WheelchairDriver

Starting a new thread so it hopefully won't get buried by the over-caffeinated one....

I pulled the trigger a couple days ago and ordered the batteries and so on to do the lithium conversion on my Invacare project chair...

I didn't use the "Made in China.com" link that Expresso found, but I did use Ali Baba and also a search on Headway cells to find a bunch of vendors. Also while Headway Headquarters doesn't sell to consumers anymore, they had a note to contact them for referral to a vendor that does, so I did...

I ended up going with Boka, the vendor that Headway HQ referred me to, as their rep seemed willing to go the extra bit needed to get my business, including relaying messages through the Headway HQ folks when we had e-mail trouble for some reason... It was $10 more than the lowest, but they seemed to earn it.

I'll post about how quickly I get the stuff, and so on, and hope it will be a good experience... I did suggest that there were a lot of folks here that were doing Lithium conversions, and that it would be a good thing for potential future orders if they made me want to recommend them....

I saved about $200 over what Evassemble would have charged. There was a fair bit of variation in the prices, but the big difference was in shipping... All of the vendors appear to be using some sort of air-freight, as they all claimed to promise delivery in under 10 business days....

I'm attaching the ODS (Libre-Office) spreadsheet that I made with the vendors I checked... No promises that anyone else would get the same prices, but at least it's a starting point... As usual, rename the file by changing .zip to .ods



ex-Gooserider

What is a .ods???

Nothing industry standard on windows opens it. Tried Word, Excell, Adobe PDF, etc. It betamax inst it...

But are they available/safe?

Any links where to buy or specs? There are BMS for those, I saw them a while back. So cell balancing etc must be required?


Heres a page on different types of lithium with loads of info. http://batteryuniversity.com/learn/arti ... ithium_ion

Burgerman wrote:What is a .ods???

Nothing industry standard on windows opens it. Tried Word, Excell, Adobe PDF, etc. It betamax inst it...

You still use Windows? Quaint. .ODS is from free open source progs like Open Office or Libre Office. They both open just about everything. You just don't have to pay Gates ridiculous prices, or pirate his stuff.

Yes I saw that open source office clone. Looks like a 10 year old Microsoft program...

And I never actually bought any Microsoft software in my life!

Thing is, the world uses word, excel, and PDF files. They cannot necessarily open some obscure programs special unknown file type! Thats why betamax failed. 3 in every town.

Cant that program save as a word .doc or rich text file .rtf or even as a pdf file? Then normal users with modern industry standard software don't need to go through contortions to try and read it.

EG In MS Office, word, I can save as:

Thats all hyroglyphics!

Been looking at those cells. That chemistry is pretty low energy density, akin to lead. So no real gain.

ex-Gooserider wrote:
I'm attaching the ODS (Libre-Office) spreadsheet that I made with the vendors I checked... No promises that anyone else would get the same prices, but at least it's a starting point... As usual, rename the file by changing .zip to .ods

bat-conv-price.zip

ex-Gooserider

Good info, Goose.

I just removed the .zip extension and added the .xls extension and Excel was able to open the spreadsheet. It gave some sort of error at first, which I told it to ignore, and then opened the file just fine.

My excel wont open it. It just looks offended.

The core of Rachele's speech output computer is a nearly 10,000 line set of PerfectScript macros and what she sees on screen is several hundred tables in a WordPerfect document. I challenge any Word expert (or OpenOffice expert for that matter) to reproduce even 10% of what we've been able to do with WordPerfect - and I'll even give you a copy of the source code to help you get started. My guess is that just trying to create two different-sized tables on successive pages, then edit the first one without screwing up the second, will prove to be a disaster.

Burgerman wrote:My excel wont open it. It just looks offended.

I'm using Office 2016. Excel wasn't happy but it opened it.

Save as a proper office document, or PDF, and post it to burgerman@ntlworld.com if its easy. If not don't worry.

Try opening this Excel sheet in Office 2016 BM, I used LibreOffice to convert it. Remove the zip extension to open it.

Steve

Yes I did it on my laptop. Made a few complaints and then opened it.

Burgerman wrote:What is a .ods???

Nothing industry standard on windows opens it. Tried Word, Excell, Adobe PDF, etc. It betamax inst it...

Windows doesn't even follow it's OWN industry standard (which it bought in direct contradiction of ISO's stated procedures)

OTOH, ODS is the ISO COMPLIANT subset of the Open Document Format, as properly registered and approved by ISO in compliance with it's stated procedures - it IS fully documented, with reference implementation, and is totally available for any program to implement that chooses to... If Microsoft doesn't open it, it is because Microsoft doesn't want to implement it....

Libre Office, which is a fork of Open Office created to maintain independence from Sun / Oracle, was what created it. Libre Office can read and write a far longer list of files than that pathetically short one shown by Windows - including all the older Word formats that the current Word will NOT open without installing extra software.... However I don't do proprietary formats....

ex-Gooserider

Getting back on topic.... I've been going through the long conversion thread (now up to Pg 22, Nov 2014) trying to make sure I have the details on the build right, and also find the connector that BM is currently using to do all the charger connections in one plug.... I'm ending up with some questions:

1. In different threads BM says BOTH that it is OK to do the initial charge to get all the cells full before putting them aside to sit while self discharging to do the matching process in parallel, and elsewhere that it has to be done one at a time... Which is it????

2. While BM says that it is OK to put the cells aside at full charge, it is better to discharge by a few Ah - can THIS be done in parallel or is it done individually?

In other words, my understanding of the steps is:

1. Charge to 3.6V and soak for 30 minutes after 'full' - can this be done in parallel or does it need to be done individually?

2. Optional, but preferred - discharge each cell by 3Ah - can this be done in parallel or does it need to be done individually?

3. Let sit for as long as possible, min 2 weeks, 1 month better.

4. Charge each cell back up individually, and record how much returned - use these numbers to build pack.

---------------

Next - can someone point me to where that Sub-D connector with the pins for both charging and balancing is? I want to get some part numbers so I can order some....

---------------

Last (For now) - the way the batteries load into an H-frame chair is that the first box slides into the frame on rails and plugs automatically into an SB-50 on the frame, then the second box slides in behind it and connects the same way to the first. The SB-50's are mounted on brackets with guide pins that force them into alignment as they get close, which allows the blind mating to work.

It looks to me like the best way to deal with the balance wires is to modify the boxes to add another set of blind mating connectors alongside the existing SB-50's and have everything mate that way. Neat, keeps the harnesses as short as can be, and doesn't add extra wiring that has to be routed around the rest of the chair hardware when putting the boxes in and out... (there would be a short harness from the box connector on the frame to the outside for the charger plug, but this would be 'permanently' mounted...)

I am currently looking at the MOLEX brand Micro-Fit or Mini-Fit 'BMI' connector series that are supposed to be designed for blind mating, does anyone have any thoughts about other alternatives?

Another possible issue is that the wiring to the rear box batteries will be about 10" longer than the wiring to the front box, and have an extra set of connector pins... If necessary, I could add extra wiring and a connector set in the front box to make it match the rear box, but that would be a bit of a nuisance - how critical is it that the balance wiring to all the cells be exactly the same length???

ex-Gooserider

1. In different threads BM says BOTH that it is OK to do the initial charge to get all the cells full before putting them aside to sit while self discharging to do the matching process in parallel, and elsewhere that it has to be done one at a time... Which is it????

As long as a low termination point in mA is set, so they soak at cv for a long time its OK to charge in parallel. Since they will all end up 100% full. Because natural full voltage is around 3.45v.

2. While BM says that it is OK to put the cells aside at full charge, it is better to discharge by a few Ah - can THIS be done in parallel or is it done individually?

Individually, because the state of charge cannot accurately be determined by voltage. So more may come out of some cells than others.

how critical is it that the balance wiring to all the cells be exactly the same length???

On the Hyperion its more important because its balance current is digital, and 250mA. And shorter is better. Less important on the pl8 as its proportional, and 1000mA. It will end up balanced regardless, its just time...

I gave all mine their initial charge individually.

Good question on the balance wiring length. I had been wondering the same.

https://www.digikey.com/product-detail/en/norcomp-inc/680S17W2103L201/NOR1218-ND/4146273

https://www.digikey.com/product-detail/en/norcomp-inc/680M17W2203L401/NOR1282-ND/4311798

https://www.digikey.com/product-detail/en/assmann-wsw-components/A-FT-25/AE11004-ND/1241836

These are the ones I used. Don't go looking for cheaper and order extras. Saving $5 is not worth redoing it when the connectors pull out or snap off. You could use the same ones with less terminals for easier connection. I needed all of them for my 14S pack. I ordered several different covers. Those I linked were by far the easiest to do and worked fine.

Don't worry too much about the wire length being exact as long as they're within one foot or so in length of each other. That won't make .001v difference. The quality of your soldering and connector impedance will make more of a difference.

1. Charge each cell to 3.6v. You can do that in parallel groups of five or so. Leave soaking on CV for 30ish minutes after the CC stage ends to make sure they're full.

2. Let them sit for a few weeks.

3. Charge each one INDIVIDUALLY and record the mAh returned.

4. Assemble them in parallel groups that AVERAGE the same.

Now, that's the way to build the best balanced pack possible with the cells you have. That's a lot of trouble. Also, lithium cells don't like to be stored full. One could argue that storing them full for weeks will affect them as much as the parallel groups not being perfectly matched. I haven't tested it nor know of anyone who has. I certainly wouldn't skip this step using questionable quality or used cells.

I've done step one, assembled the pack, discharged some for storage until needed, then used. I don't ever get low enough to even possibly over discharge one and they all top balance to 3.55v in under an hour. And I'm using a charger with a much punier balance circuit than the PL8. Use your best judgement.

Williamclark77 wrote:https://www.digikey.com/product-detail/en/norcomp-inc/680S17W2103L201/NOR1218-ND/4146273

https://www.digikey.com/product-detail/en/norcomp-inc/680M17W2203L401/NOR1282-ND/4311798

https://www.digikey.com/product-detail/en/assmann-wsw-components/A-FT-25/AE11004-ND/1241836

These are the ones I used.

Same here. Feels real solid.

Williamclark77 wrote:Also, lithium cells don't like to be stored full. One could argue that storing them full for weeks will affect them as much as the parallel groups not being perfectly matched.

After charging my cells, grouping them by static discharge level, and assembling my pack, I haven't been able get the pack in my chair as fast as I had hoped. So my pack has been sitting there full for a few weeks.

Should I bleed some power out of it?

I should have the pack installed in my chair within two weeks. I have to wait for my buddy to come over and give me a hand. Its not easy getting to my battery area - the seat has to be taken off etc.

Yes. About a third of its Ah.

Yes. About a third of its Ah.

Burgerman wrote:Yes. About a third of its Ah.

Will do. Did I do any damage?

Doubt it. Think of it like a person holding his breath ready to blow up a big balloon. Full lungs about to burst, not comfortable! Empty lungs, not comfortable. Lithium's prefer to be around 30 to 70% full. Then they last longer.

https://www.victronenergy.com/blog/2015 ... on-vs-agm/ not directly related but a good read.

Ok. I'll bleed it for an ~hr with my 24v 25A dump load tomorrow.

Can't wait to get this pack in my chair. The weather is getting nice, and I took a 10mi stroll the other day using the lead bricks I had installed last summer. BARELY made it home.

Minor update - according to the UPS site, my cells should be arriving tomorrow by the end of the day....

Took a bit longer than I was expecting, but not terribly so.

Now I need to start working on a charging setup - I want to make a jig to clamp the batteries in, rather than doing screw connections on each one...

Seems especially needed for the initial charge step where one can do several in parallel...

ex-Gooserider