Building my new BMS.

[Patriot]

Ok, this is reallt weird now.

The LED slowly came back on, but is very faint.

I noticed that when I blow on the transistor, the LED gets brighter.

 

[Patriot]

Ok, I cleaned off the back of the board with some isopropyl and a small brush because there was some dust.

After thoroughly drying, I powered up again, and touched a transistor.

The LED is back on again, and bright again. Back where I started. :?

Now I have no idea what to do.

 

[Patriot]

I said to heck with it. I soldered in a new transistor, and powered up.

Now the main LED is almost completely off, but when I turn off the lights, I can see a small faint glow, but very faint.

It's not totally off.

Should I plug in the charger, and see what happens?

 

[fechter]

I think you're really really close.

What can happen sometimes is the residue from the flux can be partially conductive enough to turn on a transistor that doesn't need much current.

Alcohol may not remove all the flux residue.

Disconnect power, then use a small screwdriver or pick and scrape the board around the edges of the traces going to the small ground wire and the transistor leads. Scrape off the crusty hard flux residue, but be careful not to damage the traces. After scraping, then use alcohol again.

Go ahead and power it up after that.

 

[Patriot]

I'm already ahead of you. I noticed the LED flickering once in a while.

I took a toothbrush with tough bristles, and isopropyl. And scrubbed the bajeezuz out of the back side. I then used one of my hard bristle artist brush (dry) to clean off the front. The whole time I was getting the LED ON/OFF.

Yeah, I know I did it while plugged in. I was curious as to whether or not the left over flux/goo was really my problem.

Anyway. I finally got the LED OFF!!!

I plugged in the charger, and turned it on.

Within a minute after four or five channel LED's came on, the MAIN LED started flickering ORANGE/GREEN.

Even some of thew channel LED's are flickering as they come on. Keep in mind the cells are basically already charged.

- 3 mins later. Almost all cells are lit up, but the main LED is still orange/flickering.

14 cells fully lit. Tyhe main is still primarily orange and flickering with a little green inside.

Waiting for the last two.

Should it turn totally green when they are all lit? Or before that?

 

[Patriot]

OK,

this is weird. The last two cells are not coming on, but the charger is cycling (fan on/off). The last two LEDS are coming on slowly.

The MAIN LED has turned solid red again. ????? :?

Ok, it's trying to flicker a little, but I'm not sure what it's doing exactly.

 

[Patriot]

All cells are now fully lit.

The charger fan is cycling on/off, and as the fan kicks off, the Main LED tries to flicker.


-3mins later.

Well, I think it worked.

The charger is OFF, and the MAIN LED is now solid GREEEEEEENNNNNNN.

It turned solid green, then all the channel LED's are going off, as the charger has also turned green and the fan is off.

I assume this is good?

Here it is right now. Looks like it worked.

Any comments?

Any suggestions on what else I should do before I button this thing back up in the box??

 

[Patriot]

Richard, if you were here right now, I'd offer you a cold one....

for putting up with my crap.

I can't believe all I had to do was scrub the bloody board clean.

 

[GGoodrum]

Looks good. When all the LEDs are fully on, that is an indication that all the shunts are operating in full bypass mode, which means all the cells are full. Once all the opto outputs trip, it sets the ALL SHUNTS ACTIVE signal, which causes the SCR to turn off, and stay off, turning the main LED to fully green. It will stay this way until you cycle power on the charger.

When the individual LEDs start coming on, it actually causes the control circuit to cut off the charge circuit, which in turn cause the voltage for the cell to drop to the point the LED and the opto output turn off, which turns the charge current back on. This oscillation of on-off changes throughout the process. The color of the main LED is controlled by whether or not the charge current is on or off. When the charge current is on, the LED is red. When it is cutoff, the LED is green. Usually, its starts out red and then as the oscillation starts, by at least one cell getting full enough that its shunt starts bypassing current, the color will look orangish-yellowish. As the cells get fuller, the amount of time the charge current stays off increases, so the color starts to look more green than yellow.

One other thing I've noticed is that the individual cell LEDs will come on before the opto gets turned on for that channel, so initially the LED gets very bright, but then looks dim once the opto trips, and the oscillation starts. thats because they are in a duty cycle where they are off at least as much as they are on, but you really can't see the oscillation. As the cell gets completely full, the cell voltage doesn't drop so much during the off stage so the LED gets a bit brighter. It is when all the cells are at this point, when they are about as full as they are going to get, that the SCR cuts off the charger until power is reset.

-- Gary

 

[Patriot]

Ok, I "think" I understand.

I boxed it back up, and disconnected the charger.

When I reconnected the charger, the LED came on RED, which I assume is normal, as you stated above, it resets.

The battery fresh off the charger after sitting 10mins..

57.9Vdc.

That oughta crank the motor pretty good.

 

[fechter]

Congratulations. Looks like you got it. I could see the flux residue in your pictures. Alcohol doesn't do a real good job of dissolving it, but mechanical cleaning is good. The transistor input is very sensitive. I might need to add a resistor to prevent that in future versions.

It seems like your charger is doing some pulsing toward the end that's annoying, but it doesn't mater as long as all the cells come up and it goes green at the end. Mine does some similar pulsing, only faster. The main LED goes red when there is no charger output, this is normal.

As you've noticed, the thing gives off quite a bit of heat when it's balancing, so keep that in mind when packaging. Also be real careful not to short the board against anything when mounting. Good idea to unplug the battery when working around it.

 

[Patriot]

The box is made out of pressboard. Actually, a clipboard that I painted black.

Theboard is screwed into place, but uses plastic air hose for mounts and washers. So, no metal touches the pathways or components on the board.

You're right, this thing gets very warm. The top of my box originally had on a 1/8" slot for heat to escape, and the side of the box got very hot to the touch. Almost too hot to touch. I then cut off an additional 1/2" of material away to open up the top vent of the box. Now, the heat escapes much better. The plexiglass gets kind of hot, and the channel wires do get warm and flimsy from the rising heat. I hope this doesn't hurt the setup.

If I had room to install a small fan, I would, but I don't think there is any more room in the box for that. Would be nice though.

 

[Icewrench]

Patriot Very nicely done 8) 8)

Nice pack with a sweet bms to watch over it.

GGoodrum and Fechter should be proud for making these boards , circuits and endless assistance
available to us wanna be`s out here in cyber ville.


This place rocks

 

[dnmun]

congratulations, 99.99999999999999999% of the population will never achieve what you did, yo momma gonna be proud of you too.

has anyone ever used paint stripper with MEK to dissolve solder varnish? i use it to remove head gasket residue and wonder if it eats up flux too.

 

[Patriot]

^^^ It might eat up the matrix in the glass board as well. That's a potent mix. Not sure if I would chance that.

 

[fechter]

Don't use MEK! It will eat up the board and the components.

I had a can of this flux remover stuff at work that was really effective on rosin flux. I wish I knew what it was made of (can long gone). I usually just scape off the hard chunks with a tiny screwdriver blade and wash the rest with alcohol.

Once the pack gets reasonably balanced, the balancing time should be short enough that the board doesn't get hot for very long before the thing shuts off.

 

[Patriot]

^^^ This is good to know. The first time I charged the battery, half the cells came on within 10 minutes, then the rest took several hours. SLowly turning on, one by one, it really started heating up to the point of roasting my box. It didn't burn, but was very hot to the touch in some spots. I can imagine doing that everytime would eventually damage the insulation on the channel leads. So hopefully from now on, all cells will balance within minutes of each other.

 

[Patriot]

Just for referance.

After sitting for over a day now, my 48v/20ah Headway 38120S battery pack has settled at 54.4 volts.

I just got it installed in the bike, and hooked up for its maiden test to see if my controller was working.

It works very well. The wheel goes round-n'-round.


Thank you fecter and GGoodrum.

 

[The Mighty Volt]

Can somebody please direct me to a link for the Bill of Materials {B.O.M.} for the LifePo4 V2.6c BMS, thanks.

{My particular board is 24s}

Cheers.

 

[fechter]

I thought I had it, but in checking doesn't match the schematic. I'll look around some more. I suspect Gary has a copy.

 

[The Mighty Volt]

I thought I had it, but in checking doesn't match the schematic. I'll look around some more. I suspect Gary has a copy.

Thanks Fechter. If you don't have any luck, I will email AndyH who made and sold me the completed BMS I have.

Thanks.

 

[fechter]

Good luck getting ahold of Andy. He seems to have dropped off the radar.

Here's my best guess on the BOM:

647-UFW1H100MDD|26
810-FK28Y5V1C105Z|1
512-1N914T50A|50
78-TLUV5300|1
859-LTL1CHKFKNN|24
512-KSP94TA|2
512-KSP44TF|1
511-STP160N75F3|1
512-KSA931YTA|24
299-1M-RC|1
299-100K-RC|4
299-10K-RC|2
299-4.7K-RC|1
299-1k-RC|51
299-100-RC|73
299-10K-RC|4
270-75K-RC|24
270-180K-RC|24
286-6.8-RC|24
299-20K-RC|24
610-2N5060|1
512-LM78L12ACZXA|1
747-IXDF404PI|1
579-TC54VC2102EZB|24
512-FAN431LZXA|24
782-ILD2|24

I would suggest double checking the quantities and values to see if it matches the schematic.

 

[The Mighty Volt]

Thanks Fechter. I'll try that.

 

[Flip101]

Hey Patriot,

Could you please send me that thread by Gary on the design and instruction set for the battery management system? If you could that would be highly appreciated.

thanks
Flip101