 |
Search Sci.Electronics.Basics |
|
|
|
|
|
|
 |
|
|
Sci.Electronics.Basics -> So, how DO I charge a 6V SLA battery?
There are 27 messages in this thread.
You are currently looking at messages 20 to 27.
|
|
|
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
|
|
|
|
Author: Bob MonsenDate: 15:24 17-03-08
|
|
<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
|
|
|
|
|
|
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
|
|
|
|
Author: Bob MonsenDate: 15:33 17-03-08
|
|
<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
http://www.jaycar.com.au/images_uploaded/slabatts.pdf
Regards,
Bob Monsen
|
|
|
|
|
|
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.
6.75V http://www.jaycar.com.au/images_uploaded/slabatts.pdf
less than 7.2V (<2.4V/cell) float
http://hss.energy.gov/NuclearSafety/techstds/standard/hdbk1084/hdbk1084.pdf
up to 7.5V (2.5V) for sealed lead acid batteries
http://www.batteryuniversity.com/partone-13.htm
Michael
|
|
|
|
Author: gearheadDate: 17:20 17-03-08
|
|
On Mar 17, 12:42=A0pm, mrdarr...@gmail.com wrote:
> 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=
ting
> > >> >> > chip (http://www.myra-simon.com/bike/charger.html).
>
> > >> >> > I've got a 6VDC (nominal) wall wart that puts out just
over 9V o=
pen-
> > >> >> > 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=
r
> > >> value.
>
> > >> Regards,
> > >> =A0Bob 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,
> > =A0Bob Monsen
>
> Thanks for that. =A0I'm starting to get dizzy with all the different
> voltage recommendations.
>
> 6.75Vhttp://www.jaycar.com.au/images_uploaded/slabatts.pdf
>
> less than 7.2V (<2.4V/cell) floathttp://hss.energy.gov/NuclearSafety/techs=
tds/standard/hdbk1084/hdbk10...
>
> up to 7.5V (2.5V) for sealed lead acid batterieshttp://www.batteryuniversi=
ty.com/partone-13.htm
>
> 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.
|
|
|
|
Author: ehsjrDate: 22:10 17-03-08
|
|
mrdarrett@gmail.com wrote:
> 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
>
> 6.75V http://www.jaycar.com.au/images_uploaded/slabatts.pdf
>
> less than 7.2V (<2.4V/cell) float
> http://hss.energy.gov/NuclearSafety/techstds/standard/hdbk1084/hdbk1084.pdf
>
> up to 7.5V (2.5V) for sealed lead acid batteries
> http://www.batteryuniversity.com/partone-13.htm
>
> Michael
|
|
|
|
|
|
|
|
|
Contact | Electronic Portal
|
|
|
