New 16-cell Battery Management System (BMS)

[bobmcree]

i believe he meant what "peak voltage do i use for a123 charging?" and the answer is any voltage you want between 3-4v most people use 3.65v

 

[bobmcree]

Yep, that there scheematic looks right to me! :wink: j/k

Wow! I cannot believe what you guys are able to come up with. This is very impressive indeed. It's way over my head, but still, I can be impressed by it.

I think you guys should take your wives out to dinner and a glass or two of wine since you are tinkering too much!

this kind of stuff comes pretty easy when you don't sleep anyway we have a 2 lb 100v 100Ah battery in the works next but it may take a bit longer...

 

[Deepkimchi]

Hello Bob,

What kind of sleep problems are you having? Remember Xyster seemed to have it too.

My brother swears by Melatonin. I try to think about ebikes when I have trouble sleeping. I'm almost 51, and have PTSD from something I can't talk about (things that went boom). A shot of Cognac helps too about 1/2 hr before bed. Working out at the gym helps relieve stress. Going to bed at a fixed time, not doing anything else but sleeping in bed (besides that other thing), watching caffeine intake such as coffee/sodas (avoid late afternoons), may be some things that help.

DK (an American in S Korea, not Paris) :wink:

 

[jeffkay]

What I meant was this: The cutoff voltage is say 2.7 or 2.5v. After the BMS/CMS device does its cutoff, if the load is removed, the cells should be at some voltage of rest--what is that? It is probably in a range of 3.00v?

"Serious watt hours"... Yes, "Deep Cycle" is a full size commuter motorcycle conversion. Originally a 1973 Yamaha 750cc, it uses a first gen Etek and an Alltrax set for 150 amps. I have been reconfiguring the packs and now have 4 packs with 4 sub-packs of 16s12p. I drove the heavy bike and heavy rider (!) the other day with 3 packs (36v nominal) and it went over 14 miles on very hilly route. It is geared to be about 7:1. The 4 pack estimate should get me 19.5 miles or more on the flat. Speeds with that pack have reached 50mph but realism dictates about 40-45mph. It is a blast.

I have charged the 12p sub-packs in under 20 minutes using my 80 amp Vicor supply! Yes the charge wires (6ga.) get hot!!!

Jeff K./ D"Deep Cycle"

 

[bobmcree]

What I meant was this: The cutoff voltage is say 2.7 or 2.5v. After the BMS/CMS device does its cutoff, if the load is removed, the cells should be at some voltage of rest--what is that? It is probably in a range of 3.00v?

that voltage or higher, yes. what typically happens is that you will hit the lvc under heavy load and the system will cut out, then when the load current drops and the voltage rises above cutoff + .150V the low voltage signal goes high and either releases the ebrake signal or cuts off current to the load, which immediately clears the lvc and restores power, then if you reduce the throttle you usually have 10% or so remaining capacity you can still use at a lower throttle setting.


if that doesn't answer your question i will try again...

I have charged the 12p sub-packs in under 20 minutes using my 80 amp Vicor supply! Yes the charge wires (6ga.) get hot!!!

Jeff K./ D"Deep Cycle"

that's the reason we put the 8A current limit in the spec. when the first shunt starts to conduct the current is reduced,but the full charge current still needs to go through the cutoff fets, and with .002 ohms from a pair of 4110s it should be possible to use higher currents, but we need to put a limit somewhere or somebody will try to run 80A which would be 6.4W in the cutoff fets, still manageable but a fair amount of heat.

 

[GGoodrum]

What I meant was this: The cutoff voltage is say 2.7 or 2.5v. After the BMS/CMS device does its cutoff, if the load is removed, the cells should be at some voltage of rest--what is that? It is probably in a range of 3.00v?

"Serious watt hours"... Yes, "Deep Cycle" is a full size commuter motorcycle conversion. Originally a 1973 Yamaha 750cc, it uses a first gen Etek and an Alltrax set for 150 amps. I have been reconfiguring the packs and now have 4 packs with 4 sub-packs of 16s12p. I drove the heavy bike and heavy rider (!) the other day with 3 packs (36v nominal) and it went over 14 miles on very hilly route. It is geared to be about 7:1. The 4 pack estimate should get me 19.5 miles or more on the flat. Speeds with that pack have reached 50mph but realism dictates about 40-45mph. It is a blast.

I have charged the 12p sub-packs in under 20 minutes using my 80 amp Vicor supply! Yes the charge wires (6ga.) get hot!!!

Jeff K./ D"Deep Cycle"

Ah, okay, now I know what you mean. With so many a123 cells in parallel, the voltage drop is minimal, all the way up to when the cells are pretty close to being fully discharged. If the cells are pretty close, they tend to all dump at once. You don't get much notice. Because of this, the cells will have resting voltages up close to 3.3V per cell, even up to when there's less than 10% capacity left. When they do finally dump, the voltage drops off pretty quick. Because of this, what the LVC need to do is detect this drop as soon as possible, which is why we used the 2.7V TC54 versions in the LVC circuits that are used with a123-based packs. With LiFeBatt, and other LiFePO4-based cells, you can actually feel a slight difference towards the end of the capacity, so the 2.1V version of the TC54 seems to be perfect. I have driven my LiFeBatt packs down to when the cutoff trips, under a big load, and what happens is that you will feel a quick "hit". If you keep the load on, it will hit again, about a 1/2 second later. If you back off the throttle, this oscillation will stop, and you can go about another couple of miles, with a lower load. Eventually, any throttle at all will cause this oscillation. At this point, the WattsUp says I've used about 9.8Ah, which is about what it takes back in.

-- Gary

 

[bobmcree]

Hello Bob,

What kind of sleep problems are you having? Remember Xyster seemed to have it too.

My brother swears by Melatonin. I try to think about ebikes when I have trouble sleeping. I'm almost 51, and have PTSD from something I can't talk about (things that went boom). A shot of Cognac helps too about 1/2 hr before bed. Working out at the gym helps relieve stress. Going to bed at a fixed time, not doing anything else but sleeping in bed (besides that other thing), watching caffeine intake such as coffee/sodas (avoid late afternoons), may be some things that help.

DK (an American in S Korea, not Paris) :wink:

Thanks DK, the major factor in my sleeplessness is pain from a severe back injury. i already take enough narcotics to kill a horse, and i can't just keep increasing the dose because of the side effects. i agree about the melatonin, it helps a lot. I had a spinal fracture from falling off the roof of my tour bus when i was up there tying off some luggage after river rafting in the snake river in idaho. i could make it more interesting by saying i got hurt river rafting, but the truth is not quite so romantic.

 

[rarebear]

Hello Bob and Gary!!

Congratulations !!!!!!!!!!!!! very impressive!

My question: (12 cells LiFeBatt)

Is the LVC realy needed when i set my programmable controller to a safety LVC (28V?)

I would like to use your:

"Charger Management System (CMS) as an external board/unit that would sit between the output of a standard SLA charger, or a regulated power supply, and the pack, connected to the latter via a special 18-pin plug."

Is your 12 Cell CMS (external board) also available? or only the BMS board with LVC?

I will use two of yours LifeBatt 12 Cells Packs in a high speed application (wired in series)
and in a long range application (wired parallel)

I also want to quickcharge it with a 20 amps output SLA charger. (Is it possible?)

Any suggestions?

Please help!

Thank you!
Albert

 

[bobmcree]

Hello Bob and Gary!!

Congratulations !!!!!!!!!!!!! very impressive!

My question: (12 cells LiFeBatt)

Is the LVC realy needed when i set my programmable controller to a safety LVC (28V?)

depends on whether your cells stay balanced. i feel it is cheap insurance on expensive cells to watch each one or each parallel group

I would like to use your:

"Charger Management System (CMS) as an external board/unit that would sit between the output of a standard SLA charger, or a regulated power supply, and the pack, connected to the latter via a special 18-pin plug."

you can use this system that way just with longer wires and an 18 pin molex connector which i believe gary has

Is your 12 Cell CMS (external board) also available? or only the BMS board with LVC?

you would have to use the complete board and just not stuff the lvc parts

I will use two of yours LifeBatt 12 Cells Packs in a high speed application (wired in series)
and in a long range application (wired parallel)

I also want to quickcharge it with a 20 amps output SLA charger. (Is it possible?)

the shunts can only handle 8A , but when the shunts activate the charge current is reduced, so the shunts do not have to carry all the current, the lvc circuit does if it is used, and if the charger has the proper output voltage of 3.65v per cell plus a half volt or so for fudge factor, and not so much that there is excessive voltage across the fet that limits the charge current. we really do not intend the system to handle that high current, but it is possible since the high current only goes through the cells if the low voltage disconnect function is omitted and the ebrake signal used instead. even at 20A the dissipation in the fets would be just a watt or two, but the pcb traces are not intended to carry that much current. beefing them up with extra solder would probably make it possible to run at 20A but we have to draw the line somewhere for warranty purposes.

 

[bobmcree]

As i said before, the LifeCycle BMS (my idea for the name - not connected with LifeBatt except that i am also US distributor for their cells for e-bike applications) is not perfect. I felt that we could not bring a PIC based product online that was reliable for at least another month or two, and every day we have been getting requests for complete systems including bms and charger. Lifebatt has now finally come out with their own system, and i am about to start testing it. I will be using that vms system and the LifeBatt 8A charger on the system i am putting together for Jim Parker of Cruzbike, as that is the only way to get him the promised 3 year warranty. The LifeBatt system is certainly more sophisticated than mine, but does not have exactly the same functions, so it is up to the user whether to buy a complete LifeBatt "hard pack" system and get 3 years, get raw cells and get 90 days, or somewhere in between by using our system and or charger. Gary has secured an agreement with Soneil to customize some 4.5A chargers that he will be able to offer at a good price.

A few notes on the design; it has been described as "brute force", and i suppose that is valid from the viewpoint of the wasted power, simple minded control system, and very high parts count, but i would describe it as just the opposite. We are treating the cells as gently as we can by assuring that the cell voltage never exceeds 3.65v or another user-variable setpoint from 3-4v, and we are reducing the charge current when near the endpoint to assure accurate measurement without the voltage drop of the wiring interfering. It has been said that the component count is too high. The shunt circuit could be a simpler if the pot was replaced by a resistor, but there is no simpler method i have found for achieving the degree of control over cell voltage this provides. If the logic section is left out it can be used with just the shunts and a charger that cuts off at the total shunt voltage, as long as the heat sink is big enough to handle the power dissipation. The LEDs and associated drive circuitry can be eliminated if desired.

The current reduction circuit could be changed to pwm, but i wanted to maintain the capability to use existing sla chargers insofar as is possible, so i wanted almost no voltage drop in the charge path, and .004 ohm drop of the fet used will be pretty close to none with the circuit the way it is. anybody who wants to could replace the fet and op amp circuit with any other type of current regulator that can handle the task, provided you provide the required control inputs to drive it on or off or regulate. Generating the logic signals from 16 channels to tell when none, any, or all are on could have been complicated and would require a lot of i/o pins on the PIC, but instead i did it with 32 2 cent diodes. (1 cent in qty 1000). the one shot that generates the delays is accurate enough to provide the delays required, though of course a PIC could be more accurate.

To achieve the kind of low voltage protection the system provides with a dedicated TC54 for each cell costs less than a dollar a cell in parts, but permits us to perform this vital function drawing only 1 microamp from the cell while not charging. This real-time system also provides warning by cutting power at full throttle then immediately restoring it when the throttle setting is reduced. This provides ample warning to get to a safe place to stop without abruptly cutting power, while still providing excellent protection against over-discharge. There is no way a microprocessor based system could sample each cell at an adequate rate and resolution to provide a matching function without capability that would make it too expensive.

The LM431 shunt regulator IC is comprised of an accurate voltage source, a low current comparator, and drive circuitry so it is pretty well integrated, as is the darlington output stage. both of these are common 50 cent parts. The pot setting the clamp voltage could be replaced with a fixed value but that would result in about a 5% possible error which can be reduced to the accuracy of the meter used to measure it and he setting will drift of <1%. over the expected temperature range.

Every part in the design was carefully chosen with cost and reliability weighed along with simplicity and the idea of creating a kit that the user could understand and learn from while they are building it. Hopefully putting together the bms will help users become better informed about the use of their expensive battery systems, and we can help them to get optimum performance. The design is too complicated to make money on it but that does not mean it is not a valid, useful design. If it makes it possible for us to offer a complete solution to our users the profit on the bms is secondary to its preventing a landslide of battery failures while still under warranty a couple of years down the road.

We made the schematic public so the tinkerers could play around with it and customize it to suit individual needs. If the guys working on a PIC based BMS come up with something workable that is less expensive i am all for it. Right now i just don't have time to follow that thread. Spring is coming and it's time to get to work if we are going to have a garden.

 

[fechter]

You're obviously on the right track there Bob. You have something that actually works and way out performs any of the other commercially available BMS circuits I've seen (mostly RC stuff).

Sure, there will always be room for improvement with any design, but it's important to do actual testing and observe the behavior before you can refine things. Your observations in the difference in charging time vs. shunt current, for example, are good lessons. Not everybody wants the same thing either. I can buy a "duct tape" BMS from Ping for $43 plus shipping from China, but that's not really what I want.

The PIC thing is very complicated and will take quite a while to work out. I also have an inherent distrust of anything that runs on software (too many years of dealing with Microsoft). Actually, we use a huge number of PIC based devices in the hospital, and I've seen what can happen if the code is not perfectly written. Some redundancy and fault tolerance needs to be worked into the software. I think it can all be done, but it will not be so easy and it's yet to be seen if there would be any cost savings.

Eventually, the chip manufacturers will start making parts specifically designed for LiFePO4, but right now, they only support Li-Co. If all the stuff that is duplicated for each channel was built into a single chip, that would certainly make life easier.

 

[GGoodrum]

I started out life programming in assembly/machine language for computers that went in fighters and helicopters, so I'm all for using PICs, where I think they can work. I'm not sure, in this case, whether it makes all that much sense to have it try and do everything, when a few inexpensive parts can do the job just fine. Certainly adding functionality, like logging error conditions, more useful displays, like a "gas" gauge and/or incorporating WattsUp/CA functionality, would be good reasons for using a PIC-based design, but even there I think using dedicated low voltage detection chips, and LM341-controlled shunts is still a better way to go. With this "combo" appraoch, you could eliminate having individual LEDs on each channel, and all the drive logic that goes with it. We are presently combining the opto outputs from the LVC detection and shunt on detection logic, basically into three signals, one for any LVC tripping, one to say that at least one shunt is conducting and one that says all the shunts are conduction. With a PIC, you could have it monitor each LVC and each shunt, so that it can use this extra information for added functionality.

In any case, what we have does, in fact, work. By keeping it simple, we've made it very reliable, but still have the right sort of basic functionality, which is to protect the cells from being over-discharged, and to ensure that each cell can get a 100% charge, even using standard SLA-type chargers.

I'm still working on the test and assembly documentation, trying to make this as simple as possible. Hopefully, this effort will be complete today, so that I can make the kits and assembled versions available starting tomorrow.

-- Gary

 

[bobmcree]

You're obviously on the right track there Bob. You have something that actually works and way out performs any of the other commercially available BMS circuits I've seen (mostly RC stuff).

Sure, there will always be room for improvement with any design, but it's important to do actual testing and observe the behavior before you can refine things. Your observations in the difference in charging time vs. shunt current, for example, are good lessons. Not everybody wants the same thing either. I can buy a "duct tape" BMS from Ping for $43 plus shipping from China, but that's not really what I want. /quote]

thanks fechter, it means a lot coming from a working fellow engineer. the circuit could be described as firing a shotgun at a bluebird, but the argument is that if you really want to hit it a shotgun is a better choice...I built one of the Popular Electronics Altair 8080 home computers in '65 that you programmed with switches and graduated to a paper tape 6800 then pdp 8 to 11/20 to 11/34 to vax 11/780 then to CRAY, then followed the stairway back down to reduced instruction set (RISC) and PIC (programmed instruction control - a Microchip trademark) chips that perform functions we only dreamed of when we built the first MRI machine powered by a 6802. You can do a lot these days with a PIC but the code still has to be written by a human. With this all-analog design if you want to change the time that the cells are held at the peak voltage you just change a resistor or cap, and if you want to get a bit of extra runtime out of your cells by charging them up to 4.00 instead of 3.65v or maybe get some extra service live by charging them just to 3.55v, you can achieve either with a simple pot adjustment.

instead of going in to the software to vary the current during the final phase of the charge cycle a pot is provided to adjust it from a few hundred ma to a couple of amps. Each individual user has the ability to tailor the system to suit their needs. Of course to maintain warranty the values must be set to the factory recommended levels.

if people just want partial function they can just not stuff some of the parts. I agree that a patent is only worth what you are willing to spend to defend it, so i did not even consider the idea. i really doubt there is anything worth patenting in the design, and i would not want to contribute to the idea that there was. Gary and i did spend a fair amount of time assuring that the design works as intended, and we are still today finishing up the procedure for test/assembly for users who want to buy kits.

i heartily recommend the kit as a way to gain a better understanding of what the bms does, what your battery does, and how to assure the maximum service life from your battery. We are finishing up the procedure today, Gary of course doing most of the work while i sit here with a bloody mary and help him through the magic of satellite technology ;') don't get jealous quite yet, i expect to see some profit from this endeavor just about, uh, never.... but it is a fun and interesting way to keep busy.

 

[fechter]

Excellent Bob.

I was snooping around at datasheets this morning and ran across something interesting.
The MAX6436. It does both high and low voltage points on a single chip, and both points are adjustable.

As you pointed out earlier, if someone was going to buy 1000 pieces, you could get a fixed voltage monitor made to the exact right voltage and save some resistors. The MAX6432 or somewhrere around there would do both high and low points with preset voltages.

Both of these are surface mount only, so will have to wait until the next generation.

 

[Ypedal]

Curious question.

Can circuit boards be " Doubled up " if one wanted to double the current capability ? or does that create assembly nightmares ?

And personal opinion on the KISS method ( keeping it simple but get the job done ) i agree and support fully.. as long as it works.

Like the crystalyte controllers.. the old style is now understood by the general ebike maniacs, like those on this forum, fixing, modding, troubleshooting is possible by the average joe like me with a soldering iron with help from EE's like Fechter,Bob,etc.. it's all Win Win.... then we get V2 with a whole new set of problems and it starts all over again.

Those with a bit of money who can afford the battery packs, likely won't mind spending an extra 100 or 2 for a complete " Battery Pack Solution ".. And i can finally offer a high-priced but trouble-free battery pack solution that won't keep me up at night worring about lying warrantee claims and problematic complex battery problems....

Unlike every dissapointing battery purchase i've had the pleasure of " learning " from.... this one so far sounds great... I hope i'm right in real life ! Only time will provide that answer.

 

[bobmcree]

you can parallel first and use one bms if you keep discharge within the limits of the cutoff fets or use one bms for each serial string and connect them together. i think for proper operation you would need a schottky diode at the + end of each pack but there may be a way around that. with the diodes it would be possible for each parallel string to cut out independently when any cell hit the cutoff point and the rest of the strings would continue to power the load. this process would continue until the current capacity of the remaining strings was exceeded. cool, eh?

 

[knoxie]

Hi Chaps

I'm with you on this one Bob, keep the PIC out of it, they are great devices when used properly of course but it just makes things more complicated, the pure analogue approach you have there is much more flexible Bob, here in the UK you could get the boards assembled in batches very cheaply, runs of surface mtd boards aren't too expensive either although you would need orders to make it a risk free investment.

Justin from e-bikes ca would be the man to speak to about SM manufacture, the Life packs you are sorting out really do look the business, the pack failures that I have seen have all been down to the BMS failing, a nice feature for the plug and play user would be some indication that the battery capacity was low, this cropped up quite a lot with customers using Point-1 packs, they didn't like the fact that they could be at the end of a ride and the BMS would cut the power when they pulled across an intersection, now you cant cover all events with any BMS or monitoring system however letting the user know its getting low would be a good idea, I know this would be tricky to implement with this technology as the potential in the cells stays high almost to then end of the discharge.

I would encourage anybody using any e-bike to get a watts up as a minimum, I still use a simple bar led meter made by 4QD, its a brilliant tool for gauging the life left in the cells, I use it on my NIMH pack (NO BMS) there of course! my watts up meters come in to their own on long rides with the Lipos, using them I never trip the BMS as I always leave enough juice in the tank.

Anyway I am rambling, I cant wait to see the packs and the batts flying off the shelf and I really doubt there will be any problems and to anybody reading this thread you simply couldn't deal with a more straight up and honest guy than Bob, I have been shipping bits from him to the UK for a couple of years and he has stood behind everything he sells 110%, a couple of motor controllers blew and Bob sent me new ones straight away no question!

I hope you can make enough from the packs to make it worth your while (that goes for the both of you), best of luck!!

Knoxie

 

[bobmcree]

thanks for the vote of confidence, paul. we all try to do our part to make this a better place to live and i feel this is some small part of me doing my part. i wanted the design open source so it would support the idea of electric bikes in general; an idea whose time has clearly come. Nobody needs to go over 30 mph on an ebike (except you and i of course, and then only for 'testing' We need the capability to go that fast to stay our of trouble (the cops did not go for this argument either when they pulled me over in the vette.

in order to assemble the LifeCycle BMS a decent meter and a variable supply are required. since not everybody has a supply and i could not find a cheap alternative, i put together a kit which can be found in a thread higher up in the endless sphere menu. i got a good deal on a truckload of transformers years ago, and still have some left that are quite suitable for this purpose. email me for details, $29 including shipping for 0-20v@2A and another $10 for a 3 1/2 digital lcd meter. i need a $1 deposit from 10 guys to build them, otherwise the deposits will be returned.

 

[OneEye]

The variable power supply is used to set the trim-pots and refine the maximum charging voltage for each cell. You could calibrate it with a battery and a voltmeter, but it might take a lot longer to make sure you have it set correctly.

 

[bobmcree]

The variable power supply is used to set the trim-pots and refine the maximum charging voltage for each cell. You could calibrate it with a battery and a voltmeter, but it might take a lot longer to make sure you have it set correctly.

a battery would not really be good enough to use for calibrating the shunts. ideally you need a supply that can provide exactly 3.65v @ an amp or more, and the voltage needs to be constant for some time to adjust them all. if you have a low current voltage source like a battery and a pot you could set the voltage but when the shunt starts conducting at an amp the pot will no longer provide the proper voltage. there will also be some voltage drop in the wiring, so you might need to fine tune the shunt voltages with the pots while monitoring the cells directly.

instructions are included for testing the charge current regulation loop with a 12v supply and a 10 ohm 10w resistor. a 12v battery could be used for this if desired.

 

[PJD]

I brought this issue up already in an e-mail to Bob, but I thought I'd bring this up with the community for ideas.

My e-max scooters, and I suspect most street-legal equipped electric scooters and motorcycles, use the +12 volts from the tail light circuit to signal the controller brake cutoff. They also have +48 or +60V logic circuit power wire which is turned on through the key switch which could be used to cut the controller off.

But, the BMS's LVC logic is a "low" for cutoff and "high" for on - or just the opposite of what is needed. (although I'm curious if +12V is actually needed, maybe a +5V logic signal will work too - I should test it)

And simple ideas how to address this? Yes, I could connect the contactor relay negative (rather than the 95 amp pack circuit negative) to the cutoff FETs. But in a LVC condition the relays will be cycling on-off-on under high amp load which they aren't designed to do.

 

[fechter]

You could invert the signal using a transistor.
Another way to tie in the LVC would be to pull the throttle signal down. This should work with most controllers. To be safe, you would add a 1k resistor in series with the throttle signal and pull down on the controller side the same way you tie in a Cycle Analyst.

When the signal goes low, the motor will stop.

 

[bobmcree]

I brought this issue up already in an e-mail to Bob, but I thought I'd bring this up with the community for ideas.

My e-max scooters, and I suspect most street-legal equipped electric scooters and motorcycles, use the +12 volts from the tail light circuit to signal the controller brake cutoff. They also have +48 or +60V logic circuit power wire which is turned on through the key switch which could be used to cut the controller off.

But, the BMS's LVC logic is a "low" for cutoff and "high" for on - or just the opposite of what is needed. (although I'm curious if +12V is actually needed, maybe a +5V logic signal will work too - I should test it)

And simple ideas how to address this? Yes, I could connect the contactor relay negative (rather than the 95 amp pack circuit negative) to the cutoff FETs. But in a LVC condition the relays will be cycling on-off-on under high amp load which they aren't designed to do.

here is a simple inverter that should work. the resistor values are not critical but do not use anything smaller than 10k on the bms side. the pullup resistor to 12v should not need to supply much current if the signal is logic and not a relay. for a relay you might need a power transistor.

 

[manfred59]

Hi Bob,
when, do you think will this wonderful BMS kit be available.
Second question: Would it also be possible to use this kit for less than 16 cells?(like from 4 - 16?)

 

[GGoodrum]

We are still trying to finish the assembly and test instructions, which is the reason for the delay. I'm insisting on trying to come up with ways to test the different sections that won't require anything more than the simple variable 0-12V supply, and a multimeter. We made some changes over the last week, so I wanted to wait for the new boards to show up, which they did. Now I think we can get this done in the next couple of days.

You can use the BMS with any number from 1-16 cells, simply by jumpering over the unused channels.

-- Gary