PINNED - Lithium battery conversion/info

[Burgerman]

What worries me more is that if you are struggling to connect a battery up to a charger - then how on earth are you going to sort out the roboteq, one off wiring loom, joystick/scripting/RC/current sensors/brake, SSRs, MOSFET fail and emergency contactor etc, + complex calibration and setup? Because that stuff really is complicated. Or should I say its very simple on the face of it, and equally simple to do it wrong... And get anything from £££damage to an uncontrollable or hard to control chair, or a dangerous runaway or huge unreliability. It has to be done in a professional way and to the same standards or better than a manufacturer would do it. Literally 1000 details and all must be right 1st time. You are designer, expert, development engineer, of chair, battery system, control system, and test pilot... There's no teams of experts for every part.

Non of this stuff is simple. You really must understand it, all of it, and know what you are doing in minute detail or it will end in tears, smoke or broken bones, or never be finished or properly functional. You cant expect to give the problem to someone else to figure out because they wont.

By the way, I trust this lad, Danny. He is genuine, and trying his best, isn't just doing it for the money he is being paid.

Seriously if your guy you have doing your chair cant wire up a battery/charger then I think you need to either supervise it or oversee it yourself, every moment. Or find someone that can understand it. He may be a nice guy, but he isn't up to the task. The charger is the easy bit.

But... It may be that he has wired things incorrectly and blown the 12, 13 balance inputs on the charger? And so now it doesn't work even if correctly wired. A simple test with a multimeter will tell you if the wiring is correct. If it is then he has quite possibly damaged the charger previously.

As I keep on trying to explain. You really cannot just "farm this out" and get a chair built. You will never get it done right. Its too involved, too many details to expect someone else to get right. Its one of those things that *you* must understand, do yourself, or oversee 100 percent, all the way.

This is one reason I just ignore those that say they can "get some built" or can build them for others. Too much time, labour, detail in a one off chair for that to ever work without mass production.

[funkykeyboard]

Thanks very much for the honest and frank reply. Much food for thought.

Looks like I've been overoptimistic just like me to do that. Looks like I will have to start selling some stuff LOL. I thought I would just be able to copy yours. Anyway, thanks again for your advice.

[Burgerman]

You can.

IF you have enough knowledge and skills to understand it all.

About 80 percent of what you need to know and understand is in the Roboteq manual, PL8 or Hyperion charger manual, etc. This isn't like lego bricks. Or a case of just buying the same bits and plugging it all in. You wont find a wiring diagram for the pod for eg. Because I figured it out as I went along. As did will. I wouldn't know how to draw or describe it.

But all the parameters, and info you need is in the two manuals. Did you read them?

[funkykeyboard]

I don't have those skills. And even if the bloke does have the skills to do it, I'm not sure he will have the amount of time it will take. I'm paying him for about 6 hours a week.

What I have is;
1. All the engineering done, below the seating.
2. The battery pack built.
3. The Robotech controller.

I was going to have it if I could, but I'm not really bothered about 14 or 15 mile an hour 8.5 would do me. My main attraction to the wheelchair is the engineering, the larger tyres which will give suspension to my arthritic hips, allow me to do some of the country walks in my area, and go on the beach. Like computers, Im more interested in the utility, than building the bloody thing.

Danny has successfully managed to put lithium batteries on my Life stand wheelchair. So what's the way round this problem? I know it won't be a Rolls-Royce like yours, but could I create a lesser species? Just buy an existing system like the one for my life stand, and just plonk it on top? If it works on my life stand wheelchair, why not this one? Even if there was problems marrying the 8.5 mph motors, I'm sure I could get one of the engineers out from life stand to program that side of things.

I'm sorry I am so ignorant of the necessary technical knowledge to discuss this problem, get me on politics or history and I will talk your socks up and down

[Burgerman]

Danny has successfully managed to put lithium batteries on my Life stand wheelchair. So what's the way round this problem?

To reduce the technical issues to a easy level I suggest reconfiguring your battery to 8S and so 24V equivalent. No loose screws! Careful simple wiring the same as your other chair.

Then use the R-net 120 or plug an play controller or the DX2 120 Amp 24v controllers. Any that you can get a oem programmer for.

One thing though. Those tyres are good on soft ground. And running at low pressures they take out vibrations really well. (my problem, spasm!) But for large amplitude bumps like level changes they don't help much. That takes suspension. Which would add width... Everything is a compromise.

[maker102]

I charged all of my cells in groups of 6 at a time. When I individually checked the cells for Output Capacity about 85% were between 55-70 milliamps. The other 15% I pulled from the charger at approximately 150-200 milliamps replaced and charged to approximately 90%. These cells were part of the grouping of six with the other 5 cells charging normally. What do you feel I should check? I have tried recharging some of them a 2nd time with some charging normally ie 30-60 milliamps. Was I right in pulling from the charger? Could this be a software or hardware glitch in the Hyperion Charger? Bad Cells? Anything I might have screwed up? After getting two cells like this I decided to recharge the cells to 100% and plan on setting them aside for another month. Your thoughts would be greatly appreciated.

[Burgerman]

I charged all of my cells in groups of 6 at a time.

To 3.600v and allowed them to sit on the charger until the computer screen showed no current still flowed? (0mV) Full...

When I individually checked the cells for Output Capacity about 85% were between 55-70 milliamps. The other 15% I pulled from the charger at approximately 150-200 milliamps replaced and charged to approximately 90%.

Capacity checking would involve discharging to 2.5V and measuring actual capacity. Do you mean, connect each individually, and charge, and note the mAh returned? If so then this is correct, and is WHY you did this. The amount you returned to each cell was the amount LOST over the period. You should write this on each cell. Completely ignore any % charged reading it is meaningless.

These cells were part of the grouping of six with the other 5 cells charging normally.

No idea what that means...

What do you feel I should check? I have tried recharging some of them a 2nd time with some charging normally ie 30-60 milliamps. Was I right in pulling from the charger

No idea what you pulled from the charger or why you pulled them?
30-60mA?? Or mAh? Cell, or group of cells? The reason you did all this was to assemble groups with the same TOTAL self discharge (capacity in mAh lost) over time. So add a high discharge one to some low ones. Just add them up!
Unless I know if you are charging or measuring individually, and measuring mAh (capacity returned) and not mA (charge current) then I have no idea what you are actually doing!

Could this be a software or hardware glitch in the Hyperion Charger? Bad Cells? Anything I might have screwed up? After getting two cells like this I decided to recharge the cells to 100% and plan on setting them aside for another month. Your thoughts would be greatly appreciated.

Not hardware or software. What is: "two cells like this" ???

30mA is a charge CURRENT.
30mAh is a charge AMOUNT or quantity of charge.

You were testing how many mAh were returned to each cell after X time. Only. On subsequent individual recharge. So you can assemble bigger parallel groups of bunches of cells with the SAME self discharge rate total.

So one 150mAh cell with a bunch of 30mAh ones. Etc. That's a small difference. The reason some cells read differently, was the exact reason you were testing them!

[maker102]

I got most of what you are saying, I charged the batteries in parallel 6 in a group. When I checked them I got the following output capacity readings:
Cell 1 65
Cell 2 57
Cell 3 260 and climbing when I stopped the charging
Cell 4 63
Cell 5 49
Cell 6 66

I tried putting the high cell #3 back on the charger and the charger reported back a cell capacity of 35-40
This was the case in 3 of 5 cells. The other 2 continued to charge reporting an output capacity of 300 and still climbing.

I guess my question is: is it normal to have a 250 plus mAh output capacity in 20% of the cells?

[Burgerman]

I got most of what you are saying, I charged the batteries in parallel 6 in a group. When I checked them I got the following output capacity readings:
Cell 1 65
Cell 2 57
Cell 3 260 and climbing when I stopped the charging
Cell 4 63
Cell 5 49
Cell 6 66

No you didn't!
You got the following RECHARGE mAh replaced, before the charger said full?
After a month stored at FULL condition?
Capacity reading is what the cell stores. And you would need to do a full discharge test to find that...

Question 1. Do you have it set to continue when charging, and WATCHED the mA decrease on the PC screen, fall over time to zero? (it gets to 50mA and then drops to 0mA. For every cell or cell group. Or they are not full...
Question 2. The figures above, are the replaced mAh to read full?

I tried putting the high cell #3 back on the charger and the charger reported back a cell capacity of 35-40
This was the case in 3 of 5 cells. The other 2 continued to charge reporting an output capacity of 300 and still climbing.

High cell means the one that needed the most returned? That would be the lowest cell!
You mean RETURNED mAh capacity by highest?

I guess my question is: is it normal to have a 250 plus mAh output capacity in 20% of the cells?

Yes. This is why you are testing them That's a quarter of 1 Ah. The best cells lose nothing. The worst cells can lose 5% a month. Now you know which are which, you can assemble 6 cell groups with the same TOTAL self discharge. Just add up all the RETURNED mAh figures until each group is as close as possible...

So now you have a choice. Build the pack with the "worst" cells as long as you can make the TOTAL PER GROUP add up until its close, or replace the "bad" cells.

0 to 5 percent per month capacity is within spec. Now you know why you SHOULD select and shuffle cells to build a better pack.

[maker102]

Got it, I was going on a previous post where it was stated I should see 10-100. When I seen triple that, I got concerned. Anyway I am going to mark those cells and recharge all the cells and see what happens in a month or so. When I bought the cells I got 6 extra so the lesser cells will be set aside. Thanks for the help

[Burgerman]

Any that lose a lot of charge faster are best swapped for ones that don't, but 1/3rd Ah in a month is still ok.

Now you know, discharge each cell by approx. 30 to 40 percent. So remove 4Ah (4000mAh) from each one for storage.

[maker102]

Will do. Two more questions:
Where did you find the Battery Screw Nylon Caps? I really like the idea.
And for a friend: In your opinion what is the best stand alone (self contained) PB battery charger for the money?
As always thanks for all your help

[Burgerman]

Cant remember where I found them in bulk cheap. They are used on motorcycles and anything that has allen head bolts to finish off and look tidy. Probably find some on ebay. They are pretty essential.

http://www.ebay.co.uk/itm/M8-6mm-HEX-BL ... 2ed229a350 wrong size but like these.

http://www.ebay.co.uk/itm/M5-4mm-HEX-BL ... 2c83915787 THESE may be the correct ones for button head m6 bolts.

http://www.ebay.co.uk/sch/i.html?_odkw= ... r&_sacat=0 more

But search the web because I bought bag 500 for about 1p each.

[Raymondo]

Hi BM,

I am raring to get into lithium. I've read all your BM3 info with relish. Fantastic stuff. Having gone onto your 'convert a powerchair to lithium' page it says at the end "In a month or so I will add more to this page, as I intend to do exactly this and build two batteries for a stock powerchair and will photograph every detail as I go along. A picture is worth a thousand words and all that...". Not sure when you posted this.. Are you still working on it?

[Burgerman]

Well I have built several 12V "BATTERIES" as such for scooters and powerchairs, but not got around to updating that page. But there's a thread here that you are posting on that basically tells you everything you need. And there are a few that have done the same here too.

What do you need to know?

[Raymondo]

I have just spent the afternoon reading this whole topic. A lot to take in. I need to get my thoughts organised now, do some serious planning and then I am sure I will have many questions.
Thanks.

[Raymondo]

Dear BM, I've heard some grand claims about lead crystal batteries. Do you have a view on them?

[Burgerman]

Marketing. Good cycle life, but a horrendous 7mOhm internal resistance. That gets worse as they discharge. So good for say solar or battery backup where low currents and continual currents needed.
http://leadcrystalbatteries.com/media/w ... NFJ-70.pdf

MK gel and Sonenschein gel A500 are better for service life in our type of use. And more importantly have 4.5mOhm internal resistance compared to the countless cheaper AGMs and so are twice as good as those lead crystal batts at a huge 7mOhm...
http://www.wheelchairdriver.com/MK3.pdf

Odyssey (and clones/rebrands such as die-hard) are better for fast charging, high currents that we use, and have almost the same range and yet still have good service life. 2.5mOhm internal resistance means some 3x better than lead crystal under heavy loads. Or 3x less voltage drop under load, more of the capacity usable, and better torque and control.
http://www.wheelchairdriver.com/odyssey.pdf

MK for most people, Odyssey for those that know why they need them... Nothing else is worth buying.

[Williamclark77]

A bit late, but the reason you charge, let them rest, then recharge is to assemble the parallel batteries with cells that self discharge equally. Absolutely critical? No. But, it will make balancing on each recharge quicker. As in 2-3 minutes to balance when recharged vs several hours.

You don't HAVE to do this. You can just fully charge each cell to 3.6v and assemble. Acceptable but your pack won't be optimum. NEVER assemble a pack with cells at different states of charge. It will most likely never balance or take days (literally) to balance.

I finally ran my 45ah pack down to where voltage dropped to 38 volts for the first time - around 2.7 volts per cell. On my brushless Willchair it took several days of running around on vacation, another day around the house, and mowing several acres of land. My lead battery chair can't make it through one day without opportunistic charging. Much less four days with a few hours of dragging around a 400 pound mower through chest high grass.

It took about 9 hours to fully recharge and balance (I only had one 12v power supply hooked up, making it charge 1/2 as fast). I left it sitting for a few more hours because I was busy. All cells within .003v after much abuse and resting for a few hours after the charger finished.



Truly remarkable! It held 48ah.

[Burgerman]

You still had a days use left in that battery...

[shirley_hkg]

You still had a days use left in that battery...

What ! 2.7V still holds that much energy ?

[Burgerman]

Yes, he only replaced 50Ah of a 60Ah battery.

10Ah at 48V remaining is the same as 20Ah at 24V. Not that its a great idea to go down to 2V per cell... But if you did need to its there.

[shirley_hkg]

he only replaced 50Ah of a 60Ah battery.

.

Is the real capacity of the pack verified ?

[Burgerman]

All my headway cells do almost exactly the Ah claimed at low C rate tested via the Hyperion or PL8 chargers. If run down to the 2V point by the CV method. Typically 11.5 to 11.8Ah from a 12Ah cell. So Wills shouldn't really be any different?

2.7V off load, is about 90 percent discharged because if you wait a good while and the volts climb back up to above 3V after the load is removed.

Will started with 1150watt hours. Has about 300 watt hours remaining to 100% discharged. With higher volts, and brushless motors that's about a day.

[Burgerman]

Heres a test on a 10Ah headway. Note, only to 2.5V, and still under load. So no CV discharge end.

[Williamclark77]

But 38 volts is sloooow

What has me curious though is that mine is a 45ah battery, not 60. 3p of the 15ah cells. I wouldn't think they held that much more than rated but nor would I think the Hyperion was that far off or that much lost due to inefficiency. My wiring is short and large.

I've never done a capacity test of my whole battery.

I may have a 15ah cell or two left I can do a capacity test on if I didn't use them all when I fubar'd my battery last summer. They would be in storage though. No telling when I'll be able to dig one out.

[Burgerman]

They are normally approx. what they claim. I thought that you had 60Ah battery. So 10Ah left...

If you have 45Ah then that's it. You ran them as low as you should. You CAN go down to 2 volts at a push. According to Headway specs. But it punishes the cells.

[maker102]

I found these on the internet and wondering if they will work. I have nothing to compare them to so I was hoping you might be able to measure yours.

http://www.widgetco.com/hole-plugs-covers-5MM-black

Thanks

[Burgerman]

Not sure. I will dig out my bag as soon as I can find it and take a look.

[FJC10]

Hi BM,

I am raring to get into lithium. I've read all your BM3 info with relish. Fantastic stuff. Having gone onto your 'convert a powerchair to lithium' page it says at the end "In a month or so I will add more to this page, as I intend to do exactly this and build two batteries for a stock powerchair and will photograph every detail as I go along. A picture is worth a thousand words and all that...". Not sure when you posted this.. Are you still working on it?

I agree with you, Raymondo.

Burgerman, as I told you on private mensage, I can take the photos every detail if you help me/guide me step by step to build it.

We can start with list of all we need.

For the battery:
- 72 Headway 38140S 12ah LiFePO4 Cell http://www.evassemble.com/index.php?mai ... ucts_id=21
- 72 Orange cell building blocks holder for 38120&38140 http://www.evassemble.com/index.php?mai ... cts_id=147
- 136 2 holes connecting plate for headway cell(38120&38140) http://www.evassemble.com/index.php?mai ... cts_id=156
- 144 M6x10mm STAINLESS STEEL FLANGE BOLTS BUTTON HEAD DOME HEAD BOLTS ALLEN SCREWS
Like these? http://www.ebay.co.uk/itm/M3-M4-M5-M6-M ... 1c51e719e6

- Cable AWG 14, 16, or 18 for balance...? Like these? SINGLE CORE CABLE FOR WIRING HARNESS 12-24V FLEX AUTOMOTIVE ELECTRICAL COMPONENT 5,75 amps black 5 metre, they are AWG 14 I think. http://www.ebay.co.uk/itm/351091757644? ... EBIDX%3AIT

- NORCOMP 680S13W3203L401 D SUB, COMBO, RECEPTACLE, 40AMP, 13WAY
http://uk.farnell.com/norcomp/680s13w32 ... dp/2294341

- D-SUB 25P Cover Shell/Hood Housing Metal
http://www.ebay.co.uk/itm/D-SUB-25P-Cov ... 2ec99437a9

- Ring Insulated Wire Connector Electrical Crimp Terminal 14?-16AWG? M6
http://www.ebay.co.uk/itm/20Pcs-Blue-Ri ... 20ed042a64



For 40A charge/balance cable:
- NORCOMP 680S13W3103L401 D SUB, COMBO, PLUG, 40AMP, 13WAY
http://uk.farnell.com/norcomp/680s13w31 ... dp/2294339

- D-SUB 25P Cover Shell/Hood Housing Metal
http://www.ebay.co.uk/itm/D-SUB-25P-Cov ... 2ec99437a9

-Cellpro (JST PA) PowerLab 36" Extension Cable
http://www.store.revolectrix.com/Produc ... sion-Cable

-Cellpro PowerLab, Stackable, 40A Safety Banana Plug Cable
http://www.store.revolectrix.com/Produc ... Plug-Cable

- 1M # 12AWG Soft Flexible Silicon Wire Cable Black 50cm + Red 50cm
http://www.ebay.co.uk/itm/1M-12AWG-Soft ... 1321906570

- Black Braided Sleeving Cable Harness Sheathing Expanding Sleeve (size 8mm / length 5m)
http://www.ebay.co.uk/itm/Braided-Sleev ... 0088799839

- Black Adhesive/Glue Lined Weatherproof Heatshrink Tubing/Heat Shrink Sleeving (unshrunk diameter 13mm / 200mm Length)
http://www.ebay.co.uk/itm/Black-Adhesiv ... 2a2885b834

- 40A fuse. This or other better? http://www.ebay.co.uk/itm/2-40A-24-Cara ... 0590321690
- We need holder inline for the fuse? http://www.ebay.co.uk/itm/5-X-Black-Red ... 1898214457



Charger:
- PowerLab 8 (v2) Workstation http://www.store.revolectrix.com/Produc ... Lab-8_1075
- FUIM3 USB Interface Module for 2-way data communication http://www.store.revolectrix.com/Produc ... sion/FUIM3
- Power supply (>= 24v 30A) http://www.coolice.co.uk/cfs/coolice-psu-s.html 575/1150 watt, 25 volt, 47 amp PSU's?
- A great guy to help me understand how connect all this things!
- What else do we need?