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

[ejonesss]

since the link to tppacks does not work do you still have any boards in stock and how much?

[Gregb]

you might be better to send Gary a PM.....

[GGoodrum]

Sorry, I missed that. I'm going to try and make the website a priority this weekend, but in the meantime, you can send me a PM. If I were you, however, I'd wait for another week, or so. Monday I am turning in our latest version of the newer, easier to build Zephyr variant, which makes use of resistor arrays and quad opto chips that drastically reduces the build time.

This latest board will support up to 32-channels, in a single box. For sixteen channels, a 1.2" x 4.06" x 6.3" box is used, and for the full 32 channels, both boards go in the taller 2" version of the same box.

Functionally, this is the same as its been for a the last several versions, as we've been mainly tweaking the layouts. There's three opto lines, one standard one for LVC, and two for HVC, one set a bit higher than the first. The higher one is used as a failsafe, to catch any weak/errant cells that may reach the normal cutoff way before the rest of the cells. This will trigger the HVC cycling mode where the power will cycle between off and on about once a second, until the rest of the cells get closer. The other HVC opto output string is connected in series. This signal goes active when all the cell's bypass circuits are on, which means the cells are all full. This then causes the EOC logic to shut off the charge current and turn the main LED a solid green.

Stay tuned...

-- Gary

[ejonesss]

that's ok for now ggoodrum budget (i am recovering stuff lost or damaged by this year's floods on the east coast caused by a week of off and on rain and i am trying a couple other ideas using a pair of meanwell power supplies and 10 voltphreak chargers.

the temporary house i am in has a bad outlet that caused 2 soneil chargers to blow and take $300.

also will the failsafe mode eliminate the effect that seems to occur on the negative end of the pack where the end 4 cells seem to be slightly lower than the rest?

[Gregb]

"also will the failsafe mode eliminate the effect that seems to occur on the negative end of the pack where the end 4 cells seem to be slightly lower than the rest?"

Could you elaborate on this? Do they measure a lower voltage? and by how much ? and does this effect come in after standing for a while or are they cutting off early ?
None of mine are exactly the same particularly after an hour or so. and are you leaving something like the cell log across them ? It does consume power

[GGoodrum]

"also will the failsafe mode eliminate the effect that seems to occur on the negative end of the pack where the end 4 cells seem to be slightly lower than the rest?"

Could you elaborate on this? Do they measure a lower voltage? and by how much ? and does this effect come in after standing for a while or are they cutting off early ?
None of mine are exactly the same particularly after an hour or so. and are you leaving something like the cell log across them ? It does consume power

This was with the original v2.x boards, which had a tap for the 12V regulator off the top of the 4th cell. All of the v4.x variants have the regulator powered from the whole pack voltage.

-- Gary

[GGoodrum]

Here is the latest layout variant, that we just turned in to run:

Functionally, it is the same, but we've made some accommodations so that this one PCB can support 12s, 16s, 24s and 32s configurations. Also, I think we are a lot closer now to having a final variant. After Richard finishes testing this one, we should be good to go.

-- Gary

[SlyCayer]

Hey,

I bought the board very early around the 11th page of this thread, and I am wondering if the board I have is good enough to trust with A123 20Ah worth of 7000$...

I never had the time to put together after I ordered the board and the parts.

Is there anything that has changed significantly since I bought the parts and board? I will be putting it together soon and if you are telling me it it's no use to put it together due to problems with the original design then I won't lose time with it.

[fechter]

The addition of the diode described on the previous page is about the only major thing. There were a few mismarks on the actual board for the components, so when in doubt, check the schematic. The schematic is correct. I'll send you the updated schematic. The testing instructions suck. Zenid's version will help. Building this board is not a good project for a beginner or someone with limited electronics knowledge.

[gensem]

Gary,

Would I be able to use non standard cell numbers, like 26s, 28s and 30s in the 32s "BMS"?

[fechter]

Yes, any number of cells can be used. A single jumper would need to be installed for non-standard cell counts.

[SlyCayer]

Building this board is not a good project for a beginner or someone with limited electronics knowledge.

I have good knowledge(I think), I just got off the forum for a while because I moved house and had to renovate(not done yet)

Do you guys sell pre-built and tested boards?

[Bazaki]

I also didn't read every post in this very long topic and have the same question and I also wonder about the price.

[Spacey]

Would really help to have costs simply displayed etc and also how this BMS differs from the normal Chinese BMS etc

35 pages is a lot to wade through, I am interested in a 16 cell one but have no idea on price/build/info

[Alan B]

One technique to solve these problems is for the thread owner to edit the first post to contain a summary of the info. Folks coming to the thread get up to speed, more or less, in the first posting. When that post is updated a posting can be added to the thread to let folks following the thread know they might want to go reread the first post for the updates, or the updates can be summarized in the thread.

[Spacey]

I was a bit hasty in my previous post and am nursing one hell of a headache. Have just waded through a few pages and am interested, but would like to know how this BMS differs as in it's a shunt based ...differs from the normal bleeding BMS?

[GGoodrum]

Sorry for the delays.

I agree, we need a better way to get to the latest info. I will either edit the first post, or we'll start a new thread for the new version.

What is different about this new version, which we will call v4.5, is that it has a new/simpler control scheme for determining end-of-charge, and that we are now using resistor arrays and quad opto chips which cuts the assembly/build time down significantly. It used to take me several hours to bend the leads, install, solder and trim the leads for the hundreds of resistors on a typical 24-channel board. Now, using the resistor arrays, that time is cut down to about 20 minutes. Here's what a partially assembled board looks like:

16s Zephyr BMS-01.jpg (152.76 KiB) Viewed 950 times

There are two main differences between this Zephyr BMS design and the typical Ping/Signalab-type boards. The latter typically only have bypass currents of 50-75mA, which means it literally can take over 24 hours to balance a reasonably imbalanced pack. The Zephyr shunt circuits can pass about 600mA, or about 10 times as much bypass current. Even the new Zephyr "Lite" BMS variants, which we are also working on, primarily for embedded LiPo setups, can pass about 160mA of shunt current.

The second major difference between the Signalab, et al, and Zephyr designs is the way charge control is handled. In the typical designs, the HVC trip point is set pretty high, like around 3.70-3.80V for LiFePO4. As soon as a cell voltage hits this point, the charge current is cutoff and the shunt circuits then bleed current off until the high cells are back down until the cell voltage is below the turnon point for the shunt circuit, typically around 3.60-3.65V. At only 56-75mA, this can take hours. This is not the most efficient way to do this, but it will eventually work, as long as all the cell voltages are above the shunt turnon point once the charge current is cutoff. For healthy cells, that start out reasonably balanced, this works okay, but like I said, can take awhile. If, however, you have a weaker cell, with slightly less capacity, or some that for whatever reason are significantly out-of-balance in relation to the rest, you can end up where cells get full faster. When that happens, the voltages for those fuller cells will rise sooner than the rest, and will trip the HVC line too soon. Now you have a case where the bulk of the cells haven't reached the shunt bypass turnon point, so only the fuller cell shunt circuits will come on. This will bring the high cells down closer to the rest, but it does nothing to balance the rest of the cells. What needs to happen is that the whole charge cycle needs to be repeated until all the cell voltages will at least be above the shunt turnon point when the high cell trips the HVC line.

The new Zephyr control scheme works differently. There are actually two separate HVC lines, one set a bit higher than the first one. The higher, second HVC signal is used as a "failsafe" control, to catch those cases like the one described above, where a weak, or severely imbalanced cell gets full way before the rest of the cells. We don't want this errant cell to get into an unchecked voltage rise condition, so whenever this line gets tripped, the charge current will be turned off briefly, for about 1 second. During the off cycle, the shunt circuit will pull the cell voltage back down closer to the rest, and then the charge current is turned back on. This cycling will repeat until the rest of the cell voltages catch up to the point that the shunt circuits themselves can keep the high cells in check. With 500-600mA of shunt current, it takes a pretty out-of-whack cell to trip this "failsafe" HVC signal. Under normal conditions, with normal imbalances, this HVC cycling condition shouldn't occur. When it does, it is a good indication that something is amiss.

The other HVC signal is tripped for each cell circuit when its shunt is in full opration, which means this cell is full. The opto outputs for these HVC signals are connected in series, instead of in parallel, like with the "failsafe" HVC and the LVC lines, and then this series connected opto string is used to trip the end-of-charge cutoff logic. This is a much simpler, and more reliable way to do the cutoff logic. In the previous versions, we were measuring the charge current and waiting for it to drop down below some user-adjustable setting, and then cutting off the charge current. This scheme works, but each setup is different and we've seen numerous issues in various setups. The new scheme is pretty much "one-size-fits-all" and it doesn't require any user adjustments.

The Zephyr Lite variants are functionally equivalent, but with shunt currents low enough that the boards can be safely embedded with the LiPo packs. It has been my experience that LiPo-based setups stay much more closely balanced, under normal conditions, so less shunt current is fine. The charge control section is identical to what's on the full Zephyr board, but as shown in the example shown below, it is sized to fit in the smallest Hammond 1" x 2" x 3" extruded aluminum case:

4x6s Embedded BMS Lite-v4.4.10a.png

(156.61 KiB) Downloaded 3 times

I'm not too sure on the pricing, for either the full Zephyr unit, or for the Lite variants, but the overall costs should be less than the previous versions. The board sizes are smaller and the total parts count is down quite a bit. For the full Zephyr boards, we will at a minimum offer the PCBs with a detailed set of instructions and a BOM file. We may, however, also offer pre-built and tested versions, once we get these going. I don't know how much extra this will be until we get an idea on how long it now takes to build one. Richard is working on this now. For at least the LiPo Lite version shown above, we will definitely offer these pre-built/tested, at an attractive price. More about this later (please don't send me a PM requesting prices and availability yet. ).

We will also be starting "For Sale" threads in the for sale forum section, for each of these, and like I said, I will either update the first post in this thread, or we'll start a new "info" thread, with all the appropriate data in the first post.

-- Gary

[fechter]

It's not quite 'fully baked' yet, but it's close. I don't want to declare success until it passes all the validation testing. 4.5 takes uses the throttling and auto power scheme from 4.4 and throws in a modified version of the successful ver 2.x end-of-charge detection. This eliminates the need for adjustments on the board and maintains the reduced heat output feature of 4.4. It should be fairly tolerant of charger voltage variations and play nice with most chargers. LVC relay option allows for highly flexible LVC connections that will work with virtually all controllers and there is a provision for audible/visual alarm connections for those that don't want a throttle interrupt. The real breakthrough is the use of resistor arrays to cut down on the assembly time. Great idea Patrick It works fantastically with through-hole parts.

4.4 is still the big daddy in terms of shunt current. 4.5 is designed at 500mA but generally runs a bit higher. For very large cells or large imbalances, 4.4 will have a speed advantage.

[Spacey]

Sounds good, with the Lipo version would we be able to have the option to ...well...here is my Lipo charging setup:

I have 6 x 8S 5.8Ah Turnigy Lipo wired up for 16S 3P with the balance leads all wired up in parallel for simple balancing. I charge using a Kingpan standard 12A but adjusted to 63.4V so that my cells are kept at around 4.12 to 4.15v when bulk charging.

Can your Lipo Lite BMS be setup to not let cells go over say 4.14v to keep the cycles higher as a lot of people do not like having cells charged to 4.2v?


Doh! Further reading of the other thread says that you like to charge to 4.16v I think which is fine

[fechter]

Build still in progress:

Build pic 4.jpg (144.3 KiB) Viewed 908 times

Most other commercial circuits allow the high cells to go to a much higher voltage at end of charge and the charge terminates as soon as the first cell reaches this level. With the new versions, all the cells must reach the set point to terminate charge, so balance is forced on every cycle, yet none of the cells are allowed over the set point.

Another feature, also found on the 4.4, is my patented HVC delay function, which allows for throttling the charge current by switching the charge current on and off at a very low frequency (around 1Hz), yet maintains the fastest possible balancing for a given shunt current. This eliminates the screeching/blown charger problems some encountered with the high frequency ver 2.x board throttling system. If the cells are well matched, the throttling function will never kick in, but if there is a significant imbalance, it will correct the balance in the shortest possible time, then terminate the charge.

Another 4.4 feature carried over is the automatic power switch. Previous versions required either a manual start or a third wire and jumper on the charger connection to switch on the control circuit when the charger is connected. Now, anytime the charger voltage is greater than the pack voltage, the control circuit automatically comes on.

[GGoodrum]

Sounds good, with the Lipo version would we be able to have the option to ...well...here is my Lipo charging setup:

I have 6 x 8S 5.8Ah Turnigy Lipo wired up for 16S 3P with the balance leads all wired up in parallel for simple balancing. I charge using a Kingpan standard 12A but adjusted to 63.4V so that my cells are kept at around 4.12 to 4.15v when bulk charging.

Can your Lipo Lite BMS be setup to not let cells go over say 4.14v to keep the cycles higher as a lot of people do not like having cells charged to 4.2v?


Doh! Further reading of the other thread says that you like to charge to 4.16v I think which is fine

Yes, you can simply set the charge to voltage to about 4.15-4.16V per cell. It will balance all the cells to around 4.14V.

What is shown above is 4 x 6s boards, but we will also have 8s versions as well.

-- Gary

[krelle52]

4.4 is still the big daddy in terms of shunt current. 4.5 is designed at 500mA but generally runs a bit higher. For very large cells or large imbalances, 4.4 will have a speed advantage.

A semi-noob questions
What is considered to be a very large cell? I use LFP 12S 16 AH. Should I buy a v4.4 instead of a v4.5?

I am looking forward to the release of v4.5 and if it is not too much to hope for. A website which is not under construction . but seriously..great work and do not work yourself to death

/krelle52

[fechter]

A semi-noob questions
What is considered to be a very large cell? I use LFP 12S 16 AH. Should I buy a v4.4 instead of a v4.5?

I am looking forward to the release of v4.5 and if it is not too much to hope for. A website which is not under construction . but seriously..great work and do not work yourself to death

/krelle52

By large, I'm thinking 100Ahr car-sized cells. For 16Ahr, the 4.5 shunt levels should be fine.

[GGoodrum]

Here are some shots of the new Zephyr "Lite" embedded BMS 6s4p boards, along with the small separate Charge Controller unit:

These boards are not just simple LVC/HVC boards, like I've done in the past. These are full-blown BMS boards that add cell balancing, plus the same two-level HVC and LVC protection functions. As many of these 6s4p boards that are needed can can be daisy-chained together, to support multiple pack configurations. The two-wire LVC signal can be tied into the throttle signal or a controller's ebrake input. The two HVC signals are daisy-chained between board using comon RC servo cables, which are available in a large variety of lengths. There is a special adapter that the end unit servo cable plugs into that combines these signals with the main pack charge + and - connections. These also have spots for 4mm bullet plugs, so the main pack leads can be paralleled as well. I have two other versions of this adapter, with support for 4p 4mm bullets and a 2p setup for 5.5mm versions, found on some packs.

A single charge cable which has the main pack charge leads, as well as, the HVC signals, plugs into this adapter and can then be brought out to the outside of the pack. The new standalone charge controller has the mate for this plug coming out of one end of the small box. The only oher connections are then the two + and - charge connections that are connected to the charger/supply.

I'll have more info about this new "Lite" setup, including pricing and availability, in the coming days.

-- Gary

[dnmun]

where is our steve jobs giving the release presentation?

we should have bands playing and politicians with speeches.

this is a really proud moment for you guys, it has been a pleasure to try to just understand and appreciate how far you guys have come in just a few years.

congratulations of the highest order! you guys did a great job, and put up with a lot of questions, this has to be one of the biggest things on the sphere, congrats to both of you!