hr run per day to restore the day's electrons. Why 55A? Because the Honda generator is limited to 13.3A continuous and 13A is the peak charger requirement.

My alternator puts out 100A and provides 0.15C. A 2 hr boat ride typically restores all the lost electrons from the previous day. I also looked at the 0.2C as a maximum, not a minimum or optimum target.

 

[CMS]

Blue Sea doesn't help get this point across with their wiring diagram, which shows an outboard motor alternator connected first to the starter bank, then a second battery. Both batteries are shown to be the same, with no other charging sources so it is correct under those circumstances. However, with cruising boats you have a large house bank and a small starter bank with additional charge sources. As you say, connecting charge sources first to the house bank makes the most sense.



They key here is the presumption that .2C is the minimum acceptable charge current for an AGM bank. Sounds like Insequent has that, but Delfin certainly did not. With a 1284 24vdc Northstar AGM bank and a 120 amp (detuned) alternator, I was half that, and I presume that explains why I never saw the combine voltage reached for a hour or two. BTW, that bank lasted 10 years through hundreds and hundreds of cycles and was still going strong when I replaced it with LiFePO4. And, it seems the opinion that high C rates are best isn't shared by all manufacturers:

Optima: "Low and slow is best. A low amp charger (one to 12 amps) is generally the best choice for charging any lead-acid battery. It's quicker to charge at higher amperage, but it also can generate a lot of heat, which reduces the life of a battery, just like the heat of summer."

Victron views .2C as the maximum, not the minimum: "The charge current should preferably not exceed 0,2C (20A for a 100Ah battery).The temperature of a battery will increase by more than 10°C if the charge current exceeds 0,2C. Therefore temperature compensation is required if the charge current exceeds 0,2C."

Your combiner, an older 9112, and did not combine until 13.6V + 30 seconds.. Blue Sea changed this due to the exact reasons you explain. 13.0V is pretty easy to attain but the bulk rise beyond 13.0V - 13.2V is not as fast.

That said, mine is a part number 9112, which has been replaced with the ML series. The technician couldn't find the reference on mine

Blue Sea was sold and tech support has been progressively getting a bit worse. I believe I have the spec sheet for your 9112 on my hard drive, even if Blue Sea does not, and I could send it to you.. I know they likely have it, whether the the tech support guy knows how to find it is another story..

Optima Batteries were sold by Enersys to JCI. In my experience JCI has literally destroyed that product to the point I will not longer use them as starting batteries. I never did use those as a house bank anyway as the Ah to foot print ratio is horrible due to the cylindrical cells. This is why Enersys came out with the TPPL flat plate battery and sold the spiral/cylindrical format to JCI...

I used to install a lot of Optima's, for starting banks, and they could last 8-12 years or more as starting batteries. Today I am lucky to see 2-5 years out of the JCI built versions even when used as a starting batt. When Enersys had that product they recommended fast charging, just as they do today with the Odyssey TPPL batteries (.4C). Lifeline suggests .2C as the minimum recommended charge current. Where JCI got "low and slow", for the Optima AGM's, is really beyond me? Perhaps they just modified/changed/cheapened a proven product and are riding on the well earned reputation that Enersys created by actually building a quality battery...? Hard to tell.

Personally I don't really consider the Victron AGM or for that matter the Mastervolt AGM batteries, a premium product in the "deep cycle PSOC market". Neither company is actually a battery manufacture, like Trojan, Lifeline, Northstar or Enersys are, they both apply stickers to batteries made by other companies. Their charge guidance is in-line with UPS system type AGM batteries that are not purposely built for actual cycling, let alone PSOC cycling.

My own capacity testing equipment has shown me they just don't hold up like a Lifeline, Odyssey, Northstar AGM or a Sonnenschein GEL or East Penn GEL battery does under heavy cycling with PSOC use. I put them close to par with East Penn AGM's but that is not saying all that much for a deep cycling AGM battery. East Penn however does make a tremendous GEL product.

If you're charging a premium AGM at less than .2C you're really not taking advantage of the benefits they offer for fast charging. You're not going to kill them quickly, like PSOC use will, by charging slower, but charging most AGM batteries at high rates actually leads to longer life at least with the premium AGM batteries I mentioned.

That said even at .1C the time to 13.0V is not all that long but 13.6V would be a different story. Your relay does not combine until 13.6V, Blue Sea recognized this issue and changed it in later models..

 

[Delfin]

Your combiner, an older 9112 IIRC, did not combine until 13.6V. Blue Sea changed this due to the exact reasons you explain. 13.0V is pretty easy to attain but the bulk rise beyond 13.0V - 13.2V is not as fast.

Optima Batteries were sold by Enersys to JCI. In my experience JCI has literally destroyed that product to the point I will not longer use them as starting batteries. I never would use those as a house bank anyway as the Ah to foot print ratio is horrible due to the cylindrical cells. This is why Enersys came out with the TPPL flat plate battery and sold the spiral/cylindrical format toe JCI...

I used to install a lot of tOptima's, for starting banks, and they could last 8-12 years or more as starting batteries. Today I am lucky to see 2-5 years out of the JCI built versions even when just used as a starting batt. When Enersys had that product they recommended fast charging, just as they do today with the Odyssey TPPL batteries. Lifeline suggests .2C as the minimum recommended charge current. Where JCI got "low and slow", for the Optima AGM's, is beyond me? Perhaps they just modified/changed/cheapened a proven product and are riding on the well earned reputation that Enersys created by actually building a quality battery...? Hard to tell.

Personally I don't really consider the Victron AGM or for that matter the Mastervolt AGM batteries, a premium product in the "deep cycle PSOC market". Neither company is actually a battery manufacture, like Trojan, Lifeline, Northstar or Enersys are, they both apply stickers to batteries made by other companies. Their charge guidance is in-line with UPS system type AGM batteries that are not purposely built for actual cycling, let alone PSOC cycling.

My own capacity testing equipment has shown me they just don't hold up like a Lifeline, Odyssey, Northstar AGM or a Sonnenschein GEL or East Penn GEL battery does under heavy cycling with PSOC use. I put them close to par with East Penn AGM's but that is not saying all that much for a deep cycling AGM battery. East Penn however makes a tremendous GEL product.

If you're charging a premium AGM at less than .2C you're really not taking advantage of the benefits they offer for fast charging. You're not going to kill them, like PSOC use will, by charging slower, but charging most AGM batteries at high rates actually leads to longer life at least with the premium AGM batteries I mentioned.

That said even at .1C the time to 13.0V is not all that long but 13.6V would be a different story. Your relay does not combine until 13.6V, Blue Sea recognized this issue and changed it in later models..

Interesting, thank you. I guess I'm not quite sure what the problem is with higher combine voltages, like my 9112, mostly because as you noted, a starter bank doesn't get taxed much, and in my case, spinning the starter for 2 seconds off a couple of 8Ds isn't going to take much current to top off. 2 minutes, perhaps, if that? Having said that, if charge current goes to the house bank, and the combine takes place quickly, the piddling amount of current needed to recharge the starter bank isn't going to make any difference.

Back to the OPs original question - an ACR is a useful, nearly bullet proof device that prevents your two banks from discharging together to the point where you can't start the engine. So enjoy it....

 

[CMS]

Interesting, thank you. I guess I'm not quite sure what the problem is with higher combine voltages, like my 9112, mostly because as you noted, a starter bank doesn't get taxed much, and in my case, spinning the starter for 2 seconds off a couple of 8Ds isn't going to take much current to top off. 2 minutes, perhaps, if that? Having said that, if charge current goes to the house bank, and the combine takes place quickly, the piddling amount of current needed to recharge the starter bank isn't going to make any difference.

Bingo!

Back to the OPs original question - an ACR is a useful, nearly bullet proof device that prevents your two banks from discharging together to the point where you can't start the engine. So enjoy it....

Simple, accurate and correct!

 

[dhays]

Um, no. the charging source and the primary bank will necessarily be at the same voltage when connected (unless you use very skinny wire!).

Point taken.

 

[dhays]

A very large high-CAR AGM bank at 50%, being charged by a stock 80A alt it may take a few hours before voltage is high enough for combining.

I think perhaps this issue above may explain some of the confusion here, even though it is not really anything to do with "how ACRs work".

I think this is where my own confusion came in.

 

[john61ct]

Wow thanks once again CMS, that has now superseded your past efforts as a canonical reference on the topic.

Here also is a great post from CMShttp://www.cruisersforum.com/forums/showthread.php?p=2342015

And I'm happy it was you that created that great term, can't see how it's not PC myself.

Can you please post a link to where we can find out about these classes you teach?

 

[john61ct]

I think this is where my own confusion came in.

But it would really need to be a cr^ppy alt and a very large / depleted bank, likely on its last legs wrt SoH.

 

[john61ct]

Thank you as always for great info, posts and a great refetence site..

....but.....what I got at the time was not what I wanted so I use an on/ off switch instead as you suggest...not as some aware of as a good compromise.

Unfortunately when I bought it...there was no indication this would be an issue.

Now as tech comes out, I do a lot more research first.

Anyone want to buy a small, earlier model ACR, lightly used...

If it's CL-Series BatteryLink #7600 yes.

Limits the current to 60A, very handy for certain use cases.

 

[john61ct]

While robust charge rates like .4+C are ideal for longevity with quality deep cycling AGMs,

note that the manufacturers themselves were not fully convinced of this for many many years.

And with lower quality makes, they may be afraid of liability issues with things getting hot. With say a 1000AH bank, few boats are ready to setup any charge sources at 400+A actual output capacity anyway.

Top-notch charge sources will have dedicated temp sensing wires direct to the bank, so I assume use them to guard against overheating as well as temp compensation adjustment of voltage.

Obviously solar-only setups are never getting to even .2C in a mobile context, but the loss of lifetime cycles from that won't come close to the harm done by regular PSOC abuse or over depletion, both of which are very common issues on many boats.

 

[dhays]

But it would really need to be a cr^ppy alt and a very large / depleted bank, likely on its last legs wrt SoH.

Yeah, I haven't had that situation so never even considered it. Any time that I have actually put a multi-meter on a battery terminal while it is getting a charge current, the voltage has always been up in the 13.x range.

 

[Dave_E]

WOW... 6 pages of electrical engineering! Thank you to all participants! After all the reading, I'm convinced that one of the PO's installed the ACR because the monster charger/inverter is for 1 battery charging only and he did the 1O2Both selector switch in some order that left his starter battery dead. The PO told me tales of having a dead battery and having technicians out twice to diagnose problems. I think one of them installed a basic ACR. Everything works... I treat the battery switch like I did on the sailboat... always OFF or always BOTH. We don't anchor out yet... still doing the yellow chord thing to mother dock.

Lots of knowledge... thank you all so much!

Dave

 

[dhays]

WOW... 6 pages of electrical engineering! Thank you to all participants! After all the reading, I'm convinced that one of the PO's installed the ACR because the monster charger/inverter is for 1 battery charging only and he did the 1O2Both selector switch in some order that left his starter battery dead. The PO told me tales of having a dead battery and having technicians out twice to diagnose problems. I think one of them installed a basic ACR. Everything works... I treat the battery switch like I did on the sailboat... always OFF or always BOTH. We don't anchor out yet... still doing the yellow chord thing to mother dock.



Lots of knowledge... thank you all so much!



Dave

Dave,

The folks here at TF are nothing if not experts at beating a dead horse. Some of them, as you have seen in this thread, really know their stuff. Of course we will also tend to argue minutia that isn’t necessarily meaningful for many.

I may have missed it, but it would be a good idea to determine exactly how your 1/2/B/O switch is wired. In my mind, it should NOT select which battery is being charged (as your sailboat likely was setup as was mine before I changed it).

It sound like your battery charger is connected to your house bank (which is good). The ACR then charges the start battery by combining the two (which is also good). I would suggest that you double check to see which batteries are connected to 1 and 2. Also double check to see where your alternator output is going. On my sailboat, it was connected to the Common stud on the 1/2/B/O switch (which was bad). Hopefully, your alternator output is going to your house bank, but check to make sure so you know exactly what your switch is doing.

 

[Dave_E]

Dave,

The folks here at TF are nothing if not experts at beating a dead horse. Some of them, as you have seen in this thread, really know their stuff. Of course we will also tend to argue minutia that isn’t necessarily meaningful for many.

I may have missed it, but it would be a good idea to determine exactly how your 1/2/B/O switch is wired. In my mind, it should NOT select which battery is being charged (as your sailboat likely was setup as was mine before I changed it).

It sound like your battery charger is connected to your house bank (which is good). The ACR then charges the start battery by combining the two (which is also good). I would suggest that you double check to see which batteries are connected to 1 and 2. Also double check to see where your alternator output is going. On my sailboat, it was connected to the Common stud on the 1/2/B/O switch (which was bad). Hopefully, your alternator output is going to your house bank, but check to make sure so you know exactly what your switch is doing.

EXACTLY how I'm set up. The charger goes to the house bank... the 2nd alternator goes to the house bank and the ACR jumps over to the big 8D AT THE BATTERY SWITCH.

 

[Delfin]

@CMS, thanks I found the spec sheet for my 9112. Perhaps I'll send a copy to Blue Sea! Also thanks for the education on LiFePO4 batteries. Very important for me to gain an understanding on managing this great technology, so I am grateful to you. You've been more open with your information than anyone could expect, and given a great deal back to the boating community.

 

[FlyWright]

Dave,

The folks here at TF are nothing if not experts at beating a dead horse. Some of them, as you have seen in this thread, really know their stuff. Of course we will also tend to argue minutia that isn’t necessarily meaningful for many.

I may have missed it, but it would be a good idea to determine exactly how your 1/2/B/O switch is wired. In my mind, it should NOT select which battery is being charged (as your sailboat likely was setup as was mine before I changed it).

It sound like your battery charger is connected to your house bank (which is good). The ACR then charges the start battery by combining the two (which is also good). I would suggest that you double check to see which batteries are connected to 1 and 2. Also double check to see where your alternator output is going. On my sailboat, it was connected to the Common stud on the 1/2/B/O switch (which was bad). Hopefully, your alternator output is going to your house bank, but check to make sure so you know exactly what your switch is doing.

That's a key point that is overlooked on many boats, IMO. There is the charge side of the electrical circuit and the load side of the circuit. When I bought my boat, the single Perko switch controlled both charge and load through a network of undersized and dual-purpose wires and cables...plus the panel ammeters. If you turned a switch off during an engine run, you'd fry an alternator diode.

I no longer have a manual switch controlling my charge circuit. My charge is controlled by the combiner and the combiner toggle switch at my helm. My Perko switches only control the load.

My alternators are now hardwired directly to my batteries with appropriate fusing and large cables and the SOC meter replaces the ammeters. Both sides of the circuit are appropriately sized and separately controlled. With my old-school Perkins diesels, if I need an alternator off-line, I can turn the key off and the alternator is defeated while the engine purrs along.

Coming from aviation, we always dealt with the two sides of the electrical circuit individually.....supply and demand. I seldom see that differentiation highlighted among boaters.

 

[dhays]

That is exactly where I was going with that FlyWright.

 

[Insequent]

I have now checked my physical wiring, and it matches the electrical schematics: all charge sources to House bank.

On ACR chatter and cycling. I have never had chatter. I have only noticed cycling when discharging, and only in the last year, and its just a few times. So what changed a year ago? I upgraded my solar. I surmise that when at anchor the solar can get the House up to the ACR combine voltage. But, when solar amperage is modest (clouds, late in the day) the House can draw down to the ACR isolate point. If it was just clouds reducing the solar for a short period then when the sun comes out again the House may get up to combine voltage again. Next time I'm anchored I'll leave the ACR's on Auto, an pay attention if/when they cycle.

 

[Nidza]

Well I do have a question about one case that I have with ACR. It is about transients.

I am using ACR from Victron energy type Cyrix-i (100A countinous current max) on my boat (Cyrix measures voltages on both battery groups - house and start). I am using it only for charging between batteries, and I can override it with switch/selector if emergency starting of engine is needed (this allows me to use smallest/cheapest Cyrix and to keep charging of both groups in case Cyrix dies for whatever reason and until I change it for a new one). All charging currents and battery group sizes are such that this size of Cyrix is "strong" enough. But, in two years using it flawlessly, I had two occasions burning the 100A (ANL) fuse dedicated for the Cyrix. After analyzing those two rare occasions, the problem is from transients during starting the engine if at the same time AC charger was connected to shore thus keeping the Cyrix closed due to voltage levels on house battery group or if I was restarting the engine while sailing (not connected to shore), but the period between shutdown and restart of engine was not long enough that Cyrix open its contacts due to battery levels and timing profile set in Cyrix. Of course, this does not happen all the time, but only when starting current is extremely high, and that depends of many factors as you know (ambient temperature, at what angle is the engine shaft before starting, etc.) and that is why it has happened only twice for two years. I also do plan to add solar panels and MPPT charger to house battery group side which will make this scenario almost default.

So, I know that only complete and the priciest solution is to change ACR for the bigger one (230A countinous current), but that also means different mounting and more space in already tight distribution locker which I have chosen and in which is everything installed and IP protected. And the main idea was also to use the cheapest ACR of high quality which I can easily buy and keep in spare. Next bigger one has the double price.

So what do you think of solution, which came to me, to use the PTC resettable fuse instead of ANL fuse? In that case, I only have to make adapter to mount the PTC fuse in place of ANL fuse. So, even if I get in that situation when cranking the engine, PTC will protect it and reset automatically, so I do not have to change the ANL fuse and the ACR is also protected.

Here is the PTC fuse I have in mind:
BD540 Series - Bladed Devices from Resettable PTCs - Littelfuse

Or do you have some better advice and what do you think of this soultion?

 

[john61ct]

Victron usually makes decent products. Apparently the Cyrix line is an exception.
The Start Isolation feature of the better Blue Seas ACRs will I believe handle your issue

https://www.bluesea.com/products/7620/ML-ACR_Automatic_Charging_Relay_-_12V_DC_500A

but 90% of even pro sparkies don't follow instructions on wiring the feature up properly, so oversight and testing is called for there.

I dunno from PTC resettable fuse.

 

[Nidza]

Victron usually makes decent products. Apparently the Cyrix line is an exception.
The Start Isolation feature of the better Blue Seas ACRs will I believe handle your issue

https://www.bluesea.com/products/7620/ML-ACR_Automatic_Charging_Relay_-_12V_DC_500A

but 90% of even pro sparkies don't follow instructions on wiring the feature up properly, so oversight and testing is called for there.

I dunno from PTC resettable fuse.

Well, I would not judge the Cyrix, it is being protected by the fuse as Victron predicted it and it has survived the transient before the fuse has burned, it was rather my choice to use lower current model and not to account the starter current, obviously I have overseen these transients during the design phase. So I am looking for different alternatives if possible. The one you mentioned in the link is 500A ACR, it is too big, I still can find smaller Cyrix for 230A, which is still too big since everything is in cabinet that I have optimised/chosen for the smallest Cyrix, surrounding fuses and selectors. That is why I do investigate the PTC possibility, works almost the same as fuse, but instead of breaking mechanically it increases its resistance, but after the transient is finished and PTC cooled down, it again decreases its resistance and works again as fuse (like self resetting fuse). If someone can see the bad side of it, I would like to hear it, maybe I am overseeing something again.

 

[diver dave]

Here is the PTC fuse I have in mind:
BD540 Series - Bladed Devices from Resettable PTCs - Littelfuse

Or do you have some better advice and what do you think of this soultion?

I"ve done some designs using PTC's for fuses. That 100A PTC will have a voltage drop of 0.2 to 0.4V at full current, rather high.
These are best used with systems where the overcurrent protection is difficult to reach, and it is easy to "unplug" or rewire the problem. Also, to reset, the load must be removed and a cool down period is involved.
I don't recommend a wholesale change out to PTC's in 12V boats. They are best INSIDE electronic equipment to protect agains reverse polarity wiring, as an example.

 

[boathealer]

That is why I do investigate the PTC possibility, works almost the same as fuse, but instead of breaking mechanically it increases its resistance, but after the transient is finished and PTC cooled down, it again decreases its resistance and works again as fuse (like self resetting fuse). If someone can see the bad side of it, I would like to hear it, maybe I am overseeing something again.

A few things I would want to check on if it were me:

1. Cycles - I see some of these have cycle times as low as 350. If it trips every time you start your engine, that seems pretty low. Not listed in the data sheet.
2. Most of the resistance and trip specs are listed at 25°C. I would want to know how these change at engine room temps much higher than that.
3. Time to trip shows 13 seconds at 120A and 25°C - is this OK? What happens at 40°C?
4. Hold current listed as 21A - is this OK?
5. Power dissipation once tripped is only 6.2W (I^2*R) - is this OK?

Just some thoughts - it may be fine.

 

[john61ct]

Just saying if you do replace the current unit, switch to Blue Sea, don't get a bigger Cyrix.

-----
Watch out for fuses with excessive delays, in a dead short scenario sparks flying, quicker the better.

I myself would focus on fixing the underlying issue instead.

-----
"Too big"? Makes no sense to me. Costly maybe, but there's no downside to high ampacity

except where you specifically want to limit charging current, e.g. to keep wire sizes reasonable.

Plus, never have to replace that ACR, even if you put in HO alts, high-CAR chemistry banks etc.

And self-jumpstarting built in, for even big engines.

 

[diver dave]

So, if the house is sometimes paralled with the start battery during start, a 100A fuse should not be in that part of the circuit. You want the fuse to be in series with the house loads, near the battery. Another cable should go to the combiner.
You might consider the house to combiner over current protection of a manual reset 100A circuit breaker, if you feel the need to protect the combiner.

 

[CMS]

Well I do have a question about one case that I have with ACR. It is about transients.

ACR is the Blue Sea trade name for their combiners or VSR's voltage sensing relays.

I am using an ACR from Victron energy type Cyrix-i (100A countinous current max) on my boat (Cyrix measures voltages on both battery groups - house and start). I am using it only for charging between batteries, and I can override it with switch/selector if emergency starting of engine is needed (this allows me to use smallest/cheapest Cyrix and to keep charging of both groups in case Cyrix dies for whatever reason and until I change it for a new one). All charging currents and battery group sizes are such that this size of Cyrix is "strong" enough. But, in two years using it flawlessly, I had two occasions burning the 100A (ANL) fuse dedicated for the Cyrix. After analyzing those two rare occasions, the problem is from transients during starting the engine if at the same time AC charger was connected to shore thus keeping the Cyrix closed due to voltage levels on house battery group or if I was restarting the engine while sailing (not connected to shore), but the period between shutdown and restart of engine was not long enough that Cyrix open its contacts due to battery levels and timing profile set in Cyrix. Of course, this does not happen all the time, but only when starting current is extremely high, and that depends of many factors as you know (ambient temperature, at what angle is the engine shaft before starting, etc.) and that is why it has happened only twice for two years. I also do plan to add solar panels and MPPT charger to house battery group side which will make this scenario almost default.

What you need is the right product for the job and the Cyrix-i is not it. This is not due to its amperage carrying capability but rather it's lack of features.

A Blue Sea 7610SI is rated at 120A continuous (210A for 5 minutes) but if wired PROPERLY, & most of them are not, the relay is physically opened during cranking. This feature is called SI or "start isolation". A feed from your ignition switch opens the relay, during cranking, thus avoiding passing 300A-600A+ across a 120A continuous rated relay. It also minimizes related voltage transients that can occur cranking, especially in poorly wired systems.

The Blue Sea ACR is simply a better choice and is very, very robustly built. I know Wayne K. & Blue Sea spent considerable time working to improve relay contact life to the point that they just don't seem to fail even when wired incorrectly. The 7610SI & the ML-ACR also use very heavy duty 3/8" studs rather than dinky little .25" / M6 studs. The 7610SI is also fully submersible, for as long as 30 minutes, without damage. The Start Isolation (SI) feature of the Blue Sea ACR is really a necessity, especially if your boat has alternative energy etc..

So, I know that only complete and the priciest solution is to change [strike]ACR[/strike] Cyrix for the bigger one (230A countinous current), but that also means different mounting and more space in already tight distribution locker which I have chosen and in which is everything installed and IP protected. And the main idea was also to use the cheapest ACR of high quality which I can easily buy and keep in spare. Next bigger one has the double price.

This will not solve your problem. Even a 230A Cyrix should not be closed during cranking. The minimum fuse size you'd want for cranking a small diesel should be somewhere around 250A, at a minimum. Just last nighty I noted my 583CC Ski-Doo two-stroke / 2 Cylinder engine needing 277A to get the starter turning. Once I replace the bad battery cables, and minimize voltage drop, I fully expect even this tiny little engine will be pulling well over 300A to get the starter turning. In last weeks cold snap, -19F up at camp, the machine did not want to crank very well, even with a brand new AGM. The cranking conductors were dropping 2.2V on top of the normal cold weather battery voltage sag. No wonder it did not want to crank. Snowmobiles suffer similar issues that boats do, in relation to corrosion.

Victron also fails to point out that there needs to be two fuses, not just one, protecting the paralleling wires, one within 7" of each battery bank, unless, you're meeting/exceeding the ABYC exceptions to the 7" rule..

Perhaps Victron wants that 100A fuse to protect the device and hence why they show 100A fuse at the device end (wrong location).

Blue Sea does not mandate fuse size for the relay and the fuse is simply sized to protect the wire. Sometimes I will even bump a 7610SI ACR wire GA to 1/0 or 2/0+, complete over-kill for the ACR, in order to utilize the fuses already existing at the battery banks rather than adding more fuses. The short larger gauge wire run is considerably less costly than doing a smaller gauge run and having to add two additional fuses.

With the Cyrix the wire GA you can physically place on an M6 stud is also limited so cranking current should not pass through it nor should it pass through a Blue Sea 7610SI ACR, and why Blue Sea adds the SI circuit.

So what do you think of solution, which came to me, to use the PTC resettable fuse instead of ANL fuse? In that case, I only have to make adapter to mount the PTC fuse in place of ANL fuse. So, even if I get in that situation when cranking the engine, PTC will protect it and reset automatically, so I do not have to change the ANL fuse and the ACR is also protected.

Here is the PTC fuse I have in mind:
BD540 Series - Bladed Devices from Resettable PTCs - Littelfuse

#1 Auto-resetting fuses or circuit breakers are disallowed under the ABYC safety standards so they don't reset into a dead short or reset while a tech or owner is physically trying to figure out what went wrong, when the AC or DC circuit resets and kills them (AC) or creates an additional short (DC)..

#2 Fuses connected directly to a battery bank should meet the AIC (amperage interrupt current) requirements for the bank size. Generally speaking Class-T (20,000A), MRBF (10,000A) & quality ignition protected ANL's (600A) are the best choices for this. With a properly installed combiner, one with Start Isolation, this will never be a problem. A pair of manually resetting surface mount breakers would be a better choice but most don't meet the AIC so would need a fuse that does closer to the battery.

Do you have some better advice?

Spend the $70.00 - $80.00 on a Blue Seas 7610SI ACR, and wire in the SI circuit, and your problem is solved.

Not all combiners/VSR's are created equal. Victron has some decent products but I am not a fan of the Cyrix-i for the reasons mentioned above.