What size solar panel to maintain batteries?

[RPW]

In addition to the foods add a ballast resistor. It will prevent a battery that dies from pulling the whole system voltage to near zero. Also will help balance the current between batteries.

 

[Soundguy]

diode isolation will completely take care of the cross current isue of one bat dieing killing the other bats.

soundguy

 

[greasemonkeyok]

Happy there are folks smarter than I here.

Soundguy, does the resistance always go up on a battery that goes bad? Or could it go down and draw all the current through that one path? (Showing my ignorance again.)

 

[Redneck in training]

Happy there are folks smarter than I here.

Soundguy, does the resistance always go up on a battery that goes bad? Or could it go down and draw all the current through that one path? (Showing my ignorance again.)

The high resistance is usually the case. The resistance goes down only when there is enough sediment or broken plates that they short together and it usually doesn't happen in all cells.

 

[Soundguy]

Happy there are folks smarter than I here.

Soundguy, does the resistance always go up on a battery that goes bad? Or could it go down and draw all the current through that one path? (Showing my ignorance again.)

with the diodes in place, if you charged 3 bats, only the one bat would die, and possibly the charger.. other 2 would not draw down.. unless there was some spectacular weird failure in the charger..

 

[Redneck in training]

If the charger is designed right (equipped with current limiter or "soft" enough that the current will drop when loaded) it should survive short indefinitely. Since that is relatively easy to do I would guess that most chargers would survive such abuse.

 

[Soundguy]

If the charger is designed right (equipped with current limiter or "soft" enough that the current will drop when loaded) it should survive short indefinitely. Since that is relatively easy to do I would guess that most chargers would survive such abuse.

it's realitively easy to do, yet many don't.

soundguy

 

[Gordon Gould]

In the case of one bad battery the simple diode isolation scheme will prevent the good batteries from discharging but the good batteries will not be charging either. All the charging currant will pass through the low voltage bad battery. It is way better than having the good batteries discharged just be aware that one bad battery will prevent the others from receiving their maintenance charge.

 

[greasemonkeyok]

Thanks Gordon, that was the point I was trying to address. It is a remote probability, but nonetheless a weakness in using one system to charge four batteries.

 

[BobRip]

In the case of one bad battery the simple diode isolation scheme will prevent the good batteries from discharging but the good batteries will not be charging either. All the charging currant will pass through the low voltage bad battery. It is way better than having the good batteries discharged just be aware that one bad battery will prevent the others from receiving their maintenance charge.

I agree.