diy solar

diy solar

How to charge battery bank with gas generators but no inverter/charger

P

PNWDave

New Member
Joined
May 28, 2020
Messages
13
Hi all. Piecing together a smallish (1.2kw) system as a starting point for a much larger system based on suggestions from another post on this forum. I need to be able to top off the batteries with generators when the sun just isn't cutting it. I wanted to know if I must get an inverter/charger or if I can get a less expensive inverter and somehow supplement the batteries through other means (still using the gas-powered generators). If I can use my generator which has a 12v DC out on it, how would I charge a 24v battery bank?

Thanks in advance for the advice.
 
Last edited:
The generator produces 110v ac. If you have a plug-in battery charger that would normally be used for a car, that could be plugged into the 110v ac.

However, that type of charger isn't going to charge the battery with enough amps. The converter in my trailer can charge at 45 amps. To bring your battery bank up to 100% SOC it might take a few hours.

Best bet is to buy a converter that is designed for your battery's chemistry type.
 
I can't speak for the pros in the group as I'm a newbie to Solar systems. But 2 to 3 times a month during the summer months our utility power goes out. This past winter I bought a gas generation from Costco that puts out 120 vac at 15 amp rating. If I want to charge a battery assuming my utility power is still off, All I need to do is connect my battery charger to the generator output port and connect the charger directly to the battery to be charged.

See if you can do the same thing. Give it a try, if it doesn't work, nothing lost and move on to plan B.
 
You have 2 options. Do as @Jim Burrow said and connect a battery charger to your gen and use that to charge the batteries, this however is inefficient and you're going from DC -> AC -> DC and there's losses every time you switch over. What you really need is a DC generator, alternator or turbine (water or wind). You'll also need to have a way to detect when the battery is nearing full and ramping down the charge or just cutting it off before you reach the balance/abortion stage.
 
L-P-G said:
He'll still need something to generate the power, either solar or something turning a rotor inside a stator.
Click to expand...

In the title of the thread he mentioned that he has a generator. The assumption there is that the generator is producing 110v ac.

I don't know if the mention of a 12v dc output on the generator was in the original post or part of an edit, but I missed that. There are DC-DC chargers that can step up the voltage from 12v to 24v. Will that be less expensive than a typical 110v converter? Plus, can the 12v output port produce enough amps?
 
My old generator is rated at 5,000 watts AC with both a 240 volt split phase and a pair of 120 volt outlets. The more expensive version at the time also had a 12 volt outlet, but it was rated at just 7 amps max (about 84 watts). It just didn't seem worth it. I have a 600 watt charger for my 48 volt (58.8 volt full charge) battery bank. That is far more power, but still nothing compared to what the generator can handle. For a 24 volt system, look at something like this.


I have thought about using up to 3 of the 600 watt chargers to keep the generator isolated from the inverter AC buss. I know it would be more effective to just connect the generator to the AC input of an inverter charger, but the fact my generator is an old direct AC alternator, and the frequency floats around from 55 to 63 Hz as the load varies. And I absolutely don't want any chance of the inverter or solar array back feeding into it. If I am without power for a long time and solar production is weak, I would move my refrigerator and furnace over to the AC outlets on the generator, and use my 600 watt charger to bring the battery bank back up. Once the battery bank is near full, I can shut the noisey generator down and run off the batteries again.

Honestly though, we so rarely have a power failure here, I have no need to make this an auto switchover. For a true off grid system, I would want an auto start system and transfer switch to keep power flowing.
 
PNWDave said:
If I can use my generator which has a 12v DC out on it, how would I charge a 24v battery bank?
Click to expand...
if the typical Honda, Yamaha, Champion, firman, Westinghouse, and etc small generator - forget about the 12v output on the generator. It is not efficient to charge batteries by this output. Use the 120v output to drive a charger.
 
My genny has a 30amp hookup that I plan to do this with. I am going to use one of the PIP systems where I can just plug in if needed. Not the most efficient but keeps the system portable if I need to book across the country to family.
 
Jim Burrow said:
I can't speak for the pros in the group as I'm a newbie to Solar systems. But 2 to 3 times a month during the summer months our utility power goes out. This past winter I bought a gas generation from Costco that puts out 120 vac at 15 amp rating. If I want to charge a battery assuming my utility power is still off, All I need to do is connect my battery charger to the generator output port and connect the charger directly to the battery to be charged.

See if you can do the same thing. Give it a try, if it doesn't work, nothing lost and move on to plan B.
Click to expand...
I was thinking along these lines also. I have 3.8kwh 48V Li-ion powerwall. I do not have a lot of average sun exposure. I was wondering if I could charge the 48V battery with a dc power supply set at solar panel settings through a 48v controller connected to the solar inputs?
 
toolmaker said:
I was thinking along these lines also. I have 3.8kwh 48V Li-ion powerwall. I do not have a lot of average sun exposure. I was wondering if I could charge the 48V battery with a dc power supply set at solar panel settings through a 48v controller connected to the solar inputs?
Click to expand...
typically you just run the DC powersupply directly to the solar input (bypassing the controller) You'll see Will do this in a lot of his videos to simulate a solar array hooked up.
 
PNWDave said:
Hi all. Piecing together a smallish (1.2kw) system as a starting point for a much larger system based on suggestions from another post on this forum. I need to be able to top off the batteries with generators when the sun just isn't cutting it. I wanted to know if I must get an inverter/charger or if I can get a less expensive inverter and somehow supplement the batteries through other means (still using the gas-powered generators). If I can use my generator which has a 12v DC out on it, how would I charge a 24v battery
Click to expand...

I dont know of any solar system that doesnt use a solar charge controler. This is the "charger". So no you dont have to have an all-in-one inverter, but if your going to have solar panels, your going to have a SCC which will do the charging (from the sun). Your question about charging from the generator when the sun isnt out is valid, In addtion to the car chargers mention above, you can step up to a larger 20 or 40 amp golf cart charger. (NOTE: these kinds of chargers are only intended for lead-acid batteries, if you intend to have something else you can not use "car charger" styles on other chemistry batteries.)
 
Thanks schmism,
I'll have to check Will's videos. Actually, I think that's what I meant to say.
 
GXMnow said:
My old generator is rated at 5,000 watts AC with both a 240 volt split phase and a pair of 120 volt outlets. The more expensive version at the time also had a 12 volt outlet, but it was rated at just 7 amps max (about 84 watts). It just didn't seem worth it. I have a 600 watt charger for my 48 volt (58.8 volt full charge) battery bank. That is far more power, but still nothing compared to what the generator can handle. For a 24 volt system, look at something like this.


I have thought about using up to 3 of the 600 watt chargers to keep the generator isolated from the inverter AC buss. I know it would be more effective to just connect the generator to the AC input of an inverter charger, but the fact my generator is an old direct AC alternator, and the frequency floats around from 55 to 63 Hz as the load varies. And I absolutely don't want any chance of the inverter or solar array back feeding into it. If I am without power for a long time and solar production is weak, I would move my refrigerator and furnace over to the AC outlets on the generator, and use my 600 watt charger to bring the battery bank back up. Once the battery bank is near full, I can shut the noisey generator down and run off the batteries again.

Honestly though, we so rarely have a power failure here, I have no need to make this an auto switchover. For a true off grid system, I would want an auto start system and transfer switch to keep power flowing.
Click to expand...
Does this mean I should not use the 12v dc plug in the gas generator to charge a Jackery? I have the Costco yamaha knock off 2200w generator, and I've heard that their 12v outlet is not regulated.
 
toolmaker said:
Does this mean I should not use the 12v dc plug in the gas generator to charge a Jackery? I have the Costco yamaha knock off 2200w generator, and I've heard that their 12v outlet is not regulated.
Click to expand...
my 1700w honda clone also has 12v outlet, but as others have indicated only puts out like 5 or 7 amps. I assume the best option is to take the 12v dc and run that into the jackery solar side, and then use the AC charger plugged into the 120v on the genny and "double" your charge rate so you dont have to run the generator for 5 hrs to charge the thing back up.
 
schmism said:
my 1700w honda clone also has 12v outlet, but as others have indicated only puts out like 5 or 7 amps. I assume the best option is to take the 12v dc and run that into the jackery solar side, and then use the AC charger plugged into the 120v on the genny and "double" your charge rate so you dont have to run the generator for 5 hrs to charge the thing back up.
Click to expand...
Read your generator owners manual to see if utilizing both output sources are ok. Many times it is not ok.
Current model Honda EU2200i only puts out 8.3 amps of unregulated 12v power.
 
mapguy525 said:
Read your generator owners manual to see if utilizing both output sources are ok. Many times it is not ok.
Click to expand...
My version is a blackmax bmi2100 and outputs 7.5 amps
Per the manual
The 12 V DC receptacle provides continuous charge. Do
not overcharge battery or leave battery unattended. Doing
so may cause damage to the battery.
Click to expand...

and
NOTE: The AC receptacles can be used while the DC
receptacle is in use.
Click to expand...

So yes, check your manual seems some allow it, were others don't.
 
You must log in or register to reply here.

Similar threads

A
Charging lifepo4 battery bank.
Replies
4
Views
360
Andrewko
A
K
Batteries are being overcharged by All-in-one Inverter
2 3 4
Replies
69
Views
3K
42OhmsPA
4
S
pure sinewave inverter and gas generators
Replies
2
Views
193
seneysolar
seneysolar
G
Charging lead acid from lithium no alternator
Replies
10
Views
573
Vigo
V
D
OK, DC generator versus AC generator, what's everyone's opinoin
Replies
9
Views
344
OffGridForGood
OffGridForGood
Back
Top