How long would it take to charge a dead 12 volt battery?
491374
Hard to say exactly because it depends on the intensity of the sun. I charged up mine totally in two full sun days.
491375
At 5 watts this charger can produce a max current of ~0.4A: I(A) = P(W) / V(V)So every hour, it can provide 0.4 Ah (amp hours) of charge. Batteries come in all sorts of capacities, and are rated in Ah (amount of hours it can deliver one Amp of current.) So to calculate this you can estimate at about 2.5 hours for each Ah of battery capacity. If if you have a typical 50Ah battery it would take 121 hours of sun to deliver a full charge. This is not factoring in any inefficiencies of the charger, battery, or normal drain over the extended charging time.
491376
Without knowing what the Amp of the battery is I cant tell you for certain. One amp =(approximately) 100 watts. Do the math to extrapolate your battery's capacity. Remember, this unit is for maintenance, not full charge so, take it from there. IF your battery is completely dead (use a voltmeter) then it will not be capable of being recharged.
119866
If it is a 12 volt battery this charger should work fine. I would start the charger for about 7-8 minutes at 40 amps, then turn it down to 10 amps for about 3 hrs. The 40 amp rate is to sort of shock the battery, then a slow charge for the next 3 hrs. If the battery doesn't show taking a charge after the 7-8 minute 40 amp charge, it might be bad. You could turn it up to the 200 amp charge for about 30 seconds, then turn to 40 amps to see if it is charging. If it is, after the 7-8 minute charge, then turn it to 10 amps.
229972
No... but if you are talking about a battery that had the lights left on overnight and 'dead' it will not charge if it is below (I think 2 volts) some minimum voltage left in the battery. It IS very frustrating because the older 'not so smart' chargers would at least try to charge a dead battery where these smart ones won't work at all. I faked one out once by connecting a small motorcycle battery to my dead car battery and fooled the 'smart charger' to start working and then put the motorcycle battery back. Battery was fine after about 6-8 hours of charging.
2115091
No don't reverse polarity. This is only a trickle charger it maintains your battery charge when in storage or not used for long periods of time. If your battery is dead you need a full recharge with a regular charger that puts out 12v. It will take 6 to 8 hours to charge. Sometimes when your battery is dead it will not hold a charge because the battery plates have shorted out.
146785
It takes more than the voltage capacity of the battery to charge it. So 12 volts charges the 3.7 volt battery.
2150963
There is a light on the charger that changes color when the battery is fully charged. Usually, if the battery was totally discharged it will take one to two hours to fully charge.
321574
I'm not quite sue--I've never used it long enough to drain a charge. My guess would be several hours. Sorry I can't be more helpful.
165505
I am not really sure, i have a total of 3 batteries, so when/if one goes dead, i just pop it in the charger and it stays till i need it again. My android phone takes a while to charge, even on its own w/o any apps running. My guess it takes about 3 hours from completely dead to charge.
564280
The plug-in charger, which comes with the battery box, has a red LED which should comes on when the battery is charged. The charger is not much larger than the ones used for a cell phone. The initial charge may take a couple of days, after that, only a couple of hours. The 12 volt battery is similar in design to the batteries used in motorcycles and ATVs.
1767669
It depends on how low the battery level is. If you are charging it from 0 then it will take about 1.5-2 hours.
1858087
Send it back! It takes around 4 hours to charge mine from dead to fulling charged.
2069243
Only if it is12v led. The battery is pretty stout, but you only have 12 ah (amps per hour). With that said you will have to calculate the rate it will drain the battery.DC watts to amps calculation formulaThe current I in amps (A) is equal to the power P in watts (W), divided by the voltage V in volts (V):I(A) = P(W) / V(V)So amps are equal to watts divided by volts.amp = watt / volt12 = 144w / 12vMax run time on a perfect charge/battery 12 hrs.
1614671
It will take several days if they are severely drained. Only because they are designed to charge slowly for a deep charge. My trailer batteries are 6 volt deep cycle and take several days to charge.
720193
Unless it is defective, it should charge a dead car battery within milliseconds of being connected! You could put an ammeter in the charging circuit and it should indicate 1.5 amps ("+ or - small measurement error") current flow almost instantaneously after turning it on. To FULLY charge a 60 amp-hour capacity battery that is commencing from a near-fully-discharged state (adding in something like a 50% factor for heat loss and other inefficiencies), it would take:(60 amp-hours) / (1.5 amp) = 40 hours... Adding the 50% 'fudge factor', take you up to about 60 hours (about 2.5 days). Unless it is defective, it should charge a dead car battery within milliseconds of being connected! You could put an ammeter in the charging circuit and it should indicate 1.5 amps ("+ or - small measurement error") current flow almost instantaneously after turning it on. To FULLY charge a 60 amp-hour capacity battery that is commencing from a near-fully-discharged state (adding in something like a 50% factor for heat loss and other inefficiencies), it would take:(60 amp-hours) / (1.5 amp) = 40 hours... Adding the 50% 'fudge factor', take you up to about 60 hours... » Read More Unless it is defective, it should charge a dead car battery within milliseconds of being connected! You could put an ammeter in the charging circuit and it should indicate 1.5 amps ("+ or - small measurement error") current flow almost instantaneously after turning it on. To FULLY charge a 60 amp-hour capacity battery that is commencing from a near-fully-discharged state (adding in something like a 50% factor for heat loss and other inefficiencies), it would take:(60 amp-hours) / (1.5 amp) = 40 hours... Adding the 50% 'fudge factor', take you up to about 60 hours (about 2.5 days). « Show Less
1338585
I hard charge my battery everytime...overnight. I suspect it would take a full 8 hours. I also carry a second battery with me....never want to be caught out with a dying battery 25 miles from home.
1252353
It didn't take that long to charge my new battery. I would think a few hours would be good. Maybe you got a new battery that was bad?? Hope this helps...
634596
I charge mine 24 hours once every 2 or 3 weeks when it gets slow. Even if it is dead it should pick up enough charge to run within 30 to 60 minutes. If not either the charger is not charging or the handle is not taking the charge. These are cheap enough it is more cost effective to replace than repair if anything is failing.