I’ve been thinking a bit about adding a second accessory battery, in the bed of my truck to double the battery reserve while camping. This would provide additional power for camping, especially camping multiple days during the winter when there is little solar radiation, or even camping at campsites with a lot of shade. I want to be able to camp multiple days with ample power.

I would probably get another matching Group 24 battery, stick it in the bed of my truck in a marine battery box, and just tap it into the system via the bus bar I have mounted in the shelf on my truck cap.

I could probably do it for around $120, as I have the wire and fuse, but would need the battery, a marine battery box, and a fuse holder.

A few things that give me pause …

1. A Group 24 battery weights 45 lb.  While that’s not a lot of weight for a 7,000 lb pickup truck, it does add some weight, and could make things a bit further out of balance and require moving around the weight in the bed.
2. The third battery would be mounted in the bed and take up space. While I have a fair of space, and things could put on top the battery box, it still more space taken up by the battery, plus additional wires, fuses, etc.
3. Different age batteries could fight. I don’t really want to replace the other accessory battery, so fighting batteries could reduce the charge that they both would take. But I tend to think the advantage of the additional battery would be greater then losses from fighting.
4. Batteries produces hydrogen when the they charge. I don’t want to be smelling hydrogen sulfide when I sleep, or have it be burning me. While I think the bed is fairly well ventilated, I don’t want hydrogen to build up in the cap and go bang like the Hindenburg blimp.
5. The second accessory battery would be beyond the low voltage shut-off, as it would be connected directly to bus bar that powers the accessories in the truck cap. That means I wouldn’t have under-voltage protection for that battery, but with the two batteries for reserve, my very modest load, and the solar, I doubt I would have too many under-voltage conditions.
6. It’s additional load on alternator and solar panel, which means it will take longer to charge two batteries even if it takes longer to discharge, and discharge cycles will be less deep.
7. Plus it’s $120 bucks that wouldn’t be in my wallet anymore. While I would get a lot of use out of it, and I could use the battery box for other projects, batteries don’t last forever.

I want to give this a bit more thought, but if I do set this up, I’d like to have it all working and fully tested before my Independence Weekend trip up to Moose River Plains.