Proper Balance of wiring 3 12V batteries

Thanks BFL13. I currently have the solar controller/Inverter inside the trailer on that same Blue Sea bus bar, each fused with ANL. I also have a 250A fuse on my current T105's which I plan to reuse- either after the bus bar or get 2 more and have one on each battery.

Of course I can't get at the trailer now as it is still burried in snow.... sigh.

With thirteen positive wires all trying to be on one buss, you might need two or three sub-busses to hold all the terminals. That's what I do. I collect a few pos ring lugs and bolt them together with a short fatter wire out from that going to another fatter wire that comes from another collection of smaller wires. Those two go on the buss that the battery links all go to.

Fusing starts with a big amper on the first fat wire to a branch buss, then each thinner wire from that has its own smaller amp fuse.

The pos wires from each battery to the buss point could be unprotected and everything (except the breakaway brake wire) from there would be fused, each in its own way, depending on its wire size and current load. Or you could fuse each battery link with a smaller amp fuse instead of using a big amper for all three at once.

The inverter pos to that buss point would have a big ANL and the converter wire might have a 60a resettable Dc circuit breaker. The slide and jacks already probably have 30a fuses and the 7-pin charge wire might share one of those already or have its own. Solar pos from controller has own or might share with converter's. The Trimetric has its own little fuse too--forgot that one above so now its eleven positives. Add the LP alarm and the stereo, for thirteen.

Thanks BFL13 for the idea on the Trimetric on the negative side, seems so obvious now, but hadn't thought of it!

I originally was planning to fuse after combining the 3 batteries, but after thinking through this more, maybe it's better to fuse between each battery and the bus bar- thoughts?.

This is a HTT, so I have the batteries on the tongue- wish we had a 5ver with all that storage up front.

What about using the battery side of the battery switch as the bus connection?

I use buss bars. It's just easier to do.

Hi 2oldman,

Yes, there are two other ways.

Best is a buss bar with equal length cables.

Alternate is all equal length cables but double up on some of them.

i.e.

feed/charge positive==positive--positive

and

negative--negative==negative feed/charge

the equal signs are the doubled up interconnects of equal size and length.

My own opinion is that this does not work as well as the buss bars. This second method MIGHT work better if the doubled up cable was beefed up to be 1/2 the resistance of the single cable. For myself, I'll keep to the buss bars.

I don't have the math skills to figure out if this variation really makes a difference. The buss bars DO make a difference.

2oldman wrote:
Take the + from battery one and the - from battery three. Is there another way?

If you have a Trimetric, then the battery end of the shunt is one of the "buss bars" you can have three neg links from, one to each battery.

Now you just need to have a positive "buss" to take the three positive links, plus whatever else. The inverter positive terminal and a short wire from that to the "buss" can be a common point for those three plus inverter, that's four, now add solar pos and converter pos, the breakaway pos, the slide pos, the jacks pos, and the 7-pin pos.

So you need a buss to take those ten positive wires and let the inner end of the Trimetric shunt take all the negs (except the three battery negs)

You need appropriate size fuses on those positives, but you can have some wires "share" a fuse just before the buss connection

Hi Marc,

Look no further. I use a buss bar with equal length cables from my group of 3 battery bank.

marcindy wrote:
Don, I know method #3 is the best way to connect, I was looking for actual examples people have used. Twisting wires together with electrical tape I don't think will cut it! :-)

Marc

600 amp bus

These guys will make up some pro looking battery cables all crimped and sealed with heat shrink for a good price. No wire nuts and tape for this application.

I am running an inverter, and draw 100A+ once or twice a day. I was thinking about using a bus bar, I have one to connect all the grounds from the solar charger and inverter (the + leads all run through Blue Sea switches).

Don, I know method #3 is the best way to connect, I was looking for actual examples people have used. Twisting wires together with electrical tape I don't think will cut it! :-)

Marc