"Zephyr" - Finally, the "v4" Fechter/Goodrum/Hecker BMS...

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Re: "Zephyr" - Finally, the "v4" Fechter/Goodrum/Hecker BMS.

Post by fechter » Sep 20 2011 8:55am

OK guys, got it.

The problem was with higher charge currents/smaller cells, the on time during cycling was too short for the EOC detector to trigger. In earlier testing, we were mostly using very large cells at a lower charge rate, so the timing was not an issue.

The solution will be to add a 1N914 diode to enable the EOC detector during the HVC delay time. My test setup used no cells (worst case) so the timing cycle was as short as possible.

The diode needs to go from the base of Q2 to U3 pin 7 or the gate of the main FET. The cathode (end with the black band) goes to Q2.

Here is a layout diagram showing the location of the diode (in blue). I think you can bend the legs of the diode around the existing resistor legs and solder it in.
EOC Diode mod.jpg
EOC Diode mod.jpg (154.47 KiB) Viewed 2452 times
The anode side of the diode can go to either end of R14.

Once you install the diode, you should be able to crank the charger voltage up a bit and still get good end of charge shutdown.
Some cycling is normal if there is significant cell imbalance, but it should shut down after a reasonable amount of time. Having the diode will make variations in charger voltage less critical.
"One test is worth a thousand opinions"

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Re: "Zephyr" - Finally, the "v4" Fechter/Goodrum/Hecker BMS.

Post by steveo » Sep 20 2011 9:42am

fechter wrote:OK guys, got it.

The problem was with higher charge currents/smaller cells, the on time during cycling was too short for the EOC detector to trigger. In earlier testing, we were mostly using very large cells at a lower charge rate, so the timing was not an issue.

The solution will be to add a 1N914 diode to enable the EOC detector during the HVC delay time. My test setup used no cells (worst case) so the timing cycle was as short as possible.

The diode needs to go from the base of Q2 to U3 pin 7 or the gate of the main FET. The cathode (end with the black band) goes to Q2.

Here is a layout diagram showing the location of the diode (in blue). I think you can bend the legs of the diode around the existing resistor legs and solder it in.
EOC Diode mod.jpg
The anode side of the diode can go to either end of R14.

Once you install the diode, you should be able to crank the charger voltage up a bit and still get good end of charge shutdown.
Some cycling is normal if there is significant cell imbalance, but it should shut down after a reasonable amount of time. Having the diode will make variations in charger voltage less critical.
thanks for looking into this fechter, I will try this mod when i have the chance...

as i mentioned earlier i was able to set the charger so each cell his 4.10v and then the main led goes to green

with this mod, will it allow me to set the voltage of the cells to 4.15 of 4.20v for lipo?... any ideas roughly? how about for a life cells?

thanks
-steveo
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Re: "Zephyr" - Finally, the "v4" Fechter/Goodrum/Hecker BMS.

Post by Gregb » Sep 20 2011 7:32pm

I have asked this question on another thread to no avail and have tried finding it on the mouse catalogue.
Does anyone know the name /no. of the plug for the cell-log O/P plug and where it can be obtained?
thanks
Greg

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Re: "Zephyr" - Finally, the "v4" Fechter/Goodrum/Hecker BMS.

Post by fechter » Sep 21 2011 12:06am

steveo wrote:thanks for looking into this fechter, I will try this mod when i have the chance...

as i mentioned earlier i was able to set the charger so each cell his 4.10v and then the main led goes to green

with this mod, will it allow me to set the voltage of the cells to 4.15 of 4.20v for lipo?... any ideas roughly? how about for a life cells?

thanks
-steveo
It won't change the voltage where the shunts come on but will allow a little more variation in charger voltage and still have a reliable shutoff. With the EOC pot turned up higher, you can run the charge current higher toward end of charge to speed things up.
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Re: "Zephyr" - Finally, the "v4" Fechter/Goodrum/Hecker BMS.

Post by fechter » Sep 21 2011 12:08am

Gregb wrote:I have asked this question on another thread to no avail and have tried finding it on the mouse catalogue.
Does anyone know the name /no. of the plug for the cell-log O/P plug and where it can be obtained?
thanks
Greg
I've never been able to find them. If you find some, let us know. I wish they used a more common connector.
"One test is worth a thousand opinions"

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Re: "Zephyr" - Finally, the "v4" Fechter/Goodrum/Hecker BMS.

Post by damcard » Sep 21 2011 10:56am

Will the following link be back up soon? -Damcard

Order site: http://www.tppacks.com/products.asp?cat=26

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Re: "Zephyr" - Finally, the "v4" Fechter/Goodrum/Hecker BMS.

Post by GGoodrum » Sep 21 2011 11:01am

damcard wrote:Will the following link be back up soon? -Damcard

Order site: http://www.tppacks.com/products.asp?cat=26
Yes, in another week, or so. In the meantime, PM me if you need something.

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Re: "Zephyr" - Finally, the "v4" Fechter/Goodrum/Hecker BMS.

Post by Zenid » Sep 21 2011 1:19pm

Gregb wrote:I have asked this question on another thread to no avail and have tried finding it on the mouse catalogue.
Does anyone know the name /no. of the plug for the cell-log O/P plug and where it can be obtained?
thanks
Greg
Are you talking about the 8S JST-XH connectors?:
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Re: "Zephyr" - Finally, the "v4" Fechter/Goodrum/Hecker BMS.

Post by Zenid » Sep 21 2011 1:24pm

Thanks a lot! I'll get round to this soon...
Does this fix the EOC issue generally (it not shutting off in either mode with the voltage set too high), or just the pulse mode EOC issue? Is the 1N914 diode the "1N914_T50A" that is used elsewhere on the control circuit?

Thanks
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Re: "Zephyr" - Finally, the "v4" Fechter/Goodrum/Hecker BMS.

Post by fechter » Sep 21 2011 2:12pm

Zenid wrote:Thanks a lot! I'll get round to this soon...
Does this fix the EOC issue generally (it not shutting off in either mode with the voltage set too high), or just the pulse mode EOC issue? Is the 1N914 diode the "1N914_T50A" that is used elsewhere on the control circuit?

Thanks
Almost any diode will work. Yes, I used the same one used elsewhere on the board.

This will fix the problem where it goes into cycling and gets stuck in that mode.
If you set the charger voltage way too high, the shunts will be full on at end of charge and you would need to adjust the EOC pot higher than about half way to make sure it turns off, but it should still turn off.
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Re: "Zephyr" - Finally, the "v4" Fechter/Goodrum/Hecker BMS.

Post by Zenid » Sep 22 2011 12:41am

I've done the mod. Since I had it open, I took it as an opportunity to fit the second Q3 FET, so that I can run it with a 15A or 20A charger later on.

I elected to mount the diode on the underside of the board. The diode leg had just enough room to fit in with the FET leg, which made it nice and straightforward to double up the two jobs.

[EDIT] Corrected as per Richard's suggestion in the following post. It goes to the gate not the source :oops:. I moved it across to the rail serving the gate (shown at the bottom of the picture).

The other end just went to the bottom of the middle pin of Q2.

Image
[EDIT] Photo of corrected layout as per Richard's suggestion

It'll be some time before I know for sure that this works. I'm still fine-tuning the charger voltage and EOC. It seems that unless I have it just a bit lower than the 86.4V ideal (3.6V per cell), then it sometimes sticks and never switches off. The voltage seems to fluctuate a little according to various factors, and if it goes over a certain threshold then it will just run away, never turning off and just getting hotter and hotter. It looks to me that - for whatever reason - a slightly lowered voltage is what my system is happiest with. All the cells end up nicely balanced once they've settled, and they all discharge in step with one another right up until they cliff-dive at the end.

I've set to see if this mod has fixed the pulse mode yet. One thing I did notice while tinkering, is that once I ramped up the voltage again, pulse mode came on by itself. Is this a good way of 'forcing' it to see if it works, and also calibrating the EOC with this mode?
Last edited by Zenid on Sep 22 2011 10:50pm, edited 6 times in total.
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Re: "Zephyr" - Finally, the "v4" Fechter/Goodrum/Hecker BMS.

Post by fechter » Sep 22 2011 7:27pm

I can see from the pic that the diode is going to the wrong leg on the FET. It should go to the gate leg, which has the skinny trace. It looks like maybe you can just snip one end off and move it over to on top of the trace leading to the gates.

Once you get that moved over, yes, you should be able to get it going in the throttling mode and dial up the pot and it should shut off. If you have a way to measure the current it may be helpful.

During normal operation, near end of charge you may or may not see it go into the throttling mode depending on how much imbalance there is in the cells. After that it should shut down. I think if you have the pot set high (more CW), it will shut down a bit early which may be better for the cells.
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Re: "Zephyr" - Finally, the "v4" Fechter/Goodrum/Hecker BMS.

Post by Zenid » Sep 22 2011 10:40pm

fechter wrote:I can see from the pic that the diode is going to the wrong leg on the FET. It should go to the gate leg, which has the skinny trace. It looks like maybe you can just snip one end off and move it over to on top of the trace leading to the gates.
Doh! :oops: It was a long day...
Image

Thanks for the suggestion! Easy fix.
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Re: "Zephyr" - Finally, the "v4" Fechter/Goodrum/Hecker BMS.

Post by fechter » Sep 23 2011 9:09am

Looks good.
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Re: "Zephyr" - Finally, the "v4" Fechter/Goodrum/Hecker BMS.

Post by Zenid » Sep 23 2011 12:34pm

fechter wrote: Once you get that moved over, yes, you should be able to get it going in the throttling mode and dial up the pot and it should shut off. If you have a way to measure the current it may be helpful.
Yes. The great thing about the BMSBattery charger is they have a display that is switchable between voltage and current. It's in my little video (25 seconds in) from when I first tested the board:
http://www.youtube.com/watch?v=QN6tYkzu ... re=related

Now I've put the extra main MOSFET on, should I be okay with a 15A or 20A charger? I built it solidly with nice thick gauge wire everywhere. Are there any issues I should be aware of before I try it with anything more powerful (apart, of course, from making sure the EOC is stable and works okay now)?
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Re: "Zephyr" - Finally, the "v4" Fechter/Goodrum/Hecker BMS.

Post by Zenid » Sep 23 2011 8:54pm

Incidentally, here's my own pretty picture of where the diode goes, from my blog:
http://zenid10.files.wordpress.com/2011 ... x12001.jpg
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Re: "Zephyr" - Finally, the "v4" Fechter/Goodrum/Hecker BMS.

Post by fechter » Sep 24 2011 10:02am

Zenid wrote:
Now I've put the extra main MOSFET on, should I be okay with a 15A or 20A charger? I built it solidly with nice thick gauge wire everywhere. Are there any issues I should be aware of before I try it with anything more powerful (apart, of course, from making sure the EOC is stable and works okay now)?
Should be no problem. A single FET can handle up to about 20A. The current shunt will get hot, but it is made to take it. Just avoid having any wires in contact with it as the insulation could possilby melt.
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Re: "Zephyr" - Finally, the "v4" Fechter/Goodrum/Hecker BMS.

Post by Gregb » Sep 29 2011 2:43am

Still not terribly impressed with the instructions. In the Charge Control section Test It says use a current limited PS set to 100mA but no mention of initial voltage. It then says turn voltage up to 20V... From what ???
There is still no instruction for 8 cell units that after cutting the board then term 9 or B8 should be strapped to +.
and it is as though the 47uF (c101) capacitor across the leads doesn't exist....

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Re: "Zephyr" - Finally, the "v4" Fechter/Goodrum/Hecker BMS.

Post by Zenid » Sep 29 2011 4:50pm

Gregb wrote:Still not terribly impressed with the instructions. In the Charge Control section Test It says use a current limited PS set to 100mA but no mention of initial voltage. It then says turn voltage up to 20V... From what ???.
From zero would be a safe guess...

I didn't have any fancy equipment, so I used his alternative approach of simply running a power supply to it in series through a 100W bulb. That protects the board in case there are any shorts. You can test both the shunt circuits and the main control circuit that way. If you look earlier on in the thread, you can see where I'm running through the tests and double-checking with Richard (Fechter) if I'm doing it right, what to expect and what to do next.

I will get round to writing this up at some point, but I've been busy with other things. If you don't have bench power supply equipment, just run a charger through a 100W light-bulb. Use a little screw-in light-bulb holder, and run the positive through the bulb and use the wire that comes out of it as your "protected" power source to attach to the positive of the board, to check that the main LED lights and that shorting the EOC pins turns the LED red. If something is badly wrong with the board then the bulb will light up brightly.
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Re: "Zephyr" - Finally, the "v4" Fechter/Goodrum/Hecker BMS.

Post by Gregb » Sep 30 2011 2:46am

Yes I have been collating all your chats about testing. It is just that the tests and instructions seem to be written for advanced users and not people like yourself, new to the game. The charging or discharging of the 47uF could be confusing to people trying to measure/compare the chan leads. And the other things I have listed should have been included by now. There is serious money involved in building this. Also many bench supplies don't like being started at zero. I have written quite a few instructions for techs over the years and these are not among the best I have read. There doesn't seem to be a consolidated list of corrections yet or the differences of the various marks of boards. Especially the addition of the switching diode. And Gary's web page is still down. I have been caught up with a lot of other things recently including making a bench PS so have put it aside for the time being and just read the thread when I can. Don't get me wrong I think they have done a good job, but when you charge money for things, you have to keep it up to date.

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Re: "Zephyr" - Finally, the "v4" Fechter/Goodrum/Hecker BMS.

Post by GGoodrum » Sep 30 2011 12:15pm

I agree, the test instructions could be better, but I must say, this was never intended to be a project for "first-timers", so to speak. Nonetheless, the whole point of this thread is to provide help for those who are putting one of these together. The big problem with this is that although this board will work with a very wide variety of configurations and charging setups, each one of these might operate a bit differently, in terms of how the circuits operate. It makes it hard to have a "complete" set of testing instructions, covering all possible cases.

In the next version of this, which Richard and I are working on right now, we are using a new control scheme that should work the same way with virtually every setup. The end-of-charge detection logic will work the same way, for all setups, and there's no "adjustments" required. The circuit is simpler, with fewer parts, because we were able to eliminate the current measuring portion of the circuit. Anyway, this should help simplify the testing instructions for these new variants.
Gregb wrote:when you charge money for things, you have to keep it up to date
You make it sound like we are making money off of this stuff. :lol: The "profit" from these boards is about $5. Even if the margin was $100 a board, I'd have to sell literally hundreds of these in order to come close to making up what I've spent on test boards and unsold older versions. :roll: Also, the website is still down because I have been concentrating on these new versions, plus the related "Lite" variants, and haven't had time to build a new website.

Anyway, if you have a problem with a setup, post as much detail as possible here, and we'll all try and figure out what is going on.

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Re: "Zephyr" - Finally, the "v4" Fechter/Goodrum/Hecker BMS.

Post by fechter » Sep 30 2011 1:18pm

Quite right, I agree the instructions are not very good.
If you have any problems figuring out the testing procedure, you can ask here or pm me.
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Re: "Zephyr" - Finally, the "v4" Fechter/Goodrum/Hecker BMS.

Post by Gregb » Sep 30 2011 6:53pm

Sorry Gary was not inferring you were making money or or being duplicitous. apologies if it came out that way. Some time ago I sent fechter a reference to a SM technology lifepo charger from Microchip. I have been busy lately on volunteer things for handicapped people and haven't been able to give it any time, but have you considered changing your philosophy slightly? Give away the shunt method, but keeping your control panel use it to switch on individual channel chargers when one channel hits full on bulk charging which would then be turned off. If they built a version on a more useful package size I would have tried it myself. You have hinted that SM technology is available to you. I bought one of their test boards and it performed well with accurate cut off voltages etc but I don't have the tools to mount them. The chips are very very cheap and the specs are pretty impressive.

regards
and apologies if necessary

Greg

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Re: "Zephyr" - Finally, the "v4" Fechter/Goodrum/Hecker BMS.

Post by fechter » Oct 01 2011 12:06pm

Yes, I've looked at dozens of chips and so far the best ones I've seen are the Seiko ones. It's still on the drawing board, but we want to get a solid through hole version first. I'm not so good at hand building with those microscopically small smd components. The capacitor coupled balancing scheme still has potential too, but will take a lot of time/money to get built and tested. This would avoid the need for shunts and all that wasted heat.
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Re: "Zephyr" - Finally, the "v4" Fechter/Goodrum/Hecker BMS.

Post by Zenid » Oct 01 2011 12:53pm

Yeah. Goodrum & Fechter are spending too much time on luxury cruises, and lounging around in gold-plated swimming pools off of all the money they made... :lol:

Come on guys! We want one of these right away:

Image

Seriously though I will eventually get round to doing a test section on my site, complete with the usual pretty illustrations and photos. I'm just a little swamped right now...
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