# Elcon/TC charger 6 kW idea on 3-phase



## Coulomb (Apr 22, 2009)

z_power said:


> I couldn't find any info about 6 kW ones but comparison of external dimensions suggests three blocks of 2kW inside; can anyone confirm this?


Unfortunately I can't confirm it, but I got the impression that they always used even numbers of chargers. So a 6 kW unit would be four 1.5 kW chargers paralleled (inputs and outputs).

However, there are 2 kW chargers, so it is also possible that they have 3 2 kW chargers in one box.

Be aware that you need some isolation to control the chargers; the processor is loosely connected to pack negative through the current sense resistor and its amplifier. I know of someone who paralleled two chargers, and also paralleled the control signals (pins 1-3 of the 7-pin round connector). This ended up blowing up both processors. In fact, I think that's the pair that Pdove is working on right now. We're not totally sure that paralleling the control circuits is what fried the processor, but it sounds fraught with danger to me.

When two chargers come in one box, there is only one control circuit, and the chargers have different firmware - one is a master, and the other is a slave. (For three and more chargers, there would be one master and n-1 slaves). The master communicates to the slave(s) through the serial port; the slaves listen only. There is a special "channel" for the master to talk to the slaves over. Basically, the master works out what it wants to do, based on 1/n th of the power and current, and it sends out commands to the slaves to do the exact same thing, assuming that they will take over the other (n-1)/nth (1/2, 2/3, 3/4 etc) of the load.

But of course, you will have no reason to change the way the chargers in the box communicate and so on, just that you will be giving them different active signals. I can't see why this would not work. However, I think you'll end up having to have two chargers on one phase, since I think there will be four in the box. This is unfortunate, but not as unbalanced as putting all four of them on one phase!

I have a 5 kW charger, and can confirm that it is two 2500 W chargers in one box. It has one fan for each 2500 W charger. So you might be able to figure out how many chargers are in the box by looking at the number of fans.

Indeed, this page seems to confirm it:

http://www.tccharger.com/english/Product/T35/51.html










This is for a TC charger; I believe that Elcon chargers are re-branded TC chargers.


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## Weisheimer (May 11, 2009)

I'll point out that the Master / Slave segments in each charger have a common DC ground and as Coulomb points out, that is tied to the negative terminal of the traction pack. 
They use optical isolation in the serial command chain and it is critical that you do too!
It should be safe to follow their lead and parallel whatever groups of these chargers that you desire, but the serial command chain MUST be optically isolated.
I say that with the caveat that I would test for isolation if I were to put this rig together in a 3 phase configuration and I would do that PRIOR to applying full power.


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## z_power (Dec 17, 2011)

Thank you gentlemen for your answers!
Regarding no. of "subchargers" - in case there're four 1,5 kW units inside they could be connected in pairs, like L1 to unit 1&2, L2 to unit 3&4, N is common. At 230V L-N each phase would carry 3 kW so ~13A; neutral line would carry ~13A too thanks to high power factor. All within 16A limit of popular IEC sockets and a few charging stations I could visit.
As for control interface - am I right in my thinking it's already "split" by manufacturer and isolated from grid side? User has only one 7-pin connector to control charger as a whole unit, no access to "subchargers" at this level. No extra problem here, just single 2-5V signal needed or even simplier relay giving on/off control.
Well, actually I could connect my present 3 kW unit to L3-N, why not?
I'll give it a try, must wait a few weeks for shipping but will let you know as soon as warranty on new 6 kW unit is void thanks to cover removal ;-)


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## Coulomb (Apr 22, 2009)

z_power said:


> - in case there're four 1,5 kW units inside they could be connected in pairs, like L1 to unit 1&2, L2 to unit 3&4, N is common.


Or why not connect L2 to unit 3 and L3 to unit 4? That will reduce the neutral current a bit, and balance the loads a little better.



> As for control interface - am I right in my thinking it's already "split" by manufacturer and isolated from grid side? ... No extra problem here, just single 2-5V signal needed or even simplier relay giving on/off control.


Yes, I realized that as soon as I had finished typing my spiel. No extra problem.



> Well, actually I could connect my present 3 kW unit to L3-N, why not?


Wow, a 9 kW charger. That would be a reason to do the unbalancing you mentioned, except I'd still distribute the 6 kW charger as I suggested, and run the other charger on L2 and L3, so it will be perfectly balanced when both chargers (6 units) are plugged in, and not too badly unbalanced when only 1 is plugged in. There is slightly less total current in conductors my way (since the N wire in the 6 kW charger will have a little less current this way). I think I remembered that right - the N current is the sum of the loads for 1 or 2 phases, but only the unbalanced current for 3 phases.


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## Coulomb (Apr 22, 2009)

z_power said:


> Well, actually I could connect my present 3 kW unit to L3-N, why not?


Oops, I forgot to add: in the 9 kW case (6 kW plus 3 kW) with two separate cases, you will as Weisheimer points out (thanks, Mark; hope I got that right) need two control circuits for the current control, one isolated from the other (and as usual, both need to be isolated from nearly everything else, as they are loosely connected to pack minus). 

I suppose you could reflash the 3 kW unit to be two slaves, and tie the serial ports together in an isolated way, but I think it's worth keeping them as separate units, in case something goes wrong with one, you can still use the other while you get that one sorted.


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## z_power (Dec 17, 2011)

So I got the charger on Friday and I've found some time to remove gazillion screws holding the cover. There're three 2kW units inside, slave ones are connected to master trough a mystery box, probably to separate serial data with a few optocouplers. I wonder if one could control them just by sending prepared 79-byte message? 
I'll try to change input cable to 5x2,5mm^2 on Monday and see if it works on 3ph. If any of you, gentlemen, has ideas on experiments I should perform please feel free to post 'em


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## Coulomb (Apr 22, 2009)

z_power said:


> There're three 2kW units inside,


Ooh! Ideal for 3-phase. Good to know that odd numbers of units (>1) are possible.



> slave ones are connected to master trough a mystery box, probably to separate serial data with a few optocouplers.


Interesting. When two units are in one box, they are connected by a postage-stamp sized PCB that is glued to the back of the master control board, and of course buried in their beloved yellow goop. It seems that to drive two or more slaves from a master, a bit more circuitry is required.

It looks a bit like shielded wire, too; can you tell if it's shielded? More likely, it's just round cable.



> I wonder if one could control them just by sending prepared 79-byte message?


Certainly you can control the slaves like that; I know of at least one charger that is running in that configuration. The master won't be listening for instructions, though. But you could re-flash the slave firmware into the master to do that, or re-flash all of them to use some more convenient protocol.

The master-to-slave packet is just 15 bytes (10 active, 5 header and checksum), not 79. It has the "comms descriptor" of COMM_DESC_MASTER, which is the value 0xC5. This is separate to the "listen info" (general data, a copy of the RUN data structure), which has the comms descriptor COMM_DESC_LISTEN, value 0xF0.

Thanks for the info and pictures. As a point of interest, is this one an Elcon branded charger, or TC Charger branded? The Chinese characters on the sticker suggest the latter.


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## z_power (Dec 17, 2011)

It's branded as TC, bought at ev-power.eu (GWL Power); as Herr Brainzel explains here at his blog (german language) it is trimmed for this distributor with one curve only, 189,8V and 27A.

Cables connecting units are in fact shielded with two conductors only so communication is unidirectional as pointed earlier. 

I'll let you know tommorow about any new findings (hope there'll be some...)


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## Coulomb (Apr 22, 2009)

z_power said:


> It's branded as TC, bought at ev-power.eu (GWL Power); as Herr Brainzel explains here at his blog (german language) it is trimmed for this distributor with one curve only, 189,8V and 27A.


Thanks. That's an unusual "trim"; basically it's cutting down the maximum current from 12 A to 9 A (per 2 kW unit), taking it from over 2200 W to just over 1700 W. I wonder if they wanted more reliability from less heating? I can't imagine another reason to cut back the specifications.

Heh, it seems that they are wishing they could adjust the limits, too. Perhaps when we're more organized we tell them how to at least find out what's really in their firmware.


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## z_power (Dec 17, 2011)

Slow progress due to health issues...

It works! At least in the meaning there's no smoke released  I changed input wiring so that each unit is connected between L1-3 and N; works like charm except that CV point is ~1,7V to low (I charge my 56 cells to 191,5V) and current tapering started way to early when there was still ~25Ah to be put into 100Ah Winstons.
I did Ian Bruinsma's resistor mod in my 1,5kW chargers to raise their outputs to 191,5V; I could try it with this 3x2kW but I feel there'd be a lot of tinkering needed to achieve equal syncronized change in three units. This puts me in a row of people patiently awaiting news on firmware modifications.

Regarding cables for serial communication between master and slaves - only two cables from "mysterious box" to slaves are shielded, master connects to box with unshielded 3 conductors, 3rd one carrying +12V (pull-up? doesn't seem like needed from master's side of eventual optoisolation).


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