The Stovebolt Site Forums The Shop Area The Electrical Bay Adding a second battery

I was thinking about doing a little addition to the truck. I want to add a second much much smaller 12v battery to power a stand alone accessory. The kicker is it would be nice to have this second battery still hooked up in some way so it can still be charged when the truck is running.

Has anyone done this before or know the correct way of connecting it up so it stays charged? Is it as simple as connecting it in parallel?

connecting it in parallel would be the equivalent of adding a larger-capacity primary battery. both will discharge/charge together. for whatever reason you want standalone power for your accessory - a parallel arrangement will not accomplish it.

Use a continuous-duty solenoid to connect the auxiliary battery to the charging system while the vehicle is running, using the ignition switch to power the relay. With the ignition off, you will have a way to draw power from the extra battery only, with no drain on the starting battery. Most RV dealers will have that solenoid, but they're also available on Ebay without paying the RV store ripoff prices. Those guys are as bad as (or worse) than the old truck resto-ripoff parts guys!

Search "battery isolation relay" on Evil-bay!

Jerry

So hooking a smaller 12v atv battery in parallel with the standard batter would be ok right? I think doing it that way will work for what i need to do.

A little more detail about what you're doing would be good. The extra battery is either a good idea, or totally unnecessary and useless, depending on what you're doing with it. If whatever accessory you're planning to power is only going to be used when the engine is running, you don't need another battery. If you're worried about running the starting battery down when the engine is off, you MUST install an isolation solenoid.
Jerry

OK so laugh all you want but this was my thinking. Its to do with theft. Just heard another story from a local that had a truck stolen. They knew the vehicle and cut the battery cables thus the alarm was only sounded for seconds if that. My idea was to possibly have a remote small atv battery that can be installed in some other location that can feed the alarm, but stay charged from the stock wiring. if someone cuts the main battery wires it would actually do nothing to the second smaller battery and still sound at least giving a person a better chance they will leave it alone.

Thoughts?

If all you're planning to power is a burglar alarm, use two square dry cell 6V lantern batteries wired in series and replace them once a year like smoke alarm batteries. No need to recharge- - - -they last three days past forever if they're not used much.
Jerry