PINNED - Lithium battery conversion/info

[Burgerman]

Oh yes. Thats good as a charger too.

[Thierry]

Japlar Schauer 24v 7A :


The charger changes to constant current 7.0A. When the battery voltage reaches up to 28.6V, the charging stage changes from (CC) Constant Current to CV (Constant Voltage) mode.

Stage 2: Constant Voltage Mode (CV)
The charger holds the battery at 28.6V and the current slowly reduces. The moment the current reaches 0.5 C (C= Battery Capacity), is called the Switching Point. The Switching Point is one of the great features of this battery charger that it can adjust the current automatically according to the battery capacity. Other chargers without microprocessors are not capable to adjust the current automatically.

Stage 3: Standby Voltage Mode
The charger maintains the battery voltage at 27.0V and current slowly reduces to zero.

Thé s'ils similar 12A models.

[expresso]

those are not too bad chargers for plug and play - they even have a 20A model also - But i also found out later on - if you call the company and ask them - they can make it to your specs - in terms of Charge volts etc, - it may be worth a try at calling and asking if they can make it for 28.2V for Gel settings - and what ever the term. is etc, then float

[Burgerman]

Just to scare you THIS is a PL8 hobby charger doing nothing, except MONITORING ONLY VOLTS, as a typical mobility charger charged a powerchair. Scooterman wrote on it, incorrectly.

The battery hasnt a hope in hell of getting a proper charge, and lasting a long time.

Its such a mess its impossible to say what the hel its actually doing.

[Burgerman]

And here is a hobby, PL8 charger CHARGING the battery properly!

In this case its an ODYSSEY battery, so correct CV voltage is 12.70V at 20 centigrade.

First part is CC. 2nd part is CV stage. Only 2 stages are needed if the CV stage continues until a very low 68mA. Or double this if charging in parallel (2 batts) as shown. Or 8 hours CV whichever is sooner.

THIS is what the yellow graph SHOULD have looked like.

[Burgerman]

Here are the AMPS gradually falling away.

Stage one is CC (Constant Current)
Stage 2 is CV but the amps naturally fall to an extremely low level in time. Only then is it charged. Many chargers stop far sooner. And rely on around 6 to 12 hours float to top up completely. If you do not allow that time, they will become rapidly sulfated and deteriorate.

[Burgerman]

Heres a 3 stage graph. Idealised drawing rather than measured.

Remember if you continue the CV stage for long enough (1000thC or 8 hours typically) at the CORRECT voltage for the specific chemistry no float is needed. And 100% charge completion happens overnigh usually. Which is why its the best way to do this in cyclic use.

Also remember that no mobility chargers or any cheap generic chargers come close to achieving this. So you get short range, and short battery lifespan.

[shirley_hkg]

Are lugs available that can accommodate a large diameter cable but still have only an M4 bolt clearance hole?

The reason I ask is usually the larger the cable size the bigger the lug bolt clearance hole?

At least that's the way it tends to be in the UK but I'm only familiar with power/mains electrics so perhaps automotive lugs are different? But then it seems everything is available in China. Some of the stuff you post Shirley you'd never get over here.

It can take 8awg cable.
Ring OD @0.473''
Barrel ID @0.19''
Thickness 1.5mm.

Battery has 10mm round terminals .

[shirley_hkg]

Can I have a link to accurate measurements of those 105Ah cells?

They are not perfectly flat. I will pile them up and measure the thickness of 8 cells .

Official specification file too big to post , 775k.
Still want it ?

[Scooterman]

It's amazing the stuff you can get Shirley.

It's really useful

The lugs you got me to fit the balance leads but with a M6 bolt hole you could never get in the UK.

[Burgerman]

Lugs...

Ring terminals?

[Scooterman]

Lugs...

Ring terminals?

That's true you're right they are ring terminals, I don't know why I call them lugs? I think I probably learnt it from the old boys at work when I was an apprentice. Just like foolscap sheet paper, I always assumed they meant A4 sheet but I never did discover.

[Dan]

They are not perfectly flat. I will pile them up and measure the thickness of 8 cells.

I would love to know the size too.

Lugs...

Ring terminals?

That's true you're right they are ring terminals, I don't know why I call them lugs? I think I probably learnt it from the old boys at work when I was an apprentice. Just like foolscap sheet paper, I always assumed they meant A4 sheet but I never did discover.

Google image search for lugs.
https://www.google.com/search?q=lugs&cl ... =829&dpr=2

[Scooterman]

I think the term ring/crimp terminal tend to be used for the smaller sizes and lugs for the larger sizes? But I dunno, I guess it's like scone and scon (scone). I say scone cos I'm posh and it's got an 'e' on the end, whereas common people say scon .
But I mustn't digress cos I messed up this thread last week. So I'm staying stom from now on unless it's on topic!

[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.

This new breed of BMS I mentioned earilier in page 162 , is available now. I need to change the power module to a 18Vdc---36Vdc , 5V / 5A one for our application.

Which model will fit ?

Now it offers as low as 3S version . Got one & test, this new BMS .

No draining cells of high volts, so no heat .

After the first cell got fully charged , it starts charging the others @2A , one by one , till all cells are full.

Wish me luck.

[LROBBINS]

I see myself having to send a fair chunk of change for batteries as soon as that top-ony BMS is available. The need for a SIMPLE charging setup is the only thing that's been holding me back as LiFePO4 would have a major advantage for Rachi's chair beyond all of the things talked about here. Getting weight off the rear casters (now at 30%, more when tilted) would massively improve its handling!

[shirley_hkg]

LiFePO4 means a lot CHEAPER to us , let alone its longevity.
I can get real 210A ≤£500.00.
A pair of G24 MK gel ask £900.00 here.

[Burgerman]

900 for 40Ah usable from gel.
500 for 210 all usable from Lithium, with 7x the lifespan, and 5x the range, just over half the weight...

I will be ordering a set of those very soon.

[Irving]

900 for 40Ah usable from gel.
500 for 210 all usable from Lithium, with 7x the lifespan, and 5x the range, just over half the weight...

I will be ordering a set of those very soon.

+ shipping + (if you're unlucky) 2.7% import duty & VAT on the lot.

Nevertheless, if those cells check out, I'm seriously thinking about getting some.

[Burgerman]

If they added 100% tax. And if they added 500 shipping. They would still be WAY cheaper than lead, when you compare lifespan alone. And that does not even take into account the fact that you have less weight or that you can fast charge, or that you have bought 5x the amount of fuel... On range alone, you would need to pay for 10 MK Gels... Which doesent fit and is 20x 52lb. Or half a ton!


Shirley tested a set. Full capacity. Low resistance for a high capacity low C rate type cell, and consistent. Only negative is the small M4 thread. But if you are not ham fisted and understand what you are doing that need not be an issue.

[Irving]

Shirley tested a set. Full capacity. Low resistance for a high capacity low C rate type cell, and consistent. Only negative is the small M4 thread. But if you are not ham fisted and understand what you are doing that need not be an issue.

M4 definitely isn't an issue. Get a bike stem torque wrench 0.5 - 10Nm set for 3 - 4Nm or finger-tight + 1/2 turn approx, or better still stud them. Use the right ring terminals (e.g. AMP Solistrand 324061 Nickel/tin plated copper 10mm dia, 4.4mm hole for 6mm - 10mm sq wire, from Farnell or Chinese knock-off) to give the right cross-section for the current - I think this is important, there's not much contact area with M4, its much more critical than M6 and cheap ~6.5mm dia terminals might get hot at high load.

[stevelawiw]

500 for 210 all usable from Lithium, with 7x the lifespan, and 5x the range, just over half the weight...

I will be ordering a set of those very soon.

If enough of us want them at the same time could we perhaps order a pallet?

[shirley_hkg]

If enough of us want them at the same time could we perhaps order a pallet?

Good thought.

Minimum lot of 100 cells, directly from factory.

[stevelawiw]

Hmmm put me down for 16
Shame batteries are so bloody heavy. Could we perhaps put them in a bigger box and fill the gaps with helium ballons?

[Burgerman]

A little maths says that for 16 cells, the box needs to be around the size of a medium sized house. If the box is weightless. Which it wont be.

[Scooterman]

Hydrogen - more lift so smaller box

[greybeard]

BooOOOooM!!!

[swalker]

I have successfully put in a set of 176 Ah LiFePO4 cells into my Magic Mobility X4 wheelchair. Now I am considering doing the same thing for my Permobil F5 wheelchair.

I do a lot of downhill riding. In the summers, I often ride the gondola to the top of our local ski area and then wheel down various trails to the bottom. I usually take a fully charged wheelchair when going on these excursions.

The F5 currently has Vision Group group 24 lead acid batteries (appear to be AGM). These batteries came with the wheelchair when I bought it used and my research shows that are not very good batteries at all. I have a pair of MK gel batteries that I could put into the wheelchair if I need ot.

If the F5 is fully charged when I start heading downhill, I will eventually get a "PM High Battery" message. The Rnet manual says this happens when the battery voltage is detected at being over 35 volts.

I have also had this message when doing the ride in a Permobil C500 with MK group 24 gel lead acid batteries.

Presumably, the wheelchairs' motors are acting like generators when going downhill and charging the batteries for me.

Regardless of the cause, if it does this with LiFePO4 cells, it seems like it would do irreparable harm to the cells.

Does anyone have any thoughts about this? I would really like to avoid destroying a set of LiFePO4 cells while riding downhill.

Thanks for your help.

Steve

[ICEUK]

Im going to make a charge cable for a lithium battery (my winter project) i ordered the 3ft cable that goes from powerlab 8 to the dsub connector, i would like the cable to be longer do you think its best to buy another cable making it 6ft and just plug them together or extend the exsisting cable i have. Or Cut the one end of i dont need and solder new wire on?

[Burgerman]

New cable.