PINNED - Lithium battery conversion/info

[C400Driver]

My battery box is 520mm x 250mm x 171mm.

Headway 38140s.jpg (205.48 KiB) Viewed 17023 times

(made with sketchup)

It's right?

[Burgerman]

Its 13 cells long, 5 cells high?

Then its 40mm x 13 long (520mm)
40mm x 5 tall (200mm )
171mm wide.

Mine is 13 long x 6 tall so 520 x 240 x 171 (78 cells, 72Ah, 42v nominal)

Yours will be 12Ah x 8 cells so 24v nominal, 96Ah.

Of course you can also add another half row on top, and still have 240mm height and 108Ah... That's as close to 3000 watt/hours as matters. So about 2.8 times the range of lead.

[C400Driver]

Sorry, 215mm tall.

I don't understand how to link bus bars together in series - parallel.

[Burgerman]

Parallel

Take 10x 10Ah cells, join all positives together. Join all Negatives together. You have 3.2v and one big 100Ah "cell"...

Take 10x 10Ah cells, join end to end, pos to neg, pos to neg, for all 10, and you have 10Ah, 32 volts.

[cdb0ewm]

Does anyone have a good source for Headway cells?
Has anyone purchased them from China?
I got a quote for $20 US each delivered to Miami Florida from China

[Burgerman]

I ordered some from www.evassemble.com fast, efficient, no customs charges. Your mileage may vary!

Eva is usually on the ball...

[cdb0ewm]

Thank you -

[cdb0ewm]

On the MK3 where did you place the controller

[Burgerman]

On an alloy plate below the seat frame, above the battery. Photos soon. The last lot of stainless bolts just arrived.

[flagman1776]

I really don't use my Pride Wrangler much... occasional camping trips & other outdoor outings. I'm actually reconstructing a utility trailer to allow me to use it more. The Wrangler weighs 345# supposedly. The OEM batteries were junk when I bought it, so I bought new Universal batteries from MonsterScooterParts.com They are massive group 27 batteries & the battery box has lots of room. I think mine we 90Ah SLA, the new ones rate 100Ah. & OUCH!! what a price for lead bricks!! These are rated to give it a 20 mile range.
The day will surely come when I'll need new batteries... I'm thinking that LiFePO4... Headway... With such generous space, a conversion would appear to be easy. How much battery would I need without sacrificing performance?

[Burgerman]

How much battery would I need without sacrificing performance?

You are asking the wrong question. That's the best way to spend a lot of money, get no extra performance or range, and at the same time "over load" the lithiums so that they have a short life. Whats the point in this? This is EXACTLY what the manufacturers will do for the new lithium marketing, once they figure it all out. The answer is that 60Ah 24v lithium will give the same performance as your 100Ah batteries roughly, with absolutely no benefits in range, service life, and greater cost. (other than weight.) So why would you want them?

The question you SHOULD be asking is this:

Whats the MAXIMUM Ah I can squeeze into the space two antique lead bricks came out?

The answer is approx. 150Ah. But this will give you around 2.5 to 3x the current range.
And because you have the same motor "load" (amps) on a 3x BIGGER battery size it has an easier life and is not heavily loaded. C rate is naturally about 3x lower. So service life, and torque is drastically improved. By maybe 2x. High currents kill lithium's faster.

And because your AVERAGE depth of discharge is now about 1/3rd of what it would be with a 60Ah battery, your cycle life will not be 1000 to 1500 cycles, but 5 to 10 THOUSAND cycles. And remember that as the battery is big, it may need charging much less frequently on average, so instead of daily, you may do this weekly... So lets say 3000 charges, weekly. That's an everlasting battery. Although shelf and USAGE life is still approx. 15 to 20 years for lifepo4 TREATED WELL.

[flagman1776]

The group 27 batteries don't come close to occupying the full battery box space... a huge advantage over the tight confines of a power chair. I am aware of the advantages mentioned which is why I asked. I have 3 years of intermittent duty on these Universal batteries.

[Burgerman]

Well then now you are aware of the issues, its up to you to do the maths, advantages, gains, cost analysis! Its not easy. Where space is NOT at a premium, as it is in a powerchair theres lots to consider. EG a lot of lower C rate cells (Calb, thundersky etc) makes a lot of sense.

And the actual Ah and voltage becomes important.

BECAUSE high C rate cells are available. That is the thing, the ONLY thing that allowed me to use the Roboteq 150Amp (300 with 500 pulse) controller with a low capacity high voltage battery. That lithium battery is only 72Ah, but is some 3000 watt hours, because of the voltage increase.

You can either go twice as fast (double motor / shaft RPM) for free since range and torque are exactly the same as the 24v setup. Because no change of gearing.

OR

You can go twice as far, (again!) by using LOWER slower gearing. Because then it takes half the amps, and gain torque free of "charge"...

If you don't get this feel free to ask how it works! It really is a free ride. You cant get this free speed/range/torque with lead. Because Peukert affect negates it and it becomes impractical. Which is exactly WHY we have what we have in stock lead powerchairs/scooters today. They evolved this way because of the battery limitations.

[cdb0ewm]

Looking for alternatives to Headway batteries for a MK3 type chair. I found the following which are very favorable priced. What do you think about these. Will I get similar performance?
Thank you

Size 148*65*15mm L*W*H，including bolts，not including PVC film，Tolerance±0.5mm.
Nominal capacity 10Ah 20±5℃，0.5C，CC(constant current)discharged to 2V.
Nominal voltage 3.2V
Charge cut-off voltage 3.65V
Discharge cut-off voltage 2V
Standard charge current 2A - 0.2C CC (constant current) charged to 3.65V, then CV (constant Voltage) 3.65V charge till current decline to 500mA.
Max. charge current 10A - 2C CC(constant current)charged to 3.65V, then CV(constant
Voltage)3.65V charge till current decline to 500mA.
Standard discharge current 2A 0.2C，CC (constant current)discharged to 2V.
Max continuous discharge current 30A 3C，CC (constant current)discharged to 2V.
Max peak discharge current 50A Lasting time ≤1 min.
Retention ability of Charge capacity ≥90% Nominal capacity - Standard charge at 0.2C CC/CV to 3.65V
Cycle Life ≥2000 times
Impedance ≤3.5mΩ Between discharge port of Cathode and Anode.

[Burgerman]

Standard discharge current 2A 0.2C，CC (constant current)discharged to 2V.
Max continuous discharge current 30A 3C，CC (constant current)discharged to 2V.

This is the problem.

Headways are 10C and where batteries are small, space is limited, and currents can be 240 amps on a 120 controller this matters. Best not to go anywhere near max C rate, so say 50 percent.

A 100Ah battery made from those cells can then only really do about 150Amp max. You may need almost double this. The 10C headways can do 1000 Amps.

[cdb0ewm]

In your discussion on the MK3 you mention being able to switch between 45v and 24v for 'outside' and 'inside' usage.
How are you doing this

[Burgerman]

No.

I mention that I may fit a slow speed indoor switch. The thing will still be fed 45v. I leave everything on max speed, on my 24v chairs. But that might be a bit lively on this one.

[cdb0ewm]

Does anyone have the settings/parameters for the Hyperion charger for Headway cells

Thanks

[Burgerman]

Yes, basically full power (20 amps) regardless of capacity.
LiFe
3.600 Volts.
Correct cell count! 13 in my case, 8 in most others for 24v.
No time or capacity limit. (untick)
Correct Ah capacity, or up to say 30 percent less. It means the cut off point is later.
TCS 100
TCS END CONTINUE

The rest don't matter to most people so just ignore.

[CPguy]

I just got a batch of brand new headway cells (the 12Ah screw tab ones) from evassemble. I mounted the orange plastic tabs but now I am at the loss on how to mount the metal connectors that are included. Do I need a nut to secure them on the individual cells? (say size M6?) But I do not see a thread to mount the nut... I am at a loss here. Thanks for some enlightenment!

[woodygb]

I believe that the cells have an internal thread ..so a screw not a nut.

[woodygb]

[stevelawiw]

If you haven't a thread at each end, and you ordered screw tab cells then they may have sent you the wrong ones. I know they do sell cheaper ones without the threaded caps ( by the way, each end should have an M6 screw in it, mine did!)

[woodygb]

You haven't ended up with these have you?

[Burgerman]

( by the way, each end should have an M6 screw in it, mine did!)

And they are unreliable and come loose. Swap for short M6 Cap screws. Allen head bolts. And clean contact area, and Loctite the thread.

[CPguy]

@ woodygb and @ stevelawiw: Thank you for the pictures! No, I certainly have the screw tab cells and not the flat tab cells. I will have to inspect the cells more closely when I get home.

Thanks for the fast replies.

[CPguy]

I can now confirm that each end of the screw tab cell actually already has an M6 size screw with an allen head in it.

[steves1977uk]

Where do you buy spare 8 pin balance cables for the i1420 charger? I've googled for them but can't find a source for them in the UK. Help!

Steve

[Burgerman]

ebay, fastlads, ANY online hobby places.

http://www.ebay.co.uk/sch/i.html?_trksi ... &_from=R40

Search 7s JST XH CABLES ETC.

http://www.ebay.co.uk/itm/10pcs-JST-XH- ... 35cb850219

[Burgerman]

Latest firmware has important fixes. 5.91. One being discharge.

Eg it allows you to discharge without it balancing. So on a big pack, top balance is maintained.

To use this to store a pack, charge normally, set discharge voltage to 3.3v and choose discharge. 3.300V is around 66 to 70 percent charged. It will stop at this point. Don't use store, as that will balance too.