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

01-01-2007, 04:09 PM

On 30 Dec 2006 20:40:46 -0800, "peter" <prathman@comcast.net> wrote:

>dgk wrote:
>> 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.
>
>You already have a case that holds 8, so buy a holder for two
>additional cells and connect the two battery holders in series so they
>deliver a full 12 VDC. However, you should note that rechargeable
>cells can be damaged if you discharge them to the point where they're
>getting reverse-charged. With 10 cells in series you might have a
>situation where one of the cells may have a little less capacity than
>the others and therefore it goes dead first. Even if the voltage of
>that cells drops to 0, you could still be getting 9 x 1.2 = 10.8 V from
>the other cells which may be enough to keep your device operating. But
>driving that current through the discharged cell will probably damage
>it.
>
>So when using that many cells in series you need to be careful that all
>the cells are well-balanced so they discharge at close to the same
>time. Keep cells purchased together as a set and always fully charge
>them at the same time. Also try to avoid running them to the point
>where they're close to fully discharged.
>>

I did exactly that. I went to RadioShack and got a 2 battery holder
and a few of those 9-volt battery connector things, which is what the
current holder uses. Then I just wired them together and velcored them
physically together. The lights look great.

I bought twelve rechargable AA batteries at the start of the cold(er)
weather and have been using eight for the lights and two for a CD
player. So I took the two from the player and am using them with the
eight, so all ten are around the same wear. The two formerly unused
ones are in the CD player.

They never get drained that much during the ride home, and now the
days are supposedly getting longer again so all should be fine. Once
in a while I discharge them all the way just to keep them honest. The
charger does that.

Thanks for the advice.

01-01-2007, 04:09 PM	#14 (permalink)
dgk Posts: n/a	Re: When 12 volts is not 9.6 volts On 30 Dec 2006 20:40:46 -0800, "peter" <prathman@comcast.net> wrote: >dgk wrote: >> 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. > >You already have a case that holds 8, so buy a holder for two >additional cells and connect the two battery holders in series so they >deliver a full 12 VDC. However, you should note that rechargeable >cells can be damaged if you discharge them to the point where they're >getting reverse-charged. With 10 cells in series you might have a >situation where one of the cells may have a little less capacity than >the others and therefore it goes dead first. Even if the voltage of >that cells drops to 0, you could still be getting 9 x 1.2 = 10.8 V from >the other cells which may be enough to keep your device operating. But >driving that current through the discharged cell will probably damage >it. > >So when using that many cells in series you need to be careful that all >the cells are well-balanced so they discharge at close to the same >time. Keep cells purchased together as a set and always fully charge >them at the same time. Also try to avoid running them to the point >where they're close to fully discharged. >> I did exactly that. I went to RadioShack and got a 2 battery holder and a few of those 9-volt battery connector things, which is what the current holder uses. Then I just wired them together and velcored them physically together. The lights look great. I bought twelve rechargable AA batteries at the start of the cold(er) weather and have been using eight for the lights and two for a CD player. So I took the two from the player and am using them with the eight, so all ten are around the same wear. The two formerly unused ones are in the CD player. They never get drained that much during the ride home, and now the days are supposedly getting longer again so all should be fine. Once in a while I discharge them all the way just to keep them honest. The charger does that. Thanks for the advice.