Why Do 18V Batteries Charge Faster but Discharge Quicker Using DC to AC Inverter?

Hi,

I have noticed that when I charge my 18 volt batteries using the ac charger plugged into a dc to ac converter in my truck the batteries charge faster and die faster.

It doesn't seem to make sense since the voltage is supposedly converted to ac and I would expect the batteries to charge the same way as on the grid. But I have timed the process and the batteries charge in almost half the time in the truck and last a little more than half the time.

Any input would be appreciated.

It is not that bad since DC to AC inverter is just giving up more power or potential but the current stays the same. The batteries charge faster with supplies that have high current rating provided that the voltage is relevant to the system. High voltage could produce explosion that can physically damage your device. High current implosion will drive the device faster and heats up faster.

More likely is that the batteries are not fully charging from the dc source. I have seen this with a cell phone charging from the ac adapter in the wall compared to charging from auto dc. I haven't gotten a meter out to test to be sure but the phone indicates it is fully charged. I presume the fault lies in the way the sensing circuitry detects the battery level. I am guessing that the ac adapter actually delivers a rectified dc that pulsates somewhat so that the sensing circuit reads it at a lower value than a true dc. That would allow the battery to charge to a higher level on the ac charger. I'm sure this would all be within engineering specs but noticeable in operation. It would be consistent with what you are seeing in that the shorter charging time results in shorter useful charge.

Maybe I should clarify further. I wired a dc to ac converter, modified sine wave, in the cab of my truck. Then I plugged the Ridged 18 volt battery charger, made for 110 ac, into the converter.

In the house, the batteries charge about twice as long on that charger, in the truck on the converter, they charge in almost half the time and last about half as long.

I understood exactly what you said the first time! Although you did add the information that it is a modified wave inverter which surely results in a different charge. Refer to my original comment. The sensing circuit is reading the power from the sources differently. Try checking battery voltage at the end of the charge cycle from both sources. Let the batteries settle 10-15 mins after the charge cycle before measuring.

To be honest, I don't know whether DC to AC inverter bad for battery charger or not. Before reading this point, I'm used to charge camera battery with 400w DC 12v to AC 110v power inverter when start a road trip. But I show never pay much attention to this question. Whether it is bad for battery. I have used this charger to charge battery for two years. There is no problem about my camera battery. If you want to know more about this charger, you can search bestekmall on Google to learn. Hope this tip is useful to you. Warm regards.