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So, how DO I charge a 6V SLA battery?

Started by Unknown March 10, 2008
I bought a 6V, 6Ah battery from Home Depot to power my 3-year-old's
toy electric car (the kind that a kid can ride).  The previous battery
didn't hold a charge when I bought the car.

One reference from batteryuniversity.com mentioned something about
2.50V per cell for SLA batteries.  I'm assuming my battery has 3
cells.  Another website mentions use of an L200 voltage regulating
chip (http://www.myra-simon.com/bike/charger.html).

I've got a 6VDC (nominal) wall wart that puts out just over 9V open-
circuit.

How should I charge it?

Thanks,

Michael
 On Mar 9, 8:17=A0pm, mrdarr...@gmail.com wrote:
 > I bought a 6V, 6Ah battery from Home Depot to power my 3-year-old's
 > toy electric car (the kind that a kid can ride). =A0The previous
battery
 > didn't hold a charge when I bought the car.
 >
 > One reference from batteryuniversity.com mentioned something about
 > 2.50V per cell for SLA batteries. =A0I'm assuming my battery has 3
 > cells. =A0Another website mentions use of an L200 voltage regulating
 > chip (http://www.myra-simon.com/bike/charger.html).
 >
 > I've got a 6VDC (nominal) wall wart that puts out just over 9V
open-
 > circuit.
 >
 > How should I charge it?
 >
 > Thanks,
 >
 > Michael

What became of the charger that came with the car that showed you the
original battery is now bad?

GG
On Mar 9, 9:42 pm, stratu...@yahoo.com wrote:
> On Mar 9, 8:17 pm, mrdarr...@gmail.com wrote: > > I bought a 6V, 6Ah battery from Home Depot to power my 3-year-old's > > toy electric car (the kind that a kid can ride). The previous > battery > > didn't hold a charge when I bought the car. > > > > One reference from batteryuniversity.com mentioned something about > > 2.50V per cell for SLA batteries. I'm assuming my battery has 3 > > cells. Another website mentions use of an L200 voltage regulating > > chip (http://www.myra-simon.com/bike/charger.html). > > > > I've got a 6VDC (nominal) wall wart that puts out just over 9V > open- > > circuit. > > > > How should I charge it? > > > > Thanks, > > > > Michael > > What became of the charger that came with the car that showed you the > original battery is now bad? > > GG
Charger wasn't available. Got the car for $5 from a Thrift Store, intending to utilize the motor assembly only. Turns out the rest of the car was in pretty good condition, and the tiny 6V 4A-h battery worked for maybe a month, then no longer held a charge. I suppose I could run to Wal-Mart and buy a $30 charger for their Power Rangers line, but that would not be nearly as satisfying as a DIY solution... plus, I'm not sure if their charger is tied to the 4Ah battery or not. MD
mrdarrett@gmail.com wrote:
> I bought a 6V, 6Ah battery from Home Depot to power my 3-year-old's > toy electric car (the kind that a kid can ride). The previous battery > didn't hold a charge when I bought the car. > > One reference from batteryuniversity.com mentioned something about > 2.50V per cell for SLA batteries. I'm assuming my battery has 3 > cells. Another website mentions use of an L200 voltage regulating > chip (http://www.myra-simon.com/bike/charger.html). > > I've got a 6VDC (nominal) wall wart that puts out just over 9V open- > circuit. > > How should I charge it?
Per the manufacturer's recommendations. But that's not what you wanted to hear, so read below.
> > Thanks, > > Michael
Here is a way you can charge it: Build a float charger. Set the float voltage to 7 volts. Use a 9 or 12 volt DC wall wart (not your 6v wall wart) The schematic is on the first page of the datasheet http://cache.national.com/ds/LM/LM317.pdf? There are better ways to charge your battery, but this way won't cook it and is simple to build. If you can't build, buy a charger recommended for that battery. Ed
On Sun, 9 Mar 2008 21:17:03 -0700 (PDT), mrdarrett@gmail.com wrote:

>I bought a 6V, 6Ah battery from Home Depot to power my 3-year-old's >toy electric car (the kind that a kid can ride). The previous battery >didn't hold a charge when I bought the car. > >One reference from batteryuniversity.com mentioned something about >2.50V per cell for SLA batteries. I'm assuming my battery has 3 >cells. Another website mentions use of an L200 voltage regulating >chip (http://www.myra-simon.com/bike/charger.html). > >I've got a 6VDC (nominal) wall wart that puts out just over 9V open- >circuit. > >How should I charge it?
My preferred solution to SLA charging is to use the TI/Unitrode UC3906. If you're not into building your own PCB then ready-to-assemble kits are available. http://www.altronics.com.au/index.asp?area=item&id=K1685 They do ship internationally if you can't find a souce for a similar kit nearer to you.
<mrdarrett@gmail.com> wrote in message 
news:a8841939-ddff-4175-8be7-476b6a198445@s13g2000prd.googlegroups.com...
>I bought a 6V, 6Ah battery from Home Depot to power my 3-year-old's > toy electric car (the kind that a kid can ride). The previous battery > didn't hold a charge when I bought the car. > > One reference from batteryuniversity.com mentioned something about > 2.50V per cell for SLA batteries. I'm assuming my battery has 3 > cells. Another website mentions use of an L200 voltage regulating > chip (http://www.myra-simon.com/bike/charger.html). > > I've got a 6VDC (nominal) wall wart that puts out just over 9V open- > circuit. > > How should I charge it? > > Thanks, > > Michael
You can probably use your 6VDC wall wart. Unless it is a really hefty wart, it'll probably droop considerably when subjected to the battery. It may actually fail if the battery is discharged, since they often have internal fuses to prevent fires. So, use a 4.7 ohm 1W resistor in series with it just in case. If the resistor gets too hot to touch (which it won't) while charging, post again with specs for the wart. Regards, Bob Monsen
On Mar 10, 6:07 am, "Bob Monsen" <rcmon...@gmail.com> wrote:
> <mrdarr...@gmail.com> wrote in message > > news:a8841939-ddff-4175-8be7-476b6a198445@s13g2000prd.googlegroups.com... > > > > >I bought a 6V, 6Ah battery from Home Depot to power my 3-year-old's > > toy electric car (the kind that a kid can ride). The previous battery > > didn't hold a charge when I bought the car. > > > One reference from batteryuniversity.com mentioned something about > > 2.50V per cell for SLA batteries. I'm assuming my battery has 3 > > cells. Another website mentions use of an L200 voltage regulating > > chip (http://www.myra-simon.com/bike/charger.html). > > > I've got a 6VDC (nominal) wall wart that puts out just over 9V open- > > circuit. > > > How should I charge it? > > > Thanks, > > > Michael > > You can probably use your 6VDC wall wart. Unless it is a really hefty wart, > it'll probably droop considerably when subjected to the battery. It may > actually fail if the battery is discharged, since they often have internal > fuses to prevent fires. So, use a 4.7 ohm 1W resistor in series with it just > in case. If the resistor gets too hot to touch (which it won't) while > charging, post again with specs for the wart. > > Regards, > Bob Monsen
Bad idea, Michael the OP has stated that it produces 9V off load. The current drawn by the battery drops as it charges. If left plugged in past the full charge point the bettery will receive excessive voltage. Leaving the battery plugged in for a week will result in a dead battery. Around there the DIY superstores sell very cheap flashlights with lead acid batterys and unregulated chargers. They are notorious for the batterys failing. Bob
On Mar 10, 12:50 am, Bob <b...@mailinator.com> wrote:
> On Mar 10, 6:07 am, "Bob Monsen" <rcmon...@gmail.com> wrote: > > > > > <mrdarr...@gmail.com> wrote in message > > >news:a8841939-ddff-4175-8be7-476b6a198445@s13g2000prd.googlegroups.com... > > > >I bought a 6V, 6Ah battery from Home Depot to power my 3-year-old's > > > toy electric car (the kind that a kid can ride). The previous battery > > > didn't hold a charge when I bought the car. > > > > One reference from batteryuniversity.com mentioned something about > > > 2.50V per cell for SLA batteries. I'm assuming my battery has 3 > > > cells. Another website mentions use of an L200 voltage regulating > > > chip (http://www.myra-simon.com/bike/charger.html). > > > > I've got a 6VDC (nominal) wall wart that puts out just over 9V open- > > > circuit. > > > > How should I charge it? > > > > Thanks, > > > > Michael > > > You can probably use your 6VDC wall wart. Unless it is a really hefty wart, > > it'll probably droop considerably when subjected to the battery. It may > > actually fail if the battery is discharged, since they often have internal > > fuses to prevent fires. So, use a 4.7 ohm 1W resistor in series with it just > > in case. If the resistor gets too hot to touch (which it won't) while > > charging, post again with specs for the wart. > > > Regards, > > Bob Monsen > > Bad idea, Michael the OP has stated that it produces 9V off load. > The current drawn by the battery drops as it charges. > If left plugged in past the full charge point the bettery will receive > excessive voltage. Leaving the battery plugged in for a week > will result in a dead battery. > > Around there the DIY superstores sell very cheap flashlights > with lead acid batterys and unregulated chargers. They are > notorious for the batterys failing. > > Bob
Yep, 9V off load; once loaded, voltage dropped to about 6.42V @ 177mA. I monitored the voltage every half-hour or so until voltage rose to 6.77V 6 hrs later, then cut the juice (it was bedtime anyway). I was just trying to figure out the point where I should stop charging. I'll study the other responses and see what I can do. Thanks, MD
On Mar 9, 10:55 pm, ehsjr <eh...@bellatlantic.net> wrote:
> mrdarr...@gmail.com wrote: > > I bought a 6V, 6Ah battery from Home Depot to power my 3-year-old's > > toy electric car (the kind that a kid can ride). The previous battery > > didn't hold a charge when I bought the car. > > > One reference from batteryuniversity.com mentioned something about > > 2.50V per cell for SLA batteries. I'm assuming my battery has 3 > > cells. Another website mentions use of an L200 voltage regulating > > chip (http://www.myra-simon.com/bike/charger.html). > > > I've got a 6VDC (nominal) wall wart that puts out just over 9V open- > > circuit. > > > How should I charge it? > > Per the manufacturer's recommendations. > But that's not what you wanted to hear, > so read below. > > > > Thanks, > > > Michael > > Here is a way you can charge it: > Build a float charger. Set the float voltage to 7 volts. > Use a 9 or 12 volt DC wall wart (not your 6v wall wart) > The schematic is on the first page of the datasheethttp://cache.national.com/ds/LM/LM317.pdf? > > There are better ways to charge your battery, but this > way won't cook it and is simple to build. > > If you can't build, buy a charger recommended for > that battery. > > Ed
Thanks! Looks simpler than the L200. Just wondering, where did you get the value of 7.00V? Should I apply a brief charge at 7.50V to get maximum capacity? "At 2.37V, most lead-acid batteries start to gas, causing loss of electrolyte and possible temperature increases. The exceptions are small sealed lead acid batteries (SLA), which can be charged to 2.50V/ cell without adverse side effect." http://www.batteryuniversity.com/partone-13.htm MD
"Bob" <bob9@mailinator.com> wrote in message 
news:1dc6c3ed-94e3-4b00-aaf0-f1338f75f79e@m44g2000hsc.googlegroups.com...
> On Mar 10, 6:07 am, "Bob Monsen" <rcmon...@gmail.com> wrote: >> <mrdarr...@gmail.com> wrote in message >> >> news:a8841939-ddff-4175-8be7-476b6a198445@s13g2000prd.googlegroups.com... >> >> >> >> >I bought a 6V, 6Ah battery from Home Depot to power my 3-year-old's >> > toy electric car (the kind that a kid can ride). The previous battery >> > didn't hold a charge when I bought the car. >> >> > One reference from batteryuniversity.com mentioned something about >> > 2.50V per cell for SLA batteries. I'm assuming my battery has 3 >> > cells. Another website mentions use of an L200 voltage regulating >> > chip (http://www.myra-simon.com/bike/charger.html). >> >> > I've got a 6VDC (nominal) wall wart that puts out just over 9V open- >> > circuit. >> >> > How should I charge it? >> >> > Thanks, >> >> > Michael >> >> You can probably use your 6VDC wall wart. Unless it is a really hefty >> wart, >> it'll probably droop considerably when subjected to the battery. It may >> actually fail if the battery is discharged, since they often have >> internal >> fuses to prevent fires. So, use a 4.7 ohm 1W resistor in series with it >> just >> in case. If the resistor gets too hot to touch (which it won't) while >> charging, post again with specs for the wart. >> >> Regards, >> Bob Monsen > > Bad idea, Michael the OP has stated that it produces 9V off load. > The current drawn by the battery drops as it charges.
Do you know how much the current drops?
> If left plugged in past the full charge point the bettery will receive > excessive voltage. Leaving the battery plugged in for a week > will result in a dead battery.
There is such a thing as overdesign. For example, it is possible to use a kit, a charger chip, or a discrete circuit like this one: 8 - 12 V input ------o-----o------------o-----o------. | | | | | | | | | .-. | | | | | | 1.38 Ohm 1W | | | | | | | >| |< | '-' | |-----o--| >| | .-. /| | |\ |----o 4.7k | | | | | /| | | | | '----o | | '-' o------------)-----o---||-+ N-MOSFET | | | ||-> | | | ||-+ | | | | | | | 10k | | |/ \| ___ | o---| |--o-|___|-o--------. | |> <| | | | | | | | | '-----o------' .-. --- | | | | 22k - z 5.1V .-. | | --- 6V SLA A | | 1k '-' - | | | | | | '-' | | | | | | -----o-----------o-----------o----------------' GND All PNP 2N3906. All NPN 2N3904 Constant current at 500mA until battery reaches 7.5V (created by AACircuit v1.28.6 beta 04/19/05 www.tech-chat.de) (I've included an LTSpice of it, for those interested.) However, I suspect that would be overkill for the poor guy.
> > Around there the DIY superstores sell very cheap flashlights > with lead acid batterys and unregulated chargers. They are > notorious for the batterys failing. >
I think they specify that you should take the battery off the charger after it is charged.
> Bob
Regards, Bob Monsen Here is the circuit in LTSpice format: Version 4 SHEET 1 880 680 WIRE -112 16 -336 16 WIRE 48 16 -112 16 WIRE 208 16 48 16 WIRE 336 16 208 16 WIRE 336 32 336 16 WIRE -112 48 -112 16 WIRE 48 48 48 16 WIRE 208 64 208 16 WIRE -32 96 -48 96 WIRE -16 96 -32 96 WIRE -336 112 -336 16 WIRE 336 112 272 112 WIRE -32 160 -32 96 WIRE 48 160 48 144 WIRE 48 160 -32 160 WIRE 336 160 336 112 WIRE -112 176 -112 144 WIRE 208 176 208 160 WIRE 208 176 -112 176 WIRE 288 176 208 176 WIRE -112 224 -112 176 WIRE 48 224 48 160 WIRE -176 272 -224 272 WIRE 128 272 112 272 WIRE 144 272 128 272 WIRE 336 272 336 256 WIRE 336 272 224 272 WIRE -336 288 -336 192 WIRE 128 304 128 272 WIRE 336 304 336 272 WIRE -224 336 -224 272 WIRE -112 336 -112 320 WIRE -32 336 -112 336 WIRE 48 336 48 320 WIRE 48 336 -32 336 WIRE 336 336 336 304 WIRE -32 352 -32 336 WIRE -336 448 -336 288 WIRE -224 448 -224 416 WIRE -224 448 -336 448 WIRE -32 448 -32 432 WIRE -32 448 -224 448 WIRE 128 448 128 384 WIRE 128 448 -32 448 WIRE 336 448 336 400 WIRE 336 448 128 448 FLAG -336 288 0 FLAG 336 304 a SYMBOL voltage -336 96 R0 WINDOW 123 0 0 Left 0 WINDOW 39 0 0 Left 0 SYMATTR InstName V1 SYMATTR Value 9V SYMBOL pnp 272 160 R180 SYMATTR InstName Q2 SYMATTR Value 2N3906 SYMBOL res 320 16 R0 SYMATTR InstName R1 SYMATTR Value 1.38 SYMATTR SpiceLine pwr=1 SYMBOL pnp -48 144 R180 SYMATTR InstName Q3 SYMATTR Value 2N3906 SYMBOL pnp -16 144 M180 SYMATTR InstName Q4 SYMATTR Value 2N3906 SYMBOL npn -176 224 R0 SYMATTR InstName Q5 SYMATTR Value 2N3904 SYMBOL npn 112 224 M0 SYMATTR InstName Q6 SYMATTR Value 2N3904 SYMBOL res 240 256 R90 WINDOW 0 0 56 VBottom 0 WINDOW 3 32 56 VTop 0 SYMATTR InstName R2 SYMATTR Value 10k SYMBOL res 144 400 R180 WINDOW 0 36 76 Left 0 WINDOW 3 36 40 Left 0 SYMATTR InstName R3 SYMATTR Value 22k SYMBOL res -48 336 R0 SYMATTR InstName R4 SYMATTR Value 1k SYMBOL cap 320 336 R0 SYMATTR InstName C1 SYMATTR Value 1 SYMBOL voltage -224 320 R0 WINDOW 123 0 0 Left 0 WINDOW 39 0 0 Left 0 SYMATTR InstName V2 SYMATTR Value 5.1 SYMBOL pmos 288 256 M180 SYMATTR InstName M1 SYMATTR Value FDS4953 TEXT 408 280 Left 0 !.ic V(a) = 6 TEXT -370 458 Left 0 !.tran 10