2 + 1 battery connections ???

[Rbertalotto]

I'm getting ready to use the long holiday weekend to install my solar system on my travel trailer.

2 X 140w panels, Bogart Engineering solar controller....

I just bought two AGM Group 31 12V deep cycle batteries, but the TT has a new 12V wet cell already installed. I know if I connect all three together they will discharge each other as they are not same vintage or same type.

I could put a simple battery selector switch in the system and manually cycle them to supply and charge.

But is there an automatic device that could handle this chore automatically. Any personal experience with such a setup?

Thanks

 

[DiploStrat]

Basic Roolz

The basic rule is that you can connect dissimilar batteries together when they are on charge and you must disconnect them when they are on discharge.

Soooooo, your homework, should you decide to continue it, it to get hold of the tech manuals for each of your batteries and compare the recommended charge profiles, specifically maximum voltages and amperages. If they are close and you can adjust your charger, then you can probably charge all of your batteries at the same time. This is especially so for your engine alternator, because you will probably never run your engine long enough to achieve a really complete charge, and more of a problem for your solar controller because you will.

For discharge you can either split up your circuits or wire up an A/B/A+B switch.

I don't know of any way to automate this mess. Someone else may have better ideas.

I might just look at putting the FLA on Craigs list. (Or sell the AGM's and get another FLA.)

 

[Rbertalotto]

Well...I just remembered that it can't be done as the Bogart Engineering system needs to know what type of battery you have to perform its magic. Switching back and forth between different batteries will mess up its memory and screw everything up.

So I'll just install the "mess" with the two AGM batteries and be done with it.

"For Sale....near new wet cell 12V battery!"......:sombrero:

 

[DiploStrat]

You don't have to be exact, just make sure that you don't exceed the lower of the two specs. As a practical matter, each of your batteries probably calls for a range of voltages; set to the lower. Voltage is important (generally the higher the better) but time is essential. More batteries die from too little time than from too much voltage.

280w is only going to give you about 15A most of the time.

Lead acid batteries are simply not that sophisticated. The challenge will come when you discharge the beasts. Assuming that you have a decent meter and that either battery can handle the whole load, use an A/B/A+B switch. Use A or B when discharging and A+B when charging.

But I would still stick with one type or the other. ;-)

 

[Rbertalotto]

thank you!