PINNED - Lithium battery conversion/info

[Gnomatic]

Mine works fine so far. Its a no frills supply. But it gets the job done.

[Mind The Gap]

Hi all
Batteries out for delivery today, nice weather and I'm stuck in hospital.☹️

[Burgerman]

[robert97]

this is a typical charging one of my two 7S5P headway 38140S packs.

a good balanced charge

as you can see, the pack took 41917 mAh and was perfectly balanced.
given

" Lithium batteries hate being fully charged, ... "
Re: Vienna aka Viennese
Postby Burgerman \xbb 24 Mar 2018, 10:23

and

"To get good cycle life tesla/volt ... and a max charge of 80%. "
Re: PINNED - Lithium battery conversion/info
Postby Burgerman \xbb 08 Mar 2018, 21:37

does it make sense to stop charging early most times? and fully
balance/charge occasionaly?

[expresso]

From the looks of that Graph - You are already not fully charging - i mean its already being stopped - at 3.55V your good and you should balance them all the time - i believe this to be correct way - BM will correct me for sure - its looking good

[Burgerman]

I charge at 3.550V per cell. The manufacturer says 3.650. Why? Because that much overcharge allows a degree of natural balance as the full cells cant charge more. and energy is wasted as heat. So they get less cells back as damaged due to use of unbalanced cells. They do that because the typical charger is a 2 wire dumb charger and relies of a typical BMS which has too low balance current and lets the cells go over and under the target voltage for many hours while attempting to balance...

You can reduce it to 3.525 or 3.500V if you want as a minimum, but charge time will be slower, longer at CV before true balance is achieved.

Your CV time is already too long though. Whatever the termination point mA is on tha PL8 now, increase it by 50% at a time until you get a termination at about 1 to 2 hours after it attains a balanced CV top voltage. On your graph around 3.6 hours point.

You only need longer at CV if the pack is slow to balance. If its good, as yours is, set termination Ma higher, CV timeout to say 2 hours, too.

[Burgerman]

Remember that tesla cars cells are typically 500 full discharge cycles only as they are just lico cells as used in a laptop. Thats 4.2v to 2.5V to use full capacity. But teslas battery management never allows the cells to be fully charged. So they do not deteriorate fast. It says 100% at a lower approx 4.1V per cell. And the car says its dead when about 25% remains, and then stops.

Dont run them low, or high, and dont take massive currents or fast charge them, and they last way longer than the 500 cycle limit suggests. Much the same applies to the 2000 cycle LiFePO4 chemistry we use too. Except it starts off with 4x the expected life and does not burn.

Lithium lasts as long as you plan it to last. With correct treatment they will go on almost forever. With wrong treatment you get 1 cycle. With "full" rated capacity used and recharged, they dont last.

Fitting a BIG pack and only using say, 20 to 70 percent of it most days means it should last practically forever. Because of lower average % discharge daily and lower current on charge and discharge per cell. Fitting a lot of Ah is the correct way to go lithium. It pays back massively. Charging to just 70% or 80%is hard to do with our LiFePO4 packs, since the voltage cant tell us this. So charging to 3.500 or 3.525 and keeping CV level down to as long as it takes to balance, and then to top up slowly with a low current (typically an hour of CV) is the kindest thing for them. But thats still 98% full. But its volts they dont like. Keep away from the manufacturers 3.365V!!

Teslas LICO cells, are never full, even when the car SAYS they are. He uses a 140KWH rated pack and uses 100KWH from it. Allowing 20 percent unused at the top and bottom of the capacity. For service life reasons. And some say to only charge to 70% for even better lifespan. https://electrek.co/2018/04/14/tesla-ba ... tion-data/

[shirley_hkg]

Cool connector. What's it called ?

[Burgerman]

Dunno. But its huge! Unless thats a photo trick.

[Gnomatic]

Doing a bit of maintenance on my chair getting it ready for warm weather. In the process I pulled out my battery pack and decided to see what kind of shape its in after one year of use. I fully discharged my 90Ah pack till one cell hit 2.9v, then charged it back up.

So 89Ah returned. With the charger not violating the laws of thermodynamics, that means the actual amount of power returned to my pack is a bit less than that. So in a year on I've had a bit of degradation. I'm not surprised by that. A big heavy chair and a big heavy me, with a fairly small pack. I'm off pavement quite a bit, so I'm working the cells hard.

Still though, not bad. It might be good for me to build a 30Ah add on pack at some point. 90Ah has proved to be plenty of range for me. But with the add on, it would lighten the load on the cells a bit. Especially when I know I'll be going on hiking excursions etc.

With the PL8 saying 89Ah returned, what's the best guess of the actual capacity of my 1yr old pack now?

[Burgerman]

So what Ah was REMOVED from the pack, when the first cell hit 2.9V?
THAT is the all important figure and deadly accurate.
With the following provisos:

Never test to full capacity, unless a spare cell, since its very bad for the cells and you can finish up with a cell that has increased self discharged rate very easily. To test and measure FULL capacity you must discharge at around 0.1C to 2.50V. Or use a higher rate and a CV discharge to 2.50V.

So unless looking for ultimate capacity measurement at 100% discharged never really try to go lower than your 2.9v (or 2.8v at the very lowest). But that wont measure full capacity. Theres also a false drop off at around 90 percent discharged that looks like thats it. But that flattens out again for a while if you keep going. But best not to try that unless you are desperate to make it home... So you will measure about 11Ah this way from a true 12Ah cell if you discharged it fully at a low rate.

You cannot measure Ah back in with any level of accuracy.

So 89Ah returned. With the charger not violating the laws of thermodynamics, that means the actual amount of power returned to my pack is a bit less than that. So in a year on I've had a bit of degradation. I'm not surprised by that. A big heavy chair and a big heavy me, with a fairly small pack. I'm off pavement quite a bit, so I'm working the cells hard.

I would be surprised if theres more than 3 to 5% loss of actual capacity. You cannot measure Ah back, to determin capacity that way. For these reasons.

You do not know how much was left after you stopped discharging. So you might get only 90Ah back into a 100Ah battery to be 99% full because it wasnt empty. And the last 1Ah to 3Ah may take 6 or 8 Ah to complete due to thermal losses and balance losses (1A dumped to a resistor begining as soon as CV is reached, which all add up.
These losses depend on balance settings, and termination current as much as anything. But also in cell internal losses at 3.600V. And on resistance in the whole system. The loom, cells, and the charger all have internal resistance and get warm. Its quite normal to be 97 to 99% efficient at the early part of the charge. And much less as charge starts to reach CV.

With the PL8 saying 89Ah returned, what's the best guess of the actual capacity of my 1yr old pack now?

I dont think it is very helpful. What did it take out? Add to that say 5 to 7% remaining that you didnt remove. Thats more realistic.
But at a guess I would say about 3% less than when new. Going by my own packs. Unless theres a fault.

[Gnomatic]

Thanks for the reply.

I don't know how much I took out Without a supply with adjustable voltage, I'm not able to use my load dump and the PL8 to do a regen discharge the way you do, with the PL8 controlling the whole thing, measuring how much power its taking out of the pack etc.. And w/o regen discharge with load dump, the PL8 is very slow by itself when discharging.

So I just connected my ~20A load dump to my pack. Used the PL8 to monitor, and when cells hit about 3.1v, I disconnected the load dump, and used the PL8 to finish discharging. Then charge the pack up.

So your 3% best guess is all I was asking for. My intention was not extreme precision. So all in all my pack seems in decent shape after a year of use. No returning to lead bricks.

[Burgerman]

With well maintained lithium, on a relatively large pack, we seem to get around 3 to 4 percen capacity loss initially, then it seems to stop deteriorating any more unless abused in some way. At least the caacity loss seems to slow greatly.

After a year on heavily used lead mine are generally declining ever faster. The opposite to what we see with lithium. And usually down to less than 80% remaining capacity. But because the IR also goes up markedly as they deteriorate you actually get much less than the 80% range you would expect. It becomes very noticible fast! This can be largely avoided and last about 3 year+ if you regularly whack about 40A, 29.40V back in (odyssey) for an hour or so every time you sit near your computer, or drive anywhere. So they dont actually ever get low! It keeps them full/younger!

[ex-Gooserider]

Cool connector. What's it called ?

It looks like some sort of Anderson variant, but that doesn't help much. I tried looking at http://www.ddclm.com/ based on the name in the photos, but the site is in Chinese or similar ideographic language, and I don't see any buttons for getting English, so you are probably better off checking it out than I am...

I'd say the nicest thing about it is that little lever setup to ensure positive hookup and locking - might be really good for our members that have trouble manipulating regular Andersons...

ex-Gooserider

[crypmanii]

Has anyone on here converted an Omegatrac to Lithium batteries? I've been reading through this thread but with 174 pages of information its a little overwhelming. HaHa. I know its not a quick "plug & play" process to make the conversion. Is there a kind of walkthrough for making the conversion? Something like this may have already been posted, and if so I apologize for asking, but I just haven't seen it yet within the pages I've already looked at.

Any guidance would be greatly appreciated.

Thanks all.

[expresso]

If you like you can start here

viewtopic.php?f=2&t=6873

this is an ADD ON pack which you can add to the lead in the chair - you can just look here to get an idea on a much smaller pack -

you can see its just two rows of cells - - but its the same if you make one large pack for the chair - just keep adding more rows of cells -

i started this way with help from others here - my intention was just to make an ADD ON to see how it works out - two weeks after that - i realized how great it will be and since then i have done a full chair lithium with an ADD ON - this one actually and use a 36ah ADD ON with lead on another chair -

its addictive and soon will be doing another chair -

this section is fairly easy to to understand and view pictures etc, - if you can make this ADD ON - you can make the whole chair also -

there are other types of Cells now which may be easier also - instead of these headways -

take your time and figure it out what can fit etc, - you wont go back to lead after lithium

[ex-Gooserider]

Not an expert on Omegatrac, but I don't know of any reason why it would be any more of a challenge or more difficult than it would be on any other chair...
The process is not THAT difficult, ( unless you're Expresso... ) but it does require a good understanding of basic electrical concepts, and a reasonable level of ability to do basic mechanical and electronic build tasks - which is often the biggest issue for those of us in chairs...

It has also gotten a bit more complex lately in that we are getting more choices about what cells to use, but this may be a good thing as it lets us make even better packs than used to be possible...

The basic approach is still the same =
1. Figure out how much space you have available
2. Pick a combination of cells that will fit in that space, ideally the one that will give you the highest Ah capacity.
3. Get an appropriate charger (currently the PL-8) and power supply
4. Get the cells, and test them to find the right arrangement to get a pack that will balance readily,
5. Build the pack and install....

ex-Gooserider

Has anyone on here converted an Omegatrac to Lithium batteries? I've been reading through this thread but with 174 pages of information its a little overwhelming. HaHa. I know its not a quick "plug & play" process to make the conversion. Is there a kind of walkthrough for making the conversion? Something like this may have already been posted, and if so I apologize for asking, but I just haven't seen it yet within the pages I've already looked at.

Any guidance would be greatly appreciated.

Thanks all.

[Schultz5905]

Does anyone have a diagram of a 5 x 8 cell pack.

[Mind The Gap]

Hi BM

Any chance of a preset for a 8s7p 105ah Lifepo4 pack for pl8.


Cheers Paul

[Burgerman]

Will do, but expresso has one, and may post before I can as I am stuck on bed with wrong computer at this moment!

[expresso]

Hi BM

Any chance of a preset for a 8s7p 105ah Lifepo4 pack for pl8.


Cheers Paul

this is what i use on my 105ah pack - you can change the charge rate to what ever you like its at 15A now - i use it at 20A to 25A in the summer when i use the chair alot more - or 35A if i want to charge up fast in a few hours

[expresso]

this is the latest one updated with some changes that BM suggested - i use this one now - digital on/off and 2mv deadband in the balancing section of the PL 8

other than those two changes its the same preset -

[Mind The Gap]

Thanks Bm, expresso

[Scollard]

Well I'm happy to say that 2 years in and my battery pack is as good as ever. I only need to charge it at the most once a month. Remember it's a scooter and it's used mostly as an end point. When going from point A to B it rides on the back of my Cayenne. About once a month I put back around 40 to 60 AH. I charge more often if I'm on the bike paths with my wife. I can probably run about 50 miles on my 105 AH pack.

I just got another scooter, slightly smaller, and I've just ordered the cells to make a 60 AH 22NF sized pack.

[expresso]

Well I'm happy to say that 2 years in and my battery pack is as good as ever. I only need to charge it at the most once a month. Remember it's a scooter and it's used mostly as an end point. When going from point A to B it rides on the back of my Cayenne. About once a month I put back around 40 to 60 AH. I charge more often if I'm on the bike paths with my wife. I can probably run about 50 miles on my 105 AH pack.

I just got another scooter, slightly smaller, and I've just ordered the cells to make a 60 AH 22NF sized pack.

[Burgerman]

At the current state of compact lifepo4 cells with many size/shape choices now, and with enough proof of concept out there on this forum alone, for almost a decade, its about time that the manufacturers were using lithium as a matter of course.

Its crazy to see any self respecting EV manufacturer fitting lead bricks today. They really should be embarrassed.

You wont find them in tools, ev's of any kind from elctric superbikes bikes, or electrified bycicles, electric cars, trucks, buses. When was the last time you saw a lead battery in a phone, rc toys, computer, ipad, torch, mower, or anything? Its 2018!

They are way more reliable, lighter, 10x longer lasting, more compact Ah for Ah, faster charging, allow more Ah in the same space, and amazingly, even though they suffer no peukert, and so actually give you your xxAh that you pay for, are as cheap today as MK gel on an equal Ah basis.

[Mind The Gap]

Hi, could you tell me the formula used please.

Cheers Paul

Here are my groupings ....
(60 day static discharge test)

Group 1

Cell 12 - 122
Cell 16 - 109
Cell 22 - 84.3
Cell 23 - 106
Cell 36 - 107
Cell 43 - 95
Cell 44 - 189

Total 812.3mAh


Group 2

Cell 04 -187
Cell 06 - 98.9
Cell 10 - 112
Cell 15 - 106
Cell 17 - 127
Cell 21 - 89
Cell 28 - 91.9

Total 811.8mAh


Group 3

Cell 13 - 185
Cell 24 - 117
Cell 38 - 115
Cell 39 - 90.2
Cell 42 - 99.8
Cell 46 - 106
Cell 53 - 99.5

Total 812.5mAh


Group 4

Cell 02 - 98.2
Cell 07 - 95.8
Cell 09 - 110
Cell 20 - 103
Cell 35 - 121
Cell 41 - 103
Cell 45 - 180

Total 811mAh


Group 5

Cell 08 - 150
Cell 31 - 101
Cell 37 - 103
Cell 47 - 98
Cell 49 - 135
Cell 50 - 122
Cell 54 - 102

Total 811mAh


Group 6

Cell 03 - 109
Cell 14 - 114
Cell 25 - 123
Cell 29 - 107
Cell 30 - 148
Cell 52 - 102
Cell 55 - 109

Total 812mAh


Group 7

Cell 01 - 101
Cell 18 - 147
Cell 27 - 115
Cell 32 - 105
Cell 33 - 108
Cell 34 - 116
Cell 56 - 119

Total 811mAh


Group 8

Cell 05 - 109
Cell 11 - 116
Cell 19 - 100
Cell 26 - 116
Cell 40 - 111
Cell 48 - 117
Cell 51 - 142

Total 811mAh


Assuming my primitive Excel skills didn't fail me, all 8 of my groups are within 1.5mAh of each other following static discharge testing and grouping. I don't see much point continuing to fiddle trying to make that number smaller. Feel free to check my math ....

[expresso]

Thats great if you got them that close - i agree if you did - no use trying for better - you should be good to start the build i would say -

to be safe wait for BM - maybe he has something to add that i dont see -

[Burgerman]

No. Way better than needed. TRhey will vary as they age anyway...

[shirley_hkg]