I need some advice on building a battery charger for my bank of 20 Li-ion 5000mAh 26650A

I want to build a battery charger for my bank of 20 Li-ion 5000mAh 26650A.

Held in place by Battery Bracket Plastic Holder.

These will then be ready to be spot-welded with nickel strips

Finally covered by a Lithium battery pack charge controller with a balancer module function (HX-4S-F30A)

I am now reading various disturbing reports about “Li-ion 5000mAh 26650A” batteries catching fire if one starts then they follow on and are extremely hard to extinguish.

I have a couple of Stepper motors kicking about and I was hoping to use either one or both with a shaft coupling.

• 34HE45-6004S 6.0a 8.2Nm
• 34HE45-6004S 6a 12Nm

Both have these wiring colours: RD/BK/BL/GN

The person/company that gave me these specifications has now become uncontactable.

I have all the tools needed for the project plus testing equipment.

I am seeking a tried and tested schematic for a “battery charging unit”

Once this is built I am hoping to build a pure sine wave 1200-watt inverter, as a tried and tested schematic for this unit

I have some spare double-sided Breadboard Prototyping Strip Board, or if it is not feasible I bow to your advice.

Are you wanting to connect all twenty in series, or in some series-parallel combination?

Any series connected lithium cells need an undervoltage/overvoltage and cell balance system connected to the battery pack, separately from the charger.

The charger should have a precise voltage setting and current limiting - plus automatic cut-off if it will be continuously connected.

Once the cell arrangement is known, it may be possible to find an appropriate balance/protection unit.

3V to 4.2 V Steppers & 20 batteries and a future inverter ... hmm

The steppers are low holding voltage rated 6A steppers
From this V*I = 4.2V for rated temperature rise
( I recommend a stepper fan, if using this or reduce idle current then you can apply twice the voltage but must be current limited then idle drop current for faster steps.)
A simple solution uses 1S cells with as many in parallel for DC operation only.

For an inverter, the series array depends on your goals for a BMS. A 20 channel BMS will exceed your budget.

Given Li Ion Vf = 3.7 V and Steppers rated for 3V and 4.2V (I*DCR) I suggest an inexpensive float charger with current limited for CC and CV to 3.7V so that exceeds your load current while partially meeting your CC limit.

Otherwise, you need a battery current sensor independent of the charger current sensor to regulate CC, CV and cutoff = 10% of CC with hysteresis. For a fast smart charger, I expect 4A * 4.2V * 20 cells = 336W minimum is needed. This might be done with 4.0 V per cell with a small reduction in Ah capacity but more recharge cycles then use an old PC PSU 12V with a 3S string and a battery charger module that senses battery current independent of the load or charger.

The AC Inverter is an independent application 20 * 3.7 = 74V dc with a desire for P_out inverter power, then you must

Tony Stewart said:

A simple solution uses 1S cells with as many in parallel for DC operation only.

Click to expand...

Stepper motors are current controlled, not voltage.

Reading again:

sheffieldyorky said:

Finally covered by a Lithium battery pack charge controller with a balancer module function (HX-4S-F30A)

Click to expand...

That implies a 4S5P arrangement, if twenty cells are used?

Also, that module is a protection and balance type, but the are NOT charge controllers. That's the unit that goes between the cells and outside world, in effect; protecting the cells from either the load or the charger.

The ratings for those modules are also generally short-term peak, not continuous working current - I'd go for something rated 100A or more with that quantity and size of cell.

In principle the battery module itself would end up something like this, though five cells tall. This has a "40A" BMS on a pack that will not be used above 10A.

Hi there people and many thanks for your contributions.

Please allow me to supply you with some of my background and qualifications.

I owned and ran a very successful Mechanical & Electrical contracting company at one particular time I had 150 men and women working for me, this was a fairly large M&E and some civils, finished Project value was £10m ($ 12,856,850.00 at today’s exchange rate)I don’t know what it was back then.

While my company was trading we installed many LAN systems and I always built the server/s.

It was about this time that I gained a Higher National Diploma [HND] and the area was in construction.

In the electrical division, we installed CCTV, overt & covert, Access control, POS systems, Barrier systems and various other low-voltage installations, we never touched industrial (it’s a whole different ball game with that stuff), although we undertook many three-phase installations.

We successfully traded for 35 years until I closed it down in December 2008 due to the UK recession, a sombre day for one and all.

So as I was a single guy I went on a well-deserved scuba diving holiday (P.A.D.I qualified) for a couple of years in and out of the UK picking up the mail and attending to anything outstanding.

So I got tired of that and thought about buying a business but then thought about the economy and decided against it, just at that time a neighbour (past client) knocked on my door and said I know that you install LAN systems and you built my server can you fix my laptop, I said sure, an hour later I took it next door all fixed, he then told me about some of his colleagues who had problems and it went on from there.

I now purchase broken laptops from eBay fix them (down to component level) and sell them back on eBay at a profit c/w a 12-month guarantee, I have NOT had a laptop beat me yet, so much so it has paid for a nearly new Audi A3 1.9Tdi. At 76 years old I undertake this just to keep my brain happy.

The reason why I am telling you all this is because facts and figures are coming up in Forum member replies to be honest some of it is phrases and figures that I have never come across, I’m only being honest.

I think “Tony Stewart” knows what I am trying to achieve with the quote

“3V to 4.2 V Steppers & 20 batteries and a future inverter ... hmm”

I am supplying images on how I was ( and I say was, in my thread starter “ due to various disturbing reports about “Li-ion 5000mAh 26650A” batteries catching fire”

With regards to electronics, I am happily working at the computer component level and all that it entails.

As a new member, I really don’t know what I can and cannot say on this Forum, so if a Mod sends a P.M. then I will not be overstepping guidelines.

As previously stated I thought it only fair to provide my experience and qualifications, as I am not exactly behind the barn door where electronics are concerned but nowhere near the knowledge and experience of the contributors to my thread.

Many thanks

Tony

The commonest reasons for lithium battery failures with good quality cells and no physical cause (damage or shorts etc) are overvoltage, undervoltage or excess currents / overheating.

That's why the protection and balance module is essential as part of a self-contained battery pack - it prevents it being overcharged, or overdischarged while in use.

People thinking the BMS is also a charge controller is a common and serious problem, as the charge current will never taper off properly as the pack reaches the correct voltage, among other things. That's partly down to many advertisers not really knowing the technicalities of what they are selling.


What is the maximum load current going to be for the battery pack?

And, what are the steppers for; how will they be driven or controlled?

rjenkinsgb said:

Stepper motors are current controlled, not voltage.

Click to expand...

They can be either or both. Mainly they are quadrature BLDC’s with 200 poles that to achieve optimal performance with least effort need a Uno+CNC shield or STM32 or Riprap card with some design goals. The servo constants for acceleration with current control, velocity with max L/R slew rate and step rate then voltage control for holding torque. Damped control is best done with an oil filled ring.

Welcome to the group sheffieldyorky
Tony near Toronto
EE since 73

Tony Stewart said:

Welcome to the group sheffieldyorky
Tony near Toronto
EE since 73

Click to expand...

Hi there Tony
Many thanks for the welcome.
Kind regards
Tony

Right after listening to all of you knowledgeable people on here and doing internet research, I am going to bin the idea of using my already purchased 20 Li-ion 5000mAh 26650A.
So anybody wanting these unused batteries and the unused still in the anti-static cover HX-4S-F30A board, people who are in the UK send me a p.m and we can work something out together.
So what I am going to explore is something we all use/charge 12v car battery/s
So if at all possible I would use one or two of my already purchased Stepper motors to charge X amount of 12v battery/s mAh to be advised then onwards to my pure sine wave Inverter 1200w, I can either build or purchase.
The reason why I propose to use 12v batteries is because I can successfully charge them without the risk of explosion/fire, we have all charged our car batteries at some point in time.

sheffieldyorky said:

The reason why I propose to use 12v batteries is because I can successfully charge them without the risk of explosion/fire, we have all charged our car batteries at some point in time.

Click to expand...

Just make sure to do charge them a well-ventilated area because charging can generate hydrogen gas if not well controlled. Or use sealed lead acid batteries (SLAB) which have much better charge retention (lower self-discharge), if you need that.

I don't know how efficient or effective those stepper motors would be as generators (alternators).

What speed are you expecting them to be run at?

rjenkinsgb said:

I don't know how efficient or effective those stepper motors would be as generators (alternators).

What speed are you expecting them to be run at?

Click to expand...

Hi there
After visiting the Stepperonline website I have found this
I don't know if that is what you need.
These are my Stepper Motors

• 34HE45-6004S 6.0a 8.2Nm
• 34HE45-6004S 6a 12Nm

I've already looked at those.

If you are intending to use a motor as a generator, you must know what will be driving it, and with what speed or speed range?
Also, what power (eg. watts or horsepower) will be available to turn the motor?

rjenkinsgb said:

I've already looked at those.

If you are intending to use a motor as a generator, you must know what will be driving it, and with what speed or speed range?
Also, what power (eg. watts or horsepower) will be available to turn the motor?

Click to expand...

Hi there thanks for replying to my thread.

Regarding speed/speed range, surely I am governed by the Stepper Motor itself. I can’t change the speed at which the Stepper Motor rotates. So having said that if I could make a bracket and install say a combustion engine for the Stepper Motor with the rotation of the engine pulley wheels it would then charge the battery and then onwards to my inverter.
So having said that how do I make it rotate if it is not with a combustion engine ?

UNIT 1) the maximum power would be 1200w required by my inverter.

UNIT 2) the minimum power would be 800w required by my inverter.

sheffieldyorky said:

Regarding speed/speed range, surely I am governed by the Stepper Motor itself. I can’t change the speed at which the Stepper Motor rotates.

Click to expand...

If you are driving it mechanically as a generator, rather than electrically as a motor, the speed is purely what the mechanical system runs at!

If you are going to use an engine, a normal three terminal vehicle alternator would be far better as those are designed for battery charging and have the rectification and regulation included.

rjenkinsgb said:

If you are driving it mechanically as a generator, rather than electrically as a motor, the speed is purely what the mechanical system runs at!

If you are going to use an engine, a normal three terminal vehicle alternator would be far better as those are designed for battery charging and have the rectification and regulation included.

Click to expand...

Hi there thanks for replying to my thread.
Went onto eBay and searched for a small engine, but none was suitable, then searched for a Honda suitcase generator but there is no way I am paying that kind of money it will take years to break even.
All that I want to achieve is finally power the inverter (pure sine wave) 1200w max
I am moving away from my Li-ion batteries and seriously considering a 12v vehicle battery or a 12v leisure battery.
When the leisure battery is showing low capacity then I would charge this battery via the inverter and at the same time use my 800w appliance but when not charging the battery I would use the inverter for my 1200w appliance.
The 1200w would only be used sporadically.
At no time would I overload anything, once built (battery charger & Inverter) I would then use one inverter solely for 1200w & the other for 800w.
So what do you suggest, I would rather build than purchase outright.

You must be capable of understanding how a purchased system works and each component works in order to design one.
It's like watching the Olympics and thinking you can compete after seeing what others can do without the training, knowledge and experience.

e.g., Gr X11 Physics, how much energy, torque, and RPM are needed for your specified optimal motor/generator to charge a battery at 1 kW with a 50 Ah capacity from 0 to 100% State of Charge?
How much energy is lost in the process? ( or how to calculate it?)

You can get a new clone of a Honda GX series engine on ebay for less that £100.

Rig up a base for the setup and run a small three terminal alternator with a belt drive and a big pulley on the engine, and use a 12V deep cycle / leisure battery for the power storage.

Even at eg. 100A at 15V from the alternator, that would only be 1500W or around 2hp; the engine would running at quite light load.

I've worked on one of those engines, they are pretty good, with an easy-starting system.