wsh@hou5f.UUCP (Willie Heck) (07/25/83)
Please forgive me for posting this to net.auto as well as net.rec.boat,
but I thought the answer to this problem would be likely to be answered there.
For use on my boat, I have what is known as a deep discharge battery.
(This differs from a regular automobile battery in that it is meant to supply
a charge over a long period of time and to be recharged many times from a
nearly discharged state.) Depending on how much sailing I do at night,
however, the battery sometimes goes for long periods of time without any
use at all. This is not good for the battery; it must be discharged from
time to time and then recharged. My question is: what is the best way to
do this? Should I just attach a 12 volt headlight to the battery and run
it until it dims, and then recharge the battery?
Please reply over the net, as I will be moving to a new machine next
week. If you want to send mail, my return address is
ariel!hou5f!wsh, until I move, after which it will be
ariel!hou5g!wsh.
Thank you,
Willie Heck
abi - holmdel
(201) 834-3376wookie@alice.UUCP (07/25/83)
I think we had better find a battery expert here at Murray Hill for this battery question. It is my understanding that a lead acid battery is best kept fully charged at all times. From time to time if it is unused it should be trickle charged at a very low current (<1 amp?) every couple of weeks. A lead acid battery left at some discharged level will build up hard sulfate on the plates which is not easily converted back to lead peroxide and lead and thus the capacity is reduced. My experience with nickle cadmium batteries however indicates that they are best stored in a discharged state (this info came directly from engineers at General Electric) and that they should be fully cycled from complete charge to complete discharge. Ni-cads exhibit a memory for the amount they are used. If you use you battery grass trimmers for 20 minutes and then leave it on the charger the rest of the week, eventually they will only run for 20 minutes and then die completely. They also tend to crystalize if left on the charger all the time and will not work at all unless you zap them with a very high current for a short period of time (seconds) to break down the crystals. WARNING: This is a dangerous practice as the battery can explode throwing potassium hydroxide all over the place! Anyway in conclusion from what I have read it is best to keep a lead acid battery fully charged at all times and the less you cycle it the longer it will last. A Ni-cad should be fully and deeply cycled or stored in a discharged state. Any experts out there on this subject?? Keith Bauer White Tiger Racing
fred@umcp-cs.UUCP (08/02/83)
From: wookie@alice.UUCP Ni-cads . . . tend to crystalize if left on the charger all the time and will not work at all unless you zap them with a very high current for a short period of time (seconds) to break down the crystals. WARNING: This is a dangerous practice as the battery can explode throwing potassium hydroxide all over the place! Keith Bauer White Tiger Racing I once sucessfully revived my rechargeable ni-cad electronic flash unit by doing just this. I used a small capacitor (about 30 mfd.), charged it from the flash unit's recharger, then touched it to the terminals of the flash unit, but with the polarity reversed. It's now accepting a full charge, just like new. I imagine that doing this with a much larger battery could well be dangerous, but there doesn't seem to be much danger with the small (C-cell size) batteries in a portable flash unit. Besides: no one warned me. I suppose that another safety factor is that the total charge in the capacitor is extremely limited, so the reverse current will only flow for a fraction of a second, not long enough to cause an explosion.