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Deep cycle battery capacity - how to know?

J

Just Allan

Jan 1, 1970
0
Someone I know bought a 12V deep-cycle battery for their vehicle, for
camping trips and they asked me a question...

I've often read comments like, "If you regularly discharge a
deep-cycle battery only 40%, it will have a longer life than if you
discharge it 60%."

Well... How do you tell how far you've discharged it? (How do you
know what percentage capacity remains?)

Thanks...

Allan.
 
R

Rheilly Phoull

Jan 1, 1970
0
One day Just Allan got dressed and committed to text
Someone I know bought a 12V deep-cycle battery for their vehicle, for
camping trips and they asked me a question...

I've often read comments like, "If you regularly discharge a
deep-cycle battery only 40%, it will have a longer life than if you
discharge it 60%."

Well... How do you tell how far you've discharged it? (How do you
know what percentage capacity remains?)

Thanks...

Allan.

One method is to measure the volts under load with an accurate voltmeter
such as a digital volt-ohmeter. Most manufactures say that if it drops below
10.5v then deteriation (SP?) starts to occur. Personally I stop it at 11v to
be on the safe side. There should be graphs from the maker somewhere to
judge the remaing capacity. Google for Bill Bowdens battery faq.
 
B

budgie

Jan 1, 1970
0
Someone I know bought a 12V deep-cycle battery for their vehicle, for
camping trips and they asked me a question...

I've often read comments like, "If you regularly discharge a
deep-cycle battery only 40%, it will have a longer life than if you
discharge it 60%."

Well... How do you tell how far you've discharged it? (How do you
know what percentage capacity remains?)

unless it's a sealed or gel electrolyte type, use the classical method -
electrolyte SG and temp, and look up a chart or do some simple maths.
 
D

David L. Jones

Jan 1, 1970
0
Just said:
Someone I know bought a 12V deep-cycle battery for their vehicle, for
camping trips and they asked me a question...

I've often read comments like, "If you regularly discharge a
deep-cycle battery only 40%, it will have a longer life than if you
discharge it 60%."

Well... How do you tell how far you've discharged it? (How do you
know what percentage capacity remains?)

Thanks...

Allan.

A intelligent charge meter would be the hi-tech way to do it. They can
track how much charge goes into the battery and how much comes out,
among other things.
Don't know if you can get them for car batteries though, but chips are
available for LiIon battery packs etc.

Dave :)
 
Q

quietguy

Jan 1, 1970
0
Gee Roger - the rest of us squirt the 'acid' back into the cell after taking a
reading - I sincerely hope you do not just put it down the drain etc - that is
not a good thing to do

David
 
R

Ross Herbert

Jan 1, 1970
0
A intelligent charge meter would be the hi-tech way to do it. They can
track how much charge goes into the battery and how much comes out,
among other things.
Don't know if you can get them for car batteries though, but chips are
available for LiIon battery packs etc.

Dave :)

One intelligent tester for all types of car batteries is the Cadex
CA-12. It looks and sounds expensive though....
http://www.cadex.com/prod_testers_ca12.asp
 
K

Ken Taylor

Jan 1, 1970
0
Roger Lascelles said:
message

I reckon you'd only get a couple of readings that way !

As part of my job I sometimes do a hydrometer reading on the same battery
every few days, over a number of charge, settle, discharge cycles,
recording
battery characteristics. I notice that the electrolyte level gradually
drops, eventually requiring top-up. If you think about it, you always
lose
a drop here and there, and you have to wet the hydrometer. So hydrometer
readings are not much good long term - say every day when you want to
check
charge level on a deep cycle installation.

I have noticed that the simple act of adding distilled water to a battery
changes the battery characteristics to the extent that I can't use it any
longer for characteristics measurements, and the battery takes a long time
to recover.

On that basis, I would not want to spoil an expensive deep cycle battery
by
juggling with acid - all too clever - I would rather leave the sulphate
ions inside that battery to begin with.

Roger Lascelles

If it's a good quality deep-discharge battery then the manufacturer will
provide a table giving open-circuit voltage vs. capacity and specific
gravity, with a temperature compensation table.

Cheers.

Ken
 
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