AccuMate – how to connect to vehicles with 2 batteries.

Some vehicles (MGB for example) have 2 x 6 Volt batteries wired in series to provide a 12 Volt supply.  We are often asked how AccuMate should be used in these circumstances.  The examples below are for 2 x 6V batteries in a 12V vehicle – However, the same procedure applies with the AccuMate Pro 12V / 24V charger and 2 x 12V batteries in a 24V vehicle.

As a diagnostic charger, it is best that AccuMate is connected to one battery only – in this way, if there is a problem with one of the batteries, AccuMate will be able to detect it and charge it accordingly.  The only problem with this arrangement is that one has to “cycle” the use of one AccuMate between the 2 batteries, which is not always practical, for example during long periods of storage.  To use this method, connect a permanent connection lead to each 6 Volt battery individually, as shown in the top picture (you will need to purchase one additional lead).  Set the AccuMate to 6 Volt output and connect to either of the 2 connection leads to charge one battery at 6 Volts.

If you are confident that both the batteries are in good condition, a more practical (but less technically correct) method is to treat the batteries as one 12 Volt assembly.  To use this method, connect one permanent connection lead across the two 6 Volt batteries as shown in the lower picture.  If it is not clear which lead is the link between the two batteries, you will either need to use a multimeter to check the connections (look for 12V between one battery’s negative and the other battery’s positive).  Alternatively it is acceptable to connect the permanent connection lead to any permanent 12 Volt part of the vehicle’s wiring (i.e. there must be 12 Volts present with the ignition switch turned off).  Set the AccuMate to 12 Volt output and connect to the connection lead to charge both batteries simultaneously at 12 Volts, with 6 Volts going to each battery.