I am using this. And it works good.

PowerBox™ Electronic Switch

Parallel redundant switch and regulators all in one. Ideal for smaller models and models up to 27%. Will handle up to 5 amps continuous. The switch is a fail safe type with led lights for visibility. Designed to work with any of the DURALITE PLUS batteries.
• Power handling up to 5.0 Amps (according to heatsink)
• Two independent linear voltage regulators, supplying 5.90 Volts
• Two independent electronic switches
• Two volt controller ( in 4 steps ) for each battery
• Two Low voltage memory for both batteries
• SET button for On / Off switching protection
• LED indicators for both power circuits
• Operating voltage range 4.0 to 9.0 Volts
• Temperature range -10° to +75° C
• Voltage loss approx. 0.35 Volts
• Weight only 35 grammes incl. all cables


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