Installing Lithium Batteries

Discussion about the OutBack battery rack solutions
Post Reply
Urs Boxler
Forum Member
Posts: 8
Joined: Fri Feb 05, 2016 6:25 pm
My RE system: Radian GS4048A

Installing Lithium Batteries

Post by Urs Boxler » Thu Aug 20, 2020 7:01 pm

I am installing a new battery bank consisting of 16 cells of LiFePo4 280 Ah batteries with a Battery Management System (BMS) to take over from my current Aquion Saltwater battery. Are there any particular settings to set for that. I have a Radian 4048A, Flexnet DC, FM80 Charge controller, Mate3 and a 4kW PV array.

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: Installing Lithium Batteries

Post by raysun » Thu Aug 20, 2020 8:41 pm

Lithium ion batteries each have specific charging requirements depending on chemistry and cell configuration. The cell manufacturer/battery vendor should have specific charging requirements that need to be followed precisely.

What type of cell/brand battery is being used?

Urs Boxler
Forum Member
Posts: 8
Joined: Fri Feb 05, 2016 6:25 pm
My RE system: Radian GS4048A

Re: Installing Lithium Batteries

Post by Urs Boxler » Thu Aug 20, 2020 10:07 pm

The battery consists of 16 cells of LiFePo4 3.2V 280Ah from EVE Energy Co Ltd from China and a matching BMS from Daly Electric. See attached battery speciification pdf.

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: Installing Lithium Batteries

Post by raysun » Thu Aug 20, 2020 10:40 pm

The .pdf didn't make it, but the site has been having upload restrictions.

The BMS hopefully sets safe limits for charging voltage and current, but the chargers should be set to not test them. 16 3.2V cells in series would be considered fully charged at 51.2V. Depending on cell characteristics, it may take a higher charging voltage to get the cells to a full state of charge.

I'm not a fan of trying to push every last ion into the anode, as it leads to dendritic growth and shorter cell life. I'm not a fan of fast charging methods either, for the same reason. If I was determining optimum charging by experiment, I'd try for a "bulk" voltage well below the maximum voltage limit (but likely above the "fully charged" voltage), and watch the current closely. Once the cells are full, the charging current should drop precipitously. Hopefully the cell manufacturer has published an End Amps figure that would represent the proper termination current.

The cells will have a maximum charge rate. Be sure the chargers are set to limit well below this figure.

The FNDC can be helpful in controlling charging current, especially in cases where the FM80 and the Radian chargers are used simultaneously. It can, of course, also track the quantity of charge and discharge current. It may, or may not, track state of charge accurately, however. SoC calculations are based on Lead Acid battery characteristics. Whether the FNDC will track SoC depends on how closely the LiFePo4 cells' discharge curve tracks lead acid. In many cases, they don't, so SoC may need to be derived by voltage, rather than current, monitoring.

Urs Boxler
Forum Member
Posts: 8
Joined: Fri Feb 05, 2016 6:25 pm
My RE system: Radian GS4048A

Re: Installing Lithium Batteries

Post by Urs Boxler » Fri Aug 21, 2020 9:12 am

Thank you for your replies. As the specification pdf did not come through I will list some of the main parameters for this LiFePo4 battery below:

Max charge and discharge current is listed in the specification at 1C (C=battery capacity of 280Ah); i.e. an amazing 280A. I will not even get close to that with my system. My max will be 80A if coming from the FM80 charge controller or 57A if coming from the 4048 inverter, based on generator input to the inverter. So I will be safe here. I may upgrade the inverter to a 8048 in the future, which would double the charge capacity to 114A, still well within battery specs.

I plan to set the absorb voltage at 56.8V on the 4048 and on the FM80. The max charge voltage for the lithium battery is 3.65V per cell or 58.4V for the whole battery bank of 16 cells.

I plan to program the BMS for a charge cut-off voltage of 58.4V and a discharge voltage of 2.5V per cell or 40V for whole battery bank.

The BMS also has an over-temperature cut-off capability, using its own temperature sensor.

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: Installing Lithium Batteries

Post by raysun » Fri Aug 21, 2020 9:54 am

It sounds like the charging specs will fit comfortably within the Radian and Flexmax parameters. The main open question is the length of time charging should be held at the "Absorb" voltage to achieve full charge. The manufacturer may have a specification for that.

As far as programming best practices for the chargers and monitor, I suggest looking at the integration guides published by Outback and Lithium battery vendors like SimpliPhi. They can provide a wealth of guidance and can be downloaded from the companys' respective web sites.

Urs Boxler
Forum Member
Posts: 8
Joined: Fri Feb 05, 2016 6:25 pm
My RE system: Radian GS4048A

Re: Installing Lithium Batteries

Post by Urs Boxler » Tue Sep 22, 2020 6:02 pm

Thank you for mentioning the integration of Outback Radian with the Simplifi lithium batteries. I have downloaded the integration guide and used it as a base for the settings, because the chemistry is the same. I have gone live with the lithum batteries on August 28 and they have performed well since then. What I really like about the lithium batteries is their (almost) flat discharge curve. It means that the lithium battery continues to absorb all the energy the solar array can supply until the battery is full, and this happens in a shorter time. With the old battery the amps going into the battery were steadily diminishing and it took longer to get the battery to be full. Thanks again.

Post Reply