48v vs 24v revisited

[hammick]

I thought I understood until I spoke with Magnum Energy about their 24v and 48v inverters. Without debating the pros and cons of 48v vs 24v I have a simple question.

Will a 24v system with four 6v 208ah batteries have the same capacity as a 48v system with eight 6v 208ah batteries?

In other words, assume same percent of loss through 24v and 48v inverters can I get the same load capacity with half the batteries if I go with a 24v system?

If my panels will be within 20 feet of my inverter and batteries within 10' of inverter is there any reason to choose a 48v system? I will not be using DC lights or appliances.

This stuff is confusing.

[Sunking]

No

Battery capacity in Watt Hours = Battery Voltage x Amp Hours.

24 volts x 208 AH = 4992 watt hours
48 volts x 208 AH = 9984 watt hours.

Each battery has 6 volts x 208 AH = 1248 watt hours. Think of them as a 1 gallon gas can No matter how you stack them, they are still 1 gallon gas cans and total capacity is the addition of all the cans together. Power always adds no matter if the circuit is series or parallel.

No matter how you stack them if you have 8 6-volt 208 AH batteries you have 9984 watt hours. If stacked as

12 volts @ 832 AH (2S4P) = 9984 wh
24 volts @ 416 AH (4S2P))= 9984 wh
48 volts @ 208 AH (8S) = 9984 wh

If you have the option, always opt for the higher voltage.

[sensij]

I thought I understood until I spoke with Magnum Energy about their 24v and 48v inverters. Without debating the pros and cons of 48v vs 24v I have a simple question.

Will a 24v system with four 6v 208ah batteries have the same capacity as a 48v system with eight 6v 208ah batteries?

In other words, assume same percent of loss through 24v and 48v inverters can I get the same load capacity with half the batteries if I go with a 24v system?

If my panels will be within 20 feet of my inverter and batteries within 10' of inverter is there any reason to choose a 48v system? I will not be using DC lights or appliances.

This stuff is confusing.

If you have twice as many (equivalent) batteries, you will have twice the capacity. It doesn't really matter how they are wired, if you are assuming efficiency is the same.

Higher voltage will have less transmission loss and will operate at a lower current, even over short distances. To make the decision, you might want to look at the projected current, and work out a guess at efficiency for the 24 V and 48 V systems (including equipment performance along with transmission), and compare that to the difference in price of the 24 V vs 48 V system.

If you are keeping battery capacity constant, 24 V will have more batteries in parallel, 48 V will have more in series. Series wiring is likely to help your batteries last longer.

[hammick]

Thanks guys. That was my understanding. I hope the guy I spoke with misunderstood my question.

[thastinger]

Start thinking of batteries as pounds of potential energy storage capacity.

[thastinger]

If my panels will be within 20 feet of my inverter and batteries within 10' of inverter is there any reason to choose a 48v system? I will not be using DC lights or appliances.

This stuff is confusing.

Yes, if the calculations point to a system size that could be built with a single string of batteries. I.E. if you determine you need 8 of the 6V 225Ah batteries to have enough storage capacity and your decision comes down to 2 parallel strings of 4 to make a 24V bank or one series string of 8 to make a 48V bank, you'll always be better off to chose the single string configuration.