Nickle Iron batteries,voltage drop.

Sam I am

Battery voltage drops with any load applied.

We installed an A/C coupled system with the Magnum MS4448PAE inverter and a 48 v 250 Ah NiFe battery bank. In February, an ice storm hit our area and we lost power for three days. When we switched to battery power the voltage dropped from 52.7 to 36 (drop out setting) in about 12 minutes. The state of charge on the inverter display remained at 98% while this voltage drop took place. Finally last week the company that installed the system came out to diagnose the problem. According to "Be Utility Free" the company that supplied the batteries said the charger must generate 68.2 v to completely charge the batteries and Magnum says the inverter will only go as high as 64v. Also it is my understanding that NiFe batteries can go down to near zero without damaging the batteries. Magnum also says that 36v is as low as the inverter will go as far as the "drop out" voltage is concerned.
Needless to say we spent a lot of money on this system and ask the question several time as to the compatibility of the inverter and NiFe batteries. Are these two compatible?
​We know very little about solar systems so keep that in mind with any responses.

BB.

Do you have other charging sources (AC Battery charger, solar charge contorller+array, etc.)?

I don't know much about NiFe batteries. They are not damaged by being under charged... You are probably losing a bit of stored energy (battery not full) and/or it may take longer to fully recharge (higher charging voltage, higher current, faster charging).

Hopefully, one of the other members here with NiFe batteries can add their information.

You might want to contact Iota Engineering and see if their 48 volt battery chargers can be adjusted to 68 volts (for a reasonable price).

http://www.iotaengineering.com/

That is the problem when going with cutting edge (or in this case re-introduction of classic tech)--Finding off the shelf equipment that supports your needs.

Does the battery Vendor have any suggested charging systems that work with their batteries?

-Bill

Sam I am

Yes. We have the Enphase micro inverters on each of the 14 panels (3.5 KW system). That is another problem I feel we have. I would think that if the batteries were not delivering the system would switch over to the PV to deliver power.
The battery vendor suggested breaking the batteries down into smaller banks and charging them 8 to 10 at a time to reach an initial full charge. The problem there is finding an A/C battery charger that will not trip out when it reaches it's overcharge limit. With all that said, for what we paid for the system I would not expect to have to do this. Again I am questioning the compatibility of the inverter with these batteries.