PINNED - Lithium battery conversion/info

[Burgerman]

As above. But think about it like this.

Battery starts fully charged. As you move, you use power. As you slow down again, you put a tiny bit of that energy back. But not much because this if a far from 100 percent efficient scenario. So unless you add some extra power to the system, the batteries cant ever receive more power back than you just took out. So never a danger of overcharge.

That is unless you set out each morning from your bed already fully charged, at a mountain top!

[AlRedux]

Hi everyone. I stumbled upon this site a couple of months ago, read a lot, and then began a quest to make my own BM2 chair. (The BM3 felt a bit too ambitious for me as a first project). I was fortunate enough to find an old Sunrise F55 and, since my company does a lot of shipping, I was able to get it shipped to me here in the U.S. as a "tag along" on another shipment for free. Since then, I have been shamelessly copying many of Burgerman's modifications. I am finished with most of the mechanical changes and now working on the electrical and programming. I have a few questions that I hope you guys can help me with:

1. I have a Hyperion 1420i charger, so I can use the wonderfully detailed instructions in this discussion thread for its settings. However, my power supply is going to be inadequate to charge my array of 12Ah Headway cells. Can you recommend an adequate power supply that I can purchase off-the-shelf or order here in the U.S.?

2. I intend to build a single-connection charging harness, based on the Dsub connector shown in this thread. I would prefer to eliminate the Hyperion adapter boards and just wire directly to the A and B balance ports. However, I cannot locate a wiring pigtail with the proper connector (or even an extension cable longer than only six inches where I could snip the connector off one end). Can you possibly provide a pointer to such a cable?

3. Can you recommend a simple low-voltage alarm that will inform me when the battery array is below a certain voltage threshold? If so, what voltage threshold do you recommend?

4. Lastly, I want to remove the delays in the controller. I can order and make the cable, but I assume I will need the OEM programming software too. Where can I get a copy?

Thank you all so much for sharing your knowledge and experiences. Being able to go to the dog park again, maneuver myself in the tight spaces of my kitchen, and join my friends at the bar again feels very close now! This is going to be a real game changer for me.

Best,
Al

[Burgerman]

1. I have a Hyperion 1420i charger, so I can use the wonderfully detailed instructions in this discussion thread for its settings. However, my power supply is going to be inadequate to charge my array of 12Ah Headway cells. Can you recommend an adequate power supply that I can purchase off-the-shelf or order here in the U.S.?

Any, the hyperion can be set to take only whatever the max power your supply can provide.
Or theres a link to the server supplies here somewhere.
The Hyperion is no longer made, so you may do well to get a spare, or look at the Cellpro PL8 that I am now using. 8S, 40A capable. And only 1 connector required.

2. I intend to build a single-connection charging harness, based on the Dsub connector shown in this thread. I would prefer to eliminate the Hyperion adapter boards and just wire directly to the A and B balance ports. However, I cannot locate a wiring pigtail with the proper connector (or even an extension cable longer than only six inches where I could snip the connector off one end). Can you possibly provide a pointer to such a cable?

You can use the ones you have, and splice.
Or you can order the same standard connectors, on eBay, and make up your own, or you can buy longer cables and chop off the end... http://www.ebay.co.uk/itm/10pcs-30cm-JS ... 27f942fcbf

http://www.ebay.co.uk/itm/Lipo-Balance- ... 35cc9d0ff3

Or make your own any length you want. http://www.ebay.co.uk/itm/JST-XH-connec ... 35cc2f4621


Check PM

[AlRedux]

My grateful thanks for your help!
It looks like I will be making my own cables for the balance ports, as I need just a bit more length than 30cm and I am not a fan of splicing.

Also, off-topic for this thread, but I discovered that I can fit mini-bike shock absorbers to the rear without increasing width. Hoping this will help smooth the ride over larger objects while the low-pressure tires help smooth things over smaller imperfections in the sidewalks and roads. We shall see....

Al

[Burgerman]

Splicing is fine, with heat shrink, done neatly. If you want them longer use slightly heavier wire than stock connectors have.

[Scollard]

I use a pair of 12V HP Server Power Supplies wired in series to feed my Hyperion.

Here is an eBay link to a similar one like mine.

http://r.ebay.com/M6kv5Y

[DeeDee]

Here is a link to buy the black caps on ebay for the 4mm hex bolts used on the LiFePO4 Cells http://www.ebay.com/itm/181853345558?ss ... 1555.l2649

DeeDee

[Burgerman]

Just ordered 82 x 12Ah cells from http://www.evassemble.com
To build an 80 cell, 120Ah lithium pack for my green BM2 that I am rebuilding. With 2 spare cells in case.

I added this note:

________________

In export paperwork details, describe item as WHEELCHAIR BATTERY
On parcel exterior, mark as TAX RELIEF CLAIMED
Or I will be charged extra 20% tax.

Repy:

Thanks for your informaton. We have remark this in your order and make sure our shipping team will know this.

Best regards,
Michael Cheung
________________


I do not expect to pay any duty or taxes.
It costs £1000 pounds + del by UPS. (Compared to the £440 for Odyssey. So just over twice the cost).
Will give 3x the range of the Odyssey batteries.
Will give 5x the service life approximately or better.
Will save 50lb weight.
Will charge much, much, faster.
Will give better performance (5% better speed, and much better torque, less slowing on hills etc)

Lead is now a really bad way to do things.

[flagman1776]

Thanks for the link DeeDee! I just recieved them. The 4mm is the metric hex socket on the 6mm bolts.

Here is a link to buy the black caps on ebay for the 4mm hex bolts used on the LiFePO4 Cells http://www.ebay.com/itm/181853345558?ss ... 1555.l2649
DeeDee

[gcebiker]

Built a pack two weeks ago for my folding travel wheelchair.

Motors are only very low watts, and i have used LiFePo4 Radio Control Batteries from HobbyKing.com

I have fitted two of these http://www.ebay.com.au/itm/171488897769 ... EBIDX%3AIT

Charges with regular XLR LiPo Single Plug charger.
Wiring up 6cells is a bit messy,

Next one i will use something like one of these.
http://www.ebay.com.au/itm/PCB-BMS-for- ... 28077114b6

Really handy and easy to charge.

[Burgerman]

Instead of 10 years reliable service life, and complete reliability, I expect there will be trouble ahead!
That's a band aid, stuck onto a battery to try and stop it dying rather than building a properly integrated system.

[Burgerman]

EG...

Quote:
Protection Circuit Module Specifications For 24V LiFePO4 Battery Pack, Different with normal PCB, it provides equilibrium function after battery pack is fully charged, e.g. PCM will detect each cell's voltage and trim higher voltage until other cell's voltage reach same,therefore allow Li-ion cell has longer service life. Also the PCM will provide the following protections:

So if you have a bad cell, it will drag down the whole pack...

· * Balance each cell at Max. 3.6/cell ( required voltage tolerance within 0.2V for each cell)
0.2v is WAY too innacurate. Most good hobby chargers balance to 0.003mv. It means you may have cells at 3.4v barely charged, or 3.8v and tortured to death.

· * Overcharge protection voltage for single cell: 3.85V +/-0.025V
It should NEVER allow any overcharge. 3.600V per cell is best in service, 3.650v is best to allow some overcharge (and service life reduction) where balance circuitry is too small or inaccurate.

· * Overdischarge protection voltage for single cell: 2.10V +/- 0.08V
Should be controlled by the vehicles power controller in proportional fashion, when voltage drops under load, and that's WAY too low anyway. Damages cells much faster. Shouldn't be switched but proportionally controlled.


· * Continus working current: 30A
30? Most powerchairs require 100 per motor...


· * Overcurrent detection protection: 60A
As above, and if cells are CORRECTLY chosen, in both C rate, and Capacity this should not be required at all. LiFePO4 needs as much overhead here as possible for long service life. And if you are using inadequate cell C rate or capacity, it should be proportionally controlled and monitored by the controller.

· * Supply current: Max 30uA
Sends a single cell dead over time if left connected. Unless it balances all the time rather than just at the top when at CV which is bad...

· * Protection circuitry resistance: <=50mohms
10X as much as most powerchair batteries!!!

· charging current: 8A
Inadequate, usually because balance currents are way too small at 100ma or less. My hobby charger for eg balances at 1A.


Yes these BMS work. In that it allows you to fit lithium in a DIY way, so they can sell batteries that may be incorrectly sized/c rated, for the job they will be used for, or with an inadequate charge system or controller, but don't expect reliability or much service life compared to a properly integrated setup. Why do you suppose I don't have one at all on here: http://www.wheelchairdriver.com/BM-MK3- ... rchair.htm

[sourstraw]

Just a quick question- did you ever go through with making up conversion DIY? This thread is LONG and user CP doesn't offer the option to view, say, 100 posts per page.

I am thinking of doing the conversion in two steps. First, to simply convert with the same capacity I have now in my M300. Then, later on, upgrade to increase my range. This is strictly for budget reasons.

Will it work properly using my factory R-net controllers? That's ASSuming the system sees power as power, regardless of type.

[steves1977uk]

Putting the same Ah for Ah is not worth it as BM has said before. When I did my conversion to Lithium, the pair of SLA batteries I was using were 45Ah (in reality 22.5Ah), so I put a 75Ah Lithium pack made up of 8 cells in series and 5 lots of these in parallel. This gave me 3x the range in the same amount of battery space using the 15Ah cells.

The R-net will work fine, the controller will see a slightly higher voltage (26.5v) when the cells settle down after a charge to about 3.33v for each cell.

Hope this helps.

Steve

[Burgerman]

Dont waste your money doing half a conversion. Little gained, and more rapid cell degradation.

[flagman1776]

You certainly can do a nice "24" volt conversion but you don't want to build a "equal" pack. Trying to match used cells with new ones is a bad idea (expanding a pack later on). Figure out how much you have room for & build the right pack once. Since you're staying with compatable voltage to the stock controler, you don't have program anything on your chair.
No BMS. Charge with a smart charger & power supply. You'll need to program the charger through it's menu is all. I love the fast charging capabilities.

In actually you'll keep your speed up because the voltage doesn't drop in use like lead.

[Burgerman]

Reasons not to swap a 70Ah lead battery for a 70Ah lithium. The whole point of lithium is that done properly it allows a lot of advantages exactly because of the fact that you can install 1.5 to 2x the Ah in the same space.

- minimal range gain.
- deeper discharge level than need be, and more frequent charge cycles so shortening lifespan
- higher discharge rate per cell - shortening service life.
- battery is 4 times lighter Ah per Ah than lead, so stability will be lost requiring much ballast.

To maximize the lifespan, and other advantages that lithium offers it is important to replace the lead with as many Ah of lithium as can be crammed into the space available. Or you may be wasting your money.

[Burgerman]

http://www.wheelchairdriver.com/BM-MK3- ... rchair.htm

Read...

[gcebiker]

I think it was missed, the pack i built was for a 200w folding power chair.

I am 120kg and the folding power chair gets me around the Sailability Club all day just fine,
My scooter i posted about is also run on this same pack.

The scooter weighs just 30kg including the battery, this i can easily lift into and out of my van.
Range is over 20 real world KM, that is me going fishing for the day, fully loaded with myself and a trailer i tow with all the gear/bait/ice.
Battery is only 15ah, if i wanted to last longer i would put two packs in (the scooter and folding chair have holders for two packs should i need em)

My focus is on the efficiency of the drive train, as you pointed out, skid steer is power hungry.

My scooter is light, it is fast, it is efficient and it is now over 9 years old....and it was cheap to build
the battery pack well suited to its task.

I look a bit like a giant fat circus bear on my toy scooter but that's a whole other issue.

[Burgerman]

80x 12Ah headway cells arrived from evassemble. No tax/duty to pay.

[Burgerman]

viewtopic.php?f=2&t=5380&start=40

Here: viewtopic.php?f=2&t=5380&start=40

Scroll...

[Burgerman]

FMA PL8 V2 CHARGER SETTINGS!!! Too many emails so posted it here:
PL8 V2 Charge setup for Headway Pack.
Go through ALL OF THESE EXTREMELY CAREFULLY TWICE!!!!

Load and open a HIGH POWER A123 Pre-Set!
Now open the ADVANCED settings in PRE-SET via PC control.

1.Rename the Pre-Set to HEADWAY PACK or your own choice.

2.Open GENERAL tab:
Set: Lock Preset NO. (Change to YES only once you are sure it is working and tested correctly!)

3. Open DETECTION tab:
Low Volt. Restore: 2.55V (or less if poss. in some future firmware)
L.V. Restore time: 3 MINS (Or greater as above)
L.V. Restore Amps: 500mA (or MAX available in future firmware)
Parallel Packs: NONE
Cells: AUTO DETECT

4. Open CHARGE tab:
Charge Amps: Set to a figure that allows a full charge overnight, typically 20.00A for a 100Ah pack. 10.00A for a 50Ah pack. (Choose the 5 Hour rate). Or up to 40A if in a hurry! Slower is kinder to cells, allow time for balancing, and CV taper at the end. The 5 hour rate allows charge to complete in around 6 to 8 hours typically. Choose higher Amp rates if it doesn't end fast enough for you.
Increment: 5mA: NO
Charge Voltage: 3.600V full capacity. Or better to 3.550V. 3.550 is preferred if you have "safety charge" issues, or if you just want your pack to live a longer time. Lithium doesent like higher voltages. You lose less than 0.2% capacity only.
Conv Freq: 125Khz
Cold Weather: NONE
F.Ave. Past 1min: NO

5. Open DISCHARGE tab:
Discharge Mode: INT/REGENERATIVE
Discharge Profile: CONSTANT CURRENT
Discharge Amps: MAX (Allows a max of 100 Watts at 8S LiFePO4 voltages)
Discharge Voltage: 2.7V (ABOUT 95% DISCHARGED)
CCCV Disch: YES
Cycles: 1
End Cycling with: CHARGE
Cool Down: 5 MIN
Store Chg or Dsch: NO

6. Open BALANCE tab:
Balance Mode: PROPORTIONAL
Balance Speed: 16X
Balance Start: ONLY AT CV (or 3.30V unless it causes problems, in which case SET TO ONLY AT CV). (3.40V is preferred, it will be available in next Firmware Update)
Balance Set Point: -1mV
Balance Entire charge: NO, (or YES - if you choose start at 3.300v, unless it causes balance problems in which case NO, ONLY AT CV).
Bal. Discharge: NO (Important!)
Bal. Dead Band: 2mV
Bal. Limit CSET/10: NO
Bal Current Limit: 1000mA (1Amp)

7. Open TERMINATION tab:
Termination Mode: MANUAL CURRENT SETTING
Manual A. Setting: For 3.600V Set this to 1mA per battery Ah. Or next highest setting. Example, a 60Ah battery set 60mA. A 100Ah battery = 100mA etc) Setting it lower means it may never actually end. Same may happen with an old battery, so in this case increase setting. Setting it higher means charge ends sooner but may not be fully charged and fully balanced. E.g. a 72Ah battery needs to be set to 75mA termination and test to be sure it ends correctly. May take a long time.
If charging to 3.550V instead, set it to HALF this figure or a fraction more. So an e.g. - 72Ah battery, set to 35 to 40mA termination.
Require Bal. Done: YES
Require All Chg V: YES
CV Timeout: NONE

8. Open Screens tab:
Leave Default settings here!

9. Open FUEL tab:
Pack Capacity: 0mAh
Use Fuel Table: NO! (Doesn't work with large LiFePO4 cells).

10. Open SAFETY tab:
Safety Charge Stop: NO

[Burgerman]

http://www.wheelchairdriver.com/BM3-con ... arging.gif

And you should see something neat after 2 or 3 charges like this.

[Wheazel]

Hi

I am building a light electric wheelchair. Intended to be portable and outdoor capable.
I am looking for advice on wheelchair specific things to consider when building a wheelchair battery that should last.

Was thinking I could google up some good ideas and info regarding lithium builds for powerchairs, but apart from the droves of conversionkits from china I don't find much.
Admittedly I am not aware of all places to find info about this either.
I've seen Burgermans headway builds and those are nice, but I am more intrested in using 18650 cells.

So far I have built a small pack for a prototype chair to test things out. Only 7s6p out of samung 18650 25R cells. Basically a high discharge capable and reasonably cheap cell.
Works well with a bestech bms and gives around 18km of range at max speed ~8km/h. (Mostly flat land, tested on gravel road)

I charge this small battery with a cheap fanless 2A charger.

Also built a cargobike with a large battery out of an older 18650 LG cell called D1. High capacity low discharge cell.
They operate under recommended conditions due to the pack being 18s26p. About 65-70V under use and delivers maybe 65Ah. (Could be more but I charge to 4,1 or 4,15V. The cell is "intended" for up to 4,35V to deliver the full capacity)
Still a 4-4,5kWh pack that weights abit over 20kg.

For charging this battery I use the built in intelligence in an adaptto max-e controller with bms. The dc comes from a 1800W eaton power supply.
Do any systems similar to the adappto exist for wheelchairs? Are there any thriving DIY community similar to endless sphere?

I would appreciate any advice regarding the wheelchair specific application. Hoping to achieve a battery thats light, reliable and has very easy plug and play charging.
I could put a battery together similar to the small test battery, but it would be stupid to just assume that's as good as it gets.
And maybe someone else can draw ideas from the batteries I have built so far.

Pictures of the large cargobike battery, and the stuff I use to put them together:

[Burgerman]

samung 18650 25R are OK for short term use. But for a powerchair they have several problems, much like all LiIon batteries. They are very energy dense. But they are not the best choice.

1. They don't have much of a cycle life. Typically 500. If you never exceed 4.200V and better still 4.150V. And discharge at low rate. And keep cool. And a horrible high current cycle life of around 100. They also have a short shelf life compared to LiFePO4 cells of around a year or so. LiFePO4 also have a 1500 cycle (100% DOD), to 2000 cycles @ 80% DOD and 10 year shelf life. This is in response to your comments about long lifespan and reliability.

2. They are not safe for powerchair/disabled use. They explode and burn much like laptop or camera batteries can and those are not suitable if you cannot get off! LiFePO4 do not burn.

3. BMS are the main reason for short service life, and reliability issues. And fires. Inc the Boeing issues... They repeatedly pulse the cells over the best charge voltage for long life too so forget 500 cycles. Think about a 2 year old laptop with all but useless batteries. Amongst other things...

[Burgerman]

https://www.powerstream.com/p/INR18650- ... asheet.pdf

https://www.youtube.com/watch?v=ZTzEHsJVZhA

https://www.youtube.com/watch?v=Tpb-n22Y-sY

You wouldn't want to be sat on a seat made of these...

These however are good for 4x as many cycles, much higher calendar life, are very high rate, and don't burn. These too will die faster using a simple BMS and are better charged with a balancing hobby type charger. http://www.hobbyking.co.uk/hobbyking/st ... ch=lifepo4

[shirley_hkg]

I love to know how good and easy to use of the small contact welder.

I may need one, as 18650 does have advantage, and it is probably the right way to go.

[Burgerman]

Not unless you like trying to find failed cells, in spot welded packs, fires, and short service life.

They make some sense only on small disposable removable batteries like laptops or cameras. If you are not disabled and sat on them! ONE is bad enough. http://www.candlepowerforums.com/vb/sho ... A-exploded

[expresso]

http://www.powerstream.com/LLLF-24v-10ah.htm

would something like this work if i added it to my chair as an ADD ON - connected to my external cable -

its not alot of Ah - would this help somewhat on distance - to keep me going longer before charging both this battery and chair separate - ?

seems easy since its already 24V - dont have to do anytihng other than make cables to connect and thats it - something simple like this is perfect for me - but only if helpful even if not alot extra distance - but enough so i dont drain my chair batteries down before recharging -

any ideas ?

[expresso]

http://www.pingbattery.com/servlet/the- ... ium/Detail


something like this maybe ? i am looking to add a pack to my chair - as a ADD ON - and just plug it in - but what works best for me is something thats simple - meaning like nothing for me to do other than to make the correct cables to connect - charge etc,

one battery is easier to do than get two 12 V - then i have to connect - maybe solder etc, - i want to avoid if i can - One 24V would be great -

is something like this going to work ?

if anyone knows - can post a link to a battery i can use - instead - that would work and make a difference -

thanks -