PINNED - Lithium battery conversion/info

[Gnomatic]

expresso, what kind of dumb charger were you using to charge your add-on pack when you still had the BMS connected to it?

[Burgerman]

A CC/CV of x amps and 28v would be OK. In other words an 8A 28v power supply would liKely work best with a BMS. As its low enough volts that it will help to keep the bms from bouncing a cell high over and over.

[expresso]

expresso, what kind of dumb charger were you using to charge your add-on pack when you still had the BMS connected to it?

i was only using the standard generic black box chargers they give out when you get a new chair - 8A - specs show it at 28.8V - give or take - what it actually does is another story - i only used the BMS this way for a few weeks -

i believe someone here found a smaller charger which does GEL at the correct Volts - the only real charger i have now at home which can do both adjustable is the Salmex Marine charger - with a SB50 end on it - besides the PL 8 i use for lithium and a few black box types they give out - - one Lester big box old school which i use on my indoor chair only - leave it in one spot where i keep it parked in my room for that chair only -

[Gnomatic]

I really like this idea for a temporary travel charge setup.

Anyone have a suggestion or a link to a decent BMS for this application?

[Burgerman]

[expresso]

I really like this idea for a temporary travel charge setup.

Anyone have a suggestion or a link to a decent BMS for this application?

yes this would solve having to carry anything - just your normal dumb charger which you can keep where your going also - if its a family or friends place -
still carry your own - just in case

i never though of it that way - i like to do that just because i have a BMS now doing nothing - but it would be a overnight charge if your planning on fully charging your chair -

either way its something - an option

[ex-Gooserider]

Thanks for the photos Gnomatic... Bad news is that it looks like I can't get away with the 96A approach after all.. As best I can make out your measurement photo, 6 cell blocks are 9 15/16" tall, = 252mm. This works out to 42mm / block, or 2mm / block less than what Evassemble gives for block size when assembled... The second picture looks to be 13.25" which works out to 42.0625mm, or about the same. So I'm right in that stacked blocks come out slightly smaller, but not enough to help...

Measuring my box with a steel engineering rule, I get 243mm or a little over 9 9/16" So it looks like I'm about 9mm or 3/8" to short... I get the same sort of results if I calculate in terms of blocks - 243/44 is only 5.523 blocks, or with the new number, 243/42 = 5.79 blocks....

While Expresso's idea of a battery tray is interesting, I think I'd rather stick with the boxes, as they fully enclose the batteries and don't lead to other potential complications like reduced ground clearances or difficulty fitting lock-down bolts for my van. Also if I were to ever want to fly with the chair, having the packs in the stock factory boxes would probably cause fewer questions than an exposed pack would.

I definitely like Shirley's idea of using a dump charger with a BMS as a separate unit, as that at least partly solves both issues, keeping the package size reasonable, and not actually putting the BMS in the chair... Given the reports that Evassemble gets sticky about warranty issues if one doesn't get a BMS, it might make them happier as well if I ever do have problems with the pack....

So this leaves me with the question of whether or not the 15Ah 4s6p pack would fit...

The 15Ah cells are 152mm long, they don't give dimensions in the blocks, but assuming the same 32mm addition that we have for the smaller cells, I get 184mm, which should be no problem for height, even in the area of the Anderson slots which are 224mm.

So looking at length and width... The box has a definite taper, so the bottom dimension is critical. Measuring the inside bottom of a box is actually a bit of a challenge as there aren't a lot of tools that will work for that. However I've found 2-3 approaches that agree on 173mm W x 263mm L. Evassemble gives the size of the 15Ah holder as 85x43mm. Given the numbers I found above on the smaller holder, the assembled holders may be smaller, but going with the given 43mm size, I get 4 x 43 = 172mm and 6 x 43 = 258mm, so there should be no fitting problems...

So all that remains is to figure out the optimal way to do the pack arrangement, which probably isn't that critical other than figuring out what bus bars to order....

ex-Gooserider

[shirley_hkg]

....

So this leaves me with the question of whether or not the 15Ah 4s6p pack would fit...

...

ex-Gooserider

If it does , 4S7P will also fits .

The fifth row has only 3 cells , that they can be arranged on both sides , so still leave you a centre void for Anderson .

[expresso]

using the stock boxes does make it harder - but if you can get it done that way - its nice to have them closed in a box -

have you considered buying just the orange blocks for the 15ah cells - get enough use them to figure out if it really fits etc, maybe worth it - and maybe you can reuse them if it works out -

i have to say its very hard to unsnap them once snapped in place - maybe get a few cells to use as a guide - to get the correct height with the cell in place

one cell on one corner of each pack - making two 12 volt packs - get 4 cells - two for each - you know - i have some loose cells sitting discharging before i make another ADD ON - i will get one with the block in place and measure it for you - so you can see the height with the block in place on both ends -

i will try to get it done tomorrow if i can - and measure - take a pic and post it -

[Gnomatic]

Thanks for the photos Gnomatic... Bad news is that it looks like I can't get away with the 96A approach after all.. As best I can make out your measurement photo, 6 cell blocks are 9 15/16" tall, = 252mm. This works out to 42mm / block, or 2mm / block less than what Evassemble gives for block size when assembled... The second picture looks to be 13.25" which works out to 42.0625mm, or about the same. So I'm right in that stacked blocks come out slightly smaller, but not enough to help...

Measuring my box with a steel engineering rule, I get 243mm or a little over 9 9/16" So it looks like I'm about 9mm or 3/8" to short... I get the same sort of results if I calculate in terms of blocks - 243/44 is only 5.523 blocks, or with the new number, 243/42 = 5.79 blocks....

Goose, I think you might be looking at that wrong. My X5 has two separate battery compartments.(my V6 has one big one)

If/when I convert my X5 to lithium, if I'm shooting for a 90Ahr pk, I won't have the cells aligned horizontally and orange blocks stacked vertically.(if using 15Aht Headways) Rather, I'll have one 4 X 6 layer of orange blocks on the bottom (L x W) of each battery box, and another on top. With 24 15Ahr cells aligned vertically. Would fit in every Group 24 chair I've owned. From an Invacare Arrow to OmegaTreac to my current V6.

[expresso]

these are your pictures Genomatic - 90ah in the chair -

outside is the 4x6 -
the height will fit for sure - its shorter on height than a group 24

[Gnomatic]

Yes.

[ex-Gooserider]

Shirley, the 4s7p pack using the 12Ah cells arranged horizontally is one of the two packs that BM has on his conversion page http://www.wheelchairdriver.com/converting-to-lithium.htm It would fit, but is only 84Ah... Going to a 4s6p pack using 15Ah cells arranged vertically will also fit, and is 90Ah.

I had been thinking of a 4s8p pack, of 12Ah cells but that appears to be to tall by about half a cell diameter.

As a reminder - the BCI specs for Group 24 and 34 - note that they are the same except for height....
L W H L W H
Group 34 (50Ah to 70Ah) 260 173 200 10 1/4 6 13/16 7 7/8
Group 24 (65Ah to 75Ah) 260 173 225 10 1/4 6 13/16 8 7/8

Whatever we use for a pack, it has to fit in the existing battery space, which is probably going to be one of the BCI size specs, as the chair makers don't really like wasting space....

When we go to convert, we have to fit within all three dimensions. As it turns out, width is relatively easy, EITHER 4 15Ah cells arranged vertically OR a 12Ah cell horizontally is 172mm, which is just about a perfect fit... Length is more of a problem, but not that bad; 6 cells in either size fits reasonably well - 258mm for the 15Ah, or 240mm for the 12Ah.

The BIG problem is height... BM's suggested 36 12Ah cell, 4s9p replacement for Group 24 is a 6x6 pack, and 6 12Ah cells is 240mm, TALLER than the spec for a Group 24... (I'd note that the height of my Invacare boxes is within the Group 24 limits)

The 4s7p version would be 200mm on the ends, and 160mm in the center, which meets the Group 34 size limits, but only gives 84AH, which isn't all that much more than a pair of Group 24 bricks...

I'm not sure of the exact length, but it will be on the close order of 185mm, which is shorter than the Group 34 pack, but a 4x6P pack of 15Ah cells is 90Ah, which is more than the 84Ah of the 4s7P 12Ah alternative....

ex-Gooserider

[expresso]

when i did mines - i felt the same way - couldnt be sure with the 12ah cells etc, - to be sure i purchased the 12ah blocks - put them together as if i was making the pack and then went to put it in my chair to see if it fits - and it was too tall for my chair - with my divider on top for the controls for tilt and seat lift etc, -

i knew for my chair - at least with out having to do major modifications to try to make it fit - it didnt on its own - - then going to 15ah - it fitted with room to spare for a 90ah pack - i then added another row on top to get 105ah and that was just right - actually even a hair lower than the group 24 battery -

remember you want to add the posts on the battery also - if you havnt - the posts are about 1 1/2 inches sticking up - if you are not sure - consider getting the blocks and doing a dry run - get some 12ah blocks and some 15ah blocks -

[ex-Gooserider]

I will need to crunch some more numbers, but while I'm certain the 4x6 pack will fit, I don't know for certain about the idea of adding another row on top... However that is a good idea if they will fit, along with the wiring...

Another challenge that I may need to figure out is how best to do the balance / charge connectors... The 'perfect' solution on paper would be to modify the boxes and lids to have balance connectors that auto-magically connected like the existing Andersons when you slide the boxes into the frame...

The other option would have to be to put connectors in the lids and have a harness that plugged into the boxes after sliding them in. This might be a challenge as there are some fairly tight areas above the boxes, not to mention accessing the tops to plug them in.

However a brief chat with one of the engineers here says they make connectors that will do the automatic plug in so it might not be hard to get the perfect solution...

ex-Gooserider

[shirley_hkg]

....

So this leaves me with the question of whether or not the 15Ah 4s6p pack would fit...

...

ex-Gooserider

If it does , 4S7P will also fits .

The fifth row has only 3 cells , that they can be arranged on both sides , so still leave you a centre void for Anderson .

I am talking about 40152 cells of 105Ah .

[shirley_hkg]

Actually , we are fitting two 4s9p @135Ah slabs into an ARROW last weekend , that need a bespoke battery box ..

[ex-Gooserider]

Actually , we are fitting two 4s9p @135Ah slabs into an ARROW last weekend , that need a bespoke battery box ..

How are you managing THAT Or are we calling two different chairs 'Arrows' - The one I have is a "Storm" Arrow, using the same H-Frame as the Torque and Ranger-X - RWD (though I think there may be an FWD variant on one of them) with two straight aluminum extrusions, one on each side, with the caster barrels on one end, and a cross beam in the middle tying them together... The Group 24 battery box models have two boxes that slide in the back on rails, and connect to the chair frame and each other with guided Anderson SB-50's...

I don't see any way to fit a bigger box without increasing seat height, lowering ground clearance, or hanging out the back end of the chair (or more than one of these)... Given the way the boxes are fairly precise fits onto the rails, and have to support the full weight of the batteries, I know that I'd be hesitant to try to duplicate them with the tools I have access to....

ex-Gooserider

[ex-Gooserider]

OK, just did some drawing in LibreCAD, using some crude generalizations...

IF, and it's a BIG IF... My assumptions are correct, then the 4p, 6s pack of 15Ah Headways vertically will fit, no problems... I WILL have a problem adding the Horizontal row of 4 additional cells (to make it a 4p7s pack) on top...

Here is a .jpg of the drawing - the native .dxf file is available on request, but I can't upload it because the board won't take it...

The dimensions of the battery box itself are as precise as I can get - and taken multiple ways that all agree with each other... They are of the bottom inside of the box, which is tapered so it is slightly larger on top (which is NOT in this version of the drawing)

Between Gnomatic's photos, and the specs on the evassemble site, I'm using 42.5mm as the dimension on the blocks... I feel sure that this number is good enough to work with reliably,
and one can see plenty of extra space on the ends and sides of the vertical part of the pack, so I don't see an issue there...

What I am NOT certain of is the exact LENGTH of the 15Ah cells when in blocks.... For this drawing, I assumed 185mm, based on the extra added by the blocks to the smaller cells and an extra 1mm 'fudge' factor.... The result is that when I add the horizontal set of cells on top, I get 42.5 + 185 = 227.5mm, which is sticking 3.5mm into my "no battery zone"

This is where the Anderson connectors go, fitting into the notch you can see in the center top of the side view - I checked they use ALL of that space, there is less than 1mm between the connector and the notch bottom when the lid is on the box...

The cells are slightly smaller than the blocks, and the area over the notch is a cell area, but that only gets me about 1mm. I don't know if it is practical / possible / safe to put the top blocks in between the posts of the vertical ones, or mill a bit off the bottom vertical blocks (the boxes are a presumably non-conductive plastic material) to make up the extra space, or if my assumption about the height is wrong....

I need an exact number for the height to see if I can make it work at all...

ex-Gooserider

[Burgerman]

Since you can only use 45Ah at best from a typical 70Ah lead brick, a 90Ah lithium will still double your range.
If its a brushless chair like my new trick seat one, that already gets a 40% boost on range, that gives you about 60 to 75 miles. So I wouldn't worry too much if you cant get the top row of 15Ah in. I cant either.

[Gnomatic]

What I am NOT certain of is the exact LENGTH of the 15Ah cells when in blocks....

This pic of expresso's pack should give you good idea of the length of the cells in the blocks

[expresso]

i was just going to look for that picture - thanks Gnomatic

with the top row its right about 9 inches total it seems in this picture and i can say it was a bit shorter than the MK Gel i took out of the chair - its a perfect fit - like BM said without the top row - its plenty room then with 90ah pack - and unless your doing 30 miles each day with it - wont be a big deal anyway - 30 miles is alot of riding around -

[ex-Gooserider]

Unfortunately, that picture wasn't terribly useful as it didn't have the precision I needed... There is an inherent accuracy issue with tape measures as well, because of the 'slop' in the way the hook attaches to the tape - in theory this is supposed to allow for the difference in the thickness of the hook when going from inside to outside measurements, but it makes for an accuracy question when trying to get into the less than 1mm or 1/16" range... In addition it wasn't clear just where on the tape the corner of the block ended up...

(I will a tape measure for carpentry, but for precision, I use a steel rule, caliper, micrometer, or other similar tools...)

As an example, I used ALL of the following tricks when measuring the inside of the battery box -
1. Tape measure with the 'add x for inside measure' - not very good...
2. A 'story stick' - I used a couple sections of a broken telescoping pickup stick to adjust to an exact fit, then measured the stick with a steel rule.
3. A laser 'tape measure' (it's minimum distance was about 150mm, I was a little surprised when it worked)

However I have lucked out a bit... I started searching to see if I could find another site with more info than evassemble. I found a really nice picture at http://headway-cn.com/en/showproducts.php?id=1775 - the sort of dimensioned drawing I wish the other sites had as well... Surprisingly though, it was using mostly inch measurements. I downloaded the picture, and went in with a photo editor and added metric values that I got using the 'Convert-Me.com' website http://www.convert-me.com/en/ - IMHO the best site I've ever found for doing measurement conversions....

Here is the edited photo -

ENGLISH [METRIC]

Bad news is that the cells in blocks are longer than I'd guessed, so I almost certainly can't do the top row However as BM has pointed out, 90Ah of usable power is still nothing to complain about....

ex-Gooserider

[woodygb]

I have this little utility pinned to the bottom of my screen.
https://joshmadison.com/convert-for-windows/

[expresso]

90ah was what i was going to do if mines didnt fit either - can always hang a ADD ON - to extend that - if you have 9 1/2 inches clearance - it should fit with the top row also - thats the same size of a group 24 with top posts - MK battery

but you would have more room for wiring etc, if you did 90ah - my chair is good for 30 miles with some to spare with 90ah - with 105ah - i get 40 easy with some to spare - thats my chair - my riding style etc, - but it wont be far off i dont think

if you really really want to make 100% sure - what i did - i just purchased some 12ah block when i was testing it for the 12ah cells - thats what made me not do 12ah cells - didnt fit in my chair the way it was suppose to -

purchase some 15ah blocks and a few 15ah Cells from the USA headway website - and do a dry run with them - thats the only way you can know for sure %100 - i was told over and over that the 12ah cells would fit - and they should have maybe - but they didnt in my chair -

not going to waste time trying to figure out why or this or that - 15ah worked out great - fitted and easy - the 90ah pack was just one large flat pack - easy - in your case you would have two parts - - its those boxes you have to be sure how it fits in there -

i would buy some 15ah blocks and few cells to test it - once you see its fine - then you can order the rest from China -

[Burgerman]

I have this little utility pinned to the bottom of my screen.
https://joshmadison.com/convert-for-windows/

And here...

[Gnomatic]

Here is the edited photo -

hedwy-40152S-blk.jpg

Headway Headquarters used to have that photo on their website, but .....

purchase some 15ah blocks and a few 15ah Cells from the USA headway website -

Not going to work. Headway Headquarters is now wholesale only.

Lithium LiFePO4 Cells by Headway and CALiB

We are moving away from retail and concentrating primarily on wholesale for cells which is the reason for the change up occurring on our website. Our MOQ is 500 pieces for wholesale pricing. We apologize if this has caused any inconveniences. We can direct you to a reputable seller in China if you would like, the costs for the cells will be much lower, yet you will find that with the shipping costs the overall end costs will be very much the same as when purchasing from us.

[expresso]

Here is the edited photo -

hedwy-40152S-blk.jpg

Headway Headquarters used to have that photo on their website, but .....

purchase some 15ah blocks and a few 15ah Cells from the USA headway website -

Not going to work. Headway Headquarters is now wholesale only.

Lithium LiFePO4 Cells by Headway and CALiB

We are moving away from retail and concentrating primarily on wholesale for cells which is the reason for the change up occurring on our website. Our MOQ is 500 pieces for wholesale pricing. We apologize if this has caused any inconveniences. We can direct you to a reputable seller in China if you would like, the costs for the cells will be much lower, yet you will find that with the shipping costs the overall end costs will be very much the same as when purchasing from us.

OH that sucks - i mean they were expensive compared to china but for a quick fast order when you need it - i have used them before - so that leaves us with no one here in the states to buy them now ?

[Gnomatic]

OH that sucks - i mean they were expensive compared to china but for a quick fast order when you need it - i have used them before - so that leaves us with no one here in the states to buy them now ?

Yeah that does kinda suck. When considering cells and arrangement for my chair I purchased some orange blocks from HH, then once I knew what would fit I placed the big order from EVASS.

To get just a sample of 24 orange block from EVASS delivered here to the states will cost near $40.

[Burgerman]

Odd that a place as big as the US doesn't have other sellers?

UK you can get them in electric bike shops, or online from a few places. Like http://eclipsebikes.com/battery-cells-b ... f3c25f4c02

Italy http://www.greenbikekit.com/lithium-bat ... fepo4.html

There are others. And eBay sometimes shows a few sellers in france and germany.