PINNED - Lithium battery conversion/info

[FJC10]

Hi to all!

I left my lithium conversión because my bad health. Now I want to try again, but my test little pack of 8S is totally dead? All cells are below 0.200V!!! Can I resurrected it?



I try charge cell by cell 1S but as you can see "SAFETY CODE 19: No Pack"

Can I do something?

[Burgerman]

You may either have a setting wrong, or you have a voltage too low, or a bad connection to the cell.

Send me the preset here so I can look.

Unless the cells are REALLY below 2 volts? In which case they are no use. Use a volt meter. The reading on the charger may not be correct if theres another problem. You can normally leave them a year or so and not see that! How long where you ill?

I check many lipo, lifepo4, lithium ion packs every 3 months, and they seem to lose almost nothing. Did you leave them connected to a chair?

[FJC10]

Low voltage. VERY low voltage All are only 140mV to 300mV.

[FJC10]

You can normally leave them a year or so and not see that! How long where you ill?

I check many lipo, lifepo4, lithium ion packs every 3 months, and they seem to lose almost nothing. Did you leave them connected to a chair?

Approximately 9 months connected to my chair!!!! Pack 8S! Yes, I'm stupid, but my bad health made me forget the project.

All the other 72 cells are charged but not connected for 9 months too...

[Burgerman]

Any that were not connected to a chair will likely be fine. Measure them. 2.5V or higher, no worries.

A chair that is turned off, stupidly still DRAINS batteries... Its the reason almost all unused chairs have wrecked batteries, and why you need to keep lead chairs on a float charge, and lead and lithium topped up.

I always have a Anderson link plug. And disconnect if unused more than a day or so.

The cells below 2 volt are likely completely destroyed.

To find out you need to put about 1% of the charge back. That will bring the volts up to 2.5 plus. By connecting to a charged cell for a minute or two. As Shirley said, long cable, thin wire, to limit current. Tap it on and off for a bit until no spark visible, then connect for 5 mins. Then measure voltage after disconnecting. If ok, charge. I doubt it will be successful.

[FJC10]

Any that were not connected to a chair will likely be fine. Measure them. 2.5V or higher, no worries.

A chair that is turned off, stupidly still DRAINS batteries... Its the reason almost all unused chairs have wrecked batteries, and why you need to keep lead chairs on a float charge, and lead and lithium topped up.

OMG!!!, a power switch! Why they not use a simply power switch? Standby mode in a wheelchair I think have no sense!

I always have a Anderson link plug. And disconnect if unused more than a day or so.

It's common sense! except for wheelchair manufacturers.

The cells below 2 volt are likely completely destroyed.

To find out you need to put about 1% of the charge back. That will bring the volts up to 2.5 plus. By connecting to a charged cell for a minute or two. As Shirley said, long cable, thin wire, to limit current. Tap it on and off for a bit until no spark visible, then connect for 5 mins. Then measure voltage after disconnecting. If ok, charge. I doubt it will be successful.

Can I use one AC ADAPTER (from a tablet) OUTPUT = 5.2V 1.35A + this voltage regulator to 2.5v?:

https://www.amazon.co.uk/Regulator-Volt ... B00GX3YWNE

[Burgerman]

No because there's nothing to limit current. You will blow the board. Did you know, a transistor is the fastest fuse on 3 legs?

You can use the 5V supply directly if you wanted. You just need to add a 4.7 Ohm 5W resistor in series to limit current to 1A Maximum (that's what you will get with a direct short or a 0 resistance 0v battery).
Swap to a 2.47 Ohm resistor once you see say 2v.

As the battery charges the current will fall lower. It may take a few hours to see a change.
But BE SURE you take the power away before it exceeds 3.60V
In fact you only need charge to about 2.700 to 3.00V. Then use the PL8.

[FJC10]

Ok.

Best option:

https://www.amazon.co.uk/Adjustable-Reg ... 00MA01L92/

or:

https://www.amazon.co.uk/Eventek-Variab ... 071HW378T/

or... anything better for about £60/80 maximum?

[Burgerman]

You can use those. But you dont need anything. Charge one good cell. Then use a long lenght if wire like speaker wire. And charge the dead ones with a full one till they will stay above 2.5V.

Or if you want to play, tell the PL8 you are charging a 1 cell or 2 cell Nickel Hydride. Set max amps to 1 or 1000mA.

Then see if it will charge. Set cell count to not do auto. Tell it 1s or 2s manually. See what it does. Manually watch the volts and stop it if it goes above 3.6v Nicad is constant Current. Not CV.

Theres nothing to fear. At 1A it would take 75 hours to fully charge!

They are likely junk anyway.

[Gnomatic]

OMG!!!, a power switch! Why they not use a simply power switch?

I did something like this when I wired my pack to my chair. The pack itself is 24v, but I installed the bus bars on such a way it is effectively two 12v packs, wired in series. Not unlike the way two lead bricks are wired together in a chair. The pos side of one of my pack'ss 12v halves, is wired to the the neg of the other with 8AWG battery cable. With this 120A Push-To-Trip breaker in between, mounted in a convenient location.

With the breaker engaged, its a single 24v pack, and the chair etc. gets power. Trip the breaker, and it's two 12v packs, not connected to each other. And nothing gets power.

[Burgerman]

That will work too. If you do the same on a lead powered chair, or lithium, you can charge lead full, or lithium to say 70% and then leave it for up to 6 to 12 months.

If you dont break the circuit somehow, the battery discharges at around 6 to 18mA dep on chair I measured, all day every day. So the chair must be on float, or charged every couple of weeks lead, every month lithium.

Lets say 6mA. Thats 24 hours so 24 x 6 = 144 a day. And 1008mAh or 1Ah per week. Doesent sound a lot, but lead must be full or it sulfates. If its 18mAh then after a week thats 3Ah!
12Ah month just sat.
72Ah in 6 months... Lead dead. Remember it also has some natural internal losses too. So 5 months?

[LROBBINS]

OMG!!!, a power switch! Why they not use a simply power switch? Standby mode in a wheelchair I think have no sense!

Your Dynamic controller does have a real honest-to-goodness on/off switch and a high-current relay as well. The parasitic load is not because of a standby mode; it will be there even with the controller's electronics turned off and with the relay open as long as the battery is connected. The biggest part of that is the leakage in the large electrolytic capacitors in the high-current circuitry. They have to be kept charged even when the chair is off or a very large current would flow every time the relay closed, and the relay would be destroyed in short order. There are probably some other small parasitic loads as well, such as a voltage divider or two that waste a mA and are used as part of the safety checks.

The only way to keep the battery from discharging (except for internal losses) is to completely disconnect it.

[Burgerman]

Fit https://www.amazon.co.uk/d/Automotive/L ... B0051OEC4A on every chair. If you want to leave it unused, turn it off.If its lead, you can leave it up to 6 or 8 months no problem. As long as its fully charged beforehand.

If its lithium, same, but balanced and around 70% charged.

[snaker]

I full charged all 17 cells. Now I am checking their self-discharge.

I recharge a cell which was full charged 7 days ago (12th Aug). Before recharging, its voltage is 3.36V. After recharging, 280mAh is returned. Is that normal?

[Burgerman]

It is if ALL THE REST are similar.

If a few take more, then it can be a problem. Less, no problem but they must be matched with one that took more.

However a week isnt long enough.

Charge all.
Now Discharge the suspect one fully as per the settings on the preset I made. What does it read?
Recharge that one again.

Now put all the cells in a box, and leave them somewhere cool for a month.
Then recharge every one, write on it the amount returned in mA.
Now make groups of TWO for your 150Ah pack. With the same TOTAL amount returned as close as possible.

So if one cell has high self discharge, you match it with a low one...
If two are average, you match them with each other.
Then when connected in parallel these will all have the SAME TOTAL discharge over time and so stay in balance.

[snaker]

Should I discharge and recharge all cells to check their real capacity? Or do I just need to check some of them?

[Burgerman]

You can do the completed pack once. So you know. It will test capacity of each group individually. But test the suspect cell(s) now.

[snaker]

I checked the weakest cell. This cell had to be rescued due to its low voltage 2.2V. The result is:

Recharging:
240mAh returned (after 6 days).

Discharging (discharge voltage = 3.00V):
70Ah sent out.

So, this cell has an usable capacity of 70Ah. Its real capacity can be even higher.

I remember that charging a cell from empty 2.7V to 3.2V takes only 3Ah. But I monitor discharging from 3.2V down to 3.0V and see it sends out 10Ah.

[Burgerman]

Its looking like its still usable. Once discharged to 2.7V you have most of its capacity. The charger will stop automatically at 2.70V as thats what I set it too.

After that you have at best 1 or 2 percent. And possible damage. Best not to go there.

I remember that charging a cell from empty 2.7V to 3.2V takes only 3Ah. But I monitor discharging from 3.2V down to 3.0V and see it sends out 10Ah.

The actual voltage, and height of curve, depends on load or charge Amps, and internal resistance. The only part that matters here is discharge. When charging you push the curve "up" so see 3.2V too soon...

[ex-Gooserider]

There are some grounds to be wary about using a circuit breaker as a power switch... Many are not really designed to deal with being used as switches and don't have the cycle count rating.... A device designed as a switch will have a very high cycle count since the designers expect that it will be used a lot. However the typical use case for a breaker is that it only cycles if tripped or on the relatively few occasions when it needs to be turned off, so they only design for hundreds of cycles instead of many thousands...

Cycling at minimal load is better than at full power, but there are still mechanical wear issues...

Not saying don't do it, but I'd advise checking the exact specs on the part (manufacturer data-sheet) for how it is rated for cycle count and being aware that it's a potential weak point...

ex-Gooserider

OMG!!!, a power switch! Why they not use a simply power switch?

I did something like this when I wired my pack to my chair. The pack itself is 24v, but I installed the bus bars on such a way it is effectively two 12v packs, wired in series. Not unlike the way two lead bricks are wired together in a chair. The pos side of one of my pack'ss 12v halves, is wired to the the neg of the other with 8AWG battery cable. With this 120A Push-To-Trip breaker in between, mounted in a convenient location.

With the breaker engaged, its a single 24v pack, and the chair etc. gets power. Trip the breaker, and it's two 12v packs, not connected to each other. And nothing gets power.

[Gnomatic]

Thanks, Goose. I'll keep that in mind.

In my case, I think it'll be fine, as the breaker will be manually tripped very infrequently. For me this was a two-birds-with-one-stone solution. I needed a breaker for my pack, and also wanted to be able to easily cut all power to the chair. This particular breaker does the trick.

[expresso]

thats one of the best brands - breakers - at the most - if you trip it twice a year - that would be 20 times in ten years i am sure it can handle many more - i like that idea - winter time - you can flip it and leave it alone -

[FJC10]

Fit https://www.amazon.co.uk/d/Automotive/L ... B0051OEC4A on every chair. If you want to leave it unused, turn it off.If its lead, you can leave it up to 6 or 8 months no problem. As long as its fully charged beforehand.

If its lithium, same, but balanced and around 70% charged.

Nice switch.

Why 70%? My 72 cells was stored at 100%...

Well, first attempt of recovery:

1S NiMH error 1,875V



2S NiMH OK! I manually stopped it at 3.062v:



Charging Preset "Life 1S Headway 1S":



















What is your opinion? Looks like recovered, right?

[Burgerman]

Your cell looks to charge OK. But capaciy in 13Ah?

You wont know till you measure its discharge capacity. But your power supply is all over the place... Or you have a bad connection on the power supply leads or cell connection. Crimps?

Why 70%? My 72 cells was stored at 100%..

Lithium does not like full. Or empty. Likes to be 30 to 70 full. For long term storage.

Think breathing. Breatth in full breath, and wait months. Its uncomfortable. SAME breathe out full breath.... Wait. Not nice!

Above 3.7V or below 2v means damage ...

[FJC10]

Your cell looks to charge OK. But capaciy in 13Ah?

Yes, 13020mAh. First discharge and charge cycle = from 0 mAh to infinity and beyond!!

You wont know till you measure its discharge capacity. But your power supply is all over the place... Or you have a bad connection on the power supply leads or cell connection. Crimps?

No, I think all OK.

See the chart of cycle life from oficial Headway specifications PDF:

Firsts approx. 50 charge cycle are 13Ah.

You wont know till you measure its discharge capacity.

To do a discharge and charge cycle this preset is ok?

lifepo4 discharge.PNG (10.3 KiB) Viewed 11209 times

[Burgerman]

No.

Use the 1 cell charge preset I posted here. Set discharge volts to 2.7V if not already, and discharge current to say 6A for a 2 hour discharge. (1/2C)

[FJC10]

No.

Use the 1 cell charge preset I posted here. Set discharge volts to 2.7V if not already, and discharge current to say 6A for a 2 hour discharge. (1/2C)

[Burgerman]

Yes.

[FJC10]

Yes.

Thanks!

Done!

Everything looks correct... right?

[Burgerman]

Is that a 12Ah cell or a 15Ah one?