marine batteries in Hampshire

andrew.adamson · 15 November 2005, 18:38

where is the best place to get these? Likely to need one for my 200 optimax so needs to 1000 MCA. Also, is it easy to make a dual battery set up?

Swifty · 15 November 2005, 21:46

Quote:

Originally Posted by andrew.adamson

needs to 1000 MCA.

Correct me if I am wrong, do you mean CCA Cold Cranking Amps?

As regards dual battery setup, easy peasy. Get yourself a battery change over switch. Available from all good stockists.

andrew.adamson · 15 November 2005, 22:09

book says 1000 MCA or 750 CCA.
Thanks

ashbypower · 15 November 2005, 22:18

Not just a matter of change over switch, you should really use a split charge diode pack aswell.

Regards

Brian

Swifty · 15 November 2005, 22:38

Brian,
Cant say I agree with using a diode pack, They are generally used on bigger boats with different alternators to that found in an outboard. Also they are quite big and not waterproof, so fitting can be awkward.

I prefere the line that using two batteries that are entirely seperate from each other, except for the change over switch, allows one to quickly change to the other battery in the evnt of a failure. Never use the both setting, as a fault somewhere could leave both batteries flat!

I employ the regime of Saturdays, Mondays, Wednesdays and Fridays I use battery 1 and the other days I use battery 2. This ensures each battery gets charged up.

Indeed I had a charging problem in mid channel this year. Switched over to the other battery and it got me home. If I had been running in both mode, I would have had 2 flat batteries and a long tow home.

Tim'mers.

Matt · 15 November 2005, 22:49

Oops. Swifty pretty much said what I meant.

jwalker · 16 November 2005, 00:46

Some info here but be prepaired for a long read.

ashbypower · 16 November 2005, 08:39

Tim'mers.
I beg to differ I’m afraid. I'm not saying there is anything wrong with your setup it just requires a modicum of discipline. I’d much prefer to have both batteries charging and thus fully charged when needed (but blocked from each other) to prevent cross feeding. I would agree that a switch able output is required. All the yachts and Mobos we sail all have this arrangement and have saved a few embarrassing moments e.g. when one battery dropped a couple of cells!! if we had switched to it in anger it would have been as much use as a chocolate fireguard.!! But the prime battery’s charge was being maintained.

Regards

Brian

Nick Thompson · 16 November 2005, 10:19

Quote:

Originally Posted by Swifty

ndeed I had a charging problem in mid channel this year. Switched over to the other battery and it got me home. If I had been running in both mode, I would have had 2 flat batteries and a long tow home.

If it was a charging problem, it wouldn't have made any difference. Two batteries in parallel have the same output capacity in Ah as the same two batteries used one after the other.

If the battery you were using has a shorted cell, then yes, that would have taken the other battery down (unless you had a split charging system)

Matt · 16 November 2005, 10:25

Except a split charging diode has a voltage drop across it so neither battery ends up being fully charged. So then you need to use a remote sensed alternator, which adds more potential failure points. Or, twin alternators. Let's get real, Mr Priddy needs the level of redundancy being considered here.
KISS!

Nick Thompson · 16 November 2005, 10:48

Quote:

Originally Posted by MadMat

Except a split charging diode has a voltage drop across it so neither battery ends up being fully charged.

From Here
'Typical voltage drop @ 120Amp models ~80mVolts (new models).'
Hardly worth worrying about considering
'With common machine sensed alternators, batteries are, in most cases, charged to only 60 - 70% of their capacity, however long the engine is running.' from here but then Mandy Rice-Davis comments might apply.

Quote:

KISS!

Agreed

nugent · 16 November 2005, 11:56

so does 2 x 60 amp battery give you a 120amp feed , curious as i have 2 x 60amp batterys on my optimax and i now know it state's being or recomended 100amp for the engine?

Nick Thompson · 16 November 2005, 12:16

Quote:

Originally Posted by nugent

so does 2 x 60 amp battery give you a 120amp feed

Yes, just make sure the wiring is capable of the higher current.

nugent · 16 November 2005, 12:21

thanks for that i normally start it on both batterys first time in water then switch to one for the rest of the day, and next outing switch to the 2nd battery that way i have allways got a good charge in both,

Matt · 16 November 2005, 12:29

Yes, but look at the price you're paying for the 80mV priviledge.

Quote:

Originally Posted by Nick Thompson

From Here
'Typical voltage drop @ 120Amp models ~80mVolts (new models).'
Hardly worth worrying about considering
'With common machine sensed alternators, batteries are, in most cases, charged to only 60 - 70% of their capacity, however long the engine is running.' from here but then Mandy Rice-Davis comments might apply.

Agreed

Nick Thompson · 16 November 2005, 13:07

Quote:

Originally Posted by MadMat

Yes, but look at the price you're paying for the 80mV priviledge.

Of course it's expensive. It's a 'marine' product, what else do you expect ?.
Although (providing it could handle the environment) a cheap relay would do the same thing.

As to whether it's worth it would depend upon the user, IF you use the boat regularly, can remember which battery was used last & the batteries are in good condition it's probably a waste of money.

Swifty · 16 November 2005, 16:25

Its horses for courses.

You can make it idiot proof, but when something does go wrong it will take an expert to fix it.

Brian,
Quite agree, but a yacht engine is not an outboard.

Nick,
Very true, but the first warning I would have had of a problem would have been too late. 2 flat batteries!

Two 80 Ahr batteries in parrallel does not make a 160Ahr battery. There are losses involved (Sods Law?) and it should be de-rated to about 85% making about a 140Ahr.

And back to the point, if you are going for belt and braces, where would you put the blocking diode? It needs a volume of air to dissipate the heat, so would probably have to go inside the console. Then it would need long cables that are very thick (battery cables) and so on. Like MadMat says K I S S...

Sorry Andrew, seem to have ommitted the obvious. As regards choice of batteries, you have many options, cheapo car battery for about £40, Pukka marine battery for £80+. Differences are numerous but in my experience its cheaper to use car batteries and replace them every two years than to buy the marine versions which are overpriced because they are ... Marine!

Tim'mers.

nugent · 16 November 2005, 16:31

Two 80 Ahr batteries in parrallel does not make a 160Ahr battery. There are losses involved (Sods Law?) and it should be de-rated to about 85% making about a 140Ahr.

An

Tim'mers. [/QUOTE]

so the recomendation of 100amp makes me safe then,,,, as i am runing approx 140a,,
Ohh its all getting stress full

Richard B · 16 November 2005, 16:38

Quote:

Originally Posted by Swifty

Two 80 Ahr batteries in parrallel does not make a 160Ahr battery. There are losses involved (Sods Law?) and it should be de-rated to about 85% making about a 140Ahr.

Exactly where do these losses occur? Lead acid accumulators are very efficient and have a very low internal resistance, hence their suitability for supplying high currents.

Swifty · 16 November 2005, 16:48

Quote:

Originally Posted by nugent

so the recomendation of 100amp makes me safe then,,,, as i am runing approx 140a,,
Ohh its all getting stress full

Looks like you have enough there to crank over a big diesel

My Searider runs on 2x 60 Ahr car batteries. Admittedly my engine doesn't need as much power as an opti.

Tim'mers.