Which size Battery

Nick Hearne · 08 May 2004, 15:35

Hi can anyone advise me on battery size for my boat?
It has 100hp Johnson, fish finder, GPS & VHS!
It has at the moment 2 X 75 amp Marine/leisure batteries which I think may be a bit overkill!
The recommended cold crank start for the engine is 340 or 360 can’t quite remember, but UK batteries all seam to be in amps!
Any thoughts anyone?
Nick

Jizm · 08 May 2004, 15:42

That is approximately the same size cranking power as you need for a small petrol family car. Why not just go for a couple of batteries from a motor factor, will be cheaper than buying a leisure battery, seeing as it's a rib and has no need to run cabin lights, tv's, dvd's, etc without the engine running.
regards

tue · 08 May 2004, 16:11

1x 85 amp hour leisure battery should be sufficient for your RIB. The advantage of a leisure over car battery is its ability to be run completly flat and still recharged without damage to the cells or plates which will happen if car bettery is run completly flat.

Nick Hearne · 08 May 2004, 16:34

Thank you Paul that sounds good to me!
Jizm as the boat can be left for long periods of time the leisure battery should be better bet as it can take longer periods with out being charged! Car batteries kneed to be used/ charged on a regular basis.
Nick

Headhunter · 08 May 2004, 17:12

Nick

You can get 85AH leisure batteries for around £35, cheaper than normal car batteries.
Our local A1 motor parts outlet is doing them for this price.
Other wise try a caravan or camping outlet.

Don't forget to check which terminals you have.

John

jwalker · 08 May 2004, 17:21

Quote:

Originally Posted by Nick Hearne

Jizm as the boat can be left for long periods of time the leisure battery should be better bet as it can take longer periods with out being charged! Car batteries kneed to be used/ charged on a regular basis.
Nick

Not mine. My leisure batteries are pretty flimsy compared to my car batteries. They discharge equally fast and they're not designed to have large currents drained from them.
Go for a car battery. On it you will find, **CCA = Cold Cranking Amps. This is the starting current available from the battery. You'll find quite a small amp/hr battery will easily give you the current you require.

Headhunter · 08 May 2004, 17:25

Nick

My recently departed Johnson 90 2 str had a 40AH battery which was fine.

John

gavin · 08 May 2004, 18:35

Remember car batteries arnt sealed, they gas and miniscule amounts of acid can come out, this is why we often top up with de ionised water, marine batteries however are sealed, bear this in mind with a boat going up and down waves etc etc

Suzuki416 · 08 May 2004, 19:16

I of my other pastimes is Off Road driving & as I have a winch fitted this 'kills' batteries & so have gone though 7 batteries in 3 years due to the buckled plate syndrome.
This has cost me a grand total of £58.

Reason:
Buy it from Halfords with a 4 year garantee... & keep taking them back when they die.
Oh,
I STILL HAVE A 4 YEAR garantee on my newest battery...

Nick Hearne · 08 May 2004, 20:09

So I go for a cheep battery from Halfords & just take it back when I kill it off for a new one!
Nick

Suzuki416 · 08 May 2004, 20:14

Yep - thats exactly what I do.

Richard B · 08 May 2004, 20:41

Quote:

Originally Posted by Suzuki416

I have a winch fitted this 'kills' batteries & so have gone though 7 batteries in 3 years due to the buckled plate syndrome...Buy it from Halfords with a 4 year garantee... & keep taking them back when they die.

So correct me if I misunderstand you Pete, but you're advocating dishonesty?

Pete7 · 08 May 2004, 20:46

Quote:

Originally Posted by Richard B

So correct me if I misunderstand you Pete, but you're advocating dishonesty?

Whats dishonest ? he is using it in a car. Assuming he asked for a car battery thats what they sold him, a battery suitable for a car. You could argue that Halfords sold him a battery that wasn't suitable for the job (trades description Act and all that) so they give him a free replacement so he doesn't sue them.

Sounds fine to me.

P

Richard B · 08 May 2004, 20:49

Quote:

Originally Posted by Pete7

You could argue that Halfords sold him a battery that wasn't suitable for the job

Mmmm... did Pete ask for a winch battery? He's stated that he knows that they kill batteries...

Pete7 · 08 May 2004, 20:58

Winch is normally wired into the engine battery with starter motor thickness wires as the drain is huge. If your really going off road then a second battery wired in helps, but its still a car battery.

P

Richard B · 08 May 2004, 21:36

Quote:

Originally Posted by Pete7

Winch is normally wired into the engine battery with starter motor thickness wires as the drain is huge. If your really going off road then a second battery wired in helps...

So you acknowledge that the current drain is huge, used for longer periods than a starter motor (usually seconds), and that a second battery is needed. Yet you still defend your conspirator!

Pete7 · 08 May 2004, 21:42

Quote:

Originally Posted by Richard B

So you acknowledge that the current drain is huge, used for longer periods than a starter motor (usually seconds), and that a second battery is needed. Yet you still defend your conspirator!

Yup, top bloke!

pete

Richard B · 08 May 2004, 21:54

Remind me never to do business with an ex-squaddie!

jwalker · 08 May 2004, 22:51

Quote:

Originally Posted by gavin

Remember car batteries arnt sealed,... this is why we often top up with de ionised water...

Lots, if not most, car batteries are now spill proof and sealed so as never to need topping up. They have a wee vent which can take a tube. This can be vented directly out of the battery compartment/console so that no hydrogen gets trapped inside the boat.

I've a small one sitting at the side of me. 270CCA and 33A/hr, cost £22. 48A/hr is probably more than adequate for your engine.

Nick Hearne · 08 May 2004, 23:30

According to my Clymer manual minimum recommended CCA IS 360 CCA & 115 Minuets reserve!
What ever that means?
Nick