graham@arcturus.uucp (Graham;Thomas D.) (05/14/91)
Got a question re using lead-acid, car battery, as power supply for house alarm system. I'm using a Delco 40 month rated about 20 hrs (?). A typical auto 12v battery. I keep it on a floating charge at about 13v, from a cheap little battery charger. I wanted to check its power reserve/capacity, even though the little green ball indicated full charge, so I discharged it at 4 amps rate. In a little over an hour the voltage had fell to 9 volts. YET, the green ball was still indicating full charge. Is something wrong with this picture??? Is keeping the battery on a charger, at 13 volts, the proper way to maintain it??? Should it be charge/discharged cycled??? Also, it has a sealed (?) top so you can't check the electrolyte level or add water. (But it is probably OK since the green ball looks near the top). Any help appreciated, thanks. Tom Graham.
john@zygot.ati.com (John Higdon) (05/19/91)
In article <1991May14.154859.21874@arcturus.uucp> graham@arcturus.uucp (Graham;Thomas D.) writes: > > Got a question re using lead-acid, car battery, as power supply for > house alarm system. I'm using a Delco 40 month rated about 20 hrs (?). > A typical auto 12v battery. I keep it on a floating charge at about > 13v, from a cheap little battery charger. I wanted to check its > power reserve/capacity, even though the little green ball indicated > full charge, so I discharged it at 4 amps rate. In a little over an > hour the voltage had fell to 9 volts. Maintenance-free batteries were designed for one purpose and one purpose only: for automobiles owned by people who are too lazy to take care of their cars. These batteries have a terrible discharge characteristic in that they cannot tolerate deep discharge nor can they deliver any decent service with a slow discharge. They will start your car and then they want to see charging current at all other times. I found that in my Blazer, leaving the cellular phone on for only a few hours was enough to make the car unstartable. The standby current for the phone is around one amp, but maintenance free batteries fall apart during any amount of prolonged discharge, regardless of how slight. For this reason, these batteries are useless for anything other than automotive service in which the vehicle is regularly used. I have had disappointing results using them on standby generator sets (they don't seem to like constant trickle charging without nearly daily, momentary discharge), terrible results on battery backup systems, and find that they are not all that hot in cars either. Leave your domelight on all night sometime, and see if you don't start having a hard time starting your car from then on. While regular, fillum-yourself batteries typically will last over five years in a car, maintenance free types will max at about three years. Use a gell-cell for your alarm, or a heavy duty, deep-cycle battery. -- John Higdon | P. O. Box 7648 | +1 408 723 1395 john@zygot.ati.com | San Jose, CA 95150 | M o o !
wolfgang@wsrcc.com (Wolfgang S. Rupprecht) (05/21/91)
graham@arcturus.uucp (Graham;Thomas D.) writes: > Got a question re using lead-acid, car battery, as power supply for > house alarm system. I'm using a Delco 40 month rated about 20 hrs > (?). [..] In a little over an hour the voltage had fell to 9 volts. > YET, the green ball was still indicating full charge.e It sure sounds like one or two of the cells are dry or just dead. Probably the cell that has the little green ball is perfectly fine. Try to find the vent caps and open them. Many sealed cells still have a way to get inside with a bit of prying. Check under the "Never Needs Service" label for the service plugs. ;-) I bet you will find that you boiled much of the electrolyte off of a cell or two and this is your problem. Fill these problem cells with water and and charge for a goodly amount of time. -wolfgang -- Wolfgang Rupprecht wolfgang@wsrcc.com (or) uunet!wsrcc!wolfgang Snail Mail Address: Box 6524, Alexandria, VA 22306-0524