Charge gel cell with car charger?

[Mike Cook]

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.

 

[Mike Cook]

The gel cell is 12v.

 

[Jan Panteltje]

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,

 

Followups set to sci.electronics.repair .

In sci.electronics.components Mike Cook <mcham@notyahoo.com> wrote:

Can the car charger be used to charge this battery?

Probably. Do you know what the amp-hour capacity is of the battery that
is in there now? A little Googling *1 suggests that the original 12 V
battery might have been six Gates/Hawker/Enersys "Cyclon" 2 V cells in
series; the replacement that one site sells looks suspiciously like the
common or garden 12 V 7 amp-hour "gel cell", plus a couple of brackets
to make it fit. If the battery capacity is around 6 or 7 amp-hours,
then the 0.5 A charger will work OK, as long as you don't mind it taking
12 or more hours for a full charge.

One manufacturer of these batteries *2 says this is how you charge the
12 V, 7 Ah size:

"Limit initial current to 2.1A. Charge until battery voltage (under
charge) reaches 14.4 to 14.7 volts at 68°F (20°C). Hold at 14.4 to 14.7
volts until current drops to under 70mA. Battery is fully charged under
these conditions, and charger should be disconnected or switched to
"float" voltage."

So... the 0.5 A car battery charger should be OK. The charger you have
may not do the automatic float and shutoff - more below.

The voltage output by the car charger will be slightly different than
what a sealed battery needs; this is probably not too important in this
application, but may reduce battery life a little. If you want, you can
get an "official" charger for sealed batteries for $35 or so; *3 has
0.8 A output and will work a little faster. Or, get one of the
automatic car battery maintainers like a Deltran Battery Tender or
Schumacher Battery Companion; these usually have 1.0 to 1.5 A outputs
and will automagically switch to a low-current charge once the battery
is full. These are easy to find at local stores.

He can install a timer to limit charge time if that's something
required.

If the charger doesn't have any kind of automatic shutoff, then this
might not be a bad idea. The million dollar question is "how long is
enough". The answer depends on how discharged the battery is. The
simple answer (for a 7 amp-hour battery) is 7 amp-hours / 0.5 amps =
14 hours. But: the charge won't be 0.5 A for the whole time. It may
start off that way but it will go down as the battery charges up, so
a full charge will take longer.

At a guess, I would get one of those 12 hour spring wound timer switches
(often used with attic fans) from the hardware store, and put it in an
outlet box along with an outlet and a cord. Maybe set it for 2 or 3
hours the first time, then when it shuts off, measure the battery
voltage to find out how full it is. If not full enough, repeat. After
a few runs you will know what to set the timer to initially.

*1 http://www.ereplacementparts.com/ryobi-150r-41ae150f034-volt-battery-trimmer-parts-c-7931_15633_18531.html

*2 http://www.power-sonic.com/images/powersonic/sla_batteries/ps_psg_series/12volt/PS-1270_11_Feb_21.pdf

*3 http://www.mouser.com/ProductDetail/Power-Sonic/PSC-12800A-C/?qs=XATL/JQ9g1zerdAMdrMzKQ==

Standard disclaimers apply; I don't get money or other consideration
from any companies mentioned.

Matt Roberds

 

[dave]

On 02/24/2013 12:06 AM, 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.

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.

 

[dave]

On 02/24/2013 12:30 AM, Mike Cook wrote:

The gel cell is 12v.

Most lead acid batteries are ca. 13.6 Vdc If your car battery ever got
down to 12 Vdc the car would have trouble starting. Lead acid cells are
about 2.22 Vdc.

 

[Phil Allison]

"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

 

[dave]

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.

 

[Phil Allison]

"dave"

Phil Allison

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.


They have vents.

** So you have no fucking idea what really happens.




..... Phil

 

[Jamie]

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.

If you see a jump in voltage then this means the battery is on its
last leg and you really shouldn't push it.

A good test for this condition is to fully charge it with your auto
charger and disconnect it and test the voltage a day later or few hours
later to note the discharge.

It is possible the charger is bad but I am going with a
bad battery. You can always get a weak battery to appear good with an
extra current source but the charge will dwindle.


Jamie

 

[Wild_Bill]

Otherwise known as/a-k-a LER.. light emitting resistor, and they work well
for current limiters.
Brake light, side marker light, license plate light etc all have different
current ratings.

Measure the current at full operating voltage, which can be written on the
bulb/lamp base.
Sockets with leads can be purchased at auto parts stores, or leads can be
soldered to many lamps.

--
Cheers,
WB
..............


"Jan Panteltje" <pNaonStpealmtje@yahoo.com> wrote in message
news:kgcpgh$ipp$1@news.albasani.net...

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,

 

[Tim Wescott]

On Sun, 24 Feb 2013 00:06:18 -0800, 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.

Go to a boat shop, feed store, hardware store, whatever, and get a float
charger.



--
Tim Wescott
Control system and signal processing consulting
www.wescottdesign.com

 

[Michael A. Terrell]

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.

In or out of circuit? If the thing doesn't have any filter caps, the
out of circuit reading will be low.

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.

 

[Michael A. Terrell]

dave 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.

They are damaged long before they can vent.

 

[Michael A. Terrell]

Jamie wrote:

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.

More bad bad advice from Maynard Philbrook, as usual. Does the
voltage across the battery go up when the charger is connected?

If you see a jump in voltage then this means the battery is on its
last leg and you really shouldn't push it.

Bullshit, as always. The connector for the charger may be bad,
especially if it disconnects the battery from the tool while on charge.
I've seen connects melted, or the solder overheat 7 the wires fall off
poor designs.

A good test for this condition is to fully charge it with your auto
charger and disconnect it and test the voltage a day later or few hours
later to note the discharge.

It is possible the charger is bad but I am going with a
bad battery. You can always get a weak battery to appear good with an
extra current source but the charge will dwindle.

You're long overdue for replacement.

 

[David Eather]

On Mon, 25 Feb 2013 07:56:18 +1000, Tim Wescott <tim@seemywebsite.please>
wrote:

On Sun, 24 Feb 2013 00:06:18 -0800, 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.

Go to a boat shop, feed store, hardware store, whatever, and get a float
charger.

Get a gel-cell float charger. The recommended terminal charging voltage
for a gel-cell is slightly lower than for a standard lead acid.

 

[Ian Field]

"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.

 

[Ian Field]

"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.

 

[Ian Field]

"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.

 

[John Fields]

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