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Discussion Starter #1
I have a small boat which I power with 2 x 24volt, 2000 watt, Electric motors. They are connected to 2 x 12v 100ah batteries wired in series for 24v. I have 2 x 200watt solar panels to charge them (given enough days between use). I decided I needed to supplement the system by adding a DC generator to the system for when I need more run time than the batteries can provide. So I looked around and finally found a 24volt 5000watt, Inverter controlled, auto start generator. Unfortunately it was from Asia and fairly expensive with shipping and everything but against my best judgment I ordered it. When it arrived it had a small sticker on the generator saying 72volt. I tried returning it but I would have to pay all shipping costs both directions which is out of my budget so I'm stuck with it. So the first thing I did was get six batteries (72v) to try and start it. Nothing happened when I pushed the start button (no surprise). So I used the backup manual pull start and it started. Then I put a multimeter on the output and it said it was putting out 24v at idle and 60v at full throttle. Is there any way I can safely connect this to charge my 24v batteries? I admit I'm a amateur at this.

Thank You
 

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I have a small boat which I power with 2 x 24volt, 2000 watt, Electric motors. They are connected to 2 x 12v 100ah batteries wired in series for 24v. I have 2 x 200watt solar panels to charge them (given enough days between use). I decided I needed to supplement the system by adding a DC generator to the system for when I need more run time than the batteries can provide. So I looked around and finally found a 24volt 5000watt, Inverter controlled, auto start generator. Unfortunately it was from Asia and fairly expensive with shipping and everything but against my best judgment I ordered it. When it arrived it had a small sticker on the generator saying 72volt. I tried returning it but I would have to pay all shipping costs both directions which is out of my budget so I'm stuck with it. So the first thing I did was get six batteries (72v) to try and start it. Nothing happened when I pushed the start button (no surprise). So I used the backup manual pull start and it started. Then I put a multimeter on the output and it said it was putting out 24v at idle and 60v at full throttle. Is there any way I can safely connect this to charge my 24v batteries? I admit I'm a amateur at this.

Thank You
Not a problem. You really need one more item to do what you want.
It's normal for a DC generator to put out higher voltage without a load.
Also you need to have some way to control the current and voltage going into the batteries.
What you need to complete your project is an MPPT Charge Controller.
Read the manual in the second link I posted here.
This charger will accept up to 90v DC input.
These are normally used with solar panels to charge battery banks.


 

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"When it arrived it had a small sticker on the generator saying 72volt. I tried returning it but I would have to pay all shipping costs both directions which is out of my budget so I'm stuck with it. So the first thing I did was get six batteries (72v) to try and start it. Nothing happened when I pushed the start button (no surprise)."

Try a 12v battery for the starter. I think the 72v is in reference to max output voltage.
 

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Discussion Starter #4
Not a problem. You really need one more item to do what you want.
It's normal for a DC generator to put out higher voltage without a load.
Also you need to have some way to control the current and voltage going into the batteries.
What you need to complete your project is an MPPT Charge Controller.
Read the manual in the second link I posted here.
This charger will accept up to 90v DC input.
These are normally used with solar panels to charge battery banks.



Thank you

I was hoping I could run the electric motors directly off of the generator, they are 4000 watts (2000x2) but I guess that wont be possible. Also its weird the way its described (and looks) it doesn't have a separate starter. Instead the generator portion itself is the starter. This is the exact version I have (the 5KW Inverter version)



 

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Discussion Starter #5
Thank you

I was hoping I could run the electric motors directly off of the generator, they are 4000 watts (2000x2) but I guess that wont be possible. Also its weird the way its described (and looks) it doesn't have a separate starter. Instead the generator portion itself is the starter. This is the exact version I have (the 5KW Inverter version)



After shipping etc, it was $550 cad. Shipping it back and return would cost an additional $700
 

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Is that a 3 wire output I see on that generator. All my information above is null if that is the case. Did you get any documentation or wiring schematics?
So, these are actually called range extenders according to that web page.
Also, I see farther down the page it says "
Remarks: Buy the inverter range extender, please note the voltage or contact us!"
Looks like you may have the 72v model.
I don't know where to go from here.
 

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Discussion Starter #8
Is that a 3 wire output I see on that generator. All my information above is null if that is the case. Did you get any documentation or wiring schematics?
So, these are actually called range extenders according to that web page.
Also, I see farther down the page it says "
Remarks: Buy the inverter range extender, please note the voltage or contact us!"
Looks like you may have the 72v model.
I don't know where to go from here.
Thanks again

It does have 3 wires coming out but then they go into a rectifier after that its just two wires (positive and negative). I did request the 24v model on the order page itself and in a private message they assured me that was what they sent and then when I got it, It said 72v on a sticker. But when I put a multi-meter on it I get between 24v and 60v. Never reaches 72v. It is called a range extender but I was told that the difference between a range extender generator and a normal one is a range extender generator is suppose to start automatically when the battery gets low. It did not come with any documentation.
The idea I had hoped for when I ordered it was I run on batteries when they get low the generator starts and I can keep going on that. I had looked at running a regular household generator. But couldn't figure out how to change the voltage to 24v and still keep enough wattage (4000) to run the electric motors. If you have any ideas at all please.
 

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Thanks again

It does have 3 wires coming out but then they go into a rectifier after that its just two wires (positive and negative). I did request the 24v model on the order page itself and in a private message they assured me that was what they sent and then when I got it, It said 72v on a sticker. But when I put a multi-meter on it I get between 24v and 60v. Never reaches 72v. It is called a range extender but I was told that the difference between a range extender generator and a normal one is a range extender generator is suppose to start automatically when the battery gets low. It did not come with any documentation.
The idea I had hoped for when I ordered it was I run on batteries when they get low the generator starts and I can keep going on that. I had looked at running a regular household generator. But couldn't figure out how to change the voltage to 24v and still keep enough wattage (4000) to run the electric motors. If you have any ideas at all please.
Trial by error here.
Do this OUTSIDE, AT YOUR OWN RISK! Hey, hold my beer and watch this. (Stand back)
Find two cheap lawnmower 12V batteries.
Charge them up with a regular battery charger.
Wire them together as you would with your boat batteries. 24V
Connect your range extender like you would connect your solar charger. Set your multimeter up so you can monitor the battery voltage where your range extender is connected to the batteries.
Connect a load to your batteries like you would connect your boat motors. Include an on/off switch. You could use a 110V space heater for this.
Turn your multimeter on so you can read the battery voltage.
Turn your space heater (if this is what you are using) on to low.
See if the range extender starts when the voltage gets below 12V.
If the range extender does not start then start it manually. If the voltage goes above 32V to for very long, shut it down.
Shut off the space heater and recharge your batteries using a standard battery charger.

Note: It would be a good idea to also have a clamp on AMP meter on one of the range extender wires connected to your batteries to monitor the current the range extender is putting out.

That's the best I can think of.
Be careful of exploding batteries.
 

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Discussion Starter #10
Trial by error here.
Do this OUTSIDE, AT YOUR OWN RISK! Hey, hold my beer and watch this. (Stand back)
Find two cheap lawnmower 12V batteries.
Charge them up with a regular battery charger.
Wire them together as you would with your boat batteries. 24V
Connect your range extender like you would connect your solar charger. Set your multimeter up so you can monitor the battery voltage where your range extender is connected to the batteries.
Connect a load to your batteries like you would connect your boat motors. Include an on/off switch. You could use a 110V space heater for this.
Turn your multimeter on so you can read the battery voltage.
Turn your space heater (if this is what you are using) on to low.
See if the range extender starts when the voltage gets below 12V.
If the range extender does not start then start it manually. If the voltage goes above 32V to for very long, shut it down.
Shut off the space heater and recharge your batteries using a standard battery charger.

Note: It would be a good idea to also have a clamp on AMP meter on one of the range extender wires connected to your batteries to monitor the current the range extender is putting out.

That's the best I can think of.
Be careful of exploding batteries.
Trial by error here.
Do this OUTSIDE, AT YOUR OWN RISK! Hey, hold my beer and watch this. (Stand back)
Find two cheap lawnmower 12V batteries.
Charge them up with a regular battery charger.
Wire them together as you would with your boat batteries. 24V
Connect your range extender like you would connect your solar charger. Set your multimeter up so you can monitor the battery voltage where your range extender is connected to the batteries.
Connect a load to your batteries like you would connect your boat motors. Include an on/off switch. You could use a 110V space heater for this.
Turn your multimeter on so you can read the battery voltage.
Turn your space heater (if this is what you are using) on to low.
See if the range extender starts when the voltage gets below 12V.
If the range extender does not start then start it manually. If the voltage goes above 32V to for very long, shut it down.
Shut off the space heater and recharge your batteries using a standard battery charger.

Note: It would be a good idea to also have a clamp on AMP meter on one of the range extender wires connected to your batteries to monitor the current the range extender is putting out.

That's the best I can think of.
Be careful of exploding batteries.

Thanks
I will try this as soon as the weather improves a little bit. trying it in a blizzard not fun. Its been awhile since I blew anything up could be fun. One question you said I could use a space heater as a load. I'm guessing I would have to run that through a large inverter first? to get the 110v
 

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Thanks
I will try this as soon as the weather improves a little bit. trying it in a blizzard not fun. Its been awhile since I blew anything up could be fun. One question you said I could use a space heater as a load. I'm guessing I would have to run that through a large inverter first? to get the 110v
A space heater is "resistive" heat. It doesn't care what the voltage is. It just won't get very hot. It will draw current just like a light bulb. You don't need to do anything but come up with a convenient way to wire it to the batteries.
Sacrifice a cheap two prong extension cord. plug your fan into it, cut the male end off the extension cord. Strip the wires and hook them to your batteries.
 

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Discussion Starter #14
Be sure and keep us updated on your science experiment.
Quick question: (I haven't tried the experiment yet) : I know the voltage increases when the RPM increases. I'm assuming then that the watts do to? Its rated at 5000watts. I'm guessing it only achieves that at full throttle?
 

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watts is by the winding diameter of the wire size.
more voltage the less watts by theory or ohms law with more speed...
unless you are using a step down transformer.

we do rotor speed by hz on the gen sets.
set it to 60 hz if it is usa appliances.
This unit puts out DC power. No hz in DC power.
 

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Quick question: (I haven't tried the experiment yet) : I know the voltage increases when the RPM increases. I'm assuming then that the watts do to? Its rated at 5000watts. I'm guessing it only achieves that at full throttle?
Could you post photos of the controller that hooks up between the range extender and the batteries? I'm interested in the wiring on the input side, and the output side to the batteries.

I understand the voltage increasing with RPM but, you can have higher voltage without higher current. The controller may limit the current(wattage) depending on the demand of the state of charge of the batteries (like a battery charger) and the load placed on the batteries by the item(boat motors, your heater or light bulbs, etc.).
It may be possible for this controller to limit the voltage to the voltage requirements needed for the batteries.
One thing I noticed on the pages linked to the product you listed, it showed two photos.one with the unit hooked up to batteries saying "Good" , and one photo with the unit not hooked up to batteries with a warning "Damage".

One point I will make here, This unit is not designed to be connected directly to your boat motors!
Photos of the unit and controller would be nice to study.
Screenshot 2021-01-28 103931.jpg
 

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Discussion Starter #20
Not
Any luck solving your problem yet?
[/QUOTE
Not yet :-(
Could you post photos of the controller that hooks up between the range extender and the batteries? I'm interested in the wiring on the input side, and the output side to the batteries.

I understand the voltage increasing with RPM but, you can have higher voltage without higher current. The controller may limit the current(wattage) depending on the demand of the state of charge of the batteries (like a battery charger) and the load placed on the batteries by the item(boat motors, your heater or light bulbs, etc.).
It may be possible for this controller to limit the voltage to the voltage requirements needed for the batteries.
One thing I noticed on the pages linked to the product you listed, it showed two photos.one with the unit hooked up to batteries saying "Good" , and one photo with the unit not hooked up to batteries with a warning "Damage".

One point I will make here, This unit is not designed to be connected directly to your boat motors!
Photos of the unit and controller would be nice to study.
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