Crude 2.5C Capacity Test Of Frey 36130190-60PF 60Ah Cell

Thanks for the pic. I assume this is a Frey cell? How would you describe this construction(jelly roll, accordion, etc)?

I thought the jelly roll construction was one continuous sheet of lithium doped copper (with a separator in between). This video seems to show individual sheets ( see 3 seconds in) .

There is another. longer promo video by Frey where they actually show the cutting and stacking process of the foils - but I can't seem to find it any more. May be on one of their social media acounts...

I would love to understand if any of the construction techniques impacts the internal resistance of the cells. I somehow doubt it.

Their stated IR specs (up to 1mohm for a 100ah cell) is way higher then comparable 100ah CALB, EVE, etc. Also, my individual cells range in IR from 0.4 to 0.9 - that's big deviation. However, notwithstanding the IR range, they are staying perfectly balanced ( and my BMS has only has a 200mv passive balance current).

BTW - My cell grouping strategy was to put the worst cells (highest IR and largest volt drop) together (in packs of 4) and the best cells in groups of 4. I put the best cells in position 1 and 4 ( ie main negative and positive) on the assumption ( this could be a mistaken assumption) that main neg / pos will see the largest loads.

Anyway, i ordered a cheep 3000w inverter recently and will do some highish C testing with the pack before I commit to put it in the boat ( which entails a lot of custom install work, so do want to make a change for the worse...)

bestconcreteblock said:

Are you sure you are isolating voltage drop across your wiring and measuring directly on cell terminal? Either way, 100-150mV slump for a .4C test on the Frey 100Ah cell doesn't seem bad to me. According to the EVE 280 charts posted by RCinFLA, a similar .4C test would slump around 70-80mV.

In my case, I have moved forward with my build as I am satisfied with my tests. In the end, I paid for a 60Ah cell, and I believe that is what I got. If you look at my second test above, you can see I was able to pull about 62Ah at this high discharge. Am I going to loose some energy to heat? Yes. Will the cells survive these high C-rates as long as I remove the heat? I think so. Would an EVE storage cell survive these high C-rates? I doubt it.

From what I have seen, this is a complex topic with not-so-simple answers. I will leave it to the those who have more experience. When RCinFLA said "0.260v drop due to R_ionic is not too bad for 3C discharge rate", that was enough for me to move forward.

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Any update on your project? How are the cells behaving under high C loads.? Mine continue to be in perfect balance....

Marinepower said:

Any update on your project? How are the cells behaving under high C loads.? Mine continue to be in perfect balance....

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Slow progress. BMS leads and heating/cooling hardware pretty much all mounted. Power resistors bring up the pack temp quick with about 600W of heat.




Single point (set screw) compression with Belleville spring under round thrust pad to indicate compression:



BMS mounted. AMXL Fuse/holder is in place. AMXL has 8kA breaking capacity at 63VDC. I think it is a good compromise for the tight space.






Air duct with flow direction baffles:






Fan connected to duct:


Duct in place:



Not a lot of room to work!:



Without fan:



I haven't load tested the whole pack yet. I am going to use three of these 48V 2000W water heater elements in parallel to load the pack to about 120 amps:
https://windandsolar.com/9-3-8-inch-dual-power-submersible-water-heating-element/

JK BMS:

Wow, i don think i have ever seen such attention to detail on both fixturing and heat / cooling for cells. You have some crazy metal working skills. That is a thing of beauty. Thank you for posting.

I am looking forward to your load test results. Please do post a summary here.

What kind of C rates are you anticipating for your build? I assume this is for a motor - so some big inductive loads. I'm surprised you are not using a mechanical rely type BMS....

MP

Marinepower said:

I am looking forward to your load test results. Please do post a summary here.

What kind of C rates are you anticipating for your build? I assume this is for a motor - so some big inductive loads. I'm surprised you are not using a mechanical rely type BMS....

MP

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Thank you. It has been long journey.

I will definitely post my load tests here.

I expect C rates up to 3C. This will be powering a walk behind tractor using a 3 phase induction motor through a Curtis controller. HPEVs AC-9:
https://www.hpevs.com/ac--electric-motor-for-motorcycles-ac-9-03-27.htm

I also have concerns about the mosfet based BMS. I do have an easy out should I have issues. The Curtis controller uses a contactor before the drive. I can change things around fairly easily and power only this contactor through the BMS. The only thing I don't like about this option is the inability to use the BMS to estimate SOC.

bestconcreteblock said:

Thank you. It has been long journey.

I will definitely post my load tests here.

I expect C rates up to 3C. This will be powering a walk behind tractor using a 3 phase induction motor through a Curtis controller. HPEVs AC-9:
https://www.hpevs.com/ac--electric-motor-for-motorcycles-ac-9-03-27.htm

I also have concerns about the mosfet based BMS. I do have an easy out should I have issues. The Curtis controller uses a contactor before the drive. I can change things around fairly easily and power only this contactor through the BMS. The only thing I don't like about this option is the inability to use the BMS to estimate SOC.

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Well you are working with higher voltages than me ( i'm 12 volts) so a FET based system may work for you.

There are BMS designed for mechanical relays. I think they typically have seperate charge and discharge busses.

One is the REC BMS which is reputably very good but pricey. I would have gone REC but was put off by the lack of a display.

Looking forward to your high C rate tests.

I got the load bank tub all put together:




Aluminum bus bars to make things easier to connect:



Gotta love those $15 contactors from battery hookup:



Ever wonder what the surface of the sun looks like?:



I'll post the results of the discharge test next...

Probably best to document this chronologically.

Pack started at 41 deg F in the basement that was also 40 deg F:



10:53 First stage was heating the battery. Heat started:



11:06 Heating to about 68 deg F finished:




Summary: Pack was heated about 27 deg F in about 13 mins.

11:07 Second stage was fully charging battery. Charging was started:



11:31 Charging finished. Looks like some imbalance...



11:46 6 kW discharge started:





11:59 About halfway through test:




JK BMS doing well thermally (warm P- leads are my fault because I forgot and only finger tightened that connection!):


12:10 Discharge complete:



Summary: See .pdf. Cooling blower was run for the entire discharge. Battery temp peaked at 83 deg F. Looks like about 57 Ah were delivered. JK BMS shunt was a little off and corrected to what a clamp meter was reading.

Thoughts? It looks like some differences in internal resistance maybe?

Assuming the remainder of the energy went into internal heating,

60 Ah cell design capacity - 57 Ah measured capacity = 3 Ah

3 Ah x 2.9V = 8.7 Wh per cell

8.7 Wh / .4 h test duration = 22 W internal heating per cell

This seems low to me, given the change in cell temp with 40 deg air being forced through the heat sinks during test.

Anyone have experience with high C-rate behavior?

Great test. Thank you for posting your results.

I can't comment on hight load behaviour of cells. No experience with that. The voltage drop seems to be about 0.6v per cell for a 2C load. That seems OK to me.

Other observations:

Your heating and cooling solution seems to work very well. 81F seems like very reasonable temp for operating.

100mv is pretty big cell deviation on charging, even at around 3.5v. But if you have not been charging the pack to 100% regularly, perhaps this is the cause? That cell #9 is the one to watch. Perhaps some slightly higher internal resistance and some higher self-discharge? Overall, seems like a minor issue however.

Your heater load-test is a resistive load, so your 200amp BMS should be able to handle that fine. My understanding is that issues with a FET BMSs can arise from inductive loads (motors) where the initial start-up current can be 4x - 5x the sustained load and close to a dead-short if the motor stalls.

MP

Marinepower said:

My understanding is that issues with a FET BMSs can arise from inductive loads (motors) where the initial start-up current can be 4x - 5x the sustained load and close to a dead-short if the motor stalls.

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I am hoping that an AC induction motor run via a curtis controller might be a different beast? I can control max motor currents via settings in the controller.

Marinepower said:

That cell #9 is the one to watch. Perhaps some slightly higher internal resistance and some higher self-discharge? Overall, seems like a minor issue however.

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I was thinking the same thing, but then cell #16 was the limiting factor on discharge...? Curious

bestconcreteblock said:

I am hoping that an AC induction motor run via a curtis controller might be a different beast? I can control max motor currents via settings in the controller.

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That could very well be the case. I don't know enough to comment. The start-up surge current i was describing i know occurs with series wound motors...

bestconcreteblock said:

I was thinking the same thing, but then cell #16 was the limiting factor on discharge...? Curious

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Likely cell #16 just has slightly less capacity. 100mv deviation down at 2.6v , 2.7v is not a lot capacity difference. You are always going to be limited by your lowest capacity cell. Seems OK to me.

I temporarily removed tail current cutoff in my charger and held the pack for several hours at 3.55/cell to give the JK BMS a chance to balance things better. It seemed to help.

I used the same procedure and did another capacity test:

Charging finished:



Start of discharge:



Middle of discharge:



End of discharge:



It's really interesting how cells react differently at different times during the discharge. It still looks like #16 is the lowest capacity.

This time the pack delivered 59.75 Ah. See attached .pdf

Awesome work! Congrats and thanks to shared.
Is I missed the function of this battery and those HPEV motor?

yabert said:

Awesome work! Congrats and thanks to shared.
Is I missed the function of this battery and those HPEV motor?

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Thanks, application will be a walk behind tractor that can run a variety of implements:
https://www.earthtools.com/tractors-grillo/g107d/

bestconcreteblock said:

Thanks, application will be a walk behind tractor that can run a variety of implements:

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Nice! Really cool and useful tool.
Is there reasons you don't used off the shelf 48V battery like Roypow (contactor BMS), Epoch or Dakota lithium build for golf cart?