# MegaPac



## frodus (Apr 12, 2008)

the 5V modules have different fault responses than the 12V. The 12V units recover automatically (foldback). The lower voltage ones may need to be reset. You should be disabling the module to shut off, not turning the output on and off. It may be getting some nasty spikes in voltage.

What you should do, instead of the contactor, is use the Gate In pin on the megapack module. This allows you to enable/disable it remotely. Not sure what the module pinout is (there's a few different configurations with different DC-DC's inside, micro, mini, VI-200, JI-200, etc)

Do you have the vicor information? What is the model of the megapack, and what is the model of the two modules. Pics would help. I've got a ton of experience with these and own several front ends (Flatpacs, VI-200's, VJ-200's and some micro's)

if you want, feel free to email me from via my website in my sig. I don't want to post here due to spammers.


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## Zappo (Sep 1, 2011)

onegreenev said:


> PS: I will be testing the abilities of FAST charging to the A123 pouch cells. If I get this to work properly I am going to double up two modules and run them in series and see if I can get this to pump out 80 amps and see what will happen. I will be graphing the voltage on the PowerLab 8. I will count and log AH and Voltage and Temp of the connection.


Pete, I'm guessing you mean parallel instead of series and yes, you can. I have one I bought that has three of those 5 volt/40 amp modules strapped together. I've seen some on eBay that have a 10 modules strapped together. That would be 5 volts at 400 amps.
I guess they use these that way.as power supplies for electroplating.

Mike


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## dougingraham (Jul 26, 2011)

onegreenev said:


> Vicor MegaPac. I am using one of my Vicor MegaPac's as a power supply for charging a single A123 cell. I am using a 5 volt 40 amp module for the charging.


I cant tell you for certain why it is shutting down but if 40 amps are flowing and you are just opening the circuit then it is probably shutting down on an output overvoltage. They put a small inductor in the output for stability and when you suddenly open the circuit the voltage across the output is going to go ballistic for a short period of time.

There is a connector on the back of the megapac that can be used to shut down the individual outputs.

I would also recommend that you trim down the 5V output to something that won't destroy a cell if your shutdown procedure fails. You can trim these with a single resistor. Usually you can trim them down 20% and up 10%. I would trim it down as low as you can which I believe is 4 volts with the 5V modules. At least at that voltage the electrolyte wont start breaking down although the cell would still be overcharged and plating would probably occur if you leave it there too long.

I use three of the 5V modules in series each trimmed down to 4.53 volts as my DC-DC converter (13.6v). I am using an 8AH buffer battery that can handle the full charge current. What you want to do is get some of the matching booster modules (they have a B suffix) and parallel those with one of the regular modules. The output current balance with the booster modules works properly and you may have issues with load sharing between the modules if just paralleling the regular modules.

There is a tool on Vicor's web site to calculate the trim resistors. The datasheets for the modules and MegaPacs are also available.

Best wishes!


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## onegreenev (May 18, 2012)

Zappo said:


> Pete, I'm guessing you mean parallel instead of series and yes, you can. I have one I bought that has three of those 5 volt/40 amp modules strapped together. I've seen some on eBay that have a 10 modules strapped together. That would be 5 volts at 400 amps.
> I guess they use these that way.as power supplies for electroplating.
> 
> Mike


Yes, I meant parallel.


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## onegreenev (May 18, 2012)

Doug,

So the reason for the spike is more in the module because of the small inductor and not because of the contactor coil causing a reverse spike? I think I understand that. I will check to see which pins allow the turn on and off of the modules. For what I am doing I do not need to reduce the voltage. I think the issue with such high voltage is because of a faulty cell. The cell I am using was a damaged one from an overdischarge long before I ever got the cells. It was one of the last bunch I pulled out of the pack that was sitting very very low in voltage. I got it to come up but it seemed a bit sluggish for a little bit. I will try a different one later. I am not concerned about the voltage anyway. Not for what I am doing. If the voltage rises to a high level but settles I will check the issues that ensue from that. It is after all battery testing.


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## dougingraham (Jul 26, 2011)

onegreenev said:


> So the reason for the spike is more in the module because of the small inductor and not because of the contactor coil causing a reverse spike?


Any inductor will see a voltage spike if current is flowing and the current path is suddenly opened. There is energy stored in the inductor and it must go somewhere when the circuit is opened. In the case of the contactor coil the spike would be at the contactor coil and not at the contacts. Of course there will be a spike at the contacts but it has nothing to do directly with the contactor coil. And you are probably causing damage to the contacts when you open it with 40 amps of current flowing. It might take a few thousand cycles but it is hard on it. The probable failure will not be welded contacts but a gradual increase in contact resistance as the contacts become pitted.

If you look in the side of a module you will see the coil on the positive lead. It is just there for output stablilty. And it is just a guess that suddenly opening the circuit when you are pulling 40+ amps is causing the module to shutdown its output.


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## frodus (Apr 12, 2008)

What kind of connector/pins are on the VI-200 modules?

There should be V+, V-, Sense+, Sense-, Trim, Gate In and Gate Out.... IIRC

I need more info. VI-200 isn't enough information.


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## frodus (Apr 12, 2008)

http://cdn.vicorpower.com/documents/design_guides/megapacautorang_designguide.pdf

Page 14

The J10 connector (on the back of the unit, above the power input) has the enable pins on it. There's a general shutdown input, which is J10 pin 12. Connect that to J10 pin 10, which is signal ground, if you want to disable the supply.


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## onegreenev (May 18, 2012)

I saw that. Busy right now but will have a go at it tomorrow. I will post results.


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## onegreenev (May 18, 2012)

frodus said:


> http://cdn.vicorpower.com/documents/design_guides/megapacautorang_designguide.pdf
> 
> Page 14
> 
> The J10 connector (on the back of the unit, above the power input) has the enable pins on it. There's a general shutdown input, which is J10 pin 12. Connect that to J10 pin 10, which is signal ground, if you want to disable the supply.


I had one molex on the back of one of my MegaPac's and it had pin 10 occupied and pin 7 occupied. Since I only want to turn off or on the one module I put one of my 5v 40A modules in slot 7. I then connected a switch between 10 and 7. By connecting the switch module 7 will not run. Turn off the switch and module fires right up. I turned it off and on a few times and never once had it glitch out on me. Fired up perfectly. So to control each module you can connect to pin 10 and any other up to pin 8 to control modules on a single basis. If you need to shut the whole thing off then pin 12. Works beautifully. Elegant and how it should be done. It is after all how they built the sucker. Thought it was more complex. My learning curve. 

Thanks for the extra help on this matter. 

Pete 

I have 6 of these MegaPac's. I have 6 of the 5v 40a modules. Then I have a bunch of 12v, 5.2 volt and some 50 and 70 volt modules. The highest amperage modules are the 5v at 40 amps and the 5.2v at 28 amps.


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## frodus (Apr 12, 2008)

One thing to keep in mind:
http://cdn.vicorpower.com/documents/applications_manual/DesignGuideAppsManual_200J00.pdf

Read page 7.

The 3.3V and 5V output modules have foldback current limiting. If you max it out, it will fold back. I'm not sure if these modules keep resetting, I haven't tested them like that.


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## onegreenev (May 18, 2012)

Plowing through this PDF right now. Never saw this one. I have figured out about trimming the modules and was successful. Not using a trimmed module right now but I may to keep the upper voltage limited to protect the cells. I will keep you updated with my results. I will check to see if there is any folding back while charging a cell. I will let you know as well.


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## onegreenev (May 18, 2012)

Got my volt meter today so I can track small changes. Got a different cell connected and it is now holding a pretty slow and steady 3.438 volts and 45 amps and now 9.3 ah into the cell. No folding back or changes what so ever and staying nice and cool.


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## dougingraham (Jul 26, 2011)

onegreenev said:


> I have 6 of these MegaPac's. I have 6 of the 5v 40a modules. Then I have a bunch of 12v, 5.2 volt and some 50 and 70 volt modules. The highest amperage modules are the 5v at 40 amps and the 5.2v at 28 amps.


I have 5 of them with a similar mix of modules. If you are going to parallel them you want to see if you have a 5V/40AB module. The B suffix is a booster module and is intended to be paralleled. The booster modules cannot be used stand alone. They slave off of the master module next to it and share load perfectly. This will not be the case if you parallel master modules. The one with the higher output voltage will carry more of the load. If you are going to parallel them you will probably want to put a trim pot on one of the modules and adjust that one for maximum current. If you turn it up too high it will carry all of the load and if you turn it down too much the other module will carry all the load. The booster modules are the way to go. With modules trimmed down in voltage the output current goes up because the module limits output to approx 200 watts. With a single booster I saw currents of 86 amps (master was trimmed to 4.53v). The booster module needs to match the voltage and current rating of the master but does not need to be trimmed.


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## onegreenev (May 18, 2012)

dougingraham said:


> I have 5 of them with a similar mix of modules. If you are going to parallel them you want to see if you have a 5V/40AB module. The B suffix is a booster module and is intended to be paralleled. The booster modules cannot be used stand alone. They slave off of the master module next to it and share load perfectly. This will not be the case if you parallel master modules. The one with the higher output voltage will carry more of the load. If you are going to parallel them you will probably want to put a trim pot on one of the modules and adjust that one for maximum current. If you turn it up too high it will carry all of the load and if you turn it down too much the other module will carry all the load. The booster modules are the way to go. With modules trimmed down in voltage the output current goes up because the module limits output to approx 200 watts. With a single booster I saw currents of 86 amps (master was trimmed to 4.53v). The booster module needs to match the voltage and current rating of the master but does not need to be trimmed.


Got a 5v 40A booster?


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## dougingraham (Jul 26, 2011)

onegreenev said:


> Got a 5v 40A booster?


I have three but they are in use. I keep looking for a deal on EBay that has some. I would like at least one spare.

I don't know what I was thinking earlier. The way you are using them paralleling master modules will work fine. Both will output max current attempting to raise the output voltage. When the output voltage gets close to the regulated voltage is where you will see the load share unevenly. But with your use that doesn't matter.


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