charging 48v battery with 24volt input

[DerpsyDoodler]

SO then who wants to buy a nice dewey 24v dc generator? 8 hrs of use, electric start. diesel single cylinder yanmar

how much?

 

[DerpsyDoodler]

how much?

What are the specs? i know diddly poop about dc generators.

 

[HarryN]

The most simple way to do this is:
- Buy a 24 volt, 2 kW inverter
- Feed the inverter from the alternator (probably need a small 24 volt battery pack as well.)
- Feed the 120 vac from this inverter into a 48 volt charger

In spite of the slightly less than optimistic charge efficiency, this does work and it is done on conversion vans routinely.

 

[Tecnodave]

What are the specs? i know diddly poop about dc generators.

These Yanmar diesel generators are commonly used in the marine environment and as such are far more rugged than consumer generators, They are direct drive in that the generator has a female tapered shaft which directly couples to the tapered shaft on the engine. Not always but sometimes a prosperity taper is used which makes it hard to adapt engine to other uses. I have a few great honda engines from dead generators which do have a honda specific taper that i cannot find any pulley or coupling that will fit. Unfortunately honda generators do not outlast the honda engine.

Yanmar engines are the best of the best in small diesels......

 

[kpw]

What are the specs? i know diddly poop about dc generators.

The spec sheet

 

[DerpsyDoodler]

Unfortunately not enough power for my needs.

 

[The New JC777]

Have you had the generator running?

 

[kpw]

Have you had the generator running?

yes

 

[The New JC777]

Was it under a load?

 

[kpw]

A DC generator produces DC directly

An Alternator produces AC which is then rectified to DC with diodes, Most common alternators are three phase AC at a variable frequency which is directly related to the r.p.m. of the Alternator.

An AC generator produces AC directly from the coils, the frequency of the AC is directly related to the shaft speed and the number of coils on the generator.... Common AC generators are 3600 r.p.m. or 1800 r.p.m. depending on the number of coils , 2 or 4 are most common

Honda Inverter generators are a hybird.....they are 3 phase alternator (AC) which is rectified to DC at about 80 volts which is then used to power the inverter to make the AC. So they are AC converted to DC then back to AC.

The advantage is frequency output is not directly coupled to the R.P.M. of the engine.....thus the inverter generators change speed to be more effecient which a AC generator cannot do as frequency is directly related to r.p.m.
the frequency of the alternator is directly related to the speed of the engine, the frequency of the inverter is derived from the logic in the alternator. They do not need to be the same.

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

 

[DerpsyDoodler]

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

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

 

[Tecnodave]

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

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.

 

[DerpsyDoodler]

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.

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

 

[Tecnodave]

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

 

[DerpsyDoodler]

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?

 

[John Frum]

 

[Tecnodave]

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

 

[Tecnodave]

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

 

[DerpsyDoodler]

Thanks, both of you!

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

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

 

[Mike Davison]

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.

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