24v vs 48v? On-Grid Backup use only question

[rjpear]

Hi Folks, So if I desire a Grid backup system, where usage "Should" only be limited each year, which is best, 48v vs 24v. I have read that 48v is more efficient but I thought that if I decide to add a couple solar panels as a emergency charging source 48v would require more of them to do the job... I also see a battery which specs like this: 24V 202 ah- 5.2 kWh VS 48v 103 ah - 5.3 kwh. So the Amp hours are about double for the 24v bit the kWH is about the same. And the 48v is only $200 more. What do you think. Again this is for a limited use Whole home (of course limited use during an outage) backup. (the biggest draw is my jetpump)..

Thanks for your knowledge!

 

[MisterSandals]

I also see a battery which specs like this: 24V 202 ah- 5.2 kWh VS 48v 103 ah - 5.3 kwh. So the Amp hours are about double for the 24v bit the kWH is about the same.

Yes, the kWh is the capacity.

You should do an energy audit FIRST to see how much energy you need or expect to have for your backup system.

Then, whether you choose 24V vs 48V should depend on your use which I assume will be 120V AC appliances?

Do you know how big of an inverter you will use to run your appliances? This would require knowing how much energy your appliances use and how many of them at any time you'd want to run simultaneously.
This may be a limiting factor on whether 24V or 48V makes more sense.

As an example, if you need to use a 5000W inverter, the amps will be as follow:
5000W / 24V = 208A
5000W / 48V = 104A

Wiring and fusing for 208A (rated to 250A wires and fuses) is a LOT more expensive and difficult that 104A (125A-150A).

So get your energy audit (watt hours) and your max momentary watts and THEN you will have enough info to make your decision more accurately.

 

[rjpear]

Found a Great post under the resources/planning and sizing tools/Outline for selecting System Voltage. Had a great attached paper which described the benefits of 24v vs 48 and so on.. THX..

 

[MisterSandals]

Hopefully you will come back with any new questions, requirements or ideas before you buy. Good luck!