Johny's Electric Vogue

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Post by Johny » Mon, 25 Jul 2011, 16:20

Not wanting to double up on the posts that would be required to maintain the Vogue blog and a thread here, I don't want to post details of the Vogue's progress in this thread. However, I do want a member's machines entry so that I can get feedback and indicate progress since the blog doesn't appear to elicit many comments.

Anyway - the first small drive happened yesterday afternoon.
Click my signature for the blog.

I'll try to post a video with better quality later - I was a bit impatient to post it so I didn't fiddle much with output settings once I found I couldn't post a 150Mb version.

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Post by woody » Mon, 25 Jul 2011, 20:00

Awesome! Great work Johny! Good to hear family support/disbelief :-)
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Post by Johny » Mon, 25 Jul 2011, 20:06

Thanks woody. Torque control was also useful to tighten up the motor coupler 10mm bolt. Bad me Image I hope it untightens as easily because the motor coupler and drive shaft bolts don't line up. The coupler has bolts at even spacing around the PCD whereas the drive shaft is like most universals and has them as a rectangle - so I only used 2 bolts at the front. I didn't blog this because the guys who did the drive shaft AND coupler read the blog and I don't want to upset them.

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Post by marty11 » Mon, 25 Jul 2011, 23:58

Image Well done Johny ! I have been reading your blog for ages, and love the restoration bits you have done. .great work! Have notified a friend in SA who has a Minx..not a minxmaster! He says well done too.. paintwork, bumpers etc.. cant wait to see it with the lights ., boot lid, windows in, rego's and driving around.. bet you are keen as mustard now too.. Come on Woody. .catch up to Johny

Cheers.. Marty
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Post by weber » Tue, 26 Jul 2011, 00:07

Congratulations Johny! Great audio on your video.
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Post by Johny » Tue, 26 Jul 2011, 16:20

Thanks guys. The Vogue "trip" and my time on this forum are very closely aligned.

Yes weber, my kids appear not to be phased by a video camera running. My 12 year old son took the video which is why you only hear him.
At the time it felt like an anti-climax but then Laurel pointed out that I would be dissapointed now that I can't drive it around when it is electrically ready to go. BTW the torque control was smooth as silk and I didn't notice the 10% missing accelerator control at the start of it's travel at all. I think I'll up it to 15% for more control over regen.

There is still a lot of work to do but with each bodywork item done it gets easier/safer/legaler(word?) to drive on the road.

The drive was forward and reverse up and down the road about 5 times - you guys would have laughed at the number of times I went for a non-existant gearstick.

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Post by Johny » Fri, 29 Jul 2011, 19:22

I uploaded a better quality version of the same video (on the blog) to Youtube this morning. It's on the blog. Here is a link.
http://www.youtube.com/watch?v=3wkT2k5j8pU&

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Post by Johny » Wed, 15 Aug 2012, 17:44

If you check the Vogue blog you will see that we did a second test drive with the car almost finished. I didn't show the outside video due the a prominent number plate - should I - what's the issue - why do people hide them? Anyway....

Ok guys now I have a problem where I could use some input.
Before the second drive I fully charged the packs - I thought!
My packs are Headway 38120 10AH cells arranged 2P16S - so 20AH 50V packs. 32 cells per pack. 12 packs - 384 cells. 600V at 20AH.

Each pack has its own charger.
The chargers are 58.3V, 3A. I have wound them up to 59.1V and have two 3A diodes in parallel that are in series with the charger. They drop 0.8V at 3A and .75V at 1A.

On the test drive, I got a BMS alert out of 5 of the 12 packs.
The 7 good ones all measured 52.5 VDC +/- .2 V.
The alerting ones measured anywhere from 50.0 to 51.5 VDC.
All measurements done after arriving home at no load.

The alert was persistant (BMS reporting one or more cells under 2.0V) even efter powering down then up so it wasn't my old nemesis the motor EMF getting into a BMS or two.

After measuring all packs and checking the BMS fault indicators on the packs (my blue LED), I put the whole thing on change and left it overnight. Next morning all the packs had reached full charge and were no longer cycling the chargers off and on. My chargers are 3A. The chargers begun cycling after about an hour - so 3AH. (During the drive we had used 1.5AH).

Short system explanation here. The headway BMS system just turns the path from the charger to the pack OFF when any cell goes over 3.8V. When the cell recovers to about 3.75 the charger path (big FETs) is turned back on. he result is that all cells get a belt of 3A but the overvoltage ones are shunted with 180mA. The low voltage cells should end up charged. The charger is CC 3A, CV 58.3V.
Cell balance is 22 Ohm resistor shunts that appear to switch in at 3.7 V.

I pulled the worst pack out of the car (4 are easy to get at, the fifth is a 2 hour job), lifted the lid and measured the 16 cells pair voltages.
Image
I'm going to refer to cell-pairs as cells from here on.
Four cells were under 3.3 volts, most of the rest were 3.6 or over.
Cells 2, 4, 8 and 15 were of interest.
I arranged a 5V, 5A power supply with a diode or two that I could link in and out, and a big variable reostat (really) and pumped 4A into cell #2 for 3 hours - it got to 3.5V. So these cells aren't charged.

At that point I realised that I could not do this with every pack so decided to put the other 11 packs on "float" charge - meaning just switch the charging back on and let the balance system do it's job.

Over the next 48 hours I did the single cell charge thing to my open pack. Finally I connected the charge to this pack and was horrified to see cell #3 - not excessively high to begin with, was at 4.0 volts.

I panicked and disaambled the pack to the point where I could get the BMS out and checked wiring etc. I also traced back cell #3s wire to the connector on the BMS and then the shunt resistor and it was HOT - good.
By this time the cells was down to 3.85V and still dropping. Weird.

My only conclusion is that pumping 4A into cell #2 somehow caused cell #3 to overcharge??? I did NOT have the 58V charger connected when doing the single cell charge - but I also did not disconnect the cell connections to the rest of the pack.

I have tried and tried in the past to get a schematic from Headway for the BMS (which they don't make). I can't - it's annoying because I have had to reverse engineer it to do the opto pack modifications a couple of years ago now but I still don't know the nechanism that cause the above phenomenon.

The problem with just using the existing charge system to "balance" the pack. Is that the measured current when the pack is around 58V is only 50 to 70mA. It will take 16 days to charge/balance. During this time, "good" cells will be at 3.7 to 3.75V. These are measured values from the pack I opened and am playing with.

I have a 180mA constant current source and am about to wind a spare charger up to 60V and do a constant current balance. I did this about 1.5 years ago when the packs were in storage at work. At that time I didn;t open the packs but charged them CC at 180mA until they reached 58.3 volts.

Comments, ideas, dire warnings. I really can't sort out the rest of the drive system in the car (regen, thump) until I balance these packs because I figure if I draw current out of them now I might make the situation worse when I charge them again.

Sorry for the length of this post but I tried to get all the facts down in one hit.




Last edited by Johny on Wed, 15 Aug 2012, 07:49, edited 1 time in total.

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Post by Johny » Wed, 15 Aug 2012, 18:06

5V, 4A single cell system. The long stainless steel rod with heatshrink lets me get at the plate on the bottom of the cell pairs without having to take the bottom of the case off.

Image

Closer view. The white pole is a plastic ruler pretending to be a bonnet holder-upper (what's that called?).
Image

Panic sets in and I remove the lid so I can withdraw the BMS. This is just after I poked it all back in again. I'm over working on live packs.
Image
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Post by Johny » Wed, 15 Aug 2012, 18:09

BTW. For anyone using Headways cells. The three spares are still sitting at 3.31V. I blame all this on the Headway BMS and long storage. I think it's fixable without to much trauma though.
Also - no rust. The non-shiny plates are because I smeared them all with Lithium grease when I modified the packs. The undersides are NOT well smeared though - and no rust - anywhere. They have been in the cold, damp garage for two winters now.
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Post by woody » Wed, 15 Aug 2012, 18:45

The headway BMS in Dad's ebike let/caused some of his cells to get to zero. Up to this point I thought it was neglect, but I'm starting to think crappy design/execution.
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Post by Johny » Wed, 15 Aug 2012, 18:47

They have had a checkered history with BMSs. These ones don't seem to drain the cells but there is certainly some anomoly that stops them being 100% effective. I think once the packs are in reasonable balance I'll be OK. They were perfect 2.5 years ago. Image
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Post by coulomb » Wed, 15 Aug 2012, 19:30

Johny wrote: I think once the packs are in reasonable balance I'll be OK. They were perfect 2.5 years ago. Image

Yes, I think that's what's going on. Something weird has happened to unbalance the pack while in storage, and you need to re-balance it. With the only 168 mA bypass (at 3.7 V), it is going to take quite some time for the pack to re-balance. So I'd give it a week or so on charge; it might be good to set the chargers to a low current limit, if that's possible, just so things don't get too hectic. It sounds like you can't be too sure of the BMS coping with cell over-voltage, at least till you have more time to observe it. At least if the charge current is say 150 mA, then there should not be any cells going to 4.0 V or higher.

[ Edit: charger -> chargers ]
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Post by Johny » Wed, 15 Aug 2012, 19:35

Thanks coulomb. I think I'd better make a few more CC units - I only ever did one as an experiment. It allowed fully charger current then, when the current dropped below 300mA (the BMS turning the charger off), it switched to CC at 180mA. I was going to build 12 but decided I didn't need them - WRONG! I've snipped out the resistor that allowed the full charger current so now it's just a CC.
Anyway - I agree - thanks for the reality check.

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Post by PlanB » Wed, 15 Aug 2012, 22:58

Can't contribute much to the battery debate but love the video. "John can you control the speed?" is clearly spouse speak, translation "don't run over the kids". Inspiring stuff, I'm envious.

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Post by Johny » Wed, 15 Aug 2012, 23:07

Thanks. I did ponder at the time that they were standing in front of a car that I had only the day before placed a whole untested configuration in the controller and had only ensured that the motor didn't spin when the accelerator wasn't pressed - that's all. The Drive/Neutral/Reverse switch has diode ORs back to the absolute guaranteed controller enable and what you don't see is my hand loitering close to it. It also explains the "it's going forward - good" or similar that I said.

I have been green with envy so many times in the past 3 years reading about exploits on this forum - I know exactly what you mean.

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Post by Johny » Thu, 16 Aug 2012, 15:55

The constant current charge set to a couple of mA less than the rudman shunt bypass current has worked very well. I set a charger to 60V so the CC would be guaranteed to operate. After the overnight balance charge at 180mA, the opened pack has 14 cells at 3.68 to 3.69V, one at 3.33 and one at 3.37. The cell I bulk charged is one of the ones at 3.69.

That means the shunts kick in at 3.68-3.69V which is exactly what the BMS limited doco says. That in turn means that my chargers should put out 3.68 * 16 = 58.88. I have them set to 59.1 minus 0.75 diode drop = 58.35 (they came set to 58.3).
Thats how you can have a couple of cells out of balance. Fourteen at 3.69 is 51.66. 58.35-51.66 = 6.69. Divide among two cells is 3.345 - not enough.

[Ponder]
With a computer controled balancing system that can measure every cell, a good way to go would be, once you know that you have reached nominal voltage - or a cell has gone too high during charge.
1. Cut the charge rate back to your bypass value.
2. Measure the pack voltage - divide by cells - shunt any cell over the average.
3. Iterate to step 2 and stop when all cells are within some parameter = say 30mV.[/Ponder]

The simple system of cell bypass at a given absolute voltage is too dependent on the accuracy of the end voltage of the charger.

BTW For Headway 38120 cells at 180mA charge rate I found that when a cell gets to around 3.4V it's not far - less than 1AH (for 20AH cell pairs) away from full charge. Voltage of 3.2V is a very low charge, and 3.3xV has a few AH - even as low as half charged.

Conclusion. I don't have to pull that packs out of the car. I can balance my remaining packs with my 60V and 180mA CC system. I just look for pack voltage going to 3.68 * 16 = 58.9 and that's when I stop.
Once I finish getting ready for the final inspection I'll pull the chargers as I get time and re-adjust them to 59.65V -0/+0.15 ((3.68125*16)+0.75). The charge voltage setting is clearly critical with this type of balancing.

Edit: Changed 3.89 to 3.69 - thanks weber. Also divide, not device...and other typos.
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Post by BigMouse » Thu, 16 Aug 2012, 16:22

Johny wrote:[Ponder]
With a conputer controled balancing system that can measure every cell, a good way to go would be, once you know that you have reached nominal voltage - or a cell has gone too high during charge.
1. Cut the charge rate back to your bypass value.
2. Measure the pack voltage - divide by cells - shunt any cell over the average.
3. Iterate to step 2 and stop when all cells are within some parameter = say 30mV.[/Ponder]
That's pretty much what I have my BMS doing on my A123 "test" pack. Controlling an Elcon through CAN. I have programmed a 3-stage process. Stage 1 is the full 5.5A CC. Stage 2 ramps down linearly from 5.5A to 200mA between 3.56-3.58V on the highest cell. Stage 3 maintains CC at 200mA until the lowest cell reaches (and stays at, for a certain number of samples) 3.60V, at which point the charger turns off.

The voltage on the charger is set to well above the fully charged pack voltage, so as far as it's concerned, it's always CC at some set current value. The CV part of the charge is handled at cell-level by the individual BMS bypass.

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Post by Johny » Thu, 16 Aug 2012, 16:33

BigMouse wrote:The voltage on the charger is set to well above the fully charged pack voltage, so as far as it's concerned, it's always CC at some set current value. The CV part of the charge is handled at cell-level by the individual BMS bypass.
Nice. That's a good system.

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Post by Nevilleh » Thu, 16 Aug 2012, 16:53

Yes, that's what mine does too. It was handy knowing the charger manufacturer who obligingly fitted an input that drops the current down to 1/2A (my bypass value) when I asked him!
Fitting it to A123 cells would require a bit of a mission though - as you may recall the cell modules are designed to be bolted to the terminals of 40 AH prismatic cells.

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Post by Johny » Thu, 16 Aug 2012, 17:02

As some may know, I drive a 1967 Humber Super Snipe as a daily at the moment. It has CD175 pre 1969 carbies on it that don't have an individual idle mixture adjustment. The cabies aren't in bad nick but to have the car tuned for ideal mixture at throttle wide open (for towing), the idle is less than ideal - it shakes around a bit. (One day I'll find someone honest in Melbourne [not a Jag service place - past history] that can fix this issue - I don't appear to be able - or perhaps not motivated enough).

Anyway...that's why in the video we get to a stop sign and I say "I thought it had stalled". I'm just not used to my old cars idling so well. Image

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Post by Johny » Thu, 16 Aug 2012, 17:05

Humber Super Snipe (Series VA, 1967) at Parkes in 2006. You can see the dish in the background.
Image
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Post by BigMouse » Fri, 17 Aug 2012, 04:02

Love that photo! The old car makes it look like it could have been taken many years ago.

Nevilleh, pics of how I installed my BMS on A123 is in my thread in the battery forum: viewtopic.php?title=small-battery-pack- ... ing&t=2775

The BMS modules themselves are small square boards that mount on to cell "adapters" which are unique to whatever style of cell they're being installed on. The ones on my 18650 pack take two BMS modules and the adapters mount across two cells in series (4 in parallel, but could support more).

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Post by Johny » Tue, 21 Aug 2012, 17:34

I have been following the discussion on barnards-toyota-mr2-now-mr240 with interest, meanwhile battling with my packs in order to balance them.

The facts are that some cell pairs in my packs took 17AH (each cell pair is 20AH) to reach 3.65V while most cell pairs (generally 14 out of 16) were already above 3.6V from the standard charge.

I have tried two approaches:
1. Charge packs at a controlled constant current of 180mA (the bypass capability of the cell shunts).
2. Individuall charge cell pairs to bring them up.

While number 2 is obviously the best way, the CC at 180mA is WAY easier do due to the number of cells in this system.

So, does holding a cell at 3.69V (the rudman switch-in voltage) for 4 days (worst case*) damage the cells?
* normally about 20 hours and when packs are finally balanced maybe only one or two hours.

From what I have read, the Headway BMS approach of balancing by turning the path to the charger on and off (off when any cell goes above 3.8?V) does impact on cell life - how much? - don't know. Cells that have already reached full charge are being cycled from 3.85 to 3.7V continuously (over minutes) just to charge the recalcitrant (thanks Terry for that word - it fits perfectly) cells.

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Post by weber » Tue, 21 Aug 2012, 18:53

I'll put it this way: If they were my batteries, I'd do the 180 mA for (up to) 4 days. Unless they were really easy to access, in which case, at the same time as the 180 mA (sub-bypass) overall charge was going on, I'd go around clipping a 5 amp lab supply, as a single cell charger, onto the lowest ones for a few minutes at a time, to get it over-with sooner.

I dunno about "recalcitrant". Being the bleeding heart lefty that I am, I'd prefer to say they were "disadvantaged" or "underprivileged". Image

They can't help it if they were born with a higher self-discharge than everybody else, or if their BMUs have higher current than everyone else's BMUs.

[Edit: Removed off-topic political rant at the suggestion of another poster whose opinion I respect.]
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