Anyone buying these 305ah envision cells?

[42OhmsPA]

How can you balance cells effectively below 3.4V?

You can't. But I've found it does help as a temporary solution for packs that are way out of balance.
Example - I currently have mine set to turn on at 3.39V with float set to 54.4V (3.4V / cell)
I have/had a cell that was running pretty bad driving the pack voltage up, with the above voltages I was able to keep the runner balancing a bit sooner and remaining cells lower... Runner would hit 3.5xV with the rest ~3.45V. When bulk V was attained the rest would rest while the runner would bleed off.

Note I'm far from and expert and am using passive balancing JBDs. The above worked for me and isn't optimal.
If I were When I start running a passive balancing BMS I would set balance to initiate at 3.42V and not worry about it.

I'm willing to learn more everyday... Feel free to school me more.

 

[houseofancients]

You can't. But I've found it does help as a temporary solution for packs that are way out of balance.
Example - I currently have mine set to turn on at 3.39V with float set to 54.4V (3.4V / cell)
I have/had a cell that was running pretty bad driving the pack voltage up, with the above voltages I was able to keep the runner balancing a bit sooner and remaining cells lower... Runner would hit 3.5xV with the rest ~3.45V. When bulk V was attained the rest would rest while the runner would bleed off.

Note I'm far from and expert and am using passive balancing JBDs. The above worked for me and isn't optimal.
If I were When I start running a passive balancing BMS I would set balance to initiate at 3.42V and not worry about it.

I'm willing to learn more everyday... Feel free to school me more.

Balancing is effective pointless below 3.45.
What will work is a float just above 3.45-ish and keep them there to the balancer can do it's thing.

Best in any case is to do a proper top balance before you put them in series/production

 

[42OhmsPA]

Balancing is effective pointless below 3.45.
What will work is a float just above 3.45-ish and keep them there to the balancer can do it's thing.

I was doing that until I, most likely, read way to far into plating / degradation holding at higher voltages. My thought process was get as many cells down while bringing the runner down with the passive balancer.
It has definitely worked, my deviation has improved significantly.

Best in any case is to do a proper top balance before you put them in series/production

I agree 100%. My two 230 packs were top balanced per the guide; they are much better than the non top balanced pack.
I was excited to get another pack online to take advantage of the finished ground mount and I'm impatient.

 

[a619]

I top balanced these envision cells and they have stayed within 5mV at 55V with just the bms passive balancer. These packs see 80% dod almost everyday.

 

[Zwy]

You can't. But I've found it does help as a temporary solution for packs that are way out of balance.
Example - I currently have mine set to turn on at 3.39V with float set to 54.4V (3.4V / cell)
I have/had a cell that was running pretty bad driving the pack voltage up, with the above voltages I was able to keep the runner balancing a bit sooner and remaining cells lower... Runner would hit 3.5xV with the rest ~3.45V. When bulk V was attained the rest would rest while the runner would bleed off.

Note I'm far from and expert and am using passive balancing JBDs. The above worked for me and isn't optimal.
If I were When I start running a passive balancing BMS I would set balance to initiate at 3.42V and not worry about it.

I'm willing to learn more everyday... Feel free to school me more.

Great minds think alike, I changed my Batrium to start balance at 3.39V some time ago. https://diysolarforum.com/threads/issues-balancing-with-batrium-bms.54418/post-930976

That would be the lowest cell voltage, once the lowest cell hits 3.39V, bypass is enabled. I have some cheap cells from Amy that weren't matched for internal resistance and a few are runners. When bypass starts, the highest cell is already above 3.5V. Some day these will go in my electric golf cart and I will install some better matched cells.

These were top balanced as a complete 16S pack. With a BMS until one cell hit 3.65V. Then in parallel until amps dropped to nothing. Those cells still won't hold balance. I could add an active balancer to help with balance on those cells, most likely when they go into the cart I'll install one. The Batrium does a pretty good job with 0.75A passive balance. It does generate heat on the K9 heatsink. I could add a fan and increase bypass amps. I have never seen the need to however.

 

[Surferdudemi]

The spec sheet on these cells says they are at 100% SoC at 3.348V. What voltages are you folks using when you test the capacity? I've got a 4-pack on a charger that goes to 3.65V per cell, still pushing its 10A max rate into cells at 3.36V each. OC voltage looks like it's going to settle between 3.50V and 3.55V when I disconnec tthe charger, so still above the spec.

 

[nickj]

Anyone get any shipping notifications for these cells?

 

[Culchee]

Anyone get any shipping notifications for these cells?

Where are you buying the cells Nickj... at the moment it’s either 18650.. Fogstar or NKON...

 

[nickj]

Where are you buying the cells Nickj... at the moment it’s either 18650.. Fogstar or NKON...

Sorry I meant 18650

 

[shavermcspud]

My input on these cells, I purchased some from a UK company called Fogstar, Envision 305Ah grade b.

After receiving the cells, checking each visually, running an Internal resistance check on each cell to compare against the name plate rating and finally a top balance of all cells to 3.65v per cell in parallel before assembling the pack in to a 16s configuration in the supplied Seplos case with 200Amp BMS. unfortunately these do not perform very well at all at anything over a 0.2c discharge rate when the SOC is around 50%, barley 210Ah usable before low voltage cut off at 2.9v per cell, after cut off they bounce right back up to 3.1v per cell showing these are very low grade cells possibly heavily pre-used and re wrapped. I repeated the test after a full charge to 3.60v per cell then a further discharge with a 0.1c discharge rate and achieved a little over 279Ah this time. They seem to perform better at higher discharge rate around 3.3v per cell and then it all goes downhill once they are around the 3.2v mark. Appreciate they are B grade cells but not being able to pull 50Amps at a 50% SOC before a low cell warning isn't what i expected. I have tested and built many different cell types and manufacturers / grades and these are very very poor quality.

For some reason my review on their website keeps being removed.

 

[shavermcspud]

Here you can see (highlighted) when a 40Amp DC load is applied at around 45% SOC 3.1v per cell, the cell voltage drops off a cliff down to 2.9v in under a minute. Test performed today, 15 Degrees C temp from a fully charged pack that was ticking over around 10Amp discharge all day. You can see the voltage bounce backup after the low voltage cut off around 11.30

 

[houseofancients]

My input on these cells, I purchased some from a UK company called Fogstar, Envision 305Ah grade b.

After receiving the cells, checking each visually, running an Internal resistance check on each cell to compare against the name plate rating and finally a top balance of all cells to 3.65v per cell in parallel before assembling the pack in to a 16s configuration in the supplied Seplos case with 200Amp BMS. unfortunately these do not perform very well at all at anything over a 0.2c discharge rate when the SOC is around 50%, barley 210Ah usable before low voltage cut off at 2.9v per cell, after cut off they bounce right back up to 3.1v per cell showing these are very low grade cells possibly heavily pre-used and re wrapped. I repeated the test after a full charge to 3.60v per cell then a further discharge with a 0.1c discharge rate and achieved a little over 279Ah this time. They seem to perform better at higher discharge rate around 3.3v per cell and then it all goes downhill once they are around the 3.2v mark. Appreciate they are B grade cells but not being able to pull 50Amps at a 50% SOC before a low cell warning isn't what i expected. I have tested and built many different cell types and manufacturers / grades and these are very very poor quality.

For some reason my review on their website keeps being removed.

This not normal behavior for these cells, and no where near where my tests and builds are ending up..
Contact fogstar, have them swap them out..
I believe you are in the uk correct ?
Get on the phone with them

@Ben@Fogstar..
This can't be right

 

[shavermcspud]

This not normal behavior for these cells, and no where near where my tests and builds are ending up..
Contact fogstar, have them swap them out..
I believe you are in the uk correct ?
Get on the phone with them

I know, I have built probably 80+ packs now and not seen any quite this bad even from B grade cells. I've had them two weeks now, a week to top balance them and then assemble them and test. Unfortunately they are not open at the moment due to Christmas.

 

[houseofancients]

I know, I have built probably 80+ packs now and not seen any quite this bad even from B grade cells. I've had them two weeks now, a week to top balance them and then assemble them and test. Unfortunately they are not open at the moment due to Christmas.

Yeah, I'd contact them, make sure they make you whole

 

[SupraSPL]

18650 battery store just started shipping those pre-orders. I assume it's a new batch from China so hopefully they are just as good or better.

My 24V bank is big enough that it never gets pushed hard in terms of C so I can't speak to the post above (maximum is 0.12C for charge or discharge). They stay balanced very well with JBD passive balancing and it very rarely gets a chance to balance the way I have it set up.

Still experimenting with the BMS settings to try and maintain the most accurate state of charge reading for each battery in the bank between full charges.

 

[SupraSPL]

Double posted

 

[Kornbread]

Was very tempted try the $75 preorder.

If these envision cells are similar to the 64 'grade b' 304ah Eve cells from 18650, you will have some runners and possibly a ?. Out of the first order of 32 cells, there was an outlier that voltage wise, was considerably out of line with the others. 18650 was quick to replace it. Based on that good experience, ordered 32 more of the 'b' cells. With the second order, there are six runners, four of which really hold things back, even with the 2amp active balancer of the jk bms. Regarding the second order from 18650, never received an answer on a dented cell and another voltage outlier. Had to put them into service.

It would be nice to know how these individual cells balance out after some usage.

 

[Culchee]

Was very tempted try the $75 preorder.

If these envision cells are similar to the 64 'grade b' 304ah Eve cells from 18650, you will have some runners and possibly a ?. Out of the first order of 32 cells, there was an outlier that voltage wise, was considerably out of line with the others. 18650 was quick to replace it. Based on that good experience, ordered 32 more of the 'b' cells. With the second order, there are six runners, four of which really hold things back, even with the 2amp active balancer of the jk bms. Regarding the second order from 18650, never received an answer on a dented cell and another voltage outlier. Had to put them into service.

It would be nice to know how these individual cells balance out after some usage.

How are your grade b packs working out..?

 

[Kornbread]

How are your grade b packs working out..?

About what would be expected. Some cells drift a little lower but as a whole, the runners tend to hold the pack back. They are probably in a worse case scenario for 'grade b' cells. The property is surrounded by large trees and some will eventually be fell, but downing the large Oaks and Pecan, which are the main shade offenders, is not an option. Anyhow, due to considerable shading, this creates a very small window for the solar panels and chargers to do their thing, especially during winter where the low Southern sun gets blocked by even more trees. Do to all this shading, the cells don't get to spend a lot of time above a decent balancing voltage leading to a bit of cell mismatch lowering overall capacity.

 

[SupraSPL]

The new batch of cells landed today, a pack of 310s and a pack of 315s. 3.291-3.292V. The stickers dated October 29th/30th 2023. 3 cells have a slight bulge the rest look flat. Works for me ?

If everything goes smooth this year maybe prices will keep coming down but if Taiwan thing goes down who knows.