Will outboard damage battery

[Drascomber]

I am told that whilst "wet" lead acid batteries can stand a current that continues after they are fully charged, the sealed lead acid variety can be damaged.

Now, as I understand, it the charging circuit on a small (say 6 to 8hp) outboard should have a rectifier but will not have a regulator. Meanwhile several folk I know use a small sealed lead acid battery of around 7AH for the instruments and "get you home" nav lights.

So, can this be quantified - How big does the battery have to be to survive continuous 3 Amps or 5 Amps?

 

[danera]

This is similar to leaving a solar panel continuously connected without a regulator to trickle charge the battery, in which case the rule of thumb is max current 1% of battery capacity I dimly recall to prevent overcharging, ie 1A for a 100Ah battery, so you would be looking at quite a large battery to take 3-5 Amps. I think you are either going to need a regulator or a switch in the charging circuit if you will be motoring for long periods.

 

[VicS]

5 amps is the maximum output from many/most small outboards. You will only get that at high revs and it will fall as the battery charges.

7Ah is bit on the small side though and I think I would take steps to monitor it and stop charging once fully recharged. My battery is 60 Ah and I regard the input to it from the outboard (5 amp max) as insignificant. One of those LED devices would be adequate but the rather nice "Voltwatch" one is NLA.

You say, "as I understand, it the charging circuit on a small (say 6 to 8hp) outboard should have a rectifier but will not have a regulator".

For battery charging it MUST have a rectifier but you are correct you would not expect to find a regulator although I believe some of the latest do have. Some engines have a rectifier fitted as standard (mine does) but others need a special and ludicrously expensive charging adaptor.

I would not like to quantify the minimum size of battery. I used to have a 45Ah leisure one but 60 Ah was the smallest available when i replaced it.

 

[Loginname]

If you want to keep the small battery one of these would probably solve the problem

http://www.maplin.co.uk/Module.aspx?ModuleNo=97384&&source=14&doy=30m5

At £25 for the 8amp one, it's certainly cheaper than the OEM route.