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Small Cabin Forum / Off-Grid Living / battery charger question
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rugercpl
Member
# Posted: 13 Jun 2016 20:43
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I've been recharging my batteries with my Honda eu2000i and Schumacher XCS15 battery charger when the sun and solar panels need some help. When the batteries are depleted enough to need recharging, the generator and charger takes a long time to bring the batteries back up to 95% charge..as much as 10 hours.

The Schumacher is a 15amp charger. The Honda genny is rated for about 14 amps.

Excuse my lack of electrical knowledge, but is there a possibility that a Stanley BC2509 25amp charger will recharge my battery bank faster than the Schumaker 15amp....using the eu2000i? Or no because the honda generator is limited to 14 amp output?

MtnDon
Member
# Posted: 13 Jun 2016 21:25 - Edited by: MtnDon
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The Honda EU2000i continuous output is rated at 1600 watts; 1600 watts at 120 volts (AC) = 13.3 amps. Those amps are at 120 VAC. (watts = amps x volts)

The battery charger amperage rating is at about 12 to 14 volts (DC in this case; but volts are volts and amps are amps no matter DC or AC). So a 15 amp charger is putting out about 14 volts x 15 amps = 210 watts, more or less. There is some inefficiency which varies greatly between charger types/brands. Up to a 50% loss from AC to DC.

FYI, best gasoline efficiency is to use the generator to build up the bulk charge and let solar finish off the absorb stage.

In short, proper interpretation of amperage ratings depends on the associated voltage. A rough rule of thumb is a 12 volt device will have a 10X greater amp rating than a 120 volt device for the same amount of power, same number of watts.

Therefore, yes, you can use a higher rated charger to charge the batteries quicker.

How high a capacity depends in part on the amp-hour capacity of the batteries. The batteries should have the amp-hour capacity listed. If you have 2 or more batteries in series the amp-hour rating is what is labeled. If you have batteries in parallel you add the amp-hours. Tell us what you have and how they are connected if you want help with figuring battery capacity.

The maximum amperage of the charger should be approx equal to 10% of the amp-hour capacity. EG, if the battery amp-hours is 220 then you could use a 20 to 25 amp charger.

If you want the best in charging ability you need a charger that is listed as having three stages; bulk, absorb and float. AFAIK, Schumachers are not true multi-stage chargers. The specs should tell.

Iota makes some decent chargers although their standard line have a low power factor (waste power and have a large surge on start up. Samlex makes some very nice multi stage chargers with a higher power factor; lower current surge on start up and make better use of the generator power. Xantrex also has a couple better than average chargers.

FWIW I run a 24 volt 40 amp charger off a Honda EU2000i with no problem at all.

rugercpl
Member
# Posted: 13 Jun 2016 21:48
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I will be testing the Stanley charger out tonight and will report back if it charges faster. From what I got from your post it sounds possible. Thanks

creeky
Member
# Posted: 13 Jun 2016 22:39
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You want to watch your amperage. 200 amps of 12v battery could charge at 20 amps. 400 at 40. Give your batteries a good hard kick, but don't boil 'em.

25a x charge voltage of 14 = 350 watts. Your genny will have no problem. It would push 100 amps. If you had 1000 amp battery pack.

rugercpl
Member
# Posted: 13 Jun 2016 23:50
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So far so good...the charger is reading 25.4amps charging power coming from the generator thru the charger to the battery bank. I don't know what the Schumacher was doing but considering it's a 15amp charger I imagine it was considerably less charging power

rugercpl
Member
# Posted: 14 Jun 2016 05:52
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While this "test" was pretty unscientific....I think I can say the Stanley charger does indeed charge faster than the Schumacher. My bank of (3) 100amp batteries went from 12.1 to 14.1 Volts in under 5 hours whereas this would normally would have taken 8-10 hours previously.

groingo
Member
# Posted: 14 Jun 2016 10:57
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Glad to see you got the Stanley as my 2509 has performed flawlessly and dramatically cut charge times because it pushes higher amperage to the batteries longer while keeping the generator (in your case) running in the bottom 25 percent of your genny's charge capacity giving you the best fuel mileage as well, it's a win win!

paulz
Member
# Posted: 22 Sep 2019 15:51
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BUMP!

Waiting around for my Valence U27-12XP 138AH Lithium battery to show up in the mail. Meanwhile at the flea market today I picked up this battery charger for 10 bucks because it looked more hi-falootin than anything I have. Kinda hoping I can charge the Valence with it but I know lithiums are supposed to have a special charger.

The bells and whistles are shown in the photo. It works, at least in fixed mode. The Valence batteries have some BMS circuitry built in, but apparently you need some external stuff too. Still reading up on that.

Lead batteries are simple, this is all very confusing.

The manual for the charger. Xantrex, anyone have one?

http://www.xantrex.com/documents/Discontinued-Products/TC20_40(445-0050-01-01_Rev-A). pdf
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0922191233_HDR.jpg


neckless
Member
# Posted: 11 Oct 2019 02:03
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i have a ctire 200 amp charger and set on the 20 amp mode it starts out at 60 amps and it charges the 6 6 volts in about two hours has a digital display to tell u all the bs has been in use for 7 years outside under a roof

Brettny
Member
# Posted: 11 Oct 2019 08:34
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Technically speaking 1680w at 120v is 140amps at 12v not including any ac-dc loss or equipment losses. These vehicle chargers are very limited in the ammount of 12v output they can produce as most people dont need 100A+ of charging.

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