Cycling Mob: Road Cycling, Mountain Biking and More - View Single Post

12-31-2006, 10:19 AM

Mike Ellis <news@mellis.me.uk> wrote in
news:4596dcc2$0$2754$c3e8da3@news.astraweb.com:

> dgk wrote:
>> I like to use rechargable batteries in my lights, and for the most
>> part using a rechargable AA in place of a regular battery works fine.
>> But with cold cathode bulbs on my bike, the little transformer thing
>> needs 12 volts. So I replaced the normal 8 AAs with 8 rechargables.
>> And it sort of works. But one bulb starts dimming after a half hour
>> or so. Checking with normal batteries, this doesn't happen.
>>
>> I looked a bit closer at my rechargables, which are, it turns out,
>> 1.2 volts, not 1.5 like regular batteries. All rechargables that I
>> looked at are 1.2. So, 8 * 1.2 = 9.6, not 12. Other stuff, like CD
>> players, work fine on the rechargeables, but the cold cathodes have a
>> bit of a problem. Obviously, 10 batteries instead of 8 should do the
>> trick, but I don't have, and can't find, a case that holds 10
>> batteries.
>>
>> So, why do some things work fine with 1.2, and others not? And why
>> aren't rechargeables 1.5?
> Some things work fine whilst others don't because the application
> isn't so voltage critical. It could also be that the internal
> circuitry reduces the input voltage to a lower value so that lower
> voltage cells will work. The reason that rechargeables are only 1.2
> volts is because the chemical reaction only produces 1.2V whereas the
> chemical reaction of regular batteries produces 1.5V. I'm afraid its
> all down to the chemistry.
>
> Mike
>

Why not susbtitute a small sealed lead acid battery, AKA a Gel Cell...

Look at this site:
http://www.zbattery.com/sla.html

Or if you really want to get ceative see:
http://www.powerstream.com/SLA.htm

Richard B.

12-31-2006, 10:19 AM	#8 (permalink)
Richard B Posts: n/a	Re: When 12 volts is not 9.6 volts Mike Ellis <news@mellis.me.uk> wrote in news:4596dcc2$0$2754$c3e8da3@news.astraweb.com: > dgk wrote: >> I like to use rechargable batteries in my lights, and for the most >> part using a rechargable AA in place of a regular battery works fine. >> But with cold cathode bulbs on my bike, the little transformer thing >> needs 12 volts. So I replaced the normal 8 AAs with 8 rechargables. >> And it sort of works. But one bulb starts dimming after a half hour >> or so. Checking with normal batteries, this doesn't happen. >> >> I looked a bit closer at my rechargables, which are, it turns out, >> 1.2 volts, not 1.5 like regular batteries. All rechargables that I >> looked at are 1.2. So, 8 * 1.2 = 9.6, not 12. Other stuff, like CD >> players, work fine on the rechargeables, but the cold cathodes have a >> bit of a problem. Obviously, 10 batteries instead of 8 should do the >> trick, but I don't have, and can't find, a case that holds 10 >> batteries. >> >> So, why do some things work fine with 1.2, and others not? And why >> aren't rechargeables 1.5? > Some things work fine whilst others don't because the application > isn't so voltage critical. It could also be that the internal > circuitry reduces the input voltage to a lower value so that lower > voltage cells will work. The reason that rechargeables are only 1.2 > volts is because the chemical reaction only produces 1.2V whereas the > chemical reaction of regular batteries produces 1.5V. I'm afraid its > all down to the chemistry. > > Mike > Why not susbtitute a small sealed lead acid battery, AKA a Gel Cell... Look at this site: http://www.zbattery.com/sla.html Or if you really want to get ceative see: http://www.powerstream.com/SLA.htm Richard B.