Gel cel battery question

[corpuscle68]

Hello!
I used a 12V 100aH AGM battery to power the sound system on my quad cycle last year. Worked like a charm. We plan to use a solar trickle charger this year.
Well, I didn't keep it hooked up to a trickle charger since last burn! Now it won't take a full charge.
The manufacturer said it never will, and furthermore it might not take that many more charges at all, or even take one charge if it is drained.
I'm running a test right now, but wanted to query any burners who have battery knowledge.
Better to get a new one, or is there a reasonable chance this one will work this burn?

Thanks

Rolf

[phil]

I'd guess you've ruined it by not maintaining the charge. See "How to wreck your battery" at
http://www.cieux.com/bm/batteryWreck.html
for more information on battery maintenance and what happens when batteries are totally discharged.

Executive summary:

People who use their batteries infrequently and then use them to full discharge (and beyond) will damage their batteries and shorten the battery's life substantially from any advertised life. I have in mind people who go camping once a year for a week. They don't recharge their batteries until a day or two before they leave, drain the batteries dead during the week, then bring the batteries home and put them away discharged until next year. If the batteries are not critical to safety or health, this is not a problem when they fail early and often.

[corpuscle68]

Phil:
The battery was not run dead at the end of last burn. I'd say it went into its year long sojurn with a near full charge.

Rolf

[phil]

Hi, Rolf - read the article.

[corpuscle68]

Phil:
The article is summed up by your cut and paste. It comments on a battery going into its year long sojurn drawn all the way down.
When I attached mine to the charger today it read immediately at 60%. Then it charged up to 79% and plateaued.

Rolf

[gyre]

Some batteries are tougher than others.
It is a good idea to have spares.
I have had better luck using high end wet cells for recharging than batteries made for it.
I am leaning toward using some optima deep cycles.

How much draw are you pulling?
Gel cells seem to do better with low draw but are often put in high draw use due to stability.

You've tested it running it down?
Then you'll know exactly what to expect.

I have an optima that has been raced and run totally flat.
It still takes a full charge but will no longer maintain it for a long time.
After being fully drained, it took a full charge in two hours on a small charger.
I like that.

Do you have to use a gel?

[skibear]

Wet cell lead Acid batteries(car/marine) will totally discharge in a month
or two then irreversable sulphation damage starts.

They should be kept on trickle charge or recharged periodically.
I don't think think gel cell (they're also lead acid) batteries are
much different.

At the office they would take 30AH gel cell packs into the field
and return and leave them discharged. They wouldn't listen to me
so every year or two they were replacing most the gel cells.

Do a discharge test & if they have more than half their life left
(unlikely) then you should be good.

hth

[phil]

The article is summed up by your cut and paste. It comments on a battery going into its year long sojurn drawn all the way down.

My apologies, Rolf. I have completely misunderstood your original post. I had thought that your comment

Well, I didn't keep it hooked up to a trickle charger since last burn! Now it won't take a full charge.

was addressed in the article here:

AGMs seem more efficient at uses where they are deeply discharged but only infrequently, being kept on a floating charge. *** It is better to keep a sealed lead-acid battery on a floating charge than to allow it to fully discharge by sitting a year between uses. The next best option is to fully recharge the battery monthly.

which tells the proper way to store a battery for a year, whether it is fully charged or discharged at the time it is put into storage. I had thought that this would give you a way to judge whether you had properly stored the battery for a year.

I had thought your comment

The manufacturer said it never will, and furthermore it might not take that many more charges at all, or even take one charge if it is drained.

was covered here:

You can estimate your battery's current condition by fully charging it, measuring the voltage (it should be over 13.2V), and putting a known draw on the battery while keeping the volt meter connected. Let's say that you have an automobile headlamp that you know draws 4 amps. If you have a 12 amp-hour battery and fully charge it, connect the lamp and volt meter to the battery, turn the lamp on, and note the time. When you notice the light fading, start watching the meter and note the time the voltmeter reads 10.5V. Let's say it took 2 hours. For 12 amp-hour battery, the battery's rated capacity at a draw of four amps is 3 hours, so your battery's capacity is now 2/3 its rated capacity. Its capacity will continue to degrade until you find the battery useless and recycle it.

which tells you how to test your battery to confirm the manufacturer's statement that the battery is wrecked.

Your query

Better to get a new one, or is there a reasonable chance this one will work this burn?

would then have been answered, I thought, by the test mentioned in the article. The article also mentions which of the three lead-acid battery types is better suited to your use, so that when you buy a new one, you could consider which of the three to purchase.

My sincere apology for my confusion and misunderstanding.[/quote]

[corpuscle68]

Well here is what the test showed, from the charger that has a % charge meter.
The battery started with roughly 60%, after being untouched since last burn. (Plausible? Could the charger be wrong?)
Charging led to a plateau of 79% charge.
I then ran the amp, a Toshiba TP-873 85W x 4 Channel for six hours at a moderate volume.
Then the charger read 49%.

Watts = Volts * Amps
85 / 12 = 7.08

Assuming a 100aH battery in good shape, 30% of the charge should be 30 amp-hours.

6 * 7 = 42.

So likely I was not using the full 85W, since it wasn't at full volume.
Or the % meter on the charger is not reflecting reality.

An overnight charge now has brought it up to 90%.
If I trust the charger, then I think this battery has a reasonable life left, and is unlikely to die on the playa. It is taking an increasing charge, and powered the sound system for honestly more hours than I ever played it straight last year.

Thoughts from battery gurus?

[Token]

Your battery is fine. Do a couple more charge/discharge cycles and you will be fine.

Alternatively, go to Pep Boys or similar and get one of those computer controlled chargers that have a battery reconditioning program. Run that.

[skibear]

I don't claim to be any kind of guru- just a retired Electrical engineer!
The math is a bit puzzling. Did you actually measure the 7.08 amps
or is this an assumption that a 85 W amplifier running at a loud level
was running at 85 Watts. Music peaks and drops a lot unless it is
steady loud techno music. I'd bet average current was a lot less.

Best to measure current directly with a DC Ammeter and run the test
until the voltage drops to 10 volts. Then calculate AmpHours. Then
immediatley recharge the battery.


Percent of charge ??? Is this a gelcell charger? Or a car battery
charger. It probably calculates charge from terminal voltage which
can vary with ambient temperature (if not corrected) and battery
chemistry and I'm not sure I'd trust it.

If I trust the charger, then I think this battery has a reasonable life left, and is unlikely to die on the playa. It is taking an increasing charge, and powered the sound system for honestly more hours than I ever played it straight last year.

Thoughts from battery gurus?

That's the only test that matters. If it works as long as you need it
for you are fine. Just have it fully charged before use. Playa conditions
don't affect this type of battery any significant amount vs use at home.

Do you have a camp AC generator to recharge the battery after 6 hours
if you need it again.
hth

[gyre]

What are the specs on the amp?
Watts rms at .? % distortion x 4 at ?? volts.
You may have a maximum power consumption listed as well.
I can't find anything on that useless Toshiba website.

Are there no designers with sense doing websites out there?

[corpuscle68]

don't claim to be any kind of guru- just a retired Electrical engineer!
The math is a bit puzzling. Did you actually measure the 7.08 amps
or is this an assumption that a 85 W amplifier running at a loud level
was running at 85 Watts. Music peaks and drops a lot unless it is
steady loud techno music. I'd bet average current was a lot less.

- Purely dividing the 85 watts listed by the 12 volts of the system. I picked up the amp, attached to a trunk type speaker set up, off of Craigslist. It makes nice noise, but I don't have any manuals. When I google the model most of the results are offers to sell the owners manual! I have not yet used a DC Ammeter. I'll see what I can do!

Best to measure current directly with a DC Ammeter and run the test
until the voltage drops to 10 volts. Then calculate AmpHours. Then
immediatley recharge the battery.


Percent of charge ??? Is this a gelcell charger? Or a car battery
charger. It probably calculates charge from terminal voltage which
can vary with ambient temperature (if not corrected) and battery
chemistry and I'm not sure I'd trust it.

- It's a charger from Wal Mart. It says it can handle regular batteries or gel cels, and offers you a 2A or 30/10A battery charger option, and a 60A starter option. You can tell it to give you a % charge read out, among other options.

[gyre]

Are you running all four amps?
4 times 85 watts?
If that is the rating in big letters on the amp, it may be wildly off.
Is there any info in small letters?
If I were you, I would at least call Toshiba and get real specs.

Signal to noise
Power in rms watts at 4 or 8 ohms at a low distortion level-under 1 % at 12 volts.
Should be under .1 % really.
And don't forget the voltage for the rating.
Many people over rate their amps with a high voltage for the specs.
A typical 25 watt is actually 8 watts usable.
Also the power consumption going in and the rating for a fuse going to the amp.

If the test you ran was at a sound level you need and the duration was acceptable to you, then you have your answer.