PINNED - Lithium battery conversion/info

[JoeP]

(Posted above while I was typing)

Do you mean BCI Group 24 which has nominal dimensions of L= 10.5", W=6.75", H=8.75" as compared to
22NF size with dimensions L=9.04", W=5.45", H=8.15"
Sometimes the equipment has a bit of wiggle room but that can only be told by examination & measurement.

Yes. As you say, I think only a manual measurement will give the answer.

[Burgerman]

Comparison of USABLE energy in watt hours of various batteries based on a continuous drive.

Typical 22nf chair has 15 mile claimed range, so about 6mph x 2.5 hours.
MK 22nf 51Ah (32Ah@ 2.5 HOUR RATE) X 24V = 762 watt hours to 100% dead, (which we cant achieve in a wheelchair as it stops long before this!)
609 watt hours @ 80% discharge is typical.

MK's 2.5 HOUR DISCHARGE RATE FIGURES
MK GRP 22nf 609 watt hours
MK GRP 24 864 watt hours

LITHIUM.
BM3's 72Ah 45V lithium has 3240 watt hours
BM2's 120Ah 25.6v lithium has 3072 watt hours
Expressos 105Ah 25.6V lithium has 2688 watt hours
Nandols 190Ah 25.6V lithium thats stuck in hong kong has 4864 watt hours.

COMPARED TO GRP 24 73Ah
BM2 has 3.55 times more!
BM3 has 3.75 times more!
Expressos has 3.1 times more!
Nandols has 5.6 times more!

COMPARED TO GRP 22nf 51Ah
BM2 has 5.04 times more!
BM3 has 5.32 times more!
Expressos has 4.4 times!
Nandols has 7.9 times more!

[expresso]

Hi - Joe - this is the utility Cart i used for charging - i wheel to the chair and connect everything - laptop etc, - Power the PSU - Charger first before connecting it to the pack -

[JoeP]

I just had my backup chair's battery box measured. My back-up chair is also a TDX-SP.
Unlike my primary chair, the backup chair has no elevation post so the battery space is unobstructed.
As measured, the open area available for batteries is:
9 5/8" wide x 15" deep x 9.75" high, or in metric:
244.475mm wide x 381mm deep x 246.65mm high

Shirley you were on the mark. It appears I might be able to get two '6x6' packs each 4S 9P (12Ah) packs into that space. That would yield 24 Volts at 108Ah.
So it looks like a full scale TDX-SP build might be possible even with a narrow base (24 inch).

But it would be a tight fit. The clearances should be as follows:
7.6 mm at the top of the pack (247.6 - 240)
4.475mm for the width of the pack (381 - 348)
33mm for the length of the pack (381 - 348)

Are these clearances to tight?

I am posting some sketch up images of what I think a 8S 9P battery pack should look like (if I have learned my burgerman lessons well). The numbered green circles indicate where I think the nine balance cables should be attached.

Any thoughts?

Joe

[JoeP]

#!@%, I can't figure out how to attach the images! I get the message: "The file is too big, maximum allowed size is 256 KiB."
I guess I'll have to figure out how to reduce the size of the files.

[expresso]

#!@%, I can't figure out how to attach the images! I get the message: "The file is too big, maximum allowed size is 256 KiB."
I guess I'll have to figure out how to reduce the size of the files.

use the software Paint on your computer - open the file - right click on it - Edit and use on top resize - i usually end up changing those number you see in the boxes - to about 50 - then save it - and check the size again - if still too large

repeat the steps and resize another 10 off - it will say 100% - put in 90 and save again - check the size - - once you get the right size - then you can upload it -

[JoeP]

I just had my backup chair's battery box measured. My back-up chair is also a TDX-SP.
Unlike my primary chair, the backup chair has no elevation post so the battery space is unobstructed.
As measured, the open area available for batteries is:
9 5/8" wide x 15" deep x 9.75" high, or in metric:
244.475mm wide x 381mm deep x 246.65mm high

Shirley you were on the mark. It appears I might be able to get two '6x6' packs each 4S 9P (12Ah) packs into that space. That would yield 24 Volts at 108Ah.
So it looks like a full scale TDX-SP build might be possible even with a narrow base (24 inch).

But it would be a tight fit. The clearances should be as follows:
7.6 mm at the top of the pack (247.6 - 240)
4.475mm for the width of the pack (381 - 348)
33mm for the length of the pack (381 - 348)

Are these clearances to tight?

I am posting some sketch up images of what I think a 8S 9P battery pack should look like (if I have learned my burgerman lessons well). The numbered green circles indicate where I think the nine balance cables should be attached.

Any thoughts?

Joe

[JoeP]

#!@%, I can't figure out how to attach the images! I get the message: "The file is too big, maximum allowed size is 256 KiB."
I guess I'll have to figure out how to reduce the size of the files.

use the software Paint on your computer - open the file - right click on it - Edit and use on top resize - i usually end up changing those number you see in the boxes - to about 50 - then save it - and check the size again - if still too large

repeat the steps and resize another 10 off - it will say 100% - put in 90 and save again - check the size - - once you get the right size - then you can upload it -

Thanks Claudio.
Some how I got a duplicate of the back of the battery packs in there.
Joe

[Burgerman]

Are these clearances to tight?

My battery is 174 wide, sits in a 173mm space. So 0mm spare... Designed that way.
Its 240mm tall, and has 5mm spare to route cables. (And on my BM2 has several raised sections (280 tall) that miss the seat plate by 3mm. And a lower section to miss the power module.
Its 13 cells long (thats 40mm x 13 = 520mm) and I have 520mm exactly.

So no its going to rattle around!

[JoeP]

Are these clearances to tight?

My battery is 174 wide, sits in a 173mm space. So 0mm spare... Designed that way.
Its 240mm tall, and has 5mm spare to route cables. (And on my BM2 has several raised sections (280 tall) that miss the seat plate by 3mm. And a lower section to miss the power module.
Its 13 cells long (thats 40mm x 13 = 520mm) and I have 520mm exactly.

So no its going to rattle around!

Okay, that gives me some confidence!

Just ordered these from Revolectrix's US store:
1 -FUIM3 USB Interface Module for 2-way data communication.
1 - Cellpro PowerLab, Stackable, 40A Safety Banana Plug Cable
1 - Cellpro PowerLab 8 v2 with EC5 input cable, 1344W, Multichemistry Battery Workstation
2 - PowerLab 36" Extension Cables
Total $284.75
***********
Also ordered this Power Supply Unit on EBay:
"Juice Box" by StricklandProducts
24 Volt DC 75 AMP 1800 Watt for Charger, Black Carbon Fiber ( 222038775717 )
EBay: $98 and free shipping.
(Looks very similar to the UK's"CoolIce")
***********
Ordered from EBay:
300 BLACK SOCKET HEAD COVER CAPS - For Headway LiFePO4 Cell 4mm hex screw <http://www.ebay.com/itm/182087848890?_trksid=p2057872.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT>

Before I go ordering 74 headway 12Ah cells I think I should order just eight cells and make sure I can figure out that PL8. From what I've read, figuring out how to do the settings looks pretty difficult.

Joe P

[Burgerman]

No its easy. I will post you a preset. Plug and play.

You really wanted m6 short button head bolts in stainless. Rust isnt pretty and the cells have stainless ends.

[JoeP]

No its easy. I will post you a preset. Plug and play.

You really wanted m6 short button head bolts in stainless. Rust isnt pretty and the cells have stainless ends.

The short ones are 10mm long?

[curiouscat]

No its easy. I will post you a preset. Plug and play.

I realise you can program for one or the other but is the preset you mention for a slow charge up to completion or a fast top up? Reading that lithium doesn't like to be empty or full which is better for battery life?

[Burgerman]

Can send half a dozen. Depends what you are doing and why. And capacity etc.

Or you can go through 101 settings on here and tell me what you want to charge or discharge and I can tell you what to choose and for every parameter and why. Then you will know!

[curiouscat]

Can send half a dozen. Depends what you are doing and why. And capacity etc.

A 24v, 72Ah lithium battery, lead replacement. May be higher capacity once I've measured but trying to work out what my charging routine would be if I switched. I know it wouldn't need to be charged as often but does it need an overnight charge or is it fine to just top up over a few hours? Again I know I can do both but I mean which is better for the battery? I would prefer to charge during the day so I don't have to rely on someone else to do it correctly at night. Also more convenient for cell monitoring.

[Burgerman]

If you only fit 72Ah it will need charging regularly. You lose some of the range and longevity advantage. Because you will work the cells hard, discharge more deeply, recharge more often. Best fit more if possible.

With a 40A charger you can put back exactly 40Ah in 1 hour. Or 60Ah in 1.5 Hours. Or a full charge from dead in under 2 hours. You do not need a full charge. The battery doesent mind. But you must do a full charge once a month in order to rebalance cells.

[curiouscat]

If you only fit 72Ah it will need charging regularly. You lose some of the range and longevity advantage. Because you will work the cells hard, discharge more deeply, recharge more often. Best fit more if possible.

With a 40A charger you can put back exactly 40Ah in 1 hour. Or 60Ah in 1.5 Hours. Or a full charge from dead in under 2 hours. You do not need a full charge. The battery doesent mind. But you must do a full charge once a month in order to rebalance cells.

Thanks. I know if more won't fit it's not worth doing, will see.

[Burgerman]

It willstill be better than lead. But best to fit more!

[Jason12]

If I wanted to buy a readymade battery pack http://www.evassemble.com/index.php?mai ... ex&cPath=1 which one is suitable?

Cheers

[Jason12]

If I wanted to buy a readymade battery pack http://www.evassemble.com/index.php?mai ... ex&cPath=1 which one is suitable?

Cheers

I don't want change anything else just the batteries..

[Burgerman]

Non of those. And there are no ready made packs with built in BMS that are. That's not to say they wont work, in a fashion. But you will lose all the real benefits lithium offers or most of them. And its very likely you will have reliability issues.

viewtopic.php?f=2&t=1813 Read post one carefully!

[Jason12]

Non of those. And there are no ready made packs with built in BMS that are. That's not to say they wont work, in a fashion. But you will lose all the real benefits lithium offers or most of them. And its very likely you will have reliability issues.

viewtopic.php?f=2&t=1813 Read post one carefully!

Thanks

It's like reading Chinese I understand almost none of it

[Burgerman]

Well look at it like this. There isn't a plug and play solution that's any good. That's not to say that there are not some batteries and simple chargers that can work because there are.

But they don't maximize capacity, and that's the key to great range, great service life etc. That is everything. Because lithium hates being worked hard. They can do it fine. But they don't last as long. So your expensive battery doesn't give the range it could, and wears out fast.

And they use a generic BMS which is a circuit board designed to protect the cells from abuse that kills them. The trouble is that these are frankly junk, because the way they work during charge is both fundamentally the wrong way to do it, and liable to early battery or cell death. And the other things they do, shouldn't actually be required if the pack is big enough, of high enough C rate for the job and the chairs control system is current limiting etc which they are. The third thing BMS do it cause fires like the recalled laptops, phones, the Boeing Dreamliner lithium fire, etc. So we don't need one! Instead we maximize capacity, and then use a very advanced super accurate cell balancing charger.

[JoeP]

Hi all,

I've started assembling materials for converting my TDX-SP to a LiFePO battery pack.

I did the diagram set out below in SketchUp hoping for forum comments from members much more knowledgeable than myself.

I guess I'd like to use 10AWG most everywhere. But I would use 6 AWG from the battery terminals to the TDX's controller. I realize that the PL8 output cable provided by Revolectrix (the one with the two banana plugs & the 40 A fuses) is only 12 AWG, but I figure using 10AWG elsewhere won't hurt anything. However, I'm wondering whether it is feasible to fit high strand 10AWG wire into that tiny Norcomp Sub-D connector.

Following the BM Anderson SB50 philosophy, I would add an Anderson SB50 to the LiFePO battery which should add some flexibility.

This whole business of crimping vs. soldering vs. crimping and soldering is a confusing subject. Some people like the crimping & soldering method as a "belt & suspender" approach, but exGooserider has pointed out that military engineers demand crimping only on their high-end military specification equipment.

Then there is the issue of pre-tinned wire versus regular wire when crimping.
One smart commentator that I stumbled across, says that if you're doing crimping you should not use pre-tinned wire!
He says that when crimping you get a better connection by not pre-tinning. However, when soldering only, pre-tinned is the way to go. The way he explained it, it seemed to make sense.

According to that commentator, the thinking is that a "crimp only connection" is sometimes preferable because the wire is more flexible at the joint where it meets the connector. He says that using solder takes away the flexibility at the connection point. Apparently, with solder over time a lot of vibration can eventually break the connection. I think I've run across the same observation from some of the senior members on this forum.

I suppose that unless you are doing a lot of off-road cruising in a Frontier V6, the question is academic. Anyway, I would appreciate any and all comments and corrections.

Joe P

[Burgerman]

I'm wondering whether it is feasible to fit high strand 10AWG wire into that tiny Norcomp Sub-D connector.

Wont be easy... And less flexible.

As for crimp v solder thats easy. Its almost impossible to get crimp only connectors with adequate wall thickness/ strength in larger sizes, and so thats always going to be weak. And doing pro quality crimp at home is all but impossible. When you think you are done, I could go around and give every wire a tug and at least some will fall apart, move, or look like they will... And at least some will be high resistance and give funny graphs on the PL8. Have you ever worked on an old car that someone has modified or fitted a alarm system that still works properly without wiggling wires about or problems?

[JoeP]

I'm wondering whether it is feasible to fit high strand 10AWG wire into that tiny Norcomp Sub-D connector.

Wont be easy... And less flexible.

As for crimp v solder thats easy. Its almost impossible to get crimp only connectors with adequate wall thickness/ strength in larger sizes, and so thats always going to be weak. And doing pro quality crimp at home is all but impossible. When you think you are done, I could go around and give every wire a tug and at least some will fall apart, move, or look like they will... And at least some will be high resistance and give funny graphs on the PL8. Have you ever worked on an old car that someone has modified or fitted a alarm system that still works properly without wiggling wires about or problems?

Given my limited hands-on experience it looks like 12AWG and solder are the way to go.
Another question: if you look at that diagram I attached I have3 ring terminals attached to the positive & negative battery poles.
Is that really practical? Would it be better to use one of those many bubars?
as always, many thanx

[Burgerman]

Yes attach to any bus bar bolt.

[ex-Gooserider]

Crimp-only works, and IS possible in the larger wire sizes, but ONLY if one is willing and able to get the expensive high quality crimpers that are needed, and learn how to use them properly... You also have to get good quality connectors, not the cheapos that you find at the dollar store....

In practice a properly made solderless crimp connection will have lower resistance and be more resistant to vibration damage than a soldered one (copper - solder - copper has more resistance than copper-copper if tightly connected) BUT it is also important that one uses appropriate strain relief techniques on ANY connection, soldered or crimped - never have a wire from a connection flopping in space, ALWAYS secure it to something to limit it's movement, or put a connector clamp on it, etc... Any movement or flex (including vibration) should be in the wire, not at the connection point....

Note that standards can be inconsistent - and call for different things! I remember the major headache we had at a former employer where we had to get the power connection for a piece of equipment approved - there were 3 different regulatory standards bodies that had to approve the design, and each had a different standard, along with a test procedure that HAD to be passed, and the standards were mutually incompatible! We had to finally get our engineers to have a meeting between representatives of all three bodies to get them to reach an agreement on what they would buy off on... Ironically the conflicting standards were basically what happens if the conductor was swinging on the connection, with a further spec that the conductor had to be fixed to the cabinet to PREVENT it from swinging on the connection....

IMHO the critical thing is that the wiring be done in a proper and effective way overall, solder & crimp or just crimp is not as critical as that which ever is used is done right, along with the rest of the job.

ex-Gooserider

[JoeP]

Hi ex-Goowsrider,

I used to build houses and I've always been interested in 'best practices'. Somewhere I ran across your comments about military spec & crimping and that stuck in my head. I also used to be something of a tool junkie, but nowadays I'm lucky to be able to use a can opener.

In know its no Thomas & Betts, but would Powerwerx's $89.99 Hand Held Crimper qualify as a good crimper for SB50s? https://powerwerx.com/anderson-sb-connectors-sb50-50amp

JoeP

[Burgerman]

You cant JUST crimp most Anderson 50 connectors as the metal is too thin. The exception are the ones designed for smaller cables as they have heavy thicker walls and can be securely crimped with a hydraulic crimper.