[RE-wrenches] Lithium Iron Phosphate

Tue Aug 18 12:39:49 PDT 2015

Yes, it is....or soon will be.

I know who’s distributing the line here in Hawaii and am trying to find out what's going for the rest of the U.S.

marco

Thanks Marco, very impressive product. I like the idea of redundancy per module so if a cell fails, only that one module will shut down. I can build that now with multiple CPU’s with our GBS line but after looking at the EU street price, I can’t match the value. But, I don’t see it available in the US, only in EU. Do you know if it is available for US market?

Larry

On Aug 18, 2015, at 11:28 AM, Marco Mangelsdorf <marco at pvthawaii.com> wrote:

Sony is now producing an impressive LFP battery.

Attached is the spec sheet.

marco

Hello Peter,

Panasonic does not make lithium iron (LFP or LiFePO4) batteries, theirs are Lithium cobalt oxide (LiCoO2). Because RE system commonly have multiple charge sources, I think LiCoO2 is not as suitable due to the poor handling of over voltage events. Lithium iron phosphate (LFP) are far more overcharge tolerant and readily available in high capacity cells. Another problem with using LiCoO2 cells is they require 4.2V/cell to charge making it a difficult fit with common RE equipment.

Each manufacturer has recommended charge profiles. It will be difficult to follow these unless the battery is disconnected from loads while charging.

For all Lithium batteries, the discharge rate is many times greater than would ever practically be used in a RE system. Most can be discharged at 3C and surge up to 10C. A 20kWh bank could supply 60kW continuously. Don’t try that with your LA battery!

Low voltage disconnect is (or should be) built into any LFP battery system as permanent damage can happen instantly. I recently had to repair a LFMP propulsion battery system (not designed by us) that was over discharged one time. It cost $6000 for me to make the repairs and install the protective solenoids. The Battery manufacturer had warnings in their installation manual against not using proper LVD but the builder skipped that part.

Magnum Energy has a come out with a CC/CV profile that works well with LFP batteries but it’s still not the needed profile. There are many differences and factors to be addressed for the RE industry. One hurdle to overcome in RE applications is that varying loads are applied while charging. A proper LFP charger will vary the power during the charge cycle but has no way of knowing that loads are present. That creates a real challenge for equipment makers but can be resolved by designing CAN interface and software that communicates with chargers and control CPU’s to make the adjustments on the fly.  

Larry Crutcher
Starlight Solar Power Systems

On Aug 18, 2015, at 8:31 AM, Peter Parrish <peter.parrish at calsolareng.com> wrote:

I too am interested in LiFeP batteries. I think we need some more information on charge/discharge cycles. I’ve bits and pieces, but there must be some solid data from Panasonic or one of the other LiFeP manufacturers. Such as,

Recommended charge cycle
Maximum discharge rate
Low voltage disconnect

Also I expect all of the CC manufacturers are thinking about LiFeP or similar Li technology. Maybe if one of us has a friend at Outback Power, Morningstar, Midnite Solar, we could find out more.

-          Peter

Peter T. Parrish, Ph.D.
President, SolarGnosis
1107 Fair Oaks Ave.
Suite 351
South Pasadena, CA 91030
(323) 839-6108
petertor at pobox.com

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