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groingo
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# Posted: 16 Dec 2018 10:18pm - Edited by: groingo
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110volt Battery charger says charging 12 volt battery at 25 amps but it is only drawing 453 watts at 5.59 amps.
Have forgotten a lot over past few years, what am I missing.
How is it outputting 25 amps at such low power input?
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ICC
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# Posted: 16 Dec 2018 10:40pm - Edited by: ICC
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Quoting: groingo only drawing 453 watts at 5.59 amps.
Those are measured where? On the AC intake side? That sort of does not make sense because then the voltage is very low. 453 watts on the AC side divided by the 5.59 AC amps = 81 volts AC. That is too much voltage drop to seem to be true.
In your case the input volts are about 10X the output volts, so the amps in would be about 10X less than the amps out. Very rough round numbers.
FYI, charging 12 volts at 25 amps, the DC voltage output is likely more like 14.5 or so, maybe more. So, 14.5 volts x 25 amps = 362.5 watts into battery
If the charger is taking in a true 453 watts AC, then that could make sense as the charger loses power to heat. 453 watts in and 362 watts out is about a 20% loss which is quite likely with many chargers.
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FishHog
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# Posted: 17 Dec 2018 07:44am
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Typically they sense the condition of the battery and provide it the optimal charging amps. Rarely will they hit the full amps they can provide. If the battery isn't drained much, its just topping it up with those 5.5amps in a slow absorb phase.
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toyota_mdt_tech
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# Posted: 17 Dec 2018 08:28am - Edited by: toyota_mdt_tech
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Quoting: groingo How is it outputting 25 amps at such low power input?
Is it an "automatic" charger? Unless the battery is stone dead, it wont do the 25 amps charge rate.
Old manual type chargers are getting harder to find. Personally, I like them for charging, while the auto ones are better for maintaining. Even the older manual ones throttle back too.
Now a boost feature, some will have a 50A start, those will pull some amps.
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groingo
Member
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# Posted: 17 Dec 2018 12:48pm - Edited by: groingo
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Bottom line it is a Stanley 25 amp boost charger batteries were at 80% but in this case did not use boost, battery did start noticeably bubbling after a few minutes so turned it off, put kill a watt meter in place and it did the same thing again and above were the numbers it showed while all the time the charger output was 25 amps.
The charger power rating tag shows its max input is 1100 watts @ 6.5 amps
Such is electronics today.
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