CellLog 8S battery monitor and logger - any reviews?

[AndyH]

The PakTrakr - though more expensive - can monitor up to 48 series cells with one unit and can format a serial datastreem for off-line analysis or real-time display.

The PakTrakr remotes each monitor 8 cells. Each remote is powered from the first four cells it's monitoring, In addition, the last remote in the string also powers the LCD display.

I know it's more money, but if you need to monitor up to a 48S pack with a commercial plug-n-play device, it's hard to beat.

 

[pm_dawn]

The Hardy BMS can do logging and comes in different sizes.

http://www.convertthefuture.com/BMS.php

regards
/Per

 

[cell_man]

Thanks for the info guys. I couldn't get onto the PakTrackr site but I've made a bit of a test rig for just checking 8 series cells for now using the cell log 8. Here's a few pics below. I stole some ideas from the RC site for a resistive discharger using the cell log 8 to terminate the test when it hits the low volts alarm or whatever you've selected. It uses 1000W 1ohm resistors each connected to a power relay and I've brought the switches back to my desk and a latching relay so once it's alarmed once it stays disconnected. It's still very much a work in progress but it at least gives me fairly quick method to confirm that a group of cells are playing nicely together With a few simple calcs in excel I can get a pretty good idea of the capacity of each cell by simply multiplying the pack voltage by however many resistors have been switched in. It's also given me few insights into how to reduce the resistance between the tabs and the bus bar. My thinking now is that metal polish is your friend and a big surface area is unnecessary :wink:

View attachment CIMG0475.JPG

View attachment CIMG0474.JPG

View attachment CIMG0476.JPG

View attachment CIMG0477.JPG

View attachment CIMG0478.JPG

Please try to look beyond the poor choice of wood (it looked better in the shop before I had cut into it ) that I used and the odd cable as I ran out of the the other type and everywhere has now closed for Chinese New year. Next is toggle clamps, some high current 3.65-3.7V chargers or just a few more Ichargers and then repeat the setup 2 or 3 more times so I can run more tests at 1 time. Constant current would also be nice as would a method to maybe automate the test procedure and maybe data log the current. I want to go constant current and individual cell testing but it's not easy or cheap to find test equipment that can adequately test these high capacity high C cells. A CBA3 with external load is already pretty expensive, try multiplying that by 10 and then adding the beta software than enables them to be run on a single PC. Any suggestions for cell level test equipment that can test say 10 cells simultaneously and doesn't cost the price of a not so small car would be greatly apprceiated....

 

[Doctorbass]

Wow.. that's an impressive test setup cell man!

Great idea for terminating resistive load using celllog8 trigger!


Keep us informed!

Doc

 

[cell_man]

Thanks Doc but I'm afraid I can't take all the credit. Below is a link that details the circuit. All I have done is use the contact that would ordinarily have the load connected feeding some big 60A relays which I switch in and out manually.

http://www.rcgroups.com/forums/showthread.php?t=1131817

My plan is to possibly add some more shelfs to enable testing several 8S sets of cells at 1 time and also add some more resistors so I can do some higher current pulse tests maybe an additional data logger that can also have some programmable control. The cells are not compressed so I don't like the idea of pushing the cells too hard. Maybe also add some modified meanwell chargers and have a few charging stations or just go with a few Ichargers. Running into a 0.5ohm load discharges a set of cells in less than 30 mins so even with only 1 setup you can get through quite a few cells. The toggle clamps will be great if they work ok. The gym gloves are to save my hands, those bloody terrible G clamps have ripped my hand to shreds....

It's also given me a good insight into how the cell tabs work when clamped. I was having lots of trouble initially and was having to get the clamps really tight as even a little loss in the connection between tab and bus bar is very obvious when looking at the cell log data. I would put my meter between tab and bus bar and you could easily see which was the problem. Using some Autosol metal polish on the tab improved the situation dramatically and got the losses right down. There is always a bit more loss on the alloy tab but you can get it down to 2 or 3mV (according to my not so expensive meter) but the plated copper tab can be 1mV or so at circa 50A. Without polishing these figures could easily be 10mV or more. Anyway sorry to digress, but it does show what a great little tool the cell log is.

 

[j3tch1u]

It's also given me a good insight into how the cell tabs work when clamped. I was having lots of trouble initially and was having to get the clamps really tight as even a little loss in the connection between tab and bus bar is very obvious when looking at the cell log data. I would put my meter between tab and bus bar and you could easily see which was the problem. Using some Autosol metal polish on the tab improved the situation dramatically and got the losses right down. There is always a bit more loss on the alloy tab but you can get it down to 2 or 3mV (according to my not so expensive meter) but the plated copper tab can be 1mV or so at circa 50A. Without polishing these figures could easily be 10mV or more. Anyway sorry to digress, but it does show what a great little tool the cell log is.

terrific test setup--i see things are moving along. happy chinese new year--the whole country has shut down!

haven't tried it yet, but maybe the tabs need to be really flattened out before clamping. maybe try kneading out the little kinks with a piece of wood (with a rounded edge) and let us know if that helped any.

 

[cell_man]

It's also given me a good insight into how the cell tabs work when clamped. I was having lots of trouble initially and was having to get the clamps really tight as even a little loss in the connection between tab and bus bar is very obvious when looking at the cell log data. I would put my meter between tab and bus bar and you could easily see which was the problem. Using some Autosol metal polish on the tab improved the situation dramatically and got the losses right down. There is always a bit more loss on the alloy tab but you can get it down to 2 or 3mV (according to my not so expensive meter) but the plated copper tab can be 1mV or so at circa 50A. Without polishing these figures could easily be 10mV or more. Anyway sorry to digress, but it does show what a great little tool the cell log is.

terrific test setup--i see things are moving along. happy chinese new year--the whole country has shut down!

haven't tried it yet, but maybe the tabs need to be really flattened out before clamping. maybe try kneading out the little kinks with a piece of wood (with a rounded edge) and let us know if that helped any.

Thanks for the comments. Obviously it's not ideal and it's put back other things I should also be doing but I'm sure it enables a pretty good indication of at least the relative performance of the cells to ensure they are playing nicely together. It cost a hell of of a lot less than 8 CBA3 with external loads plus the rather expensive software required to run them on a single PC. The automatic cut out is great on the cell log 8 and I'd highly recommend a similar setup if you want to check a pack. I only paid about 10USD a pc for the resistors and the big relays were about 8USD a pc. Got some smaller supposedly 30A relays that are only 1usd a pc that would probably do the job but for constant use and consistent results I thought what the hell why not splash out the big $$$s Constant current and some automation would be nice but that will have to wait.

It's the same with perfectly fresh virgin tabs.. if you know what I mean I was only using slightly crappy G clamps which are not ideal but I was doing them up really tight. For sure a few seconds cleaning the tabs with some autosol metal polish definitely helped. I go along with my DMM between tab and interconnecting bus bar when it's under load and it's very easy to see where you have a less than perfect connection. For a permanent installation it's probably adviseable to clean any polish residue with a cleaning alchohol (maybe IPA) and maybe even seal them with a bit with some silicone grease if you want to be really thorough to reduce any oxidisation over time.

Happy New Year to you too Ben. The whole place is shut down here too. Including my shipping company for a rather extended holiday...

 

[olaf-lampe]

Any suggestions for cell level test equipment that can test say 10 cells simultaneously and doesn't cost the price of a not so small car would be greatly apprceiated....

I just ordered a simple evaluation board with ethernet and ATMega32 proc for only 15$
http://www.pollin.de/shop/dt/MTQ5OTgxOTk-/Bausaetze/Diverse/Bausatz_AVR_NET_IO.html
Some clever folks wrote some nice webserver app for it and it should be easy ( for a software geek ) to build an automated battery testbench off it. It has 4 ADC's, 4 digital inputs ( for celllog alarms ) and 8 digital outputs onboard. There are some addon boards with more options available. If there is a question about the german manual, just ask me. I'm happy to help!
In fact I hope some would join my project and help me with the automated software

With such a board it would be possible to test and logg up to four 8s-battery packs at once. Each is observed by a celllog and they could be switched between charging and discharging using the alarm levels from celllog.
I'm thinking of using one charged pack as source for charging another empty pack and vice versa. This way you only have to add the energy which is lost by energy conversion. For a functional test you would only need a 1-2C testbench...
Or do you want to stress every cell with 30C?
I have played around with dcdc converters from 48V ( 36-75) to 3.3V @ 15/30A. They are trimmable up to 3.7V which is perfect for single cell charging ( thanks Jeremie Harris for the tip ). Think of using two 8s-packs as power source and charge any number of single cells with it.

Example QMT100-48-3.3N:
http://www.datasheetarchive.com/pdf-datasheets/Datasheets-7/DSA-123485.pdf

-Olaf

 

[cell_man]

Any suggestions for cell level test equipment that can test say 10 cells simultaneously and doesn't cost the price of a not so small car would be greatly apprceiated....

I just ordered a simple evaluation board with ethernet and ATMega32 proc for only 15$
http://www.pollin.de/shop/dt/MTQ5OTgxOTk-/Bausaetze/Diverse/Bausatz_AVR_NET_IO.html
Some clever folks wrote some nice webserver app for it and it should be easy ( for a software geek ) to build an automated battery testbench off it. It has 4 ADC's, 4 digital inputs ( for celllog alarms ) and 8 digital outputs onboard. There are some addon boards with more options available. If there is a question about the german manual, just ask me. I'm happy to help!
In fact I hope some would join my project and help me with the automated software

With such a board it would be possible to test and logg up to four 8s-battery packs at once. Each is observed by a celllog and they could be switched between charging and discharging using the alarm levels from celllog.
I'm thinking of using one charged pack as source for charging another empty pack and vice versa. This way you only have to add the energy which is lost by energy conversion. For a functional test you would only need a 1-2C testbench...
Or do you want to stress every cell with 30C?
I have played around with dcdc converters from 48V ( 36-75) to 3.3V @ 15/30A. They are trimmable up to 3.7V which is perfect for single cell charging ( thanks Jeremie Harris for the tip ). Think of using two 8s-packs as power source and charge any number of single cells with it.

Example QMT100-48-3.3N:
http://www.datasheetarchive.com/pdf-datasheets/Datasheets-7/DSA-123485.pdf

-Olaf

Thanks Olaf,

that's all really useful info for me. I wouldn't be up to sorting the software though I'm afraid. I really should have paid more attention in the Programming modules in the B.Eng.... I have a couple of good friends that are electronic design engineers and 1 should be coming to visit soon so maybe i can recruit him to help me out a bit. For a test bench it doesn't need to be crazy current, 2C or a bit more is ok. It's nice to get a bit of current going through them though as at least that gets a little heat into the cells to keep it a bit consistent. Kind of cold in this apartment these days and that will not do the results any favours at low discharge levels. Some high current (100A or so) pulses are also nice to confirm the internal impedance but for sure it makes no sense to flog a customers cells to death on the test bench before delivery...

I didn't get what you were saying about using 1 pack to charge some other cells unless there was any way that you could control the DC-DC convertors so that they could behave like a constant current load and then measure the discharge on them. If that was do able yeah great but it sound rather difficult to achieve. Or maybe I've got the wrong end of the stick. Anyway thatnks for the info, I'll look into it and we can maybe have a chat about it later.

Sorry guys if I've dragged this thread a bit off topic

 

[olaf-lampe]

This thread is still related to the cellLog and shows the opportunities of this little gem.

My proposal about the dcdc converters is more related to a long term battery test where only cycles and capacity degradation counts . But also a real life scenario isn't drawing constant current from the batteries. The external trim resistor for the dcdc converter can be used to regulate current but needs a bit of extra tinkering.

Maybe we should open a new thread for a testbench project...
Olaf

 

[cell_man]

This thread is still related to the cellLog and shows the opportunities of this little gem.

My proposal about the dcdc converters is more related to a long term battery test where only cycles and capacity degradation counts . But also a real life scenario isn't drawing constant current from the batteries. The external trim resistor for the dcdc converter can be used to regulate current but needs a bit of extra tinkering.

Maybe we should open a new thread for a testbench project...
Olaf

I'm all for that Olaf. We can start a fresh thread and I think it would give me and others good information about how to achieve a reasonable test method and equipment for basic test systems or even not so basic test systems. I also tend to agree on your point about constant current. Ok it makes nice graphs but in real terms it means that you are actually ramping up the load by maybe 40% at the end of the discharge just when it's least able to deal with it. Temperatures also seem to rise more quickly at the end of the discharge too so at high discharge levels it's not so kind to the cells IMO. I mean most will not add a handful of throttle just when the pack is feeling like it's running low, especially if you've still got a few ks before you get home.

I'm hoping I can get my soon to visit Design Engineer friend to get a bit involved. He's designed all sorts and I'm sure with a bit of guidance from him we could come up with a few neat little tricks but on my own I've just got too much ground to cover. If I can find a reasonably cost effective source of DCDC convertors as per your data sheet I would definitely have a good use for them.

 

[olaf-lampe]

If you are looking on ebay for dc/dc converter 48V 3.3V you'll find plenty of auctions. Most of them are old stock and not ROHS compliant. But in our usecase it doesn't matter. The QMT100 converter is sold 3pcs for 10$ but has a low efficiency.
My favorite is the TYCO KW015A0F41 which I also found on alibaba, but now I couldn't find it back.

BTW you can also find many 48V AC/DC power supplies from old telecom UPS's. I have a 1.7kW PSU that could feed many dcdc bricks at once 8)
Olaf

 

[olaf-lampe]

I started a new thread about the AVR NetIO board here:
http://endless-sphere.com/forums/viewtopic.php?f=14&t=16276
Olaf

 

[geoff57]

Hi
there has been talk about where can you get the 9 way JST connector from for the Cellog8, I've had a word with keywin who supplys me with my infineon controllers and has got hold of balance cables at a very good price for me before and they are the same type of connector. He said he can get them there is no problem there already wired up no need to get out a crimper, there should be the demand for him before he goes and buys them though I can supply the UK and if we ask him nicely knuckles might supply the US how many of you out there want these 9 way connectors or shall I tell keywin not to bother.

Geoff

 

[j3tch1u]

i picked up a couple of these: http://www.saelig.com/UI1E/UI1E5.htm

going to see if i can tap into the cell-logs via usb (to avoid opening them) and maybe mash-up the data.

blog on making arduino a usb host:
http://www.underwater.ca/blog/connecting-vdp1-to-arduino

 

[cell_man]

i picked up a couple of these: http://www.saelig.com/UI1E/UI1E5.htm

going to see if i can tap into the cell-logs via usb (to avoid opening them) and maybe mash-up the data.

blog on making arduino a usb host:
http://www.underwater.ca/blog/connecting-vdp1-to-arduino

Hi Ben,

is this device gonna enable several cell log8 connected to a big pack to be monitored simultaneously? What was your intentions for the data?

 

[j3tch1u]

i picked up a couple of these: http://www.saelig.com/UI1E/UI1E5.htm

going to see if i can tap into the cell-logs via usb (to avoid opening them) and maybe mash-up the data.

blog on making arduino a usb host:
http://www.underwater.ca/blog/connecting-vdp1-to-arduino

Hi Ben,

is this device gonna enable several cell log8 connected to a big pack to be monitored simultaneously? What was your intentions for the data?

i don't see why not (assuming the firmware is able to negotiate a connection). that vdip2 supports 2 usb devices--2 cell-logs (ie 16 channels). primarily, i just want to grab the cell voltages to interlace with ntsc video for on-screen display.

 

[cell_man]

Sounds good. Keep us updated.

 

[olaf-lampe]

AFAIK you can't plug more than one cellLog's USB connection on one PC at the same time. The USB output of the CellLog is not optocoupled.

-Olaf

 

[cell_man]

Yes you are quite right Olaf. I didn't think of that with regards to Bens suggestion of connecting 2 cell logg to the same device.

 

[j3tch1u]

paul, this thread may be useful for you:
http://www.rcgroups.com/forums/showthread.php?p=14067332#post14067332

however, i don't think they are chaining multiple cell-logs together so it doesn't address the power isolation issues (usb and alert outputs)

 

[cell_man]

Yeah I saw that on rcgroups. It's very neat. A way to log current data along with the voltage data would make my test kit almost complete. If you could also take voltages directly from the tabs instead of from the interconnection between tabs it would be near perfect, well apart from the constant currrent load of course... I'm thinking a labjack is the way to go in the future but they need programming so it's not a pretty big job, for me at least.

 

[pvorlicek]

Hi
there has been talk about where can you get the 9 way JST connector from for the Cellog8, I've had a word with keywin who supplys me with my infineon controllers and has got hold of balance cables at a very good price for me before and they are the same type of connector. He said he can get them there is no problem there already wired up no need to get out a crimper, there should be the demand for him before he goes and buys them though I can supply the UK and if we ask him nicely knuckles might supply the US how many of you out there want these 9 way connectors or shall I tell keywin not to bother.

Geoff

I would be interested in 5 of these. Are we looking at about $5 each?

Preston

 

[evblazer]

I did a quick search for 9 pin jst and supposidly they are being used on some HO-Scale model trains for decoder connections.
I wonder if these would be any good?
http://www.litchfieldstation.com/xcart/home.php?cat=76

Scroll to the bottom and they have one for <$2
"JST 9-pin Wire Harness by TCS
7 inch wires to a JST 9-pin inline connector. Single harnesses from Train Control Systems
"
Edit: Denied wrong size.

 

[recumbent]

... they are being used on some HO-Scale model trains.
http://www.litchfieldstation.com/xcart/home.php?cat=76

Scroll to the bottom and they have one for <$2
"JST 9-pin Wire Harness by TCS
7 inch wires to a JST 9-pin inline connector. Single harnesses from Train Control Systems
"

Good find!!! They also list (on same page) a package of 5 JST connector from another company. Which one is better?

Thanks "evblazer" for this link.