charging 48v battery with 24volt input

kpw said:

If I had two 24v dc generators of the same output could i wire them in series to get 48v to charge the batteries?

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Now you're talking about useable power, but...at what point would you be better off just getting a single 120v ac generator?

DerpsyDoodler said:

Now you're talking about useable power, but...at what point would you be better off just getting a single 120v ac generator?

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Yep, just buy a inverter generator for battery charging and do get a “pfc” charger to go with it. A non “pfc” “phase <EDIT strike that word, its power factor corrected> battery charger can only use approx 50 % of generator power while a “phase <power factor corrected> ” device can use >95% of available power.

Tecnodave said:

Yep, just buy a inverter generator for battery charging and do get a “pfc” charger to go with it. A non “pfc” “phase corrected“ battery charger can only use approx 50 % of generator power while a “phase corrected” device can use >95% of available power.

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What does "pfc" stand for and what does it mean?

PFC power factor corrected......when some loads draw power the current is not in “phase” with the voltage and this will result in overloading the generator due to the current leading or lagging the voltage by some power factor. The way to correct this situation is to use a “power factor corrected load” Look into the specs of the better battery chargers and you will find the status the power factor correction.


One of the huge advantages of wound core low frequency transformers is that they can recycle this refelcted power from the load back into useful power whereas a high frequency inverter cannot recycle that power. This is exactly why low frequency inverters are better for large inductive loads such as AC motors.

If you notice some less expensive electric motors have only one capacitor where the better industrial rated motors have 2 capacitors , same reason, power factor correction, the capacitor in the circuit balances the inductance of the motor windings, the less expensive motor is capacitor start inductance run where the industrial motor is capacitor start capacitor run, resulting in better wave shape and less reflected power thus better efficiency.

If you missed a point or didnt understand part of that poke a question here

Is that the professional term for saying "it has capacitors to smooth current flow by keeping the voltage stabilized?" Or is that something completely different or only part of the equasion?

Really just part of the equation but the first description is somewhat valid as well.

thanks smooth joey....that will explain it very well

Thanks, both of you!

Tecnodave said:

Really just part of the equation but the first description is somewhat valid as well.

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Thanks for the explanation. My brain crumpled when I first read it. The video really helped me make sense of it.

Tecnodave said:

The generator is DC........IT does not generate AC.......Transformers are AC.....NOT DC The only way to change voltage on DC is a inverter or buck-boost converter....or change the generator.....very expensive.

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So how about something simple like.... 24v--> DC to AC inverter --> AC to 48v charger? Simple and cheap.

I didn't see this posted yet, though I might have missed some context where this wouldn't be desired?

Input 16 to 35v. Output 40 to 60v.

I assume there are probably higher current models but I haven't looked much beyond this page.

So, your 48V battery is made of two 24V batteries in series? What I might do:

Conceptually simplest: A 24V inverter big enough to supply an 80A 48V battery charger.

Most Rube Goldberg: 80A or better SPDT DC relays alternately connecting one or the other 24V battery to the generator, though at least 80A diodes (Schottky, if you're feeling lucky), I think, (this is off the top of my head, whether the diodes are required I can't be sure, but, it's better to have them and not need them than not have them and need them to protect your expensive stuff), switching perhaps every few minutes. Or maybe tens of minutes, so the relays don't die quickly. Probably it would be better to build a switching circuit which turns off the output power on the generator before switching the relays. You would need two 24V BMS which allow series connection.

For the Rube Goldberg, you would have to be sure the generator, or the battery, or both, are not grounded. As to diodes, I've become somewhat enamored of using 50V Schottkys for connecting things (like DC-DC converters) during testing of my 24V system, because if I don't, unexpected things happen. I may take some of them out when my design is final. If that ever happens.