Battery Maintenance Tips

Especially this time of year it is important to look after your batteries, our main call outs at the start of the season and over the winter months are mostly battery related problems and mainly because they have gone ‘flat’ through lack of use, your boat will have longer spells of not being used and your battery charge will suffer from this. Your batteries require charging fully and just running your engine for an hour or so will not be sufficient.

If you do not have a battery charger fitted to your boat that you can simply plug in and turn on then either removing your battery(s), if it is out of the water, and taking home to charge up in the garage on a trickle charger would be a good idea. If you are on a remote mooring with no access to power than it would be a good idea to move your boat to a marina for a couple of nights to access mains power for charging or bring a fully charged battery to your boat and swap it out, then you can charge your battery up at your leisure knowing your bilge pumps and alarms are still operational. Do not forget bilge pumps will not work if your battery is flat or taken off the boat.


Your battery ‘state of charge’  is massively effected by the amount of fluid (electrolyte) within it. It is a good idea to check your battery fluid level before charging, if it is low it will never charge fully. Although the fluid is mainly acid it should be topped up with ‘de-ionised’ water and it is important to wear protective gloves and clothing as the caps you undo (6 in total) will be wet with acid underneath. Most batteries will have a level indicator moulded into them, it is important not to over fill as there is some expansion in the water due to temperature increases in the charging process. See diagram below;


CORRECT                                        TOO LOW                               TOO HIGH

If your battery is sealed it will have an indication hole which you can peer into and depending on the colour within will tell you the state of charge, there should be a guide written on the battery next to the hole to tell you what the different colours represent, if the indicator shows that the battery requires charging then do so , if it shows that it requires replacement, then the fluid is low and it should not be charged, and as it is sealed you will need to renew it, sorry.

But lets not forget about the outside of the battery, keeping the battery and terminals clean, dry and corrosion free will not only stop corrosion eating into your connections, eventually causing a loss of continuity, but also prevent voltage leakage between the positive and negative terminals via the damp and dirt between them.

batteriesWhen you are charging a battery which is flat and you are unsure as to why, be careful, keep an eye on it whilst charging, if the battery has failed completely it can start to get hot and emit a gas which smells foul, if this happens turn off your charger and isolate the battery at the battery switch. Do not try and undo the terminals as they will be hot and may have acid on them. It will then start to cool down and eventually it will be cold and you can swap it out for a new one. Warning – If left to carry on getting hot the battery gasses can cause the battery to swell and eventually explode. See image.

With good maintenance you will prolong battery life for many more seasons and knowing how expensive some batteries can be, it cant be a bad job to add to your list, now can it? I hope this tip has been useful to you and keep an eye on our website for more.