Need Opinions on Lithium Iron Phosphate

[Murby]

I have an opportunity to purchase some Lithium Iron Phosphate batteries. They're 12.8 volts @45 AH.

These batteries came out of a hospital and were used in mobile hospital carts for various electronics. Physically, they look like they're brand new. Seller claims they have a 2015 sticker on them.

They're made by Power-Sonic (PDF File link to manufacturers website) and even have their own built in BMS.

http://www.power-sonic.com/images/powersonic/LithiumIron/PSL-12450.pdf

Seller only wants $100 each for them and he seems to have a lot of them. He even has various other brands of the same type of battery. Some from A123 systems, Valence, etc. All are basically lithium based and he says all come out of mobile hospital carts of one type or another.

New price is over $700 on these.

I would tend to think that a hospital would be likely to treat them softly and replace them way early. (imagine the lawsuit when doctor yells "Charge to 200 and CLEAR!" and the nurse says "Sorry Doctor, the best I can give you is 120) I don't think that would go over well.

I have little knowledge of how these are actually used. Are hospital carts charged every night? Do they run these things dead before recharging? Anyone here work in a hospital that would know?

What's your opinion on these?

Thanks,

[Sunking]

Well Wife and Daughter are both doctors and I know how they operate crash carts, they keep them plugged into AC power until they need them which is not great with LFP batteries. For one I would never advise anyone to buy used batteries except for salvage where you buy them cheap and sell them as scrap metal for a profit. It is a common tactic Telecom uses to turn a liability into an asset selling junk.

If your intent is to use them on an Inverter or charge them from solar is not going to work out very well. To start you cannot parallel them like you can Lead Acid batteries to increase capacity. With Lithium the only way to parallel them is at the cell level (3.2 volts) not a block level of 12.8 volts.

Second issue is they have a built-in BMS that is NOT compatible with Solar. The BMS is made to disconnect when fully charge, and if and when that happens can damage a solar charge controller, or cause the controller to go stupid.

Third issue I see is the product you linked to the specs state max Charge and Discharge rate is significantly less than 1C. Max recommended charge/discharge is 9 amps and on a 45 AH battery is only C/5. Well that is just dandy if your Solar Panel and Inverter is 100 watts or less. Absolutely perfect for Blinking LED road side Warning Sign; "Intersection Ahead".

My opinion. Pass.

[Murby]

Wow Sunking,
I asked, you delivered!

Thank you so much for taking the time to type that all out. Looks like I'm going to take a big pass on these.

[PNjunction]

Pass - but not because of PowerSonic, but buying used batteries are like using somebody else's toothbrush.

Powersonic goes into more detail than many with their own battery specs and documentation. And understand, that to offer any sort of warranty at all, you have to put a bms on them to protect them from the average abusive consumer.

Read the tech specs and application notes. Read the warranty. Looks like diy'ers are on their own If I'm not misunderstanding.

Thing is, if you know what you are doing (even with the KISS method I propose for those who will take the time to do it right), this comparable unit, minus all the warranty hardware can save you quite a lot:

http://www.batteryspace.com/lifepo4-...-2vx4-dgr.aspx

Charge each cell individually upon receipt, add an LVD, spice it up with a coulomb-counter if you like and Bob's your uncle. As long as you are safe and sane about it.

Sunking will surely recognize them. These are NOT the high-performance LFP that you would use in a drag vehicle, wheelchair, etc. For THAT type of application, you need Headway Lifepo4 *cylindricals* or other high-rate LFP.

Powersonic's specs indicates that theirs are most likely very similar prismatics inside. GREAT for low-current draw, or sluggish short-term utility vehicles. And for properly designed solar systems that have enough capacity that they aren't beating the cells to death.