Hemonster's ACIM conversion

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Post by Tritium_James » Wed, 13 May 2009, 01:58

The economiser has a small buck converter (step-down DC/DC) that puts the full 12V across the relay coil to make it pull in, then after a second or so drops it down to a lower voltage (7 or 8V or so) to keep the coil held in. So your power consumption drops pretty significantly.

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Post by Nutz » Wed, 13 May 2009, 02:21

Hi Hemonster,
Did you get a price on those 48v batteries?
Weather you think you can, or you think you can't, you will usually end up being right.

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Post by a4x4kiwi » Wed, 13 May 2009, 02:31

or a device running switched mode like these Solenoid Drivers

you will need a resistor or preferably the drivers because the coils get VERY hot running off 13.8v.

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Post by Johny » Wed, 13 May 2009, 03:53

Industrial contactors generally use the NC (Normally Closed) auxiliary contacts with a resistor across them. The Joslyn Clark I bought had a resister value that placed 8V across a 24V coil once closed. That;s abit inefficient for our purposes.

I was planning on placing the break-up contactor coils in series (pairs) and using a 12 to 24V 5 Amp Switch mode to apply 24V to the pairs then have a Diode from 12V to the contactors. The 24 V supply would only run for a second or so.

hemonster - I was going to use Allbright miniature SW60-2 SPST from UK thetoolboxshop at 12 GBP (AU$24). They are rated 80 Amps cont.
Duty    Ampere Rating
30% 150 Amperes
40% 125 Amperes
50% 115 Amperes
60% 105 Amperes
70% 95 Amperes
They also pull in at 66% voltage and have 10-25% hold-in so 3 in series would be viable (jack the 24V up to 28 or so to make sure).

I am very interested in the contactors you are getting. Is the $8 with magnetic blowouts? When are you placing your order?

Edit: Corrected 60% to 66% pull-in voltage (for continuously rated types) and added link.
Last edited by Johny on Wed, 13 May 2009, 09:29, edited 1 time in total.

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Post by Hemonster » Thu, 14 May 2009, 02:19

Nutz wrote: Hi Hemonster,
Did you get a price on those 48v batteries?


Yes I did, the one in the white plastic case was USD$560 per pack with charger and BMS! ... that's the same price as the EVPST pack, except its twice the capacity. Hmm ... starting to look like a good deal as this pack can give me 80km range.

What do you guys think? 100A continuous rated, 11kgs each, 20AHr, what more could you want?

I'm getting the specifications for the charger and BMS through next week sometime.

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Post by Hemonster » Thu, 14 May 2009, 02:37

Johny wrote: I am very interested in the contactors you are getting. Is the $8 with magnetic blowouts? When are you placing your order?


I'm getting 16 of them direct from NanFeng (2 spare), but am yet to receive a proforma invoice from them, should be today I expect. They were going to advise postage to NZ, but if you are keen let me know in the next day or so - Hemonster at gmail. Each is about 1/2 kg.

There are two main contacts, one with M8 terminals NO and other with M5 NC. Both apparently rated for 100A. I've also asked for clarification if these can break 100A at 70V - though I'm going to use the Tyco Kilovacs for blowing a main fault currents.
Johny wrote: They also pull in at 66% voltage and have 10-25% hold-in so 3 in series would be viable (jack the 24V up to 28 or so to make sure).
Sorry a bit of a ignoramous and not up with the jargon. Pull-in at 66% voltage - is that at rated current? What is a 10-25% hold-in?

I was going to use the NC contact for the charger and the NO contacts for the traction. Nanfeng do have other relays but this appeared very cheap and simple - even comes with the repair kit for USD$3 if you want it, fully servicable. It wasn't worth it getting only a few for testing, so I'm getting the lot for testing Image

edit: from what I understand, only the the 48V coils have PM blowouts, but I've asked her for clarification.

edit again: actually she confirms that it does have PM blowouts, and note that the price is USD$10.26 for the SPDT, not USD$8 as I first thought which is the SPST.

Last edited by Hemonster on Thu, 14 May 2009, 16:02, edited 1 time in total.

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Post by Johny » Thu, 14 May 2009, 03:19

Pull-in at 66% voltage means that they are guaranteed to pull in (close) at 8 volts if rated for 12 volts. Hold in is similar - they will continue to stay closed at 25% of rated voltage (3 Volts).

What this means is that you could put 3 in series off 12 V - making 4 V per contactor, provided you applied at least 8V per contactor (24 V) to initially close them.

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Post by Hemonster » Thu, 14 May 2009, 13:28

Johny wrote: Pull-in at 66% voltage means that they are guaranteed to pull in (close) at 8 volts if rated for 12 volts. Hold in is similar - they will continue to stay closed at 25% of rated voltage (3 Volts).

What this means is that you could put 3 in series off 12 V - making 4 V per contactor, provided you applied at least 8V per contactor (24 V) to initially close them.


Ok, thanks for clearing that up for me Image

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Post by Johny » Fri, 15 May 2009, 15:53

Here is another Lithium battery from China.
This one is 60V20AH. I had checked on 60V lead-acid chargers from the same guy acmotor got his 48V chargers and I was going down the path of 10 x 60V (5 12V batteries per) packs.
This reduces (slightly) contactor-contact loss and the number of contactors required.

So I was pretty happy when this battery turned up in a search (they look amazingly like the headways).
60V20AH

Here is the response to my request for maximum and cont. current info.

Dear Mr John,
20Ah60V battery with 40 cells of 38120 cell battery, so the max current is 300A and the continuance current is 200A.
And if place the higher voltage it will damage the BMS.
Looking forward to your reply soon

Sincerely
Michelle


Then I asked about price.
Hello John,
for the battery 60V20Ah, the battery price is 600USD/p, including the pack case, and if you need 10. they are 6000USD.
every charger is 44USD, and 10 is 440USD.
Looking forward to your reply soon.

Michelle


Then I asked:
Hello Michelle
If these were purchased could I get circuits of the BMS so they can be modified.
The modification would be to remove the power MOSFET used to isolate the pack and replace it with opto-isolator which would shut the controller down within a few microseconds.
In this way could I then place 10 packs in series for a 600V system?
Regards
John

She answered.

hello John ,
the circuits of the BMS , i can send it to your on my working time,
and you can place 10 packs in series for a 600V system of course
Best regard

Michelle


So, if/when I get them I'll check how hard it would be to modify so series is possible/safe.

Edit: Typo
Last edited by Johny on Mon, 18 May 2009, 10:34, edited 1 time in total.

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Post by Hemonster » Fri, 15 May 2009, 18:58

Hey Johnny, that's very interesting thanks for posting. I wonder if they guys buy from Headway or claim to also be yet another manufacturer. One thing my boss saw at the last China fair was that there are lots of companies who use "public tooling" .... where a company designs a generic solution and 100s of "manufacturers" make the thing and pass it off as their own product. However lo and behold it all looks the same, and yet all of them claim to be manufacturers ... not sure if this is or is not a problem, but pays to bear it in mind.

I didn't think it extended to the battery cell level though ... it's also often hard to know if these guys are the actual manufacturer of some part of it (ie. BMS, Cells, casing, packing of cells), or just resellers of the product ... they won't tell you if they are anyway cuz everybody wants to be known as the manufacturer.

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Post by Johny » Fri, 15 May 2009, 19:56

Now if we could get at from US$1.5 down to the magic US$1.1.
I'm feeling a lot more optimistic about Lithium - these 2 packs really look like they were made for ACIM conversions.
If all goes roughly to plan my buying time is around Sept/Oct. That's when I make the decision. A REALLY good price would have me buying earlier and storing them (run out to garage every weekend and sit and watch them for a while) Image

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Post by Hemonster » Sat, 16 May 2009, 00:41

Geek alert!! Image

Don't worry, I'm not all that different ... I've been going to the garage and looking at my motor and occasionally turning the rotor, and each time I get positive vibes ... like a warm fuzzy, but much geekier Image

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Post by Johny » Sun, 17 May 2009, 14:48

I finally ended up finding the company's real home page and guess what? It's headway - same company, different door.

http://www.xhnykj.com/

Edit: Added url
Last edited by Johny on Sun, 17 May 2009, 04:49, edited 1 time in total.

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Post by coulomb » Sun, 17 May 2009, 14:59

From the first page:
Hemonster wrote:Another thing I thought was using a DPDT (or DPST) for each of the chargers' two terminals, the coils get energised by the charger voltage itself (via some voltage reduction). These only need to be 60V 8-10A rated and should be relatively cheap?
I was just thinking that you might not need these relays for the chargers at all, depending on the chargers' output circuits.
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Post by Johny » Sun, 17 May 2009, 15:27

I am relying on the chargers being able to be left connected permanently to the batteries. If they discharge the batteries too much, one of 2 other alternatives.
1. A schottky diode to prevent the charger discharging the batteries.
or if the charger can not cope with the diode voltage drop.
2. Suitably small relays (rated for charger current) to isolate the chargers from the batteries. Relay coils energized when car on charge.

The chargers really must have floating outputs. I would think that most do (or can be modified).

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Post by weber » Sun, 17 May 2009, 17:26

Talking about charger isolation ...

When using an industrial VF drive -- capable of regenerative charging -- it makes no sense to me to use a separate charger at all. Particularly when you pay so much for the VF drive compared to DC drives (controllers).

This means non-isolated charging and so protection against shock must be provided by other means.

We plan to do our best to make our VF drive do both 3-phase 415 V and single-phase 240 V charging. But this will require a drive that provides the ability to write our own software control loops. We are considering the Control Techniques Unidrive (SP) series, with their optional Applications-Lite programming module (a second microprocessor).

The basic idea for 3-phase charging is that you either
(a) use a 3PDT contactor to disconnect the motor and connect the mains in its place via a 3-phase high frequency inductor,
or
(b) use the motor as that inductor by using a 3PDT contactor to separate the motor into 3 separate windings in series with the mains.

For single phase, the idea is to connect the motor in star configuration and connect the neutral to the star point and the active to one phase. The motor then acts as a "rotary phase converter" producing the other two phases. Then it works like (b) above. The VF drive will need to spin the motor up to speed (using battery) before connecting the single phase mains.

We will use the existing gearbox neutral switch and handbrake switch to prevent this operating unless in neutral with handbrake on. Obviously this is something you can't do with direct drive.

Back to the lack of isolation. This means that when connected to the mains, the vehicle chassis-earth must be connected to mains-earth and there must be a type-B RCD (one that trips on both AC and DC imbalances of 30 mA or more) between the mains and the vehicle. This must be mounted in the vehicle so you have it no matter where you are charging.

Since chassis-earth must be at the same potential as mains-earth and hence mains-neutral, we can't earth the centre of the battery while charging by these methods. Although battery centre is nearly the same as the VF drive's virtual neutral, it isn't exactly the same. The difference is the third harmonic "neutral wobble" that allows 415 V 3 phase to be obtained from a DC bus that is only sqrt(2) * 415 V instead of 2 * sqrt(2) * 240 V.

So either
(a) one has the battery always floating and disables the insulation monitor alarm while charging (Note that protection from shocks between battery and any of chassis or mains-earthed items or wet ground is then provided by the type-B RCD),
or
(b) one has the battery centre normally chassis-earthed via a type-B RCD and disconnects this chasisis-earth while charging.
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Post by Hemonster » Mon, 18 May 2009, 00:07

Johny wrote: I finally ended up finding the company's real home page and guess what? It's headway - same company, different door.


Ahh, I'm pleased about that. There are so many battery makers out there, its nice to know that we are dealing with the ONE company ... Image

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Post by Hemonster » Mon, 18 May 2009, 00:23

weber wrote:
We plan to do our best to make our VF drive do both 3-phase 415 V and single-phase 240 V charging. But this will require a drive that provides the ability to write our own software control loops. We are considering the Control Techniques Unidrive (SP) series, with their optional Applications-Lite programming module (a second microprocessor).
I'm an embedded software engineer myself and this sounds complicated Weber, ... perhaps you have enough experience down the power side of things to do this, but I'm more comfortable just buying something that will work. And honestly, the multi charger system really isn't all that expensive, comparatively speaking - pricing or weight.
weber wrote:
Back to the lack of isolation. This means that when connected to the mains, the vehicle chassis-earth must be connected to mains-earth and there must be a type-B RCD (one that trips on both AC and DC imbalances of 30 mA or more) between the mains and the vehicle. This must be mounted in the vehicle so you have it no matter where you are charging.
I guess you can also use an isolating transformer where the mains comes into the car, then you can keep you existing hard connect to middle pack.


I've throughly gone off the idea of a hard ground connect to middle pack because I see more disadvantages than advantages. For one you don't get a warning with a hard connect, the first strike to body will trip the system. You thus lose safety in loss of redundancy. Having two high impedance (via two 100-500K ohm) connections to battery + and - and monitoring the voltage drop across these would be much better. Also to note that I was told that these have to be switched in to prevent corroding of the contacts (if you are not breaking up your pack) from parasitic currents.

I'll use two connections so I can tell if there is a short at all locations (unless I get two identical shorts across each of the two high impedance resistors - in which case the main fuse "should" blow). If I take a closer look at the current differential, I should also be able to ratiometrically tell where the fault is likely to be in the battery pack. If the fault is in the traction circuit, this can be isolated by placing this sensing circuit before the main contactors. I'm planning on combining this functionality with the precharge circuit.



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Post by Hemonster » Mon, 18 May 2009, 01:18

Johny wrote:
And if place the higher voltage it will damage the BMS.
What was this answer in relation to? Regen braking?




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Post by weber » Mon, 18 May 2009, 01:44

Hemonster wrote: I'm an embedded software engineer myself and this sounds complicated Weber, ... perhaps you have enough experience down the power side of things to do this, but I'm more comfortable just buying something that will work.

Yes. It is complicated and despite the fact that coulomb and I have both spent a significant part of our careers straddling the computer software/hardware boundary, we wouldn't be attempting it without the assistance of Ross Pink, an electrical engineer with lots of theoretical knowledge and experience of automatic control in high power industrial situations.

And of course, when we've done it once, it costs almost nothing to copy the software. We are open-source kinda guys.
And honestly, the multi charger system really isn't all that expensive, comparatively speaking - pricing or weight.
Would you take this with you so you can charge anywhere there's 240 V? We couldn't fit anything else in the MX-5 without losing the already tiny boot.

In theory, we can do a 1 hour charge anywhere if provided with a 50 amp 3-phase outlet, just using the existing VF drive.

But of course it's more like a 10 hour charge when using a 240 V 10 A outlet.
I guess you can also use an isolating transformer where the mains comes into the car, then you can keep you existing hard connect to middle pack.
Not really. The amount of copper in a 50 Hz transformer of sufficient power would probably make it cost more than a switchmode charger and we certainly couldn't take it with us.
I've throughly gone off the idea of a hard ground connect to middle pack because I see more disadvantages than advantages. For one you don't get a warning with a hard connect, the first strike to body will trip the system. You thus lose safety in loss of redundancy.
I have to agree with you here. We plan to have floating pack too.
Having two high impedance (via two 100-500K ohm) connections to battery + and - and monitoring the voltage drop across these would be much better.
I assume you're aware that just measuring a static setup like this will not detect insulation failure from mid pack to chassis.
Also to note that I was told that these have to be switched in to prevent corroding of the contacts (if you are not breaking up your pack) from parasitic currents.
Sounds interesting. Not sure I understand what you're saying here. Please explain further.
I'll use two connections so I can tell if there is a short at all locations (unless I get two identical shorts across each of the two high impedance resistors - in which case the main fuse "should" blow).
It could be lethal insulation failure caused by water bridging across. This would not blow a fuse. And won't a single short from mid pack have the same effect, as mentioned above.
If I take a closer look at the current differential, I should also be able to ratiometrically tell where the fault is likely to be in the battery pack. If the fault is in the traction circuit, this can be isolated by placing this sensing circuit before the main contactors. I'm planning on combining this functionality with the precharge circuit

I think we'll use one of those Bender insulation monitors.
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Post by Johny » Mon, 18 May 2009, 15:49

Hemonster wrote:
Johny wrote:
And if place the higher voltage it will damage the BMS.
What was this answer in relation to? Regen braking?
What she meant was that if the BMS was to attempt to disconnect the pack due to a cell going under-voltage (maybe over as well), then the BMS would be damaged.

The BMS system usually uses a power MOSFET to disconnect the pack if the BMS deems conditions to be fatal to any cells in the pack. The MOSFET would have a voltage rating. The lower the voltage rating, the cheaper the MOSFET - so it's voltage rating would be only sufficient to safely cope with the pack voltage - not usually more.

Now imagine 10 of these packs wired in series with something drawing 100 Amps from the whole string. Suddenly one pack's BMS switches its MOSFET to OFF and the remaining packs apply 540 Volts across the pack that has just gone "open" - with 100 Amps current capability. The MOSFET dies due to massive over-voltage - and if luck with with us it goes open, but most likely it just shorts out and we may never know (depending on monitoring systems)!

So that's why I asked. This gets a bit complex because the chargers may rely on the BMS cut-out as well. If the chargers are only 3 or 4 Amps this is unlikely.

A modification to the BMSs would be to replace the MOSFETs with opto-couplers to a common bus (10 of them in the 60V pack scenario) that "trips" the VFD. This would work for under or over-voltage (as long as the BMS was looking for it) and therefore would work for acceleration and regen. braking.

Seeing the BMS circuit will help in deciding if this is viable.
I'm sure that something is possible - even without circuits it won't be hard to identify the switching device and hack it a little...

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Post by Hemonster » Mon, 18 May 2009, 17:43

weber wrote:
And of course, when we've done it once, it costs almost nothing to copy the software. We are open-source kinda guys.
Well, kudos to you guys and hope you can pull something off that is workable.
weber wrote:
Would you take this with you so you can charge anywhere there's 240 V?
We couldn't fit anything else in the MX-5 without losing the already tiny boot.
Very much so, but as you rightly point out it depends on space requirements. I'm not doing an MX-5 conversion, I should have more space. The added benefit of one charger per 48V module is also that you don't need to further isolate the charging output with diodes as no cells need to be paralled up.
weber wrote:
In theory, we can do a 1 hour charge anywhere if provided with a 50 amp 3-phase outlet, just using the existing VF drive.
Can your battery do that? ie. 1C continous charge rate?
weber wrote:
But of course it's more like a 10 hour charge when using a 240 V 10 A outlet.
The curse of a larger pack Image or should I say double edge sword ...   though I'm sure you will be able to live with a standard outlet for just oppurtunity charging. You should be getting >=6.7km/hour of charging from a 2.4kw charger, assuming a efficiency and PF of 70%, and 250WH/km. I'm picking this should be plenty for daily commutes - but could be a drag for deep discharge. But probably you should be able to catch up again soon enough over the next day assuming you are just going to do another daily commute. Better yet, improve your fuel costs, charge at work! Image
weber wrote:
Not really. The amount of copper in a 50 Hz transformer of sufficient power would probably make it cost more than a switchmode charger and we certainly couldn't take it with us.
Ahh that's true. You'd need be better off with a flyback setup like in a computer PC PSU.

weber wrote:
Having two high impedance (via two 100-500K ohm) connections to battery + and - and monitoring the voltage drop across these would be much better.
I assume you're aware that just measuring a static setup like this will not detect insulation failure from mid pack to chassis.
Sorry, let me clarify ... the high resistance is from batt +ve to chasis, and another one from -ve batt to chasis, each monitored separately. Insulation failure from mid pack to chasis will generate a warning because a conduction path will flow through the high resistance via the chasis to the mid pack. If it is exactly mid pack, you should technically get equal currents in both. If it is skewed from mid pack you should get different currents flowing in the resistors due to the different potentials.
weber wrote:
Also to note that I was told that these have to be switched in to prevent corroding of the contacts (if you are not breaking up your pack) from parasitic currents.
Sounds interesting. Not sure I understand what you're saying here. Please explain further.
I have learnt from another forum that small leakage currents over long periods of time can corrode contacts as you are wearing the metal away. This is exemplified with the process of electrolysis, using a high voltage DC small current source, place the electrodes in a water solution with electrolyte mixture (baking soda say). Even with small currents you will see corrosion on the electrodes. A similar issue occurs with these high impedance resistance connections.

Further to that, they may have to be disabled during high current draws from the traction pack due to noise on the line. This may give false positives or mess up the sensing circuitry, perhaps a high commom mode rejection ratio differential or instrumentation amp would be a good candidate for limiting this effect.

weber wrote:
I'll use two connections so I can tell if there is a short at all locations (unless I get two identical shorts across each of the two high impedance resistors - in which case the main fuse "should" blow).
It could be lethal insulation failure caused by water bridging across. This would not blow a fuse. And won't a single short from mid pack have the same effect, as mentioned above.
The leakage detector doesn't detect short across the pack, only leakage from pack or traction circuit to chasis. So if water bridged across mid pack to chasis, the leakage detector would sound. If it bridged across the internal batteries inthe pack without touching the chasis, then you either have to rely on your BMS for the warning, or fusing per pack. You could however encase the batteries in a metal box that is connected to chasis ground, and if water gets in, there is a good chance that it will short from battery terminal to its box, hence triggering the leakage detection.

weber wrote:
I think we'll use one of those Bender insulation monitors.


Do you know pricing for these?



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Post by coulomb » Mon, 18 May 2009, 19:23

Hemonster wrote: Can your battery do that? ie. 1C continous charge rate?
Even Thunder Sky are rated at 3C maximum charge rate. That's assuming a constant 25˚C of course. But I think it would be possible to do a 80% charge in less than an hour. Charging seems to be endothermic, as well.

Edit: however, "standard" charge is 0.3C. it might be time to do some torturing of the test cell, but I'm not sure where to get a source of 120 A to charge it with. Probably a 12 V battery and a water cooled resistor.
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Post by Electrocycle » Mon, 18 May 2009, 19:46

welder :)
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Post by Hemonster » Mon, 18 May 2009, 19:57

Johny wrote:
What she meant was that if the BMS was to attempt to disconnect the pack due to a cell going under-voltage (maybe over as well), then the BMS would be damaged.
Ahh, good point Johnny. I did have that in the back of my mind and intended to ask them about it.
Johny wrote:
MOSFET dies due to massive over-voltage - and if luck with with us it goes open, but most likely it just shorts out and we may never know (depending on monitoring systems)!
Yes, a dangerous situation - the system needs to be more integrated with the primary current loader, ie. the VFD via an opto coupled line as you suggest.



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