WORDS : MARTY LEDWICH

There are essentially three-types of 12V lead-acid batteries that are generally used in caravans and other RVs : wet cell , sealed gel and absorbed glass mat ( AGM ). It is possible to fully discharge these batteries , but you can risk damaging them if you do .

You should avoid discharging lead-acid batteries below 50 per cent state of charge ( SOC ). If you have brand-new batteries and you discharge them below this level once or twice , they will generally suffer little damage , but repeated deep discharging below 50 per cent SOC will shorten their life considerably .

SULPHATION

Deep discharging causes ‘ sulphation ’, or the build-up of lead sulphate on the plates inside the battery . Over time , these sulphates harden and lessen the area of lead exposed to the acid inside the battery , reducing its electrical generating capability . In extreme cases , this build-up can crack the lead plates , effectively rendering the battery useless .

The production of lead sulphate is a normal part of lead-acid based batteries discharging . Recharging the battery reverses this process ; however , if the battery is not fully recharged , some of this sulphate can remain on the plates . If the battery is subjected to repeated cycling without being fully recharged , the sulphate layer will increase and harden in a similar manner to that of repeated deep discharging .

Combine regular repeated deep discharging and inadequate recharging through the normal use of these batteries and it is easy to understand why so many owners experience early battery failure .

Lithium batteries are generally capable of sustained discharges to 10 per cent .

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