wiring question for 4 golf cart battery bank

[iggi]

I've been searching for an answer but not having any luck so my apology if this has been asked before.

Looking at running 4 golf cart batteries for a big 12 volt bank.
So.. 2 sets of 2 wired in series and then wired in parallel so that I end up with 12 volt bank with roughly 400 amp hours of capacity.

Question:

Does the distance between the two - 2 battery packs matter?

It's a bit tricky to put all 4 together in my rig and would be a lot easier to put them in two separate battery boxes and then parallel together. Would be about 20 inches between them.
Seems like that should be ok, but given how many other electrical things I've been wrong about this past month some feedback from the smarter folks would be appreciated.

Thanks!
Ian

 

[dreadlocks]

<2ft would be perfectly fine, you wanna oversize all the battery connections anyhow, so even at high amps the voltage difference is negligible.. a bank of golf cart batteries in a golf cart exceeds 20in from one end to the other.

but yeah it does matter, as in if you have to load one bank at the front of a vehicle and one at the rear of the vehicle you'll likely want to just split it into two seperate banks at that point and switch between em.. just because you wont be able to get the proper size cable to easily route between em, and it would be alot of weight and money spent on the copper connecting it.. your batteries don't need to get that far apart before its just better to seperate the banks for convenience and redundancy.

What are your big loads? If you have any multi-hundred amp loads you are trying to run.. may be advantageous to consider a 24v bank to cut the amps and wiring needs in half.. for example a 3000W inverter is 250A @ 12v and 125A @ 24v..

 

[iggi]

Thanks @dreadlocks I definitely owe you a few beers if we ever cross paths.

Biggest load will be the induction cooktop and occasional use of power tools.
Mostly loading up on capacity for winter camping and working remotely.
Essentially trying for a couple days of full time furnace, fridge, lights, computer without solar or any long drives to charge the batteries.

Given that everything is already setup for 12volt it seems changing to a 24volt pack would require a fair bit of work and replacement of my Xantrex inverter.
Or have I missed something again? lol

 

[dreadlocks]

If your xantrex inverter is not capable of just switching to 24v internally, then yeah might as well run it 12vdc.. but if you ever need to replace that inverter, consider a 24v one.. converting it to 24v later would be rather simple, just connecting things a bit differently.. but it is usually a design consideration to take before all the rest of the electrical is in place.

Dropping from 24v down to 12v for legacy appliances is pretty easy and efficient.. you can get a 20-40A 24v to 12v voltage regulator for pretty cheap.. wire that up between the bank and legacy circuits.. now charging might be a bit tricky from engine.. I havent looked into doing this on a vehicle w/alternator, guess you put a 24v alternator in it.. but you got two of em right? mebe one 12v for auto and a 24v one for house.. shrug.

 

[Joe917]

Avoid splitting the house bank in two.

 

[luthj]

See below. Treat each 12v group as a single battery, the interconnects between the 6V units should be the same length (for each 12v group). Most importantly, there should be the same number of terminals/connections, as they add significant resistance. No washers under lugs at the terminals, and make sure you have good contact.

SmartGauge Electronics - Interconnecting multiple batteries to form one larger bank

 

[iggi]

Thanks @luthj !

I'd seen that link but couldn't remember where or find it in a search.
You probably shared it before.

Cheers,
Ian

See below. Treat each 12v group as a single battery, the interconnects between the 6V units should be the same length (for each 12v group). Most importantly, there should be the same number of terminals/connections, as they add significant resistance. No washers under lugs at the terminals, and make sure you have good contact.

SmartGauge Electronics - Interconnecting multiple batteries to form one larger bank

 

[Photobug]

See below. Treat each 12v group as a single battery, the interconnects between the 6V units should be the same length (for each 12v group).

Makes sense about the interconnects. Same could be said for the two battery groups. I would also make sense if the two battery groups were a different distance from the panel as long as the cable lengths were equal the resistance on the cables would be equal.

Why no washer at the lugs? Does that mean no felt washer also?

 

[luthj]

There are best practices for bolt on terminals. Generally this means no washers between stacked lugs, and none between the battery and the first lug. The felt anti-corrosion washers are fine, as long as they are not clamped between conductors.