Anyone have a good way of testing 12V deep cycle batteries?

What I was figuring on doing was using a 50watt 12V lightbulb and measuring
voltage with time. The only problem is that this may take a few hours.

I don't think so. Look he www.batteryfaq.org.

====

Charles T. Low
- remove "UN"
www.boatdocking.com
www.ctlow.ca/Trojan26 - my boat

====

"Rick & Linda Bernard" wrote in message
...
Anyone have a good way of testing 12V deep cycle batteries?

What I was figuring on doing was using a 50watt 12V lightbulb and
measuring
voltage with time. The only problem is that this may take a few hours.

On Sat, 24 Jan 2004 05:00:54 -0600, "Rick & Linda Bernard"
wrote:

Anyone have a good way of testing 12V deep cycle batteries?

What I was figuring on doing was using a 50watt 12V lightbulb and measuring
voltage with time. The only problem is that this may take a few hours.


I use a hydrometer, myself. The specific gravity of the cells tells
you what condition they are in. 1.270 is a fully charged lead-acid
battery at 72F. Be sure to get a good hydrometer with a built-in
thermometer and calibration chart because the specific gravity of the
electrolyte is very dependent on temperature.

If you find a cell with gravity lower than the rest, be assured it has
suffered sulphation where the lead sulphate has crystalized and will
soon have a "dead cell", if it's not already.

If the cell has high specific gravity and the battery's voltage
doesn't drop under normal loads, it's fine. Just keep her topped up
with ONLY distilled water.

Of course, AGM batteries you have no way of knowing what the hell is
going on inside the sponges.....

Here's some references for you:
http://www.nwes.com/using_batteries.htm
http://www.thesolar.biz/Measuring_sp...ty_article.htm
http://www.usbr.gov/power/data/fist/...6/3_6_cont.htm
http://www.buchanan1.net/lead_acid.shtml
(people up Nawth need to pay particular attention to the table on
the bottom of this webpage relating to the electrolyte freezing
temperatures as related to cell specific gravity (charge).)
http://www.rpc.com.au/products/efn/e...ries_care.html
http://www.solartech.com/aboutbat.htm

and I think this cool instrument would be a great replacement for the
Link, which I don't think gives you an accurate assessment because the
Link runs on an assumed A-H battery rating and that rating is ONLY
good at a SPECIFIC LOAD CURRENT at a SPECIFIC TEMPERATURE none of you
are running on these batteries. The actual specific gravity is the
ONLY way of actually measuring a battery's condition. This neat
$US110 instrument stuck in one cell will constantly measure that
gravity. Isn't this actually CHEAPER than the Link?!....(c; I know
it's more accurate.
http://www.electrosense.com.au/
Wonder how long it will last in the acid environment?


Larry W4CSC

Is it just me or did the US and UK just capture 1/3
of the world's sweetest oil supply? What idiot wants to
GIVE IT BACK?!!

You need to borrow a load tester. It is just a heavy duty heat sink which
draws current from the battery. If the voltage drops during the test, the
battery is dying.
I have to borrow one to test my setup come
Spring

--
Dennis Gibbons
dkgibbons at optonline dot net
"Rick & Linda Bernard" wrote in message
...
Anyone have a good way of testing 12V deep cycle batteries?

What I was figuring on doing was using a 50watt 12V lightbulb and
measuring
voltage with time. The only problem is that this may take a few hours.

Load testers are good for starting batteries but don't really tell
much for a deep cycle battery.

Doug
s/v Callista

"Dennis Gibbons" wrote in message
et...
You need to borrow a load tester. It is just a heavy duty heat sink which
draws current from the battery. If the voltage drops during the test, the
battery is dying.
I have to borrow one to test my setup come
Spring

--
Dennis Gibbons
dkgibbons at optonline dot net
"Rick & Linda Bernard" wrote in message
...
Anyone have a good way of testing 12V deep cycle batteries?

What I was figuring on doing was using a 50watt 12V lightbulb and
measuring
voltage with time. The only problem is that this may take a few hours.

"Doug Dotson" wrote in message
...
Load testers are good for starting batteries but don't really tell much
for a deep cycle battery.
Doug - s/v Callista

====

Doug,

Any idea why is this?

Is it possible to have good sg and still fail a load test? I.e., is a load
test more sensitive than sg? (I presume that sg is more specific than
measuring voltage?) Does it go like that, in terms of accuracy?:

voltage
specific gravity
load testing???

Will an appliance such as a commerically bought load tester be more or less
accurate than doing a long, slow test oneself, such as by leaving lights on?

(And, one other poster mentioned testing down to 50% charge as more
convenient than testing to 0% charge - isn't it also true that testing to 0%
charge will ruin the battery?)

Charles

(So many questions, such limited memory capacity...)

====

Charles T. Low
- remove "UN"
www.boatdocking.com
www.ctlow.ca/Trojan26 - my boat

====

"Charles T. Low" wrote in message
...
"Doug Dotson" wrote in message
...
Load testers are good for starting batteries but don't really tell much
for a deep cycle battery.
Doug - s/v Callista

====

Doug,

Any idea why is this?

Is it possible to have good sg and still fail a load test? I.e., is a load
test more sensitive than sg? (I presume that sg is more specific than
measuring voltage?) Does it go like that, in terms of accuracy?:

The discharge time of a deep cycle battery is influenced by many
things other than SG. The condition of the plates etc all come into
play. While one may be able to draw heavy current for a brief
period that does not necessarily translate into good low power
performance. A long term low current test tells the actual story
since it is how the battery is being used in normal use. The SG
gives the state of charge from a theoretical sense as does the voltage.

voltage
specific gravity
load testing???

Will an appliance such as a commerically bought load tester be more or
less
accurate than doing a long, slow test oneself, such as by leaving lights
on?

A load tester (at least the ones I have seen) can't tell what the
capacity of the battery is. They just give a general idea that the
battery is chemically and physically sound. I built a system a few
years ago that would discharge a battery at a specified rate and then
automatically recharge it all while monitoring. It graphically showed
the capacity of the battery. It was also useful for reconditioning and
breaking in batteries.

(And, one other poster mentioned testing down to 50% charge as more
convenient than testing to 0% charge - isn't it also true that testing to
0%
charge will ruin the battery?)

0% charge and running it all the way down are not the same. 0% discharge
is usually considered to be 10.5v. That is why I figure 50% is good enough.
50% is generally considered the lowest a battery should be discharged in
normal use so doing so will tell what the useful capacity is.

Charles

(So many questions, such limited memory capacity...)

====

Charles T. Low
- remove "UN"
www.boatdocking.com
www.ctlow.ca/Trojan26 - my boat

====

Doug,

Thanks, very helpful.

So, does this seem valid to you? - An accurate voltage reading is a good
indicator of a battery's condition, but specific gravity is better, and a
slow load test (to 50%) is the best? Or are they testing different things,
all of which are important? Could it do well on a load test without good
voltage or sg's?

And, what use is a commercial load tester, then? Why do they make them? Is
it better than an sg but not as good as a slow load test?

Thanks again. Charles

P.S. I corrected the spelling of "betteries" - couldn't take it any more!

====

Charles T. Low
- remove "UN"
www.boatdocking.com
www.ctlow.ca/Trojan26 - my boat

====

"Doug Dotson" wrote in message
...
The discharge time of a deep cycle battery is influenced by many
things other than SG. The condition of the plates etc all come into
play. While one may be able to draw heavy current for a brief
period that does not necessarily translate into good low power
performance. A long term low current test tells the actual story
since it is how the battery is being used in normal use. The SG
gives the state of charge from a theoretical sense as does the voltage.

Doug,

Thanks, very helpful.

So, does this seem valid to you? - An accurate voltage reading is a good
indicator of a battery's condition, but specific gravity is better, and a
slow load test (to 50%) is the best? Or are they testing different things,
all of which are important? Could it do well on a load test without good
voltage or sg's?

And, what use is a commercial load tester, then? Why do they make them? Is
it better than an sg but not as good as a slow load test?

Thanks again. Charles

P.S. I corrected the spelling of "betteries" - couldn't take it any more!

====

Charles T. Low
- remove "UN"
www.boatdocking.com
www.ctlow.ca/Trojan26 - my boat

====

"Doug Dotson" wrote in message
...
The discharge time of a deep cycle battery is influenced by many
things other than SG. The condition of the plates etc all come into
play. While one may be able to draw heavy current for a brief
period that does not necessarily translate into good low power
performance. A long term low current test tells the actual story
since it is how the battery is being used in normal use. The SG
gives the state of charge from a theoretical sense as does the voltage.

"Charles T. Low" wrote in message
...
"Doug Dotson" wrote in message
...
Load testers are good for starting batteries but don't really tell much
for a deep cycle battery.
Doug - s/v Callista

====

Doug,

Any idea why is this?

Is it possible to have good sg and still fail a load test? I.e., is a load
test more sensitive than sg? (I presume that sg is more specific than
measuring voltage?) Does it go like that, in terms of accuracy?:

The discharge time of a deep cycle battery is influenced by many
things other than SG. The condition of the plates etc all come into
play. While one may be able to draw heavy current for a brief
period that does not necessarily translate into good low power
performance. A long term low current test tells the actual story
since it is how the battery is being used in normal use. The SG
gives the state of charge from a theoretical sense as does the voltage.

voltage
specific gravity
load testing???

Will an appliance such as a commerically bought load tester be more or
less
accurate than doing a long, slow test oneself, such as by leaving lights
on?

A load tester (at least the ones I have seen) can't tell what the
capacity of the battery is. They just give a general idea that the
battery is chemically and physically sound. I built a system a few
years ago that would discharge a battery at a specified rate and then
automatically recharge it all while monitoring. It graphically showed
the capacity of the battery. It was also useful for reconditioning and
breaking in batteries.

(And, one other poster mentioned testing down to 50% charge as more
convenient than testing to 0% charge - isn't it also true that testing to
0%
charge will ruin the battery?)

0% charge and running it all the way down are not the same. 0% discharge
is usually considered to be 10.5v. That is why I figure 50% is good enough.
50% is generally considered the lowest a battery should be discharged in
normal use so doing so will tell what the useful capacity is.

Charles

(So many questions, such limited memory capacity...)

====

Charles T. Low
- remove "UN"
www.boatdocking.com
www.ctlow.ca/Trojan26 - my boat

====