> On Mar 17, 12:33 pm, "Bob Monsen" <rcmon...@gmail.com> wrote:
>
>><mrdarr...@gmail.com> wrote in message
>>
>>news:ae82ec44-fa48-4be4-880b-64cb3666901f@i29g2000prf.googlegroups.com...
>>
>>
>>
>>
>>>On Mar 17, 12:24 pm, "Bob Monsen" <rcmon...@gmail.com> wrote:
>>>
>>>><mrdarr...@gmail.com> wrote in message
>>
>>>>news:6c8e287b-fd85-4fb8-bff5-23a1c3e0bcfc@h11g2000prf.googlegroups.com...
>>
>>>>>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
>>
>>>>>Ok, I built it. Didn't have a 5k pot handy, so I strung up two 1k
>>>>>resistors in parallel and a bunch of 100 ohm resistors in series until
>>>>>I got about 7.2V out.
>>
>>>>>Hooked it up to the battery, and I was surprised to see only 50mA
>>>>>going through the battery. Typically, without the LM317 I got 100+ mA
>>>>>going through.
>>
>>>>>LM317 was cool to the touch (with heatsink).
>>
>>>>>I thought my power supply was underpowered, so I tried a 12V wall wart
>>>>>(about 14V with no load) instead. But then, after going through the
>>>>>LM317, voltage going to the battery was just over 7.2V. Not
>>>>>comfortable with that, so I went back to my 6V power supply.
>>
>>>>>Any ideas why the current is so low with the LM317? Only modification
>>>>>I made to the datasheet schematic was I used a 10uF electrolytic
>>>>>instead of a 1uF.
>>
>>>>>Thanks,
>>
>>>>>Michael
>>
>>>>The LM317 will set the voltage. If the battery is already charged, it
>>>>won't
>>>>take much current at 7.2V.
>>
>>>>So, first discharge the battery, then try it again.
>>
>>>>I've looked around on the internet, and seems to me that you really want
>>>>to
>>>>be charging the thing at the 'float voltage' of 6.75V. If you set the
>>>>LM317
>>>>to output 6.75V, and just leave it on there, it'll float up the right
>>>>charge
>>>>level after a day or so. You can also just leave the battery on the
>>>>charger
>>>>forever at this voltage, which is a plus.
>>
>>>>The datasheet gives the formula for deriving voltage output. The thing
>>>>basically tries to keep 1.25V between its output and adj pins. So, pick a
>>>>resistor to go between the out and adj pins, and then find another one to
>>>>go
>>>>between adj and ground that is nearest to 5.4 times the first resistor
>>>>value.
>>
>>>>Regards,
>>>> Bob Monsen
>>
>>>Thank you for the information.
>>
>>>Could you provide the links that point to a 6.75V charge?
>>
>>>Thanks,
>>
>>>Michael
>>
>>http://www.jaycar.com.au/images_uploaded/slabatts.pdf
>>
>>Regards,
>> Bob Monsen
>
>
>
> Thanks for that. I'm starting to get dizzy with all the different
> voltage recommendations.
Yup! That's what my "warning" was about. :-( :-)
(It deserves both a "frowny" and a "smiley".)
When you want to get a little more complicated, the
circuit can be modified to include other features.
But modifying the circuit won't get rid of the dizziness.
:-) You'll need to decide the charge parameters you want.
Ed
> On Mar 17, 12:33 pm, "Bob Monsen" <rcmon...@gmail.com> wrote:
>
>
>
>
>
> > <mrdarr...@gmail.com> wrote in message
>
> >news:ae82ec44-fa48-4be4-880b-64cb3666901f@i29g2000prf.googlegroups.com...=
>
> > > On Mar 17, 12:24 pm, "Bob Monsen" <rcmon...@gmail.com> wrote:
> > >> <mrdarr...@gmail.com> wrote in message
>
> > >>news:6c8e287b-fd85-4fb8-bff5-23a1c3e0bcfc@h11g2000prf.googlegroups.com=
...
>
> > >> > 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-ol=
d'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 abo=
ut
> > >> >> > 2.50V per cell for SLA batteries. =A0I'm assuming my battery has=
3
> > >> >> > cells. =A0Another website mentions use of an L200 voltage regula=
> > >> >> > 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
>
> > >> > Ok, I built it. =A0Didn't have a 5k pot handy, so I strung up two 1=
k
> > >> > resistors in parallel and a bunch of 100 ohm resistors in series un=
til
> > >> > I got about 7.2V out.
>
> > >> > Hooked it up to the battery, and I was surprised to see only 50mA
> > >> > going through the battery. =A0Typically, without the LM317 I got 10=
0+ mA
> > >> > going through.
>
> > >> > LM317 was cool to the touch (with heatsink).
>
> > >> > I thought my power supply was underpowered, so I tried a 12V wall w=
art
> > >> > (about 14V with no load) instead. =A0But then, after going through =
the
> > >> > LM317, voltage going to the battery was just over 7.2V. =A0Not
> > >> > comfortable with that, so I went back to my 6V power supply.
>
> > >> > Any ideas why the current is so low with the LM317? =A0Only modific=
ation
> > >> > I made to the datasheet schematic was I used a 10uF electrolytic
> > >> > instead of a 1uF.
>
> > >> > Thanks,
>
> > >> > Michael
>
> > >> The LM317 will set the voltage. If the battery is already charged, it=
> > >> won't
> > >> take much current at 7.2V.
>
> > >> So, first discharge the battery, then try it again.
>
> > >> I've looked around on the internet, and seems to me that you really w=
ant
> > >> to
> > >> be charging the thing at the 'float voltage' of 6.75V. If you set the=
> > >> LM317
> > >> to output 6.75V, and just leave it on there, it'll float up the right=
> > >> charge
> > >> level after a day or so. You can also just leave the battery on the
> > >> charger
> > >> forever at this voltage, which is a plus.
>
> > >> The datasheet gives the formula for deriving voltage output. The thin=
g
> > >> basically tries to keep 1.25V between its output and adj pins. So, pi=
ck a
> > >> resistor to go between the out and adj pins, and then find another on=
e to
> > >> go
> > >> between adj and ground that is nearest to 5.4 times the first resisto=
>
> Michael- Hide quoted text -
>
> - Show quoted text -
Get your head around the difference between "charging" and "floating"
so you don't suffer any more confusion. The ideal charging protocol
doesn't take place at a constant voltage, but rather the voltage
changes according to the battery's state of charge (as evidenced by
current draw).
You, however, do not have a sophisticated "smart charger" to tailor
the charging curve. You'll operate at a fixed voltage. So you should
pick a voltage according to how much time you want to take to charge
the battery. If you want the battery to charge reasonably fast, use
about 7.3 or 7.4 volts. If you have all the time in the world use
about 6.7 or 6.8.
Reply by ●March 17, 20082008-03-17
On Mar 17, 12:33 pm, "Bob Monsen" <rcmon...@gmail.com> wrote:
> <mrdarr...@gmail.com> wrote in message
>
> news:ae82ec44-fa48-4be4-880b-64cb3666901f@i29g2000prf.googlegroups.com...
>
>
>
> > On Mar 17, 12:24 pm, "Bob Monsen" <rcmon...@gmail.com> wrote:
> >> <mrdarr...@gmail.com> wrote in message
>
> >>news:6c8e287b-fd85-4fb8-bff5-23a1c3e0bcfc@h11g2000prf.googlegroups.com...
>
> >> > 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
>
> >> > Ok, I built it. Didn't have a 5k pot handy, so I strung up two 1k
> >> > resistors in parallel and a bunch of 100 ohm resistors in series until
> >> > I got about 7.2V out.
>
> >> > Hooked it up to the battery, and I was surprised to see only 50mA
> >> > going through the battery. Typically, without the LM317 I got 100+ mA
> >> > going through.
>
> >> > LM317 was cool to the touch (with heatsink).
>
> >> > I thought my power supply was underpowered, so I tried a 12V wall wart
> >> > (about 14V with no load) instead. But then, after going through the
> >> > LM317, voltage going to the battery was just over 7.2V. Not
> >> > comfortable with that, so I went back to my 6V power supply.
>
> >> > Any ideas why the current is so low with the LM317? Only modification
> >> > I made to the datasheet schematic was I used a 10uF electrolytic
> >> > instead of a 1uF.
>
> >> > Thanks,
>
> >> > Michael
>
> >> The LM317 will set the voltage. If the battery is already charged, it
> >> won't
> >> take much current at 7.2V.
>
> >> So, first discharge the battery, then try it again.
>
> >> I've looked around on the internet, and seems to me that you really want
> >> to
> >> be charging the thing at the 'float voltage' of 6.75V. If you set the
> >> LM317
> >> to output 6.75V, and just leave it on there, it'll float up the right
> >> charge
> >> level after a day or so. You can also just leave the battery on the
> >> charger
> >> forever at this voltage, which is a plus.
>
> >> The datasheet gives the formula for deriving voltage output. The thing
> >> basically tries to keep 1.25V between its output and adj pins. So, pick a
> >> resistor to go between the out and adj pins, and then find another one to
> >> go
> >> between adj and ground that is nearest to 5.4 times the first resistor
> >> value.
>
> >> Regards,
> >> Bob Monsen
>
> > Thank you for the information.
>
> > Could you provide the links that point to a 6.75V charge?
>
> > Thanks,
>
> > Michael
>
> http://www.jaycar.com.au/images_uploaded/slabatts.pdf
>
> Regards,
> Bob Monsen
<mrdarrett@gmail.com> wrote in message
news:ae82ec44-fa48-4be4-880b-64cb3666901f@i29g2000prf.googlegroups.com...
> On Mar 17, 12:24 pm, "Bob Monsen" <rcmon...@gmail.com> wrote:
>> <mrdarr...@gmail.com> wrote in message
>>
>> news:6c8e287b-fd85-4fb8-bff5-23a1c3e0bcfc@h11g2000prf.googlegroups.com...
>>
>>
>>
>> > 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
>>
>> > Ok, I built it. Didn't have a 5k pot handy, so I strung up two 1k
>> > resistors in parallel and a bunch of 100 ohm resistors in series until
>> > I got about 7.2V out.
>>
>> > Hooked it up to the battery, and I was surprised to see only 50mA
>> > going through the battery. Typically, without the LM317 I got 100+ mA
>> > going through.
>>
>> > LM317 was cool to the touch (with heatsink).
>>
>> > I thought my power supply was underpowered, so I tried a 12V wall wart
>> > (about 14V with no load) instead. But then, after going through the
>> > LM317, voltage going to the battery was just over 7.2V. Not
>> > comfortable with that, so I went back to my 6V power supply.
>>
>> > Any ideas why the current is so low with the LM317? Only modification
>> > I made to the datasheet schematic was I used a 10uF electrolytic
>> > instead of a 1uF.
>>
>> > Thanks,
>>
>> > Michael
>>
>> The LM317 will set the voltage. If the battery is already charged, it
>> won't
>> take much current at 7.2V.
>>
>> So, first discharge the battery, then try it again.
>>
>> I've looked around on the internet, and seems to me that you really want
>> to
>> be charging the thing at the 'float voltage' of 6.75V. If you set the
>> LM317
>> to output 6.75V, and just leave it on there, it'll float up the right
>> charge
>> level after a day or so. You can also just leave the battery on the
>> charger
>> forever at this voltage, which is a plus.
>>
>> The datasheet gives the formula for deriving voltage output. The thing
>> basically tries to keep 1.25V between its output and adj pins. So, pick a
>> resistor to go between the out and adj pins, and then find another one to
>> go
>> between adj and ground that is nearest to 5.4 times the first resistor
>> value.
>>
>> Regards,
>> Bob Monsen
>
>
> Thank you for the information.
>
> Could you provide the links that point to a 6.75V charge?
>
> Thanks,
>
> Michael
On Mar 17, 12:24 pm, "Bob Monsen" <rcmon...@gmail.com> wrote:
> <mrdarr...@gmail.com> wrote in message
>
> news:6c8e287b-fd85-4fb8-bff5-23a1c3e0bcfc@h11g2000prf.googlegroups.com...
>
>
>
> > 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
>
> > Ok, I built it. Didn't have a 5k pot handy, so I strung up two 1k
> > resistors in parallel and a bunch of 100 ohm resistors in series until
> > I got about 7.2V out.
>
> > Hooked it up to the battery, and I was surprised to see only 50mA
> > going through the battery. Typically, without the LM317 I got 100+ mA
> > going through.
>
> > LM317 was cool to the touch (with heatsink).
>
> > I thought my power supply was underpowered, so I tried a 12V wall wart
> > (about 14V with no load) instead. But then, after going through the
> > LM317, voltage going to the battery was just over 7.2V. Not
> > comfortable with that, so I went back to my 6V power supply.
>
> > Any ideas why the current is so low with the LM317? Only modification
> > I made to the datasheet schematic was I used a 10uF electrolytic
> > instead of a 1uF.
>
> > Thanks,
>
> > Michael
>
> The LM317 will set the voltage. If the battery is already charged, it won't
> take much current at 7.2V.
>
> So, first discharge the battery, then try it again.
>
> I've looked around on the internet, and seems to me that you really want to
> be charging the thing at the 'float voltage' of 6.75V. If you set the LM317
> to output 6.75V, and just leave it on there, it'll float up the right charge
> level after a day or so. You can also just leave the battery on the charger
> forever at this voltage, which is a plus.
>
> The datasheet gives the formula for deriving voltage output. The thing
> basically tries to keep 1.25V between its output and adj pins. So, pick a
> resistor to go between the out and adj pins, and then find another one to go
> between adj and ground that is nearest to 5.4 times the first resistor
> value.
>
> Regards,
> Bob Monsen
Thank you for the information.
Could you provide the links that point to a 6.75V charge?
Thanks,
Michael
Reply by Bob Monsen●March 17, 20082008-03-17
<mrdarrett@gmail.com> wrote in message
news:6c8e287b-fd85-4fb8-bff5-23a1c3e0bcfc@h11g2000prf.googlegroups.com...
> 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
>
>
>
> Ok, I built it. Didn't have a 5k pot handy, so I strung up two 1k
> resistors in parallel and a bunch of 100 ohm resistors in series until
> I got about 7.2V out.
>
> Hooked it up to the battery, and I was surprised to see only 50mA
> going through the battery. Typically, without the LM317 I got 100+ mA
> going through.
>
> LM317 was cool to the touch (with heatsink).
>
> I thought my power supply was underpowered, so I tried a 12V wall wart
> (about 14V with no load) instead. But then, after going through the
> LM317, voltage going to the battery was just over 7.2V. Not
> comfortable with that, so I went back to my 6V power supply.
>
> Any ideas why the current is so low with the LM317? Only modification
> I made to the datasheet schematic was I used a 10uF electrolytic
> instead of a 1uF.
>
> Thanks,
>
> Michael
The LM317 will set the voltage. If the battery is already charged, it won't
take much current at 7.2V.
So, first discharge the battery, then try it again.
I've looked around on the internet, and seems to me that you really want to
be charging the thing at the 'float voltage' of 6.75V. If you set the LM317
to output 6.75V, and just leave it on there, it'll float up the right charge
level after a day or so. You can also just leave the battery on the charger
forever at this voltage, which is a plus.
The datasheet gives the formula for deriving voltage output. The thing
basically tries to keep 1.25V between its output and adj pins. So, pick a
resistor to go between the out and adj pins, and then find another one to go
between adj and ground that is nearest to 5.4 times the first resistor
value.
Regards,
Bob Monsen
Reply by ●March 17, 20082008-03-17
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
Ok, I built it. Didn't have a 5k pot handy, so I strung up two 1k
resistors in parallel and a bunch of 100 ohm resistors in series until
I got about 7.2V out.
Hooked it up to the battery, and I was surprised to see only 50mA
going through the battery. Typically, without the LM317 I got 100+ mA
going through.
LM317 was cool to the touch (with heatsink).
I thought my power supply was underpowered, so I tried a 12V wall wart
(about 14V with no load) instead. But then, after going through the
LM317, voltage going to the battery was just over 7.2V. Not
comfortable with that, so I went back to my 6V power supply.
Any ideas why the current is so low with the LM317? Only modification
I made to the datasheet schematic was I used a 10uF electrolytic
instead of a 1uF.
Thanks,
Michael
Reply by Rich Grise●March 11, 20082008-03-11
On Sun, 09 Mar 2008 21:17:03 -0700, mrdarrett 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?
Put a voltmeter on it, and connect the wall wart directly to the
battery || voltmeter. Sit and watch it. When it reaches ~7.2 volts,
disconnect the wall wart, let the battery cool, check the
voltage, and if it's 6.6V or more, you're good to go.
Good Luck!
Rich
Reply by gearhead●March 11, 20082008-03-11
On Mar 11, 10:29=A0am, mrdarr...@gmail.com wrote:
> On Mar 11, 9:34 am, gearhead <nos...@billburg.com> wrote:
>
>
>
>
>
> > On Mar 10, 9:05 pm, mrdarr...@gmail.com wrote:
>
> > > On Mar 10, 10:39 am, gearhead <nos...@billburg.com> wrote:
>
> > > > On Mar 10, 10:04 am, mrdarr...@gmail.com wrote:
>
> > > > > On Mar 10, 9:57 am, "Bob Monsen" <rcmon...@gmail.com> wrote:
>
> > > > > > "Bob" <b...@mailinator.com> wrote in message
>
> > > > > >news:1dc6c3ed-94e3-4b00-aaf0-f1338f75f79e@m44g2000hsc.googlegroup=
s.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.googlegr=
oups.com...
>
> > > > > > >> >I bought a 6V, 6Ah battery from Home Depot to power my 3-yea=
r-old's
> > > > > > >> > toy electric car (the kind that a kid can ride). =A0The pre=
vious battery
> > > > > > >> > didn't hold a charge when I bought the car.
>
> > > > > > >> > One reference from batteryuniversity.com mentioned somethin=
g about
> > > > > > >> > 2.50V per cell for SLA batteries. =A0I'm assuming my batter=
y has 3
> > > > > > >> > cells. =A0Another website mentions use of an L200 voltage r=
> > > > > > >> > circuit.
>
> > > > > > >> > How should I charge it?
>
> > > > > > >> > Thanks,
>
> > > > > > >> > Michael
>
> > > > > > >> You can probably use your 6VDC wall wart. Unless it is a real=
ly hefty
> > > > > > >> wart,
> > > > > > >> it'll probably droop considerably when subjected to the batte=
ry. 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 seri=
es 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,
> > > > > > >> =A0Bob Monsen
>
> > > > > > > Bad idea, Michael the OP has stated that it produces 9V off lo=
ad.
> > > > > > > The current drawn by the battery drops as it charges.
>
> > > > > > Do you know how much the current drops?
>
> > > > > Current dropped from 177 mA @6.42V to 140mA @ 6.63V about 90 minut=
es
> > > > > later. =A0After that I just took voltage measurements only.
>
> > > > > What will happen if I charge with my (underpowered?) wall-wart, ju=
st
> > > > > watching until voltage reaches 7.5V? =A0I'm in no particular hurry=
, and
> > > > > can monitor the voltage every hour if necessary, at least for now.=
> > > > > I'm guessing the reason for the 500mA is for a faster charge? =A0O=
r is
> > > > > this necessary for the health of the SLA?
>
> > > > > Thanks for the circuit,
>
> > > > > MD
>
> > > > You seem to know what you're doing, monitoring the voltage and
> > > > current.
> > > > SLA's have a charging protocol that goes in three stages: =A0bulk,
> > > > absorption and float. =A0If the battery has discharged a substantial=
> > > > amount of its capacity and you put it on to charge it will pull a lo=
t
> > > > of current and draw down the voltage of the charger. =A0It pulls dow=
n
> > > > the voltage of the charger either because the charger has a designed=
-
> > > > in current limit or because of the charger's output impedance -- for=
> > > > example, your wall wart can only put out a certain amount of current=
> > > > (it has an output impedance). =A0All good and well, it means your
> > > > transfomer is small enough not to boil the battery right off the bat=
!
> > > > (Some manufacturers recommend initial charging current limit for sma=
ll
> > > > SLA's around .3 C, or 1.8 amps for your battery).
> > > > Then as the battery takes on bulk charge, the voltage rises. =A0With=
a
> > > > properly regulated charger, this plateau will be somewhere around 2.=
4
> > > > to 2.5 volts. =A0For an SLA, 2.5 is not too high. =A0This is the
> > > > "absorption" stage. =A0The charger holds the voltage steady at the
> > > > setpoint. =A0Gradually, the current drawn by the battery begins to
> > > > decline. =A0When it reaches about .03 C (180 mA), the battery is
> > > > considered charged and a "smart charger" will drop the voltage to
> > > > float, about 2.2 or 2.3 volts per cell.
> > > > Your wall wart won't behave is such a precise and predictable way, b=
ut
> > > > it will work fine to charge your battery as long as you monitor it.
> > > > Such an unregulated charger only poses a danger to your battery if y=
ou
> > > > leave it on indefinitely, because the batttery will take on so much
> > > > charge that it will draw negligible current, causing your charger to=
> > > > approach its open-circuit voltage, which is too high for the battery=
.
> > > > Just disconnect before it happens.
>
> > > Yesterday I charged the battery for 6 hrs, and the voltage when
> > > charging
> > > ranged from 6.42V to 6.77V after 6 hrs.
>
> > > Today I resumed charging, and discovered something weird: =A0the volta=
ge
> > > rose,
> > > then fell, during charging.
>
> > > 6.58V @ 7pm
> > > 6.86V @ 7:2pm
> > > 6.83V @ 7:28pm
> > > 6.82V @ 7:35pm
> > > 6.81V @ 7:40pm
> > > 6.82V @ 8:35pm
> > > 6.84V @ 9pm
>
> > > In general, is it better or worse for the battery's health to split
> > > charging across
> > > several days?
>
> > > Thanks,
>
> > > Michael- Hide quoted text -
>
> > > - Show quoted text -
>
> > I wouldn't think a few hundredths of a volt is symptomatic of
> > anything.
> > Another thing about those voltages in your chart -- they're pretty
> > low, closer to float voltage than charging voltage.
> > The voltage figures would have more meaning if you had also recorded
> > the current draw. =A0What was the state-of-charge of your battery when
> > you recorded those voltages, and did you have a resistor in series?
>
> Current was just over 100 mA at end of charging (I stopped at 6.97V,
> bedtime again).
>
> Battery history:
>
> 1) bought 6V, 6.5Ah battery from Home Depot for $21
> 2) charged to about 6.7 V
> 3) 3-year-old daughter drove the car from home to the park (3 blocks
> away), then back home
> 4) charged to 6.77V over 6 hrs
> 5) charged again to 6.97V over 4 hours (where I got the above
> readings).
>
> No resistor; I figured I need all the power my little wal-wart can
> give without impeding anything. =A0To measure current I'd manually
> disconnect, connect DMM in series, then re-connect.
>
> Michael- Hide quoted text -
>
> - Show quoted text -
I'd say you've got it pretty much under control.
Reply by ●March 11, 20082008-03-11
On Mar 11, 9:34 am, gearhead <nos...@billburg.com> wrote:
> On Mar 10, 9:05 pm, mrdarr...@gmail.com wrote:
>
>
>
> > On Mar 10, 10:39 am, gearhead <nos...@billburg.com> wrote:
>
> > > On Mar 10, 10:04 am, mrdarr...@gmail.com wrote:
>
> > > > On Mar 10, 9:57 am, "Bob Monsen" <rcmon...@gmail.com> wrote:
>
> > > > > "Bob" <b...@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?
>
> > > > Current dropped from 177 mA @6.42V to 140mA @ 6.63V about 90 minutes
> > > > later. After that I just took voltage measurements only.
>
> > > > What will happen if I charge with my (underpowered?) wall-wart, just
> > > > watching until voltage reaches 7.5V? I'm in no particular hurry, and
> > > > can monitor the voltage every hour if necessary, at least for now.
> > > > I'm guessing the reason for the 500mA is for a faster charge? Or is
> > > > this necessary for the health of the SLA?
>
> > > > Thanks for the circuit,
>
> > > > MD
>
> > > You seem to know what you're doing, monitoring the voltage and
> > > current.
> > > SLA's have a charging protocol that goes in three stages: bulk,
> > > absorption and float. If the battery has discharged a substantial
> > > amount of its capacity and you put it on to charge it will pull a lot
> > > of current and draw down the voltage of the charger. It pulls down
> > > the voltage of the charger either because the charger has a designed-
> > > in current limit or because of the charger's output impedance -- for
> > > example, your wall wart can only put out a certain amount of current
> > > (it has an output impedance). All good and well, it means your
> > > transfomer is small enough not to boil the battery right off the bat!
> > > (Some manufacturers recommend initial charging current limit for small
> > > SLA's around .3 C, or 1.8 amps for your battery).
> > > Then as the battery takes on bulk charge, the voltage rises. With a
> > > properly regulated charger, this plateau will be somewhere around 2.4
> > > to 2.5 volts. For an SLA, 2.5 is not too high. This is the
> > > "absorption" stage. The charger holds the voltage steady at the
> > > setpoint. Gradually, the current drawn by the battery begins to
> > > decline. When it reaches about .03 C (180 mA), the battery is
> > > considered charged and a "smart charger" will drop the voltage to
> > > float, about 2.2 or 2.3 volts per cell.
> > > Your wall wart won't behave is such a precise and predictable way, but
> > > it will work fine to charge your battery as long as you monitor it.
> > > Such an unregulated charger only poses a danger to your battery if you
> > > leave it on indefinitely, because the batttery will take on so much
> > > charge that it will draw negligible current, causing your charger to
> > > approach its open-circuit voltage, which is too high for the battery.
> > > Just disconnect before it happens.
>
> > Yesterday I charged the battery for 6 hrs, and the voltage when
> > charging
> > ranged from 6.42V to 6.77V after 6 hrs.
>
> > Today I resumed charging, and discovered something weird: the voltage
> > rose,
> > then fell, during charging.
>
> > 6.58V @ 7pm
> > 6.86V @ 7:2pm
> > 6.83V @ 7:28pm
> > 6.82V @ 7:35pm
> > 6.81V @ 7:40pm
> > 6.82V @ 8:35pm
> > 6.84V @ 9pm
>
> > In general, is it better or worse for the battery's health to split
> > charging across
> > several days?
>
> > Thanks,
>
> > Michael- Hide quoted text -
>
> > - Show quoted text -
>
> I wouldn't think a few hundredths of a volt is symptomatic of
> anything.
> Another thing about those voltages in your chart -- they're pretty
> low, closer to float voltage than charging voltage.
> The voltage figures would have more meaning if you had also recorded
> the current draw. What was the state-of-charge of your battery when
> you recorded those voltages, and did you have a resistor in series?
Current was just over 100 mA at end of charging (I stopped at 6.97V,
bedtime again).
Battery history:
1) bought 6V, 6.5Ah battery from Home Depot for $21
2) charged to about 6.7 V
3) 3-year-old daughter drove the car from home to the park (3 blocks
away), then back home
4) charged to 6.77V over 6 hrs
5) charged again to 6.97V over 4 hours (where I got the above
readings).
No resistor; I figured I need all the power my little wal-wart can
give without impeding anything. To measure current I'd manually
disconnect, connect DMM in series, then re-connect.
Michael