Lithium iron phosphate battery compatibility

Hi All,

Our hydro sends 3 phase 205 volts ac to a transformer that outputs nominal 48 volts dc to a lithium iron phosphate, 300 ah battery. We’ve had the system for over 15 years with barely a hitch. Several years ago we transitioned from lead acid to lithium and about that time noticed that with 3 nozzles open current output was as expected, but with the 4th open it decreased. At the turbine site there are no obstructions or flooding issues and pressure is all good. The transformer components - fuses, caps, buck boost transformers and rectifiers - are all within spec, too.

Which leads to my question. Has anyone heard of or had an issue with lithium batteries in a hydro system? It doesn’t seem like it would make a difference. Just trying to eliminate another idea.

Could you clarify what you mean by "Open current output" ? If I am not mistaken, you are saying that by adding more water (opening the 4th nozzle) you are expecting more power, but the power actually decreases?

Where are you measuring current? Is there a meter on the DC side of your rectifier before it enters the battery, or are you getting a reading through a main shunt that is connected to any other circuits? I suspect your charging voltage is a little different now too, since lithium has a much narrower voltage range. If you convert to Watts, does the same effect persist?

I am pretty sure that lithium batteries have quite a bit lower internal resistance than lead-acid, and I am wondering if that could have some effect? Do you have any way to measure the RPMs of the turbine? A cheap bike computer can be tricked into approximating RPM by setting the wheel circumfrence size to 1666mm and then reading it in Km/h. I suppose without knowing what it was doing before, this might not be much help.

Anyway, I also have hydro, but my alternator has a built in rectifier. I am sending high-ish voltage to a charge controller before it goes to the batteries. I am interested in the idea of sending 3 phase AC on my next project, as I suspect it might help reduce my wire size. I would love to pick your brain at some point.

Thanks for responding, Carl. I meant
“nozzles open.” Yes, there’s an analog meter on the dc side, but I’ve verified the reading with a digital hand-held one.

The voltage regulation is pretty close to lead acid. According to the company I keep it about 54 volts in float (which it rarely comes out of) and about 57 to 58 volts for a few minutes in bulk. I manually bring the voltage to bulk when in constant float for more than a week or two.

You might be on to something with the lower resistance thought. I’m going to look into that. In any event, I can hear the turbine wind down when the 4th nozzle is opened.

Our creek is about 800 feet from the house so that higher voltage output definitely saved us from running massive cables.