Are Diodes Needed to Use OptiMate Solar Panel Kit

Updated 09/18/2025 | Published 09/10/2025

Question:

Please review the attached sketch. Would this be a practical connection for this charger? I would like to maintain the battery isolation when necessary, without disconnecting the charger. Would the diodes accomplish this? Also, can this charger be left in circuit when the engine is started/running? 10 W should be sufficient for maintaining charge on the two batteries.

asked by: David S

Diode Sketch Charger
(click to enlarge)

Expert Reply:

Hey David, I am curious why you think you need diodes to install the Optimate Solar panel kit part # MA69JR? You don't need to worry about the voltage getting past the controller as it essentially has a diode system built in. This can also be left on and charging when the vehicle battery is getting charged by the alternator as well.

expert reply by: Jameson C

David

9/18/2025

The diodes are intended to prevent flow between the batteries, not for backflow to the panel. The intention is to keep the batteries isolated when the selector switch is in the "OFF" position. Should one battery drain, for whatever reason, the other battery should be separated so as to hold its charge.

Jameson C.

9/18/2025

@David ahh yeah I see what you mean now. Yeah I can see why you'd want that then you would only need a single diode like the # RM-690 on the power wire and that would be sufficient.