Lowering absorb setpoints below minimum for LiFePo batteries

Discussion about the MX60 Charge Controller

Moderators: OutBack, OutBack Moderator Team

Post Reply
DarylDJ
Forum Junior Member
Posts: 2
Joined: Sun Oct 11, 2020 6:52 am
My RE system: Corvus 6500-48 LiFePo batteries, Outback 3648 inverter on a Midnite Epanel, two MX60 controllers and 12 QCell 330 modules

Lowering absorb setpoints below minimum for LiFePo batteries

Post by DarylDJ » Sun Oct 11, 2020 6:56 am

I have just installed four Corvus AT6500-48volt batteries into my system, but their maximum voltage is 50.4 volts. I cannot set my absorb setpoint any lower than 52 volts on my GTFX3648. Does anyone know of a way to "customize" these set points so I don't burn up these great batteries? In the meantime I've left the absorb setpoint at 52 volts but 0 absorb time and set the float voltage at 50.4 volts for six hours. I have the charger in the inverter turned off. Does this sound like a reasonable compromise if I cannot lower the absorb voltage to the recommended maximum of 50.4?

raysun
Forum Emperor
Posts: 2998
Joined: Tue Jul 26, 2016 5:57 am
My RE system: Flexpower Two: (2) FXR3048A, (2) FM80, MATE3s, FlexNetDC
SimpliPhi 48-3.8 (6 @ 48v)
Outback IBR3 battery enclosure
Suniva 330 watt panels (12 - 6 strings of 2 in series)
Hyundai 355 watt panels (6 - 3 strings of 2 in series)
Honda EU7000is gas fuel generator

Re: Lowering absorb setpoints below minimum for LiFePo batteries

Post by raysun » Mon Oct 12, 2020 7:59 am

The older FX series inverter/chargers and MX charge controllers are not inherently compatible with lithium battery technology. One of the reasons is as described.

Lithium batteries in general are very sensitive to overvoltage, which may materially shorten service life, and with some lithium ion chemistries, lead to catastrophic cell failure and fire.

I'd contact the battery manufacturer immediately, and describe the situation.

IMO, do not vary from the published charging specs in any manner.

DarylDJ
Forum Junior Member
Posts: 2
Joined: Sun Oct 11, 2020 6:52 am
My RE system: Corvus 6500-48 LiFePo batteries, Outback 3648 inverter on a Midnite Epanel, two MX60 controllers and 12 QCell 330 modules

Re: Lowering absorb setpoints below minimum for LiFePo batteries

Post by DarylDJ » Sun Oct 25, 2020 1:15 pm

So far, with a little bit of tweaking (lengthening the float voltage from 6.5 hours to 8 hours) the system has been performing flawlessly. Battery voltage has not risen above 50.4 volts (max recommended voltage) and has been selling at 50 volts.
I'm now testing off grid capabilities and have been that way for three relatively cloudy days. I'm really enjoying LiFePo batteries so far. Let's see how the long run goes. Thanks for the input.

Post Reply