OK to mix battery packs?

[OffGridIdaho]

I currently have an EVE 280ah 24v pack that is 1yr 217days old. I have run it between 90-20soc. I charge at 30a. The cell delta is great.

Can I now add 8 more EVE 280ah cells to bring my pack to 48v? I just ordered the extra solar panels and new Vic 48v inverter. Is it OK to mix old and new?

 

[sunshine_eggo]

Your 48V battery will be limited by the capacity of the 217 day old 24V battery capacity (unless the new cells are weaker than the old), and the 217 day older cells will likely fail earlier than the new cells.

If you're fine with this, it's fine.

How do you run it between 90 and 20% SoC?

 

[robby]

Yep you can add them but you will lose some the lifespan on the newer batteries. If you need 48V just do it, there is nothing else you can do to get around it.

 

[sunshine_eggo]

I'd still like to know how you run between 20 and 90% SoC.

 

[Steve_S]

I currently have an EVE 280ah 24v pack that is 1yr 217days old. I have run it between 90-20soc. I charge at 30a. The cell delta is great.

Can I now add 8 more EVE 280ah cells to bring my pack to 48v? I just ordered the extra solar panels and new Vic 48v inverter. Is it OK to mix old and new?

1) IF they have NOT been abused (over / under charged & frozen etc) the odds of any "real" capacity loss is minimal, especially if as you say, they stayed between 10-90%. you are good to go BUT do try to use identical cells, IE EVE 280K or 280N etc. There is not a big diff between N or K and you can put them together in a pack (I have and never had issues). BUT posts are in different locations so busbar fun is in play.
!! Don't mix V3 cells & V2 in a pack, the IR's will cause havoc ! BTDT !!
2) FLA-ism need not apply... Again if never abused they will be fine. LFP does not suffer like FLA and is a very different animal.

I strongly suggest you download & install the LiFePo4 Cell Scanner on your phone and scan your existing cells, get the version number and try to match them. K Series cells are quite common but N series are getting hard to locate BUT they are still out there and cheaper because they are New Old Stock. Amy @ Luyuan can source them with a wee bit of time. Note she sources from EVE warehouse stocks and not brokers. Others may be able to supply Brokered cells (consider them B or Bulk at best).

ADVICE - Pre-Assembly. You will have 8 "active" cells & 8 that have sat in storage for who knows... You WILL HAVE TO top charge the new cells and fully activate them by taking them to 3.650V and down to taking 2.5A. Then batch all 16 together & fully TOP the lot to get them on par.... Allow the 16 to sit in Parallel at least 24 hours after charge is done, then assemble. It would be prudent to use a Cell Tester and check each cell @ a "specific voltage like 3.300 exactly) and note the IR of each cell (current & new) and match them.

You never stated WHAT Grade of cells you currently have.
IF proper A-Grade, then get A-Grade cells to go with it.
IF B or Bulk then putting A Cells will be OK, but other B/Bulk if not close in IR matching could be problematic.

 

[OffGridIdaho]

1) IF they have NOT been abused (over / under charged & frozen etc) the odds of any "real" capacity loss is minimal, especially if as you say, they stayed between 10-90%. you are good to go BUT do try to use identical cells, IE EVE 280K or 280N etc. There is not a big diff between N or K and you can put them together in a pack (I have and never had issues). BUT posts are in different locations so busbar fun is in play.
!! Don't mix V3 cells & V2 in a pack, the IR's will cause havoc ! BTDT !!
2) FLA-ism need not apply... Again if never abused they will be fine. LFP does not suffer like FLA and is a very different animal.

I strongly suggest you download & install the LiFePo4 Cell Scanner on your phone and scan your existing cells, get the version number and try to match them. K Series cells are quite common but N series are getting hard to locate BUT they are still out there and cheaper because they are New Old Stock. Amy @ Luyuan can source them with a wee bit of time. Note she sources from EVE warehouse stocks and not brokers. Others may be able to supply Brokered cells (consider them B or Bulk at best).

ADVICE - Pre-Assembly. You will have 8 "active" cells & 8 that have sat in storage for who knows... You WILL HAVE TO top charge the new cells and fully activate them by taking them to 3.650V and down to taking 2.5A. Then batch all 16 together & fully TOP the lot to get them on par.... Allow the 16 to sit in Parallel at least 24 hours after charge is done, then assemble. It would be prudent to use a Cell Tester and check each cell @ a "specific voltage like 3.300 exactly) and note the IR of each cell (current & new) and match them.

You never stated WHAT Grade of cells you currently have.
IF proper A-Grade, then get A-Grade cells to go with it.
IF B or Bulk then putting A Cells will be OK, but other B/Bulk if not close in IR matching could be problematic.

Translated to Engrish? I have no idea what half that means?
I bought the EVE 280 grade A ah cells 1.7yrs ago from 18650 battery. The new cells I just bought today say "new improved" get 8,000 cycles and test higher then 300ah. So I guess that means a different version? Are they not going to work with my 1.7yr/old batteries? As far as top balancing I dont have any way to do that. Do I need to buy something? Am I going to have to shut everything off for days and weeks? I have 2 chest freezers full of meat its not like I can turn everything off. CRAP this is not going to end well I can see that.......

OK I just called, txt'd and emailed 18650 to put a hold on shipping the batteries. Sounds like I need 16 of the V3's according to you. So what do I do with the 8 older batteries? Dang its not like I have extra cash for this can of worms either. Crud!

 

[Steve_S]

They should be fine. The older cells may have a bit less deliverable AH than the new ones but that won;t make a big difference really. If you can't top balance / charge the cells, then what you can do (its a hack) is to let the current pack discharge to a point where the voltage of the cells is at or just above the new cells. I'm saying if the new ones are at 3.200 then the od on should not be over 3.275 but not more than 3.300. Once in series with a Good BMS preferable a JK with Active balancing then charge up the pack to full and let the active balancer work on it.

 

[rustyrotors]

Don't mix V3 cells & V2 in a pack, the IR's will cause havoc ! BTDT !!

why what happened? im about to mix 2yo eve 304 and new 280v3 for a 48v pack. what horrors await me

i can see the 304s higher IR will make them surge more during charge, was hoping not enough to make a difference. i can see it making cell balancer not work very well, but i already have that problem on the 304s, i only manually balance the cells now

 

[Steve_S]

I discovered much to my chagrin that;
A) the cell terminals can be in different locations on the cell pending on version. That's a PITA !
B) the IR's are CRITICAL - Murphy's Laws tempted and Tickling Runner Cell behaviours. Higher IR = slower to take charge.

I learned painfully about the IR difference quite a ways back when mixing cells (hence why I have 4 spare now, gonna become a 12V/280). This was before I got my YR1035 meter (partly precipitated why I got one). First attempt I put the cells in BUT #1 with lower IR instantly caused troubles as it would RUN up after 3.35 quickly and hit OVP handicapping the pack. So I moved things around and 4 cells (new ones) were slower to take charge then the older ones... After a lot of "Blue Air" & YR1035 I realized the issue and got 4 more cells and got it sorted.

Now if you mix 280's & 304's the 280's being lowest common denominator will RULE the pack. That means REALLY KNOWING what voltage to set for Undervolt Disconnect because the 304 Cells will have more juice in them at the bottom end than the 280's which could dip below the Volts per Cell that you want. The BMS will take care of that mostly but Inverter ETC have to be "just right".

 

[OffGridIdaho]

I discovered much to my chagrin that;
A) the cell terminals can be in different locations on the cell pending on version. That's a PITA !
B) the IR's are CRITICAL - Murphy's Laws tempted and Tickling Runner Cell behaviours. Higher IR = slower to take charge.

I learned painfully about the IR difference quite a ways back when mixing cells (hence why I have 4 spare now, gonna become a 12V/280). This was before I got my YR1035 meter (partly precipitated why I got one). First attempt I put the cells in BUT #1 with lower IR instantly caused troubles as it would RUN up after 3.35 quickly and hit OVP handicapping the pack. So I moved things around and 4 cells (new ones) were slower to take charge then the older ones... After a lot of "Blue Air" & YR1035 I realized the issue and got 4 more cells and got it sorted.

Now if you mix 280's & 304's the 280's being lowest common denominator will RULE the pack. That means REALLY KNOWING what voltage to set for Undervolt Disconnect because the 304 Cells will have more juice in them at the bottom end than the 280's which could dip below the Volts per Cell that you want. The BMS will take care of that mostly but Inverter ETC have to be "just right".

Can you link or recommend a top balancer and IR tester? I went ahead and kept the order for the 8 additional batteries. If they dont mix well Ill get 8 more.

 

[Steve_S]

I use a Yorea YR1035+ Battery Cell tester. These are rebranded by many.

Luyuan High Accuracy Fast Test Yr1035+ Lithium Lifepo4 Lfp Battery/cell Internal Resistance&voltage Tester - Buy Yr1035,Lifepo4,Ir Tester Product on Alibaba.com

Luyuan High Accuracy Fast Test Yr1035+ Lithium Lifepo4 Lfp Battery/cell Internal Resistance&voltage Tester - Buy Yr1035,Lifepo4,Ir Tester Product on Alibaba.com

www.alibaba.com

I use a TekPower TP1545 Bench Power Supply, it sells for around $240 USD and not easy to get. I bought this long ago before other similar priced goodies appeared. TODAY I suggest the EBC40L Bench power supply, similar price and capable of charging at 40A.

https://www.amazon.com/T-king-EBC-A40L-Current-Dischage-Capacity/dp/B08KS1NSMP/ref=sr_1_15?

!!! SHOP THIS AROUND, I just picked one listing from ZON.
IF Buying stuff from Amy Wan @ Luyuan like the cases, cells, she could also source the EBC40, would likely be cheaper & if bundled in with the rest of a shipment that can save bucks.

 

[DIYrich]

Make sure you use a 16 cell bms, and not two 8 cell bms.

 

[OffGridIdaho]

Make sure you use a 16 cell bms, and not two 8 cell bms.

Rodger that.....
I think my JK does 20 or 24 cells.

 

[Dynoman]

Can you link or recommend a top balancer and IR tester? I went ahead and kept the order for the 8 additional batteries. If they dont mix well Ill get 8 more.

Like the devices previously listed. Here are some other options.

Picked up one of the YR1035+ IR testers not long ago from this source on ebay.

YR1035+ 0-100V 0-200Ω Lithium Battery Internal Resistance Tester Voltmeter USA | eBay

It is suitable for battery grouping, battery performance testing and battery screening. It has a compact structure and is easy to carry, making it an ideal test machine for electricians and electronics.

www.ebay.com

Used this power supply with attached top balanced tutorial.

Variable Lab Bench DC Regulated Power Supply Adjustable 30V 20A with LED Display | eBay

0-30v 0-20a Dc Power Supply Adjustable Variable Regulated Power Supply New Specifications: Input Voltage: 110v 60hz (Customizable) Output Voltage: Dc 0-32v Continuously Adjustable Output Current: Dc 0-20a Continuously Adjustable Display Resolution: Voltage 0.1v, Current 0.1a. (Customized 0.01v...

www.ebay.com