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groingo
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# Posted: 11 Oct 2012 09:55pm
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Looking to upgrade my 12 volt battery charger from a 10 amp to a 15 amp.
Question: For a 12 volt 15 amp charger, what would the INPUT POWER wattage be at 120 volts, not OUTPUT....INPUT WATTAGE?
I am getting a ton of conflicting information.
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Rob_O
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# Posted: 11 Oct 2012 10:26pm
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Depends on the charger
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MtnDon
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# Posted: 11 Oct 2012 10:29pm
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Depends on the efficiency of the unit. There is no hard and fats rule as far as I know.
I can vouch for the performance numbers of the Iota brand of charger. I have a 55 amp that the specs state: Maximum AC Current @ 108VAC 13.4 Amps. That's 1447 watts input. I have measured an input of 1400 watts using my Kill-A-Watt meter. That charger has a rated max output of 750 watts. That is an efficiency of around 50%; probably more or less normal or average.
So if a charger can put out 15 amps that would be about 200 watts more or less.... So input about 400 watts.
How's that compare?
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MtnDon
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# Posted: 11 Oct 2012 10:30pm
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So for 15 amps charging current... is the battery being charged rated at 120 to 150 amp-hours?
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TomChum
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# Posted: 11 Oct 2012 10:31pm - Edited by: TomChum
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In my opinion 15A is a paltry rate. I would get a modern, fully automatic charger that can pump out 40A. The Sears unit has (I think) 3 levels, 5A, 15A, 40A choices. And a car-start feature, and also can tune-up your batteries.
Theres a buzzword for this feature but it escapes me at the moment.
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MtnDon
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# Posted: 11 Oct 2012 10:41pm - Edited by: MtnDon
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Quoting: TomChum tune-up your batteries.... ... Theres a buzzword for this feature but it escapes me at the moment.
desulfate??? I've seen varying reports on whether or not that really works well. More important, IMO, is that proper battery use and care will prevent sulfating and premature battery death. The maximum charge rate should not exceed C/8 to C/10 where C = battery amp hour capacity. The reasoning is that higher rates can overheat the battery and that is not good for long life. Once in a while a shock charge may not noticeably cause problems but I wouldn't do it all the time.
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groingo
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# Posted: 12 Oct 2012 12:01am
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I was looking at a Stanley that had the De-sulfating / Reconditioning feature but I am more interested in efficiency at this point and it showed 80 to 90% at an input wattage of 250 watts....there you see my paradox.
I am charging a pair of 6 volts run in tandem for 12 totaling 225 amp hours and never let them get below 60%.
I already tested (Kill A Watt) on a Schumacher 15 amp and it put out only 12 amps on a dead battery.
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MtnDon
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# Posted: 12 Oct 2012 12:23am - Edited by: MtnDon
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You'd be better off with a 25 to 30 amp charger for 225 amp-hours of battery capacity.
Iota 30 amp DLS
The one with the IQ4 is the best. 4 stage charger (if left plugged in over time it floats and then equalizes on an automatic schedule. ) (meant for wet cell, not AGM type battery)
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TomChum
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# Posted: 12 Oct 2012 10:14am - Edited by: TomChum
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Quoting: MtnDon Quoting: TomChum tune-up your batteries.... ... Theres a buzzword for this feature but it escapes me at the moment. desulfate???
Yes thank you, and Equalize too.
My understanding was that you would desulfate maybe once a year, after the batteries are a few years old. It causes a LOT of action in the battery for a short time, and presumably the extra bubbling has some benefits. Or to revive a battery that's acting old. I have done this, brought a battery back from the dead. I don't know how long it lasted after that.
I think "equalization" is a special programmed 'desulfation' sequence. If not, I can't guess what else it might be doing. But anyway my inverter has that feature and they recommend to equalize a battery bank monthly.
Quoting: groingo I already tested (Kill A Watt) on a Schumacher 15 amp and it put out only 12 amps on a dead battery.
A battery charger can't really put out more than the battery is willing to accept at that moment, and it changes during the charging cycle. When the battery is dead it could resist almost all the input. If it's going to charge at all, it has to accept some though, and if it is accepting 12A, then at some point in the cycle it should be accepting everything the charger can put out, which could be up to 20A.
Kill-a-Watt measures the 120vAC input. How did the KAW inform you of the 12A output?
That IOTA unit is a nice unit. $150 bucks though. I bet's its worth its weight in lead (batteries). Looks like a great unit for long-life of a battery bank while on-the-grid. For off-the grid though I'd have one that get it charged ASAP (if necessary).
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MtnDon
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# Posted: 12 Oct 2012 01:23pm - Edited by: MtnDon
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Quoting: TomChum My understanding was that you would desulfate maybe once a year, after the batteries are a few years old. It causes a LOT of action in the battery for a short time, and presumably the extra bubbling has some benefits. Or to revive a battery that's acting old. I have done this, brought a battery back from the dead. I don't know how long it lasted after that. I think "equalization" is a special programmed 'desulfation' sequence. If not, I can't guess what else it might be doing. But anyway my inverter has that feature and they recommend to equalize a battery bank monthly.
I posted a note on sulfation, desulfating and equalization over HERE today as my opinion on these differ from some of the other expressed opinions. Do with it what you want.
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groingo
Member
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# Posted: 12 Oct 2012 06:51pm - Edited by: groingo
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Looks like I'll stay with the old charger, nothing digital so it will keep pumping ten amps in till I tell it to stop, plus I am using about 1/2 the power in a day I had planned on so charging can easily be stretched to every two days.
Got a new hydrometer and volt meter so things are looking much better.
If all goes according to plan my daily energy cost from PSE is 31 cents a day, using the Yamaha to recharge bayyeries at $4.00 a gallon should bring me to 40 cents a day but if I convert over to Propane at 2.49 a gallon adding 10% for brings it to 29 cents a day....definitely a cost effective way to go but in the end I will add 25% just be realistic and it still pencils out pretty good, only time will tell.
Appreciate the feedback from all.
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