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› sealed lead acid batterys Help??
10-12-2005 05:36 PM  13 years agoPost 1


west yorkshire,England

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Hi just a quick question,
ive just brought home a sealed 12v 37amp battery for the field etc...
am i able to charge this on a normal car battery charger



10-12-2005 05:46 PM  13 years agoPost 2


Charleston, SC

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That's how I charge mine.

I have 7ah, 11ah, and 22ah, and use my Vector automotive charger on all of them. Their characteristics are pretty much the same as a regular open cell automotive/motorcycle/garden tractor batteries.


10-12-2005 05:47 PM  13 years agoPost 3

rrElite Veteran

Hurst Texas

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Yes a car or motorcycle charger will work fine. Charge till the voltage shows 13.0 to 13.1 after sitting off charger a few minutes.

Wildcat Fuels

10-12-2005 06:49 PM  13 years agoPost 4

rrKey Veteran

Rochester, NY

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I've read (though I can't seem to find the source now) that the charge voltage is lower on a gel-type battery, thus using a wet cell, or "car" charger can overcharge them, causing damage over time.

You will also want to charge them as slowly as possible to prevent the gel electrolyte from forming gas pockets.

EDIT: Apparently it's the charge rate that's most important, as the gel batteries are more sensitive to overcharging.

The sky is our canvas

10-13-2005 12:21 AM  13 years agoPost 5

rrKey Veteran


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Charge rate is imortant. If I use my auto charger on my field batteries, the acid will burn off in a few hours. I believe because it is charging too fast. The little 1 amp or 500mah charger does fine.


10-13-2005 01:58 AM  13 years agoPost 6

rrElite Veteran

sacramento, ca, u.s.

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i used to charge my SLAs with a car charger on 2amp setting. but, they'd only last about 1 season.

i've since started using on of these that charges at 1 amp. i put a jack on my fieldbox and plug it right into this. keeps it peak charged all the time. jacks/wiring sold separately--all you get when you order is the wall wart

if it ain't broke, break it.

10-15-2005 02:26 PM  13 years agoPost 7


Garnet Valley, Pa.

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I just ordered a Lifeline AGM (absorbed glass mat) battery model GPL-U1T from Defender.

12 volts, 33 amp hours, 275 cranking amps, 7.71" L x 5.18" W x 6.89" H.

I'm using it to run my Graupner Duo 30 out at the field.
$98 shipped.
You can lay these batteries on there side with no ill effects.

This setup... Graupner field charger, AGM battery, allows me to use the Graupner lead acid program trickle charge with adjustable milliamp hooked to a 12v power supply, to charge this field battery. It's got a full program for charging lead acid car batteries including automatically going into a programmable trickle level. The Graupner manual states "automatically reduces the final charge voltage to 2.2 to 2.3v per cell which effectively prevents excessive gassing of the battery even if it is left on charge for a fairly long time."
"This program is designed for charging and discharging lead-sulphuric acid and lead-gel batteries"

The Graupner allows me to control maximium permissable charge current. "The charger constantly monitors the battery's voltage, thereby limits the current in order to prevent excessive gassing of the battery."

"Caution: Lead Acid batteries cannot and must not be fast charged"

"Lifeline AGM (absorbed glass mat) batteries, originally developed for Military Aircraft, are the premium sealed, maintenance free deep cycle battery available. Hand made with a sturdy non marking case, they are widely used as original equipment by such companies as; Hinckley Company,Alden Yachts, Cabo Yachts, Island Packet Yachts, Sabre Corporation and others. Lifeline AGM batteries are more shock tolerant and have the fastest recharge rates due to their low resistance and aircraft class construction and no current limitations with voltage regulated charging.They offer the best charge retention as well as twice as many discharge cycles as the leading gel battery. Other features include; lowest discharge rates, the ability to fully recharge after 30 days of full discharge, non spillable user safe construction and a one year unconditional, 60 month prorated warranty thereafter making Lifeline AGM batteries the highest quality AGM option on the market."

Wolves don't lose sleep over the opinions of sheep

10-15-2005 07:11 PM  13 years agoPost 8

rrKey Veteran

Toronto, Canada

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The recommended charge voltage for lead gel batteries is 13.5 - 13.8vdc.

I lost my infamous tag line.

10-16-2005 01:40 AM  13 years agoPost 9



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Use caution if charging sealed lead acid batteries with chargers designed for open cell (unsealed) batteries as it is easy to ruin a sealed bettery this way.

There are two potential problems: the charge rate and overcharging.

All lead acid batteries produce some hydrogen and oxygen gases when charged, due to electrolysis of the water diluting the acid. At low charge rates, only very small amounts of gas are produced and they recombine in the battery and no harm is done. At high charge rates, the battery will "gas" much more. In an open cell battery, the gas escapes, and gradually the electrolite level drops. This is not too much of a problem as the battery can be periodically topped up with distilled water. In a sealed battery, if gas is produced, the pressure inside the battery rises. If the pressure becomes too great, a safety valve opens, allowing the excess gas to escape, preventing the battery from exploding. However, the loss of the gases depletes the electrolite and, as it cannot be topped up, reduces the battery performance. If the situation continues, the life of the battery will be very short.

A simillar situation occurs when the battery is fully charged. Once no more charge can be accepted, any continuing charge current simply electrolizes the water and produces gas. This is why car batteries bubble when fully charged.

So to answer Tomi2004's question:
It is unlikely that your 37Ah battery is going to be charged too fast by the average car charger when the battery is in a discharged condition. However, unless the charger has some sort of voltage sensing so that it can reduce and then terminate the current as the battery becomes charged (and most cheap car ones don't), there is a danger of overcharging, causing the battery to vent. If you monitor the battery voltage and ensure that you disconnect when it reaches 14.0V, you should be OK, but this is not ideal. A charger designed for sealed batteries would be much better. If you want to fast charge, it should be a "three stage" charger (fast, topping, then float). Look at:

for more information on three stage charging.

If your field charger has a setting for lead acids, you could buy a mains adapter and use that.

Hope this helps


Logo14 Vbar, Logo500 CSM flybarless, Trex 600 CSM flybarless, 3DMP, Logo10, Lipoly, Mini T, .......

10-16-2005 10:48 PM  13 years agoPost 10


South Africa, Cape Town

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Let's assume you are talking a 12 V battery.
A SLA, or "Gel" battery as it's also known, is a voltage driven thingy, almost like LiPo's just a heck lot more forgiving when abused.
To charge a flat or semi flat battery, you need to apply 14.2 to 14.8 volt across the terminals, same as a car battery.
Unlike a car battery, you then need to limit the current at this time, since the jelly goo inside don't like to bubble too profusely.
Most batteries will have these ratings printed on the side somewhere.
If the battery is almost full, or full, and you want to trickle charge it, then you need to reduce the voltage to 13.6 to 13.8 V.

Your normal car charger is a rather crude device, if you insist on using it on your SLA/Gel, then wire an indicator bulb from your car in series with either one of the charging leads, this will act as a crude current limiter.
(Actually, a lightbulb can be a very simple, but accurate current limiter, but to pick the correct one requires an involved explanation)

If you have a multimeter, check all the above mentioned things.

The mistake that most people make with these batteries, is watching the current.
A fully charged battery won't draw any significant current at 14.2 to 14.8 volt, but it will be ruined if left like that for more than a few days.

An aside, I don't think the Swallow chargers can really charge a 12 V Gel battery :-(


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