Removing BMS & wiring in Pl8v2

[grazy+1949]

Hi Guys

I have always been inspired by what Burgerman has designed and built. I have a BDLC Power chair, but as I live amongst steep mountains, it's just plain dangerous, so I decided to build an EV ATV Rover as well. Today I stripped down my 55Ah LiFePo4 battery pack and surgically removed a tumour known as a BMS. Now I am left with a lot of cables that I don't know what to do with.

I have just purchased a 1330w PS together with a Revolectrix Cellpro PL8v2 intelligent charger, along with all the cables and gold plated plugs.

I will put all the salient pics bellow with annotations and hope you guys will guide me with making the correct connections. Many thanks

Too many balance wires from pack?

[grazy+1949]

Where I unsoldered the neutrals from on BMS

[Burgerman]

Too many?

Divide a pack into 8 cells. Theres 1 wire each end. And 7 in between each cell.

Like this where 8 is a cell or group of cells. And I is a balance wire...



I 8 I 8 I 8 I 8 I 8 I 8 I 8 I 8 I

OR

http://www.revolectrix.com/support_docs/item_1377.pdf

[grazy+1949]

Internal wire of LiFePo4 pack

How to wire the battery internal cables to a D-Sub cable?

[grazy+1949]

Solder points for neutral return cables

[grazy+1949]

Base of pack

[Burgerman]

You are making it all look complicated.

You need ONLY 9 balance wires and you can even plug those straight in with this https://www.banggood.com/PL8-PL6-Spare- ... rehouse=CN

And tho heavier wires to drive the chair/charge the battery.
That link above shows 2 SAFE 4mm connectors for the charger. (as in you cant short them out)

Thats all you need. The BMS, its sensors, and all the rest can go in the bin.

[grazy+1949]

[Burgerman]

This is a 12V or 4S battery. So 5 balance wires.

[grazy+1949]

How many volts is the Pack Negative going to the D-Sub cable?

[Burgerman]

Like all battery neg wires its 0

LOOK at the image above. Al wires connected to that neg wire all zero volts... So, 0 Then 3.2, 6.4, 9.8, 12.8...
All worse connected to the plus are 12V

You are making it way more complicated than it is.

[grazy+1949]

Yes thanks for helping me until 4am this morning (Span.). I slept on it and now I've grasped it. I have 9 white wires + some spurious ones that are redundant wires for the BMS sensors. Of the 9 wires . 1 of them goes to bat. pos. and 1 goes to bat. neg. So that leaves the 7 that go to the PL8v2 balance port.

I will solder those to a balance cable and then , I'll need help with the extra wires that go to the D-Sub plug.

best regards

[foghornleghorn]

So that leaves the 7 that go to the PL8v2 balance port.

9 go to the balance port.

Wires don't care what colour they are but for the sake of understanding

+ RED
WHITE
WHITE
WHITE
WHITE
WHITE
WHITE
WHITE
- BLACK

[ex-Gooserider]

This is a case for either physically tracing the wires, or using a meter...

Ignore everything that went from the outside world to the BMS, the objective is to replace all that with connections to the chair and to the PL8 charger.

So you should have two heavy wires coming from the chair controller, which will be the plus and minus on your 24V input for chair power.

Then you will need two heavy charging wires and 9 light balance wires going to the PL8 (with the DB connector pair in the middle)

From the picture, it looks like you have sets of several heavy wires on the plus and minus side that are all in parallel - tie all in each set together and connect to the chair power and the charge wires of the PL8.

You then need to figure out the correct order for the 9 balance wires - if using a meter, you will find one that is at ground (0VDC) and then each will be about 3V higher - 3, 6, 9, 12, etc... These MUST be in the correct sequence going from the pack to the PL8 - see the earlier pictures....

As long as you use the same sequence on both halves of the DB connector, it doesn't really matter which wire goes to which pin, but it is a good idea to use the same pin numbers as the balance plug on the PL8 - there is no real standard, but that's as close as we get.... (just remember that there is NO guarantee that anyone else's setup will be the same, so don't borrow anyone else's gear without verifying how it's wired)

If there are more wires coming out of the pack, you may want to either figure out what they are, or ignore them (but either remove them or insulate the ends so they can't short anything out) Just guessing but you may have had some temperature sensors to tell the BMS to shut down if things overheated... The PL8 doesn't have any inputs for temperature sensing, so they aren't much use - if you wanted some entertainment you might try hooking them up to some sort of display, but that is VERY optional (I wouldn't bother...)

ex-Gooserider

[grazy+1949]

Hi ,

Thanks for a very well written , clear and easy to follow description of how to wire the battery pack to the PL8 & the chair. Much appreciated.

I didn't do any work ,as today was a pain day. Perhaps I'll go for it and get the D-sub all wired up tomorrow. I should do, as our lounge looks like a terrorist bomb factory, with both the dining and coffee tables full of tools and of course this weirdly configured battery pack. BM called it right when he said I was making it more complicated than it actually is. | Instead of trying to work out what all this BMS detritus was, I should have focused on which cables are actually required.

Thanks for your explanation on what to do with the 4 red and 4 black cables coming from the pack. I was uncertain about how to negotiate them.

[grazy+1949]

Hi All

A lot has been achieved. We have chopped out the BMS system from the Lipo pack and thrown it where it should be , in the bin.
With the help of my son and 3 x 3 hour soldering sessions with crap materials, we were able to solder the 13 cables/wires that run from the battery. We tested to order of the balance wires near the nd of the job and we had reversed the position of 2 wires . So we corrected that.
We did a balance charge on the 24v 72Ah pack @ 20A and the volts went yp to 29.9v. With the old charger it would only reach 26.5v

Fuel: We got a message saying "Fuel Level 18 %" I have no ides what that might mean??

I am very happy. I feel I have learned a lot and now have a pack that will reliably get me around town,

I have an ex Silicon Engineer in the States currently calculating the power I will need from my new battery pack to do the 7 km climb to the next mountain village. I have a feeling that he will be advising: 48v 120-180 Ah pack, with a specific cell "C" rating for my particular duty cycle.


grazy1949

[Burgerman]

ALL WRONG!!!
There are NO stock presets that will work properly.
Worse you are charging it to way too high voltage!!!

You have all the thing set wrong. Your lithium battery is LiFePO4 8S and its charge voltage should reach a MAXIMUM of 28.80V or rather 3.600V per cell, and fuel doesent work, its for lipo. Thats supposed to be turned off.
YOU are charging it with incorrect settings and as a lipo which it is not!!!

STOP doing anything. You are ruining your cells.

And use the PC to update firmware to the newest one, and then load THIS preset with the correct settings.


REMOVE .ZIP FROM THE FILE NAME. IT IS NOT A ZIP...

[Burgerman]

I have an ex Silicon Engineer in the States currently calculating the power I will need from my new battery pack to do the 7 km climb to the next mountain village. I have a feeling that he will be advising: 48v 120-180 Ah pack, with a specific cell "C" rating for my particular duty cycle.

He wont have a clue. Far too many variables. Even if he knew all of them which isnt possible the correct answer is still wrong because it depends how hard you want to work the batery or leave in reserve. And the following day all the parameters chage.

[grazy+1949]

Hi BM

Despite all the valid points you raise. I am in an expensive test and development program. Why! because I am paraplegic and the highlight of my day is often to drive myself in an EV Rover, in the open air and just enjoy the freedom and the beauty of nature at the top of the nearest mountain where the views are to die for. When I succeed with my objective in a sustainable manner, others who have mobility issues, yet are still adventurous, will benefit from the work of my team members. It is one of my passions in life. We WILL eventually get there in the end. Yes packs and motors will fail on us along the way. That is the cost of breaking new ground.

I have talked to EV designers worldwide and nobody I have talked to has a clue on what is required to get a gross weight of 200 kg up 7 km of 20% to 30% climbs (sustainably) and that includes you of course BM. We will do it BM. We are not going to give up, because engineers don't want to commit themselves to a spec. We WILL find an engineer who will run the necessary simulations and advise on the degree of over design in order to build into the algorithm that gives us the solution.

I started as a clay modeller for Ford in 1970. I have worked on the design of petrochemical plants for Stone and Webster Engnrg. I have worked in Marine Design and Development. I have worked as a Design Consultant at: Audi, Lamborghini, Citroën et cetera. I have faced many challenges and overcome them. I have absolutely, no doubt that my team and me will find the solution to this problem. Why? Because we have open minds and are positive thinkers. BM, perhaps you will bring something positive to the table to help us create something truly new. A world first ????


grazy1949

[grazy+1949]

ALL WRONG!!!
There are NO stock presets that will work properly.
Worse you are charging it to way too high voltage!!!

You have all the thing set wrong. Your lithium battery is LiFePO4 8S and its charge voltage should reach a MAXIMUM of 28.80V or rather 3.600V per cell, and fuel doesent work, its for lipo. Thats supposed to be turned off.
YOU are charging it with incorrect settings and as a lipo which it is not!!!

STOP doing anything. You are ruining your cells.

And use the PC to update firmware to the newest one, and then load THIS preset with the correct settings.


REMOVE .ZIP FROM THE FILE NAME. IT IS NOT A ZIP...

Hi BM, I will take all this info on board and charge the pack according to your advice. I'll download the correct firmware now. Thank you.



grazy1945

[ex-Gooserider]

You are sort of right about it being possible to come up with a 'spec' but it also is a bit of an exercise in futility as BM says... There are a huge number of variables, which he just mentions a few of...

As folks that don't have the somewhat easy option of hiking down the road to the gas station when the vehicle craps out, we basically have to plan either our trips or our vehicles to NEVER run out of 'gas' - aka charge...

So the basic requirement has to be set all variables to 'worst possible' and spec to handle it... Couple this with the fact that in order to get the best life out of your batteries (either lead or Lithium) you want to keep the C-rate and depth of discharge as low as possible, and you end up with our rule of thumb - namely stuff as many Ah of battery into the thing as you can make fit and keep the size reasonable... On a power chair, that is usually optimized as two group 24 lead bricks in volume - and if going to Lithium keep the same physical dimensions and stuff as many Ah worth of cells into it as possible to keep the C-rate on the pack down (and get the increased range as a bonus...)

And simply looking for 'as big as I can fit' gets around needing to worry about a lot of those variables....

ex-Gooserider

[Scooterman]

And simply looking for 'as big as I can fit' gets around needing to worry about a lot of those variables....

ex-Gooserider

That's what I've gone for!

I want to do some over night road trips in the summer and having big lithium should give me the option of not HAVING to recharge overnight if I can't get access to mains power. Although with the PL8 and 40A+ power supply I might be able to blag at a garage to let me plug the scooter in for a for few hours.

That's given me another thought. Can a lithium charge be interrupted before the cells are fully balanced, and the mobility device used? Obviously it's not something one would want to do, but may have to in an emergency or mains power outage.

I'm guessing it won't matter that much as cells become unbalance as they're being discharged? Any thoughts BM?

[LROBBINS]

If you have your car along, you can also run the Pl8 off its 12V.

[grazy+1949]

You are sort of right about it being possible to come up with a 'spec' but it also is a bit of an exercise in futility as BM says... There are a huge number of variables, which he just mentions a few of...

As folks that don't have the somewhat easy option of hiking down the road to the gas station when the vehicle craps out, we basically have to plan either our trips or our vehicles to NEVER run out of 'gas' - aka charge...

So the basic requirement has to be set all variables to 'worst possible' and spec to handle it... Couple this with the fact that in order to get the best life out of your batteries (either lead or Lithium) you want to keep the C-rate and depth of discharge as low as possible, and you end up with our rule of thumb - namely stuff as many Ah of battery into the thing as you can make fit and keep the size reasonable... On a power chair, that is usually optimized as two group 24 lead bricks in volume - and if going to Lithium keep the same physical dimensions and stuff as many Ah worth of cells into it as possible to keep the C-rate on the pack down (and get the increased range as a bonus...)

And simply looking for 'as big as I can fit' gets around needing to worry about a lot of those variables....

ex-Gooserider

Thanks I see what you mean and will take your advice on board. The firmware is not running on my PC during charge. Can you please send me a link to the correct shareware and or firmware. Many thanks.

[grazy+1949]

If you have your car along, you can also run the Pl8 off its 12V.

Hi

As BM has rightly pointed out, I still haven't learned how to use the PL8v2 correctly. I need help on installing sw/firmware and vitally, I need to learn how to set the presets. BM kindly sent me a link to the PL presets. but I could't open the file.

best regards

grazy1949

[grazy+1949]

ATTACHMENTS
LiFe use this.PS8.zip
(3.17 KiB) Downloaded 3 times

Above is the file I downloaded . I renamed it as BM instructed , but didn't discover how to open it. HELP! Please.



grazy1949

[Burgerman]

May I suggest you read the PL8 instruction manual?

http://revolectrix.com/support_docs/item_1437.pdf

Then, after you read it twice.

Open the PC software, connect the charger and configure everything properly, including the section marked supply And the section marked firmware and the one marked options... And be sure you have 3.33 firmware installed as it is modified by them, for me... So it can charge lifepo4 and lead PROPERLY.

Then go to presets. Choose advanced tick box. And go to file at the top menu. Choose open file to preset one. Navigate to desktop. Click on the file I sent you. But be sure you removed that .ZIP from the file name first. Then presuming your PL8 is connected choose UPDATE to send the preset to the charger...

Then choose graph at the top, and charge the chair from the PC and no need to ever look at or touch the PL8.

I might add, that this is EXACTLY why manufacturers use BMS and cannot fit lithium for the masses. You may have already toasted your pack, if the BMS has not already done that. It is imperative that you completely understand what you are doing. Or it will be one disaster after another. One wrong setting, never mind a wrong chemistry or preset can cause instant ruined pack, or a fire in the other lithium chemistries. DETAILS matter!

[grazy+1949]

Hi BM,

I have had a programmer here today. Following your instructions plus I have read through everything several times. I bought this 72 Ah pack with a 2 year old single seater golf kart. I drove it up my mountain course 12 times and that obviously damaged it due to over discharge.

Stripping this pack down with my son and removing the BMS, has taught me a lot, although I still have a L-O-N-G way to go, before I begin to understand how to employ lithium packs. However I now know that various factors like: Having a monitored display of cell condition during charging with a PL8, having loads of LiFePo4 without a BMS and using BLDC motors, will give me a better chance of success, in tackling my favourite terrain, using electrons, as my power source.

We have now uploaded the presets and got the display on the PC. It shows cell 4 as being approx 2.0v below the rest.

Before the BMS out op. the pack would charge to 26.5v using a 50€ charger. Today it charged to 28.61v. Tomorrow I will road test it on flat roads with some short 20% inclines and see how it performs. It'll be interesting to watch the LOW on the voltmeter. As I've always said, this pack will go in my powerchair and the new pack will go in the single seater rover. Off-road and beach usage will become minimal.

My power chair with its tiny 24v 120w BLDC's and 24v 12Ah LA pack has been doing a 6km return journey with a short 25% climb in it for 18 months now. The AGM batteries are now ready to be replace. The powerchair gives an indication of the fact that given a lot more LiFePo4 + well chosen BLDC's fitted to my Rover, my goal of building a sustainable powertrain is not fantasy.



grazy1949

[Burgerman]

We have now uploaded the presets and got the display on the PC. It shows cell 4 as being approx 2.0v below the rest.

Then you have a massive problem!!!

If a cell is 0.02 outthen thats just ok.
Of its 0.2V out, then its either massively out of balance, or you have a wiring or connection problem or a cell problem.
If its really 2.0V out then I dont know what to say!

Before the BMS out op. the pack would charge to 26.5v using a 50€ charger. Today it charged to 28.61v.

What is important is what the cell balance looks like on screen. And measuring voltage AFTER DISCONNECTION to see a bunch of numbers like 26.something tells you nothing.

You should be charging each cell group carefully to 3.600V and thats a total of 28.80V. If its ever more, you are murdering the battery.
It will frequently be less as the cell voltage will fall to anywhere from 3.55 to 3.45V over the next few minutes or hours, and tells you absolutely nothing.

Tomorrow I will road test it on flat roads with some short 20% inclines and see how it performs. It'll be interesting to watch the LOW on the voltmeter. As I've always said, this pack will go in my powerchair and the new pack will go in the single seater rover. Off-road and beach usage will become minimal.

What does LOW mean?
If the pack sees a LOW under load its too small and you are killing the cells or already have and it goes low because a cell or all of them are now high resistance. If it sees a LOW after some distance its too small and you will over discharge it, also killing its cells. Dont allow any cell to ever go below 2.5V as that will be its end.

[grazy+1949]

When the programmer (Tom) was here yesterday we noticed that 7 cells charged evenly on the graph and the pack voltage was displayed as 28.64v . Unfortunately cell nº 4 was lagging behind on the graph and its plot was displaying 2.0v lower on the graph. I took this to mean that cell 4 needs either repairing or replacing. I took the rover out for an hour today and the voltmeter displayed 26.5v on the flat.

Q) Can I replace cell Nº 4

Tom the programmer used your presets, but they are not saved in Library Presets. I tried to open the presets file you sent me. You told me to remove the file extension. Could you be more specific please as , I don't know what the correct file extension should be. Also perhaps you could explain how to save your presets in the library.

Q) Is it Ok to extend the USB wire from the PL8 around 20 ft , as my PC is downstairs and the EV Rover is upstairs (at the moment my wife is carrying the pack up and downstairs to charge it)



grazy1949