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Discussion Starter · #1 ·
We've been using an NG3 charger for the last several years to charge our lead acid pack. We originally had Electric Conversions install an optional low current mode switch on the NG3 so that we could charge on a standard 15 amp outlet while at work.

We're in the process now of upgrading our pack to lithium. Before we purchased the new batteries we had contacted Electric Conversions regarding modifying our NG3 to handle the lithium batteries. They said they would be able to modify the charging profile for our configuration.

Now, after just receiving the charger back from Electric Conversions we noticed that the low power option had been removed from our unit. They failed to mention this little detail to us. I contacted them and all I was told was we can't current limit on lithium batteries and it would take to much time to do. If you can current limit on lead acid why not lithium? If the hardware of the NG3 supports current limiting on lead acid it should be just as capable of current limiting on lithium. I realize that it might require a separate charging profile or something but it can be done.

My plan now is to figure out the profile programming of the NG3 and modify it myself. I have a lot of professional experience in reverse engineering electronic systems and feel that it can be done. I know a lot of people have been down this path before on here and have found some decent information. If anyone has information about the NG3 charger that would help speed up the process it would be appreciated.

Two lessons here, NG3s don't currently have a current limiting capability on lithium and avoid Electric Conversions. After reading some of the other posts on here, I'm not the only one to have problems with this company.
 

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We've been using an NG3 charger for the last several years to charge our lead acid pack. We originally had Electric Conversions install an optional low current mode switch on the NG3 so that we could charge on a standard 15 amp outlet while at work.

We're in the process now of upgrading our pack to lithium. Before we purchased the new batteries we had contacted Electric Conversions regarding modifying our NG3 to handle the lithium batteries. They said they would be able to modify the charging profile for our configuration.

Now, after just receiving the charger back from Electric Conversions we noticed that the low power option had been removed from our unit. They failed to mention this little detail to us. I contacted them and all I was told was we can't current limit on lithium batteries and it would take to much time to do. If you can current limit on lead acid why not lithium? If the hardware of the NG3 supports current limiting on lead acid it should be just as capable of current limiting on lithium. I realize that it might require a separate charging profile or something but it can be done.

My plan now is to figure out the profile programming of the NG3 and modify it myself. I have a lot of professional experience in reverse engineering electronic systems and feel that it can be done. I know a lot of people have been down this path before on here and have found some decent information. If anyone has information about the NG3 charger that would help speed up the process it would be appreciated.

Two lessons here, NG3s don't currently have a current limiting capability on lithium and avoid Electric Conversions. After reading some of the other posts on here, I'm not the only one to have problems with this company.

Not that it helps you much (but perhaps you can fix it yourself) but if you search the battery/charging forum I documented my modifying my ng3 for lithiums from lead.
Really was a piece of cake and it will limit current i dont belive it would care what battery chemistry you use a voltage limit is a voltage limit. Sounds like they set it too high. There are 2 settings on the ng3 you can change ending voltage and ending current. If you are around the correct voltage from lead (ie if you had a 144Vdc model and use 48 lifepos you are fine.) I went from a 156vdc to 52 lifepos lowered the ending voltage and fininshing amperage without removing the charger from the car. It will actually finish charger and go green but I like to charger to 80% so i use a timer. When i ballance i let it go green.
 

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I know I'm off the subject but maybe someone can help me here. I have an ng3 programmed for a 144 volt lead acid pack. I used it the first time on a new pack of batteries and it worked fine. I believe the voltage was about 151 when I started the charge and I ended about 152. After I discharged the pack some to about 150 volts I decided to top off the charge again but now I get a "battery not detected" alarm. Zivan has not answered my emails yet. The connections are good and I am getting 150 volts to the unit. Can someone help me?
 

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Discussion Starter · #4 ·
We found the schematics online for the NG3 charger's control logic and have verified them, so we're already close to resolving our problem. Ideally we would replace the entire control board because it's outdated at best. But, the far simpler approach is to just replace the existing socketed microcontroller with a more modern device. This will require developing a small adapter module with the new chip and additional I/O that can plug into the existing socket. Going this route would allow others to be able to modify their charging profiles and add additional features without the need for sending them in, as is required now.

We are primarily interested in adding a selector switch that will allow us to charge in both high power and power modes. However, we have seen others inquiring about various mods to their controllers. We're interested in finding out what others might want added to their NG3?

We would considering selling these modules if anyone was interested. We're curious to find out what the the interest level might be in these devices?
 

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We found the schematics online for the NG3 charger's control logic and have verified them, so we're already close to resolving our problem. Ideally we would replace the entire control board because it's outdated at best. But, the far simpler approach is to just replace the existing socketed microcontroller with a more modern device. This will require developing a small adapter module with the new chip and additional I/O that can plug into the existing socket. Going this route would allow others to be able to modify their charging profiles and add additional features without the need for sending them in, as is required now.

We are primarily interested in adding a selector switch that will allow us to charge in both high power and power modes. However, we have seen others inquiring about various mods to their controllers. We're interested in finding out what others might want added to their NG3?

We would considering selling these modules if anyone was interested. We're curious to find out what the the interest level might be in these devices?
I would certainly be interested down the line. I expect my lead acid pack to last two years more and then I will be switching to lithium. And I am not too happy with the company.
 

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Discussion Starter · #6 ·
Just put the finishing touches on our NG3 charger upgrade. Since Electric Conversions left us high and dry, we had to modify our charger ourselves in order to allow charging at different rates. We ended up replacing the outdated socketed microcontroller with a newer PIC on an adapter board. The prototype is up and working great, we can charge now at four different rates, easily adjust the CV point, and if we lose a cell at some point we can quickly recover.

We're not planning on releasing this as a formal product at this point but if anyone finds themselves in a similar situation we will be glad to assist them in doing the same.
 

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Wow, nice job! Now that should helps some folks. This is what a DIY forum is all about. :):)

Perhaps you can explain the connection and programming method?
 

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Discussion Starter · #8 ·
The only connection I use on the board is a standard 6 pin programming/debugging header for the PIC. I use a cheap ($45 at Digikey) Pickit3 USB programmer/debugger from Microchip to interface to the board. I had to bend the pins slightly (something to change if I ever do another version) in order to be able to connect the Pickit to the board while it is installed in the charger.

I added another set of input pins inorder to measure the input power as well as the output power; however, in order to keep things simple I'm just measuring the output and applying an average efficiency correction value.

The circuit boards cost me $35 and the components another $10. I already had the Pickit and the Microchip MPLAB software (with Hi-Tech Lite C compiler) was free. All total it cost me less than $50.
 

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Discussion Starter · #10 ·
We only have our one NG3 unit to test so it's hard to say for certain regarding the other NG models. My guess is most likely yes on the NG1 and almost certain on the 240V NG3. To the best of my knowledge Zivan uses the same control board and firmware for the different models. What primarily changes are the power components.

I've attached the schematics of the digital control board. I did not create the schematics myself, I found them online a while back but can't find where now to give them proper credit. I can say that they matched perfectly to my NG3 120Vac 144Vdc unit.

If possible, I would recommend opening your charger up and seeing what type of control board is inside. If the programmable chip being used is a 28 pin ST62T25B6 then you're probably set.

I will post my device's schematics and my prototype PIC code here shortly once I have had a chance to fix a few things and document them better. Additionally, I will build the hardware module for anyone interested for say $35, just to cover my costs. This will NOT include programming. It will be up to the end user to program the device and verify that it is working properly. The reason for this is because we are not in this for the money so we also don't want to take any liability should any battery packs be destroyed.

Anyone wanting to use one of these devices will need to be able to do some very basic programming. That said, PIC programming, especially with my example code provided, should be extremely easy.

I'll post more as time permits.
 

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Thanks for the info. I found that the Old_NG3_Logic.pdf file can be found at http://aaron.birenboim.com/EV/ I also found that Greg Solberg could be one of several people including a firmware engineer at Tesla but I didn't search any further. His name is at the bottom of the schematics pages.

I'll open my NG3 and NG1 and take pictures of the control board. Maybe we can determine if this mod can work in the NG1 as well.

As for programing the chip, I have a Melabs U2 Programmer, will this work for programing? I should be able to figure out the code from your example since I've programmed in BASIC, Pascal, FORTRAN, and various command languages 15+ years ago.
 

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Discussion Starter · #12 ·
Unfortunately, the only programmer that will work with my module is Microchip's PicKit3. Even the PicKit2 doesn't support the newer PIC chip that I used. Microchip does sell other programmers that would work but they are more expensive and would require a pin adapter. You can buy a new PicKit3 from Digikey for $45 or used one off of Ebay for around $20. Ebay also has cheaper PicKit3 clone devices but we can't say for sure if they work or are reliable.

I've went ahead and made a few small improvements to the module from the original prototype. I documented the schematics and attached them here.

I'll clean up and document my prototype code as well. I'll try to get it posted as soon as I can find some time.
 

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very interesting. Does this mean we can now set our own charge profiles in the software, or is this still hardware limited.

For example, I have an old NG3 that was used to charge 120v lead acid, and I'd like to change the profile to something for 144v LiFePo4. Can I set the CV point and then a minimum current cutoff that terminates the charge?
 

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Can I set the CV point and then a minimum current cutoff that terminates the charge?
If the minimum current cutoff can't be set then merely lower the ending voltage like I have done with my NG1 and NG3. I'm ending at 3.465vpc right now and the number of Ah which go into the pack after the charger drops into the "yellow" phase is actually quite minimal so charging times really aren't that much longer.

Depending how the timer is done it could be that when the current drops to a particular point the timer counter could be incremented/decremented appropriately to end the charge.
 

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Discussion Starter · #16 ·
The schematics for the logic board and my replacement microcontroller replacement module have already been posted here. I will try to have my sample code cleaned up, documented, and posted here within the next few days but please bear with me. I will have to order more boards before I can sell the modules to anyone, but I'd like to find out what the interest level is before I place the order. So please just send me an email for now stating that you'd like to buy one. But before you do, I would recommend that you examine your controller and see if the logic board inside is similar to the picture of mine that I posted.

Keep in mind that the logic board schematics are for a 144Vdc out version of the NG3. Your model of NG charger may have some different valued resistors, shunts, and voltage bias points. More than likely my module will still work but you may have to run a few additional tests and measurements. I will try to explain more in detail later.

There are only two settings to configure for the controller, a voltage limit and a current limit. For my unit, I have two external toggle switches that I mounted to the NG3 case and then connected to the C0 and C1 pin header inputs which are found right next to the LED. When the program starts it reads the position of the two switches, telling me which of four current limit settings I want to use. I then set the voltage set point and the desired current limit. All that is left is to set the SOFT_START pin low in order to enable the charger output.

Once the charger output is enabled, nothing else is technically required. The charger will current limit at the desired set point during CC until it hits the CV point, at which point it will maintain voltage, naturally decreasing current. If you did nothing else in your code the charger would just stay at the CV point forever. So, you can setup your charger to do just about whatever you want. You can stop charging immediately at the CV point, you could stop after a certain period of time in CV, or you could stop at a minimum charge current.

In other words, you can set your charger up to be a simple CC/CV single stage charger, or you can make it as absolutely complicated as possible.
Then there are the LEDs, the AUX relays, and the sounder. Again, do what you want with them. Hopefully when I post my code it will become clearer.
 

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This is really exciting. Zivan makes a great charger but the lack of interest in making true Lithium charge curves is going to hurt them in the near future. With the flexibility added by this mod chip I think we have probably the best charger for the money. These things go for cheap refurbished.
 

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Zivan makes a great charger but the lack of interest in making true Lithium charge curves is going to hurt them in the near future.
The ideal curve for Li-Ion is a plain old CCCV, nothing fancier. Your plain Lead-Acid charger (no "profile") will work just great with Li-Ion. As long as the BMS (you do have a BMS, right?) is able to shut the charger on or off, your Li-ion pack will be charged most efficiently and completely by such a charger. Zivan knows that.

Please see "the 3 stages of Li-Ion charging": read or watch.
 

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They are pawning off lead acid charge profiles to those that ask for a lithium charging, or asking for a $600 minimum charge to create a proper and true CCCV charge profile. There currently is NO generic CCCV charge profile to choose from Zivan. With all the lithium conversions going on, you think you would have taken the time to create even one generic CCCV profile. They don't care. They have good hardware, but the top people at ZivanUSA suck IMO.

Thankfully this mod chip clears up the whole issue and the only time I'll ever deal with ZivanUSA is if the charger breaks. Everyone happy (and BMS free).
 

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I wonder if the temperature compensation is taken care of in this logic chip? If so, it seems that the pins for temperature input could be used for input to control the charger externally: to turn down the current or shut it off completely.

FWIW, Attached are photos of the logic boards in my 115V NG1 and 230V NG3 both with the same programming. The paper work says it is the ZV curve #7 but the sticker on the chip says ZV6, in any case it is set for 69.3V Saturation and the current just tapers down close to zero until the timer during the "yellow" phase times out.

I don't think there is anything wrong with using a re-purposed lead acid curve except that the proper charge profile for LiFePO4 calls for a CCCV curve which terminates when the current drops to 0.05C. For my 200Ah pack that would be 10A, just barely above what the NG1 can do. I compensate by charging 20 cells to 69.3V or 3.465vpc which may still be a little high.

Here is the NG1 115V control board:



Here is the NG3 230V control board:

https://picasaweb.google.com/lh/photo/X7hGcRCA5ZHTl6CRz91NFNMTjNZETYmyPJy0liipFm0?feat=directlink
 
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