Lithium, Mixing Sinopoly LFP and Winston LFYP Cells??

[Firegirl54]

Has anyone experience whether Sinopoly 100AH Cells can be successfully paralleled with Winston 90AH cells?
We have run 12V 100AH Sinopoly for 2 years in our small off-road van and are considering doubling capacity. Our black Sinopoly cells (61×142×221, 3.1kg) are a very close physical match to the 90AH Winstons (61×143×218, 3.0kg). From the pics the ribs seem to match. Capacity testing at 12mths yielded 89AH, then 93AH after a couple of full cycles, and at 2yrs we got 92AH. Did not do a capacity test when we first got them so don't know whether they have lost much capacity. We hope to use pairs of one sinopoly and one winston. But is the chemistry compatible?
I seem to recall reading somewhere (CF?) that Terry experimented with Winston LFYP and LFP (which later evolved to Sinopoly?) and found that they worked together OK, but can't find the detail. The Winston cells are cheaper, probably better in our applications, and more readily available here in Aust.
Any thoughts?
(By the way, the Winston 100AH "tall" version match also for height and width, but are 6mm thicker and heavier at 3.3kg.....Winston are more generous with their 100AH Rating!)
Leslie

[BruceS]

Hi Lesley & a big welcome to the forum.
Terry is currently packing for his trip to the West to do a couple of jobs so I hope he gets time to answer your question.
Last report I think he'll be heading off later tomorrow so keep your fingers crossed!
If you get time maybe a few details about your outfit in the relevant section & in your profile would be good!

[native pepper]

Lesley, you may have problems with different capacity cells when charging as one will reach it's capacity before the other. It's no different to charging a 90ah and 100ah lead acid battery in parallel, one will reach capacity first, create an imbalance in the cells and could cause a thermal runaway by trying to push more capacity into the 90ah cells as it tries to get the other cells to 100ah. You could put your charge controller on the 90ah cells and then 100ah would stop charging when the 90ah cells reached capacity.

As Bruce said, Terry can tell you more, but to me different capacity cells charging in parallel could lead to problems.

[BruceS]

I doubt if there'd be a problem.
If you set it up so you had 1 X 100 & 1X 90 in each "cell" & then hook those 4 similar ones together you'd get 190Ah @ 12V (nom).
I already know of someone (not mentioning who!) that has the 2 dif sorts mixed with no problems.
Regardless .... as you know? .... monitoring cells in essential!!

[Busman]

I know at one time T1 had some Sinopoly cells mixed with his Winstons, and also a mix of old and new cells and he reported that they worked all right.
However the Sinopolys have less capacity than the Winstons, that is a fact from a discussion I have from Trev (100 Ah against 100 Ah sizes)
So, I would say you could do it as Bruce has said above but err on the safe side when you set your charging voltages.
I have 64 100 Ah sinopolys and I can tell the capacity difference from the Winstons myself.
Cheers
William

[bagmaker]

are the knee's at the same voltages?

[Firegirl54]

Thanks Guys!
Good to hear some practical experience that the cells play well together. I had assumed from an awful lot of reading that they would, but best to check.
I do monitor the cell voltage.....my husband thinks I get carried away and I suspect he is right! The Housepower BMS that we have is an overkill for this little pack, but it was a fun project....It is set up to drop the charge bus at pack voltage >14.4, and the load bus at <11.6, and reconnect automatically at 13.8 and 12.4 respectively. Additionally it drops both if any cell >3.65V or <2.6V, and then needs a manual reset. So far the only disconnects have been in testing. Have manually monitored cell voltage at top and bottom. Pack is top balanced by the dreaded cell boards nominally at 3.55V per cell, max 700 mA, but some current starts to shunt at 3.50V, biggest dV at this end 40mV, and no cell ever reaches 3.6V. At the other end, at pack V 11.6, largest dV has been 140 mV, with lowest cell at 2.85V. In use the lowest pack voltage has been about 12.4 with 118A load.
Have just bought a celllog 8S to more easily watch the cell voltages...especially when I'm not looking! With addition of a little NC relay I may also use it to ditch the cell boards. I don't entirely trust them and they have a continuous small parasitic draw when van is unused.
Cheer and thanks again, Leslie

[wazzaaaa]

I think there will always be a debate on charging different capasity batteries in parallel, i personally don't see a problem.
As far as each battery is concerned they are effected only by the voltage they receive and are constantly equalizing.
one can not charge earlier as the voltage will be the same for both.

[T1 Terry]

Hi Leslie and welcome to both the forum and the wonderful world of upgrading lithium battery capacity.
Depending on the current (amps) you used for the load test as to how well the Sinopoly cells are holding up. After reading mega crap loads of stuff about the Sinopoly cells I actually ended up with a load of them from an abandoned EV project, still in their wooden boxes never used. In amongst all the boxes I found a Sinopoly book that listed out the test methods used and that was where it all became clear as mud. Winston use a 0.5CA (50% of the rated capacity in amps) as their test load for capacity testing and the average over 3 fully cycles from 100% to 2.6v which is actually below the 0% SOC point.... I know, doesn't sound right but 100% SOC of a 100Ah cell means 100Ah has been extracted, at that point the cell is still better than 3v even under load, so their testing was to the extreme limits and repeated 3 times.
Sinopoly on the other hand, Sinopoly use a 0.3CA load and the 100% capacity is measured at 2.5v under load, so the same test as Winston use would result in a lower capacity before the 3v threshold was reached or on the other hand, the Winston LYP cells would be rated at a lot more than 100Ah using the Sinopoly test method.

Ok, now for the question, can the 2 brands using cells of a different age and potential capacity be built into a single battery using the cells in parallel to build capacity and groups of these in series to build voltage..... yes, they can. The only issue is the physical size when it comes to compressing them for end plates and strapping. If the grooves line up and the width is the same, the thickness is not an issue, the straps just need to be long enough to wrap around each end plate to secure the cells into a pack.
As you probably already know, the cells must be compressed with end plates and strapped to stop them bulging resulting in lost capacity. Ignore the nonsense that bulging only happens if the cell is overcharged or over discharged, the buggers will bulge sitting on the shelf and the 90Ah Thundersky cells we pulled out of the boxes that were 3 yrs old since manufacture were already bulging yet had never been used.... made them a right pain to get out of the boxes Sinopoly actually strap their cells in the packing crate in groups of four to stop them bulging, so the manufactures know it happens. The ready made 90Ah 12v Winston batteries are actually end plated and strapped and then fitted into the plastic case proving that the manufacturer knows they need to be strapped before use.
Can you post a photo of your battery pack?

T1 Terry

[Firegirl54]

Hi Terry,
Thanks for the detailed reply. The cells are in a wooden box that my husband made designed to compress, and well bolted to van floor. I know wood is not ideal for cooling, but so far even after 5 mins at over 100amp discharge the cell terminals are still cold....now to work out how to add the pics......Well after some resizing that worked! Sorry re image quality. Battery and inverter live under the seat but the perspex cover reflects too much. You will also have to squint a lot to see the threaded rods on each side. The BMS and relays are in the grey box in the under table shot. Charging bits live in front box. The big CB is just for roof solar and used mostly just as a convenient switch so I can turn it off if charging from car or from portable panels when van is in heavy shade. Locations mostly so I could easily remove the lithiums and return the AGM system if we ever change vans. Inverter is not directly included in LVC, but via a relay from load bus and its existing remote controller, avoiding using a jolly big contactor. This is really just an added safety in case we forget to manually turn it off immediately after use.