# Open Source BMS



## dimitri (May 16, 2008)

As I told you in the private Email, you make very bold assumptions and your statements clearly show lack of basic understanding of what BMS actually needs to do to be effective, while remaining cost effective. I could have added all those bells and whistles too, but I found thru extensive testing and experience that it wasn't really needed.

So, before you go labeling someone else's work, take some time actually testing your product in your EV and get some real EV miles on it. There is plenty of armchair designers on this forum and all others. Just because something can be improved, doesn't mean it needs to be improved.

As for open source, it was all my work and I chose to make it public to the extent that I wanted. I never promised to make every single detail public.

I am all for free market competition, Jerry. Make a better product, just don't bash something you haven't actually used, only to make yourself look smart.


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## Jerry Liebler (Feb 1, 2011)

I certainly have made many assumptions! A big one is: When a battery manufacturer specifies a maximum charge voltage do the mean it in an absolute sense or do they allow tolerance? My assumption is they mean it with the tolerance of readily available measurement instruments. Thus I chose 3.6 volts +/- 1%. If I should have chosen the absolute maximum I can easily "recenter" the design to 3.6volts + 0% -2%. Another assumption I have made is that an interconnect in a battery pack may become loose and no fire should result, hence the 300 volt DC rated fuse. Another "assumption" is that switching an unclamped inductive resistor WILL result in shorted transistors after a while. This is my experience with over 40 years of building electronics. Regarding cost, a build of 1000 cell modules could easily be sold at $12.50 each and result in a small profit even if the rest of all of the minimum order quantities had to be scrapped.

One holds secrets for ONLY 2 reasons, the knowledge would benefit a competitor or it would embarrass oneself.
Regards
Jerry


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## EVfun (Mar 14, 2010)

The "open source BMS" from Dimitri is still available in the archives. From that anybody could build their own working system, but I doubt they could do it for less than buying them from Clean Power Auto. 

If you have another BMS system in mind share what you want about the design, and for help and input as you wish, sell us on what your system will do for us, and offer it for sale. Some people here want nothing to do with a BMS, some want cell level management, and some want cell level monitoring. Personally, I'm mostly in the last group because I can manage them myself but would like some watchdog letting me know I should do that *now*.

I did have one other thought on the cell loop circuit. Older PB acid regs generally used a normally open system so you paralleled the optical isolator outputs and if any one turned on the system went into action. The problem with that is any break in the wiring looked like an all is O.K. message from the regs. Most of the new Lithium systems have the optical isolators on when everything is O.K. and use a series connection so any break in wiring shows up as a fault and action will be taken. The downside of the NC loop system is the constant slight drain on the cells, usually between 3 and 15 milliamps depending on the system. My idea is a third way of monitoring the cell modules. I was considering a normally open bus with the cell isolators paralleled but with a termination system to monitor for breaks. So you would put a limited current of about 5 to 10 milliamps on the chain of paralleled cell isolators. At the far end of the chain you would have a terminator made of a couple of LEDs or other method to create a measured voltage on the chained connectors. The BMS monitor would be window comparator circuit. All is O.K. only if the voltage stays right around the terminator voltage. At the cell level the drain should be able to be reduced to microamps with most of the power now coming from the 12 volt system which can be easily unplugged.


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## DavidDymaxion (Dec 1, 2008)

Nah, lots of reasons for secrets! Not saying these apply in this case, but there are lots of reasons to not blab everything about a design:


You are pushing a part beyond spec, and are afraid it'll encourage others to do so
You are afraid of emboldening newbies to try something dangerous
You are respecting a nondisclosure agreement with someone that helped your design
Your employer constrains you from sharing intellectual property as a general policy
You are afraid of waking a "sleeping giant" that'll refuse to sell you parts if they see you as a competitor
You are afraid someone will mess up your design and then wrongly blame you for the poor performance when they can't replicate it
You might be exposing yourself to legal liability



Jerry Liebler said:


> ... One holds secrets for ONLY 2 reasons, the knowledge would benefit a competitor or it would embarrass oneself. Regards, Jerry


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## Jerry Liebler (Feb 1, 2011)

EVfun,
Yes the static drain on each cell with a normally closed loop is a concern! But just having a quad comparator on each cell "costs" up to 2 milliamps. Adding a voltage reference and 2 sets of voltage dividers adds another milliamp or so. So adding 2 milliamps for the opto relay and another 2 milliamps for a green LED is still "noise" for even a 40 AH pack (it would take over 100 days to use half of the packs energy). This loading is quite easily justified by the large gain in reliability and ease of implementation over any normally open architecture.
Regards
Jerry


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## dimitri (May 16, 2008)

Jerry Liebler said:


> Another assumption I have made is that an interconnect in a battery pack may become loose and no fire should result, hence the 300 volt DC rated fuse.


Are you implying that fire can be started with my current miniBMS product installed, due to lose connection? Please explain this hypothetical scenario in more details. It should be amusing, especially coming from someone who doesn't own an EV AFAIK and only knows LiFePo4 cells from datasheets.

You are posting same theoretical issues here as you do on TS Yahoo list, which should be renamed to "blind leading the blind" list, as most of active posters on that list have not held a LiFePo4 cell in their hands, let alone have an EV.

Oh, and BTW, every miniBMS module is fused, always been, always will be.


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## EVfun (Mar 14, 2010)

Jerry Liebler said:


> EVfun,
> Yes the static drain on each cell with a normally closed loop is a concern! But just having a quad comparator on each cell "costs" up to 2 milliamps. Adding a voltage reference and 2 sets of voltage dividers adds another milliamp or so. So adding 2 milliamps for the opto relay and another 2 milliamps for a green LED is still "noise" for even a 40 AH pack (it would take over 100 days to use half of the packs energy). This loading is quite easily justified by the large gain in reliability and ease of implementation over any normally open architecture.
> Regards
> Jerry


But why use comparators on the cells? It seems like a voltage reference for the high end and a low voltage detector for the low end could turn an optical isolator on outside of mid range. The 2 together shouldn't demand one milliamp when off. Something crudely like this:

```
R3         
+ ----^^^------    
    |     |   |    
    |     >  \/=   
    |  R4 >  -- O1 
    |     >   |    
    |     |---|    
    |     |  --    
    |-----)--|| V1 
    >     |  __    
 R2 >     |   |    
    >    --   |    
    |----/\   |    
    >   D1|   |    
 R1 >     |   |    
    >     |   |    
    |     |   |    
- -------------    

R1, 6k8
R2, 15k
R3, 680
R4, 10k
D1, TLV431 (1.24v ref)
V1, low voltage detector
O1, opto-isolator
```
Might want to throw a low power red LED on right on top of D1 so the current through O1 isn't much higher for over voltage compared to under voltage.


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## Jerry Liebler (Feb 1, 2011)

Dimitri,
My EV will have 52 100 AH CALB cells in series. What will happen if a bolt loosens and 182 volts DC from a freshly charged pack is put across a "MiniBMS cell module? There is a reason fuses have voltage ratings!
Yes I wouldn't risk my car to the current MiniBMS!
Regards
Jerry


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## dimitri (May 16, 2008)

Jerry Liebler said:


> Dimitri,
> My EV will have 52 100 AH CALB cells in series. What will happen if a bolt loosens and 182 volts DC from a freshly charged pack is put across a "MiniBMS cell module? There is a reason fuses have voltage ratings!
> Yes I wouldn't risk my car to the current MiniBMS!
> Regards
> Jerry


I can tell you what happens, since I tested it myself on my own EV and few customers tested it as well and reported same results. When high voltage is applied to single module, fuse blows immediately, which results in open cell loop and generates BMS signal. No fire, no drama. Total cost, $12 for module replacement, which is a good lesson to keep those bolts tight and follow install instructions.

Not risking your car to miniBMS is your natural right, since I am not twisting your arm to buy it. But, I will not stand here listening to some self proclaimed expert bashing my hard work. Unless you have proven a specific failure of miniBMS that ocurred in real EV under specific real conditions, you have no right to bash it. 

Create something that works and offer it to people, competition is good. But stop referencing my work in negative light unless you have some real data to prove it.


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## Jerry Liebler (Feb 1, 2011)

Dimitri,
I have NO intention of "bashing" the MiniBMS or your work, I only cited is a starting point and offer, to one or all, a design that is complete and has the attributes I've stated. I believe all components should be used within their ratings. When a battery manufacturer says 3.6 volts they mean 3.6 +/-1% because they used 2 significant figures and if they say 3.85 volts they mean a tolerance of +/-0.1% since they used 3 significant digits. In my view operating any component outside it's ratings, even under fault conditions is courting disaster. Your experience operating outside manufacturer's ratings and surviving is not an endorsement of such practices that I'll accept.
Regards
Jerry


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## dimitri (May 16, 2008)

Jerry Liebler said:


> Dimitri,
> When a battery manufacturer says 3.6 volts they mean 3.6 +/-1% because they used 2 significant figures and if they say 3.85 volts they mean a tolerance of +/-0.1% since they used 3 significant digits.


Clearly you have much to learn about LiFePO4 chemistry and how to interpret what manufacturers say and why they say what they say. I respect your intentions to improve the design and your faith in datasheets. I only ask not to refer to my name or my trademark unless you have solid proven data to support your references.

Good luck!


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## Jerry Liebler (Feb 1, 2011)

EVFUN,
It took a while but I kind of like your idea of a "monitored" normally open loop. This concept is used in virtually all alarm systems. A big advantage is it greatly expands the number of "suitable" available optolsolators allowing a likely cost saving. I'd still use a single voltage reference and a Quad comparator to accomodate a "shunting" function to maintain top balance. so the curent saving would be on the order of 2 milliamps but every bit helps.
Regards
Jerry


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## Jerry Liebler (Feb 1, 2011)

A disadvantage of the "monitored" normally open loop is it roughly doubles the number if interconnnections, is that really worth 2 milliamps?


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## EVfun (Mar 14, 2010)

The extra connections are all part of the vehicle 12 volt system. There are likely thousands of such connections already spread about the vehicle. Some in important things like lighting or ABS. I think another 2 per cell isn't a significant risk, especially since the monitored loop will detect any open connection.


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## Jerry Liebler (Feb 1, 2011)

With the NC architecture every modules health and operation is in fact monitored this is not the case with a monitored NO architecture. The extra connections make a monitored NO system cost more, both in materials and installation labor, than an NC system. The available systems hold per cell module drain under 10 milliamps. By throwing some money and parts at the problem the per cell drain could be reduced to 5 milliamps and still have the "fail safe" benefits of the NC architecture.
Regards
Jerry


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## EVfun (Mar 14, 2010)

Actually, I think the NC system has the potential short coming here. Transistors usually fail on. It looks like Dimitri's system has plenty of margin because I haven't heard of any such failures with it.


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## Jerry Liebler (Feb 1, 2011)

Only Dimitri can comment on his system, at least I won't. The design I've done has a green LED and opto relay driven by one output of a quad comparator which has a 10 milliamp rating. Resitors limit the currents through the LED and relay to a total of under 5 milliamps at HVC.


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## EVfun (Mar 14, 2010)

I'm using 60 amp hour cells in the buggy in my avatar. If I walk away for 6 months I can easily kill the 12v parasitic loads -- pull the fuse to the DC>DC and disconnect the 12v battery + so 12v parasitic loads don't kill it. I've even set it up so the controllers small parasitic load is pulled with that fuse too. The cell regs would be a pain to pull though. 10 milliamps is about 44 amp hours if I walk away for six months. Since I should leave the pack at about 50% SOC (LiFe cells age from being full even if not in use) that would be a problem if for some reason I didn't add amp hours every so often. I can live with 3ma, a one year margin of safety.

I've mostly been looking at some type of battery bridge system, only with isolated output and about a 1/2 to 3/4 volt balance window. I sketched the monitor I posted but never followed up with it or drew up a head board (an good job for a dual comparator.) With a bridge it would be easy to pull the parasitic load, or even set up so its only connected when the pack is being charged or driven.


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## Jerry Liebler (Feb 1, 2011)

As I said with the addition of 2 transistors and 2 resistors (a part cost of less than a dime) I can assure adequate drive to the opto relay yet have a max draw of 6milliamps with the typical slightly over 5 milliamps. The green led may be pretty dim at lvc. The 6 milliamps Would get you 416 days on a fully charged pack so if when you left on your 6 month safai they were full they would be right at 1/2 when you returned.


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## dimitri (May 16, 2008)

Just for the record, miniBMS module runs at 6.6mA.



> Actually, I think the NC system has the potential short coming here. *Transistors usually fail on*. It looks like Dimitri's system has plenty of margin because I haven't heard of any such failures with it.


Its virtually impossible in this context. I use optorelays rated many times over what they see in normal BMS use. In extremely rare cases when optorelay is damaged, usually due to install mistake or some external factors like a short from high voltage circuit to signaling loop, the relay blows like a fuse, opening NC loop and producing BMS alert.

As a side note, I recently added TVS component to miniBMS head end board, to improve EMI resilience. This addition was a result of extremely rare situation, which I discovered while working on a project with a new customer. This does not effect 99.9% of typical miniBMS users, but I will still offer free upgrade of the head end board to any existing customers. Upgrade is super easy to install in the field, without having to remove the board from the EV, I will provide instructions and support as always.


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## EVfun (Mar 14, 2010)

Of course you can design things however you would like. I find the desire to use a quad comparator confusing as references can more than drive the LED of an optical isolator and more than handle the gate of a the shunt load transistor provided the desired shunting current is less than 1 amp. 

I'm looking at monitoring from my particular knothole. My batteries are small and will be stored part of the year. I should store the batteries at about a 50% SOC, but that is in the middle of the vast nearly flat voltage area so perhaps they will end up being put away with 25 amp hours in them. Perhaps I get called away, end up working on the opposite coast for a spell and they sit for 9 months one year. With a 2 milliamp cell monitor limit I'm down to about 12 amp hours left in the cells. I'm not comfortable below 20% SOC unless I am right there watching it.

I notice that the EVworks units are in the ballpark of what I need for standby current and they are a NC system. These are what I installed in the Datsun and used with Dimitri's Head End Board. I should measure the actual standby current to see what ~3ma really means.


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## Jerry Liebler (Feb 1, 2011)

EVfun,
Abandoning the Quad comparator and the LM285 & replacing them with a 2.5 volt TC54 and 2 of the TS4431's allows a NC cell module to draw under 4ma. This may be what EVworks is doing as they advertise 3ma. Such a module could be even smaller and would have fewer parts on it & should cost about the same.


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## EVfun (Mar 14, 2010)

dimitri said:


> Just for the record, miniBMS module runs at 6.6mA.
> 
> Its virtually impossible [photo FET failing on] in this context. I use optorelays rated many times over what they see in normal BMS use. In extremely rare cases when optorelay is damaged, usually due to install mistake or some external factors like a short from high voltage circuit to signaling loop, the relay blows like a fuse, opening NC loop and producing BMS alert.
> 
> As a side note, I recently added TVS component to miniBMS head end board, to improve EMI resilience. This addition was a result of extremely rare situation, which I discovered while working on a project with a new customer. This does not effect 99.9% of typical miniBMS users, but I will still offer free upgrade of the head end board to any existing customers. Upgrade is super easy to install in the field, without having to remove the board from the EV, I will provide instructions and support as always.


Thanks for the info on standby draw. It's not bad, but it is a bit much for my buggy needs. 

Your cell boards seem to have the best reputation for NOT failing amongst the BMS choices available to the EV hobbyist. I certainly respect the design and execution. If I had found those before the EVworks hardware I most likely would have chosen them for the Datsun. The only thing I don't like is the remote mounted board option for the cell modules. Pack spaghetti scares me unless every wire going back to the pack is fused at the cell. (in fact, I think that was the actual cause of JR's small fire)

How about a little more information on who might need the TVS? I am using a non-isolated charger so I'm wondering if I may fall into the group.


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## Jerry Liebler (Feb 1, 2011)

EVFUN,
I have a schematic for a cell module that by moving one jumper can be either NC or NO. As an NO it would be under 2 milliamps while as an NC it would be about 5 milliamps.
It uses the TC54 for low voltage alarm and 2 TS4431's, one for hvc and one controlls shunting. I need some help in getting it posted.
Regards
Jerry


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## EVfun (Mar 14, 2010)

Jerry asked me to shrink the file size down to something manageable and post this. After a bit of discussion this one has hysteresis on both the HV shunt load and HV cell loop optical isolator.


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## Jerry Liebler (Feb 1, 2011)

THANK YOU PAUL 
The resistor values are not final! In other words I've changed some of the to get closer to what I want. I've laid out a PWB. On the PWB I have provided 3 holes for a jumper so the cathode of the opto relay can either connect as shown or to the cathode of the green led. One PWB will do either NC or NO. The default PWB is NC, a clad cut on the bottom and adding the jumper will make it NO. I've also put pads and holes for a second set of faston terminals for the extra connections needed in an NO system.
Regards
Jerry


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## Jerry Liebler (Feb 1, 2011)

I strongly favor the normally closed architecture. The downside of normally closed is current draw. So I took a look at what can be done to hold down static draw. One big issue is the opto relay should have 2 milliamps flowing through it normally this current is set by a resistor which must allow this curent at the LVC of 2.5 volts but with a fully charged cell at say 3.4 volts what was 2 milliamps is now 3.5 milliamps. A similar problem, but even worse, exists with the green LED if it has 1 milliamp at 2.5 it becomes 2.3 milliamps at 3.5volts. I've come up with a solution, adding a transistor, one resistor and a 1.224 reference. Basically I changed the LED drive to be a 3 milliamp constant current source. The implementation allows the full 3 milliamps for the green LED and the opto relay combination with a resistor controlling the share each gets, the circuit will wok from 2.1 volts up. With the lower and more certain current of the TS4431's and TC54 Typical current at 3.4 volts works out to 3.778 milliamps and worst case is 3.978 milliamps. This smaller drain will be far more consistent than the competition.
Regards
Jerry


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## GizmoEV (Nov 28, 2009)

> the circuit will wok from 2.1 volts up.


So with this NC system does that mean if a cell is below 2.1V that a low voltage alarm will be triggered?


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## EVfun (Mar 14, 2010)

As a general principle I like that. I am a bit concerned with what you mean by "the circuit will wok from 2.1 volts up." Will D3 be off with certainty below 2.1 or lower or will that leave it in a questionable state? If the state below 2.1 volts is questionable that is a problem because under load you can go from 2.5 to 2.0 volts quickly. 

There is a low voltage point where where it becomes difficult to keep the optical isolator on, a weakness with my idea of a monitored normally open loop. I can put a red LED in the high voltage detect line to reduce HVD current, and make the resistor for the optical isolator about 150 ohms. That would maintain a 2ma optical isolator current at 1.4 volts and still only as high as 8ma at 4 volts. Its been screaming stop for a while by then.

While your idea did have a very easy way to function either as a N.O. or N.C. isolator loop there would be a number of parts that would be best changed with a N.O. loop. Resistor values for operating the infrared LED is one such choice. As you refine your design you may be better off going one toward a N.C. loop if that is what you prefer. 

If you want to go with only a N.C. loop you may consider replacing the TC54 with another TS4431. It can turn the isolator on and the other one can turn if off. You can add a 4th resistor to the divider to set low, shunt, and high voltage points (instead of just shunt and high with 3 resistors.)


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## Jerry Liebler (Feb 1, 2011)

Sorry, I created a bunch of confusion, I intend to generate a low voltage alarm at 2.5 volts! That means D3 is off absolutely guaranteed! The mention of 2.1 volts is that is the point at which the constant current is no longer constant and the transistor saturates, well below the alarm level. A third TS4431 costs power and a few cents. The TC54 is an extremely low power user with 3 microamps max. While the TS4431 max draw is 350 microamps, huge difference. From all I've seen,heard, read, there is precious little energy below 2.5 volts and lots of risk of shortening cell life.


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## Jerry Liebler (Feb 1, 2011)

Yes the NO and NC designs conflict in how to drive the opto relay.
For the normally open design, The opto relay's LED should have it's anode connected to positive input (no resistor) and the TC54 should drive it's cathode through a resistor about 300 ohms to give near 4 milliamps at 2.5 volts but falling to under 2 milliamps below 1.8 volts. Independently the HVC TS4431 would drive the opto's cathode through a 1200 ohm resistor for 2 MA @ 3.6 volts. This, of course complicates the green LED but that can be solved with 3 diodes forming an low input 'or' function to the base of the transistor driving the green LED. 
Regards
Jerry


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## GizmoEV (Nov 28, 2009)

My question relating to the 2.1V was more to cover the case where a cell died when the vehicle was off. I know of someone who had a cell die while sitting on the shelf with nothing connected to it. I don't know what really happened but I would want an alarm if I went out to my car and tried to drive it. If a cell is at 0V I want a warning.


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## EVfun (Mar 14, 2010)

To get a start up warning with a 0v cell pretty much requires the use of a N.C. cell loop. The monitored N.O. loop has a lower standby current draw but has some low voltage point where it will quit working. With a 100 ohm resistor for the optical isolator it should work down to about 1.5 volts.


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## EVfun (Mar 14, 2010)

Jerry has a new version drawn up as a low drain N.C. loop cell module. 


> Calculated nominal specs are: shunt start=3.49, shunt reset 3.476, HVC set 3.600, HVC reset 3.579, current drain @3.4 volts 3.78 ma typical, 4.00 ma worst case.


My main concern is a lack of separate resistors for the green LED and the optical isolator. Since my primary interest is with <1 milliamp standby current N.O. cell modules with a monitored loop this is about where I detour off this course.


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## EVfun (Mar 14, 2010)

I wanted to post a little about my concerns with the tight HVC limit. I know we don't _want_ to go over 3.6 but after charging cells for a while I know some times some go over a little. I don't like to use the BMS as a primary control of the charger, instead viewing it as a backup to shutting things down in the event of issues. I see it as a second line of defense, not part of the first line of defense. My ideal would be something to "just say no" if a cell goes below about 2.1 or above 3.9. The goal is a tool to prevent a cell from ever making it down to 2 or up to 4 volts (for LiFePO4, the numbers vary based on chemistry.)


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## GizmoEV (Nov 28, 2009)

I personally wouldn't want a higher HVC limit. There is so little energy in that voltage region why would you want to stress the cells and shorten their life when all you might gain is a few hundred feet of driving range per charge?


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## EVfun (Mar 14, 2010)

My charger is set for 3.6 vpc (TS cells) and hold that for 1 hour. That doesn't mean every cell is at 3.6 volts, there is a little scatter and I don't want that terminating the charge every cycle. 

I think we are looking for slightly different things in a BMS. I expect my charger and controller to have strict control over the pack minimum and maximum voltage. I don't expect the BMS to be a regular part of this. If the BMS wakes up something is going wrong. If the BMS goes off on charge it will be terminated and I will get to figure out how charged the car got and what cell is out of line the next morning. I may even set up the LVC as a latching function too.


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## GerhardRP (Nov 17, 2009)

I wonder if when the normally closed circuit is opened, all the BMS modules are disabled, going to a near zero current drain. When the vehicle is off AND not charging, the circuit is opened externally removing the parasitic drain. Probably requires a PIC based system.
Gerhard


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## Jerry Liebler (Feb 1, 2011)

Gerhard,
Nice thought but the "Devil is in the Details". How can it be done? There is a which came first problem, how do you turn on the cell modules so they can "close" the loop if the loop is not already closed? If this is a "cost is no object" situation one could run a common pair of wires to each module and have each module use these wires to power the LED of a SECOND opto isolator to generate the turn on condition for the module from the output of that second opto isolator.
Regards
Jerry


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## mikep_95133 (May 20, 2009)

dimitri said:


> You are posting same theoretical issues here as you do on TS Yahoo list, which should be renamed to "blind leading the blind" list, as most of active posters on that list have not held a LiFePo4 cell in their hands, let alone have an EV.
> 
> Oh, and BTW, every miniBMS module is fused, always been, always will be.


Dimitri, 

The statement "blind leading the blind" could be applied to this forum and every other forum as well. Bad info and misunderstanding of these simple technologies is everywhere, not just at the TS list. But putting down the TS list or any list, is like the pot calling the kettle black. All EV forums are flawed. Even this one. The one thing that JR is an expert in, is pissing on all of the forums. Leave it to him. He's a "professional".

Oh man, I totally understand you defending your work. I'm there constantly. Jerry really stepped in it early on in this thread. I would recommend however to try and not piss on an entire group of folks if you can. It just doesn't help anything.

Mike


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## dimitri (May 16, 2008)

mikep_95133 said:


> I would recommend however to try and not piss on an entire group of folks if you can. It just doesn't help anything.
> 
> Mike


If you read the rest of my posts in this thread you would have noticed that Jerry and I reached some civil attitude towards each other, so no more pissing contexts here .


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## chaz_fwb (Feb 15, 2011)

*Bad boy charger technical help*

I purchased a ev with a bad boy charger.

It has a hammond tranformer (parallel connection), diode bridge retifier and large resistor on the 120 volt side and appears to work fine (120 vdc out). Except that the EV has 12 batteries which I assume would need 144 volts out.

The 240 side has additional components pior to the Hammond (they look like additonal smaller inductors), a with series connection to transformer. The 240 side is blowing fuses. Not sure what output voltage? any ideas?


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