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

[hellosailor]

dansken-
There are many anticorrosion compounds for use with aluminum and copper wiring. Some of the common automotive/marine anti-seize compounds also appear to do the job perfectly well, along with "greases" like Tefgel, which is a Teflon-loaded gel to prevent corrosion, or high-dielectric silicon grease, which is sold as "light bulb grease" "vacuum grease" and "high temperature brake grease".

I'd suggest stopping by any professional electrical supply house, that sells to contractors and licensed electricians, or to the theatrical lighting trade. They'll have at least one suitable product on hand.

[Maine Sail]

Originally Posted by deckofficer

So what all on the fence want to hear, stay away from the discharge knee, limit bulk charging to 14.6 volts or a bit less, no BMS, cell loggers (with high and low alarms and disconnect) for piece of mind and top balance cells for plug and play use.

Can't get easier than that for all of you on the fence about LiFePO4. The cheapest and most robust energy storage available today.

Lead is Dead.

You could not pay me to charge my LiFePO4 bank to anywhere near 14.6V / 3.65 VPC.... There is zero need to do so on a boat......

I am a firm believer that people who are to lazy to spend the money on the adequate charging equipment and proper protections for the bank will eventually get what they paid for, a big FAT hole in their wallet.

It was not to long ago that one member fried some cells by forgetting to turn off batt temp compensation. A simple BMS properly wired with HVC relays would have 100% prevented this mishap..

Why go anywhere near the danger zone when 13.8V - 14.0V will yield all the capacity in the cells? I am still getting over 400Ah out of a 400Ah bank after charging to 13.8V to 5A of accepted current. This is just 5 - 7 Ah's shy of pushing them to 3.8VPC or where I top balance, in the danger zone...

I find it an odd justification when folks spend 2k on cells but can't spend another $300.00 +/- on a good regulator & charge controller?

I also do not believe in alarms for LVC or HVC. Audible alarms can be very hard to hear on some boats, especially power. Who is there to hear the alarm when the solar or wind controller goes tits up when you are off hiking....?

I still prefer an automated LVC and HVC... I also believe in using a BMS as an added insurance policy EVEN IF NEVER PUSHING THE CELLS TO SHUNTING LEVELS.

They are cheap insurance and will do fully automatic low voltage cut/disconnect and high voltage cut/disconnect.....

I am not on-board with slap some cells on a dumb regulated alt with an audible alarm and call it good..... It is however a great recipe for wallet-burn..... I suggest if folks have that extra money burning that hole in their pockets to send it onto me instead.....

[dansken]

Tanks hellosailer!
Now to something completely different: There is Another thread that could benefit from input from some of you knowlageble people over here: "LIFEPO4 for starting". Which type, how small can you go, any experience, etc ?

[Maine Sail]

BTW This is what I have into my BMS/Battery protection system:


Tyco EV-200 Contactor For LVC = $79.00
House Power BMS Board = $75.00 (Clean Power Auto LLC.)
Cell Modules = $54.00 (Clean Power Auto LLC.)
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
Job Box = $13.00
TOTAL = $287.90

That is small potatoes compared to toasting $2000.00 worth of cells due to a mishap..

This was shot during the load and charge bus re-wire and install for LiFePO4...


I already owned a Balmar MC-614 and a fully adjustable solar controller.

[deckofficer]

Maine Sail, looks like I'll be getting another lesson from you on Life(PO4). Please excuse my 40 years of lead acid mentality. When I set folks up for off grid with LA I would show them how to do an equalizing charge about 4 times per year. After this charge would be a good time to inspect and top off water level. I thought we were doing this to help keep all the cells close to each other as far as voltage.

If I understand what you are telling me is that LiFePO4 cells will both stay tight on voltages at the knee and not lose capacity if they are only charged and discharged well before both knees? The charger I bought for these cells was labeled as a LiFePO4 charger for a 12 volt bank and it is set at 14.8 volts or 3.7 VPC. Was I snowed on the charger I bought? It does charge fast, running at max 50 amp output for 110 minutes then tapers to 0 amps for the next 18 minutes on a battery that I pulled 100 a-hr out of.

[Maine Sail]

Originally Posted by deckofficer

Maine Sail, looks like I'll be getting another lesson from you on Life(PO4). Please excuse my 40 years of lead acid mentality. When I set folks up for off grid with LA I would show them how to do an equalizing charge about 4 times per year. After this charge would be a good time to inspect and top off water level. I thought we were doing this to help keep all the cells close to each other as far as voltage.

If I understand what you are telling me is that LiFePO4 cells will both stay tight on voltages at the knee and not lose capacity if they are only charged and discharged well before both knees? The charger I bought for these cells was labeled as a LiFePO4 charger for a 12 volt bank and it is set at 14.8 volts or 3.7 VPC. Was I snowed on the charger I bought? It does charge fast, running at max 50 amp output for 110 minutes then tapers to 0 amps for the next 18 minutes on a battery that I pulled 100 a-hr out of.

I have not found an ounce of reason to push my cells to shunting levels. They are still in perfect balance out to the thousandths of a volt after 200+ cycles (204 I think now).

Again, this is for fractional "C" discharging and sub .5C charging in house bank use. That point is important and needs to be kept in perspective.

Those chargers are intended for the fastest possible re-charge. If you are regularly pushing to 3.7VPC you would be very smart to top balance. Heck Balquon told me in no uncertain terms to NEVER go above 3.8V and to top balance at 3.8V MAX... In my testing I fully agree with that assessment. It was also confirmed by the CEO of Balquon that charging beyond 14V +/- results in no more capacity just a little longer taper. I can live with that.

On a boat house bank there is no need to push the voltage that high. My cells have not drifted one iota in 200 cycles to approx 80% DOD and recharges at 120A - 130A via alt and solar controller.....

If they do drift off I think a yearly or bi-yearly parallel top balance back to 3.8VPC is all that will be necessary. This is very simple, see below.

I find matching "voltages" cell by cell tedious, time consuming and NOT as accurate. I found it is MUCH easier to simply connect them in parallel and let them sit for a day or two then simply charge the parallel pack to 3.8V and stop.. It is best to start with a nearly full bank as four 400Ah cells is 1600Ah at 3.8V and it can take a while with a small power supply to get to 3.8V...

Top Balance Made Simple:

Wire in parallel let sit for a day or two or until current stops moving between cells. If you don't have the equipment to test this just give it more time. As voltages converge between the cells the movement of current gets very, very slow....


Now charge the parallel pack to 3.8V = DONE:


A bench top power supply with independent control of both current and voltage is really a critical tool if you want to be in the LiFePO4 game:



I am purposely not going to top balance yearly as I want to see how long it takes for them to get out of balance. I suspect, as I have for a while, that pushing up into the knees and higher voltage ranges is what causes them to go out of balance to begin with, hence the need for shunting at those levels.

I suspect a lot of this high voltage charging mentality comes from the EV drag, street and racing guys who want their packs ready to go again in 40 minutes.

On a boat if you stay below 14.1V to 14.2V and above 2.9V I suspect you will not have to top balance for a good many years. In one year I have already replicated what most coastal cruisers do, in cycles, in 6+ years.....

Even though I am not using my BMS for shunt balancing I AM using it as a good insurance policy with alarms, high voltage cut and low voltage disconnect. I also have a Cell Log 8 but am not as enamored with it as some are. Shunt balancing is but one aspect of a BMS and on a house bank kept well between the knees the need for shunt balancing may never even be necessary.

For house bank use I am not yet a believer that any "shunting" by a BMS is necessary but I am a firm believer that bank protections from HVE's and LVE's are necessary. It has not been necessary for my bank at all. As a matter of fact I pushed it to shunting only a few times while doing some testing last winter. That is it... I just wanted to see if it worked and how hot the resistors got...

[Lagoon4us]

I find matching "voltages" cell by cell tedious, time consuming and NOT as accurate. I found it is MUCH easier to simply connect them in parallel and let them sit for a day or two then simply charge the parallel pack to 3.8V and stop.. It is best to start with a nearly full bank as four 400Ah cells is 1600Ah at 3.8V and it can take a while with a small pwoer supply to get to 3.8V...

Totally agree with MAINE on balance, it's like chasing cats, our supplier in China gave us the same advise. Our cells after a hard solid season show on our voltage monitor balance within a few thousandths of a volt and this soon aligns when a load comes on the circuit.

Bottom and Top rebalancing is only to be performed IF there's been an 'imbalance' event i.e. dodgy connection etc..

[Jd1]

Originally Posted by Maine Sail

BTW This is what I have into my BMS/Battery protection system:

I already owned a Balmar MC-614 and a fully adjustable solar controller.

Nice job !!!!!
May I ask what the parameters are for the Balmar 614 ?

[Maine Sail]

Originally Posted by Jd1

Nice job !!!!!
May I ask what the parameters are for the Balmar 614 ?

Off the top of my head these are the big ones (I have them written down somewhere):

Gel Program
Belt Manager = 4 (this current limits the 160A alt to 120-130A)

Then into advanced settings:

dLc/Start Delay = 45 Seconds
AHL/ High Voltage Regulator Limit = 14.4V
CL/Temp Compensation Limit = 14.3V
bv/Bulk Voltage = 14.0V
b1c/Bulk Time = 24 Minutes
Av/Absorption Voltage = 13.8V
A1c/Absorption Time = 12 Minutes
Fv/Float Voltage = 13.2V (this essentially turns the reg off)
F1C/Float Time = 12 Hours
AL1/Alt Temp Compensation = 220F
BL1/Batt Temp Threshold = NO BATTERY TEMP COMPENSATION

I also have a dash mounted switch for killing the alt reg when the bank reaches 13.8V / 5A current. We discharge to 80% DOD then recharge...

Please note that an HVC relay for the regulator should cut the B+ / Red wire to the reg NOT the field wire. My dash switch also cuts regulator B+...

At any given time the regulator can be re-booted into bulk (starting the program all over) by flipping the regulator cut switch off then back on....

Disclaimer: If I find my notes some of these parameters could be different.

[T1 Terry]

Originally Posted by deckofficer

Maine Sail, your experience with these cells is showing. You must of got a quiet chuckle when you read last year that I did both a bottom and top balance. lol

I balanced bottom first then top, so in reality did a top balance for these packs.

That 3rd cell that dropped to 2.64 on the discharge knee, when bottom balanced now becomes the highest voltage cell on the charge knee. The 4th cell which was the highest voltage at the discharge knee after the bottom balance becomes the lowest voltage on the charge knee.

Before bottom balance
2.94, 2.84, 2.64, 3.06

After bottom balance on charge knee.....

At 4 amp acceptance (missed 5 amp)
3.55, 3.55, 3.90, 3.46

At charger shutoff
3.55, 3.63, 3.97, 3.46

At resting voltage
3.40, 3.42, 3.60, 3.36



As to us EV guys, we don't want to hurt our cells either and want cycle life. What we do want is a fast turn around time on the charger so charge voltages are higher, thus it is best that we, the EV guys should also top balance.

I will give this bottom balance a few cycles and if that 3rd cell stays high (over 3.90 volts), then I will again balance but at the charge knee. Maine Sail, your experience with these cells has you doing the right thing, for me I guess I had to experience first hand, but as usual you are correct.

I hope you understand what these cell voltages are telling you Bob, you are killing no.3 cell at a rapid rate.
The cell that drops to the lowest voltage discharged yet the highest voltage charged is the cell with the least capacity. Every time that cell is dragged under 2.8v or pushed over 3.6v more capacity is lost, you are creating a death spiral for that cell by pushing it so hard, stay inside the safe zones of 2.8v and 3.6v and you won't loose a lot more capacity from that cell, keep pushing it that hard and the lows will become under 2v and highs over 4v, then the death spiral speeds up. you will know you have permanently damage a cell when it's the lowest voltage when under load yet the highest voltage when charging, there isn't much you can do for it once the damage has reached that extent, just nurse it till it fails altogether.
Get a Junsi cell logger, attach at ratcheting solid state relay to the alarm port and set the high cell voltage to 3.6v and low cell to 2.8v but turn all the other alarm functions off. Charge and discharge through this relay so you automatically stop before you damage the cells further. If you buy the dearer unit it also has a data logger, set that for 30 sec sampling, then you can down load a chart of exactly how the cells are performing.

As far as a LCVD and HCVD (low cell and high cell voltage disconnect) that only function if the contacts to the relays don't seld together or the cable move to a point where the in and out touch, then only an alrm will tell you something is wrong. This what happened to my battery bank, I thought I was having issues with the control circuitry but it was just a simple case of 2 terminals on a relay touching each other. It's the simplest things that bring the most complex protection gear unstuck. The simpler the protection gear, the more attention you pay to what’s happening, automated system just make you complacent and simply forget to ever look over the system in general. it takes 10mins to retrieve a log file and view it, secs to turn the log recording on and off, that's not a lot of time out of anyone’s life to protect a serious $$ investment is it? You wouldn't buy that many $$ in shares and then just forget you have them would you?

T1 Terry

[deckofficer]

T1 Terry,

Cell #3 before last nights bottom balance was not a high cell at charge

Past full charge cell voltages
3.56, 3.51, 3.55, 3.54


It has become the high cell after the bottom balance. I'll be able to confirm in a few hours but it looks like I'll have longer run times by bottom balancing due to how sharp the discharge knees are for these cells. When one cell of the pack hits that knee ahead of the others, overall pack voltage drops off fast. With them all bottomed balanced I'll consider 2.9 volt cell voltage as fully discharged.

[FlyingCloud1937]

Have you considered PerfectSwitch to lower your blood preasusre




This makes it easy

Well, a pair makes it really easy.

Lloyd

Originally Posted by Maine Sail

BTW This is what I have into my BMS/Battery protection system:


Tyco EV-200 Contactor For LVC = $79.00
House Power BMS Board = $75.00 (Clean Power Auto LLC.)
Cell Modules = $54.00 (Clean Power Auto LLC.)
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
Job Box = $13.00
TOTAL = $287.90

That is small potatoes compared to toasting $2000.00 worth of cells due to a mishap..

This was shot during the load and charge bus re-wire and install for LiFePO4...


I already owned a Balmar MC-614 and a fully adjustable solar controller.

[Maine Sail]

Originally Posted by FlyingCloud1937

Have you considered PerfectSwitch to lower your blood preasusre




This makes it easy

Well, a pair makes it really easy.

Lloyd

I did look into those as well as many other LVD devices. My issue was it was based on pack voltage not cell level for the cut... The House Power BMS is monitoring at the cell level and protecting based on individual cell voltage not the whole pack voltage..

[FlyingCloud1937]

So,

Low is one, High is 2, 4 cells at lower/high equal 6.

I see a HVC and a LVC, and if the worry is great, at inter-cell at each level.

At pack LVC, HVC, or at cell HVC/LVC, the costs of hardware, will be cheaper then the bat costs.

As well you can program for an intermittent level at each, so if a false fault condition exists, it can be by design self correcting.

Lloyd

Originally Posted by Maine Sail

I did look into those. My issue was it was based on pack voltage not cell level for the cut... The House Power BMS is monitoring at the cell level and protecting based on individual cell voltage not the whole pack voltage..

[diugo]

I have had my 260Ah "Balqon Special" set for almost a year now, and routinely avoid both knees of the charge curve on a daily basis. My last bottom balance was ten months ago, and the voltage spread from high to low cell never exceeds 30mV and averages about half that. In order to maximize cell longevity, I only charge my bank to 80% SoC---so I cannot top balance.