AVASS cells 2nd lot

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offgridQLD
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AVASS cells 2nd lot

Post by offgridQLD » Tue, 23 Apr 2019, 19:40

I was one of few who ended up with 16 of the 460ah lifepo4 cells from the AVASS bus. I was surprised that there hasn't been more discussion or shared info regarding the cells from the first round last year. Unless there is and it's not on this forum? I thought I would share my thoughts on them and what I plan to do with them.

I was one of two people in SA that received them this round. I got 18 cells for a 16 cell battery bank + two spare. One for me and another if the other member needed one. Or if one of us got really unlucky and need two.

My first impressions looking at the little plastic-wrapped pallet was that sure doesn't look like 34x460ah lifepo4 cells. Have we ended up with 200ah cells ? Just going off the size of my old 400ah Calb cells. Sure enough they had 460ah stickers on a few cells so at least the factory thinks they are 460ah. Must be more energy dense than the calb cells or the aluminium case is consuming less volume than the plastic Calb case.

All the cells looked the same but one cell had a diffent heat shrink on top (looked like the ones from last year) I took that one as one of the two spares in case it was unbalanced in age or cycles to the others. We tried to find some kind of pattern to the numbers on the stickers on top of the cells along with the barcodes but looks like the cells were a bit random as there wasn't a real sequence, so we just split the cells up as they were packed.

Was a small challenge to transport the cells 1 hour drive in the back of my ute. I wanted to stand them upright as a big 18-cell brick and then just pallet wrap the hell out of them, then run x-shaped tiedowns to the 4 corners of the tray. Why I didn't want to lay them down was one very strange thing about the cells that I have never experienced with any other lifepo4 cell is that if you shake the cells you can hear a slight sloshing of a liquid. I found this very odd for a prismatic lifep04 and didn't want to lay the cells down.

The next day I laid them out in the shed to go over the cells. Running the meter over them they all read 3.30v. I then took a reading from the terminals to the aluminium case and was shocked to find that I got a reading from the negative terminal post to the case on every cell. Not the full cell voltage but some were around 3v. I then looked at the wimpy looking blue heat shrink on the cells and thought there is no way I am going to strap them all together as a brick with just paper-thin heat shrink as insulation. Particularly how some of the weld seams on the case protrude ever so slightly and would create pressure points to rub through or pierce the heat shrink. I plan to use thin rubber insulating mats between each cell to take up any slight surface imperfections and give better insulation of the live case.

Close inspection with a straight edge found just one cell has a very slight belly to it, so I marked it and will see if I want to swap that out for a spare if it underperforms.

The cells came at a very good time for me as I have just moved into our new offgrid house build and was just about to purchase 16x 400ah calb cells. I had been limping along on 32x 40ah worth of 2nd hand calb cells so I was under pressure to improve the battery situation. That said, I was keen to get the Avass cells up and running ASAP.

1st step was to use the included cells connections and bolts to get them all wired up into a 16 cell bank. I decided to arrange the cells into one big long skinny row of 16. This was partly due to how I wanted to fit my cell top monitors to clear the centre vent.

Now I had no idea what SOC the cells were in or if the SOC of each cells was even close. One way to find out and that was to charge them. I was in a hurry so took the dirty option and had the 8kva generator power a Victron inverter charger set at 5kw output. With me watching over them with a few meters to catch the first cell to reach 3.6v. Not long after, I caught the first cell at 3.6v. They had soaked up roughly 6 or 7kwh (I didn't have the current shunt connected to them so was a rough number from the generator's display) Obviously charging at around 100A, it was going to take some more fine-tuning to ensure all the cells were topped off gently to 3.6v.

Unfortunately because I am 100% offgrid (struggling along on my temporary small bank), I had to top off each of the 16 cells with two 7A lithium hobby chargers powered by two 12v batteries that were charged with a spare solar panel, so it took several days. Most of the cells needed around 20 - 30ah top off to get them to 100% full, though one cell was a little hungry and needed about 40ah. So they were a bit out of balance. This gave me around 1kwh on top of the 6 - 7 kwh from the fast charge.

Finally with them all full at 3.6v and the big question looming........how much capacity are they? At this stage I knew they were at least 7 - 8kwh but that's just 30% of the sticker capacity. Let's just hope they came 60 - 70% charged!

So I connected up my Victron 712 battery monitor shunt meter and entered in 400ah as the capacity. I wanted to be a little conservative to start with, but had to pick a number. Wired the inverter to the bank and disconnected any solar input. It was time to run them down and see what they return. I will take them down until the first cell hits 3v and call that empty. I'm powering this pc from them as I type and I have about 100ah out of them. I could drain them down faster with larger loads but wanted a more realistic average load they will see over the days.

I will report back with my results and add to this post tomorrow with what battery managment system I am using and how I plan to mount the cell top monitors/balancers I had already purchased for the 14mm terminal Calb 400ah cells, so some creative thinking was required to make it work on the avass cells.

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Re: AVASS cells 2nd lot

Post by Dan007a » Tue, 23 Apr 2019, 20:46

Watching with interest.
Last edited by Dan007a on Tue, 23 Apr 2019, 20:46, edited 1 time in total.

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Re: AVASS cells 2nd lot

Post by dgh853 » Tue, 23 Apr 2019, 20:46

The discussion of using the AVASS cells is in the AEVA Cell Mates facebook forum at https://www.facebook.com/groups/252080995574519/.

Request access to the forum and you'll be able to browse a good information that has been posted by many who have already built up their packs.

To save you some time, capacity tests on the cells were done on the first round of cells. Mine came very close to the 460Ah. The charging profile is very flat with 3.0V => 5% SOC and 3.4V => 99%. I wouldn't recommend charging anywhere near 3.6V as the voltage increases very quickly past ~3.45V. I currently charge to 54.5V (3.4V each).
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Re: AVASS cells 2nd lot

Post by jonescg » Tue, 23 Apr 2019, 21:36

Hey Kurt,

Yeah the sloshing was a bit unusual, but these cells have been pulled out of a working bus and I think they were laying down in that instance. Either way, its not a big deal to lay them down, at least during transport. The aluminium case shouldn't be galvanically connected to the cell terminals, but if they are, you will fast know about it. I agree - keep some kind of insulation between them, even if it's just a few strips of Kapton tape. A bit of capacitance is normal though.

I'd personally connect them all in parallel and charge to 3.5 V. That way you know they will all balance to the same voltage, and at 3.5 V there is enough potential to drive that current. Most folks were finding 400 to 440 Ah capacity, which considering the price is pretty good.

I also think these cells would have made for a very lousy electric bus. Not particularly powerful and the cells themselves don't look robust enough to survive the rigours of a road going vehicle.
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Re: AVASS cells 2nd lot

Post by Dan007a » Wed, 24 Apr 2019, 03:54

What drives did these buses use.
And what has happened to them

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Re: AVASS cells 2nd lot

Post by offgridQLD » Wed, 24 Apr 2019, 07:25

Thanks for that info, I will try and resuscitate my old facebook account to take a look.

Anything over 400ah is a bonus :) I just wasn't sure if anyone had performed a capacity test on this 2nd round of used cells from the buses and the results could be different?

No intention to charge the cells to 3.6v after commissioning. It was more to do with the individual cell level chargers I was using. That had a non adjustable lifep04 end voltage. Then me wanting something I could walkaway from and have it terminate the charge at the same point for all cells. Though really as mentioned the last few Ah after 3.45v went fast as the Amps tapered down to almost nothing. No real aggressive over charging going on.


I will be using the Batrium battery managment system and as mentioned befor I had allready purchased the blockmons for the M14 calb cells terminals so they are not a good match for the terminals of the Avass cells. My plan is to use some of the shorter terminal links (that this round of cells came with many extras) to creat a stand off to the side of each negative post. The Blockmon will bolt to one end of the terminal link and be suspended in mid air to the side of the cell. The short cell links are stiff enough to hold the cellmon.Particualy for stationary storage. One bonus of this aragment is the great airflow around the cellmon when ballancing. The fartory fly leads are a nice length to span the axtra distance on the relativly narrow cells with the cellmons out to the sides.

I have two Victron 85A 48v charge controllers that will manage pv DC/DC charging. Pv is aranged in a fixed mount (vertual tracker) arangment where 1/2 the panels are facing NE on one controller and the other 1/2 NW on the 2nd controller to avoid the midday peek. Most likely a good thing with the Avass cells as the specs I have seen didn't encorage much over 5000w charging continuouse. I also have a small 600w 48v wind turbine that I will use through the PIP4048's onboard charge controller as my new location has wind thats actualy worth the efort. backed up with the Victron Quattro 110A charger on the generator that I hope dosn't get much use at all.

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Re: AVASS cells 2nd lot

Post by jonescg » Thu, 25 Apr 2019, 10:33

How'd you go Kurt? 48 V and 440 Ah?
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Re: AVASS cells 2nd lot

Post by doggy » Wed, 01 May 2019, 19:40

Thanks for this info. It will save me some work! Sounds like the cells must have been around 80% SOC or higher. At least they do not appear to be 100%. I do not have any spares for my 8 so I am hoping they will all be okay. Their OCVs were all quite close. However, that does not mean much.

I'm not on Facebook and do not intend to join so I cannot access that info.

If there is any other source of info I would appreciate a link.

The main thing I was after was charge parameters, but it sounds as if 3.45Vmax and 2.9V min might be best? I will be charging at less than 100A but would like to pull up to 200A with a 5kW inverter.

Cheers,
Dave

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Re: AVASS cells 2nd lot

Post by jonescg » Wed, 01 May 2019, 21:13

Yeah avoid that digital cesspit if you can.
http://www.brighsunauto.com/Ch/ProductView.asp?ID=4
I think 200 A discharge won't be a problem at all. They are technically good down to 2 V but I think 2.5 V is effectively empty. There is nothing to be gained by charting to 3.65 V, indeed the difference between 3.45 and 3.65 is about half an amp hour for a cell this big.
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Re: AVASS cells 2nd lot

Post by doggy » Thu, 02 May 2019, 04:54

Hi Chris, many thanks for that.
I've attached a translation for those who need it.
Regds,
Dave
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Re: AVASS cells 2nd lot

Post by doggy » Sun, 05 May 2019, 06:33

A question.
Why are people using SS bolts with the AVASS cells?
Why did the AVASS people use SS?

I have large capacity battery banks on two different boats and have always used copper for busbars and brass bolts/nuts. The conductivity of brass, thougth not as good as copper is much better than SS.

So my first thought was to use brass on the AVASS cells. Any thoughts why this might not be best (other than really expensive and soft copper bolts)?

Thanks,
Dave

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Re: AVASS cells 2nd lot

Post by coulomb » Sun, 05 May 2019, 09:59

doggy wrote:
Sun, 05 May 2019, 06:33
Why are people using SS bolts with the AVASS cells?
Pretty much everyone uses stainless steel bolts. It's the best compromise with compatibility with the copper straps, availability, and so on.

Yes, the conductivity of stainless steel is quite poor. But little current should be flowing through the bolts; the vast majority should be through contact between the terminal of the battery and the copper strap. The extra conductivity of brass bolts is no help, and the softness could be a problem.
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Re: AVASS cells 2nd lot

Post by doggy » Sun, 05 May 2019, 11:18

Hi Coulomb,
Thanks for that info.
I might compromise slightly and use SS with some copper washers.
I have to replace the supplied SS bolts so I can add my BMS boards over the vents.
Cheers,
Dave

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Re: AVASS cells 2nd lot

Post by doggy » Mon, 15 Jul 2019, 17:07

Some info:
1. I finished my 60A charger and home grown BMS some time ago. I am using the system to gather exportable excess solar and then put it into my EV as required. The charger tracks the excess solar and adjusts charge rate appropriately.
2. I carefully balanced the cells in parallel (3.500V and <2amps) before immediately discharging them.
3. I am getting between 400 and 420AH out of 8 of them in series, running a 5kW inverter and 195 to 210amps.
4. I am stopping discharge when any cell hits 2.8V. I stop charging at 3.48V on any cell or when charge current is below .025C and volts averaging 3.4/cell.
5. Internal resistance is coming in at about 0.5 milliohms per cell.
6. When 210amp discharge stops because of a cell starting to get low, if I drop the current drain to 60amps, I only get a few more amp hours out of them. So 400-420 is max for me.
7. I started with S/S bolts and nuts with the BMS modules mounted over the vents. However I found this fiddly even after making a special S/S insulated spanner. So now I am using brass posts, brass nuts, copper washers and conductive paste. Terminals are cooler with max temp rise 15deg at 220 amps. Cabling is short and I am using 75mm2 with hydraulic crimped connectors.
Cheers,
Dave

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Re: AVASS cells 2nd lot

Post by jonescg » Mon, 15 Jul 2019, 18:38

Wonderful to hear its working out for you David!
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Re: AVASS cells 2nd lot

Post by doggy » Mon, 15 Jul 2019, 19:55

Thanks Chris,
It's all been more work than predicted- what a surprise!
The only thing that puzzles me a little is the AHs as I had expected around the 460.
The extra 60 would be nice. However, 400 is okay for my application and the price for that was fantastic.
I have a separate setup with 8* CALB180s and they also don't give the rated AH.
I have typically been charging at 15degC and at the end of the last couple of discharge runs (200amps), the cells have started around 15deg and ended up at 20degC.
So possibly there is some reduction in capacity due to temperature.
Also, even though the AVASS cells have stayed in good top balance, two of them always hit the discharge turnoff point first. So, they are not very well matched but by how many AH it is hard to say. Certainly not 60AH, but from my observations it could be 10-15AH.
Best Regards,
Dave

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Re: AVASS cells 2nd lot

Post by jonescg » Mon, 15 Jul 2019, 21:07

Yeah, that sounds about normal. The cold weather can't be helping either. A really good balance charge feature is a good choice for these cells. It prevents overcharging a cell and shortening it's service life even further.
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Re: AVASS cells 2nd lot

Post by T1 Terry » Tue, 16 Jul 2019, 14:27

Looking at the specs, the 460Ah capacity is @ a 0.2CA discharge rate, not the 0.5CA rate you are discharging them at. I found the Sinopoly cells had a similar issue, their advertised 100Ah cells would only deliver 100Ah down to 2.8v if the discharge was restricted to 0.2CA. At the 0.5CA we use for the Winston cells the 100Ah Sinopoly cells only deliver 80Ah.

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Re: AVASS cells 2nd lot

Post by doggy » Tue, 16 Jul 2019, 15:00

Thanks Terry,
Yes, 200A is quite hefty.
At .43C I am getting 89% of theoretical which does compare favourably with your 80% for the Sinopoly cells plus the slightly lower temperature and the fact that my AVASS cells are only roughly matched. However, I do have them well (top) balanced.
At some stage I'll run a test at 0.2C or 92 amps. My EV charger loses efficiency at 2.3KW but it will be worth a run to see what happens in terms of AH.
Thanks,
Dave

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Re: AVASS cells 2nd lot

Post by doggy » Sun, 21 Jul 2019, 19:07

Okay, I have now done a run at 95amps (92 would be 0.2C).
Definitely an improvement.
I extracted 435.6AH. Current measured by clamp meter which was almost the same as that measured across 200A shunt.
After 30mins, all cells were within +-5mV of one another. +-8mV at 3hrs.
With 10mins to go, the cells were all within +-32mV. I stopped at 2.8volts per cell- there were two that hit this voltage.
I got 10.33kWHrs from the 8 cells.
Compared with the 200A run, everything was almost totally cool reflecting lower losses.
So I'm pretty happy with that.
I fed it into my EV and the EV recorded 9.6kWHrs into its battery. That's also nice.
Cheers,
Dave

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Re: AVASS cells 2nd lot

Post by mikedufty » Mon, 22 Jul 2019, 13:35

I don't think I'm going to be able to use my cells in the near future.
Is there anyone who missed out, who would like to buy them?
Set of 16 (~48V)

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Re: AVASS cells 2nd lot

Post by Dan007a » Thu, 25 Jul 2019, 21:21

Send me a pm for your price

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Re: AVASS cells 2nd lot

Post by mikedufty » Fri, 26 Jul 2019, 14:01

Hoping to sell them at the original offer price from AVASS $2,040 for the lot.
Seems nice to keep them in a set that will do 48V, but I'll consider splitting up if I can sell at least half of them.

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Re: AVASS cells 2nd lot

Post by jeffthewalker » Sat, 27 Jul 2019, 13:22

I am interested in the lot. However, I am in Emerald Queensland. Any idea of cost to freight the lot?

Thanks,

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Re: AVASS cells 2nd lot

Post by mikedufty » Sat, 27 Jul 2019, 15:09

No idea, I think Chris Jones organised the shipping to WA.
It was only $120 to get them shipped to WA, but that was as part of a bigger bulk shipment, I suspect it may be a fair bit more on their own.

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