Charge gel cell with car charger?

A friend has a battery powered Ryobi lawn trimmer ("weed whacker") which doesn't work. The 12vdc wall wart puts out only ~ 12.4v.
I charged the lead-acid gel cell using a car charger. The charge rate (selectable) was 0.5A. Afterward the trimmer seemed to work as new.
Can the car charger be used to charge this battery? He can install a timer to limit charge time if that's something required.
Thanks.
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On 02/24/2013 12:06 AM, Mike Cook wrote:

You answered your own question. As long as the battery doesn't heat up on a big charge you're probably OK. Trickle chargers can do more harm than good. I'd find a smartcharger with a "lead-acid" setting.
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"dave"

** SLA or "gel cells" are prone to gassing when overcharged.
The pressure builds up inside until something gives - then you have bits of battery and acid all over the place.
Voltage & current limited charging is the only safe and sensible way.
... Phil
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On 02/24/2013 05:14 AM, Phil Allison wrote:

They have vents.
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Which are NOT meant for overcharge relief.
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On 02/24/2013 05:37 AM, SoothSayer wrote:

I didn't say they were. I was speaking to the "bits of battery and acid" prediction above.
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dave wrote:

I've seen the results of several car batteries exploding. Maybe your head should be under the hood when one blows.
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On 02/25/2013 10:54 AM, Michael A. Terrell wrote:

Why is everyone so rude around here?
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wrote:

Why are you here?
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On 02/25/2013 05:07 PM, snipped-for-privacy@attt.bizz wrote:

I am here for entertainment, mainly. most of the substantive stuff is over my head, but the lead-acid battery is on the FCC exams you take for an advanced license, plus I used to maintain a fleet of trucks at a construction company, where I also serviced 2-way radios and 5 mW surveyor lasers.
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wrote:

Ah Ha!

Oohhh! I'm impressed. You took a *real* FCC license exam. Did you pass?

So you know it all. Great!
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snipped-for-privacy@attt.bizz wrote:

The ham + CHEESE test! ;-)

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I specifically stated that I did not. You may be a good engineer but you are a shitty reader.
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wrote:

I can't help it if you can't make up your mind.
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dave wrote:

Everyone is quite an exaggeration, but this isn't the kiddy's sandbox. If you want to be spoon fed, go to news:sci.electronics.basics
This group is intended as a place to kick around design ideas, not baby-sit beginners. If you think this place is rude, you'd never survive a design review.
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I wasn't saying you said something wrong. I was merely iterating that those vents are not for charging pressure relief, per se.
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"dave"

** Most do not - eg:
http://cdn-products.austinkayak.com/p_8037_700.jpg
An acquaintance had a 12V gell battery like the one pictured explode violently while doing just what the OP here is contemplating. He was sleeping nearby at the time an got one HELL of a scare !!!!
Makers all warn against using unregulated ( ie raw, rectified AC ) chargers with gell or SLA batteries.
BTW:
Makers also warn against shorting the battery and often quote a max safe discharge current.
The penalty for ignoring this advice is a dead battery when the deliberate (weak link ) fuse inside goes open.
.... Phil
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On 02/25/2013 08:27 PM, Phil Allison wrote:

"An absorbed glass mat battery has the electrolyte absorbed in a fiber-glass mat separator. A gel cell has the electrolyte mixed with silica dust to form an immobilized gel.
While these batteries are often colloquially called sealed lead?acid batteries,
they always include a safety pressure relief valve.
As opposed to vented (also called flooded) batteries, a VRLA cannot spill its electrolyte if it is inverted." -https://en.wikipedia.org/wiki/VRLA_battery
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For NORMAL battery utilization. NOT a vent for charging pressure relief.. The device and or person doing the charging has to keep the process below any overt gassing level.
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On 02/26/2013 06:52 AM, SoothSayer wrote:

OK. My only other point was that 12 Vdc nominal is never 12 Vdc, except when the battery is severely discharged. A lot of mobile equipment will not work properly on 12 Vdc.
"A car battery is considered charged at 12.4 volts or higher. It is considered discharged when it's at 12.39 volts or less."
-http://www.autobatteries.com/basics/voltage1.asp
You are allowed to nag precise, and I am too.
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