PINNED - Lithium battery conversion/info

[Burgerman]

As you charge or discharge theres a point around half charged where all the cells voltage changes. A step...

Its only at this step that you are seeing a problem. The step happens sooner or later on that group number 1. You wont see it unless you discharge further than say 50%.

Meaning it has a slightly lower capacity. That could be a cell, with a little less capacity or a bad connection on a connector, balance wire, or bolt. Usually a bolt...

Only on one of the 7 cells in group 1.

The only danger is that as you reach 40 to 45 miles that group no 1 may run out of power before the rest and go below 2 volts. Which causes damage. So your real question is does group 1 go out of power and voltage fall fast before the rest do? The reason that Shirley inc a cell monitor is so that you can see if that happens .

[Andrey]

Guys, how bad is it? Should I be worried? Should I reassemble the pack to find what is wrong?

(Headways, 84Ah pack)

Thanks.

[Burgerman]

Is this a first charge?

If so, now discharge it by say 50Ah and recharge.

[Andrey]

No, it's not first. I used it few months on Hyperion without PC monitoring (doesn't work), after that few weeks with PL8 (same graphs as above).
I'll try to discharge with PL8 and recharge again. Will post graphs later. Thanks.

P.s. what to do with "Bal.Entire charge" options? In preset "PO4 Normal Charge" it set as "Yes", is it ok?

[Burgerman]

Definitely not!
That will CAUSE your problem.
Dont use their presets.

Use mine.. Several reasons.

Set to 3.5V balance start or set to balance at CV only. Then charge fully, first, then discharge by 50Ah. Then recharge and post graph.

[expresso]

BM - i understand its the lowest cell group now - i left it off overnight - now monitor -

Cell 1 = 3.492V all the rest are 3.494V

i will discharge it again all day today - would be about double the discharge of yesterday - and recharge it again tonight -
the cell monitor shirley got me - at that time it was for the ADD ON - which is perfect by the way - i decided after to make the full pack - but now i should make a cable to try to use the monitor -

i recall at 40 mile ride - which i would call it my limit range to be safe - the Cells were 3.1 V - if Cell 1 stays the same at 2 lower than the rest - that shouldnt be a huge concern i believe right ?

what do you suggest i do at this point - if this dosnt fix its self this week ? would you known the correct size screw those are - length etc, - i like to just purchase new ones - its easier to replace with new ones rather than try to clean the glue off - takes more time ? thanks

monitor from this morning -

[Burgerman]

Glue, screws???

Test first, see if group 1 has less capacity.

[Andrey]

Definitely not!
That will CAUSE your problem.
Dont use their presets.

Use mine.. Several reasons.

Set to 3.5V balance start or set to balance at CV only. Then charge fully, first, then discharge by 50Ah. Then recharge and post graph.

Can you please share your entire preset?

[expresso]

Glue, screws???

Test first, see if group 1 has less capacity.

locktite is what i call glue - the bolts that come with the headway cells - ? i like to buy new ones - this way its easier to just replace add more locktite - - when i removed my bolts - i had to clean them a bit to remove the locktite that dried up on them -

i was more careful this time to add less on the bottom end of the bolt rather than up higher - if you can give me the correct size bolt - length - i would get a bunch and replace them if it comes to that - i am discharging it now all day and will check it tonight and then recharge it - monitor it again etc, -

[Burgerman]

Are these on group 1? If not what do they have to do with anything?

You need only check if 14 bolts on group 1 are tight.

[Burgerman]

For 84Ah 8S LiFePO4

This is set to suit your pack.

It is 20A charge, 3.5v balance start, 500th termination, no +8mv at CV, wide cell balance limits, and voltage and time limits, etc and a bunch of other hidden settings changed to suit. Remove.zip

Charge, discharge 40 to 50Ah , then recharge and lets see the curves.

[Andrey]

For 84Ah 8S LiFePO4

This is set to suit your pack.

It is 20A charge, 3.5v balance start, 500th termination, no +8mv at CV, wide cell balance limits, and voltage and time limits, etc and a bunch of other hidden settings changed to suit. Remove.zip

Charge, discharge 40 to 50Ah , then recharge and lets see the curves.

Thank you!

[expresso]

Are these on group 1? If not what do they have to do with anything?

You need only check if 14 bolts on group 1 are tight.

what i did was just check the top row since that was the only thing i removed last to add the breaker etc, - but now that i think about it - i did have to remove some under the top row to add the wires

I dont know what Cells are Group 1 - i dont know which 14 bolts to check for Cell Group 1 -

[Andrey]

For 84Ah 8S LiFePO4

This is set to suit your pack.

It is 20A charge, 3.5v balance start, 500th termination, no +8mv at CV, wide cell balance limits, and voltage and time limits, etc and a bunch of other hidden settings changed to suit. Remove.zip

Charge, discharge 40 to 50Ah , then recharge and lets see the curves.

Found that this preset also has Bal.Entire Charge - "Yes", right?

[expresso]

Bm would this be the correct size ? M6 x 8mm - is the rest of the details correct ? if i have to redo this - i rather replace the bolts and clean the old ones at a later time for a spare -

https://smile.amazon.com/Button-Socket- ... l_huc_item

[Burgerman]

yES is OK as long as you set 3.50v or higher. Default is 3.30 and too low. No is CV only. Also OK.

[Burgerman]

https://www.amazon.com/gp/product/B01H6 ... pldnSite=1

YES...

[expresso]

https://www.amazon.com/gp/product/B01H6QFSUC?ref%5F=cm%5Fwl%5Fhuc%5Fitem&pldnSite=1

YES...

i just read somewhere - that someone got M6 x 6mm size - are the same ones we use 8mm long ? before i order 150 of them - which i cant return

[Andrey]

Charge, discharge 40 to 50Ah , then recharge and lets see the curves.

Discharge naturally (it will take me about a week, with my current pattern of use) or with PL8 (it discharges with -3.65A as I can see)?

[Burgerman]

Make sure discharge balance is OFF!

As it is on my profile.

[Andrey]

Make sure discharge balance is OFF!

As it is on my profile.

I checked - it's off. But discharge rate still is -3.65A.

[Andrey]

The internal discharge is limited to 10A or 100W, whichever occurs first.

Mystery solved

[Burgerman]

There are ways to discharge at 30 to 40 amps. But its complicated...

Your pack is 2100 watts.
100w discharge to 50 percent will take 10.5 hours.

[Gnomatic]

There are ways to discharge at 30 to 40 amps.

With something like this(25A) or this(40A). They come in 50A and 60A versions too, but I assume its not the best idea to pull current out of the pack too fast.

When discharging with something like the above, does the PL8 even need to be in the loop? Say you're discharging a 24v 100Ah pack with a 25A load dump. Is it ok just to connect the pack straight to the load dump, and disconnect it after say 3hrs if you planned on draining the pack to 25% power remaining?

[Burgerman]

http://www.ebay.co.uk/itm/12V-24V-1000W ... SwA4dWK4qn

I use this.

You only pull current out as fast as you set it to do so. And as long as volts dont go higher than the regen 24v batt charging volts set in supply tab. They get very hot!!!

It doesent need to be, but it measures, graphs.

[Gnomatic]

If using the PL8 with a load dump to discharge a pack, where in the loop does the PL8 fit in? Is the PL8 being powered by the the battery pack and then "charging" or sending current into the load dump?

And from what you are saying, I could use the PL8 to discharge the pack at say 20A, even if the dump load could handle 40A. Do I have that correct?

[Burgerman]

PL8 is powered by the power supply.
The load dump is ALSO powered by the power supply. Its connected in parallel.

When you turn on the power supply the load gets hot...
I set my power supply to 25V. I set my PL8 to use a 24V Optima battery as a power supply, and enable regenerative discharge. I set it to a max 15.6V and a max of 35A into the "battery".

In the regen discharge setting for the lithium pack I choose max. Or something higher than I expect the charger will be limited to on the regen Amp setting.

Then choose discharge, regen, and go! As the Amps ramp up, the regenerative power pushes the dump voltage above the power supply voltage and so the power supply now contributes zero Amps. And there is a 35A 30 volt regen current. If you choose low amps, the power supply will still contribute. And waste power. You have to feed more amps in than the power supply is doing before you press go. So if you only want to discharge at 20A then set power supply to 12V. And then it will be only pulling about 15 amps. Then the 20A regen will be enough. You need to understand whats going on its too hard to explain.

[expresso]

what can i do to check each cell in Group 1 to see if theres a bad cell or not ?

can i leave them in the orange blocks - just remove all bolts connector plates etc, - then what can i do ?

i been discharging for over 9 hours now - i notice Cell 1 is going lower from the rest starting at about 30ah removed and the gap is wider now - from the rest
also i notice the discharge current it slower now than before which was at 3.6amp i think and now 1.6amp

i think i am just going it remove the top row tomorrow and start checking each bolt - clean , replace - - not sure what else i can do - ?

[Gnomatic]

PL8 is powered by the power supply.
The load dump is ALSO powered by the power supply. Its connected in parallel.

When you turn on the power supply the load gets hot...
I set my power supply to 25V. I set my PL8 to use a 24V Optima battery as a power supply, and enable regenerative discharge. I set it to a max 15.6V and a max of 35A into the "battery".

In the regen discharge setting for the lithium pack I choose max. Or something higher than I expect the charger will be limited to on the regen Amp setting.

Then choose discharge, regen, and go! As the Amps ramp up, the regenerative power pushes the dump voltage above the power supply voltage and so the power supply now contributes zero Amps. And there is a 35A 30 volt regen current. If you choose low amps, the power supply will still contribute. And waste power. You have to feed more amps in than the power supply is doing before you press go. So if you only want to discharge at 20A then set power supply to 12V. And then it will be only pulling about 15 amps. Then the 20A regen will be enough. You need to understand whats going on its too hard to explain.

That's a pretty interesting setup. Pretty sure I followed most of that LOL. Like you said, a bit complicated.

I think I'll go with a 25A dump load, and just stick one of these power meters in between the pack and the load dump to monitor how much has been discharged etc. You've mentioned using them for various things before. I can still use the PL8 to monitor individual cell voltages as the pack discharges.

[Burgerman]

Slower because that cell has reached the voltage that the discharge was set to. Lower it to 2.9V and restart the discharge, and see what it does.

How to find a bad cell from 7?

Remove the connecting plates from those 7. At just one end.
Then connect the charger to each cell in turn, charge, then discharge, and see what its capacity is. If one is bad you will see it easily. Strange if it is, as I have 3 full packs, some years old now, all fine.

DISCONNECT ALL BALANCE CABLES BEFORE DOING ANY OF THIS FROM THE CHARGER..