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Voltage logger in series?

7K views 17 replies 5 participants last post by  major 
#1 ·
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.
 
#2 ·
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.
 
#3 ·
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
 
#5 ·
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.
 
#4 ·
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.
 
#9 ·
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
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
 
#18 ·
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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