On Sat, Dec 14, 2002 at 12:23:32PM +1100, Allan Benson wrote:
> I took it back to Battery World and they found no problem with the
> battery or the recharger. After a long conversation with the very
> helpful salesperson I discovered the plug in recharger will not or
> will have trouble recharging the battery if the charge in the battery
> has less than about 10 V charge remaining. This means that once the
> spotlight starts to dim it is wise to stop using it and recharge the
> battery. I had run down the battery thinking the battery had
> "memory". I know now that this concept only applies to nicad type
> batteries.
Yep, you should not discharge 12V lead-acid batteries below about 11.5V.
Typically about this voltage a spotlight become noticeably dimmer and
yellower. While I'm giving unasked-for-advice. If you are transporting
lead-acid batteries be very careful to ensure that the terminals can't
short. Something metal touching both terminals would produce intense
heat, would destroy the battery and likely start a fire. Covering the
battery terminals with electrical tape is a good precaution. A roll of
electrical tape is handy in your field kit anyway e.g. if you are going
out at night its good to tape up any connection that might come loose.
You should recharge lead-acid batteries before storing them -
i.e. recharge them the day after your spotlighting trip not in 6 months
time. They self-discharge over a period of months so you'll still may
need to recharge them before use - but they last long if stored charged.
They also last longer stored somewhere that doesn't get hot.
I don't want to start an argument about NiCD batteries but I wouldn't
normally fully discharge them either. A 1.2V NiCd cell should not
normally be discharged below 1V. This is a common cause of damaged
NiCds. Overcharging is another - so follow the charger's instructions.
Although many people will tell you otherwise, you are unlikely to
encounter any sort of "memory effect" with NiCds. But a deep discharge
can partly remedy other problems that occur with NiCds, particularly some
associated with overcharging. But I wouldn't do it, unless the NiCd cell
had obvious problems i.e. had an apparent capcity far less than normal.
If you are using batteries a lot, buying a multimeter to check their
voltage is worthwhile. Jaycar sell basic multimeters for under $20.
Andrew
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