Elec help needed to charge house batteries

[pvcces]

John Z, it has to go from pattery positive to battery positive on as short as possible of a run to get the benefit of the starter boost capability when the starter batteries become very discharged.

This is going to depend on where your batteries are mounted.

Tom Caffrey

[John Z]

Thank you Tom. I was not sure if it would make a difference whether at the bus/start battery end, it was attached to the battery post or to the junction block mounted on the bus.

How about the neg cable on the house bank, should that be as large as the positive cable?

Gosh i will be glad to have this installed and working.

[gumpy]

John,

If your house batteries are closer to the positive cable bulkhead lug from the coach batteries than they are to the coach batteries, that would be just fine. If they are closer to the coach batteries, then hook it to the battery positive post.

Due to the size of the cable, it may be better to mount a separate bulkhead stud if you can't attach directly to the positive post. You can get these from Waytek. They also have pass-thru bulkhead studs, which work well to go through a panel.

The negative cable should be the same size as the positive and preferably should go to the same grounding lug as the coach batteries. That may not be practical, however.

Here's a few photos of the coach battery side of my crossover connect.

[gumpy]

Here's the other one....

[John Z]

Thanks much Craig. The house batteries are almost 18 feet from the start batteries, so at 4.00 a foot for cable, it looks like it will have to go to ground right at the house bank. I do appreciate your help again! We were commenting last night at all the things that had to happen just right in order for us to be able to leave tonight,, and it looks like we are going to make it!

[pvcces]

John Z, at 18 feet of distance, which means 36 feet of total conductor, you will likely be beyond any recommended distance for a large inverter. And the starter will draw more when cranking than an inverter.

Perhaps you will be able to figure out how to get a better setup.

Tom Caffrey

[John Z]

Thanks everybody for all your help. The guy at the welding shop talked me into 1/0 cable, said it will handle 350 amps over 50 feet. I have it all hooked up, the bus is loaded, it is about -8 and we are out of here!

[TomC]

Highly recommend you go with 4/0 or 0000 cable.  There is no such thing as too big of a battery cable.  A 1/0 just seems small to me.  Good Luck, TomC

[gumpy]

Thanks everybody for all your help. The guy at the welding shop talked me into 1/0 cable, said it will handle 350 amps over 50 feet. I have it all hooked up, the bus is loaded, it is about -8 and we are out of here!

It appears, according to Jock Fugitt's information, that a 1/0 cable at 200 amps for 50 feet will have a voltage loss of 1.22 volts. That's 10% on a 12 volt system. And at 300 amps, will lose 1.83 volts.  At 100 amps, the loss is 0.61 volts.

This can be significant. That means your batteries won't ever get fully charged if you're charging off the alternator. This could eventually lead to premature failure of the house batteries.

It's unlikely you'll ever be putting that much current through it. I wouldn't expect to see more than about 100 amps charging off the alternator, and only for a short time.

[DrivingMissLazy]

John, I think you will be just fine.
Some fail to consider that as the battery gets up to full change the current continuously decreases to the point that only a few amps will be flowing. There will be little or no voltage drop under these conditions.
Richard

[John Z]

Richard, i am in agreement with you. He showed me the chart they have in the shop and use to make up the cables. Actually, for my alternator he said i could have used 1 gauge wire. So using the 1/0 is overkill. Also, i am not running 50 feet of cable, only 20 feet. It has worked just fine so far. I must say, those golf cart batteries do seem the way to go. I am sure i will add another pair of them to the house bank before my next trip. We are in Little Rock, Arkansas tonight. Rain all day today, but temp is 55 at 8:30 at night. And after driving in -16 the first night out, i gotta say this feels just wonderful! Thanks to everyone for your help with getting me through the hook up of the solenoid etc. It works better than i had hoped. I guess now i need to work in the equalizer charger.

[kingfa39]

i ran battery cable from bus batt to a solinoid continuous duty to the house batt, have a swithcc in the driver area, has worked well for 20 yrs. had to replace the solinoid one time. romex is not the way to go, too light and its solid wire.
Frank Allen