Rustic cabin off grid. Seperate wiring for 110AC and 12VDc. Using solar panel through a Steca PR1515 charge controller to charge 2 12v batteries in parallel. If not enought light (at night) to charge batteries using solar, would it be OK to disconnect solar and connect automatic car charger (plugged into a generator)and set on 2amp trickle charge to charge batteries with current running through the charge controller? Would it damage charge controller?


closed as off-topic by PeterJ, Ricardo, Scott Seidman, Null, Nick Alexeev Oct 14 '15 at 15:40

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  • \$\begingroup\$ This is a design question. Really. You just have to read it with understanding. Whatever. \$\endgroup\$ – Russell McMahon Oct 14 '15 at 14:03
  • \$\begingroup\$ Questiomns MUST be re a design need - not re connection of off the shelf stuff - even if the design can be satisfied thayt way. eg "I have two 12V batterieds which are usually charghed from a solar panel via an xxx solar charger. To allow charging when there is not enough sun I wish to also be able to charge the batteries using a 110 VAC alternator and a 110VAC to 12V DC automatic charger or such other equipment as may need to be designed for the purpose. What circuitry do I need to provide to accomplish this task properly. Relevant details: ...." \$\endgroup\$ – Russell McMahon Oct 14 '15 at 14:14

It is highly likely that this will be OK in terms of damage BUT the battery will not charge well this way. Better woul;d be to disconnect the regulator to battery connection and connect the mains chartger to the batteries directly.

The input voltage to the regulator needs to be enough to allow for internal drop in the regulator. However, the automatic chargher expects to be "looking at" a battery and it bases its charghing decisions on what it expects to see. The drop in the solar regulator will almost certainly make the charger undercharge the batteries.

It is quite possible (but not certain) that you can safely connect the mains charger to the batteries at the same time as the solar charger is conmnected but there is no sun. This can be determoned by asking the manufacturer OR by conncting an ammeter and small resistor in serioes with the mains chargher and connecting it to the solar controller OUTPUT and seeing how much current (if any) flows into the solar controlle. If it is very small then odds are there are blocking diodes on the output and no damage is likely. Not that this advice is "all care no responsibility" and you need to be happy that the advice is good.


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