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Battery charging with a generator


Jakes
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Guys

 

I need some help please.

 

My (off-grid) system is getting a MicroCare 48V/5kW Bi-directional inverter.

 

I'm adding a petrol generator to charge the batteries on days with little sunshine.

 

According to MicroCare, the inverter can charge the batteries with a maximum current of 50A. Without losses this will be 2400W.

 

Now the questions:

  1. Will a 2.5kW generator be sufficient for the job? I also have a 5.5kW, if the small one does not do the job, but I think the 2.5kW one is lighter on petrol. (I haven't tested them both with a 2.5kW load, I'm guessing).
  2. Can I use 2.5mm cabtyre with a normal 3-point plug on the end and just plug it into the generator?
  3. The inverter has 2 "Live In" terminals, L-IN and N-IN. Should I also connect the earth from the generator to the earth of the inverter?

Thanks so long.

 

J

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Guys

 

I need some help please.

 

My (off-grid) system is getting a MicroCare 48V/5kW Bi-directional inverter.

 

I'm adding a petrol generator to charge the batteries on days with little sunshine.

 

According to MicroCare, the inverter can charge the batteries with a maximum current of 50A. Without losses this will be 2400W.

 

Now the questions:

  1. Will a 2.5kW generator be sufficient for the job? I also have a 5.5kW, if the small one does not do the job, but I think the 2.5kW one is lighter on petrol. (I haven't tested them both with a 2.5kW load, I'm guessing).
  2. Can I use 2.5mm cabtyre with a normal 3-point plug on the end and just plug it into the generator?
  3. The inverter has 2 "Live In" terminals, L-IN and N-IN. Should I also connect the earth from the generator to the earth of the inverter?

Thanks so long.

 

J

 

 

1. The 2.5Kw generator will be suitable.

2. 1.5mm2 x 3 cabtyre.

3. Connect the earth. 

 

2. Depending on the distance between the generator and the inverter, but if more than about 5 meters I would suggest to rather use 2.5mm2 instead of 1.5mm2 cable - thicker cable is always better when it comes to losses.
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Inverters / UPS's have problems with power that isn't clean. You may find that the inverter doesn't like the input of the smaller gensets and then don't charge at all. I'd probably recommend getting an external 50a, 48v charger and plug that into the genset and connect it to the battery. Test the inverter first to see if it is happy with the genset power.

 

Also make sure that you don't overload the inverter when running on the genset. The bi-directional inverters will switch to mains if you overload and drawing 5kw+ from your genset will likely just trip everything.

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If I understand the question correctly, the invertor load will run on the genset while charging the battries.

The MicroCare unit can not charge the battries from mains, while running on invertor mode from said battries.

 

So, this means your 5.5kva unit will have to do duty, as you would need to cater for the invertor output load and the extra current for charging the battries!!!

You should be able to limit the battery charging current on the invertor settings. You should do this anyway, so that the charging current is matched to your battery bank size.

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