DIY 24V Generator build ** Update **

[taltom]

This is my second generator build. Intended to run freezer, etc. during power outages. While there are always upgrades possible, I'm requesting a sanity check for safety such as wire sizes, fuses and switches. All input is welcome.

Take care,
Terry

p.s. I've updated the drawing with a few suggestions.

 

[JCSchwarb]

This is my second generator build. Intended to run freezer, etc. during power outages. While there are always upgrades possible, I'm requesting a sanity check for safety such as wire sizes, fuses and switches. All input is welcome.

Take care,
Terry

Nice drawing Terry! Looks like a fun project.

1. Recommend adding AWG size and wire type (Solar-UV rated) from panels.
2. Recommend changing MC4 Wye to Fuse block. Most codes and manufacturers require fuse between PV and MPPT charge controller.
3. Specify wire size from battery positive to inverter.
4. Not clear why there is a 50a fuse feeding a 300A. Place fuse before MPPT and delete 50a on output to battery.
5. I didn’t calculate your loads so need to ensure those are correct (max demand in watts/24V to get your max current). Seems the negative terminal doesn’t match positive to battery.

Hope this helps. -Jay

 

[John Frum]

This is my second generator build. Intended to run freezer, etc. during power outages. While there are always upgrades possible, I'm requesting a sanity check for safety such as wire sizes, fuses and switches. All input is welcome.

2000 ac watts / .85 conversion efficiency / 20 volts low cutoff = 117.647058824 service amps
117.647058824 service amps / .8 fuse headroom = 147.058823529 fault amps

Pure copper 2 awg wire with 90C insulation is rated for 190 amps in free air.
So your 300 amp fuse is way out of spec high.

 

[John Frum]

The switch and the fuse are reversed between the battery and the dc2dc converter.

 

[Horsefly]

2000 ac watts / .85 conversion efficiency / 10 volts low cutoff = 117.647058824 service amps
117.647058824 service amps / .8 fuse headroom = 147.058823529 fault amps

Got an error there, since he's using a 24V nominal battery, not 12V. Divide the amps by 2.

 

[John Frum]

Got an error there, since he's using a 24V nominal battery, not 12V. Divide the amps by 2.

Fixed thanks.

 

[taltom]

Fixed thanks.

Yeah, I thought that was too high. So, would it be best to go with 150A to cover the inverter draw, 175A to give some room or 200A to cover the 2AWG wire between the battery and inverter?

Many thanks,
Terry

 

[taltom]

The switch and the fuse are reversed between the battery and the dc2dc converter.

Switched them. Thanks

 

[John Frum]

Yeah, I thought that was too high. So, would it be best to go with 150A to cover the inverter draw, 175A to give some room or 200A to cover the 2AWG wire between the battery and inverter?

Many thanks,
Terry

My preference is to use 105c insulation and a 200 amp fuse.

 

[taltom]

My preference is to use 105c insulation and a 200 amp fuse.

That works. I'm using Windy Nation 2AWG which is 105C rated.

Thanks!

 

[taltom]

Nice drawing Terry! Looks like a fun project.

1. Recommend adding AWG size and wire type (Solar-UV rated) from panels.
2. Recommend changing MC4 Wye to Fuse block. Most codes and manufacturers require fuse between PV and MPPT charge controller.
3. Specify wire size from battery positive to inverter.
4. Not clear why there is a 50a fuse feeding a 300A. Place fuse before MPPT and delete 50a on output to battery.
5. I didn’t calculate your loads so need to ensure those are correct (max demand in watts/24V to get your max current). Seems the negative terminal doesn’t match positive to battery.

Hope this helps. -Jay

Jay,

I've seen the 50A fuse often to protect the reduced wire going to the MPPT since the maximum size to connect there is 8AWG.

Many thanks for your input!

Terry

 

[Bud Martin]

The 20A fuse feeding the 24V to 12V Buck converter will have current higher than 20A flowing at full 12V 40A load due to conversion loss.