# Charging with high voltage



## dimitri (May 16, 2008)

Jan,

I'm not sure how to respond to a video which insults the DIY community and well respected charger manufacturers with false statements and bits of information taken out of context, just to prove some obvious theoretical point, while confusing people in the process. So, at a risk of being accused of typing myself smart by someone who has no problems with videotaping himself smart on a weekly basis , I'll give it a shot.

Its true that charging voltage in of itself is irrelevant and useless without reference to a current going thru a battery at the time said voltage measurement is taken. In fact, there is no difference between charger voltage and cell voltage since they are directly connected by thick wires and those voltages are always the same. So, amount of power flowing into the cell ( minus thermal losses ) is charging voltage times charging current, but since power is timeless function, you then have to consider the time that it takes to absorb the power until cell is full. As Jack demonstrated, you can put as much current into the cell as your bench supply is capable of and care less about voltage AS LONG AS YOU KNOW WHEN TO STOP. Well this is the key dilemma when designing a charger, charger doesn't know how much energy is in the cell every time you start charging, so charger must have some reference point to know when to stop. There are couple of ways to do it. One, charge with max current, but stop frequently and see how much voltage drops after current is removed to gauge how close you are to a full charge. Two, charge with max current until you reach a certain voltage level, a "knee" as its referred to often, then continue to reduce the current until current drops to zero or almost zero and stop. Second method is called CC/CV profile, which is demonstrated in the video, and its most popular and easy to implement, so most typical chargers use this method. It doesn't help to understand CC/CV if you suddenly raise the current and say "look how much the voltage is rising", duh, of course its rising, but you are not supposed to raise current in CV phase, so its not a representation of real life scenario, although a good dramatization trick.

I found it hillarious that my HVC cutoff at 3.6V for SkyEnergy cell was so emphatically ridiculed, but when CC/CV method was properly followed the charger was stopped at 3.6V  just like BMS would. I guess I should add to MiniBMS manual a statement like this "don't use HVC cutoff when charging with 200 amp bench supplies". The point is that NORMAL CHARGER will not go over HVC voltage anyway. My definition of "normal charger" is the one with CC/CV profile set to commonly agreed "knee" levels. As mentioned in the video, "knee" level can be anything, there are infinite possibilities, but common charger manufacturers ( but what do they know, they can't even make good chargers  ) have certain knee levels that are widely accepted by most customers, so common BMS HVC levels are relative to those common knee levels, so they can all work together in harmony. If you pick your own knee levels for CC/CV charge process, then you may not get desired results from any BMS and should consider developing your own or just go without one.

Sorry for long winded post, hopefully it took less than 103 minutes to read it 

P.S. My tone may seem insulting, but its a knee-jerk reaction to numerous insults in public and private conversations from certain arrogant and hypocritical person, so I apologize to readers in advance.


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## Jan (Oct 5, 2009)

dimitri said:


> P.S. My tone may seem insulting, but its a knee-jerk reaction to numerous insults in public and private conversations from certain arrogant and hypocritical person, so I apologize to readers in advance.


Thanks for your explanation Dimitri. It's late now, I read it tomorrow again. 

I understand your tone. I found it rather funny to see a sharp discussion between forummers via a video. And the fact that we are all emotional ego's. Funny creatures.


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## GizmoEV (Nov 28, 2009)

I have to agree with you Dimitri. He doesn't want to see the value in a simple BMS as a protection measure. He uses a ridiculous charge current for the systems the miniBMS would be used on to claim the BMS is useless. The BMS is to be used with a well behaved charger on a normal vehicle pack from a household outlet. Since voltage is the easiest thing to measure regardless of charge time it makes for a simple cutback and turn off indicator. Jack's method would require Ah counting out and in, temperature monitoring, dv/dt monitoring, and the intelligence in the whole system to automatically do what he did manually. There is no way my Zivan will put out 200A into my pack. It will, however, happily put out 6-38A. With 6A at the end I don't think I'll be "leaving a lot on the table" when/if the BMS shuts down the charger. Now, if only I could get Zivan to program in the charge curve I want, I'd be set.


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## JRP3 (Mar 7, 2008)

GizmoEV said:


> Jack's method would require Ah counting out and in, temperature monitoring, dv/dt monitoring, and the intelligence in the whole system to automatically do what he did manually.


I think all it would take is CC to a preset voltage then CV down to 0 amps. Chargers can do what he did manually, though not at 200 amps of course. I think he just used such a high amperage so it didn't end up being a 5 hour video


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## GizmoEV (Nov 28, 2009)

I didn't type what I meant to say. I meant to say to do what Jack was saying about charging at a high current until the cells were full or very nearly so and to let the voltage go as high as it wants.

The CC/CV charge profile is so easy I see no reason not to use it unless charge time is the issue.


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## Jan (Oct 5, 2009)

dimitri said:


> Its true that charging voltage in of itself is irrelevant and useless without reference to a current going thru a battery at the time said voltage measurement is taken. In fact, there is no difference between charger voltage and cell voltage since they are directly connected by thick wires and those voltages are always the same. So, amount of power flowing into the cell ( minus thermal losses ) is charging voltage times charging current...


OK. But that's not an answer to my question. You agree with Jack. 

That implies that Li-Ion batteries can be charged -theoreticaly- upto 80% in a few seconds. If you have enough amps and volts available. Which is just a matter of money.

Max amps is 3CA, but there is no max voltage mentioned. And you booth say it's no problem. So, at -let's say- 1000 volts and 300 amps, I can put 300 kW into just one 100ah battery. It has a capacity of 340wh. So it's charged in less than 4 seconds upto 80%. 

And if you have a charger that can reach 100,000 volts, you can charge a serious pack in a few seconds. 

That means there is no problem with charging along the road at long distances. It can be solved. Easy. 

But I don't believe that.


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## dimitri (May 16, 2008)

Jan said:


> Max amps is 3CA, but there is no max voltage mentioned. And you booth say it's no problem. So, at -let's say- 1000 volts and 300 amps, I can put 300 kW into just one 100ah battery. It has a capacity of 340wh. So it's charged in less than 4 seconds upto 80%.


You are forgetting Ohm's law. Voltage, Current and Internal Resistance are directly related. You cannot keep increasing voltage without increasing current and vice versa. So, since you have 3C limit from the specs you will stop raising current at 3C mark which will stop the voltage at some arbitrary point which will be constantly changing since Internal Resistance also changes as battery gets full. So implied 3C limit, which is likely due to thermal management is what limits your fast charging to 20 minutes.

Hope this makes sense.


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## Jan (Oct 5, 2009)

dimitri said:


> Hope this makes sense.


Yep. That makes sence.


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## Guest (Dec 24, 2009)

dimitri said:


> Jan,
> 
> I'm not sure how to respond to a video which insults the DIY community and well respected charger manufacturers with false statements and bits of information taken out of context, just to prove some obvious theoretical point, while confusing people in the process. So, at a risk of being accused of typing myself smart by someone who has no problems with videotaping himself smart on a weekly basis , I'll give it a shot.
> 
> ...


Dmitri, you are INDEED the poster child and I could do a dozen videos on what you absolutely know, and of course know wrong. That you are insulting about it doesn't bother me at all. You STILL, even after 103 minutes of the DMITRI show, don't understand the charge process.

If you CUT OFF the charger when the measured voltage REACHES 3.6 v, you don't HAVE a constant voltage charge phase. You just terminated it with your BMS.

Second, there IS a difference between the charge voltage and the measured voltage. If you could disconnect while charging, you would find the open loop voltage from your supply MUCH higher than the measured voltage or the cell voltage THAT'S WHAT CAUSES THE CURRENT. 

You have the battery voltage trying to force current one direction, and the supply trying to force current in the OTHER direction, and the amount of current into the cell is George Freakin Ohm's very deliberate function of the difference between the two.

But yes, if you put a multimeter on two ends of a 3/4 inch copper cable, it will read pretty much the same at both ends while it's charging because the entire drop is now the battery, which is absorbing power.

Yes, you could pulse charge, but it would take the rest of your life. It takes roughly 5-7 minutes for the surface charge to dissipate and the cell return to it's own voltage representative of state of charge. So the entire question of the manufacturers specified cc/cv curve is how to arrive at full charge, which can be measured at 3.4000 volts. IF you can picture this, and if you apply ANY current up to 3C until the measured voltage reaches 3.6 v, and if you then hold it there until current decreases to 0.05C, you will have arrived there safely.

On the other hand, if you charge to 3.6 v and cut it off when you reach there, you won't be anywhere particular. Just lost, dazed, and confused, and mildly angry at your favorite TV show.

So there is nothing wrong with the given charge curve, it's just not a religion. The cell isn't "fully charged at 3.6v", it's fully charged at 3.4 v. The 3.6 is ONE way to know how to get there with a CC/CV curve, but you DO have to do both parts of the curve.

How much energy goes in during each phase is kind of a function of the current used, so I can't say that you are only charging 80% or 60% or 94%, since I don't know what charger you are using or at what currrent.

In an interesting way, I am videotaping myself smart. Notice the meter leads and the meters. I learn something every day about these cells. But Brian is running the camera.

While you're "typing", you clearly aren't measuring anything, so how do you learn? By reading what you've typed. And since you typed it, you believe it. Maybe you could get Brian to type for you, and you could go measure something - while you're designing yourself smart and a lot of people broke on purchases of less than useful equipment.

Jack Rickard


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## Guest (Dec 24, 2009)

JRP3 said:


> I think all it would take is CC to a preset voltage then CV down to 0 amps. Chargers can do what he did manually, though not at 200 amps of course. I think he just used such a high amperage so it didn't end up being a 5 hour video


Precisely so. If you use a voltage detect to shut off when you REACH 3.6 your have just defeated the Zivan's constant voltage phase.

It IS true that you would not be leaving much on the table at 6 amps. But I happen to know that that is not the current the Zivan uses to charge cells - it's just another "typed" hypothetical red herring. 

Jack Rickard


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## Tesseract (Sep 27, 2008)

FWIW, my informal and thus far brief testing of single TS 200Ah cells confirms what Dimitri reports.

More specifically, when the LFP cell hits a certain level of charge (80%, 90%, who knows exactly), voltage starts to rise more rapidly for a given amount of charging current. Note the exact phrasing. You can essentially consider an LFP cell as having a very low, nearly constant internal resistance across the bulk of it's capacity range (say from 10% to 90% State of Charge, or SoC) which sharply rises at either end. This results in the cell voltage plummeting when it is almost flat and skyrocketing when it is almost full.

Temperature affects a cell in a similar fashion by not only increasing the effective internal resistance (e.g. - nearly doubling from the 20C value at -8C), but it also seems to decrease the chemical activity as the open circuit voltage is lower. In other words, the graph of voltage over time at a given constant current (whether charging or discharging) is not only shifted downward with temp, it is also sloped more (down if discharging; up if charging).

I did not watch the jrickard video in question, and likely will not, so I can't comment on it specifically.


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## Guest (Dec 24, 2009)

Jan said:


> OK. But that's not an answer to my question. You agree with Jack.
> 
> That implies that Li-Ion batteries can be charged -theoreticaly- upto 80% in a few seconds. If you have enough amps and volts available. Which is just a matter of money.
> 
> ...


And well you shouldn't. You don't get to pick the voltage and the current separately. They are kind of bound together by ohms law. You can change the voltage, to adjust the current, which is just what I did to GET 200 amps. But 3C is the given limit, and at that I'm told it reduces cycle life from the 3000 cycles to 2000 cycles, so there is SOME damage at 3C.

Picture 3.6 * 200 or 720 watts. And to do that at 130v is 26kW
.
Jack Rickard
http://evtv.me


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## dimitri (May 16, 2008)

Jack,

you don't know anything about me, so please stop making remarks about my knowledge or lack thereof. You are very delusional and hypocritical person, you think you are the only one who knows Ohm's law?

Here you go again taking bits of information out of context and turning it around to show your delusional superiority. Of course when supply is disconnected from load its voltage will be higher, do you really think everyone around you is a moron? The original poster wasn't asking what voltage will be after you disconnect supply from load. Why do you always insist on answering questions that no one is asking?

As for the product I am offering, no one has complained about my offers, I am not pushing anyone to buy anything. In fact I started the BMS poll because I was curious how many people believe in the crap that you were shoveling in your previous videos, and as it turns out that 40% of people didn't buy it, only 6% did. This goes against your recent blog post where you claim that entire DIY community followed you in 8 seconds, not true my delusional friend, not true.

I can argue that people are more likely to go broke following your videos than buying my product, let the time sort it out.

As for my typing, I hate to type, I much more prefer to read what people smarter than me typed. However, I am passionate about DIY EVs and want to help my fellow EVers. So I spend time answering questions to which I think I know the answers to, and when I am wrong I happily admit it or engage in intelligent conversation to prove my point. You should know, I tried several times to engage you in respectful intelligent conversations, but it was futile effort, since you are incapable of such communications. Your only response is arrogance and hypocracy.

I am very sorry that all forum members have to be exposed to this, but my reputation is important to me and I can't let some arrogant bully crap all over me on public record.


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## JRP3 (Mar 7, 2008)

Couldn't you use the HVC signal from the BMS to force the charger into CV mode through the regbus of a Manzanita? That way if one cell starts heading higher while still in CC mode the charger will start dropping current.


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## dimitri (May 16, 2008)

jrickard said:


> Precisely so. If you use a voltage detect to shut off when you REACH 3.6 your have just defeated the Zivan's constant voltage phase.
> 
> It IS true that you would not be leaving much on the table at 6 amps. But I happen to know that that is not the current the Zivan uses to charge cells - it's just another "typed" hypothetical red herring.
> 
> Jack Rickard


And again with false statements and hypocracy. First off, Zivan makes no secrets as you mention in your video, when you buy Zivan charger it comes with well documented charging curve and all currents and voltages in CC/CV profile are well documented, no need for any guessing. They only prevent you from changing it, but they hide nothing about it.

Second, Zivan's knee is 3.6V for Thundersy cells, and ther Um is 3.8V , so there is plenty of time for CV phase to go from 3.6V to 3.8V. CV phase current limit is also configurable with a rotary switch and can be set as low as 1 amp. In this case BMS would stop at 3.8V not 3.6V, get your facts straight.

When you order Zivan for SkyEnergy cell they should set the knee at 3.4-3.5V and Um at 3.6V , which would still allow CV phase to go happily and allow BMS to stop at 3.6V.

So, nothing is defeating CV phase, get your facts straight.


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## JRP3 (Mar 7, 2008)

Jack, I assume your purpose is to spread knowledge, so it might be better to avoid attacking the intelligence of your audience, unless you want your audience to consist of only those who agree with your every word. I happen to agree with much of what you say so I have no personal animosity towards you, but you seem to bring that out in others. It's not an effective way to communicate ideas, if that is your true intention.


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## Guest (Dec 24, 2009)

JRP3 said:


> Jack, I assume your purpose is to spread knowledge, so it might be better to avoid attacking the intelligence of your audience, unless you want your audience to consist of only those who agree with your every word. I happen to agree with much of what you say so I have no personal animosity towards you, but you seem to bring that out in others. It's not an effective way to communicate ideas, if that is your true intention.


The purpose is of course to share knowledge. My personal popularity is not particularly important. And it's kind of a case of if a shoe fits, wear it. And if not, there's not much to worry about. 

We're doing about 60,000 video views per month. Somebody is watching. And they're not all here on DIY. But there is a little club of guys desperately trying to bamboozle the EV community with this BMS nonsense. I'm not opposed to the concept, but the implementation has not only bilked hundreds of people out of some very pricey costs, but burned a few cars and cells to the ground. I think it's very important to debunk that and if a few of the BMS vendors, Dmiitri specifically, get quashed, I think that's a good thing.

Randy Holmquist told me they ordered 500 of the "volt blochers" this guy was selling and 26 of them tested bad - I personally lost a $110 cell just testing this thing. Without apology, he is off designing and offering ANOTHER blue elephant gun.

Prior to the show I attempted to discuss all this with him by private e-mail and explain the CC/CV curve in nearly a dozen messages. It doesn't fit his BMS plans, so he either can't get it or refuses to.

It's going to get worse. We're filming a series now putting the cells under load - 1C and 3C, and you will see rather graphically what I'm talking about, monitor for WHAT voltage and what are you going to do with the information.

If you want a way to monitor your cells, you can do it a LOT less expensively than giving this guy your money, and I am pretty certain at this point they will at least NOT hurt your car or your batteries. Hobby King has a rather cunning device termed a Cell Logger at $28.95 we've been discussing over on the Thundersky forum. I have some, and they are very interesting.

First, for $28.95 they will monitor 8 cells. That's $3.65 per cell, a bit more modestly priced. Second, they will display the voltages on a little screen.
Better, they LOG the cell voltages to a memory that can hold a couple of DAY's worth of driving. They provide a software program, that's independently available and somewhat popular, termed LogView that will allow you to download this data and GRAPH it on the PC. 

Why is this cool? Cell voltages are not actually terribly useful for a number of reasons. As to SOC, for the 80% you are actually going to USE they don't vary enough to be useful. But they DO vary quite considerably under various current loads. By graphing 8 cells together on the same screen, you can immediately see if one cell "stands out" from the others. This "relative" variance is VERY useful. In a normal pack, they'll all be doing more or less the same thing. If one isn't, it's a sign of pending trouble.

This device has an alarm that can be used precisely as Dmitri's terribly clumsy NC loop design. It can be set for HV or LV, which I again think is kind of not terribly useful. But it can ALSO be used for alarming voltage DIFFERENCE. Same concept. While we may not know what voltage a cell should be at at any given instant in dynamic operation, we DO know that they should all be at about the same state. Set it for a generous 0.2 volt difference, and I think you would have a useful indication of problem cells.

With the addition of some off the shelf relays, a totally isolated NC loop could be fashioned at a fraction of the cost, and you get the data logging as a bonus.

So yes, I'm on a bit of a mission to get you to stop spending cash money hard come by on snake oil and Blue Elephant guns that someone has assured you HAVE to spend or boy are you going to lose your $10,000 battery pack, and in the process selling you cheap hardware that will actually burn your car to the ground.

And yes, we're winning.

Am I likely to be voted most popular, pretty , and charming in Dmitri's self delusional poll? Would YOU think it was at all important if it were you?

If I measure carefully, believe the meters instead of my own bias, report the findings, and note products that are USEFUL and effective, we'll have a very good following. Along the way we'll step on a few toes. But it's not my first rodeo. We did this for Internet Service Providers for 12 years at Boardwatch. I never did earn a reputation as the most charming and poplar guy on the net. And I DID get it wrong occasionally. But I was known for putting out the info as honestly as possible, and we showed our work so anyone could do the same and draw whatever conclusions applied best to what they were doing, which sometimes varies quite a bit from what I think is important. And I was nearly famous for falling on my own sword when I did get it wrong and getting the word out about THAT as well.

If you're among the "online forum engineers" who sit around and type themselves smart, and you're offended, you are just going to become increasingly offended. I'm going to offend you right in your face until you quit shoveling BS and start reporting actual findings and data useful to the community. 

In the meantime, you can all vote me off the island if it makes you feel at all better. It won't slow the pace at EVTV Motor Verks at all. And my personal "popularity" is not even of consequence to ME, much less anybody else. This isn't Ivis in the Morning even if you are a bunch of nappy headed ho's. I would say at least my dog would love me, but I don't have a dog either now that I think of it.

Jack Rickard
http://evtv.me


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## EVComponents (Apr 20, 2009)

jrickard said:


> If you're among the "online forum engineers" who sit around and type themselves smart,


I love that line. It is a classic. 

Jack, your videos are well worth it. Keep documenting as much as you can. I am one of your 60,000 viewers.


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## dimitri (May 16, 2008)

Just to clarify yet another round of Jack's bullshit, I was never selling Volt Blochers, although I collaborated with Brian during initial design phase, but later we went in different directions.

I made MiniBMS an open source specifically to avoid hiding any potential design flaw and allow anyone to comment and engage in intelligent arguments. Many have engaged and helped to make it a better product. I made several attempts to engage Jack hoping that he would have some productive input, but he always refuses to answer simple and direct questions, instead he calls me a MORON every time and bashes me without any evidence in multiple places.

So far I spent hundreds of hours and thousands of dollars to help this community and have nothing to show in return, other than my family getting upset because of so much time spent helping people I never even met.

I price my work way below typical US standards because I know how difficult it is to spend hard earned money on gizmos you don't even understand. So I am trying to debunk the mystery around BMS and show that bench experiments are quite different from real life.

Again, I value my reputation more than money, so if anyone is not happy with me or my offers, please let me know and I will gladly close shop and stop spending time on forums.


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## EVComponents (Apr 20, 2009)

dimitri said:


> Again, I value my reputation more than money, so if anyone is not happy with me or my offers, please let me know and I will gladly close shop and stop spending time on forums.


Dimitri, I can completely respect what you are producing and the hard work that went into it. You should continue to sell it. Jack has a different opinion about the technology.

But if your customers want to buy your MiniBMS and it is worth it financially for you to produce, then you should definitely continue.


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## Jan (Oct 5, 2009)

I feel the spirit of Xmas in my topic.


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## TheSGC (Nov 15, 2007)

I have an observation to make to all:

I don't know Dimitri or Jack Richard at all, I don't now if they are Electrical Engineers or just EV hobbiest's, or what their professional education is.
What I do know is that I am an Electrical and Computer Engineering student, Junior year with a focus in electric vehicle technology, so this is meant to be as neutral as possible:

From an Electrical Engineering perspective, there is nothing wrong with the circuit design of the MiniBMS. All the components are properly spec'ed out and derated, the Shunting setup will ONLY allow 0.76-0.8 AMPs to pass through, depending at the set shunt voltage, well within it's 5 watt thermal limit and not a fire hazard. So if it kicks in when pumping 10 AMPs into the batteries, the shunt will consume 0.76-0.8 AMPs while the rest will go into the batteries, SLOWING down the power going into that one cell compared to the others. Even if the shunting voltage is exceeded, this is still enough derating to prevent problems to the MiniBMS. Yes, there is a point that the voltage could get past the MiniBMS ratings, but at that point you battery has probably exploded, or has been so seriously overcharged that it's no longer useful.

As for the balancer draining a cell to dead, of course it possible. That is possible, and has the same chance as your controller exploding, motor grenading or charger given out. Defective parts do bad things, and stuff happens.

There are people who agree and disagree about shunting technology, so we don't need any bashing here, or anywhere. If someone has another type of design, there are welcome to it without causing ruckus. Dimitri has kindly asked for constructive input in the design of this particular BMS and he has received it. 

And on the topic of charging a cell at High Voltage, yes it is possible IF you have the power supply/charger shutdown once your cell reaches the MAX charge voltage recommended by the manufacturer. I have not been able to find the proper CC/CV graphs but what I have read from the TS data sheets is that damage will be incurred if the Cell is brought above 4.25 volts, period. At that point CC/CV is irrelevant as the increased voltage will start to degrade and damage the battery chemistry.

Everybody have a good holiday and build some more EVs!


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## GizmoEV (Nov 28, 2009)

jrickard said:


> It IS true that you would not be leaving much on the table at 6 amps. But I happen to know that that is not the current the Zivan uses to charge cells - it's just another "typed" hypothetical red herring.


So you jump to a conclusion and assume that the 6 amps was not measured? I have three Zivan chargers. Two NG-1s and an NG-3. All three of them end with a 6A charge current at the end. Just because yours are programmed with a different profile doesn't mean the rest of them have exactly the same profile. I measured the current with both a shunt and a current sensor. If I changed jumper settings on the NG-3 I could get other finish current values, all higher. I haven't tried different jumper settings on the NG-1 yet.

Jack, for someone who appears to be trying to increase knowledge, you sure do a lot to discredit your self by verbally abusing everyone else who doesn't agree with you exactly. Your lack of language control and apparent lack of "I don't believe you because you didn't video it" attitude makes it difficult to extract the good information from your posts. Also, your statements which don't include the whole picture discredit your conclusions. Show what you are finding/measuring, keep experimenting, keep videoing, look for what is, regardless of whether it supports a particular position or not. It is clear you have a particular view and that you are out to support that view regardless of the evidence to the contrary.

David Nelson


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## EV-propulsion.com (Jun 1, 2009)

As an EV builder and supplier, building to "idiot proof" the vehicle is very important. If it can operate the same as an ICE vehicle without any different proceedures the better. Probably everyone here on the forum can understand and do what needs to be done to maintain their pack correctly. But, many people outside of here just want to drive an EV and don't have any basic knowledge of what is involved. Just turn the key and go. We all know this by the comments we all receive at shows, etc (but thats another thread..)
So what the miniBMS does is protect a large investment with the most important capability of the bms, the LVC, followed by the HVC in case of charger failure or tampering or voltage mis-match. Shunting of course is debatable still, but a small amount won't hurt. 
Basically, as stated previously throughout this forum, at it's minimum it is a necessary safety device for the un-informed lurking in the background until it is needed.
Everyone, enjoy the holidays!
Mike
www.EV-propulsion.com


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## EV-propulsion.com (Jun 1, 2009)

Dimitri,
keep up the good work of a solid, simple effective design-really just all we need for protection at a low cost too !
Mike
www.EV-propulsion.com


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