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Charge gel cell with car charger?

Started by Mike Cook February 24, 2013
dave wrote:
> > Here's another flash, your 1.5 V "AA" NiCads are only putting out 1.2 Vdc.
And that's news?
dave wrote:
> > On 02/24/2013 05:37 AM, SoothSayer wrote: > > On Sun, 24 Feb 2013 05:17:53 -0800, dave <ricketzz@earthlink.net> wrote: > > > >> On 02/24/2013 05:14 AM, Phil Allison wrote: > >>> "dave" > >>>> > >>>> You answered your own question. As long as the battery doesn't heat up on > >>>> a big charge you're probably OK. > >>> > >>> > >>> ** 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 > >>> > >>> > >> > >> They have vents. > > > > Which are NOT meant for overcharge relief. > > > > I didn't say they were. I was speaking to the "bits of battery and acid" > prediction above.
I've seen the results of several car batteries exploding. Maybe your head should be under the hood when one blows.

"Jan Panteltje" <pNaonStpealmtje@yahoo.com> wrote in message 
news:kgcpgh$ipp$1@news.albasani.net...
> On a sunny day (Sun, 24 Feb 2013 00:06:18 -0800) it happened Mike Cook > <mcham@NOTyahoo.com> wrote in > <0001HW.CD4F09FA05B8251DB04179BF@news.eternal-september.org>: > >>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. > > Old trick was to put a car headlight or some other low voltage bulb (break > light) > in series as current limiter. > Maybe modern car has only LEDs, dunno, :-)
Its a trick I often use if I have to, but increasingly I turn to the more modern electronic/microcontroller type chargers that automatically switch to trickle charge.

"dave" <ricketzz@earthlink.net> wrote in message 
news:1sadnWIBuIufjrfMnZ2dnUVZ_j-dnZ2d@earthlink.com...
> On 02/24/2013 05:14 AM, Phil Allison wrote: >> "dave" >>> >>> You answered your own question. As long as the battery doesn't heat up >>> on >>> a big charge you're probably OK. >> >> >> ** 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 >> >> > > They have vents.
How very convenient - till you have to pry off the glued on cover plate to refill the gassed off electrolyte, then glue/tape it all back together.

"Jamie" <jamie_ka1lpa_not_valid_after_ka1lpa_@charter.net> wrote in message 
news:72pWs.41135$Q91.3308@newsfe26.iad...
> Mike Cook wrote: >> 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. >> > > > THe OEM charger most likely is unfiltered. Put a cap on the output but do > not connect it to the battery and then do a voltage check.
The old "iron-transformer" chargers were usually impedance limited, so the off load voltage will be significantly more than nominal (enough to get a mildly sulphated battery going). In addition a capacitor would charge to the AC peak so what you read would be even higher still.
On 02/25/2013 10:54 AM, Michael A. Terrell wrote:
> > dave wrote: >> >> On 02/24/2013 05:37 AM, SoothSayer wrote: >>> On Sun, 24 Feb 2013 05:17:53 -0800, dave <ricketzz@earthlink.net> wrote: >>> >>>> On 02/24/2013 05:14 AM, Phil Allison wrote: >>>>> "dave" >>>>>> >>>>>> You answered your own question. As long as the battery doesn't heat up on >>>>>> a big charge you're probably OK. >>>>> >>>>> >>>>> ** 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 >>>>> >>>>> >>>> >>>> They have vents. >>> >>> Which are NOT meant for overcharge relief. >>> >> >> I didn't say they were. I was speaking to the "bits of battery and acid" >> prediction above. > > > I've seen the results of several car batteries exploding. Maybe your > head should be under the hood when one blows. >
Why is everyone so rude around here?
On Mon, 25 Feb 2013 22:36:52 -0000, "Ian Field"
<gangprobing.alien@ntlworld.com> wrote:

> > >"Jan Panteltje" <pNaonStpealmtje@yahoo.com> wrote in message >news:kgcpgh$ipp$1@news.albasani.net... >> On a sunny day (Sun, 24 Feb 2013 00:06:18 -0800) it happened Mike Cook >> <mcham@NOTyahoo.com> wrote in >> <0001HW.CD4F09FA05B8251DB04179BF@news.eternal-september.org>: >> >>>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. >> >> Old trick was to put a car headlight or some other low voltage bulb (break >> light) >> in series as current limiter. >> Maybe modern car has only LEDs, dunno, :-) > > >Its a trick I often use if I have to, but increasingly I turn to the more >modern electronic/microcontroller type chargers that automatically switch to >trickle charge.
--- That's a good thing, since it puts you squarely into the rank of a "consumer", where you clearly belong, instead of into the ranks of designers, where you've clearly demonstrated you don't belong. I could be wrong of course, and I'd welcome any rebuttal you might want to proffer with respect to the lamps and loads you used for eliciting your various "tricks". -- JF
On Mon, 25 Feb 2013 15:54:23 -0800, dave <ricketzz@earthlink.net>
wrote:

>On 02/25/2013 10:54 AM, Michael A. Terrell wrote: >> >> dave wrote: >>> >>> On 02/24/2013 05:37 AM, SoothSayer wrote: >>>> On Sun, 24 Feb 2013 05:17:53 -0800, dave <ricketzz@earthlink.net> wrote: >>>> >>>>> On 02/24/2013 05:14 AM, Phil Allison wrote: >>>>>> "dave" >>>>>>> >>>>>>> You answered your own question. As long as the battery doesn't heat up on >>>>>>> a big charge you're probably OK. >>>>>> >>>>>> >>>>>> ** 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 >>>>>> >>>>>> >>>>> >>>>> They have vents. >>>> >>>> Which are NOT meant for overcharge relief. >>>> >>> >>> I didn't say they were. I was speaking to the "bits of battery and acid" >>> prediction above. >> >> >> I've seen the results of several car batteries exploding. Maybe your >> head should be under the hood when one blows. >> > >Why is everyone so rude around here?
Why are you here?
dave wrote:
> > On 02/25/2013 10:54 AM, Michael A. Terrell wrote: > > > > dave wrote: > >> > >> On 02/24/2013 05:37 AM, SoothSayer wrote: > >>> On Sun, 24 Feb 2013 05:17:53 -0800, dave <ricketzz@earthlink.net> wrote: > >>> > >>>> On 02/24/2013 05:14 AM, Phil Allison wrote: > >>>>> "dave" > >>>>>> > >>>>>> You answered your own question. As long as the battery doesn't heat up on > >>>>>> a big charge you're probably OK. > >>>>> > >>>>> > >>>>> ** 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 > >>>>> > >>>>> > >>>> > >>>> They have vents. > >>> > >>> Which are NOT meant for overcharge relief. > >>> > >> > >> I didn't say they were. I was speaking to the "bits of battery and acid" > >> prediction above. > > > > > > I've seen the results of several car batteries exploding. Maybe your > > head should be under the hood when one blows. > > > > Why is everyone so rude around here?
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.
On 24/02/2013 08:06, Mike Cook wrote:
> 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.
For how long?
> Can the car charger be used to charge this battery? He can install a > timer to limit charge time if that's something required.
Lead acid batteries are fickle things but last a long time if looked after. I would prefer to use a charger that could detect end point and either turn off or supply a constant voltage. There are some car battery chargers that do this. A final thing is to check battery terminal voltage. During a fast charge you might accept a voltage of 14.5V, but under long term (float charge) I wouldn't want the charger to push out more that 13.8V. -- Mike Perkins Video Solutions Ltd www.videosolutions.ltd.uk