Battery advice please

[lakelandterrier]

Suffered an annoying problem to day when I found out the hard way my battery didn't have the juice to fire up my Merc 40HP 4-stroke. could have been worse - I was tied to the pontoon, not 3 miles out!

anyway, on checking the battery a 6 cell acid-lead 12V 85Amp jobbie that was new with the boat last year & has worked fine , I found that it was seriously (0.5l) short of water. Topped up the cells, put it on charge & now appears to be OK...BUT this raises some probably very basic questions for me who is not enginering minded.

1) There is a ?vent? hole on the top of the battery, from which electrolyte will come out if tipped. As this would be mild acid is it right to have a non-sealed unit?

2) What could have caused the loss of liquid - how do I prevent it in future?

3) How will I know the batttery will not fail again - in a more threatening sitution.

4) Should I invest in a sealed calcium gel type battery - and if so what would people recommend?

5) Is there a way of knowing if the battery is losing charge in advance. My rib is a basic 4m Avon, no instrumentation / electronics installed.

6) I thought the engine charge the battery when running - is this so or not. If not I will put the battery on charge regularly.

[Ian Sharlot]

Hi

Your battery doesn't sound like a marine battery and should not leak, your local supplier can check your battery, but my advice would be to go out and get a marine/leisure battery. you don't need a gel battery but some do prefer them and you engine should charge the battery assuming there are no fault

[Nos4r2]

I'd investigate your voltage when running the engine. It might be cooking your battery if it's that short of water.

[Poly]

Originally Posted by lakelandterrier

2) What could have caused the loss of liquid - how do I prevent it in future?

spillage is a possibility - but natural evaporation is a possibility - its also possible from excessive (?)charging of the battery (which turns water into hydrogen and oxygen). It would be worth taking a careful look at the cells for significant bubbling when the engine is running - it could be you either have an alternator problem or need a more sophisticated charging system.

3) How will I know the batttery will not fail again - in a more threatening sitution.

measure the voltage (either install a little monitor or just use a voltmeter - it should give you some idea of problems. But now would be a good time to try out the emergency cord start that came with your engine - so you know how to use it if the worst happens.

5) Is there a way of knowing if the battery is losing charge in advance. My rib is a basic 4m Avon, no instrumentation / electronics installed.

see 3.

6) I thought the engine charge the battery when running - is this so or not. If not I will put the battery on charge regularly.

it will do on most outboards. But the battery will also discharge just from sitting doing nothing so if it has been "neglected" for a few months you are probably expecting a lot for a basic engine charging system to get it back to tip top condition.

[Chris]

If you want to go down the totally sealed maintenance free route then get an AGM type battery. Merlin power-store sell the Odyssey range. I always go on about these but that is only because they really are fit and forget. You can leave one for 6 months and it will still be 99% charged. They are totally sealed and have a 5 year warranty, they are also much smaller that the equivalent wet battery.

For a 40HP I would have thought this one would suit
http://www.power-store.com/view-item...d=1659&id=214&
however just ask them to confirm which would be best for your engine.

Chris

[Andy Moore]

We bought a solar panel to trickle charge our battery. We can now leave our Rule pump on all the time too.

The battery fires up our Merc fine now.

[jyasaki]

Originally Posted by lakelandterrier

3) How will I know the batttery will not fail again - in a more threatening sitution.

Short version: You don't.

Longer version: The only way to obtain confidence in your starting system is to maintain stuff in a way that keeps it working well. That means checking out the motors charging system, checking out (or replacing) the battery, so you know it's operating correctly, and keeping the battery charged while not using the boat (discharging a starting battery to below about 60% may damage it. If you need the capacity to run for those lengths of time, look at a deep cycle battery rather than a starting (or cranking) battery.

4) Should I invest in a sealed calcium gel type battery - and if so what would people recommend?

I wouldn't. Gel cells require a much more closely managed charging circuit. Their input range is much tighter than a standard flooded wet cell or an AGM. Too much voltage will fry a gel cell, and they're not exactly cheap.

If you need to mount the battery in a strange orientation, or if space is an issue (or if you're like me and don't maintain batteries all that well), then an AGM (Absorbed Glass Mat) battery is the way to go. The electrolyte is held in a fibreglass mat between the plates, so the battery can be mounted in any orientation and not leak. [Note that *any* flooded wet cell battery - even the "sealed" maintenance free ones, may leak. They have a small vent to relieve pressure when charging, and if mounted so the electrolyte is at the vent pickup, will spew the electrolyte rather than the gas.]

5) Is there a way of knowing if the battery is losing charge in advance. My rib is a basic 4m Avon, no instrumentation / electronics installed.

Measure with a voltmeter while not running the engine. A fully charged battery will read 12.4 to 12.6 volts or so. A reasonably charged battery will read about 12.2 volts. Anything lower than 12.0 Volts would probably be reason for concern (meaning it needs a charge; not necessarily that anything else is wrong.)

6) I thought the engine charge the battery when running - is this so or not. If not I will put the battery on charge regularly.

That should be so. Again, a voltmeter will tell you. Anything over the voltage read in the previous step means current is flowing into the battery. The actual voltage depends on how the charging circuit is set up in your motor, but at higher-than-idle revs, you should have at least 13 volts, up to about 14.6 volts. Any more than that is cause for concern. Any less than about 13 would be as well.

If you leave the boat on the trailer (or on the mooring) for longer than about a couple of weeks, a trickle charger would be a good idea. AGM's will hold a charge longer than a flooded wet cell, but in either case, keeping the battery topped up is better than allowing it to self-discharge. Make sure you use a smart charger (shuts off or nearly shuts when the battery is fully charged); overcharging is as bad as allowing it to discharge.

jky