Forums

Battery charger ??

Started by Dave, I can't do that August 31, 2013
Hi All,

A few months back I bought a really nice hand held spotlight and last night=
 it crapped out on me. I put it on charge and this morning it was still dea=
d so I opened it up. A small 2.3AH, 6-volt sealed battery and a wall-wart c=
harger with the prongs facing out of the back. A bit of a visual surprise.

A bit of poking around and the wal-wart (6vdc 300ma) is a done for. I have =
a 7vdc 700ma wall wart that I am hoping I can use. The original had no char=
ging controller, the output went straight to the battery. I am hoping I can=
 do the same with the 7vdc.

No load output was 11vdc. Clipping to the battery it drops to 8.4vdc and as=
 I watched, about every 20-seconds the voltage would drop 0.01v. Not sure w=
hy but then I am a **Mechanical** Engineer. {grin}

Nothing got hot after 5-minutes, with the charger removed, the battery was =
already holding 5.4vdc, so I am guessing that is still OK.

The questions.
1:
Should I have a resistor as a current limiter? If so what value and wattage=
?
2:
Is it OK to just let the 7vdc supply just feed into the battery? Providing =
of course I unplug it after a reasonable amount of time?=20
3:
Will the battery and charger find a balance at somewhere around 7v when the=
 battery is fully charged?

This is a really good light when it was working and I am reluctant to spend=
 anther 60-bucks when it is only a charging problem.

Useful suggestions?

Thanks
On Saturday, August 31, 2013 10:43:06 PM UTC-4, Dave, I can't do that wrote=
:
> Hi All, >=20 >=20 >=20 > A few months back I bought a really nice hand held spotlight and last nig=
ht it crapped out on me. I put it on charge and this morning it was still d= ead so I opened it up. A small 2.3AH, 6-volt sealed battery and a wall-wart= charger with the prongs facing out of the back. A bit of a visual surprise= .
>=20 >=20 >=20 > A bit of poking around and the wal-wart (6vdc 300ma) is a done for. I hav=
e a 7vdc 700ma wall wart that I am hoping I can use. The original had no ch= arging controller, the output went straight to the battery. I am hoping I c= an do the same with the 7vdc.
>=20 >=20 >=20 > No load output was 11vdc. Clipping to the battery it drops to 8.4vdc and =
as I watched, about every 20-seconds the voltage would drop 0.01v. Not sure= why but then I am a **Mechanical** Engineer. {grin}
>=20 >=20 >=20 > Nothing got hot after 5-minutes, with the charger removed, the battery wa=
s already holding 5.4vdc, so I am guessing that is still OK.
>=20 >=20 >=20 > The questions. >=20 > 1: >=20 > Should I have a resistor as a current limiter? If so what value and watta=
ge?
>=20 > 2: >=20 > Is it OK to just let the 7vdc supply just feed into the battery? Providin=
g of course I unplug it after a reasonable amount of time?=20
>=20 > 3: >=20 > Will the battery and charger find a balance at somewhere around 7v when t=
he battery is fully charged?
>=20 >=20 >=20 > This is a really good light when it was working and I am reluctant to spe=
nd anther 60-bucks when it is only a charging problem.
>=20 >=20 >=20 > Useful suggestions? >=20 >=20 >=20 > Thanks
In answer to your specific queries, please note: 1. If the battery capacity rating is 'X' AH, the maximum charging current must be X/10.0 2. The 7 Volt DC should be fine. There has to be a potential difference for the current to flow from the charger to the=20 battery. Also note that a sealed lead acid battery is a=20 rugged device and a bit of overcharging would not damage it, provided the charging current is controlled (please see 1.0 above) 3. When the battery is fully charged, it will not draw any=20 current from the charger. All of the above hold for sealed lead acid cells as they are=20 inherently rugged. Other batteries as Li-ion are very delicate.
<dakupoto@gmail.com>


1. If the battery capacity rating is 'X' AH, the maximum charging
   current must be X/10.0
2. The 7 Volt DC should be fine. There has to be a potential
   difference for the current to flow from the charger to the
   battery. Also note that a sealed lead acid battery is a
   rugged device and a bit of overcharging would not damage it,
   provided the charging current is controlled (please see 1.0
   above)
3. When the battery is fully charged, it will not draw any
   current from the charger.

** Fraid it will and rather too much in this case.

 A DC supply ( like the OP has) and a battery charger are very different 
things.


All of the above hold for sealed lead acid cells as they are
inherently rugged.

** They explode if overcharged.

The 8.4 volts reported by the OP when the battery is on charge is way too 
high.

His 2.3AH battery is probably stuffed as well as the charger.


...   Phil




"Phil Allison"  wrote in message =
news:b8fq8vFcmi9U1@mid.individual.net...

> <dakupoto@gmail.com>
>> 1. If the battery capacity rating is 'X' AH, the maximum >> charging current must be X/10.0 >> 2. The 7 Volt DC should be fine. There has to be a potential >> difference for the current to flow from the charger to the >> battery. Also note that a sealed lead acid battery is a >> rugged device and a bit of overcharging would not damage it, >> provided the charging current is controlled (please see 1.0 >> above) >> 3. When the battery is fully charged, it will not draw any >> current from the charger.
> ** Fraid it will and rather too much in this case.
> A DC supply ( like the OP has) and a battery charger are very > different things.
>> All of the above hold for sealed lead acid cells as they are >> inherently rugged.
> ** They explode if overcharged.
> The 8.4 volts reported by the OP when the battery is on charge > is way too high.
> His 2.3AH battery is probably stuffed as well as the charger.
I agree. SLAs are more readily damaged by overcharging because the = resultant=20 gassing may be vented to the environment and water cannot be added to=20 restore the electrolyte as in a flooded lead-acid battery. It may = survive a=20 short time of overcharging at C/10 or longer at about C/100, but it is = best=20 to end the charge when the battery is full and wait several months = before=20 recharging. And they can remain fairly well charged over a 6 month to = one=20 year period. Some useful information: http://evbatterymonitoring.com/WebHelp/Section_3.htm http://batteryuniversity.com/learn/article/charging_the_lead_acid_battery= http://www.mpoweruk.com/ http://www.evdl.org/lib/index.html http://www.evdl.org/pages/hartcharge.html Lead acid batteries have a normal voltage of 2.2 to 2.3 volts per cell = fully=20 charged, and 2.4 to 2.5 volts per cell maximum when charging. So the 6V=20 battery should never see more than 7.2 to 7.5 volts under charge. 1.67 = volts=20 per cell is the lowest it should ever be before damage occurs, so 5 = volts is=20 essentially dead. There is also a temperature coefficient and internal=20 series resistance which can affect the voltage when charging and=20 discharging. Here is a thread where I asked for and found much information on = charging=20 SLA batteries. I plan to make a BMS for 12V SLAs so multiple batteries = may=20 be safely charged in series: http://www.diyelectriccar.com/forums/showthread.php/sla-sealed-lead-acid-= battery-charging-88167.html Paul
On 8/31/2013 10:43 PM, Dave, I can't do that wrote:
> Hi All, > > A few months back I bought a really nice hand held spotlight and last night it crapped out on me. I put it on charge and this morning it was still dead so I opened it up. A small 2.3AH, 6-volt sealed battery and a wall-wart charger with the prongs facing out of the back. A bit of a visual surprise. > > A bit of poking around and the wal-wart (6vdc 300ma) is a done for. I have a 7vdc 700ma wall wart that I am hoping I can use. The original had no charging controller, the output went straight to the battery. I am hoping I can do the same with the 7vdc. > > No load output was 11vdc. Clipping to the battery it drops to 8.4vdc and as I watched, about every 20-seconds the voltage would drop 0.01v. Not sure why but then I am a **Mechanical** Engineer. {grin} > > Nothing got hot after 5-minutes, with the charger removed, the battery was already holding 5.4vdc, so I am guessing that is still OK. > > The questions. > 1: > Should I have a resistor as a current limiter? If so what value and wattage? > 2: > Is it OK to just let the 7vdc supply just feed into the battery? Providing of course I unplug it after a reasonable amount of time? > 3: > Will the battery and charger find a balance at somewhere around 7v when the battery is fully charged? > > This is a really good light when it was working and I am reluctant to spend anther 60-bucks when it is only a charging problem. > > Useful suggestions? > > Thanks >
-------- ------- | Wall +|---Vin| LM317 |Vout---+ | Wart | ------- | | 7V | Adj [R1] | 700 mA | | | | | +-----------+---[+BATT-]---+ | | | | -|-------------------------------------+ -------- The above is a simple "overnight" current limited charger. For your battery to charge at about C/10 you want to limit the current to about 230 mA. R1 computes to ~ 5.45 ohms at about 1.25 watts. Make R1 by putting a 10 ohm and a 12 ohm resistor in parallel - use 1 watt resistors. Use a heatsink on the LM317. Ed
On 2013-09-01, Dave, I can't do that <davenpete@gmail.com> wrote:
> Hi All, > > A few months back I bought a really nice hand held spotlight and last night it crapped out on me. I put it on charge and this morning it was still dead so I opened it up. A small 2.3AH, 6-volt sealed battery and a wall-wart charger with the prongs facing out of the back. A bit of a visual surprise. > > A bit of poking around and the wal-wart (6vdc 300ma) is a done for. I have a 7vdc 700ma wall wart that I am hoping I can use. The original had no charging controller, the output went straight to the battery. I am hoping I can do the same with the 7vdc.
7V isn't enough to charge a "6v" sealed lead-acid battery. you want to charge to avout 7.2 volts
> No load output was 11vdc.
That helps.
> Clipping to the battery it drops to 8.4vdc > and as I watched, about every 20-seconds the voltage would drop 0.01v. > Not sure why but then I am a **Mechanical** Engineer. {grin}
The battery sounds a bit sick.
> Nothing got hot after 5-minutes, with the charger removed, the > battery was already holding 5.4vdc, so I am guessing that is still OK.
> The questions. > 1: > Should I have a resistor as a current limiter? If so what value and wattage?
Typically you want to limit the charge voltage instead.
> 2: > Is it OK to just let the 7vdc supply just feed into the battery? Providing of course I unplug it after a reasonable amount of time?
yes, but determineing the correct time to disconnect it could be tricky
> 3: > Will the battery and charger find a balance at somewhere around 7v when the battery is fully charged?
yes, but the battery will then start to heat up,
> This is a really good light when it was working and I am reluctant to spend anther 60-bucks when it is only a charging problem.
you could try one of these: http://www.ebay.com/itm/6-V-Volt-Sealed-Lead-Acid-Rechargeable-Battery-Charger-/261147046414 -- &#9858;&#9859; 100% natural --- news://freenews.netfront.net/ - complaints: news@netfront.net ---
Thanks to those helpful replies and one not-so-helpful. :)

Being a little lazy, the charger in Jasen's post seems the best option, although it will not be from that crackhead-laden auction site. Once burned...

Ehsjr's little ASCII art makes sense if I can find the parts here. If I have to buy parts to build, I may as well buy the charger, but thanks so much for the other good replies.

@Phil, it is fine to show us/me how clever you are, but I am asking for help and your post did nothing in that vein. Dare I point out the closing line in my OP, "Useful suggestions," which you failed to read obviously. :)
"Dave, I can't do that"
> > Thanks to those helpful replies and one not-so-helpful. :)
** Fuck you.
> Being a little lazy, the charger in Jasen's post seems the best > option, although it will not be from that crackhead-laden > auction site. Once burned...
** Hey, we got a live one here folks...
> Ehsjr's little ASCII art makes sense if I can find the parts here. > If I have to buy parts to build, I may as well buy the charger, > but thanks so much for the other good replies. > > @Phil, it is fine to show us/me how clever you are, but I am > asking for help and your post did nothing in that vein. Dare I > point out the closing line in my OP, "Useful suggestions," > which you failed to read obviously. :)
** Hey - fuckhead. I did NOT post ANY reply to YOU !! I was correcting the nonsense posted by another trolling idiot here. Pearls before swine, in your case. ... Phil
On Sunday, September 1, 2013 2:53:50 PM UTC-7, Phil Allison wrote:
> ** Fuck you. > > ** Hey, we got a live one here folks... > > ** Hey - fuckhead. >
Ahhh, phil, what a nice man. OK, back to the charger and the helpful replies. Bought a charger from Amazon for $3.50-shipped. After a 10-hour charge, the battery is just fine and holding charge well. Thanks to all who responded, including you phil and I hope your anger clears up soon. I am left to muse if you would be so aggressive if we were standing toe to toe. My guess is not.