Battery chargers operate when connected to the 240V AC mains connection. Most of the Plug In units use the car/caravan switch to decide which battery is being charged. The centre position of the switch is an off/storage position and also allows the charger to act as a power supply instead of a battery charger.

A couple of methods to see if your Manufacturer fitted Plug in charger is working.

 1. Turn the Car/Caravan switch to the center position. With the charger switched on you should have power showing on your battery meter and lights etc should be available. Also look for an excessively high needle position on the battery meter indicating a out of tolerance charger.

 2. With the Car/Caravan switch in in the leisure battery position, watch the battery meter/indicater whilst you turn the charger on. The battery level should improve.

Boiling Batteries and Overcharge 

If your battery starts to smell excessively or the casing starts to swell, there could be a fault with the battery or charger. Either way a profesional test is recommended to ensure a replacement battery does not befall the same fate.

The charger can cause a battery failure if its output voltage goes high. Typically signs of this are a higher reading on the battery meter than normal, brighter 12v lights and a higher failure rate of said lights. 

The battery can also fail of its own accord. This can be due to one of the 6 cells that make up the battery failing due to a short within the battery. A high current then passes through the other 5 cells causing excessive gassing heat etc.  

Units and corrective action.

KT12SM and Interpower Unit can have a push and twist style fuseholder. Use a flat bladed screwdriver that fills the head to push and twist the centre insert anticlockwise to release the fuse. Replace the fuse if failed with the rating indicated. If the unit still fails a complete replacement charger is usually required.

PMS1 and PMS1hs The first 12v fuse on the left is the charger fuse. The charger is replaceable with a circuit board.

 PMS2000 or PMS6 units have the KT12SM or Interpower charger built into them.

PMS3 - PMS4 - PMS5 - PMS7 - ESM and ESM 2000 units all have an internal circuit board (PCB) to charge the battery. Replacement PCB^s are available. The PMS3 charger is fused on the front panel. The ESM unit has an external fuse along with the vans fusing. Normally close to the charger look for a black fuseholder with a clear cover witha label for the fuses. The ESM2000 has no external fusing.

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