LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

[deckofficer]

Ram,

(4) of these 700 a-hr cells will run $1848, they were $3080 3 months ago, and from other suppliers over $4000.

[NahanniV]

Originally Posted by deckofficer

Ram,

(4) of these 700 a-hr cells will run $1848, they were $3080 3 months ago, and from other suppliers over $4000.

To be fair, you must remember to let people know that the prices you are quoting are for used cells that are up to 3 years old !

[deckofficer]

Originally Posted by NahanniV

To be fair, you must remember to let people know that the prices you are quoting are for used cells that are up to 3 years old !

True, I should have mentioned they are old stock and some had been cycled about 25 times. It has been covered on this thread and Balqon states it for those "clearance" cells. So far, all who have purchased the clearance cells have been pleased with the purchase, and Balqon still has the normal 5 year warranty. For us doing EVs, and have been following the prices for the last couple of years, those prices were too good to pass up.

[downunder]

Ram,

What Lagoon4us is about to do with 400AH LiFeO4 right now would be very similar to what you need/have and might be a template for you. If you are in Greece he is not far away.

Cheers

[Pieter Dijkstra]

Hi Ram, we have just finished a 540 Ah 24V system for Catamaran using European Batteries LFP system, fully integrated with BMS and charge control for any type of charger. We added logics so battery system can be hooked up to all sorts of power supplies, also available if needed in 12V system. found EB LFP cells to be very high quality with extreme low moisture content give great calender life. Sure our system would suit your applications as well.

[JayH]

Originally Posted by Pieter Dijkstra

Hi Ram, we have just finished a 540 Ah 24V system for Catamaran using European Batteries LFP system, fully integrated with BMS and charge control for any type of charger. We added logics so battery system can be hooked up to all sorts of power supplies, also available if needed in 12V system. found EB LFP cells to be very high quality with extreme low moisture content give great calender life. Sure our system would suit your applications as well.

Contemplating a 24V catamaran install myself. Did you put 8 cells together in the center, or 4 cells on each side? Wondering if there are any electrical considerations for physically separating the bank.

[Elithion]

Originally Posted by ebaugh

I found this site a great source of information on BMS systems:

Li-Ion BMS - Lithium-Ion Battery Management Systems and large battery packs

It's done by the maker of the Elithion BMS.
But either way, his book and white papers are excellent.

Thanks!

Originally Posted by ebaugh

I found the BMS product more suited to EVs, but it could probably be adopted for marine.

The Lithiumate Lite BMS is specifically just for EVs: it won't work for marine power back-up applications, but would work for an EV boat (electric motor propulsion).

On the other side, the Lithiumate Pro BMS is versatile, for most applications, and has been used in Marine back-up applications.

Here is a selector of all off-the-shelf Li-ion BMSs, from all manufacturers.

[Pieter Dijkstra]

Originally Posted by JayH

Contemplating a 24V catamaran install myself. Did you put 8 cells together in the center, or 4 cells on each side? Wondering if there are any electrical considerations for physically separating the bank.

In our setup you basically could do either or. Each string will have own BMS in case you split them to two hulls. I would go then for 2 totally separate systems, also providing you redundance in case one system fails. With our topology reconnecting one string to the 24V bus will not give high equalizing current between both strings as well.

[JayH]

I currently tap my 24V AGM bank to get 12V and use an equalizer to keep the 12 and 24 balanced. I'm thinking the equalizer setup won't work so well with LFP since the voltage curve is so flat. I guess I'll need to add starter batteries, cross chargers, and voltage converters to the budget.

[witzgall]

Hi,

I got the housepower bms installed over the week-end, but only the balancing part, no disconnects wired in yet. My cells, when installed are oriented such that taking voltage readings is only possible on two of the four cell groups. I have a celllog 8s that I would like to use for spot checking voltages. The manual shows the first wire going to the negative terminal of the furthest cell, but then it shows each of the remaining wires going to positive terminal of one cell, and the negative of the next in series?

I would have thought it would be wired up just like the BMS, with negative on C1, then a positive on C1, C2,C4,C4. If so, could I not just tap into the wires coming from the cells to my cell boards (mine are not on the cells, but remote to them in a box with the "Main" board, different then the currently sold housepower bms)?

Chris

[NahanniV]

Originally Posted by witzgall

Hi,

I got the housepower bms installed over the week-end, but only the balancing part, no disconnects wired in yet. My cells, when installed are oriented such that taking voltage readings is only possible on two of the four cell groups. I have a celllog 8s that I would like to use for spot checking voltages. The manual shows the first wire going to the negative terminal of the furthest cell, but then it shows each of the remaining wires going to positive terminal of one cell, and the negative of the next in series?

I would have thought it would be wired up just like the BMS, with negative on C1, then a positive on C1, C2,C4,C4. If so, could I not just tap into the wires coming from the cells to my cell boards (mine are not on the cells, but remote to them in a box with the "Main" board, different then the currently sold housepower bms)?

Chris

Sharing the cell connections between the CellLog and the BMS balance boards might cause some measurement errors, most likely when the balance boards are bleeding current from a high cell. The resistance of the wires and connections will alter the voltage reading. Not necessarily a problem, but something to be aware of.

As far as where to connect the CellLog wires, either the positive or negative post will do; If the two posts are well connected by a heavy bus bar there should only be a few mV difference even under a heavy load.

So, if it makes your life easier go ahead and "tap into the wires" to the BMS cell boards, but be aware they may cause some slight errors on the CellLog.

[Maine Sail]

Blue anodized wins....





Expenses so far:

4 - 400Ah Winston Cells = $1032.00
Shipping Cells = $250.00
Tyco EV200 Contactor = $79.00
House Power BMS Board = $75.00 (Clean Power Auto LLC.)
Cell Modules = $54.00 (Clean Power Auto LLC.)
Aluminum for end plates/compression = $64.00
3/8" Polycarbonate = $27.00
Anodizing Aluminum = $60.00 (minimum charge)
Nuts, Bolts, Threaded Rod, Washers etc. = $12.80
Solar and Alt HVC relays = $8.60 (Cole Herse 70A)
Bus Bar = $4.80 (Blue Sea)
Switches, Alarm Buzzer etc. $44.00
Terminals = $9.50
Total Materials = $1720.70


Compare that to a bank like this:


4 - 100Ah Odyssey PCM2150's for a 400Ah AGM bank = $1509.60
(note I am not even including the hold downs in that price just the batteries)


"Claimed Cycles" (disclaimer: I don't believe either of these "lab" derived claims and do believe they will both be lower in real world use.)

Odyssey Cycles at 80% DOD = 400 Cycles
Winston LiFePO4 at 80% DOD = 2000 Cycles

$$ Per Cycle Odyssey = $3.77 per cycle

$$ Per Cycle LiFePO4 = $0.86 per cycle

[deckofficer]

The blue was my choice, sets off the yellow of the cells. As to cycle life, with how conservative the LiFePO4 are rated as to a-hr, my money is on at least 2000 cycles before losing 20% capacity.

I've run my cells at the 20 hour rate that LAs are rated at, and I saw 50% more than what the LiFePO4 claims for a-hr. My bet is cycle life is also on the conservative side, but time will tell.

[electric1]

Originally Posted by deckofficer

I've run my cells at the 20 hour rate that LAs are rated at, and I saw 50% more than what the LiFePO4 claims for a-hr.

Does your meter have Peukert setting or efficiency setting? I think your meter is misleading you. LFP cells do not give more than their actual capacity, regardless of C rate, they just have almost no Puekert effect, so their useful capacity is the same regardless of C rate ( within certain practical limits ).

Its common for Chinese cells to have actual capacity 2%-5% more than rated capacity, but not beyond that.

[deckofficer]

No meter other than amp meter to confirm a 5 amp load. 100 a-hr pack ran 30 hours with that 5 amp load. When I pulled 3.7 amps, managed 165 a-hr before 100% DOD. Ask other owners of these cells, when compared to LA for their capacity, they are rated very conservative. I think even at a 4 hour rate (pulling 100 amps from a 400 a-hr pack) some owners have reported 25% more than the rating. Try that will LA, a 4 hour rate for discharge, those 220 a-hr golf cart batteries might give 150 a-hr.