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Have a question - EV vs ESS batteries

GFruge

New Member
Joined
Apr 25, 2021
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108
I’m getting ready to make a purchase from Docan. They have 15kw / 300ah batteries available with EVE ESS batteries. But there’s an upgrade available for an additional fee to get EVE EV grade A batteries.

What are the differences? EV lasts longer? Should I spend the money to upgrade? I’m planning on buying 2 batteries to get 30kw worth of storage.
 
I read through the posts and I see people more excited about EV batteries over the ESS batteries. I did confirm with Docan that the ESS batteries they use are grade B, but new.

The internet search results show the ESS batteries having longer lifespan and life cycles than the EV batteries.

I ask these questions because I currently have 2 125ah batteries that have failed after only 3.5 years. Granted, they were discharged 80% daily for those 3.5 years.
 
What’s the price difference?

Many are saying Calendar aging is more of a factor than cycling.
You could have a bigger bank of batteries with the ESS for the same price. And that would put less strain or potentially lower C-rate charging/discharging and cycling on the batteries.
 
Failed how?
That is only 1000 cycles, expect 3000 or 6000 according to some claims.
 
The price difference is $500 for upgrading from grade B ESS to grade A EV. Should I ask about grade A ESS?
 
Failed how?
That is only 1000 cycles, expect 3000 or 6000 according to some claims.

I have no idea. One day, the batteries would only charge to 87%. A week later, would only charge to 80%. A month after, would only charge to 51%. And now, the batteries refuse to charge.

Not sure what’s going on, but I needed more capacity anyways. Once swapped out, I’ll replace the cells in these batteries as I really don’t know what I have. All I know is 125ah batteries that were supposed to be good for 3,000 cycles
 
The price difference is $500 for upgrading from grade B ESS to grade A EV. Should I ask about grade A ESS?
You are assembling the battery pack? Does your system need to be “Listed/Certified”?
 
No, purchasing already assembled pack. Don’t have the experience assembling myself. Does not need any certifications. I live in Central America.

When I rebuild my current packs, I’m sure I’ll ask many questions or just try to replace everything as I see it
 
I have no idea. One day, the batteries would only charge to 87%. A week later, would only charge to 80%. A month after, would only charge to 51%. And now, the batteries refuse to charge.

Not sure what’s going on, but I needed more capacity anyways. Once swapped out, I’ll replace the cells in these batteries as I really don’t know what I have. All I know is 125ah batteries that were supposed to be good for 3,000 cycles

I wonder if it is cell imbalance, and charge voltage was never high enough to trigger balancing.
Do you have access to BMS information, which would list individual cell voltages and limits?
What voltage did your system charge to?

125Ah batteries are small enough that it is more cost-effective to replace with large, new, cheaper ones than to replace a BMS.
However, understanding the failure and possibly making changes to avoid it is worthwhile.

If no BMS access, you could remove cover and measure individual cell voltages. Report back for further assistance.

Do look up charge parameters in your equipment. And tell us which inverter, SCC, or whatever you use.
 
I asked the installer about the BMS info. Seems like there’s no access to it. I may have to end up opening and testing each individual cell to see what’s going on. For right now, I’m more interested in this new purchase to make sure I’m getting what I need and the best investment for long term.

I have a Growatt 6k off grid inverter, model SPF-6000T-DVM. System was at 58 volts. Not sure if the batteries even have anything to balance the cells. Not sure, just some cheap batteries I’m sure.

I asked the installer why I would only get 30amps worth of charging max. He gave me some run around. I finally found in the inverter settings that it was set at 30amps. I recently changed that to the max of 60amps after the issues began.

I’m here working in the US and trying to get this order in since it takes like 2 months to get anything from China. When I return to Central America, I can remove the covers and check them. However, if there is a balancing issue, what’s the remedy? Do I need particular instrument or hardware? I’d like to have what I need in hand or can get access to in case that’s the issue.

Last time I was there, 2 weeks ago, one battery was flashing at 3/5 on the SOC. The other battery was flashing full at 5/5 on the SOC. Something is out of wack between the 2.

Anything suggested will get tried. If I need something to balance the cells or a new BMS, I’ll give it a shot.

Only other thing I can mention is that I have this connected to 10x 530 watt panels
 
BMS ought to provide balancing if pack held at sufficiently high voltage for a while, apparently did not.
58V / 16s = 3.625V/cell which should be good to trigger balancing.
Some might say a lower voltage would be preferred for cell longevity. But if it only reaches that voltage for a short while, doesn't sit there long, I don't think it gets to or past 100% SoC so not a problem.

You can charge low cells individually with a CV/CC supply set for about 3.6V; see top balancing topic on the forum.
You can discharge high cells with a resistive load. But need to monitor, stop before over-discharging. Would be nice to have an automatic circuit.
If cells can be separated so no longer in series, you could connect a high voltage one through a resistor to parallel with a low-voltage one. That would partially bring them into balance.

Not accepting a charge I'm guessing means BMS disconnects for some cells being over-voltage while others are low.
 
I asked the installer about the BMS info. Seems like there’s no access to it. I may have to end up opening and testing each individual cell to see what’s going on. For right now, I’m more interested in this new purchase to make sure I’m getting what I need and the best investment for long term.

I have a Growatt 6k off grid inverter, model SPF-6000T-DVM. System was at 58 volts. Not sure if the batteries even have anything to balance the cells. Not sure, just some cheap batteries I’m sure.

I asked the installer why I would only get 30amps worth of charging max. He gave me some run around. I finally found in the inverter settings that it was set at 30amps. I recently changed that to the max of 60amps after the issues began.

I’m here working in the US and trying to get this order in since it takes like 2 months to get anything from China. When I return to Central America, I can remove the covers and check them. However, if there is a balancing issue, what’s the remedy? Do I need particular instrument or hardware? I’d like to have what I need in hand or can get access to in case that’s the issue.

Last time I was there, 2 weeks ago, one battery was flashing at 3/5 on the SOC. The other battery was flashing full at 5/5 on the SOC. Something is out of wack between the 2.

Anything suggested will get tried. If I need something to balance the cells or a new BMS, I’ll give it a shot.

Only other thing I can mention is that I have this connected to 10x 530 watt panels
Before you buy more batteries, it’d be best to understand what wrong with the current one.

Otherwise you might end up in the exact same situation (a battery that can’t be properly maintained/charged) and the only issue is the meat popsicle between the inverter charge controller and the BMS.

Yet another reason cell level voltage indication is a must on any purchase.
 
I’ll definitely figure out the issue with my current batteries. But, I’ll buy new batteries anyways for the capacity and user friendly features like being able to monitor the cells with BMS and definitely have an active balancer installed.

So, going back to my original thoughts, what’s the best longevity battery? EV grade A, grade B ESS, or another option that just came across, Hithium?
 
ESS and grade B are all cells that failed to be EV cells in some what. Possibly internal resistance. Calling them ESS or grade B is the manufacturer recouping cost for cells that fail to meet specs.

They'll probably work fine for you, as they have for many others.
 
Yes. get the Grade A cells. Grade B cells can be a good deal or crap out on you sooner. And they sometimes can have issue with staying balanced if they are too far out of spec, which will cause the problem you have now with your existing batts.

On your "failed" batteries, you can cause the cells to balance if you carefully charge them up to a voltage the BMS will allow, and hold it at that voltage over night. Then bump up the voltage by a 0.01-0.05v increment and charge again that day and over night. Rinse and repeat until they are taking a full charge to the voltage you expect. If you push a cell voltage too high, the BMS should cut you off. If that happens, step down by 0.01 or so volts and go again, once the BMS allows charging again. Sometimes you have to discharge for a few minutes to reset the charge FETs so you can charge again.

I recently had to go through this on my new battery. It took about 125 hrs of holding charge voltage to balance the cells to a point where I can charge to a nice high voltage without tripping any alarms.

A lot of people say not to charge to a high voltage, but it is required in order to keep the cells balanced. You should charge to as close to 3.6v/cell as you can get once every couple months or so, and hold it there for 5-10 hours to balance the cells.
 
Would it be wise to swap to a different BMS and balancer while this thing is open to do top balancing? One that I can monitor the health of the cells without having to open constantly to check each individual cell.

If so, which one would you recommend?
 
The only ones I have any experience with are JK BMS.
I'm using B2A8S30P for 12V, PB2A16S20P for 48V. Working so far, haven't done much with them. Others have some months/years on the 48V model.
 
If Docan is saying their ESS batteries are "Grade B" then don't buy those.

You want something that is at least being called "Grade A" even though that still probably won't be truly EV spec. It's doubtful that anybody is selling actually EV passing cells on the secondary market.
 
Thanks for the advice on the BMS and cell grade. I have 1 estimate with Docan at the moment and waiting on one more quote from a company named Avepower. Both claim A grade cells.
 
I did confirm with Docan that the ESS batteries they use are grade B, but new.

ESS does not mean grade B. Grade B means failed rejected cell that can nto be sold so it has to be auctioned off to wholesalers. Docan is one of these whole buyers.

EV and ESS are 2 separate classes of cells, cells are made for each type of purpose, generally EV cells have more armor plating for crush rating while ESS do not not. Also EV cells will have less cycle life but higher output power vs ESS cells.

The only EV rated cells I am familiar with are EVE 105 and EVE 304 (UL 2580) the rest are all ESS rated (UL 1973)

A grade B EV cell does not make it a Grade A ESS, it makes a failed CELL. PERIOD.

Docan just refuses to admit these are grade B and has been caught multiple times selling cells with counterfit qr codes that have been sanded off. I would assume anything you buy from them is grade B.
 
Any suggestion to protect myself from bad cells?

I actually just sent payment for (2) 15kw batteries with EV cells.

Every other vendor I checked with only offered Hithium cells
 

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