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There is probably an optimum voltage zone, but opinions will likely differ on what that might be..
If you don't use pre resistors with a 72 cell pack then it runs at a lower SOC and voltage than if you do.

Some people will want maximum available capacity for PHEV operation, so that means higher charged voltages.
Some will want simplicity and maybe slightly more longevity.
 

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The 72 cell setup without resistors seems the best and simplest solution at present.
I think that "simplest" may be in the eye of the user. The 72 w/o preresistors (which I ran for a long time) is fine, but the Bvo always trickled down over time and did not have enough regeneration and background charging to stay above the minimum of 144V. Therefore, it required periodic charging. For those who don't mind the periodic charging, that's fine and it is probably close to ideal for those who want a pseudo PHEV mode of operation.

By adding the 10K preresistors (10K fooler matrix), I have been able to get my Bvo to stabalize at around 154=156V, for the kind of driving that I do. I no longer have to grid charge, which is convenient to me. So maybe the answer on preresistors depends on what the owner is trying to accomplish?

Later: Posts crossed;)
 

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With those resting voltages, I can't say conclusively how much of a difference they make. I wouldn't want to keep the pack sitting long term above 2.4 volts. I also found that letting them drop between 1.5 and 2.0 volts is bad.

I would say, you want to try and keep the pack around 2.3 volts if you wanted optimal life. But again, not sure if it makes much of a difference.

If I remember correctly I think storing them at 2.1 volts seem to be optimal over say 2.2 volts. But the difference wasn't all that much if stored in a cool place.

I do know with regular lithium cells, there is a big difference in how the cells are stored long term. If you store them too high, they will lose capacity at a much higher percentage. Storing a lithium cell fully charged will take about 4% of its life a year. Storing it at 30% of capacity will reduce that to .5% a year. Temperature also plays a reasonable part and probably most of the capacity we will see is from the battery baking in the hot sun in the car. It is probably more important to store the car at lower voltages if its baking in the hot sun.

Another way to look at this is if you over charged a cell to 4 volts, you would probably kill its life. So charging to 2.6 while not as overcharged as 4 volts, is still going to be much harder on the cell than say 2.4 volts.

With that being said, I tend to keep my battery around 2.2 volts when not using the car or when I have it sitting, and only charge it to 2.45 volts before most trips.

The worst thing you could do is keep the battery fully charged. I cringe when I see people who do that and most people do that with all their batteries. I tell my father if he uses a cordless drill, to not charge it afterwards if he is not going to use it for a long time. Charging it to 100% and letting it sit will reduce capacity about 3-5% a year vs .5% if stored at a lower voltage on most lithium chemistries.
 

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Discussion Starter #344
My goal is to have the system charge my LTO pack as necessary so I won't need to grid charge it to attain lost voltage levels. I understand balance is important but I'm not talking about that. I would use a BCMI with newest code. I understand that when using a pre-resistor a Vpin resistor muzbe used. My question : with my type of use in mind is it necessary, or best, to use a pre-resistor and Vpin?
 

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Question if anyone can clarify:


My IMA battery cut out the DC/DC converter at 145 volts when I had the key in the ON position but the engine off. I have the wire cut so I can run it like this.

It was mentioned that the NiMH cuts off at 120 volts, but not sure if that is under load or resting.
 

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Discussion Starter #346
To monitor Vpin voltage the parameter is called MDM Voltage and the designation is Mdv. The decimal value is 5.
 

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Discussion Starter #347
ok, the Mdv reading is 0170. That doesn't look like the Vpin voltage. As a matter of fact I measured it and it was 3.599V Where exactly is MDM voltage taken from? What is a normal value?
 

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...Another way to look at this is if you over charged a cell to 4 volts, you would probably kill its life. So charging to 2.6 while not as overcharged as 4 volts, is still going to be much harder on the cell than say 2.4 volts...
fyi, apples and oranges: 4V is seriously overcharging, 2.6V is not overcharging at all, therefore the cell charged to 2.6V does not experience any of the harmful effects of overcharging that the cell charged to 4V does... If you were overcharging you would have to to see a higher voltage than 2.6V, i.e. the fact that the voltage is only 2.6V is a prima facie case that the cell is indeed not overcharging.
 

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Early on I didn't pay attention to background charging, but I noticed an MPG hit when I allowed that, so for the last few months I aggressively use my clutch switch to prevent it. Doing that, my voltage does slowly drop while driving it. I've seen it down to about 2.1 per cell as the lowest. But I plug it in almost every night to get it to about 2.4 and then It becomes a light PHEV. However, if I didn't aggressively try to prevent background charging, I think the voltage would be maintained around 160 or 161 which is around 2.2 per cell. If I get annoyed with using my clutch switch for a while I can report back whether or not the car keeps itself charged with background charging.

Note: I do not have BCM Interceptor installed
 

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ok, the Mdv reading is 0170. That doesn't look like the Vpin voltage. As a matter of fact I measured it and it was 3.599V Where exactly is MDM voltage taken from? What is a normal value?
The VPIN voltage is a safer isolated 0-5V representation of the full MDM voltage.

VPIN varies as the actual MDM voltage varies.

The MCM takes the VPIN voltage and scales it up internally to get the MDM voltage.
 

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Discussion Starter #351
Tonight I installed my hacked rear harness and my car works correctly! Still have the Fooler connected. Haven't driven it but started it several times. Sure feels good.
I removed the Vpin resistor. The harness has the wires to accept and power the BCMI as well as power my CAN bus.
I was using the Vpin along with the pre-resistor for several months until I began to have problems. Removing the Vpin and pre-resistor his is the only thing that's changed.
My last step, after a week's driving, is to install the BCM/MCM modules in the "hole" to see how the harness reacts to the stresses of being placed there.
 

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Discussion Starter #352
as part of my step-by-step process to assure my LTO conversion is working correctly I increased the current hack to 40%. I went for a short spin until the SCO gauge was 100%. Later this week I'm going to install the MCM and BCM modules into the "hole". My last step will be to connect the BCMI.
I seems as though my troubles went away when I removed the Vpin resistor. I can't say for sure if that caused my problems but it's hard to believe anything else was to blame.
 

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Discussion Starter #353
I decided to pull the bottom, left battery because it has the screws holding the case together that interfere with the two plugs/wires when I pull the BCM/MCM modules out. I had the top and bottom of the joint welded and I removed everything 'outside' the weld. Gives me lots of nice room with no possibility to damage the MCM wires.
20201105_154330-1.jpg 20201105_160418-1.jpg

I also decided to revert to the 20% current hack so as to keep my car more reliable.
 

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Discussion Starter #354
Since my car has been operating I've had issues with not having the ceiling to allow the regeneration to work all the time, or another way, the battery stays charged to the point that frequently I don't get regen. Sometimes I only get partial regen. I'm using a Fooler with 20k resistors and no additional external resistors, i.e. Vpin or external. I'm using the BCMI with the latest software BCMI_12F1840_LTO72C_0k_L145_H187_T25_261020_V1_M_QB. My LTO voltage runs between ~170-185 when the regen cuts off, and the SOC was 60-70. I had it set for 60 then changed it to 70 in hopes of providing more regen, but the pack voltage crept up to 177-ish. What options do I have available that would give me regen all or most of the time?
 

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I had the same issue with mine and even made a thread about it a while back. Its quite annoying.

The only way I solved this issue was disabling coast regen. Coast regen will always keep your battery fully charged.

You may be able to try and use the IMA Boost and current hack to help, but the current hack will also increase the coast regen amperage and will cause such a drag on the car that you will feel like you have a flat tire every time you are coasting.

The best thing to get rid of this issue is to disable the coast regen, but its not exactly easy thing to do. You would need the IMA Boost. I just love coasting without the coast regen.

You could of course be very vigilant and throw the car in neutral every time you remove your foot off the gas, but that is not something I'm going to do.
 

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If the car detects a resting or sustained low load battery voltage above about 175-180V volts or so then it will disable regen.

This is one of the points and purpose of the VPIN and BCM Fooler pre-resistors.
It moves the voltage seen by the car down so it allows regen.

The 72 Cell LTO block configuration works well but the voltage is a tad high for the Insight system.
So if you want regen at higher SOC (pack voltage) you need VPIN and BCM Fooler pre-resistors to bring it down a touch.

BCM Interceptor software etc makes no difference.
 

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retepsnikrep, but even if he moves the voltage down, will he not still have the same issue of the pack that continues to keep over charging?

I think the main cause of the issue is too much charging and too little discharging. The insight was built around NiMH which has a large self discharge, meaning it loses about 10% a week of capacity by just sitting. The NiMH is also probably a lot less inefficient.

What happens is the insight does not work well with an LTO pack which is highly efficient and doesn't self discharge.

The only way I solved this issue was by losing the coast regen. The Coast regen is actually something you do not want if you have an LTO setup, especially if you are grid charging the pack. You really do not want the car to start charging every time you take your foot off the gas. First its annoying, and 2nd its inefficient.

What he really needs is my modified IMA Boost, this would allow him to switch coast regen on and off. This would allow him to keep the Coast regen disabled and get a much nicer drivable car with no drag and better MPG, and then if he needs his battery to charge because he can not grid charge the car, then simply turn the coast regen back on and charge the battery back up by a flick of a switch.
 

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Ah i see. I misread/misunderstood that then?
I thought he wanted to continue charging and was being prevented from doing so by a high resting voltage....

If the pack is full, the pack is full and you don't want regen..
You will have to expend some energy to make space in the cells.

You can use an IMA Boost device to turn down regen a bit and turn up assist across the board.
After a bit of tweaking the system will find a new equilibrium.
 

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I read it that he doesn't have the ceiling, meaning his pack is at too high of a voltage most of the time. I had this same exact issue and even made the following thread.

I think the issue is worse if you drive inefficient by constantly speeding up and then taking your foot off the gas instead of holding a constant throttle speed.

In this thread you made the 2nd post, basically saying what I wrote in this thread. I think I learned the problem from your 2nd post and realized there wasn't much I could do about the issue unless I do things to limit charging and increase discharging of the pack.

You can read my thread from 2017 below about pretty much the same issue:

 

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Discussion Starter #360
"I read it that he doesn't have the ceiling, meaning his pack is at too high of a voltage most of the time. " that's correct, I want to use regen as often as possible to slow me down. I can always use the clutch or put trans in neutral to stop it.
So Peter, you're suggesting going back to the Vpin setup. I'm using 20k on my Fooler, what are the best value resistors to insert to accomplish lowering what my system sees? When that voltage is" lowered"will I have similar characteristics as with NiMH pack?
 
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