Setting FLEXmax 100 battery levels

Discussion about the FM100, FM80, and FM60 Charge Controllers

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rickd
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Setting FLEXmax 100 battery levels

Post by rickd »

I have two FLEXmax 100 charge controllers. The lithium battery they connect to should be topped off at 48V. The Mate3s will not allow a value less than 54V. How do I set the value lower than 54V?
I am the homeowner, not the installer. He's stumped. He said he normally programs the charge controller directly, as he's always dealt with 60/80s.
fcwlp
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My RE system: GS8048A, FM80 w/3,600W PV Fixed, FM80 w/2,700W on Zomeworks tracker, Mate3, 24 Trojan 2V L16 1100AH @ C20, Grid-Tied with Kohler 14RESA LPG Generator and MEP-803 Diesel if needed.

I install and maintain grid-tied and off-grid systems in my area and consult on solar system design/operation.
Location: 80 miles NE of Phoenix at 5500'

Re: Setting FLEXmax 100 battery levels

Post by fcwlp »

rickd wrote: Fri Nov 13, 2020 6:54 am I have two FLEXmax 100 charge controllers. The lithium battery they connect to should be topped off at 48V. The Mate3s will not allow a value less than 54V. How do I set the value lower than 54V?
I am the homeowner, not the installer. He's stumped. He said he normally programs the charge controller directly, as he's always dealt with 60/80s.
You are correct, whether it is a FM80 or a FM100, the Mate3s has a lowest absorb voltage of 52V and lowest float voltage of 48V. The challenges of system integration, if you don't understand the system in detail. If your installer designed the system, he should be responsible for pulling the FM100s out and replacing with the requisite number of FM80s.
rickd
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Re: Setting FLEXmax 100 battery levels

Post by rickd »

That's his plan, to replace with two 80s and one 60.
The 100's manual states "Supports 24, 36, and 48 Vdc battery voltages." How does this reconcile with the 52V minimum?
raysun
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Re: Setting FLEXmax 100 battery levels

Post by raysun »

rickd wrote: Fri Nov 13, 2020 7:43 am That's his plan, to replace with two 80s and one 60.
The 100's manual states "Supports 24, 36, and 48 Vdc battery voltages." How does this reconcile with the 52V minimum?
The 24, 36, and 48V specifications are battery nominal voltages. Every battery is made up from one or more cells of a specific battery chemistry. Each battery chemistry will have its own particular voltage per cell. For example, lead acid = 2.0 volts per cell (vpc) nominal. A lithium ferrophosphate cell = 3.2 vpc nominal. Other chemistries, likewise have unique nominal cell voltages.

What might be termed a "48 Volt" battery can vary from 48V by a measureable amount, depending on cell type, number of cells in the battery and state of charge.

Every cell chemistry has a unique charging profile that generally calls for a controlled overvoltage in order to "push" the battery chemistry into a charged state. Typical "absorb" voltage for lead acid = 2.24 vpc (54V for a 24 cell battery.) The various lithium cells will likewise have a unique "absorb" (end) voltage that will indicate a fully charged state.

The "48 Volt" lithium battery described in the OP has an unusually low nominal end voltage. This is characteristic of certain batteries made up of lithium ion chemistry other than lithium ferrophosphate, and fewer than typical series-connected cells. Many of these "drop-in lead acid replacement" lithium batteries have difficulty being charged by standard chargers, even those that are "lithium aware", due to unusually low or high charging end voltages.

A battery with a charge end voltage of only 48V is likely going to have an operating voltage around 46V.

FWIW, I suggest replacing the 2 FM100 charge controllers with 3 FM80 charge controllers, rather than 2 FM80 and 1 FM60. The reason has to do with serviceability in the future. The most likely component to fail on the charge controllers is the cooling fan, which on the FM80 is a trivial exercise to change out. On the FM60, changing the cooling fan is a very difficult proposition due to the chassis design.
rickd
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Re: Setting FLEXmax 100 battery levels

Post by rickd »

Thanks for the quick replies everyone. Are there non-lead acid batteries that can absorb at 52V? I assume that would be easier than redoing all the strings. I didn't dig in to all the Li and LiPo options, I just specified performance, price, and size ranges; 10kwh will get us through the night easily, 8kwh is cutting it close (lights, refrigeration, ceiling fans, vampire loads).
It looks like the price difference between the 60 and 80 is about $70 dollars, so I'll pass on your suggestion. It should even be cheaper than two 100s, $899 x 2 vs $479 x 3.
raysun
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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: Setting FLEXmax 100 battery levels

Post by raysun »

Most of the folks here that use a (non-DIY) lithium battery, use SimpliPhi 3.8-48 LiFePo4. There's lots of discussion and operational knowledge on this forum.

Three FM80s makes good sense for the small additional cost.

The FM100s are certainly more expensive, but are also more capable in several aspects. If this installation needs to meet local code requirements for rapid shutdown, the FM100s are better. Also, the FM100s with built-in Arc Fault detection provide a level of protection the FM80/60s don't. The FM100s also manage higher voltage PV panel arrays, so make accommodating the newest, high power, panels less of a wiring chore and expense.

"My new system has too many solar panels, and I'm going to reduce my array size" said nobody, ever. ;)

The FM80s will accomodate 4000W of PV panels @ 48V battery and are limited to 150V PV panel string absolute maximum. The FM100 has the "muscle" to handle 6000W into 48V battery at 300V PV maximum. Future upgrades in solar panel array size are slightly easier to accomplish with FM100s.

I just upgraded my system and replaced a single FM80 with dual FM80s, mostly because I'm an "old-school" guy, I know how they work, they fit my system requirements (7kW total PV array), and charge my lithium battery just fine. If I was starting from scratch, I would have seriously considered the FM100.
rickd
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Re: Setting FLEXmax 100 battery levels

Post by rickd »

raysun wrote: Fri Nov 13, 2020 10:01 am Most of the folks here that use a (non-DIY) lithium battery, use SimpliPhi 3.8-48 LiFePo4. There's lots of discussion and operational knowledge on this forum.
I found OutBack instructions for SimpliPhi at https://www.outbackpower.com/downloads/ ... p_note.pdf so I'm relieved that's it's officially recognized. Unfortunately I'd need five to meet the system requirements :(
fcwlp
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My RE system: GS8048A, FM80 w/3,600W PV Fixed, FM80 w/2,700W on Zomeworks tracker, Mate3, 24 Trojan 2V L16 1100AH @ C20, Grid-Tied with Kohler 14RESA LPG Generator and MEP-803 Diesel if needed.

I install and maintain grid-tied and off-grid systems in my area and consult on solar system design/operation.
Location: 80 miles NE of Phoenix at 5500'

Re: Setting FLEXmax 100 battery levels

Post by fcwlp »

rickd wrote: Fri Nov 13, 2020 12:52 pm Unfortunately I'd need five to meet the system requirements :(
Four would give you 12+ kWh useable.
raysun
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Posts: 3326
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: Setting FLEXmax 100 battery levels

Post by raysun »

fcwlp wrote: Fri Nov 13, 2020 8:03 pm
rickd wrote: Fri Nov 13, 2020 12:52 pm Unfortunately I'd need five to meet the system requirements :(
Four would give you 12+ kWh useable.
Exactly.
rickd
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Re: Setting FLEXmax 100 battery levels

Post by rickd »

raysun wrote: Fri Nov 13, 2020 8:35 pm
fcwlp wrote: Fri Nov 13, 2020 8:03 pm
rickd wrote: Fri Nov 13, 2020 12:52 pmUnfortunately I'd need five to meet the system requirements :(
Four would give you 12+ kWh useable.
Exactly.
According to the linked application note's 48V chart, if I have two FM 100 and an 8 KW inverter I need five batteries. If I'm incorrect let me know, fewer batteries saves me a lot of money.
Does anyone have a good source? Best price I've found is $2,285 each.
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