Batteries

[DM]

Anyone have any thoughts on batteries for a rib. Do more expensive marine labelled batteries really have any advantage over normal car types or is this just marketing hype? I know places like Halfords sell batteries with a picture of a caravan and boat on them but do these supply the high power required for cranking a big outboard? From what I've gleaned from mags like PBO the leisure batteries are designed to give a longer supply per charge rather than high initial output. The reason for this question is that I bought a marine battery for last season which gassed furiously after a good high speed run. whereas a normal car battery gave no problems.

D.M.

[Garygee]

Hi David

I dont think that deep cycle batteries as used on yachts have much place on RIB's. Ther are designed to allow them to be used as power when people are on board, lights, pumps etc, going long peroped between charge and hence being cycled quite deep, say down to 50%
They also tend to have a lower cold cranking capacity which is what you need to start your engine.

Also many so called deep cycle batteries are only modified car batteries anyway. You will pay a lot of money for true deep cycle batteries.

As far as starting I dont think you would have much trouble with a 115 outboard, a 300Hp diesel would be different. The thing that often lets most people down is not the battery but the cable used between the engine and battery.

As long as you dont leave it too long between use there should be little problem with self discharge, but in winter I would recomend to charge the battery before storage and then about every 3 months.

Personaly I belive that the most important feature of a battery on a RIB is the ability not to splill acid eveywhere as it gets thrown around. Save yourself lots of money and buy a sealed or semi sealed car or small lorry battery.

If you want lots off info on batteries drop me a e-mail and i will try and sort some info out for you.


Regards Gary

[Julian]

Hi Dave

We use 2 gel filled batteries in the scorpion. They are 3 years old and have never caused any problems. I think that they are expensive but they last. Never had to charge them up and never had any problems cranking the diesel over.

Julian

[Alan Mckewan]

"Marine" or "Leisure" batteries are designed primarily for "deep discharge cycle" - this means they are better at being run down to a low state of charge, very typical when being used to supply lights, TVs etc. in a caravan or boat. They are not usually quite as good at supplying very high current for short periods, more typical of starting a big heavy boat engine.
On the yacht I have one large deep discharge battery for accessories and one large ordinary one for the engine.
As you are unlikely to be using lights and watching TV on a RIB (except Cyanide) the standard battery will be fine.
It may be worth thinking of one of the sealed-type batteries that can tipped over without worrying - they should also be less likely to suffer from saltwater getting.
For our club RIBs I simply buy the cheapest possible and treat them as "disposable" as they get such a rough (and therefore short) life.

[Simon Guest]

Sorry, I'm rather ignorant on this subject. Can you overcharge a battery? Does it matter what charger you use? When I went into Halfords to buy a battery charger, I found they sold about 8 different types . The cheaper ones were rated at lower amps, and cost less than £10. For £30-£40 I could buy a charger which turned itself off automatically once the battery was fully charged. Is this over the top?

The assistant said that the low-amp chargers might suffer damage if used for a long time (i.e. to charge from a low starting point), but I suspect he knew only a little bit more than me (not much, you can tell).

Being confused, I didn't buy anything.

Can anyone help?

cheers,
Simon

[Julian]

Hi Simon

Yes you can over charge a battery and boil the plates inside. This will shorten the battery life and lead to you having to charge the battery more often. The cut of chargers are good. The bestthing to do is half charge the battery so that there is enough power to start the boats engine and go for a run.

Julian

[DM]

Thanks for the replies. The only thing I can add is that, after reading a couple of Johnson and Mercury repair manuals dealing with outboards up to 1994, they both state that sealed/maintenance free batteries should not be used with outboards because the output is not regulated as in a car and can reach up to 18volts. The difference can be seen between auto voltmeters which read up to 15/16 volts and the units supplied with outboards which read up to 18 volts. Perhaps later model engines are better regulated.

D.M.

[dgpw]

Hi my understanding is that a deep cycle batery has to be charged at a different rate to a standared car battery. A deep cycle battery will be trickle charged to begin with then the charge will increase and then decrease again as it moves through its charging fhases. (I may be wrong) The other thing about a marine deepcycle gell battery is that they can not spill acid all over the boat if they end up upside down ect. This has got to be a bonus because acid can not be good for the hull.