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Discussion Starter · #101 ·
what gauge wire is appropriate to connect the LTO battery backs in your LTO conversion?
mudder recommended 4AWG, which I used. It seems adequate since the voltage drop at 65A or so, on a warm day, is only about 2-3V, which is mostly due to internal resistance of the cells.
 

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Discussion Starter · #102 · (Edited)
I just recently added the 10K pre-resistors to my BCM fooler and to the Vpin line. I've been pleasantly surprised how nicely this mod " realigns" the operating range of the LTO pack with the range that the OEM wants to see to keep a good balance of assist/regen. Just driving modestly around town (old hypermiler) it looks like the necessity to recharge periodically is almost gone. The pack stabilizes very nicely at around 160-162V and doesn't trickle downward with time like it once did:)

I'm still on track to add the new revised BCM Interceptor as time permit me to read up on using the PIC programmer.
 

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Discussion Starter · #103 ·
Yesterday in conversation with klr3cyl, realized that there are only two possible mechanical configurations for a 72 cell pack if it is housed in the OEM IPU case, so it is a compromise between the advantages of one or the other - purely in the eyes of the owner. These two options are driven by the total width of two LTO packs placed side by side.

Configuration 1 is the Natalya configuration which has a hole in the right side of the IPU and allows the relay board to be mounted in the original position, providing for the shutoff safety on the main IMA switch.

Configuration 2, which I will vainly call the jime configuration in its various forms, retains the IPU case as original and moves the 2 LTO packs to the left by approximately 1 inch. This eliminates the safety feature of the small bolt interlock at the IPU switch, and requires a thin membrane insulator over the dc-dc converter cover.

Pretty sure that these are the only two basic options for a 72 cell pack using the OEM IPU.
 

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Discussion Starter · #104 · (Edited)
Been tinkering with the fooler and Vpin preresistors in attempt to get battery stabilization voltage a little higher. I seem to be at a rather tricky "edge" where I'm changing the stabilization voltage rather slowly. Currently have values at 10K + 2.2K. This seems to want to stabilize at battery voltage of 156-157V.

Current measured voltages are:
Battery:156.5V
OBDII C&C:156V
Fooler: 139.5V

I'm a little surprised with the fooler at 139.5V that I don't get more background charging. I did about 50 miles expressway and saw very little background charging. Going to do some suburban driving tomorrow and see if the assist/regen balance will up the battery voltage. Would like to see stabilization at 160-165V.

I'm kinda tempted to go to 20K.
 
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Discussion Starter · #106 ·
Yes. It is still running the original s/w from a couple of years ago. I also have on hand a second Interceptor, and the upgrade PIC chip.

I have been slow to make changes, because I've found a new layout which will give me more space, but tinkering with the pre-resistors is easy. I have a bit of free time at the moment:)
 

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Discussion Starter · #108 ·
The OBDII C&C reports 75% SOC and does not vary. I thought this was true of all the "original" Interceptors.
 

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Currently have values at 10K + 2.2K.
Sorry I missed this. Please explain in more detail. :unsure:

Assuming your BCM Fooler is a 10 x 10k matrix, then the BCM Fooler pre-resistor and the vpin resistor must be the same value.

You also won't get any SOC related charging with the fixed SOC Interceptor.
The fixed 75% SOC is fighting your voltage modifying efforts.
 

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Discussion Starter · #110 ·
Sorry I missed this. Please explain in more detail. :unsure:

Assuming your BCM Fooler is a 10 x 10k matrix, then the BCM Fooler pre-resistor and the vpin resistor must be the same value.
Sorry to confuse:(

10K+2.2K just means that I added a 2.2k in series with both fooler and Vpin. Total of each is now 12.2K. I do understand that they both must be the same.

You also won't get any SOC related charging with the fixed SOC Interceptor.
The fixed 75% SOC is fighting your voltage modifying efforts.
OK, I'm a little confused. I thought that the two pre resistors were intended to modify what the BCM saw as the current IMA battery voltage, even if SOC was faked to 75%. Wasn't this the idea of adding pre-resistors?

I note that changing the values does seem to adjust the "stabilization" voltage. Adding the 2.2k "seemed" to move the pack voltage up from 154V to about 155-156V, but it might have been attributeible to the nature of the driving cycle, and not modification of the assist/regen balance.

I did notice that when I raced the engine in the driveway to about 3500RPM, the OBDII C&C showed charging at about 35A.
 

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Adding resistors does adjust the voltage the BCM sees.

But if it the BCM is changing the SOC to initiate charging you will never see it, as the BCM interceptor is overriding that data on it's way to the MCM and replacing whatever SOC the BCM is setting with the fixed 75%.

The ECM actually commands regen based on the QBATT PWM sent out by the MCM.
The MCM bases QBATT on the SOC data it gets from the BCM.

So QBATT is in effect at 75%, so no charging occurs except when coasting/braking/reving etc.

The fixed SOC 75% BCM Interceptor code is really for people who want to use the car as a PHEV and grid charge daily.
It's designed to stop all but coasting/braking regen. So you don't get hidden charging impacting mpg.

Later versions of the firmware have variable SOC based on two minute pack voltage averages.
Time to try on of those.
 

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The fixed SOC 75% BCM Interceptor code is really for people who want to use the car as a PHEV and grid charge daily.
It's designed to stop all but coasting/braking regen. So you don't get hidden charging impacting mpg.
I use the BCMI software that holds the SOC to 75% and I do not use a Vpin or a pre-resistor. I am really happy even though I don't treat my setup as a PHEV. It's great on the highway because it does not background charge, and I've found that in situations where there is more traffic and traffic lights the 75 SOC still works. It has to come down to driving style and 'accessories'. By accessories I mean the Bulldog Cruise Control that enables me to use regen as a braking tool rather than using the brakes. I would guess that I use the regen more than most people which keeps my pack topped-up to 169-ish V.
In the short turn my pack voltage has pretty much leveled at Lta = 2.357-ish (168-170 V). But again driving style. I'm thinking I have the option to reduce the pack voltage to 165V using resistance, but I'll have to wait and report back after more miles and time.
 

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Discussion Starter · #113 ·
Thanks.
Later versions of the firmware have variable SOC based on two minute pack voltage averages.
Time to try on of those.
Ok. I may get time to set up my second Interceptor and put it in. I'm not really strongly motivated since I'm changing the configuration anyway, but it would be valuable testing;)

There still seems to be some performance inconsistency with your explanation, but maybe I changed my driving style after I added the 10K preresistors.
 

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Yesterday in conversation with klr3cyl, realized that there are only two possible mechanical configurations for a 72 cell pack if it is housed in the OEM IPU case, so it is a compromise between the advantages of one or the other - purely in the eyes of the owner. These two options are driven by the total width of two LTO packs placed side by side.

Configuration 1 is the Natalya configuration which has a hole in the right side of the IPU and allows the relay board to be mounted in the original position, providing for the shutoff safety on the main IMA switch.

Configuration 2, which I will vainly call the jime configuration in its various forms, retains the IPU case as original and moves the 2 LTO packs to the left by approximately 1 inch. This eliminates the safety feature of the small bolt interlock at the IPU switch, and requires a thin membrane insulator over the dc-dc converter cover.

Pretty sure that these are the only two basic options for a 72 cell pack using the OEM IPU.
Just saw this post. I want to note my method also eliminates the small bolt interlock on the junction board at the IPU switch. The junction board is physically shifted left about an inch from the OEM position, but one can still get the OEM foam block that sits on top of the DC/DC converter to stay in place. I've used additional electrically insulating foam (which came with the LTO blocks as a packaging material) to keep the junction board from being able to touch the side of the DC/DC converter. The switch itself still sits underneath the cover, so you can access it normally.
 

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Discussion Starter · #115 ·
Brilliant is Quick, Dumb takes Longer. :D

The "balance" of total power changes as one runs the A/C a bunch. The car has to use more assist to climb grades or support higher gears because the ICE power is being "sapped" by the A/C power demands. I knew it, but I didn't realize it would change the voltage stabilization level of my pack. (Incidentally I am still running the original version of the interceptor with fixed 75% SOC - still trying to get time to upgrading a bunch of stuff). Now obvious - more A/c, more assist, more drain on my LTO pack - lower voltage needing more grid charging in summer.
 
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Discussion Starter · #117 ·
@jime for what it's worth I believe the 75% SOC prevents general background charging.
You may be right. Makes sense. Probably need to pay more attention to my C&C gauge. I haven't worried too much about what it is doing since I'm going to change it all anyway. ;)
 

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I'm really tempted to install BMS Interceptor to reduce bg charge in my car. I'm constantly having to defeat it with my clutch switch. I also fixed my A/C recently, so I've been using that and wow, it really gives a hit to the MPGs. I'm also running Vredestein Quattrac 5 tires for safety, but those sap MPGs too even at 62 PSI. I think I'm probably making the pack work harder than it ought to without a BMS.
 

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Discussion Starter · #119 ·
If you are getting enough charging to maintain the the pack voltage somewhere the "midrange" of 162V give or take, then you should be ok. The current draw, even with a 40% hack, shouldn't be more than 100A for a few seconds. I think I saw someone's calculations (Peter's??) somewhere, but thinking our current demands, even with the 40% hack, must not exceed those of the Fit electric under hard acceleration.

Do you use the clutch switch to, a. reduce the m[g hit from the background charging, or b. to avoid the battery charging to too high a voltage. I'd guess a. but which is it?

Are you targeting a particular operating voltage?

When I get to my new installation installed, I had thought of running the interceptor with the version of S/W which requires no charging, so maybe we are actually trying to do two different things. Actually now that my mind turns to it, I think I recall that you are charging regularly, so I guess you are attempting a PHEV mode. I "think" the PHEV version of the interceptor will give you a good shot at that.

I've got to go back and study the interceptor modes again. I have a tough time retaining all the technial detain in all this chaos at home. My brain has shrunk to much to keep track;)
 
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I also fixed my A/C recently, so I've been using that and wow, it really gives a hit to the MPGs
@Natalya I found that when on the highway using the AC 100% my mileage suffers 10-12%.
 
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