Anyone use a poorboy alternator generator?

[user 423]

My B&D charger is only 15 amps max because my Ryobi generator is only 900-700 watts. I remember reading conflicting info about how big a charger it could run (up to 25 amps?) so I went low.

Haven't used the charger that much since the 100 watt solar panel 'seems' to keep my single FLA batt charged.

There's a lot to read about proper charging but I understand that lead-acid batteries need occasional equalization and charged at a higher voltage (up to 16v) for a short time. The solar does show bulk charge at 15.5 volts but it's only 8.33 amps max.

Years ago I used a car alternator spun by a 5hp lawn mower motor to charge first a 29 series WM battery and then 2 used 6 volt golf cart batteries. I only had a clamp on ammeter and I remember it put out 45 amps. Don't remember the voltage.

 

[highdesertranger]

remember doing it like that you still have to charge for hours and hours. in fact no matter how or what you are charging with it takes hours and hours. IMO you would be better served with adding more solar. highdesertranger

 

[user 423]

remember doing it like that you still have to charge for hours and hours. 

Yes but I would still be hooked up to solar and after bulk charging for X number of hours with the alternator genny
the solar would then finish the job.

That's basically what I've done periodically when I've hooked up the charger either with shore power or with the Ryobi.

 

[highdesertranger]

so why not just get a bigger charger for you generator? the quick math in my head says you could run a charger at lest twice as powerful maybe more.

remember that a vehicle alternator will not hold the high amperage very long, and if somehow you could get it to you will burn it up pretty quick.

you won't be able to do equalization with one. i really see no advantage of trying to use an alternator unless you use your existing alternator as a supplement charge source when you are driving.

highdesertranger

 

[user 423]

^
Yeah, adding solar is probably the better way or getting a bigger charger.

Guess I'll find something else to use this little 3hp motor on.

I'm noticing on Amazon that a 25 amp Stanley charger looks identical to the 25 amp Black&Decker and has the same functions but the Stanley is $36 cheaper. It's even less than what I paid for the 15 amp B&D last year at Home Depot.

 

[DannyB1954]

Making a battery charger from an engine and alternator will take up a lot of weight and space, and it is another engine to maintain. Some alternators put out 13.8 volts. Some can go as high as 14.6 volts.
I would recommend putting in a solenoid so that as you drive the alternator in your vehicle will help recharge. This has another advantage in that if you have a large load like say an electric coffee maker, you can start the vehicle while using a large inverter and it will help not drain your battery bank. You can also let the vehicle run for a few minutes after the load is gone. The sooner the battery is recharged the faster it will recharge. I think this is because the chemical composition in the battery has not yet changed. If you let a battery set with a low charge for a longer period, it will take a long time to recharge.

 

[user 423]

Some alternators put out 13.8 volts. Some can go as high as 14.6 volts.
I would recommend putting in a solenoid so that as you drive the alternator in your vehicle will help recharge.

Yeah, I was thinking more of the amps than the voltage. So I guess for equalization the volts don't go high enough for that.

I did order a 25 amp charger and I'm curious to see if the 900W genny will run it OK.

Right now I'm sitting around twiddling my thumbs waiting to see how the COVID thing is going to turn out and I'm looking for a project or two.

I've been putting off adding a solenoid but that's on the list.

 

[LoupGarou]

If you’re going to mix battery types, use a DC to DC charger.

 

[hugemoth]

If you use an old type alternator without a built in regulator you can manually adjust charging amperage. By using a resistor to control field current you can charge at full amperage up to 16+ volts. My home setup is a 100 amp truck alternator driven by a 12 hp lawn tractor engine. Field resistor is a piece of heating element from a dryer and a alligator clip. It'll charge my battery bank at about 100 amps even at 16+ volts.

 

[user 423]

My home setup is a 100 amp truck alternator driven by a 12 hp lawn tractor engine. Field resistor is a piece of heating element from a dryer and a alligator clip. It'll charge my battery bank at about 100 amps even at 16+ volts.

So running an alt. at max doesn't necessarily cause quick destruction. How long do you typically need to charge at those figures?

Nice to have first hand info. Thanks.

 

[hugemoth]

I've run it for several hours at a time charging a 800 amp hour battery bank. The 12 hp engine is overkill but I had it from another project. It's important to turn the alternator the right direction so the fan pulls the air through rather than trying to push it. It will generate power either way.

 

[user 423]

^
Are you totally off-grid then? Is that enough for charging or do you also have solar,etc.?

 

[hugemoth]

Totally off grid for over 30 years. There is no wind here in the tall trees so it's all solar.

 

[user 423]

^
Nice. What type of batteries?

 

[hugemoth]

Trojan L16, commonly used in forklifts. Too heavy for one person to move.

 

[DannyB1954]

I did order a 25 amp charger and I'm curious to see if the 900W genny will run it OK.

It should. I have a 900 watt Ryobi propane generator as a back up. It actually only puts out 700 watts continuous, ( the 900 is peak for about 2 seconds) I run a 30 amp charger with it. Watts is volts times amps so 30 amps times 14 volts is 420 watts. There will be wasted energy in the inside of the charger, so figure maybe another 30%. 420 watts times 130% = 546 watts.
The specs on your charger should tell you what it's maximum input watts is.

 

[user 423]

^
I have the Ryobi LP 900w also. Before I bought it last year someone on the forum said it was bogged down by a 25A charger so I got a smaller one. At the time I was in a hurry to get equipped and didn't do enough research. Typical noob mistake.

My power needs have been prettty light for the past year and I've only used the genny about 6 times.

Ryobi doesn't sell this gen. any longer but it is sold under the Baja brand at Home Depot.

 

[B and C]

Be aware that as you go up in altitude that the generator won't put out as much power.

 

[user 423]

Trojan L16, commonly used in forklifts.

What kind of battery life are you getting from these?

 

[hugemoth]

About 8 years on the L16s. A bit longer than golf car batteries.