Charge Rate for a 12v 7Ah Battery - RC Groups
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Jun 15, 2010, 09:10 PM
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dlt2859's Avatar
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Charge Rate for a 12v 7Ah Battery


Gang,
What is the max Ah charge rate for a Hanger 9 12V 7Ah battery?
Thanks,
Don
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Jun 15, 2010, 09:19 PM
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Gary Cee's Avatar
A average .7 (700 mA) amp rate for 10 to 12 hours should be fairly safe. There are automatic chargers that work well for that size battery. You may use a faster rate but the rate given is pretty common. Lead-acid type cells generally charge satisfactorily with a fixed voltage source. The initial current may sart out quite high then taper off as the battery voltage reaches equilibrium with the charge voltage.

Lead acid cell should not become deeply discharged and should be charged as soon as possible after discharge. There is no harm in topping off after use even if not fully discharged. A little research and experience will allow voltage readings to help you determine the actual state of charge.
Jun 15, 2010, 10:17 PM
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dlt2859's Avatar
Quote:
Originally Posted by Gary Cee
A average .7 (700 mA) amp rate for 10 to 12 hours should be fairly safe. There are automatic chargers that work well for that size battery. You may use a faster rate but the rate given is pretty common. Lead-acid type cells generally charge satisfactorily with a fixed voltage source. The initial current may sart out quite high then taper off as the battery voltage reaches equilibrium with the charge voltage.

Lead acid cell should not become deeply discharged and should be charged as soon as possible after discharge. There is no harm in topping off after use even if not fully discharged. A little research and experience will allow voltage readings to help you determine the actual state of charge.

Gary,
Thanks for the quick response!
Don
Jun 15, 2010, 10:38 PM
Registered User
Also, there are many good chargers on the market now to charge sealed AGM batteries. You might try looking for one at a good motorcycle shop. The good ones are "intelligent" and do things to keep your battery in top shape and prevent or reverse sulphation, etc. and can be connected indefinitely without harm so you're battery is always ready to go.
Jun 15, 2010, 10:50 PM
Registered User
I use the Battery Tender Jr for my SLA flight box battery.

http://batterytender.com/battery-ten...-at-0-75a.html
Jun 16, 2010, 09:55 PM
Registered User
Been using the same Battery Tender Jr to maintain my 2 starter box cells. Changing to a float type charger has more than doubled the life I had been getting from these type cells.
Jun 17, 2010, 02:46 AM
Registered User
Rule of thumb is to charge SLA batteries between 1/10 of their capacity to 1/4, so for this battery between 700ma to 1.75A.

Normally the charge rate and time is printed on the battery, maybe under a sticker?
Aug 24, 2010, 03:17 AM
Registered User
Quote:
Originally Posted by dlt2859
Gang,
What is the max Ah charge rate for a Hanger 9 12V 7Ah battery?
Thanks,
Don
Don as a rule 1/10 of the batterys capacity is the rule of thumb eg: 7Ah or 7000mah = 700mah but 1amp is ok just dont leave on for too long.
I always check the Battery for warmth as if it's making heat then it's charging too fast or for too long OK..cheers
Aug 24, 2010, 07:38 AM
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flypaper 2's Avatar
Most of the lipo chargers today will charge just about anything. I use the Accucell 6 with no problems. PB setting is for lead acid. It charges it properly and shuts off when done.

Gord.
Aug 25, 2010, 10:53 AM
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dlt2859's Avatar
Quote:
Originally Posted by jcinauz
Don as a rule 1/10 of the batterys capacity is the rule of thumb eg: 7Ah or 7000mah = 700mah but 1amp is ok just dont leave on for too long.
I always check the Battery for warmth as if it's making heat then it's charging too fast or for too long OK..cheers
Thanks,

That's just the conformation I was looking for!!

Don
Aug 25, 2010, 02:37 PM
Registered User
Especially on sealed (no maintenance ) cells, limit the charge rate to 0.1C else you risk ruining the battery. Be sure to use a voltage limited charger (13.7 volts for a 12 volt battery) as any overcharge is very detrimental even if limited to 0.1C.
Aug 25, 2010, 03:13 PM
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Dan Baldwin's Avatar
I have a bunch of SLA batteries on my bench, including several 7 ah batteries, and they all say to charge at an initial rate of .3 C or less, so 2.1 amps or less for a 7 ah battery.

They also say to charge to 13.5-13.8 volts for standby use, and 14-15 volts for cycle use.

Dan
Aug 27, 2010, 12:42 AM
Registered User
Quote:
Originally Posted by Rodney
Especially on sealed (no maintenance ) cells, limit the charge rate to 0.1C else you risk ruining the battery. Be sure to use a voltage limited charger (13.7 volts for a 12 volt battery) as any overcharge is very detrimental even if limited to 0.1C.
You're thinking of the old "gell cell" batteries. They were very delicate.

The new sealed lead acid batteries are Absorbed Glass
Mat (AGM). AGM's use the same voltage points as lead acid batteries, thus any good lead acid charger with a lowish (motorcycle) rate should work fine.

For example, here's the datasheet for a Yuasa NP7-12
http://datasheet.octopart.com/NP7-12...heet-47645.pdf

They're okay with up to 1.75A... i.e. 0.25C.

Other batteries will have different specs... I've seen some with even higher ratings. YMMV.
Aug 27, 2010, 05:41 AM
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everydayflyer's Avatar
There are AGM batteries which can be charged at 3C but here is the problem / issue here in my opinion.

OP wanted to know a safe charge rate for a Pb and the correct generic answrer IMO is 1/10C as this is indeed safe for any Pb I am aware of.

This is one of those two poster threads. OP asked question in post #1 and first respomder ,post #2 provided excellent / accuract answer.
Aug 27, 2010, 05:48 AM
most exalted one
wish I could delete.


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