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Author Topic: charging gel cel batteries  (Read 657 times)

Posts: 102

« on: March 21, 2004, 12:27:37 AM »

hi all.

i have eight 12 volt 7 ah batteries and was wanting to charge them (one at a time!). i have a 12 volt 6 amp battery charger and was wondering if i could use that to charge them? if not, a local told me that i might try hooking the gel cell up to my little radio shack 3 amp power supply (he charges his that way). i also have a big 20 amp power supply and assorted wallworts.

 will any of these work?

tnx sam/kc8vcb

Posts: 300


« Reply #1 on: March 21, 2004, 01:32:31 AM »

I also use my 3 amp Micronta (actually 2.5 A continuous with a 3 A surge) power supply to charge my gel cells. Due to the fact that my power supply is not 13.8V, but 14.5V, I just charge the gel cells through a silicone (not germanium) diode, so the voltage through the power supply drops to 13.8V. The diode also acts as a fuse in case the power supply malfunctions and you get a dead short across the battery. I once learned that lesson the hard way. I had a nice fire going when the power supply shorted and the insulation burned right off the wires that connected the battery to the power supply. I had several gel cells connected in parallel to my 25A supply, charging. The circuit breaker tripped and the crowbar circuit placed a dead short across the + and - leads. Its a good thing I was home when it happened. Now, I connect gel cells to a power supply through diodes only. After that mess, I had to replace the SCR in the power supply to get the power supply working again. The SCR had a dead short when I tested it. If I were you, I wouldn't charge any battery (gel cell or wet cell) with a power supply unless you do it through a diode.

Posts: 0

« Reply #2 on: March 21, 2004, 10:10:24 AM »

 I asked the same question on here about 4 weeks ago and had about 20 replys. Look into the Archives on here and you can read thoes also. Had some good replys.Right now I use a Radio Shack 12 volt/1 amp power supply(looks like a big wal wart)and it works very well for me.It puts out exactly 13.8 volts which is pretty good for a wal wart. 73,Jim

Posts: 628

« Reply #3 on: March 21, 2004, 01:08:35 PM »

The way a battery is handled defines how long a battery will last. If you routinely run it way down or charge it up too fast it will shorten its life. Take a look at the the Battery Tender web site, "".


Posts: 6231

« Reply #4 on: March 21, 2004, 01:43:50 PM »

Those batteries should be charged at 13.5 to 13.8 VDC at a current of 500 to 1000 MA.  In the case of those gel cells, even 1000 MA at 13.8 is a bit too high--but acceptable.

If you want to use a 3 A power supply, gang three of the cells together (in parallel) to keep from driving too much current through one of the batteries.  If the batteries start to get very warm, disconnect them and resume charging after they've cooled for a while.

You can still charge just one of them at a time at 3 A, but don't expect them to last too long if you do--you'll just fry the usefulness out of them.  Remember, those are SEALED gel cells, not vented storage batteries.  Just remember what happens to a car battery when it is overcharged--those batteries can take far more abuse and overcharging than a gel cell can.

Posts: 3317

« Reply #5 on: March 21, 2004, 01:50:29 PM »

If you charge the battery with a voltage over about 14.2V you need to current limit the charging to about a half-amp or so, it usually says right on the battery.  If your battery is pretty low and you use a car-type charger, you may find you are running too much current into the battery.

Monitor the charge voltage and current.  Radio Shack sells (or sold, anyway) convenient and inexpensive meters for this purpose.

These batteries like to be float-charged at 13.8 or so.

If you (or anyone else) needs some more-portrable gel-cell batteries than the ones you are mentioning, I have a large quantity of smaller batteries.

These are 2 lb., brand-new, 2.3 amp-hour Yuasa gel-cell batteries I will sell for $4 each.  

A great deal, and MUCH lighter weight than the 7 amp-hour batteries!!

Posts: 9930

« Reply #6 on: March 21, 2004, 06:30:12 PM »

A & A engineering  sells a 1 amp and a 5 amp smart charger, starts with high current then goes to hi voltage, low current then goes to trickle..

has red pos, black neg and yellow wire which goes to pos post on battery fo sensing.. $50 or so for the small one made for hooking upto your rv, boat or standby bateries..

nice to have one around, they advertise in most ham magazines and have a site I think is a& or such

Posts: 9930

« Reply #7 on: March 23, 2004, 06:51:59 PM »

another trick to use is if you already own or buy a cheep UPS back up ( like you use on your computer when the power goes out) . I have several and they all have these batteries in side, so take off the bottom plate , make a couple of wires to go from the  existing battery + and - terminals and run them out side the ups and hook up the second battery.  use care not to short out the dc etc.. I got mine (APC brand UPS on ebay for $15  shipped..)
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