Ian Pearson
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| posted on 30/10/06 at 10:59 AM |
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Deep Cycle Batteries
The starter motor on my Land Cruiser is 24v, and so I've two batteries. They are starting to play up, and so I'm looking for replacements.
Are deep cycle batteries worth looking at? I'm not planning to fit an inverter, so all I'm looking for is reliability and longevity. Any
advice from any of you who are battery wise?
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pewe
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| posted on 30/10/06 at 05:16 PM |
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Ian, I'm no expert but to me deep cycle/leisure batteries do not have the ability to consistently provide the instant power needed for engine
starts, especially diesel engines.
They are designed for the slow release required for boats and caravans for lighting and other ancilliary items.
Someone else may be able to confirm this. Cheers, Pewe.
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Syd Bridge
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| posted on 30/10/06 at 06:18 PM |
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Deep cycle are used on fork lifts, commonly called traction batteries. Also can be used on boats and vans.
They are called 'deep cycle', because they can be run down very low, and be charged back to top voltage over and over again, and not
suffer like ordinary car batteries would.
For starting, they give a more steady voltage and better cranking power. Diesels give them no probs at all.
I've trusted my life to them in yachts far too many times, to not trust them in a land based vehicle.
Cheers,
Syd. 
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MikeRJ
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| posted on 30/10/06 at 11:15 PM |
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A deep cycle battery will typicaly be capable of delivering around 20% less cranking current than an equivalently sized car battery.
The reason for this is the plates are made from a solid lead rather than the sponge that normal car baterries use. This helps prevent them
sulphating, but gives less plate area and hence less current capability (due to higher internal resistance).
[Edited on 30/10/06 by MikeRJ]
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Syd Bridge
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| posted on 31/10/06 at 12:24 PM |
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You better go tell that to all the boat owners in the local marina/moorings, who rely on them to start their diesels after sitting for weeks at a
time.
Turn up, put the key in, and away it goes, time after time.
Syd.
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Bob C
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| posted on 31/10/06 at 01:20 PM |
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Mike's perfectly correct - yachts have 'bigger' batteries 'cos it's supplying all electrics, it's not sized for
cranking.
Bob
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Syd Bridge
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| posted on 31/10/06 at 05:35 PM |
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I don't know where you lot are getting your info, but 'traction' batteries are designed to give very high instantaneous
currents, and prolonged high current.
Change the label and they are 'extreme duty marine' batteries.
I am currently involved in two electric car projects, using deep cycle traction batteries. Try 400 amps continuous!!!!! If your starter is drawing
more than that, you've got more problems than battery suitability.
Ian, if you can get deep cycle batteries for the 'right price', then get them. They won't let you down.
Better still, talk to a battery maker, and see what they say. It'll be the difference between a commercial quality item, or domestic.
Cheers,
Syd.
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Ian Pearson
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| posted on 31/10/06 at 05:45 PM |
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Thanks All.
Batteries died totally, got out voted for cost reasons, and had to buy normal ones!
Regards, Ian.
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MikeRJ
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| posted on 31/10/06 at 08:37 PM |
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Traction batteries are simply one type of deep cycle battery, as are marine and leisure batteries. In fact marine batteries are not usualy true deep
cycle, most of them are not designed to be discharged more than about 50% on a regular basis.
The fact remains that size for size, a true deep cycle battery has higher internal resistance than a conventional "starting" battery
which limits it's cold cranking amps. Note that I have not said that a deep cycle battery is unsuitable for car applications, but to get the
equivalent CCA that battery will need to be approximately 20% larger.
I did quite a bit of research into deep cycle baterries at my last work place, but just to confirm this I've had a quick Google:
http://www.mpoweruk.com/leadacid.htm
http://www.windsun.com/Batteries/Battery_FAQ.htm
http://en.wikipedia.org/wiki/Lead-acid_batteries
I had to do quite a bit of research on deep cycle batteries for my last job,
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