Checking water in auxiliary battery.

[Bazza Senior Member Find all posts View Profile Close Bazza]

Guys,
I have a reasonably new MarinePro 720 wet cell battery under the bonnet as my auxiliary battery. It is isolated by a Redarc SBI12. I also have a diode replacing the fuse on the alternator to increase the charging voltage.

When checking the auxiliary battery I noticed that the indicator was showing "add water". This is the second time in about 6 weeks. I checked and noticed that it needed some and that the top of the plates were exposed. After topping it up and driving it for a couple of days, I load tested the battery, checked the SG, and standing & charging voltages, all good. Hopefully the battery has not suffered from this.

Question ..... how often should I be checking the battery water in the auxiliary battery? I check the main battery about once a month ( if I remember ) and cant remember the last time it needed water. The auxiliary battery is running all my secondary lighting and power requirements, fridge power, etc .... stuff that really only gets used when I'm away.
Is it possible that it's being overcharged.

Bazza

[prado2004 Advanced Member Find all posts View Profile Close prado2004]

generally it should only need to be topped up every 6 months, using more water than that seems not right to me..

[J Janke Member Find all posts View Profile Close J Janke]

Something doesn't sound quite right with your aux battery mate. Unless it's charging about 14v I don't think it's over charging it.