CellLog 8 hacking

[Alan B]

Cell logs are smaller and take longer to boot up which is noticeable when plugging in four times. Medics are much larger, easier to read and boot faster. Medics are cheaper. Accuracy is not perfect on either. Either will unbalance packs if left connected.

My choice would probably be Medics.

[itchynackers]

My medics aren't as accurate as my cellogs (as compared with my Hyperion 1420i balance charger). Just yesterday my charger balanced to 2mv, and my cellog was off 3mv at most. My medic seems to unbalance the pack.

[bobale]

Cell logs are smaller and take longer to boot up which is noticeable when plugging in four times.

CellLogs can boot up immediately if you disable spash screen and warning about logging.

[EBJ]

Maybe I'm wrong, but I always thought the "difference in voltage" was the amount of voltage drop you want the total pack to experience. Example, my parallel pack is 20.5V hot (4.1v/cell). If I want the pack to drop only to 18.0V (3.6v/cell), then the difference alarm should be set to 2.5V. That being said, I don't enable the difference alarm, so I can't say for sure. Anyone else?

definitely not the case for me, or I wouldn't get very far having 'em set to delta .025

[EBJ]

ok, just confirmed the voltage-difference alarm isn't my problem.
I believe it to be a motor-controller issue.

[heathyoung]

For the more adventurous there are some 'interesting' hacks that can be done - I modified an 8S unit for checking the balance across 8S 12V batteries - its pretty simple to do, just some resistive dividers and some unity gain opamps.

[EBJ]

Do you think the cell-log could handle switching a relay for throttle cut-off AND sounding an alarm ?
..granted I could just use the same LVC relay to sound an alarm, but It would be easier wiring if I could just have the cell-log switch the LVC relay while also sounding an alarm.

[fechter]

The alarm output is rated for 500mA. If your throttle pull down circuit uses a 1k resistor, the maximum it will take is less than 5mA. Many piezo alarms will be well under 500mA, but check the ratings.

[EBJ]

The alarm output is rated for 500mA. If your throttle pull down circuit uses a 1k resistor, the maximum it will take is less than 5mA. Many piezo alarms will be well under 500mA, but check the ratings.

Thanks, but I just decided to run the alarm off the relay I was already using for the throttle pull-down.
(which is something like 25mA) It's a sure-bet this way since I know my cell-logs are able to power these relays.

[Pir]

For the more adventurous there are some 'interesting' hacks that can be done - I modified an 8S unit for checking the balance across 8S 12V batteries - its pretty simple to do, just some resistive dividers and some unity gain opamps.

Is this external circuit, or modification of cellogs schematic? May you describe your hack in detail?

[heathyoung]

Its an external circuit. I'll find the schematic and post it up. Very simple, I used it to help out someone trying to find a battery that was dying under load. He had 8 12V batteries in series.

[dumbass]

The alarm output is rated for 500mA. If your throttle pull down circuit uses a 1k resistor, the maximum it will take is less than 5mA. Many piezo alarms will be well under 500mA, but check the ratings.

Thanks, but I just decided to run the alarm off the relay I was already using for the throttle pull-down.
(which is something like 25mA) It's a sure-bet this way since I know my cell-logs are able to power these relays.

What type of relay are you using? Got a pic or link? I'm asking because I am intending to use a common ice cube relay and it's not power draw isn't indicated.

Bob

[EBJ]

i'm using the relays that used to be at AllElectronics surplus store....
I think they sell 'em at mouser. Lemme go find it...

http://www.mouser.com/ProductDetail/NEC/EA2-12NJ/?qs=BFfLPGsFlNdZQua2EckYEg%3d%3d

I believe these pull 11mA ... check the data-sheet.
I'm using 'em w/ the cell-logs and can confirm no problems.

[__Tango]

Just wondering...I want to access the data stream from my six CellLog 8s from my mac. I'm a coder, so once i get the device attached and i can talk to it, i should be able to make it happen. The problem is that i don't know much about connecting USB devices to computers and getting them to look like serial devices (like how the Arduino serial monitor works).

I'm assuming there's a chip driver i need or something, but i'm not sure. Anyone have any ideas? Or has anyone already done this?

Thanks!

[EVPowers]

Its an external circuit. I'll find the schematic and post it up. Very simple, I used it to help out someone trying to find a battery that was dying under load. He had 8 12V batteries in series.

I am very interested in this circuit.
Was the schematic posted somewhere?

I actually need it for 7, 12v cells in series, but hopefully there would be a way to adapt whatever you have already done.

Thanks in advance.

[heathyoung]

Sure, I have a version on the PC here I think.

For 7 cells, you just wouldn't connect to the cell 8 tap.

The input voltage range of the cell-log is 1.3-4.9V (and so is the alarm range). Obviously, you cant hook up a 12V battery to a channel, you would fry it!

So what to do... Divide it by 4. Use a resistive divider, with an opamp buffer (ie. gain of 1) powered off the 36V tap of the battery with a series zener diode of 6.1v (the opamp is rated for 44V max) . The reason for such a high voltage rail for the opamp is that the 8th output at 15V per cell (worst case) divided by 4 (3.75) and multiplied by 8 is 30V, and the opamp is not rail-to-rail, and so needs some headroom.

You get a voltage range of 2.5 (10.0V, dead empty for a 12V AGM) to 3.75V (15.0, highest cyclic charge voltage). You can use the alarm output to turn off your charger while the zener shunts (if you do this with your AGM's) do their thing, or warn you when you hit the LVC (or you have a single battery drop like a stone, or a massive imbalance occur - delta V).

The resistor values are calculated so that you have battery voltage/4. I have a PCB design around here somewhere as well.

At the highest voltage level (120V) the resistors will only be losing 0.9mA - and dissipating 0.1W.

Yes, you will unbalance the batteries eventually, but if you pulled from the whole pack voltage with an amplified zener reg, this would not be an issue. The dividers drop less than the self discharge rate anyway, so they are negligible.

[Pir]

Sure, I have a version on the PC here I think.

For 7 cells, you just wouldn't connect to the cell 8 tap.

...

Thanks for your schematics. But IMHO must be interconnections zeners 18V anodes with 100k and 5v1 anodes with output lines, or I'm wrong?

[megacycle]

I am hoping to use the cellog8 output to initialise a relay capacitor bms so it starts/stops shunting on the differential alarm.
I want it to trip something like a simple adjustable duty cycle 555 timer, i was hoping someone with electronics background could help me i'm more electrical inclined.
Thanks in advance

[heathyoung]

Sure, I have a version on the PC here I think.

For 7 cells, you just wouldn't connect to the cell 8 tap.

...

Thanks for your schematics. But IMHO must be interconnections zeners 18V anodes with 100k and 5v1 anodes with output lines, or I'm wrong?

The zeners are reversed biased - they form a voltage clamp when their rating is exceeded, basically forming a shunt ( that is a low impedance path) to protect the op amp input circuitry and cell log inputs if the voltage exceeds normal limits. In theory they aren't needed in practice they likely are.

You could omit them if you like but they are a protection mechani from spikes produced by motor emf etc.

[Pir]

The zeners are reversed biased - they form a voltage clamp when their rating is exceeded, basically forming a shunt ( that is a low impedance path) to protect the op amp input circuitry and cell log inputs if the voltage exceeds normal limits. In theory they aren't needed in practice they likely are.

You could omit them if you like but they are a protection mechani from spikes produced by motor emf etc.

OK! I understand this. It's very helpfull schematic to find bad accumulator in my ebike.

[NeilP]

I was going to start a new thread for this, but came across this thread

I just did a stupid thing... yes, OK another stupid thing..

Anyway. I came across a link for the firmware upgrader for the celllog ..so though I would give it a try.
http://www.jun-si.com/UploadFiles/Upgrader.rar

you guessed it, I screwed the cellog. The upgrader says it completely, but when ever I plug that celllog in to a pack I get this:

Err: Flash Memory.

Seems to fire up OK other wise, but have not tried any cell loggin yet.

Is there a way to fix this?

Neil

[NeilP]

Got it working myself in the end.
I checked the other cell logs I have, and noted that the Upgrader
http://www.jun-si.com/UploadFiles/Upgrader.rar
was not upgrading..it was downloading and installing the same firmware as was already isntalled.

SO I though I would see if it was possible to donwgrade to earlier if I manually d/loaded the firmware
From the address in teh donwloader, I took guesses at what the older firmware was called..not difficult to guess

http://www.jun-si.com/UploadFiles/CellLog(8S)_V208.bin was the same firnmware as I had on originally, and the others have.

I tried V206, V205 , and got d/loads for them all.
I then tried V208...and ended up with newer firmware. which flashed and worked with no errors.

http://www.jun-si.com/UploadFiles/CellLog(8S)_V208.bin
strange though that the upgrader software does not find this later firmware.

Can't immediately notice any changes in it though

[EVPowers]

I have a PCB design around here somewhere as well.

First, thank you so much for the pdf. I knew it must be possible, but didn't know how.

If you do come across the pcb design someday, I'd love to see it.

Great work and thanks again for sharing!

[whatever]

can i confirm something mentioned earlier, you can put an on/off switch on the negative wire to cell log to cut all power to it?
anyone done this?

[hillzofvalp]

i just saw a go kart team who had 4 cell logs on each of their 4 battery packs... that's a lot of loggin'