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NG3 chargers can't current limit on lithium batteries?

60322 Views 144 Replies 21 Participants Last post by  jollmo
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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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.
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).
I wonder if the temperature compensation is taken care of in this logic chip?
Check out for some temp probe (and general) info.
Yes, that is a great thread. What I was wondering is if the chip does the actual controlling of the ending voltage then the replacement unit could be programmed to take input on the same pins and do something different with it.
I see. Well it depends on how the probe is wired. The way I understand it, the chip sees a reference voltage that has some relationship with with the actual measured pack voltage. We can manipulate this reference voltage using the voltage pot. If Zivan wired the probe "inline" with this signal line I would think we could only use it only for it's intended purpose of lowering or raising the voltage setpoint. If the probe really is on it's own signal line then we probably can use that as a signal line as you wish to. With the right programming you should be able to signal on the line any number of variables using a multi position switch with different resistance values or just a SPST switch for a simple binary hi/low signal.

If what you're ultimately after is simply a CC/CV charge profile that terminates charge at 0.05C I don't think we need anything more than the mod chip itself. The way I understand it, just like voltage the chip sees a reference signal corresponding in some way to the charger current output, so it would be a simple matter for the chip to terminate charge once the current drops to the specified reference level. The reason I believe the chip must receive a current reference signal is because manipulating the current pot lowers and raises current output of the charger, even in Phase one (CC) mode.

If we can use the temp probe, I'd like to use it as a temp probe, but at proper correction value for LiFePO4 cells. The best reference I have to what that might be is the Thunder Sky owners manual that suggests raising charging voltage 100mVpc at -35degC. This implies a temperature compensation of -1.82mVpc per degC standardized at 25C. At 110 degrees that's a 79mVpc drop in voltage, or almost 2 volts with 25 cells.
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Dave posted pictures of his NG3 and NG1. Same (output) voltage ranges but different current capabilities. Most of the resistor values are readable. Can this help answer your question? I'd assume 99% of the Zivan chargers out there started life as Pb chargers. My hunch is each model uses different hardware revisions for the power section and the logic section is generic between them.
Do you have any idea what could happen in the worst case situation testing the a different logic board? Any chance that something might burn up in the charger due to over current or is there enough in place that maybe the worst that could happen is messed up voltage settings and timeouts? If only the latter then that is easy to deal with. Just babysit the pack when charging and unplug the charger if things go wrong.
Have you taken a look under the stickers to confirm both your units are using ST62T25B6 microcontrollers? I'll check mine next time I have cause to tear out my dash for access. If they are, then this mod chip adapter will at least be electrically compatible and no harm will come from testing it out. We still might find that some singlal lines were crossed or something like that, but that won't physically damage the charger in any way (and would be easy to fix in software.)

BTW, I was reading an old thread from 2005 mention the reprogramming fee was only $40 back then. ZivanUSA is double that now.
I think at this point the best to get a few boards out and just let you guys help run some tests. I'll work on getting some boards ordered and assembled as soon as I can.
Hi Dave. Any news on the boards yet? Just checking in.
Sorry for the delay, I've been sidetracked. Boards are in, parts are in. I just need time to get them assembled and tested. I'll try to get them done soon.
That's great! Take your time, I was just curious as to how things were going. :)
My charger is modular and i will include schematics of each of the 5 modules after I learn how to convert them to pdf files. They are now *.eps. will do an online converion of EPS to PDF. There are plenty of other free sites as well as software out there.
I was able to convert my files to pdf. Now they are too big to insert. I'll work on that.

If you ZIP comprees the PDF file, the message board allows up to 2.38MB attachments, instead of the measly 97.7KB it allows for most others.
Well, I receive the chip today. Thanks! Can't do much until I also receive the programmer I found on eBay.
Let me know if you have any questions. I realize there isn't a user's manual yet.
It'll probably be a couple of weeks to receive the clone Pickit 3. Hopefully David already has the debugger in hand and will have a lead on me.

Have you experimented with getting more than the rated 10 amps out of your charger? Using the trim pot and the stock chip, I'm able to adjust it up to 13.9 amps with no ill effects so far.
Can't say that I have. I've usually been more concerned with turning down the output. We're lucky to even find a 15A outlet around here.
I forgot you'er running around 160V. My GEM NEV peaks out at about 85V while charging. 85V * 13.9A = 1181 Watts. Well below the 1800 Watts a standard 120V 15A outlet will handle. That extra 40% is appreciated.
Has anyone else ordered and received their chip yet? I'm still waiting for the programmer and would enjoy hearing from others that are already playing with the device.
Charger dead. Watch out.

Well I changed the voltage and current values, programed the chip and verified programming, swapped out chip in NG1. All I got when plugged in was a click from the relay and a solid yellow LED. Swapped back to old chip and got same thing. NG1 now dead and on it's way back to Zivan for repair. Wish I would have charged the batteries before the swap. No wheels for a few weeks. Thanks for trying anyway.
Any smoke or fireworks? It would be nice if we could figure out what happened.From the sounds of it your charger might still be ok. If the main relay still clicks and you have the yellow LED then most of the charger is working. This is the default behavior without a chip installed. Any chance the chips were installed backwards or have a bent pin? When you programmed the chip did you use the PicKit in debug or programming mode?
Could have been backwards. I oriented pin one to match the old chip's pin one. I think I programmed in debug mode. I'm not shipping until tomorrow so I could pay with it some tonight, but not hopeful. I'll try rotating the old chip 180 degrees and see if I get some life showing.
OK, I'm an idiot. When I put the old hip back in I reversed it. I also just broke a pin on the old chip taking it back out! :rolleyes:

I reprogrammed the new chip, but this time not in debug mode. I installed the new chip, and get the beep, and the LED is green this time, and fan is off. So, I beleive it thinks the pack is already at or above the charge voltage and ends charging instantly. How do the voltage and amperage trim pots currently work with the new chip? Do they have any effect right now? It's either the trim pots or the formula used to derive pack voltage from the reference voltage is not applicable for the NG-1.

Time to go solder that pin pack onto the old chip. I don't have a clue what's the matter with me today. :confused:
Is this a 3.3 volt or 5 V PIC? I've played it safe so far setting the voltage at 3.65 (3.38 at the PIC).
25 LiFePO cells. Been charging at ~86V (~3.45Vpc) until amps drop to ~1 Amp.

When Zivan reprogramed my NG1 for lithium, they replaced the entire logic board. This new board has a row of five jumper pairs, not four. They are labeled MD, C0, C1, TP, and AH. TP is the pair currently shorted.
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