24 volt to 12 volt converter

OldSmokey wrote:

BFL13 wrote:
"- battery V drop under load is halved on a % basis at 24v"

Is that true? It might be halved or doubled as such, but I would think on a Percentage Basis it would be the same. Please elaborate--my brain quit :)

assume T105RE with internal resistance of 0.001 Ohms per cell and 1200 Watt load

for 12V we have 6 cells so 0.001*6*100 A = 0.6 V
0.6/12*100% = 5 percent drop

for 24V we have 12 cells so 0.001*12*50 A = 0.6 V
0.6/24*100 = 2.5 percent drop

That's the theory, and it's what I've found in practice. With the same inverter load I get about the same V drop, whether the batteries are 12V or 24V.

It was about 1V drop both times in my test case. So 12.5V down to 11.5V on the old, or 25V down to 24V on the new.

Different inverters have different lower V limits so can't really compare, but the new Kisae claims that it will alarm at 22.4V and shut off at 21V. But haven't heard it yet.

To be honest not sure I understand how the internal resistance of batteries works in this situation ...