New 24v bank feeding 12v windlass and 12v engine start?

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jointcustody

jointcustody

Veteran Member
Joined
Oct 16, 2020
Messages
44
Location
Canada
Vessel Name
Joint Custody
Vessel Make
CHB 34
Hi there,

If i have to draw diagrams I am ready to do that...I am going to do my best to get this all across lol.

I currently have a 34ft CHB trawler with a perkins 135 diesel. It's the boat in my sig. I have a 12v house bank that is 2 sets of 2-6v gc batteries, new 10 months ago. So 4 batteries wired to a 3 position switch that is always left on "both" so for simplicity lets just say i have a 416ah 12v house bank. I have barely cycled these house batteries. Maybe 30 cycles.

I have a 12v windlass in the bow. There is old 4/0 wiring ran from my house bank to the windlass. 25-30ft including bends.

I have a separate 12v 4d battery for starting the perkins.

--------------------------------------

I am adding a sideshift ss350 24v bow thruster. It is already purchased. I need to add 2-12v AGM's in the bow to feed it 24v. I also want to feed my windlass with one of the batteries- so connect to just one of them. I don't really want to rewire my windlass motor to 24v (assuming thats possible- its old) because I have a spare windlass motor. I have read that you can use a battery equalizer to balance them and they should be fine. For charging, I think victron offers a 12-24v dc-dc charger that I could run from my 12v alternator to the 24v bank to charge. Heres where it gets trickier...

My 4d starting battery is getting older... like 8-9 years old. I want to use this opportunity to remove it, and potentially rewire. I'd like to add two more gc batteries to increase my house bank to 624 ah (using the battery box that my starting battery had)

Assuming everything is ok up until this point, should I use the 4/0 cable from my bow, shorten it up and renew the ends... run it from the OTHER 12v battery in the bow, (the other side of the 24v setup) as my engine starting battery (and maybe go large on these batteries?)

Is it a bad idea to remove the engine start battery?

Or should I start this engine with my new larger house bank? (surely theres enough cranking amps now???) with an emergency parallel switch to one of the agm's in the bow should the house bank go dead- maybe two switches- one to shut off the depleted house bank, the other to turn on the emergency start from the AGM to the perkins- then you could close the house bank back in and begin charging it (but could destroy my 12-24 charger in the process?)

I have read that my perkins should have two 750 cca 12v batteries in parallel for a dedicated starting battery, but that it will start just fine with one. It is only with sustained cranking that you need to have two. I will be installing two 850cca AGM's in the bow for the thruster. So in a situation where someone goofed up and the house bank was completely flat, the single 12v agm would start it fine.

I should also say, that I have a diesel genset that I could start as well to run the battery chargers in such a situation.

To me- it seems like I got enough 12v batteries around that surely I dont need to have a dedicated one for starting at this point????

I am a powerline technician (lineman) by trade so I understand the basics, but I deal with AC at work.

Sorry, Thanks lol :banghead:
 
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Yes, leave the 4/0 cable to the windlass and use a 12 volt to 24 volt DC charger to recharge the bow thruster batteries.

If you want to start the engine off the house bank, it can certainly be done. Recharging the house bank from the generator through the inverter / battery charger will work if the house bank is to low to start the engine. But, when I want / have to move the boat NOW, I don't want to find the battery is too low to crank it over.

An alternative would be to use a single battery to start the main engine and add a paralleling circuit with a switch to temporarily parallel the start battery to the house bank. When the battery gets weak, you are essentially jumping the start battery off the house bank by closing the switch (until you replace the start battery). The above is what I did on my single engine boat.

Ted
 
Regarding starting from the house bank. Of course there are reasons not to rely on the house bank for starting with no other way to start the main. However here is one well considered argument on using the house bank for starting by Rod Collins at Marine How To 1/2/BOTH battery switch considerations. You'll have to get nearly 1/2 way through the article to get to the point where he discusses starting from the house bank. His discussion considers a much smaller diesel than yours so the math will need to be adjusted. He does in the article talk about a 'reserve' battery.

That makes me ask the question can the generator start battery be the reserve battery? Your engine requires 750 CCA. It's easy to find a group 31 that is higher CCA than that. Why can't the gen start batt be swapped out for a group 31 and have that serve as the reserve battery?
 
O C Diver said:
Yes, leave the 4/0 cable to the windlass and use a 12 volt to 24 volt DC charger to recharge the bow thruster batteries.
Ted
Click to expand...

So don't use the agm in the bow to power the windlass?
 
Portage_Bay said:
Regarding starting from the house bank. Of course there are reasons not to rely on the house bank for starting with no other way to start the main. However here is one well considered argument on using the house bank for starting by Rod Collins at Marine How To 1/2/BOTH battery switch considerations. You'll have to get nearly 1/2 way through the article to get to the point where he discusses starting from the house bank. His discussion considers a much smaller diesel than yours so the math will need to be adjusted. He does in the article talk about a 'reserve' battery.

That makes me ask the question can the generator start battery be the reserve battery? Your engine requires 750 CCA. It's easy to find a group 31 that is higher CCA than that. Why can't the gen start batt be swapped out for a group 31 and have that serve as the reserve battery?
Click to expand...

Your link was very helpful- I will follow up with a modified diagram i made from the link you sent me.

As far as the generator start battery, I am pretty sure its fed from the 4d I am trying to remove. I could probably start it with one of the agm's in the bow though...
 
I have attached a photo with the planned wiring diagram. Ted, it would be easier to just leave the windlass the way it is... but I am hoping to get an emergency engine start out of one of the agm's... unless you think being able to fire up the genset, and thus charge the batteries in an emergency is good enough. Whats the chances of batteries being dead AND having to move the boat suddenly happening at the same time?

See attached. Thanks a lot
 

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Take a look through this thread
https://www.trawlerforum.com/forums/showthread.php?t=61233
I believe your 6V bank qualifies as a large batty bank and ABYC requires fusing that can handle dead short current a large bank can deliver. In your case that is likely a type T fuse. More info & links in that thread.
I'm no expert here but trying to learn what I need to do when replacing some 8Ds. This may be one case where a large combined house/ start bank is a negative... start usually does not require fusing but a large batty bank requires dead short protection? You may need to consult with a knowledgeable source re the large bank protection.

I'm also confused how you plan to use the 12V of your 24V bank for main eng & gen start... you show no neg connection for that 12V batty (I'm assuming 12V for gen & eng start - maybe incorrectly? But the primary starts are from largev12V bank?)
 
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Ok, let me add some more thoughts:

If you remove the engine battery or isolate it with a switch or put a fuse between the alternator and the house bank, you run a substantial risk of a voltage surge to an electronic item should the switch fail or be in the wrong position. Also, the fuse failing could cause that spike. Bacchus is correct that the house bank should be fused. The problem is that a fuse large enough to handle engine cranking draw (momentary) would be incorrect to protect the DC wiring. You would likely have to come off the bank with a battery cable to the engine, and one (through a fuse and the battery switch) to the breaker panel. It would be helpful to know the distance from the house battery to the engine.

Are you, or do you plan to use an external multi stage regulator (such as a Balmar) on your alternator? The voltage sensing location would be critical in this application.

It's generally considered an extremely poor idea to run substantial loads (the windlass) off one 12 volt battery in a 24 volt system. This has to do with charging where one battery is low and the other is full. My recommendation is still to run the windlass off the existing 4/0 cable from the house / engine battery and install the 12 volt to 24 volt battery charger next to the windlass batteries.

How big is the generator battery?

How many amps is the battery charger for the house bank that could be run off the generator?

Ted
 
Agree with Ted. These highly inductive loads like eng starters are stressful to electronics. In my perfect world, eng start batts are close, dont share, and have operator controlled jumper ability in emergencies.
 
O C Diver said:
It would be helpful to know the distance from the house battery to the engine.

Are you, or do you plan to use an external multi stage regulator (such as a Balmar) on your alternator? The voltage sensing location would be critical in this application.

It's generally considered an extremely poor idea to run substantial loads (the windlass) off one 12 volt battery in a 24 volt system. This has to do with charging where one battery is low and the other is full. My recommendation is still to run the windlass off the existing 4/0 cable from the house / engine battery and install the 12 volt to 24 volt battery charger next to the windlass batteries.

How big is the generator battery?

How many amps is the battery charger for the house bank that could be run off the generator?

Ted
Click to expand...

1) the distance from the one edge of the house bank (i can make that the positive end) to the engine start can be as low as 2-4 ft. of cable. (are you wondering distance just because your thinking theres no point in fusing a really short run?)

2)There is currently a "next step regulator" beside the engine and a newer heavier "hot" alternator installed, with the factory alternator as a spare. I meant to get the details off it the other day but forgot too. I checked out the regulator to the best of my ability this summer and it appeared to be working fine, but I would like to fine tune it after I heavy up the house bank.

I don't know if these regulations for fusing are the same in Canada... we are on vancouver island. To be honest I would just wire it up, but I thank you for the post.

3) after sending out my last comment there it was decided that we would just leave the 4/0 for the windlass... it does draw a lot and it would be better leaving it off the larger house bank now. also makes for a much simpler system- no battery balancer etc. Your right Ted we will leave it.

4) the generator battery was the 4d battery that I am trying to eliminate.
I think it would be perfectly fine to start the genset with one of the 12v agm batteries from the 24v bank.... that draw is so small i would think the 24v bank would balance itself. That would give me redundancy if the house bank died. (i can run my battery chargers off my genset) I have an outback inverter/ charger thats 40A. I also have a second old school heavy built marine 50A charger that i think is much lower tech...

questions:
1) I dont think the genset has an alternator itself.... i am asking this because if i start it with one of the 12v batteries off the 24v bank, I don't want it to be charging that battery by itself. I don't think it does... so should be fine.

2) Can i run the inverter/charger 40A and the old school 50A at the same time? or will they cut eachother out sort of thing.... i think i tried it already and the 50A old school seemed to cause the outback new school one to cut out.

Id really like to add some flexible solar panels onto our flybridge.... even like 300w would make a huge difference.

Thanks.
 
How big is your generator? Most smaller generators could be started with a lawn tractor battery. A 4D is excessive to say the least.

You really need to confirm whether the generator has its own alternator or not.

What is the distance from the generator to the main engine?

What would be the cable length from the generator to the bow thruster batteries?

I'm formulating a plan for you, but need to get my workout (cycling) in before the sun goes down.

Ted
 
Ted,

I literally just finished last week doing an overhaul on my entec 4200d genset. I know it doesn't have an alternator in the traditional sense- it just had a belt running the raw and coolant pumps thats it. Unless there is some other way to feed power back other than an alternator.

My distance from genset to main engine is like....id say 10 ft of cable but engines are physically 6 ft center to center of eachother.

the cable to the 4d from the genset is currently... 10-12 ft. from the genset to the bow thruster batteries I would say would be 12-14 ft.

wow, thanks for doing that.

Cheers
 
I would not use half of a 24V bank for anything. I would either find a motor shop and have my spare windlass motor rewound for 24V, then swap it in; or run it off the house bank. A 24V rewind would be the cleanest solution and you can eliminate the 4/0 cable run if you did this. Finding a shop to do so might be an issue of course, this used to be easy but not so much anymore.

I don't see any benefit to not having a start battery, but some drawbacks as others have mentioned. Using an AGM identical to one of the units you are using for your windlass up front would be plenty and can be setup to be the start battery for both the main and genset as the default start batt. You'd need to add a DC-DC charger for it as well since an AGM won't charge properly from the FLA house bank without a voltage boost. The house bank is then your 'emergency' start bank.
 
It's likely that I have it wrong but...
It seems like the goofiness started by adding a 24v thruster to a 12v boat. I googled that thruster it's 400A at 24v, it's a beast.
Is it even possible to build a 24v bank from 12v batteries and then pull 12v from one? Seems weird but someone will know if it'll work.
It seems like really what you're doing is building a 24v start battery bank then pulling 12v off for start and windlass leaving 12v for the thruster.
So far none of this seems to involve your 4 soon to be 6 GC battery house bank. So I'm unclear why some are talking about starting from your house bank or start loads effecting your electronics assuming that your electronics are connected to your house bank.
Seems to me the big question is about pulling 12v off your 24v battery bank. Figuring out if that works ok just leaves you with how to wire the system which is pretty straight forward.
Also instead of just saying run a 4/0 to your windlass or whatever how about looking at the load. As an example, on my boat my windlass came with a 100amp breaker, so that's the max amperage that the circuit will see. So look on the charts for the appropriate wire size to the the load rather than just default to the largest.
And, hey, you've a generator, have a small separate start battery for that. If you tank all the other stuff you can still start that to recharge
 
sean9c said:
It seems like the goofiness started by adding a 24v thruster to a 12v boat. I googled that thruster it's 400A at 24v, it's a beast.
Click to expand...

Better 400 amps at 12v than 800 amps at 12v. No big deal, wire it as 24v with a dedicated charger and 2 batteries and leave it alone.

IMO the goofiness started by thinking about drawing from that 24v battery bank for heavy 12v loads. Don't go there.

It sounds like the windlass is appropriately wired now to the house bank. Why change it?

I'd suggest dedicated starting batteries for the main and genset, but they don't have to be huge. Maybe group 31 for main and smaller for genset. Alternator and future solar output goes to the house bank, then maintain the charge on the main starting battery with a dc-dc charger from the house bank. I'd guess that your generator has a 12v charge output to maintain its battery, so no worries there.
 
I think that my point was that it's an awfully big thruster for a CHB 34.

Jeff F said:
Better 400 amps at 12v than 800 amps at 12v. No big deal, wire it as 24v with a dedicated charger and 2 batteries and leave it alone.

IMO the goofiness started by thinking about drawing from that 24v battery bank for heavy 12v loads. Don't go there.

It sounds like the windlass is appropriately wired now to the house bank. Why change it?

I'd suggest dedicated starting batteries for the main and genset, but they don't have to be huge. Maybe group 31 for main and smaller for genset. Alternator and future solar output goes to the house bank, then maintain the charge on the main starting battery with a dc-dc charger from the house bank. I'd guess that your generator has a 12v charge output to maintain its battery, so no worries there.
Click to expand...
 
sean9c said:
I think that my point was that it's an awfully big thruster for a CHB 34.
Click to expand...

It is the size they recommend for my boat when you call them. My boat is heavy for its size and has a ton of windage.

Thanks everyone for the other posts. The original post Is definitely dated now...

Here is the update to what we are still considering;

Replacing our dated 4d start battery that currently starts the perkins and the genset with another set of gc batteries, so a total of 6 in a series-parallel configuration making 624ah at 12v. We would then use it to start the perkins as well.

Adding a 24v agm bank in the bow (2-12's wired in series) to power my bow thruster. using one of those batteries to start my genset. This would give me redundancy to start my genset if the house bank went dead, and charge the house bank. I would run a dc-dc charger to the agm bank from my house bank with a ACR in there.

leaving the windlass the way it is, off the house batteries. (not running off the new 24v bank)

Thanks for your interest
 
Don’t they make it in a 12v version too, if I read the data sheet correctly?
 
Bowball,

They do, at 800A draw... which is fine, but its too far from my house bank to draw that from it, and the cables would be massive. So you would need two new batteries anyhow.

Also, they still recommended the 24v version, maybe it has a little more jam? IDK.

And then as a bonus (and how i got it) I found it on craigslist with a brand new motor replaced under warranty (with another years warranty transferred to me) for $2800. They are $5600 taxes in new. In literally new condition.

Thanks
 
That all makes sense. In the side power line they stop 12v models at the se130 which is 130kg of thrust.
Looking at the boat size range of recommendation of theirs (42’-62’) in comparison, the model you selected does not seem too large.
 
Sorry for not getting back to you sooner, but life got in the way.

Here's my recommendation with some explanation as to why:

I would strongly recommend a separate starting battery for the main engine. Having 2 power sources in the engine room for the main engine and generator provides redundancy which equals reliability. Whether you put the battery in the existing engine battery box or the generator battery box is a matter of easiest wiring.

The generator is small enough that it should easily start off the house bank with minimal draw.

If you utilize the empty battery box to enlarge the house bank, I would suggest wiring the alternator and smart regulator to charge the house battery instead of the engine battery. The house battery sees probably over 90% of the consumption and makes the most sense to charge directly off the alternator.

I would install a 12 volt to 12 volt battery charger between the house bank and the engine battery. This will charge the engine battery off of the house bank. The engine draws very little energy (in a big surge) when starting, and the running consumption for gauges and maybe a fuel solenoid is quite small. The battery charger probably can be between 6 and 12 amps. Alternatively, if you leave your inverter on, a 120 VAC 6 or 12 amp battery charger could be used to charge the engine bank.

I would add a circuit as previously described, to combine the house and engine batteries to overcome a low battery situation. Alternatively, a set of jumper cables could be used.

If overcoming a low battery situation, you would want to start the engine on the good battery first. So if the house bank were to low to start the generator, starting the main engine first, guarantees charging to the house bank through the alternator before trying to jump the generator off the start battery. Doing it this way insures that a problem with the generator doesn't also draw down the main engine battery.

If the main engine battery is low, starting the generator first, allows charging to the house bank through a 120 VAC battery charger to prevent the main engine from drawing down the house bank (should there be a starting problem with the main engine).

Also, wiring it this way will prevent most electronic items from seeing low voltage when starting the main engine.

Finally, all charging is automatic with isolation of the different batteries when you shut the engine down.

Ted
 
What a project!
IMHO you have your house and start banks properly configured right now.
For your windlass a 4/0 from your house bank seems about right, and the boat has probably had that setup since new, 30 to 45 years ago, so why mess with success.
I don't think messing with any of that will help your thruster installation.

Getting rid of the 4D shouldn't be a priority. Yes, you can start from your house bank, but you already have the start battery set up, though you may need to replace the battery soon, as it is aging.

Do you really need a thruster? Your boat has gotten along without one for a long time, so far, and you likely have already learned to handle it without that extra bit.
 
Ted,

Your explanation sounds very similar to the setup I have now. I think you have convinced me to leave it the way it is or at the worst take on another set of 6v gc's if i desire more house bank capacity. I do think theres value in looking into a better charging setup for each individual bank though. Thank you for making me come to this realization.

Koliver,

My wife and I split the boat with my parents, so we are not the only operators. There was a couple close calls in some heavy wind trying to dock in foreign marinas this summer, and even when you look at the hesitancy to use the boat-just that one aspect- in my mind it is worth installing the bow thruster. You spend all that money and expenses every year and then hesitate to take it out on a half decent day? forget it. Especially because I will be all-in to this system for like $3700.

I am seriously considering to add even 300 watts of flexible solar panels to the roof of my flybridge, and increase the CHARGING rather than the capacity....including making sure my regulator is dialed in from my alternator
 
Hey guys,

So I am finally gathering the parts for this project- getting two 12v agms for the bow to make 24v for my thruster (size 31 or larger). I want to charge with victrons 12-24v dc-dc charger as suggested- likely their 10 or 15a model.

Do I need to put a VSR in between the alternator and bow thruster batteries? I read that it might not even work because the vsr needs to sense voltage on both sides.

Just trying to protect the scenario where the bow thruster batteries run flat and then try to pull juice from the house bank via the connection at the alternator. I can't see any details on the victron dc-dc on if they allow current to flow "back and forth" or just the one direction. Maybe I am overthinking it? and what fusing if any to protect the wire?

Thanks.
 
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