2X 48V 100ah vs 2X 24v 200ah

Newton_Lass

Hello all. I need to purchase some batteries for my off grid cabin system. I was looking at the Gyll/EG4 lifepo4 batteries. The 48v 100ah ones are really hard to come by but they have the 24v 200ah in stock. I need about 10kwh for my batteries so I would need two batteries either way. 

Is there a big disadvantage to getting 2X of the 24v 200ah as opposed to 2X of the 48v 100ah? Sounds to me like it’s the same amount of power for same price since either one of them run $1,500. Not sure exactly how that works though. Thanks!

BB.

You got it correct... Same amount of energy storage, and pretty much 1/2 the bank in parallel (for 24 volt), or both banks in series for 48 volts.

Power = Voltage * Current

2x the voltage at same current (or Amp*Hours) is the same as 2x the current (or AH) at the same voltage.

Especially with lithium Ion batteries--You do get into issues with Battery Management System design. Depending on cell/battery design, you could parallel all the cells and connect in series, and use a BMS with 1/2 the number of monitoring/EQ ports (two cells in parallel = 1x monitoring port---2x cells in series = 2x monitoring ports).

Also, you can have other design issues... Many BMS systems use transistors for bank shutdown if too high/low voltage, too high current, out of temperature range, etc... You need a BMS that is designed for 24 or 48 volt banks.

Neither bank is that large AH wise... 400 AH * 0.10 rate of charge (nominal for solar) = 40 Amps... Not a large charge controller by any means (or very heavy wiring).

Go back and look at the balance of your system... Do you have the charger(s), AC inverter, loads that do what you want @ 24 VDC battery bus--If yes, then get the more available system and run with it. Don't lock yourself into a "rare" system configuration that does nothing else for you other than making it more difficult to get spares/parts/etc.

If you are (for example) using smaller AC inverters--Smaller 24 VDC inverters and inverter-chargers are usually easier to find than "small" 48 VDC inverter/inverter-chargers.

-Bill