Docan 8x EVE 280ah slightly swollen

[Ampster]

they are all swollen like in the pictures jay_jay posted

As far as I can tell that is nothing to worry about. Compress them and test them if you are concerned. The capacity is what you bought not the physical shape. If you don't want expansion, buy ribbed prismatics at $300 per kWh.

 

[gonmag8]

My 16 just arrived and are like the pics too.
I thought this to be normal, now not sure?

 

[Mr Q]

As far as I can tell that is nothing to worry about. Compress them and test them if you are concerned. The capacity is what you bought not the physical shape. If you don't want expansion, buy ribbed prismatics at $300 per kWh.

I fully agree on the capacity. If they are the Ah I paid for I will be happy, just didn't expect them to be swollen.

 

[Ampster]

I will be happy, just didn't expect them to be swollen.

The thin cases are susceptible to pressure, more so than the ribbed prismatics. That is why the manufacturer recommends a fixture.

 

[jay_jay]

Well, more like a real indicator of grade B cells. Matched cells will stay within a single digit millivolt difference (I have grade B and matched grade A to compare). Generally speaking, mine stay within 4 to 8 millivolts apart through 99.9% of the charge/discharge cycle for the grade A (depends on the C rate, and also the connections). Grade B cells are a good value.

Well, as long as my cells are in between the knees (roughly between 3.1 - 3.4v) the highest I've seen was a delta of 10mv. Most of the time less than 5. So the top balanced worked fine I would say.
Docan offered me a warranty extension and I took it. I'm pretty sure that the shipping costs for a replacement cell would be more less the same as the cost for a new cell. But I appreciate the gesture.
Anyhow, some new issue arose (like always):

I set the following parameters for solar cycling:

Bulk charge: 27.2
Float (the SCC manual calls it recovery charge but it behaves exactly as float): 26.8

Float is meant to serve loads when battery is full. This works nicely. When I pull bigger loads while in float the panels are mostly able to serve.

However, one charger (I have 2 because of different panels) never reaches bulk. It's having a south orientation and therefore sees sun roughly 2 hours after the east panels. Once it does, the battery voltage is already over 26.8v and the charger interprets that as fully charged and therefore drops to float while the other controller is still in bulk.
Anyone having a good idea about this situation?

 

[time2roll]

However, one charger (I have 2 because of different panels) never reaches bulk. It's having a south orientation and therefore sees sun roughly 2 hours after the east panels. Once it does, the battery voltage is already over 26.8v and the charger interprets that as fully charged and therefore drops to float while the other controller is still in bulk.
Anyone having a good idea about this situation?

Set the second controller slightly higher than the first. But honestly if battery capacity is not an issue I would not worry about it. If the usage is unusually large I assume the second controller would not see the higher voltage and would begin charging. Basically under normal or light load the second set of panels may not be needed. And unlike lead-acid there is no real concern to be at tip top 100% charged each day.

 

[jay_jay]

Set the second controller slightly higher than the first. But honestly if battery capacity is not an issue I would not worry about it. If the usage is unusually large I assume the second controller would not see the higher voltage and would begin charging. Basically under normal or light load the second set of panels may not be needed. And unlike lead-acid there is no real concern to be at tip top 100% charged each day.

So you mean I should leave the 2nd controller in float even though it won't charge while the voltage is higher than the set float voltage?
I mean it could be enough to keep the batteries full in summer. But what about winter?
Would it be acceptable to let the cells float at 3.4v? In that case the bulk voltage would need to go up a notch, maybe around 27.4v. That might be just enough to let the controller kick in boost charge before the battery has reached that level.

 

[time2roll]

Yes wait for winter and see how it goes then. The shift to more usage and less sun could prove interesting with the current set points. The answer will be more evident as the system is under more stress and may present a different solution. Or it might work fine. Enjoy the summer.

The float as programmed will still supply power as demanded for as long as the sun is up. So there is still some utility in keeping the battery full as the sun goes down.

 

[740GLE]

If the battery is “full” can’t really force more into it. Can you check how many KwHr the second SCC is producing
Also double check the voltage what the SCC thinks the cell voltages are vs what they actually are. Could adjust a few MV if need be.

 

[jay_jay]

If the battery is “full” can’t really force more into it. Can you check how many KwHr the second SCC is producing
Also double check the voltage what the SCC thinks the cell voltages are vs what they actually are. Could adjust a few MV if need be.

Always checking with a quality multimeter of course.
In the old lead acid times (just a few weeks ago ;-) the second SCC would yield 2.5 kWh on an average day. Since switching to lithium, I've only seen numbers close to that when the battery started on a low soc of course and when I set the float voltage to the absorb voltage in order to "force" the SCC into charging. I kept it like that until the current dropped to a few amps. Then I programmed the desired float again.
This worked beautifully, the batteries were fully charged and excess solar power was being used ro cover the loads. Full battery going into the night.
So now I'm thinking why not setting bulk and float to the same value, slightly above the resting voltage, for example 3.4v. That should charge the batteries to almost full while fully utilizing excess solar power right? Also, staying at that voltage for a couple of hours wouldn't hurt the cells would it?

 

[Ampster]

So now I'm thinking why not setting bulk and float to the same value, slightly above the resting voltage, for example 3.4v. That should charge the batteries to almost full while fully utilizing excess solar power right? Also, staying at that voltage for a couple of hours wouldn't hurt the cells would it?

I do something similar but my bulk setting is 3.45 per cell and float is 3.4. Most of the time after bulk my pack goes into about two hours of absorb and then sometimes settles to that float voltage before the sun goes down. My inverter has loads on it during the day and is passing through the GT solar coupled to it. The concept is to end the day with a pack topped up to about 90% as I use the batteries to cover all my loads during the evening peak.

 

[jay_jay]

I do something similar but my bulk setting is 3.45 per cell and float is 3.4. Most of the time after bulk my pack goes into about two hours of absorb and then sometimes settles to that float voltage before the sun goes down. My inverter has loads on it during the day and is passing through the GT solar coupled to it. The concept is to end the day with a pack topped up to about 90% as I use the batteries to cover all my loads during the evening peak.

Right, this seems to be exactly my usecase. I will try this approach.
Thanks!

 

[hackenstein]

Mine from Docan also swollen. 280ah

 

[Alkaline]

Message houseofancients, he should be able to help you with docan.

 

[Ampster]

Mine from Docan also swollen. 280ah

Some of mine were like that. They tested fine and have been in use for 15 months now with no problems. To me that is typical distortion of the thin walls of those cells. That is why the manufacturer recommends compression when in use.

 

[joeshmoe]

Same here. Just received mine, right out of the boxes. Haven't capacity tested or checked resistance. They all have a 3.25V SOC.
I'm hoping it's nothing to, but reading some of these threads has me concerned.

 

[Ampster]

I'm hoping it's nothing to, but reading some of these threads has me concerned.

It is nothing. Did you read my post above? Do not let perfect be the enemy of good. Do not pay attention to the comments of posters who have not used the cells before. Use the cells or test them to satisfy yourself.

 

[SparkyJJO]

I am no expert, but I don't see a problem with those at all.

 

[houseofancients]

Message houseofancients, he should be able to help you with docan.

how do you figure ?
not affiliated with them ..
he should message or email jenny wu

 

[Just John]

Same here. Just received mine, right out of the boxes. Haven't capacity tested or checked resistance. They all have a 3.25V SOC.
I'm hoping it's nothing to, but reading some of these threads has me concerned.

I'm not sure why people obsess about the voltage they receive cells. As long as it is above 2.5v and below 3.65v, it really tells you nothing about the quality of the cell.

My first 16 "grade B" cells were all within a single millivolt. Yet the 4 lowest capacity cells took less than 5 amp hours of charge to reach 3.65v. What that meant was that they sat around fully charged for more than a year and a half. By then, the voltage had settled to where it matched the other 12 cells that were at about 30% state of charge. Really the "matched" because they are at the same voltage BS that vendors tell people is a bunch of hogwash.