# BMS using Celllog8



## madmike8 (Jun 16, 2011)

Honn1002 used cellogs to make a bms...

http://www.diyelectriccar.com/forums/showthread.php?t=56509&highlight=cellog


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## frodus (Apr 12, 2008)

I think they're great. IMHO monitoring is an absolute must with lithium batteries. Having an LVC and HVC is important to keep a healthy pack.

If I was going without a balancing BMS, the Celllogs is exactly what I'd use for a cheap robust system.

Just one thing though, they can cause unbalance on the pack because they tap power off of the first cell or two. Just something to keep in mind. I think there are mods out there to fix this, but I'm not sure.


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## major (Apr 4, 2008)

frodus said:


> Just one thing though, they can cause unbalance on the pack because they tap power off of the first cell or two. Just something to keep in mind. I think there are mods out there to fix this, but I'm not sure.


Actually off the first 6 cells. It takes a while, but it will cause cells 7 & 8 to drift to higher voltage than the first six. There is a simple fix....jumper soldered inside the cover of the celllogger. I haven't tried it yet. It is shown on a thread in this forum somewhere.



















Here it is. From the thread http://www.diyelectriccar.com/forum...s-relay-circuit-56509p3.html?highlight=cellog

And if interested, I can supply the JST connectors with wires assembled.

Anybody know if bblocher is still around? He had a nice circuit board design for this. Photo of his solution attached.


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## frodus (Apr 12, 2008)

Thanks Major!


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## madmike8 (Jun 16, 2011)

Yeah, I wish someone had a good circuit board for this... even the files so, we could order some...


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## madmike8 (Jun 16, 2011)

Doh, double post sorry...


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## rwaudio (May 22, 2008)

madmike8 said:


> Doh, double post sorry...


I'm actually working on one. 12 un-cased Cell log 8's that can be used to monitor up to 96 cells, with alarm outputs connected to relays that form a NO or NC loop depending on how you want it to work. Cell logs plug into connectors on the PCB and if you used one or more logging versions they could be removed easily to download the data. Along with relays on the most negative wire since you can basically turn them off (and remove parasitic load) by disconnecting the ground wire.


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## madmike8 (Jun 16, 2011)

rwaudio said:


> I'm actually working on one. 12 un-cased Cell log 8's that can be used to monitor up to 96 cells, with alarm outputs connected to relays that form a NO or NC loop depending on how you want it to work. Cell logs plug into connectors on the PCB and if you used one or more logging versions they could be removed easily to download the data. Along with relays on the most negative wire since you can basically turn them off (and remove parasitic load) by disconnecting the ground wire.


Sign me up...


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## major (Apr 4, 2008)

rwaudio said:


> I'm actually working on one. 12 un-cased Cell log 8's that can be used to monitor up to 96 cells, with alarm outputs connected to relays that form a NO or NC loop depending on how you want it to work. Cell logs plug into connectors on the PCB and if you used one or more logging versions they could be removed easily to download the data. Along with relays on the most negative wire since you can basically turn them off (and remove parasitic load) by disconnecting the ground wire.


Kool  I'm interested. Any thoughts to making the board modular? I have different applications where I need 2, 4, 6 or 12 of the little buggers for the installation in particular. 

On the data side of the gizmos, has anybody opto isolated the USB to computer connect so you can monitor multiple cellloggers (or even a single) without blowing sh!t up? Or download without disconnecting the unit from the battery. They aren't perfect devices, but pretty nice for $29


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## rwaudio (May 22, 2008)

major said:


> Kool  I'm interested. Any thoughts to making the board modular? I have different applications where I need 2, 4, 6 or 12 of the little buggers for the installation in particular.
> 
> On the data side of the gizmos, has anybody opto isolated the USB to computer connect so you can monitor multiple cellloggers (or even a single) without blowing sh!t up? Or download without disconnecting the unit from the battery. They aren't perfect devices, but pretty nice for $29


Yes, it could be populated to use any number up to 12. I haven't tried the opto isolator yet but it's a good idea (my design won't do anything with the USB though). I'll see if pricing would be better to do a board that holds 4 or 6 instead and then use multiple boards for the total required, the alarm loop would be the same it would just need to loop from board to board. (smaller boards are cheaper, and higher quantities bring the price down) I plan on using fairly generic Phoenix Euro connectors similar to this for the cell wiring:
http://search.digikey.com/ca/en/products/282836-5/A98079-ND/1826942

And simple right angled sockets for the cell log 8's, Alarm from the cell log would use the pigtail provided and just solder to pads on the pcb.

If you don't need loggers and just want monitors they are only ~$14 otherwise they work exactly the same as the logging version.


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## madmike8 (Jun 16, 2011)

I like the idea of the smaller modular system... I'm planning 32 cells so, 4 cellog8s. I plan to buy one that logs and 3 that don't. I figure I can moving the logging one around to get logs from cells when I want them.


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## Citystromer (May 2, 2009)

frodus said:


> Having an LVC and HVC is important to keep a healthy pack.
> 
> Could someone tell me a reasonable value for a LVC for a pack of 40 Winston WB LYP160AHA (160Ah Life yellow) with a published discharge limmit of 2.8V (HV max 4V)
> I would have started using a LVC of 3,15.
> Is that kind of too high?


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## MN Driver (Sep 29, 2009)

major said:


> Anybody know if bblocher is still around? He had a nice circuit board design for this. Photo of his solution attached.


Great question, I haven't seen him around here since he took his shunts off the market. I think he got spooked and isn't around anymore. Possibly a different name here, who knows.


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## frodus (Apr 12, 2008)

Citystromer,

Take this as positive criticism because I like your posts, but they're all using quotes incorrectly. Every time you post a reply to a quote, you remove the /QUOTE at the end. The QUOTE=blah blah is the Start of the quote. The /QUOTE signifies the end of the quote. Don't remove it and it will display correctly. Just hit the quote button and type the response after the /QUOTE


I'd say start at 3.15 or so if you want, and dial it back. I wouldn't go down to 2.8, but maybe 3 or 2.9 wouldn't be bad. You just want to be careful because it's easy to fall off the cliff as a cell is near the lower end of it's SOC. Start on the safe side and tweak it.


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## Citystromer (May 2, 2009)

major said:


> Actually off the first 6 cells. It takes a while, but it will cause cells 7 & 8 to drift to higher voltage than the first six. There is a simple fix....jumper soldered inside the cover of the celllogger..


Great, easy to do,
I wanted to point out one more important thing, concerning to wire length:
If the celllogs are supposed to be placed at a single loation, the difference in length of t the wires from all the cells can easily account for a few mV false reading, depending on wire gauge. I tried .51 gage = 24AWG resulting in one mV per foot length. 
I am going to keep those wires as short as possible, and only run the wires from the single alarm relays tied to each celllog to a single point from where I `ll controll the main contactor. (to take the battery off line in cas off HV or LV on any cell)


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## major (Apr 4, 2008)

Citystromer said:


> I wanted to point out one more important thing, concerning to wire length:
> If the celllogs are supposed to be placed at a single loation, the difference in length of t the wires from all the cells can easily account for a few mV false reading, depending on wire gauge. I tried .51 gage = 24AWG resulting in one mV per foot length.
> I am going to keep those wires as short as possible, and only run the wires from the single alarm relays tied to each celllog to a single point from where I `ll controll the main contactor. (to take the battery off line in cas off HV or LV on any cell)


Hi City,

I really don't think you need to worry about V drop in the wires up to a reasonable length, say 10 feet. I run #22 wire sometimes 4 feet. I typically keep all wires the same length, plus or minus a foot. Using a Fluke DVM occasionally to calibrate, I can't say I have identified any voltage drop. You just have on the order of microamps in these wires.

Control the main contactor? Probably a bad idea. For HVC you want to control the charger. For LVC you need to cutback the controller or give a warning to the driver. In either case, opening the main contactor is a bad idea.

Regards,

major


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## Citystromer (May 2, 2009)

frodus said:


> Citystromer,
> 
> Take this as positive criticism because I like your posts, but they're all using quotes incorrectly. Every time you post a reply to a quote, you remove the /QUOTE at the end. The QUOTE=blah blah is the Start of the quote. The /QUOTE signifies the end of the quote. Don't remove it and it will display correctly. Just hit the quote button and type the response after the /QUOTE
> 
> ...


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## frodus (Apr 12, 2008)

Citystromer said:


> Thanks, appreciate!


you didn't listen to a darn thing I said, did you, hahaha


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## rwaudio (May 22, 2008)

Revised PCB to hold 4 Cell Log 8's 
I haven't double checked it yet so it still needs work.
3.25" x 6.72" 

Each alarm output triggers a relay that forms a loop, an alarm on any cell log will open the NC alarm loop. Multiple breakout modules will use the same alarm loop. The alarm loop is up to the end user and could trigger a warning light, buzzer, trigger an input on a Soliton or similar controller or reduce throttle with parallel resistor.

There are relays that disconnect the most negative wire from each cell log effectively turning it off to remove parasitic load. Can be turned on (12v dc) during driving and or charging. There are two unused terminals at the moment, I might make one of them 12v from the ignition and the other 12v for charging to allow two different 12v sources or switches. 

Not all slots need to be filled, a 45 Cell pack would require two breakout modules and 6 CellLog8's and only monitor 5 cells on the final CellLog8.

It will work with both the original "logging" CellLog8S as well as the "non-logging" CellLog8M. 

Is there anything I missed, or anything people would like to see in this?


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## madmike8 (Jun 16, 2011)

That's awesome...


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## Citystromer (May 2, 2009)

rwaudio said:


> Revised PCB to hold 4 Cell Log 8's
> I haven't double checked it yet so it still needs work.
> 3.25" x 6.72"
> 
> ...


Hi,cool
Here`s my answer for over last weekend: Not quite as professional, though rugged.
The alarms open collector transistor within the cellog supplies ground via a 390 ohm resistor and a LED to a 24V relay whose other end connects to the 8 cells pack most positive lead.
Built up on a pre drilled prototype board, epoxied together, for mechanical strength.
Those 5 Cellogs plus one ballancer (in fact those are 2 parallel) for every cell make up my complete BMS- for under 200$. A very acurate, reliable one, I think, depending on good wiring - which I have with silikone insulation wires. 
I soldered within every Cellog the jumper according to majors post, (who figured this out - and how???) - and it works:
Every Cellog now draws 32µA, except number 2 whitch draws 46 for some reason. 
When I tested the alarm, I noticed, that the Led and relay flickers - it does not just stay on permanently. Rather it comes on and off, all the time that an alarm condition is reached. This has to be taken into account when designing further circuits.


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## Citystromer (May 2, 2009)

rwaudio said:


> Revised PCB to hold 4 Cell Log 8's
> 
> Each alarm output triggers a relay ....
> There are relays that disconnect the most negative wire from each cell log ...


Hi, rwaudio,
looks very good, which relays are for disconnecting the minus leads? You use only two- correct?
And wher is the second blue wire from input +5 going to? It`s just a positive input for the cellog to meassure the voltage there?

What does cells1 - to cells11 mean? 

Is this the top view of the schematic - then the numbering of the Cellogs inputs are confusing, considdering the real Cellogs minus is 1.
You numbered the inputs from -1, +1 throug +32, so, 9+ is really the negativ of the second Cellog.
I`m sure there is a reason but I just don`t see it.


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## rwaudio (May 22, 2008)

Citystromer said:


> Hi, rwaudio,
> looks very good, which relays are for disconnecting the minus leads? You use only two- correct?
> And wher is the second blue wire from input +5 going to? It`s just a positive input for the cellog to meassure the voltage there?
> 
> ...


I've moved things around a bit to streamline it. The 2nd wire from each of the 5th pins for each cell log is to power the alarm relay. (I've since moved it slightly and is powered from the first 4 cells of a group) This is only active in an alarm situation and not during normal use.

The pin numbering isn't the cell log pin numbering it's the connector pin numbering and doesn't really mean anything. This is a top view of the PCB layout and you will notice that the far left connector pin numbering matches the cell log pin numbering.

If you look closer you will see that 8+ is actually the negative for the 2nd cell log. 9+ is the is the first cell in the 2nd group. 8+ for the 2nd cell log goes through the relay to turn off the cell log.

Relay 1 and 3 are DPDT and connect ground to all of the cell logs (individually). The remaining 4 relays are for the alarm output and in the new version the unused half (NC/C/NO pins) of the relay are broken out so they can be used any way you want.

I've also connected an extra 12v and ground to the unused connector at the top to allow easy daisy chaining of 2 or more modules without each one needing it's own power wire from the source.

Cells1 through Cells11 is simply the name for the connector on the PCB, the others are labelled power at the moment but those are simply names that let me lay out the PCB when I move from the schematic to the board so I know what order to put the connectors in.

I haven't routed the new version yet but this gives you an idea of the parts layout.


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## madmike8 (Jun 16, 2011)

So, are you routing these yourself? Please let me know when they are available.


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## Nuts&Volts (Dec 20, 2011)

I am interested in a board or two or three as well. 

Just a thought, but maybe you could have another output JST-XH 9pin connector coming off of another end. This would just been vias available for a through hole JST-XH connector. This would allow the use of a cheap RC balance charger to balance the cells whenever it is need. You essentially get a full functioning BMS on the cheap. 

If you dont put these on the boards I can just have some additional wires coming off of the screw terminals go to a JST connector.


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## rwaudio (May 22, 2008)

madmike8 said:


> So, are you routing these yourself? Please let me know when they are available.


Yep, I route them, the autorouters in eagle suck, as soon as I have some time I'll route then double and triple check and get the boards made. Looks like 50pcs is a good minimum quantity to hit a decent price point. I'll make them available once I get them and have a chance to test it.



Nuts&Volts said:


> I am interested in a board or two or three as well.
> 
> Just a thought, but maybe you could have another output JST-XH 9pin connector coming off of another end. This would just been vias available for a through hole JST-XH connector. This would allow the use of a cheap RC balance charger to balance the cells whenever it is need. You essentially get a full functioning BMS on the cheap.
> 
> If you dont put these on the boards I can just have some additional wires coming off of the screw terminals go to a JST connector.


The board isn't designed to carry much current, so unless it is only 1A or less for balancing I would suggest breaking it out of the terminals then you can simply use suitable wire for the purpose. I could put some pads under the Cell log location that would allow for a balancer to be connected to the bottom, but that might not be so user friendly.

If it would be helpful to simply have solder pads that you could connect something like this: 
http://www.ebay.com/itm/8S-JST-XH-Connector-balance-wire-Cable-9-PIN-50cm-9PIN-/150608613045?pt=Radio_Control_Parts_Accessories&hash=item2310f90eb5#ht_2253wt_1037
Then I would be happy to.

(I'll see how hard it would be to simply have room for another JST-HX connector on the right side of the board, it would make what you are trying to do much easier much easier)

Are there 8 cell balancers? Is it something like this that you would be using??
http://www.hobbyking.com/hobbyking/store/__10786__HobbyKing_HK_010_Wattmeter_Voltage_Analyzer_.html

Thanks for the input.


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## Nuts&Volts (Dec 20, 2011)

Yea I actually have one of these (http://www.progressiverc.com/fma-powerlab-8.html) because I want to do cell testing as well. But yea it would 1A max balance and wouldnt use the board to do anything but balance. I think adding extra wire to the screw terminals would be fairly easy. But I was just thinking a row of through holes on the right side would allow a JST connector (or wires like you linked) to be attached easily. Please don't redesign something like this into just for my sake thou. I can make it work either way. I just want a simple PCB to organize all the needed parts and make the install straightforward

Just so I understand this properly, the alarm GND from each Cell-log is isolated from the batteries and the other alarms by the relays right? I have only seen this done with opto-isolators in past designs. 

FYI if you do end up making a lot it may be worthwhile to post on Endless-Sphere and ElMoto.net in order to sell more.


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## whiteggs (May 21, 2010)

Eagerly awaiting the outcome of your board, do you have a price range in mind?


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## rwaudio (May 22, 2008)

Nuts&Volts said:


> Yea I actually have one of these (http://www.progressiverc.com/fma-powerlab-8.html) because I want to do cell testing as well. But yea it would 1A max balance and wouldnt use the board to do anything but balance. I think adding extra wire to the screw terminals would be fairly easy. But I was just thinking a row of through holes on the right side would allow a JST connector (or wires like you linked) to be attached easily. Please don't redesign something like this into just for my sake thou. I can make it work either way. I just want a simple PCB to organize all the needed parts and make the install straightforward
> 
> Just so I understand this properly, the alarm GND from each Cell-log is isolated from the batteries and the other alarms by the relays right? I have only seen this done with opto-isolators in past designs.
> 
> FYI if you do end up making a lot it may be worthwhile to post on Endless-Sphere and ElMoto.net in order to sell more.


I have a Powerlab 6 that I'm using to measure the capacity of my cells, since you wouldn't actually need the celllog 8 connected when balancing with the PL8 I would recommend that you simply pull a celllog 8 and plug your PL8 into that connector. When it's done replace the celllog 8 and move on to the next one.

You are correct, the alarm is isolated using relays, there is one relay per celllog and it can be used in the loop configuration that I have, or in a configuration of your choosing using the other set of relay contacts that are broken out at the bottom of the board.



whiteggs said:


> Eagerly awaiting the outcome of your board, do you have a price range in mind?


The PCB price is a bit high since it's only a run of 50, (it doesn't get significantly cheaper until 1000pcs) but I think I could do a fully populated PCB with all of the relays and connectors etc. for $75US + shipping, not including the celllog 8's.
So if you went with the non logging version of the celllog 8 $13.57US from hobbyking, that's $54.28 + $75 + shipping (x2) for a 32 cell BMS (Battery MONITORING System) with cell level HV/LV and DeltaV alarms.

I may also design a main board that could be mounted up front with either a buzzer/light and other interface connectors that would allow an alarm signal to turn off a charger, feed into a controller to activate a limp mode or similar.


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## Nuts&Volts (Dec 20, 2011)

Oh yea great point, no need to add anything to the board then it will work great for me. 

You can also point out the modularity of this setup. You can use this BMS with just about any cell chemistry, because you can reprogram the alarms so easily (I forget the limits on the cell-log thou). It also can data-log for you if you want. I just know I have 3 cell-logs sitting around and it would be nice to use them, especially to turn my charger off. Right now I'm just monitoring it.


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## rwaudio (May 22, 2008)

Final design, I need to double check it tomorrow.

-Revised to fit the Cell Log 8 WITH the casing
-Revised to break out the unused half of the relay with NC/C/NO terminals
-Revised 12v and Gnd connections for daisy chaining when using more than one Breakout Module (this is what turns on the Cell logs)
-Revised layout for simple/direct routing
-Revised mounting holes for more clearance

By removing a Cell Log 8, a balancing connector could be plugged in from something like a PowerLab 8 charger (Maximum 1A)

Alarm loop current is maximum 500mA

Alarm NC/C/NO current is maximum 1A


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## Nuts&Volts (Dec 20, 2011)

Nice, how will the alarm output be attached to the board? Will you have wires soldered to the board with the plug hanging off the other end? 

Looking forward to using one of these. Will you be assembling them or just supplying bare boards? Sorry if this was posted elsewhere


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## rwaudio (May 22, 2008)

Nuts&Volts said:


> Nice, how will the alarm output be attached to the board? Will you have wires soldered to the board with the plug hanging off the other end?
> 
> Looking forward to using one of these. Will you be assembling them or just supplying bare boards? Sorry if this was posted elsewhere


The alarm is a Normally closed loop (NC) when an alarm on any group is triggered it opens the loop. A bad connection in your wiring can also open the loop. It's designed in a similar way to the Mini BMS loop (a Mini BMS Head End Board could be used with this as well if Dimitri is willing to sell just the Head End Board)

I will be designing my own "Alarm board" with more features but it might take a little while. By the time I have these boards available I will have some how to's on making a buzzer and warning light using a simple inexpensive relay that turns on when the loop is broken.

I will be supplying finished boards that are ready for cell log 8's to be plugged in. I won't be selling cell log 8's though.


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## Nuts&Volts (Dec 20, 2011)

Thanks for the info!


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## rwaudio (May 22, 2008)

Just a question....

My current design relies on the alarm wires from the cell log 8 to be soldered to the PCB, I had dismissed this as not a problem, but since I'm not supply the Cell Logs this would be left to the end user. I'm guessing not everyone would have soldering equipment.

Should I make room for some small screw terminals so that the pigtail provided with the Cell Log 8's can simply be stripped and screwed down??


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## madmike8 (Jun 16, 2011)

Well, I can solder just fine. So, I'm easy... Put my name on one of the first 50!

Thanks for your work...


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## Nuts&Volts (Dec 20, 2011)

I can solder on small wires no problem. Not sure if their is a good solution for those who can't but they may few and far between in this market


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## rwaudio (May 22, 2008)

PCB's are on order, estimate about 2 weeks till they arrive.


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## madmike8 (Jun 16, 2011)

Cool! P.m. Me when your ready.


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## T1 Terry (Jan 29, 2011)

rwaudio said:


> Just a question....
> 
> My current design relies on the alarm wires from the cell log 8 to be soldered to the PCB, I had dismissed this as not a problem, but since I'm not supply the Cell Logs this would be left to the end user. I'm guessing not everyone would have soldering equipment.
> 
> Should I make room for some small screw terminals so that the pigtail provided with the Cell Log 8's can simply be stripped and screwed down??


 With the alarm port, as far as I can gather it trips a relay is that correct? If I go this right, what hold the relay in the active position and what determines how long it stays on for?

T1 Terry


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## rwaudio (May 22, 2008)

T1 Terry said:


> With the alarm port, as far as I can gather it trips a relay is that correct? If I go this right, what hold the relay in the active position and what determines how long it stays on for?
> 
> T1 Terry


This is a breakout board with relays to isolate the Cell logs but give you a simple alarm loop similar to mini bms. The relay will be on/off exactly as the alarm on the cell log is. Exactly how you process that signal in the end is up to you. I may use a latching relay or something with an adjustable time constant so that you can choose how long an alarm stays on even if the alarm was a one time trigger. By the time the boards are ready I will have a simple how to on wiring up a network cable with 4 LED's to signal which Cell Log triggered the alarm.


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## T1 Terry (Jan 29, 2011)

rwaudio said:


> This is a breakout board with relays to isolate the Cell logs but give you a simple alarm loop similar to mini bms. The relay will be on/off exactly as the alarm on the cell log is. Exactly how you process that signal in the end is up to you. I may use a latching relay or something with an adjustable time constant so that you can choose how long an alarm stays on even if the alarm was a one time trigger. By the time the boards are ready I will have a simple how to on wiring up a network cable with 4 LED's to signal which Cell Log triggered the alarm.


 A how to for building a "time on" adjustable relay circuit that didn't draw power from the Cell Logger alarm circuit would be very handy as well if possible please  The on to be ajustable between 10 mins and 30 mins would be great.

The idea I have is to use a 24v water heater element linked across the 8 cell the cell logger is monitoring and have alarm settings for 3.6v single cell and 28v total so if a cell or group of cells gets ahead of the others the load will pull that cell/set down while the others continue to charge. The fact that any voltage above 3.45 per cell has no more capacity than 100% means that any run away cell would quickly be brought into balance and the whole pack could continue being charged till total pack charging voltage was reached. Top balancing with a bonus water heater function.

T1 Terry


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## rwaudio (May 22, 2008)

Here is a first look at the Cell Log 8 Breakout module.

More info to come.


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## Nuts&Volts (Dec 20, 2011)

How awesome is that ^^^???

Pretty damn awesome. Looks great man! hope the testing goes well.


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## jddcircuit (Mar 18, 2010)

rwaudio said:


> Here is a first look at the Cell Log 8 Breakout module.
> 
> More info to come.


That looks great. I am sorry if my questions are already answered elsewhere in the thread.

What is the approximate cost per cell work out to be?
What is the current draw on each cell or how much imbalance do you expect the monitoring method to contribute if any?

I am very interested in low cost monitoring solutions and logging of parametric data for optimization purposes. The design I am currently working on is attempting to get the voltage of each cell to a central processing unit for the various actions like alarming and logging. My conversion will have over 100 cells in series so I want to get my cost per cell as low as possible.

Regards
Jeff


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## major (Apr 4, 2008)

rwaudio said:


> Here is a first look at the Cell Log 8 Breakout module.


Lookin' good, rw  I'll be interested in a few. Let us know please.



jddcircuit said:


> What is the approximate cost per cell work out to be?
> What is the current draw on each cell or how much imbalance do you expect the monitoring method to contribute if any?


Hi jdd,

The CellLog8s is just under $30 and monitors 8 cells. It draws just a few milliamps per cell and is a little heavier on the first 6 cells. See mod on post #4 to equal out the current draw to all 8 cells. 

Just for the monitor function you should be under $5 per cell when you include connectors. You cannot connect the USB outputs while connected to the cell strings, so you have to use the built in displays or disconnect the CellLoggers and download data collected.

rw's circuit boards look nice and provide a means to use the HV and LV alarm functions to activate protective measures similar to a BMS.

Regards,

major


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## rwaudio (May 22, 2008)

Nuts&Volts said:


> How awesome is that ^^^???
> 
> Pretty damn awesome. Looks great man! hope the testing goes well.


Thank you!! I think it turned out well, I'll be setting up to test in the next day or so. I don't have a 32S pack assembled yet so I will probably use 4 of the dc/dc charger board that I also made. That way I can vary each "cell" voltage and test the alarms individually and make sure everything works as it should.



jddcircuit said:


> That looks great. I am sorry if my questions are already answered elsewhere in the thread.
> 
> What is the approximate cost per cell work out to be?
> What is the current draw on each cell or how much imbalance do you expect the monitoring method to contribute if any?
> ...


I think Major covered just about all of your questions. This was a low volume batch of a fairly large PCB so the cost is a bit high, not to mention the number of connectors that go on one. I should be able to do a finished board with all connectors/relays but WITHOUT Cell Log 8's for $75-80.

Major went over the price of the Cell Logs themselves.



major said:


> Lookin' good, rw  I'll be interested in a few. Let us know please.
> 
> 
> 
> ...


Thanks Major, my board will supply a relay isolated version of the Cell Log alarm signal so it will still need to be processed with either an audible or visual alarm or possibly an input to either the controller or other system. This does make it a lot easier to interface with the Cell Logs though.

I'll get some video of the board in action and show everyone what the RJ45 jack is all about. It's not network or anything fancy don't get your hopes up, but Cat5/6 cables are abundant so by chopping an end off and using the desired length a quick and dirty visual indicator of which Cell log has triggered the alarm can be seen by soldering some resistors and LED's, that way if you have one "logger" and want to move it to the cell group that is triggering the alarm you can tell what group it is.


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## madmike8 (Jun 16, 2011)

Cool! I'm still waiting... definitely want one...


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## rwaudio (May 22, 2008)

Testing is going well, everything is working as it should. I don't have a 32S pack at the moment so I'm simply using 32 cells worth of my dc/dc charger. It works better because I can adjust the voltage of each cell and test the alarms.

All of the alarms trip the relays, I just need to thoroughly test the alarm function on the "loop" as well as test the RJ45 output with a Cat5/6 cable and LED's.


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## rwaudio (May 22, 2008)

Everything has been tested and is working exactly as designed. Here is a short video of the Breakout module in action. 
I will make a post in the vendor section with details on shipping cost, how to buy etc.


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## major (Apr 4, 2008)

rwaudio said:


> Everything has been tested and is working exactly as designed. Here is a short video of the Breakout module in action.
> I will make a post in the vendor section with details on shipping cost, how to buy etc.


Cool  My guy is ready to order. Put up the details. I told him it would function with only 2 CellLog8s on the board as well as all 4. We have application for both, 4 and 2. I hope I'm right about that.

 major


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## rwaudio (May 22, 2008)

major said:


> Cool  My guy is ready to order. Put up the details. I told him it would function with only 2 CellLog8s on the board as well as all 4. We have application for both, 4 and 2. I hope I'm right about that.
> 
> major


You are correct, it will work with 1, 2, 3 or 4 cell logs. The only possible issue is that for the alarm function to work properly (turn on the relays) there needs to be at least 4 cells connected to a cell log.

Using 1,2 or 3 cells won't work, 9-11, 17-19, 25-27 won't give you full alarm functionality for the last cell log either. 

I'm just working on finding suitable shipping methods and packaging.

I also checked with dimitri and he is willing to sell just the Head End Board from his MiniBMS system and his board would interface with the NC loop on my Cell Log Breakout Board. All functionality would be exactly the same and would be connected as per his documentation.


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## rwaudio (May 22, 2008)

Boards are tested, packaging and shipping methods determined, if interested please see this thread in the classified section.
http://www.diyelectriccar.com/forums/showthread.php/cell-log-8-breakout-module-70186.html

Please keep any "sales" related questions out of this thread, that's what the classified section is for (thread above).

Thanks!


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## athlon (Feb 27, 2012)

Hello , I used the Cellog plus the MiniBMS to monitor my battery in my recent trip from Milano to Dakar , for sure this setup is not optimal because Celog tends to unbalance a little the cell 7 and 8 that go higher than the rest but I thik is something really cost effective and with just one spare CellLog I was feeling very safe (My battery are 24x100Ah paralled with 24x150Ah so I have 6 CellLog onboard)


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## rwaudio (May 22, 2008)

athlon said:


> Hello , I used the Cellog plus the MiniBMS to monitor my battery in my recent trip from Milano to Dakar , for sure this setup is not optimal because Celog tends to unbalance a little the cell 7 and 8 that go higher than the rest but I thik is something really cost effective and with just one spare CellLog I was feeling very safe (My battery are 24x100Ah paralled with 24x150Ah so I have 6 CellLog onboard)


If you have a look at Major's post on the first page of this thread he shows the process of modifying the Cell Log 8's to balance the current draw much closer between the cells.
http://www.diyelectriccar.com/forums/showpost.php?p=278842&postcount=4


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## swoozle (Nov 13, 2011)

rwaudio said:


> By the time the boards are ready I will have a simple how to on wiring up a network cable with 4 LED's to signal which Cell Log triggered the alarm.



RW, although I won't get to this part of my project for a while, I'm hoping you still plan to do this. Us challenged folks will find it very useful.

Thanks


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## rwaudio (May 22, 2008)

swoozle said:


> RW, although I won't get to this part of my project for a while, I'm hoping you still plan to do this. Us challenged folks will find it very useful.
> 
> Thanks


Yep, I just have to draw it up, I have it scribbled on some scrap paper. We are moving at work this week and it has been and is going to get more insane.

I will also try and expand upon the RJ45 connector so that it can do more, like run a buzzer, etc.

I don't think I want to design a "head end board" like Mini BMS, Dimitri already did it and I've heard no complaints so buy his if it fits your needs. In the tutorial video for EMW's 10kw charger they also mention that you can connect the NC loop of a MiniBMS to it, so you could do the same with this Cell Log Breakout Module and it would work the same way.

I think in time there will be many ways to interface with this module, and I imagine some of the best ones will come from you guys when you get the board and start playing with it. 

I will post the schematic soon though.


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## rwaudio (May 22, 2008)

Attached in the zip file is a high rez image of the schematic directly exported from Eagle. It's a bit messy as I didn't tidy everything up before moving on to the PCB layout.

There is also a smaller image attached so you can see what's in the zip file.


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## rwaudio (May 22, 2008)

A couple of people have asked if it's possible to measure two different (isolated) battery systems using one Cell Log 8 Breakout Module, the answer is YES. However there are cases where the board needs to be modified slightly to make this work.

Below is the modification to allow measurement of two separate systems where the cells 1-16 and 17-32 are completely isolated from eachother. Care must be taken when soldering to the relay pad for the new wire though a solder bridge would be bad news.












The other questions has been can I monitor my 12v battery along with the HV pack because I'm not using all of the Cell Log 8 inputs on the board. The answer is also YES... sometimes.

For example if you have a 48 cell pack you would require two Cell Log 8 Breakout modules, the first would have 4 Cell Logs and the 2nd would only have two. The "top" two or cells 17-32 would not be used on board two. Now it is possible to use the top section, Cells 24-28 to monitor a 4 cell LiFePO4 12v system battery without causing problems or connecting the 12v pack with the HV pack. The key here is that Cell Log section 17-24 is left empty!! (**Cell 24+ is used as cell 1 negative, cell 1 plus is 25+ etc..**)

Alarms from the 12v system battery also affect the NC loop and other alarms so that must be taken into consideration on the total system depending on how things are connected.

If you were using 56 cells then the third section 17-24 would also be used for HV monitoring and if you wanted to also monitor the 12v battery using cells 25-28 a small modification to the board would be required, much the same as the image above, just at a different place on the board. I can create an image with instructions if anyone wants to do this.

If using a 12v Lead acid battery the Cell Log will accept higher voltages on the first two terminals and could be implimented the same as a 4 cell LiFePO4 battery using terminals 24 and 25 instead of 24-28. I don't know how the alarms behave though and you are on your own if trying this.

Under NO CIRCUMSTANCES can you create this isolation within a cell log 8. IE if running 60 Cells, two boards with 1-32 on board one and 1-28 on board two. You can NOT monitor the 12v system battery using Cell inputs 29-32. This simply does not work and will fry something, if you are lucky it's just a Cell Log 8.

If you have specific questions about monitoring a battery system not mentioned feel free to ask. If anyone wants boards modified for a specific use at the time of purchase I'm happy to do it free of charge.


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## swoozle (Nov 13, 2011)

major said:


> Actually off the first 6 cells. It takes a while, but it will cause cells 7 & 8 to drift to higher voltage than the first six. There is a simple fix....jumper soldered inside the cover of the celllogger. I haven't tried it yet. It is shown on a thread in this forum somewhere.


I performed this mod on all 6 of my Cell Logs and now when attached to USB they give a "ERR: CELL VOLT" indication with no opportunity to do things like send the log file to the PC. When attached to the pack they work fine; it's just the USB connection that is now hosed.

A little searching indicates this is a common result. An email to Junsi got me direction to upgrade to the latest (v208) firmware, which didn't fix it. 
Has anyone else had this problem or know how to fix it besides undoing the mod?


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## T1 Terry (Jan 29, 2011)

They need to be very small capacity cells to be affected by the difference in power draw between the first 6 cells and the the last 2. Maybe on an electric cycle, but not anything with a bigger pack. A light bulb across cells 7 and 8 for a minute will draw more than the logger imbalance created over 3mths so it's really a non issue with bigger capacity packs. Over the last 12 mths on a 180Ah 24v pack cell 7 & 8 were not the cells that regularly suffered a run away, it was shared fairly evenly across the whole pack. We have the alarm port set to switch a timer circuit relay that cuts he charge for 2 mins if a cell reaches 3.6v, the pack gets much closer to 100% this way without any form of BMS boards across the cells, the pack is cycled every day, it's part of a remote house power supply system. 
We tried the bridge on one logger, it wouldn't record data files after that and still didn't after the link was removed, it went in the junk box.

T1 Terry


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## Elithion (Oct 6, 2009)

Citystromer said:


> Hi,
> I`m planning to build a BMS using [inexpensive] zener type [balancer], (3A max, conducting at 3.6V)


Zener diodes will make things worse, because low voltage Zener diodes have too much leakage at the normal cell voltages. See the Li-ion, section 5.2.11 (free on Google Books).
You're better off with no balancing than with Zener diode balancing.


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## swoozle (Nov 13, 2011)

T1 Terry said:


> They need to be very small capacity cells to be affected by the difference in power draw between the first 6 cells and the the last 2....
> T1 Terry


I disagree that the imbalance issue is minor. These gizmos pull 8mA (mfg data). Let's say you only had them on during charging (not even during driving), charged 3 times a week and your charge took 8 hours. Over the course of your 3 months the power draw over the first 6 cells would be more than half an amp-hour. That's not insignificant. With any reasonable use it would be easy to get a pack imbalanced a few amp-hours over the course of a year. Not good.



swoozle said:


> I performed this mod on all 6 of my Cell Logs and now when attached to USB they give a "ERR: CELL VOLT" indication with no opportunity to do things like send the log file to the PC. When attached to the pack they work fine; it's just the USB connection that is now hosed.
> 
> A little searching indicates this is a common result. An email to Junsi got me direction to upgrade to the latest (v208) firmware, which didn't fix it.
> Has anyone else had this problem or know how to fix it besides undoing the mod?


Junsi suggested updating to v208 firmware, which not only DIDN'T fix the problem, it broke the ability to transmit data to the PC. I downgraded to v207, made a small 3-cell (old cell phone cells I had lying around) cheater pack and hook that up at the same time I'm on USB. Problem solved. A cheater pack isn't the most elegant solution but it works.


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## T1 Terry (Jan 29, 2011)

swoozle said:


> I disagree that the imbalance issue is minor. These gizmos pull 8mA (mfg data). Let's say you only had them on during charging (not even during driving), charged 3 times a week and your charge took 8 hours. Over the course of your 3 months the power draw over the first 6 cells would be more than half an amp-hour. That's not insignificant. With any reasonable use it would be easy to get a pack imbalanced a few amp-hours over the course of a year. Not good.
> 
> 
> 
> Junsi suggested updating to v208 firmware, which not only DIDN'T fix the problem, it broke the ability to transmit data to the PC. I downgraded to v207, made a small 3-cell (old cell phone cells I had lying around) cheater pack and hook that up at the same time I'm on USB. Problem solved. A cheater pack isn't the most elegant solution but it works.


I think these units require 4v minimum to operate with a current draw of 8mA, spread that across 6 cells, that's not a very big draw per cell. We have home power packs using these units 24/7 and we don't see cells 7 & 8 running away at the end of charge, this would be the best indicator of cell imbalance there is, it just doesn't happen. These are 180Ah cells, maybe 10ah cells in the electric pushbikes might have a problem but we haven't experienced one in over 12 mths continuous use.
We do not use balancing BMS boards, I can see no value in adding a potential failure point to solve a a problem that doesn't exist.

T1 Terry


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## simat (Mar 25, 2013)

Does anyone know if the Cell-Log 8M is physically the same as the Cell-Log 8S but without the serial to USB chip?

If so i was wondering if it is possible to tap into the serial lines from the ucontroller, are they still active?

Thanks


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## Roy Von Rogers (Mar 21, 2009)

simat said:


> Does anyone know if the Cell-Log 8M is physically the same as the Cell-Log 8S but without the serial to USB chip?
> 
> If so i was wondering if it is possible to tap into the serial lines from the ucontroller, are they still active?
> 
> Thanks


Yes they are the same except no usb. Btw I'm only using the first six to get away from the draw problem. I know about the jumper thing but really didn't want to do it. Beside I have five rows of six cells, this way one Cell Log for each row. The other reason for using only six, I use cat5 cable, and it only has eight wires, and one needs 9 for a total usage of this device.

Roy


Roy


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## simat (Mar 25, 2013)

Thanks Roy for the reply

I found some very interesting information about the 8M outputting data and also information on the unbalanced loading here
http://endless-sphere.com/forums/viewtopic.php?f=14&t=20142&start=150

It looks like the 8M might output serial data and one could tap into this via a TTL serial link, or you could easily optically isolate it to overcome any voltage differentials.

Simon


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