Adding a second battery.....

[BrianBlair]

......two questions:

1. If adding a second battery....does it need to be the same size/specs as the first?

2. Cables. How do I determine what gauge cables I need for the run between the two batteries?

Thanks!

BB

[1der]

Brian,

Is this for a house or second starter battery?

If for house it can be different although all the batteries should be of the same construction, ie AGM, Flooded Lead Acid, etc. Starter batteries should be the same.

Cable - There are calculators on the web for wire gauge needed for amps/voltage distance. If you post up what amps you will be drawing/charging and teh distance, I/or someone (scalf probably) can double check. Make sure to incorporate fusing requirements as this can add to your distance.

Main thing needed right now is more details as to what you want to do and what the layout will be.

[BrianBlair]

Sorry...I should have been much more thorough in my description!

I bought a 175ah AGM battery to replace my existing group 24 battery. We've found ourselves lacking enough power for running the fridge on consecutive hot days in the summer when parked for multiple days.

I bought the 175ah battery thinking I would replace the group 24 with it. Then I got to thinking.....can I just keep the group 24 in place and add the new battery to have even more power.

I guess the remaining question is whether or not the group 24 is AGM?

The batteries will only be about a foot from each other, under the gaucho.

BB

[Viva]

Mostly to echo what's already been said.

1) Ideally any bank of batteries (i.e. house bank) should be the same type, size, and age. Life isn't always ideal, but given the cost of batteries, and the annoyance (at least to me) of having potential degradation of function, I try very hard to adhere to this. Now, I might add a second battery of the same type/size/brand some few months after the first one, but probably not much past that. I just feel there are enough "mysterious variables" with battery chemistry that I want to eliminate that as a possible cause.

2) As far as jumper wire size, as mentioned above, you want to know how many amps (maximum possible) you will have going through those jumpers (charging or discharging), and the length (one way) of them. Then you can use a voltage drop calculator to see what you need. Keep in mind that if you are calculating voltage drop for something sensitive, such as the run from solar panels to solar controller, to batteries, and through jumpers, you have to add up all the legs. Since the jumper legs affect every circuit, I like to minimize voltage drop here. The two factors that "ding" you here are number of amps, and length of run(s).

The other thing you need to make sure is that you can fuse large enough. Say you are going to have a "jump start" link between start and house banks. And say your starter draws 150 amps (not counting inrush current). Then to me it would be nice to have wire that I could safely fuse to 200 amps. If not, I'd go up a size.

If you post some specifics, I'm sure folks here would be happy to double check your calcs (or just do them).