misc dual battery winch solar electrical questions

[osidepunker]

Hello!

I am planning out my electrical system upgrades and I have a few questions for the experts. First my planned setup:

Diehard Gold AGM 34 MB (main battery)
Two Diehard Platinum Marine 34 HBs (house batteries) mounted in the bed
IBS-DBS dual battery system with Relay Booster (enables starting with a totally dead main battery). 200 amps continuous, 500 amps surge ratings
200w solar panels and charger

My loads:
12.5k winch, max draw 420 amps
ARB 82q fidge
12v RV water pump
Lots of LED bars, radios, air pump, lockers etc.
12v and 120vac ports in key locations

I am planning for max draw on the HBs, which would be prolonged winching with a dead engine. With that in mind I am going to run 2/0 welding cable, POS and NEG, from the HB bank to the MB. It should be about a 16-18' cable run. 2/0 cable should also lower resistance for better solar charging on the MB. Couple questions:

I know I should fuse the 2/0 cable run at both ends, close to each battery. How do I choose a fuse size? What type of fuse should I use?

The HB bank will be two batteries in parallel mounted next to each other. Should I put a fuse between them? If so what size/type?

I am going to use military battery terminals with copper crimp terminal ends and a hammer crimper. Does anybody think I should go a different route for connections?

I need a MB and HB fuse and relay box for all my accessories. I have looked at Blue Sea, but they seem expensive and not enough connections I think. Are there any other solutions out there?

thanks for reading!

Does anyone have any suggestions for improvement or constructive criticism with my plan?

 

[osidepunker]

Looks like I should use ANL fuses rated for the wire size. Since I will be using 2/0, I am going to use a 400 amp ANL fuse right at the HB bank.

Should I also fuse the line at the Dual Battery switch?

 

[Tony LEE]

You will get all sorts of answers, but generally it is wise to have a catastrophe fuse as close to the source of any unregulated current as possible. Problem with major loads like the winch is that is hard to discriminate between a legitimate current draw and fault current which goes to explain why a starter motor isn't usually fused. My winch isn't fused, but it is supplied from the two engine batteries and through very short cables with extra protection in the same way as the starter motor, but your route length is too long to take that risk. Have you worked out what the voltage drop at the winch will be at a current draw of say 250 amps over 30' of cable.

Solar panels - may be some UL listing that supposedly requires it, but solar panels themselves are current limited so what size fuse could you use? Between the regulator and the battery the same argument applies at the regulator end, but you do need a fuse at the battery end.

BTW, there are some smart people who consider fuses as a very inferior method of circuit protection and who prefer quality circuit breakers because they have less resistance, faster fault clearing and are less liable to develop high resistance joints over their lifetime.

Two loads you really need the engine running - winching and pumping up tyres - so prolonged winching with the engine stopped may not be as prolonged as you hope for.

 

[osidepunker]

You will get all sorts of answers, but generally it is wise to have a catastrophe fuse as close to the source of any unregulated current as possible. Problem with major loads like the winch is that is hard to discriminate between a legitimate current draw and fault current which goes to explain why a starter motor isn't usually fused. My winch isn't fused, but it is supplied from the two engine batteries and through very short cables with extra protection in the same way as the starter motor, but your route length is too long to take that risk. Have you worked out what the voltage drop at the winch will be at a current draw of say 250 amps over 30' of cable.

Solar panels - may be some UL listing that supposedly requires it, but solar panels themselves are current limited so what size fuse could you use? Between the regulator and the battery the same argument applies at the regulator end, but you do need a fuse at the battery end.

BTW, there are some smart people who consider fuses as a very inferior method of circuit protection and who prefer quality circuit breakers because they have less resistance, faster fault clearing and are less liable to develop high resistance joints over their lifetime.

Two loads you really need the engine running - winching and pumping up tyres - so prolonged winching with the engine stopped may not be as prolonged as you hope for.

Thanks for the detailed response!

Yeah I dont think I will have a whole lot of winch time with a dead engine, but three group 34 batteries should at least move me a little. My thought was if I hydrolock during a water crossing, maybe I can still finish the crossing. Or a crash kills the engine and I have to move the vehicle to save it. Unlikely scenarios like that.

The other thing that complicates matters is the winch will be connected to the MB. Then a 16' cable run to the HB bank. So at a max draw of 420 amps from the winch, I will not really be passing 420 amps through the 16' run. I guessing it will be somewhere north of 200 amps. Voltage drop across 16' of 2/0 cable at 420 amps is 1.05vdc or 8.75% of 12vdc. That would be worst case scenario though; a dead engine and a dead MB. I am just trying to plan for the worst, which will have a side effect of reducing resistance for optimal solar charging on the MB

I will look into C/Bs. I didnt think that was a recommended practice on 12vdc systems since I never see them. Do you have any you recommend?

I'll do the solar next year, but I agree it need to be fused as well.

 

[unseenone]

You can definitely reduce the winch amperage draw with copious use of snatch blocks. That would help a lot of power. With your solar, it might take time, but you might be able to recharge and winch again if the engine was dead.

Ideally with the engine running, with the other loads you mention you should be fine. Obviously if you are broken down, wrecked or otherwise disabled, you would conserve power within the limits of what you can replace.

Where will you be traveling out of curiosity.

 

[dwh]

I know I should fuse the 2/0 cable run at both ends, close to each battery. How do I choose a fuse size? What type of fuse should I use?

Size the fuse to protect the wire. Whatever the wire is rated to carry, that's the size fuse you need. Type of fuse is up to you. ANLs are good, but they are a bit of a "slo-blo" sort of fuse. But that's okay, because they won't blow on a short term overload (the wire won't melt on a short term overload either), but they'll blow almost instantly on a dead short.

The HB bank will be two batteries in parallel mounted next to each other. Should I put a fuse between them? If so what size/type?

Depends on how close they are together. Sitting right next to each other and paralleled with a foot of wire and then feeding into a fuse? You don't need to fuse each battery as well - unless there is some grounded metal real close that creates a sketchy situation for those short wires paralleling the batteries, then yea...but I doubt that's happening.

Does anyone have any suggestions for improvement or constructive criticism with my plan?

Well I think your "worst case" assumptions are not accurately defined. For instance, you say worst case is dead MB and full winch load coming from HB. But then you say that the 2/0 won't have to carry the full winch load, but only maybe 200a.

That ain't right. If the MB is dead, then the 2/0 *will* have to carry the full winch load. (IF the winch is fully loaded, of course.)

Also, you've calculated your voltage drop at 12v. Most people do. But it's wrong.

At full charge, the battery will be at 12.8v.
Under heavy load it might be (temporarily) dragged down to 10v.
450a max winch load is at what? 12v?
450a x 12v = 5400w.
5400w / 10v = 540a.
So now, redo your voltage drop calcs using the TRUE "worst case" numbers of 540a and 10v.

Which then leads us to the question: Is that 2/0 gonna be big enough if it has to carry a 540a load?