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

[fechter]

I'm sorry to hear that. I hope things will work out for both of you. I assume that this is mainly caused by the general declining home value in California, right?

Well, in my case, it's mainly due to having 3 kids in college at the same time combined with a very high cost of living in my area (Marin county, CA). If I survive working 3 jobs, I can probably get the kids through college.

[999zip999]

What you pay for gas in texas ? Bay area is the most expense for everything.

[SamTexas]

Well, in my case, it's mainly due to having 3 kids in college at the same time combined with a very high cost of living in my area (Marin county, CA). If I survive working 3 jobs, I can probably get the kids through college.

I understand what you're going through. My two kids just finished college, one in May 2011 and one in December 2011. Hang in there, things can only get better.

[Alan B]

Then they move back home and still need support.

[Tom_D]

" both of our wives have prohibited us from working on the project anymore after wasting so much time and money with little hope of recovering it."

350 + pages on this BMS topic, then ANOTHER 350+ pages on the same topic, then ANOTHER 40+ pages of "Finally" pages,
enough already ?

here's where to order:
http://www.tppacks.com/products.asp?cat=26

enough already ?

[Gregb]

Nobody is forcing you to read them.............do you have a compulsion????????

[gge5]

here's where to order:
http://www.tppacks.com/products.asp?cat=26

I was just going to place my order, but the TP Packs website is selling old printers, software, and movies from the mid 1990's?

[ohzee]

Yea from what I can tell this venture is not atm cost worthy and the guys are doing their real jobs.

Web page has not worked for some time.

[iconoclast]

@Fechter/Goodrum:

Are any of the latest Zephyr boards still available? If not, how much would it take to make a small production run worthwhile?

I understand they would be unsupported.

[fechter]

I hope to get a run of boards done at some point. I need to revise and check the most recent version very carefully before submitting a run, as mistakes are too costly. Once the layout is 'validated' with a successful test, a larger batch could be done. Right now, time availability is more of a limiting factor than money.

[IBScootn]

Maybe the thread name should be edited to " Zephyr BMS - Good Idea but Boards Are Not Available". The current title tends to imply that "finally" something is available when it isn't.

[dnmun]

not really. the 'finally' means they have gone through several iterations of optimizing the BMS design to meet all the increased expectations they developed as they learned more and more about how to design one. i actually think their design is right up there with the very best offered in the world, just no money in it for them when they have so much other work to do.

when you are young you have lotsa time and little knowledge. when you are old you have little time and lots more knowledge.

maybe you need a facebook type BMS where you can 'friend' it in order to make it valuable to you. others appreciate what they are doing for the elegance of the design and it's effectiveness.

you can build up one of the previous iterations too. if you post up a request on 'items wanted' for an old V2 board you could build that.

[chxs]

i have BMS v4.4 and i get problems with ... i can't get the fet activating by itself ... if i bypass it the charge cycle is fine and the led switch from orange to red at hvc ... but if i don't bypass the fets the charger don't detect anything !but i can read the voltage at the pole of charger and all cells is shunting well ... !! what is the problems .... what i have to check ??? tank you very much !!

[fechter]

i have BMS v4.4 and i get problems with ... i can't get the fet activating by itself ... if i bypass it the charge cycle is fine and the led switch from orange to red at hvc ... but if i don't bypass the fets the charger don't detect anything !but i can read the voltage at the pole of charger and all cells is shunting well ... !! what is the problems .... what i have to check ??? tank you very much !!

You can PM me. You would need to measure some points on the board to figure out what might be going on. I assume by 'bypass' you mean install the EOC disable jumper.
If the charge current is too low, it won't stay on. What is your charge current? Also, you could try turning VR1 all the way down and see if that works.

[TheWizard]

I hope to get a run of boards done at some point. I need to revise and check the most recent version very carefully before submitting a run, as mistakes are too costly. Once the layout is 'validated' with a successful test, a larger batch could be done. Right now, time availability is more of a limiting factor than money.

I found this little blurb today about using an inkjet printer to lay masks directly to copperclad board so you can etch your own prototype PCBs
http://www.instructables.com/id/Convert ... /?ALLSTEPS

the v4.5 BMS has a hell load of through-hole drillings that one would have to knock-out, but I still think a DIY PCB beats the cost and wait of a PCB service.
And you could make the pads extra wide on the prototype in case you need to add/cut/reroute things, so it can be like a breadboard.

some drilling and etching tips are here
http://www.mentby.com/Group/piclist/ee- ... board.html

I'm thinking the cost of retrofitting a salvaged printer is about the same or less than ordering a prototype batch of _anything_, and it gives the ability to make lots of validation boards. I have a bunch of little projects I want to make where high-power/frequency rules out breadboards and wirewrap so I'm going to try and build a printer.

I've seen the layout thats been posted of the v4.5 BMS but not the parts list. smaller shunts and resistor arrays are the major changes, right?

[fechter]

To make DIY boards like that, it would probably be much easier to use surface mount parts as much as possible to minimize the number of holes needed. Drilling tiny holes by hand would be pretty challenging.

[thedarlington]

well drillings nothing compared to soldering well all those tiny bits, what if we messaged some of those open source nano pc(smoke pack size) guys who does the boards for them? they already sell a $25 700mhz mini pc -raspberri and theres plans for a $15 1ghz one soon -rhombus, thats with CPU, RAM, and plug sockets usb, hdmi phones etc, i bet they wouldn't mind helping us out atleast with tips or maybe take us under the wing to get some prices from whoever makes their stuff, after nano scale mobos im sure these boards are cake

by the way, are you guys still integrating off the shelf stuff like Cell Logs? i found a nicer $10 copy that comes with a large external alarm module probably makes for a nicer trigger,
also an already boosted Battery Medic (like garys old one?) $12 50w & $17 150w, using a light bulb & circuit to bleed-balance, these 2 are pretty much 80% of the the brains & triggers aka the complex bug prone stuff, maybe they could even make for a lite BMS? good enough for now with a more plug and play approach vs extra soldering

http://www.ebay.com/itm/3-in-1-li-polym ... 836wt_1198
http://www.ebay.com/itm/BVM-8s-1-8-cell ... 1e6ed2992f

[andrew.box]

Found this thread and project way later than I should have, looks awesome. I could use one of these, the main drawback of DIY lipo packs is still battery management. I understand the predicament you're in - to finish development to the point of a polished product that can be sold at a profit, or even break-even, at a reasonable number of units, is tough if not impossible given the niche market of DIY electric bikes and small electric vehicles.

In the meantime, are there any plans to make up and sell some bare boards with a parts list and basic instructions for assembly/testing that people could populate and assemble at their own pace? Seems like the margin per unit could be MUCH higher, since labor would be significantly reduced. Maybe a good stop-gap way to recover some costs before proceeding with more development?

I agree that a plug-and-play solution in a nice, pretty case would be sweet, but I for one wouldn't' mind taking care of the connectors, case and details on my own if I had a good quality PCB generated from a well thought out circuit like this.

I'll be subscribing to the thread, this is neat stuff.

[Tommy L]

Nice work here!

Subscribed!

Tommy L sends.... \\m//

[mj2412]

Hello, i'm still trying to solder this BMS. Beause of bad experience i have little concerns about connecting the cell cables one by one to the battery. Is it possible to add a small fuse into the cell cables? I'm thinking about a small fuse to solder into the cables.

What kind of fuse could be used for this?

Thanks, Martin

[fechter]

Yes, I've used small 2A pico fuses that have legs on them. Another approach is to attach one wire at a time through a 6v or 12v light bulb. If the bulb does not glow, then connect directly and go to the next cell until they're all hooked up. If the bulb lights up, something is wrong.

[alternety]

I am just curious. I have followed this topic through I think two different threads, and found it very interesting and potentially useful. I have a battery powered tool using a 36V NiCad pack. I was looking at making a Lithium replacement in the long term using this device. As it turned out, the battery pack failed after something less that 10 charge/recharge cycles. So I am back at looking at this solution.

My question (as in just curious) is has anyone looked at doing this with microprocessors rather than assorted analog solutions. Microcode is much easier to update than an analog implementation. I would think a digital solution would have less probability of circuit layout changes and could reduce power dissipation in some areas by using switching power regulation. Just a thought. It could possibly reduce component count and make it easier to tune performance. A simple microprocessor may cost less that a power resistor. It would also allow a diagnostic code display vs lots of LEDs. With an LCD display, much more operational information could be available.

[heathyoung]

Yeah, there are microcontroller solutions out there, have a look for peter perkins BMS. The biggest problem with micros is noise, lockups and power consumption.

The Cell-Log was used as a BMS for a while by GGoodrum/Fletcher IIRC (I have the board images here somewhere).

Its not a bad idea, the problem is though the unbalanced consumption between the pins. This is solvable, I've done it with external modification, rather than modifying the internals of the unit (yuk). Everyone complains about the cell-log unbalancing their cells if used permanently - the answer - rail to rail opamps set up as voltage followers (ie unity gain). But I digress.

I did like the original design, use it for LVC, delta V and HVC (with a simple shunt reg) - it appeals to the geek factor, plus you can have an indicator of your cells health all the time.

[megacycle]

Unlike an ebike, were generally guys want to maximize charge on larger packs, i was lead to believe power tool lithium packs often dont have much in the bms, basic, so you can fast bulk charge and terminate below the max recommended voltages, so practically they are slightly undercharged.
Please correct me if Im wrong.

[circuit]

if you don't mind large connector on the battery pack, it can contain only an LVC circuit (for each cell). The balancing and OVC should be in the charger then.
If large connector with many contacts is not a solution, then a proper BMS must be integrated in the battery pack, doing LVC, OVC and balancing.

Anyway, some sort of 'advanced' electronics is needed in the pack.