Anyone use an ACR?

[Nidza]

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.

What is the current which you call "full" - tripping(40A), holding(21A), maximum(100A)? Actually, high currents are present only during short periods. My alternator is 50A, but we all know how short that current will be present, if ever (if batteries are flat). My AC charger/inverter is also Victron multiplus compact and although it is capable of delivering 70A for charging I have configured it to give charge with maximum of 20A since my house battery is AGM 130Ah and start battery is flooded 148Ah (actually 74Ah x2 in parallel to save my back), so when paralleled around 10A to each bank (if we say everything is ideal, which is not, but that is the life). I do expect that most currents at steady states are much, much below holding current of 21A.

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.

I designed that all of my "electrics" (for which is possible) and batteries are out of engine room and in very good ventilated space, so temperatures are not critical, although I did pay that with thicker cables.

Tripping times of PTC are similar to thermal fuse, just the current values are a bit different. And this is the strongest PTC I could fine.

According to my steady states, 21A should be OK, and transients I want to dampen with PTC anyway.

Dissipation is not critical. Even the ANL fuse, although being ignition protected is in IP enclosed cabinet so it cannot start a fire.

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

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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.

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"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.

It is spark protected as I have already explained, fuse part enclosed and fuse enclosed in IP protected cabinet.
ACRs are relays, so eventually, they have to be replaced, contacts die sooner or later, therefore price is important. Ampacity is good, but it also does cost. My engine is already having very big starter, it is an old V8 from Cummins. My cables for starter have 85mm2 cross area. If jump starting needed, I like the idea that I can also disconnect start group of batteries with selector in case it is completely dead (well, I hope I will never experince that, but there is some Murphy guy always listening). If jump needed, than again I prefer manual selector.

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.

I copy/pasted that part of schematic with the fuse from Cyrix datasheet, here is the link:

https://www.victronenergy.com/upload/documents/Manual-Cyrix-i-400-EN-NL-FR-DE-ES.pdf

Other fuses are out of the scope of the problem, so I have not been describing them (from batteries to loads, etc), this is the only one in line with the combiner.

Using manual reset DC circuit breaker is also excellent idea and easier to find. But, when solar charger comes in the circuit, I question myself how often will I have to do that, if often, I prefer PTC, otherwise manual. Both adapters would be wise to build. Tanks for the advice.

Thanks everybody for the brainstorming!!

 

[JDCAVE]

Nidza: I would study CMS’s post on your problem closely as I believe he has considerable background on this subject.

 

[john61ct]

I don't think "ACR" is trademarked, but yes VSR and combiner are the more generic terms, especially VSR in commonwealth English.

ACRs are relays, so eventually, they have to be replaced, contacts die sooner or later, therefore price is important.

I've never heard of that Blue Sea ML unit I linked to failing, they have a **very** strong rep for being bulletproof, as opposed to Cyrix

And given its non-essential role, certainly not something I'd feel the need to carry a spare for anyway.

 

[Nidza]

@CMS,
it seems that I was editing the text while you were answering so did not see it at correct time, and my message turned out after yours which is not logical order.

I do apologize for using protected acronym ACR, I did not checked it since there are many acronyms which mostly state "...smart relay..." in some form, missed it.

OK, I do agree with you on most aspects. Good price for 7610SI, I do like that one and it does cover my case (maybe not by dimensions only). It actually has completely opposite function from Cyrix, the Cyrix has a contact pin to connect it for 30 seconds if needed (which I have left open), instead of using selectors, and it can stand higher amounts of current for some time, long enough for starter motor to decrease the current in normal conditions, conditions in really low temps that you are describing are special cases, at least in my country. Of course, if that is going to be used, proper Cyrix has to be used, with adequate ampacity (they also cover higher amperage than continuous rating during shorter period like cranking), and newer ones Cyrix-t have internal temperature protection, but all that is not what I want in my case anyway. In my case, concerning 7610SI, only the protection is overkill since I am installing it in the IP protected cabinet not even close to any flammable surrounding, but only in a sense that protection is making it bigger.

And there is always the problem of availability in my country so that does effect my choices a lot when buying for me privately (hopefully this will change in time). You seem a bit toward the brand, I am indifferent to brands, just looking for the correct function, properties and price and in this case you nailed it.

As an electric engineer, I do agree with you that fuses protect wires (preventing fires), not devices and that they have probably wanted to save device with that inline fuse. Anyway, those are more like marketing diagrams around sole device than the system, we all know how "real" schematics looks like and what sort of details are "imprinted" in them. Also I do agree with you about protection standards in any aspects preventing dangerous or lethal situations, although when building for yourself some aspects not concerning dangerous aspects can be little more "flexible" (not talking of here mentioned cases).

About stated ABYC rules - #1 - AC is obvious, for DC I agree mostly, but there are some cases where I could disagree, but I will not because at some moment any boat can be and most often is sold to someone who is not technically inclined with electricity/electronics, and it has to be 100% safe in such case, too. #2 - I do have ANLs for each bank with proper AIC so it would be valid to use manually resettable circuit breaker and I do like that idea, at least while I do not redesign the circuit. And yes, that will be also in IP protected cabinet as is the current fuse.

Thank you for going through all aspects in details! Good info and good solution/advice!

 

[CMS]

You seem a bit toward the brand, I am indifferent to brands, just looking for the correct function, properties and price and in this case you nailed it.

I am not pro or against any brand, heck I even still use some Xantrex products despite overall poor reliability on some of their products. I do always try to pick and choose products based on the specific product itself, features/benefits, its reliability, cost and total installed cost.

There are a lot of Victron products I like and install that I believe are better than those from other brands, and then some other products from other manufacturers I like, but perhaps not the entire line up. In the case of the Blue Sea ACR's I have found them amazingly reliable, robust and well designed. I also use Yandina Combiners and they have a lifetime warranty. I am just not a big fan of the Cyrix when compared to the ACR that is within a few dollars of it. Each company has their winner products and their second or third string products. It is actually quite rare that one company does every piece of gear "the best"...