| Author | Message | ||
     Xdigitalx |
Just wondering if it could charge that battery alittle faster and won't damage it. I have a 1 amp slow charger (no shutoff) and a battery tender with the green/red light shutoff. (750ma?) haha.. how many hours do you think it would take to charge an 8 month old almost dead automotive battery with one (or both) chargers connected?? thanks | ||
| Etennuly |
A long time.  Putting both chargers on at one time should not hurt anything. The battery is not too smart, it will not know you are using two chargers to ramp all the way up to nearly two amps!  If the battery is in good condition, other than being discharged, it will probably take about eight hours at two amps. But at best that is just a guess. If it has shorted(dirty partially crap filled) cells it will probably climb to about 9 volts (+ - 1V) and never get much higher. | ||
| 86129squids |
IIRC, many "tender" type chargers require that the battery not be below a certain standing voltage to begin- not completely sure though. Vern's prolly right, it'll take a good while at least... he's smarter than he looks anyway.  | ||
| 86129squids |
BTW, I bought a decent Duracell brand charger for cheep last year- it'll charge at 3 different amperages, seems to do a good job so far. I believe Big Lots had them for about what I paid for mine. | ||
| Reepicheep |
One charger will probably just cause the other charger to shut off. At worst, one could fry the other. Like any other committee, two at once will probably screw up what either alone would have done fine, and take any "smart" away from smart charging. | ||
| Skntpig |
If you have access to cables and another batter to use, jump it. Connect both as if you were jump starting and connect the one stronger charger. It will take a while but the good battery will help bring back the discharged one. Squids is right. Sometimes those small chargers won't work but this trick will help them. | ||
| 46champ |
It is true battery tenders will not charge a battery that is completely dead. I know because the battery in the M2 was flat like .75 volt. Got it to charge up with a conventional charger but don't know if it will hold a charge. | ||
| Etennuly |
When I have a flat dead car or truck battery I often hit it at 60 amps for a couple of minutes to get it started, then back off to twenty amps for an hour or so for a quick charge. I have to frequently charge up customer trucks for having dome lights left on or drivers leaving the key in the "on" position when they check their mileage at drop off. If the vehicle will be around for a while I would rather step down the charge for about 8 to 10 hours on two amps, the charge goes deeper and the battery does better at holding the charge. I have a 24V scissor lift that is happier on a 2 amp 24 hour charge that it is a 20 amp charge for 4 hours. I have used two chargers at one time in the past. One would do 8 amps max and the other would do 10 amps. I have also done the jumper from a good battery with a charger on it to keep it's charge while leaking off a charge to the dead battery. It does work for getting a flat dead battery to start taking a charge. | ||
| Just_ziptab |
Batteries and chargers have a damned mind of their own,depending on how bad you need one to work. I have five 12 volt batteries wired to run a 12/120 inverter..to run the furnace for a short term power fail. Smoked a trickle charger on that set up so now I charge them separately and it usually takes less than 20 minutes each to top them off once a month. | ||
| Xdigitalx |
I used a charged motorcycle battery jumped to the dead auto battery, plus the trickle charge for about 5 hrs. Car starts now...but.. prior to me charging.. it would just shut off after a few min of jumping from another vehicle.. I think the alt is finally gone. It is a 2000 Ford Escort, original owner. My back can't take the leaning under the hood otherwise I would replace the alt myself. But it may not be just the alt, could also be just a belt adjustment or some connections, better to get someone who know wtf they doing. Gonna tow it to local shop get looked at. Thanks for the tips. | ||
| Preybird1 |
You should just use a good known battery and wire both together as one battery and hook the charger the negative on the bad battery and the positive on the good battery and the charger will recognize the good battery and actually charge up both but. Only if done correctly. If the battery is to weak like 2 volts or lower it may be to far gone to save. 2 chargers wont do any better if the battery is dead!! |
