Mastervold Battery Mate - Universal Car Battery Charger & Maintainer for Cars, Trucks, SUVs - Perfect for Winter Storage & Emergency Jump Starts

Battery Mate’s technology is electronic and includes mosfets (transistors). Its components compensate for the voltage drop and ensure that charging continues at the right voltage level, even with several battery banks. In contrast to Isolators, Battery Mate allows you to charge two or three batteries at high capacity with various alternators.
Battery Mate is compatible with any type of alternator/battery charger, in both existing and new systems
Battery Mate performs far better than conventional battery isolators as the voltage loss between the alternator and battery is negligible
With these battery mates you will have fast and complete charging of your batteries without having to make additional adjustments to the alternator. 
Features

• Compact and lightweight Isolators – just weighing 2,2 lbs
• The isolators are Robust and durable – made to be corrosion proof with aluminium heat sink, and fitted with electrical components encased in synthetic material
• Easy installation - these isolators have synthetic end plates with connection lugs, solid bolt connections with nuts and locking rings. All of these items ensure easy installation.