# Voltage logger in series?



## lnpurnell (Sep 27, 2012)

Good Morning EV'ers,

Can anyone tell me if there is a voltage logger such as a cellog8 the monitors each cell in series (taking one voltage reading at a time then moving to the next cell in the pack?)

I am looking at some options for a monitoring system for 15 cells of LiFePo4. I am thinking if i can get one central voltage logger to scan all 15 of my cells one at a time then not only do the costs go down for a system but the parasitic loads on each cell should be the same. (as it is only one device consuming power for a set time period).

I do not need it to actively balance my cells.

It would be required that it should indicate if a cell goes above or below a certain voltage; communication via Canbus or a serial connection would be good.

Thanks for your help.

Leigh.


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## frodus (Apr 12, 2008)

The cell-logs are 8-cell monitors, so you'd need 2 of them at a minimum for 15 cells.

The output of a cell-log is an alarm output that you can rig to a relay. It will alarm when its too high, or too low, but there is no separate alarm for each, just one output.


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## lnpurnell (Sep 27, 2012)

I understand the cellog8's only do the eight cells. I was asking for a larger version of this system that does 15 cells. Also do the cellog8's monitor the eight cells in series or simultaneously? I am looking for an equal parasitic load on all cells. 

Thanks
Leigh


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## frodus (Apr 12, 2008)

It's been discussed on here and Endless-sphere about how the cell-log taps off voltage from the first cell or two, so that might help. You should also read the manual, it taps off each cell, so it monitors all 8 cells at the same time.

Don't know of a 15s version, because it's kind of a wacky multiple of cells. Most BMS out there is in multiples of 4 for anything under 24 cells in series. Nothing that small that I know of uses CAN..... but higher dollar systems like Elithion or Orion will actually do it, but the cost might be prohibitive.


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## major (Apr 4, 2008)

lnpurnell said:


> I understand the cellog8's only do the eight cells. I was asking for a larger version of this system that does 15 cells. Also do the cellog8's monitor the eight cells in series or simultaneously? I am looking for an equal parasitic load on all cells.
> 
> Thanks
> Leigh


The CellLog8s draws very even (and very low) on the first 6 of the 8 channels. Cell 7 and 8 are the ones which get unbalanced from the first 6. So I just use 6 cells per device. For you, I'd say get 3 CellLog8s units and connect 5 cells to each. Less than $90 and you have it.

You can set the HVC and LVC alarms on each. Record charge and discharge. They claim you can monitor thru the mini USB port but I haven't tried. The com ports (and alarm outputs) aren't isolated. I bet a clever guy could isolate those com ports and convert to CAN.


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## pm_dawn (Sep 14, 2009)

Perhaps This one !

http://faktor.de/batterie-ueberwachung-zubehoer/kapazitaetsanzeiger/bm16lf-software-3-1.html

Got pretty much all the features of the cellog except the logging.


Regards
/Per


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## major (Apr 4, 2008)

pm_dawn said:


> Perhaps This one !
> 
> http://faktor.de/batterie-ueberwachung-zubehoer/kapazitaetsanzeiger/bm16lf-software-3-1.html
> 
> ...


Looks interesting Per. Any chance you can provide a link that comes through in English? I can't find a way to translate.

Thanks,

major


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## pm_dawn (Sep 14, 2009)

try using chrome as your browser and you can get automatic translation.

or

http://translate.google.com/transla.../kapazitaetsanzeiger/bm16lf-software-3-1.html

And the datasheet in the page is in english.

http://faktor.de/out/media/BM16LFspecificationV3_1.pdf

Could be a good alternative to using two cellogs.
I have not tried it.

Regards
/Per


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## major (Apr 4, 2008)

pm_dawn said:


> try using chrome as your browser and you can get automatic translation.
> 
> or
> 
> ...


Thanks Per,

With a little more google fu I found this: http://www.chargery.com/cellSaver16S.asp I'm tempted to buy one and give it a try. Do you know where a hick in Ohio can buy one? I sent Chargery an email asking him.

major


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## lnpurnell (Sep 27, 2012)

major said:


> Thanks Per,
> 
> With a little more google fu I found this: http://www.chargery.com/cellSaver16S.asp I'm tempted to buy one and give it a try. Do you know where a hick in Ohio can buy one? I sent Chargery an email asking him.
> 
> major


Hi Major,

Have you had any emails back from Chargery?

I am assuming that a basic version of this would not be hard to re-create by someone with some electronic background, anyone up for the challenge?

Leigh


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## major (Apr 4, 2008)

lnpurnell said:


> Hi Major,
> 
> Have you had any emails back from Chargery?


A sample unit should be on its way to me. I'll report once I get it  Pricing seemed to be about in line with the CellLog8 give or take a few $.


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## jumpjack (Sep 9, 2012)

major said:


> The CellLog8s draws very even (and very low) on the first 6 of the 8 channels. Cell 7 and 8 are the ones which get unbalanced from the first 6.


As per their blog, this happened on early versions, they now fixed the bug.


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## major (Apr 4, 2008)

major said:


> A sample unit should be on its way to me. I'll report once I get it  Pricing seemed to be about in line with the CellLog8 give or take a few $.


O.K. Here goes. First I'll post a bunch a pics.


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## major (Apr 4, 2008)

major said:


> O.K. Here goes. First I'll post a bunch a pics.












I use the Cell log8s as a comparison. The new thing is a BM16LP. The instructions are here: http://www.chargery.com/doc/Chargery%20BM16LP%20specification%20%20V3.0.pdf Not too bad for a Chinese product and it appeared to operate and function per the instructions so I won't repeat. It is also available in a BM16LF version for LiFePO4 cells. I have not tested it to the limits on either charge or discharge so I do not know first hand how the alarm works. 

All I did was to connect to a 12S LiNCM module (EnerDel) and compare to the CellLog8s and Fluke multimeter measurements. I'll compile those measurements in a spreadsheet and post later. Both the CellLoggers and BM16 had cell voltage deviations of 10, maybe 15 milliVolts from the Fluke readings. The CellLog has a set-up calibration which I never bothered doing; the BM16 has no calibration.

As you can see, the BM16 is a simple circuit board and small screen which is shrink wrapped (in clear as it comes out of the box). The first screen is a multicolor fuel gauge (SOC), not available with CellLog8s. The BM16 comes with 2 temperature sensors, and a plug for the alarm output. Temps appeared to read correctly.

On the 12S EnerDel module I split the monitor leads into 2 separate JST 7 pole plugs. I use one each for 6 channels of the 8 available on the CellLog8s. Using these for the BM16LP, the first 6 cells display as cells 1 thru 6 and the second 6 cells as cells 9 thru 14. Works for me that way and no sparks 

I like the plastic case on the CellLog over the shrinkwrap BM16. The CellLog has a data recording capability which I really like and use whereas the BM16 does not. 

Nice about the BM16LP is:
Smaller footprint.
You can turn it off with a button push as opposed to unplugging it. I have yet to verify it has no parasitic drain.
Easy to read SOC gauge.
Less costly. (Maybe 20% less delivered than two CellLog8s. I hate to post actual prices on products from others)

I kinda like the little thing and will put it to use and maybe get a couple more. My eTractor would take 2 of these instead of 4 CellLoggers and look a little cleaner on the dashboard and easier to read.

There ya go,

major


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## jumpjack (Sep 9, 2012)

major said:


> The CellLog has a data recording capability which I really like and use whereas the BM16 does not.


 I think such a device is totally useless on an EV without logging function!
I notified this to the chinese manufacturer; he replied "what is logging capability?"



> Less costly. (Maybe 20% less delivered than two CellLog8s. I hate to post actual prices on products from others)


On ev-power.eu it costs half than on any other site! I guess they are not aware of non-logging variant version!


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## major (Apr 4, 2008)

jumpjack said:


> On ev-power.eu it costs half than on any other site! I guess they are not aware of non-logging variant version!


I don't see the BM16LP device listed there. What are you talking about  Please provide a link to a webpage listing price for the BM16LP. Thanks.


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## jumpjack (Sep 9, 2012)

major said:


> I don't see the BM16LP device listed there. What are you talking about  Please provide a link to a webpage listing price for the BM16LP. Thanks.


Sorry, bad quoting: I was talking about the CellLog8s:
http://www.ev-power.eu/en/By-Brand-...port.html?listtype=search&searchparam=celllog


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## major (Apr 4, 2008)

*BM16LP Update*

I left the BM16LP connected to a 12S battery overnight. I checked on it this morning. GOOD news: The alarm works. BAD news: The alarm was working.

Channel #10 indicated a low cell by about 200mV which was enough deviation to trigger the alarm. The unit had turned its screen off. The unit was beeping fairly loudly and the big LED was flashing quite brightly. I pushed a button and the screen lit up. I could scroll and read cell voltage.

So I proceeded to investigate. Connected CellLoggers. Used different battery. Different wires. Problem is with the BM16LP device as far as I can tell. It follows on channel #10 regardless of the battery or wires. The second battery was balanced to 8mV. Channel #10 still showed way low, about 150mV. And channel #11 reads a tad high, about 50mV. Looks like a problem with the BM16LP.

I sent a report to the source, Jason. We'll see how the handle it. But for now, I'd suggest you hold off on these things.


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