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Discussion Starter #381
My issue as I stated before is my regen braking is working inconsistently and I want it to work all the time. My driving style is not to 'hammer down' when driving around town to reduce pack voltage and I’m on highways a great deal of the time so I don’t get regen on exit ramps.

I’m trying to understand SOC and pack voltage with regard to regen so I can figure out a way to have regen available most of the time. Is this possible? How does the OE system manage regen with the NiMH?

@insightbuyer suggested the characteristics of LTO enables the pack to hold a charge longer and voltage does not bleed-down with LTO? I would suggest the OE design was for SOC to be held below 100 most of the time (regardless what the gauge indicates) to accommodate regen ‘all the time’ … correct??

QUESTION: I remember after a grid charge I would not get full regen; Does regen stop when SOC reaches its ceiling or when the voltage reaches a ceiling? As I ponder I think the NiMH pack has no real ceiling because it “burns-off” excess voltage… correct?

Currently my pack is 170-180V and during regen it reaches 185V, at which time the regen braking stops. Too frequently however I get little or no regen braking when the pack voltage is under 180V. My SOC has been either 65 or 70 as indicated by the OBD2C&C and the dash gauge being most all the way at the top. I’ve tried changing it to 40 or 60 but in a short time I haven’t seen a change.

QUESTION: does the OBD2C&C SOC options affect regen?

Vpin and pre-resistor

I'm trying to understanding how the Vpin and pre-resistor (I'll call them external resistors) will influence the system. These two external resistors work in unison to make the system see a lower voltage then the actual LTO pack has.

QUESTION: with regard to regen, has the relationship between pack voltage, real or fooled, and SOC changed when these external resistors are used?

I know Peter said when these external resistors are used the pack voltage must be monitored to assure it doesn't get over charged. I guess the pack will continue (try) to charge above my 185V even if it only sees 170V? @jime said his pack stabilized at a much lower level all by itself; I'm not sure if he was using the external resistors. What causes / allows his pack to stabilize at a different, lower nominal voltage?

Regardless of using the external resistors or not, is my only solution to occasionally reduce the pack voltage (if I want regen all the time) or install a Qbatt device and use Mode 2 or 3?
 

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^ Too many specific questions for me to tackle, but I can take a stab at the general topic...

The two or three main things that manage regen at the very top are nominal state of charge and resting and loaded tap voltages. I imagine you must have a fooler to spoof tap voltages, right? And then, do you have anything spoofing the total voltage? If your pack voltage is really 170-180V resting, and your tap voltages are just the typical voltage divider, then your taps would be 17-18V and you're at or over the 'regen disable' tap voltage threshold...

As far as I can tell, the BCM 'pos recals' - jumps to 75% or 81% nominal - when resting tap voltage is ~17V for at least some short duration (like 30 seconds). If you have a BCM that pos recals to 75% you can still invoke regen for another ~6 points or until the max thresholds are reached, whichever comes first. If you have one that pos recals to 81%, then regen is immediately disabled until a 12V drain drops SoC by about 5 points.

The max threshold, as far as I can tell, is 17.4V resting. Once a tap has a resting voltage of 17.4V - you're done, no regen. I don't think there's any duration on that one, or if there is it's very short, like a few seconds. I guess there must be some duration...

That's pretty much it. I would imagine that if you're not spoofing the total voltage via resistors on vpin and whatever, then you're simply hitting the BCM's tap voltage limits. Resetting nominal SoC with the OBDIIC&C would make no difference.

[edit] Let's see, I think I'd use the pos recal threshold to determine the appropriate scaling for vpin etc., i.e. you'd fool the BCM to pos recal when the voltage is right for your cells. So, for example, maybe you want to consider your pack full when a cell reaches 2.6V. If you have a 72 cell pack, the pack voltage would be 2.6 X 72 = 187.2V, divided by 10 spoofed taps = 18.72V -- too high for the BCM. You need to scale your pack voltage down by a factor of 17V (what I think is the pos recal voltage) / 18.72 = 0.908...

When your total pack voltage is, say, 190V, the BCM would see 190V X 0.908 = 172.5V

When your tap voltage is 15.12V, the BCM would see 15.12V X 0.908 = 13.73V. 15.12V is 2.1V cell value, probably about the lowest you'd go, the BCM wouldn't let you go quite that low with a spoof factor of 0.908, as 13.73V is below the BCM minimum of about 14.4V resting... Let's see, 14.4V X 1.092 = 15.72V - I think that's the lowest you could take your pack with a spoof factor of 0.908, that's 2.184V per cell...

I think this is the way one would do it... Something like that.
 

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minor, what BCM interceptor software are you using? I would not install any software that does any background charging until you figure out what is causing your issue.

How often are you having this problem, are you not able to regen sometimes, or most of the time?

If your regen is cutoff, your pack voltage should fall fast and you should get regen back quickly.

the stock NiMH pack was always in a discharging state, it also was probably not that efficient charging, the cells heated much quicker causing more waste. LTO cells are always cold and never seem to heat up. Honda designed the battery management to deal with the highly inefficient NiMH cells and my insight was always in a discharged state when using them.
 

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^ That's not true at all - the OEM NiMH cells, when they're in good shape, have a very very high coulombic efficiency - like >95%. They hardly heat at all. I actually calculate more like 99%, but that's so good, and it's based on the pack's current sensor, that I have to be skeptical.
 

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Discussion Starter #385
I'm using the latest BCMI software. I have no pre-resistor or Vpin. Regen stops when the pack voltage reaches (Peter's) predetermined value, seems to be 185V but I'll now check the high cell voltage (Lth). The figures I present come from the OBD2C&C, SOC and Ltp, which tracks 100% with my measurements of pack voltage.
The regen availability depends on how hard I accelerate. Unfortunately I'm more often on 55 mph roads or highways so the pack charges to a point that leaves me little or no regen available.
@insightbuyer I wasn't aware there was any BCMI software that does not background charge.
On my drive from Detroit Saturday in 45F ambient temperature the Bte (pack temperature) does not come off the (Peter's predetermined) peg. On a very warm day I've seen the Bte reach 97F. I'm driving back today, then again Thursday, so I'll check voltages and current charging on the highway.
 

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EQ1 Post 382 is basically the answer. (y)

You are hitting the OEM resting voltage limits around 175V.
The OEM setup will simply not allow regen if the detected pack V is above this.

Then when you are actually regening you are also hitting the BCM Interceptor voltage limits at 185V or so.

Adding resistors can bring the detected voltage down, it depends how high you want to push your real cell V.
185/72 = 2.57V per cell assuming they are perfectly balanced.

The BCM SOC also has an impact and if it reaches 80% that also disables regen.

Your terrain/driving style/journey etc etc is completely different to everyone else's.
So your IMA charge/assist usage profile is also different.

Simply put you need to use more assist to bring your pack down if you want room to regen with your present setup.

If you add resistors etc but don't change your IMA usage profile IMO you will simply move the problem higher up the voltage scale.
 

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Yup, its simply like calories in / calories out. Too many calories in and not enough calories out, you get fat.

Your battery is simply taking in too much regen and not using enough assist. I had the same exact issue with my pack.
It is highly unlikely your battery pack is background charging without bars, you should try and figure out if this is happening if you saw it happen at higher pack charge voltages.

The only easily workable solution is the IMA Boost, unless of course you want to drastically change your driving habits like flooring the car constantly on the highway and then putting the car in neutral. Or possibly using a a joystick to control the assist manually.
 

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^ That's not true at all - the OEM NiMH cells, when they're in good shape, have a very very high coulombic efficiency - like >95%. They hardly heat at all. I actually calculate more like 99%, but that's so good, and it's based on the pack's current sensor, that I have to be skeptical.
First you are comparing the NiMH pack of about 1KW to a 4KW LTO pack. When I ran a voltage sag test on my NiMH sticks vs LTO cells, it was like 2 volts NIMH sag vs .2 volts LTO sag, per 12 volts. The NiMH sagged about 10x more than my LTO pack at not a very high current. With less voltage sag, the insight will draw less current and less current losses.

The LTO is much more efficient, especially because we are talking 3x the capacity. The LTO is also more efficient at the same capacity.

The LTO packs are also much more efficient when charging. You can charge LTO packs at the same rate I believe as max discharge. The NiMH packs are rated at what half charge to discharge?

LTO also doesn't self discharge at the rate of over 10% per week.

I'm not sure how much this all matters, but it must have an impact. Even if NiMH seems good, we are talking about 3x more capacity to deal with the discharge and charge.
 

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It is highly unlikely your battery pack is background charging without bars, you should try and figure out if this is happening if you saw it happen at higher pack charge voltages.
I explained what's happening. It's not only NOT highly unlikely, it's the opposite - it's exactly what you'd expect to happen. They don't call it a "background" charge for nothing.
 

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Discussion Starter #390
I read the last responses and understand the LTO battery is like a person’s weight – too much in and not enough out. I thought I’d add some additional info I gained today and ask a two questions.

I drove a 300 mile trip today at 70mph, unless I stopped.

My System: 72 Cell LTO; 20k Fooler w/ no external resistors; BCMI w/ most current software
Terminology: LTO Average cell voltage (Lta); LTO Hi cell voltage (Lth); LTO pack voltage (Ltp); IMA Battery voltage (Bvo)
All values come from the OBD2C&C

My question:
  • What determines when background charging occurs and the rate of charge, i.e. 2A, 5A, or 11A? It seems as though Lta plays a part to stop background charging but I can’t correlate what starts it or what determines the charge rate. A recent reply stated it stops at 185V; is that Bvo?
  • Is a Qbatt gadget the only way to stop background charging? Can BCMI software deal with that?
This is what I observed:
  • Lta likes to stay around 2.443 (176V) during the drive
  • Background charging (no dash gauge visual) is cyclic and real, going as high as 11A
  • Lta during background charging reaches 2.495V (179V) with Lth 2.517. The Bvo is probably 185 but I didn’t monitor that value.
  • SOC was 65 the whole trip except at end when I got regen, the first time that lasted longer than 10 seconds, then SOC went to 70.
  • Typically no regen braking is available, or only for 10-ish seconds.
  • At the very end I got regen braking from 70mph to 35mph when Lta went to 2.515. Regen didn’t stop until I let up, (my Bulldog cruise control gives me control w/o using braking); SOC reached 70; regen would not come back.
 

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The background charge rate is basically dependent on engine load/tps etc.

Engine lightly loaded or going down slight incline = higher charge rate.
Engine more heavily loaded or going up slight incline = lower charge rate.

If the load is too high it will of course drop out of background charge and start assisting.

Background charging occurs when the ECM says give me some charging.
The ECM commands charging in response to QBATT SOC data in accordance with the ECM's own firmware settings.

QBATT data from the MCM to the ECM is based on SOC data that originates in the BCM.

The BCMI can modify QBATT data and that has been explained in the various threads and videos.

We could compile you a different version of the standard BCMI software that has the SOC fixed at 75% for a much wider range of pack voltages. The car should not background charge with the SOC at 75%. You could be the test guinea pig at no cost ;)

Finally as the Lithium pack is slightly more efficient than the old Nimh one, any excess charge v assist Honda might have built into the system to compensate for any Nimh loses would cause a gradual increase in Lithium SOC.
 

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If for some crazy reason your brake lamp fuse is blown and the brake lights don’t work the regen doesn’t work correctly. The quick check is to see if the horn works. If the horn doesn’t work, check the fuse. The horn and brake lamps share the same fuse.

Scott
 
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OK Try this..

This firmware for the BCMI sets the SOC at 75% anytime the 2 minute avg pack voltage is > 160V

75% SOC should certainly disable SOC related background charging, so your pack might back creep down.

It will only set to 80% and disable SOC related regen if the 2 minute average is > 185V

You may still have a problem with a high resting pack voltage stopping regen until your pack creeps down a bit.
 

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Ahhh, I kind of figured there was something with that background charging and the BCM Interceptor software Minor was using.

I am using the original version of the BCM interceptor software that sets the SOC all the time at 75%?? and that is why I never have any background charging. It will be interesting if that fixes his issue.

This setup is exactly what you need for an easy way to control your battery level of your pack, LOL.

Qbatt and IMA Boost both combined with a control panel to easily change settings.

I can do the following from the control panel:

Adjust assist strength
Adjust regen strength
Enable background charging
Disable Assist
Disable Regen
Enable Coast Regen
Disable Coast regen
Allow maximum assist or regen to 100% by pushing a button

 

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Discussion Starter #395
Thanks Peter, I'm excited to try it and I'll install it before I make the RT starting tomorrow. I'm a little confused about the 75% SOC you refer to that stops background charge. I set the SOC to 60 using the OBD2C&C and the display is 65 most of the time.
 

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75% SOC should def stop background regen unless the pack voltage is really low or something else weird is happening.

60 or 65% won't stop regen in some car/firmware revisions.

Anyway test it and report back. :)
 

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Discussion Starter #397
Are you saying the when using the BCMI and the latest software that the SOC reading on the OBD2C&C is meaningless and the OBD2C&C screen to change the SOC is not functional?
 

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Discussion Starter #398
@insightbuyer, when you say "I can do the following from the control panel" what panel are you referring to, OBD2C&C. I'd like to know more. Is this info in another thread?
 

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minor, what I did was build my own control panel to control the Qbatt and IMA Boost more easily. What I wanted to avoid was having the mess you see in the picture. This mess was only suppose to be temporary as I wanted to make sure everything worked, then I just never got around to tidying it up.

I finally have the time to work on these projects after my corona virus layoff, which I'm happy to have gotten layed off, as I finally have some time to do my projects and hobbies.

I intend to mount the control panel by hot gluing it to the console in front of the emergency brake lever. Then I will mount safely mount the Qbatt and IMA Boost under the dash someplace and safely away.

I like the IMA Boost because it offers easy control of assist and regen levels. I use my insight mostly as a PHEV and use max assist, but if I'm doing a long highway trip I turn down the assist on the highway, then usually turn it back up when I'm off the highway.
I also don't like coast regen because of the regen drag, especially with the current hack and 84 cells, and since I use my insight as a PHEV, turning off coast regen allows higher MPG.

You can see the mess in the picture is why I made the control pod. Normally I would have to reach down there and feel for the pots or buttons when making adjustments. I'm surprised I never broke or shorted anything.

The OBDIIC&C is the next thing I need to work on, I have just used that briefly to test.
 

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Discussion Starter #400
On the way to work this morning the system acted as requested; SOC indicated 75 and no background charging. We'll see how the trip to Chicago goes with respect to Lta and Ltp.
My drive to work begs the question: is it possible to have an active SOC similar to OE where all charging stops at point A and all background charging can actively be turned on and off? This might not work with our LTO. How did the Fit operate?
 
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