Parallel LiFePO4 12V 90Ah pack with 12V 280Ah pack, any issue?

[JoeHam]

So if you truly stay between the knees, running from about 3.1 to 3.5 volts there should be no issues correct?

I would like to parallel my 60ah DIY Fortune with my 100ah GYLL.

I can set my Schneider CSW 4048 to step in and charge if the batteries drop below 49.6 v so no need for LVD unless the grid is down for days. At that point I could add a generator to the setup.

Charge and discharge are usually around 0.2C.

 

[flemmingdjensen]

So if you truly stay between the knees, running from about 3.1 to 3.5 volts there should be no issues correct?

I would like to parallel my 60ah DIY Fortune with my 100ah GYLL.

I can set my Schneider CSW 4048 to step in and charge if the batteries drop below 49.6 v so no need for LVD unless the grid is down for days. At that point I could add a generator to the setup.

Charge and discharge are usually around 0.2C.

In parallel they share the same voltage! So no problem in using the full specified range of the cells 3.65V to 2.5V

 

[Steve_S]

3.00-3.400 is the main curve and all cells will do it if they are healthy and happy. Runners & lazies will act up outside of the main curve 99% of the time. Hi/Lo temps will have an impact. A DIY pack can rarely stay "tight" with little deviation outside of the main curve is RARE. Bulk Commodity cells DO NOT ! Only fully Matched, Batched & Binned cells will stay close together. THAT is an expensive proposition because it is labour intensive & time consuming (see labour), it can easily drop 50% of cost on top per cells. That is usually only done for large commercial orders, like when BattleBorn orders their cells in massive batches, they are only Matched, Batched & Biunned cells which they same out to verify.

Try to find ANYONE here that takes the DIY packs with Bulk Cells from 2.50 to 3.65 with all the cells remaining within <=30mv. Good Luck.

 

[flemmingdjensen]

3.00-3.400 is the main curve and all cells will do it if they are healthy and happy. Runners & lazies will act up outside of the main curve 99% of the time. Hi/Lo temps will have an impact. A DIY pack can rarely stay "tight" with little deviation outside of the main curve is RARE. Bulk Commodity cells DO NOT ! Only fully Matched, Batched & Binned cells will stay close together. THAT is an expensive proposition because it is labour intensive & time consuming (see labour), it can easily drop 50% of cost on top per cells. That is usually only done for large commercial orders, like when BattleBorn orders their cells in massive batches, they are only Matched, Batched & Biunned cells which they same out to verify.

Try to find ANYONE here that takes the DIY packs with Bulk Cells from 2.50 to 3.65 with all the cells remaining within <=30mv. Good Luck.

The BMS will cut off when the first cell reaches 2.5V and the same goes for charging - the BMS will cut off when the first cell goes above 3.65V.

I have been using my 300AH bank (3 x 100AH in parallel) like this for years - so within specs. And never had BMS cutoffs...

Probably never discharged to more than 50% because it wasn't necessary. So I have NEVER had a cell above 3.65V and NEVER below 2.5V so what's the problem

If you buy cells from Basen Technology and order Prismatic Grade A New Matched cells you will not have huge problems with in-ballance

 

[Steve_S]

Any cell hit's 2.50 it's LVD even if other cells are at 2.75 or even 3.00.
Any cell hit's 3.65 it's HVD even if other cells are at 3.45 or 3.50.
Without a Smart BMS or active cell monitor people do not see this and make assumptions.

This is a Diversion and Off-Topic for this thread.

 

[JoeHam]

In parallel they share the same voltage! So no problem in using the full specified range of the cells 3.65V to 2.5V

Not how I run my cells, thanks anyway. Your cells, your choice.

I think I will parallel them and run between 3 and 3.5.

 

[flemmingdjensen]

Not how I run my cells, thanks anyway. Your cells, your choice.

I think I will parallel them and run between 3 and 3.5.

Sounds good - you will get around 90% og the capacity using these parameters which is fine indeed.

In my setup I will very seldom go below 3V also - I will probably turn on my diesel engine and charge if there is no sun for the solarpanels

The only thing I am trying to say is that people seems to be getting super paranoid about getting close the the parameters where you still are within specs.

 

[Bud Martin]

So I charge my battery bank (12V 90Ah batterey and 12V 280Ah battery in parallel) to full charge (stop charging at 14.1V using 50A AC charger of my MPPT).
The inverter is RelaiblePower 1500W. The loads (about 400W) are laptop, 32" LCD TV (CCFL backlights), two 9W LED lamps, two air cleaners. The loads are connected to Kill-A-Watt which is connected to the output of the inverter.
I set the low Voltage shutdown of the inverter to 11VDC using external Voltage sensor module that drive the relay, the contacts (C and N.O.) of the relays are connected to the power switch of the inverter. When 11V is reached the relay contacts goes open circuit and shutdiwn the inverter.
The result is, the Kill-A-Watt shows 4100WHr just before shutdown, that means the power input to the inverter is higher than 4100Whr, I estimate it to be about 4700Whr.
I am happy with the results, but will keep my eyes on it in the long run until I have money to build another 12V 280A bacttery pack.

 

[Steve_S]

4 cells X 3.2V = 12.8V. kWh is always calculated at a nominal voltage of 3.200 for LFP.
12.8V X 280AH = 3,584kWh
12.8V X 90AH = 1,152kWh
total gross capacity: 4,736kWh.

 

[Mike Jordan]

4 cells X 3.2V = 12.8V. kWh is always calculated at a nominal voltage of 3.200 for LFP.
12.8V X 280AH = 3,584kWh
12.8V X 90AH = 1,152kWh
total gross capacity: 4,736kWh.

This miss-matched capacity bank, intrigues me.
Have you ever done an gross capacity test, on the connected bank of miss-matched capacities?

 

[jpimlott]

I do a similar thing for a low volt disconnect. I use the load control relay in an epever charge controller to hold a relay to lvd. I user the same relays other contact to direct control 24 volts loads.
I have a large load that runs 24/7 (server ,NAS storage, and boinc computing drawing about 400 watts. I just finished setting up about 1800 watts of solar panels. Instead of the batteries going full and charge controller going to float ,I am going to setup a high voltage (27ish) to transfer load from the server on the inverter using an automatic transfer switch and a cool voltage detect to drive a relay.


Always fun playing with toys to make it better.

 

[Bud Martin]

4 cells X 3.2V = 12.8V. kWh is always calculated at a nominal voltage of 3.200 for LFP.
12.8V X 280AH = 3,584kWh
12.8V X 90AH = 1,152kWh
total gross capacity: 4,736kWh.

I wonder why Battleborn does not use 12.8V as norminal, Battelborn rates its batteries at 100Ah 1200WHr, not 1280WHr. I never learn which one to use, 12V or 12.8V rating when looking at the spec of pre made battery.

 

[Dijo]

But I would LOVE for someone to run a separate charge/discharge capacity test on their small/large batts. Then parallel connect, and run the charge/discharge capacity test again.

Anyone did some serious test like this , with some good capacity test.. ? should we require a Will prowse's video ?

Anyone with 2 different intensity pack who spoke in this threads had some troubles with it since 30th of January ?

 

[Bud Martin]

Follow-up on the 90Ah 12V pack in parallel with 280Ah 12V pack.
So I remove the 90Ah pack (in parallel with 280Ah pack) from the setup that I have been using since Jan 2021, run it 24/7 on my Solar system, and now replace it with 230Ah pack that I just built about a week ago using EVE 230Ah cells from DOCAN Power.
The 90h cells ('B' grade cell, not likely to be 'A' for sure) were bought from Aliexpress which at that time I really do not know much about the building DIY battery pack, the capacity tested out a little over 90Ah.
So yesterday I charge the 90Ah pack back up to 13.6V and wait till current went down to <1A and let it sit for about an hour, then I hook up my 1200VA/1000W Victron inverter to run my gas furnace last night, I ran it down till the cells show about 2.5V then I shutdown the system. The result shows about 87Ah, and there is no sign of cell bulging at all since the day I got the cells.