PINNED - Lithium battery conversion/info

[Scooterman]

Did you notice my speed pot goes past Mr Hare into the “Oh my god that’s so fast” speed setting.


PS: Didn’t Spinal Tap’s amps go up to 11 or something?

[Burgerman]

Yes.

[terry2]

BM - on a chair thats 6.5mph - stock - if adding tires 350-8 and lithium - adding volts to the motors - from a stock 22.5V to 25.5V - or 25V - would 8 or 8.5mph be reachable ?

Wouldn't adding volts damage the motors?

My 8mph motors does 8.4 on a flat.
If it was safe, I would up the voltage as well.

[Scooterman]

If you did that you’d need a controller. Check out BM’s BM3.

I was going to double volts (and hence speed) on my scooter but it all gets a bit complicated. That’s why I bought 16 cells as 16x3.2v gives many volts

[wheelie junkie]

Never had those issues in W10, mind you I strip out most of the unwanted garbage before I install it. Now I run W10 Ent LTSC2019 with the Store apps I CHOOSE to install, best of both worlds!

Steve

Exactly why I use a Mac, I've never had to waste my time stripping anything out, just install and use

[Scooterman]

I like these scooters, although I think they're a bit big for going in shops, etc.

John, what's your opinion, self-build lithium packs, and off-roading?

The top spec model scooter is 15mph and has 85Ah batteries as standard.

Do you reckon for off-roading you're better fitting the biggest Odyssey batteries that will fit, rather than our self-built lithium packs?

I can't imagine the connections of any pack I built could stand up to this sort of shaking for long, although neither could I!

I expect you could build a pack that would withstand it. I remember seeing you doing a bit off roading while walking the dog. I was wondering if that was with one of your lithium powered chairs or the odyssey one/s?



youtu.be/XQl3qBbd2WA

[Burgerman]

Lead and off road is a joke. Its all weight (bad) and its got so little energy that after about 20 mins you are out of power. So lithium is the only sensible option.

But for the life of me I cant see what possible pleasure anyone would get out of doing that.

[Scooterman]

Yes. Shirley has bunch of them to offer.

re PSUs. I've not forgotten about these Shirley, I'm still trying to work out where I can squeeze one under the bodywork for road trip away from home charging. The 100-240v range is useful if go abroad.

[Scooterman]

But for the life of me I cant see what possible pleasure anyone would get out of doing that.

I do agree, I'm totally with you on that one!

[expresso]

BM - on a chair thats 6.5mph - stock - if adding tires 350-8 and lithium - adding volts to the motors - from a stock 22.5V to 25.5V - or 25V - would 8 or 8.5mph be reachable ?

Wouldn't adding volts damage the motors?

My 8mph motors does 8.4 on a flat.
If it was safe, I would up the voltage as well.

only way to know for sure is to do it and hopefully it wont damage them - it may shorten its life a bit i would think - i guess it depends on the motors - how well built they are in the first place etc,

stock volts are keep lower because of lead - most likely - since lead cant supply more - but lithium can and does stay steady at 26v till it at its end - so we can make use of higher volts 24v 25v etc, leaving a little left over for control - gaining free speed and not loosing bottom end either -

you can maybe gain at least 9pmh with a few extra volts - once you try it - you may not want to go back

[steves1977uk]

The AMT motors can do 45 volts with no problems as BM has used these on his BM3 chair build. Cheaper Chinese made motors MAY handle higher volts but would need testing fully loaded to make sure nothing breaks or fly off!

Steve

[expresso]

i have used my 646 with a few volts higher - but i havnt used it that way for long - they did die on me - and got new motors now - but i cant say it was because of the volts since it was a short time with the higher volts - they were already used and Old by then - now with the new motors - i can use the chair and see how long they last - i dont expect them to last long either way because of how i use my chair - alot range during the summer time - if they last as long as my first set - then its best i can expect which was about 4 years - most motors die before then with out even adding any volts -

[Scooterman]

Wouldn't adding volts damage the motors?

My 8mph motors does 8.4 on a flat.
If it was safe, I would up the voltage as well.

you can maybe gain at least 9pmh with a few extra volts - once you try it - you may not want to go back

But unless I'm missing something the only way terry could get more mph is adding more lithium cells and changing the controller.

[steves1977uk]

No SM, the R-Net defaults to 21.5v for the motors, to make sure there's headroom for steering when using LAs. With Lithium we can up that to about 25v safely to gain some free speed since it doesn't drop unload like LA bricks do.

Steve

[Scooterman]

Ah! Got it, thanks Steve

[expresso]

i think it may depend on the Chair and how its set from factory - mines came with 22.5V set from new Rnet

i have since upped it to 24v - and feels fine - i may try 25v this summer - well see - i know i do about 10 easy the way it is now -

[Scooterman]

I shall check my rnet settings

[shirley_hkg]

Clearly that device is unsuitable, but I do wish someone could find a cell balancing board that would: (1) start balance only near or at the end of CV, (2) dissipate or exchange enough current to balance reasonably quickly (would 3A be enough?). It should be rugged enough to be mounted in the chair and not need any user attention (after initial programming). As it would only be doing something when connected to a charger, it can be a passive balancer that just dissipates energy from the highest cell - the mains watt-hours wasted would be tiny in any case.

There are lots of cell monitor/balancer boards out there that use an Analog Devices or TI chip that can do the above, but that can pass only mA of current. One of those chips plus 8 MOSFETs and 8 resistors would seem to be all that we really need, but I'm not up to designing and testing same (at least not with too many other projects underway). So, with all the "stuff" that's out there, isn't someone making a simple board like this?

The only thing that has kept me from going LiFePO4 has been the fact that we can't have a setup that only I can hook up for charging. It's hard enough to get people to remember to push the rocker switch on her dumb charger (and even I have forgotten once in a while), no less follow a sequence of who connects to whom followed by one or more button presses. It's not just that I'd rather not have yet another daily chore. Perhaps if I were 40 or 50 y.o. that would be OK, but I've already got 73 behind me and Rachi is going to still need her chair well after I'm gone.

You will get one , very soon.

[LROBBINS]

I am avidly awaiting news of this. Not that I need another project, but it's absolutely clear that the next battery for Rachi's chair WILL be LiFePO4 - even if a balancer for dummies does not become available.

[Burgerman]

Clearly that device is unsuitable, but I do wish someone could find a cell balancing board that would: (1) start balance only near or at the end of CV, (2) dissipate or exchange enough current to balance reasonably quickly (would 3A be enough?).

As long as you charge at under 3A.

But even if there was an 8A on board device to do this. Thats not really enough. Because in my salsa for e.g I am fitting 16 of those 105Ah cells. So 210Ah. Since you can use all of that, its quite possible you may want to return say 190Ah. Ignoring the CV part for simplicity, that will take 190 div by your 8A. Or a full day... Plus CV.

As such I am charging my BM2-L now as we speak at 40A. Its 120Ah battery will then be done in 3 hours plus about 1 to 2 hours at CV/Balance. So that wouldneed something on board that can dump 40A per cell. If 7 cells are full, then it will need to dump 40A x 3.6V X 7 watts... Over a KW! As you can see Throttling the charger output proportionally is the answer. As we are doing with the PL8.

[shirley_hkg]

How about user defined charge current , @50A max. , and won't pump cells up 3.85V then stops / starts again and again ?

[LROBBINS]

No John, that's not what I have in mind. I would want the balance board to not do anything until near or at the end of CV when it would then tell the power supply to reduce maximum current to what the balance circuit can handle and only then start to dump from the highest cell. In other words, there would be no involvement of the balancing circuit except at the "finishing" stage.

[Burgerman]

Are you just talking about a big BMS?

If its used only for charging they can work. But the problem is that the devil is always in the details. And a pile of code. And they can be good/bad or indifferent.

However you do that you are also blindly relying on an unseen BMS and a bunch of wiring. I am discharging a 120Ah 5 year old headway pack right now because one group (group 1 of 8) has developed a high self discharge rate. And when I discharge the pack, all cells stay within 8mV up until around 95Ah. Then that same group drops like a rock. Ending at about 107Ah. The other cell groups are still at 3.2X Volts.

Without a PC and a graph, how would I detect this possibly bad cell or loose connection? Its equally much needed to check out a new pack. Many here find issues to correct before saying its ready for use. So quite apart from charging, its still going to need to be monitored one way or another.

[Burgerman]

No John, that's not what I have in mind. I would want the balance board to not do anything until near or at the end of CV when it would then tell the power supply to reduce maximum current to what the balance circuit can handle and only then start to dump from the highest cell. In other words, there would be no involvement of the balancing circuit except at the "finishing" stage.

If it could tell the charger to reduce current, to less than the balance current plus CV current was, then it would work like the hobby chargers.

[shirley_hkg]

I am avidly awaiting news of this. Not that I need another project, but it's absolutely clear that the next battery for Rachi's chair WILL be LiFePO4 - even if a balancer for dummies does not become available.

€35.00

[shirley_hkg]

The first BMS I knew that controls the charging current .@50A max.

Direct output. Instead of cutting output, it has three alarms to inform user battery states.

BT connect to cell phone , and to program the BMS.

Individual cell scaning and balance @2A.

Many more , till I look into it later.

[Burgerman]

Again, wrong thing. In wrong place. Asking wrong questions if that phone screenshot is part of it. But as always the devil is in the details that we will never know! Does it proportionally balance, stay below the correct CV voltage per cell, and throttle the charger? Not ON/OFF?

[shirley_hkg]

Yes , throttle the charger amp , so no more ON /OFF.

[Burgerman]

How?

[terry2]

BM - on a chair thats 6.5mph - stock - if adding tires 350-8 and lithium - adding volts to the motors - from a stock 22.5V to 25.5V - or 25V - would 8 or 8.5mph be reachable ?

Wouldn't adding volts damage the motors?

My 8mph motors does 8.4 on a flat.
If it was safe, I would up the voltage as well.

only way to know for sure is to do it and hopefully it wont damage them - it may shorten its life a bit i would think - i guess it depends on the motors - how well built they are in the first place etc,

stock volts are keep lower because of lead - most likely - since lead cant supply more - but lithium can and does stay steady at 26v till it at its end - so we can make use of higher volts 24v 25v etc, leaving a little left over for control - gaining free speed and not loosing bottom end either -

you can maybe gain at least 9pmh with a few extra volts - once you try it - you may not want to go back

Thank you for the info