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Discussion Starter #221
my contribution to thread Building a LTO Grid Charger:
I like using the OE LTO BMS boards because I believe the readings to be accurate.
Just to get people on the same 'definition' page, a single board monitors 12 cells called a Block. A 72-cell pack is ~180v and has six blocks.
With a total pack voltage of 176.8V I noticed one of my blocks had a considerably lower voltage than the other five. The delta between hi/lo voltage for the cells of a 'good' block was 4mV; the delta for the wondering block was 42mV.
I decided to use my 180V grid charger, Peter's simple Cycler, and monitored total LTO pack voltage and stopped at 183.7V., I figured an average 2.55V/cell was ok.
What I found was the block total voltages raised pretty evenly but did not level or balance the individual cells. The delta between hi/lo cell voltages for 5 blocks, raised, in mV, 4, 3, 3, 1, 6. The delta between hi/lo cell voltages for the 'wondering' block raised 61 mV.
So that attempt to level or balance didn't go as I'd hoped. Clearly I have an issue with one block.
To try to level/balance all blocks I used my 'Level' tool consisting of high power resistors of 25 ohm (2 each) and one 500 ohm resistor. ( Post #218). I have very fine voltage-reducing control with the 500 ohm and gross control with a 25 ohm resistor, and medium-gross with 50 ohms. Today I reduced all blocks to within 10mV, monitoring using my DMM. Tomorrow I'll get more info after I read the BMS blocks.
I'm considering modifying Peter's Simple Cycler to a 30V charger using a Mean Well LPF-16-30 (cc/cv) because I believe a cv of 30V is necessary.
So for now I'm attempting to level my packs using my 'tool'. Hopefully in the future I can figure out how the Mean Well 16-30 can be used.

So here's what happened:

A weird thing happened after I connected the batteries and started the car to check voltages. I reset everything so I had no SOC display, but the 3 charge bars were on as it high-idled. Before I started the car my total pack voltage was 183.6; after several minutes of internal charging it raised to 187.8, then after several minutes the voltage went to 189.3. That's when I shut down. That's pretty phenomenal. Didn’t want it to go that high, ever. So now I’m doing a discharge to 30.2V/block or 181.2V total.

My chart includes my original data before I started any charging; after a charge; and after a discharge. The overall results shows some improvement but not like a true cell-by-cell balance.
EDIT: I had removed the BMS Interceptor. After discharging I'll but it back into the circuit.
 

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Discussion Starter #222
@retepsnikrep is it normal that when my Interceptor is not used and the BMS is reset by pulling a fuse that the car charges the pack until the SOC gauge reaches its appropriate level? When I reinstall the Interceptor will the car charge the pack since the Interceptor makes the SOC gauge to to 19 bars? Can you briefly explain?

Can you tell me what the OBD2C&C Menu item "Mdm VComp Val" does? At one time I inserted a value so BVO read my battery pack 'correctly'. I read in the manual that this value affects the Vpin voltage. Does the "Mdm VComp Val" only make BVO look 'different' or does it do something else too? With an LTO pack of 180+V should that be adjusted to a specific value? Thanks
 

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@retepsnikrep is it normal that when my Interceptor is not used and the BMS is reset by pulling a fuse that the car charges the pack until the SOC gauge reaches its appropriate level? When I reinstall the Interceptor will the car charge the pack since the Interceptor makes the SOC gauge to to 19 bars? Can you briefly explain?
If you have a BCM Interceptor then it won't do the BCM reset charge. (If you don't it will)

But you can can cancel that charge by using the OBDIIC&C to set the SOC at 75%

Can you tell me what the OBD2C&C Menu item "Mdm VComp Val" does? At one time I inserted a value so BVO read my battery pack 'correctly'. I read in the manual that this value affects the Vpin voltage. Does the "Mdm VComp Val" only make BVO look 'different' or does it do something else too? With an LTO pack of 180+V should that be adjusted to a specific value? Thanks
It adds a correction factor to the MDM VPIN displayed voltage. 'Mdv' and the 'Bvo'

I don't use it and it's likely to be removed or changed in future updates to make way for other LTO functions.

It's better to see what the car is actually reporting rather than this fudged value.

It should be set to 10 Decimal for no effect or compensation..
 

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Discussion Starter #224 (Edited)
9 days ago I went over a big pot hole and my car stopped. In the end what I found was my pack was not balanced very well despite a feeble attempt to charge/level it.
I have one errant 12-cell pack that changed quite a bit over several months so its average voltage was 0.40 V lower than the highest 12-pack. So I charged the 72-cell pack and the trouble started. The errant 12-pack was now 0.52 V lower. That's when the big bump stopped everything.
I ended up lowering-leveling each 12-cell pack to the same voltage, +/- 0.005V using my 'level tool'. The errant 12-pack still has issues but for the moment things are under control. I will be replacing that pack with another one from Greenpac.

I was surprised to learn what a difference an 'unbalanced' pack can make. The car didn't even want to start, my EDIT: Interceptor didn't work and my CANBUS didn't work because the 12V supply voltage from the BMS stopped.

This is a chart for the before charge, the charge, and the leveled packs. Pack 0 & 1 will be getting replaced so I left their data out in one chart.

86240
 

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I was surprised to learn what a difference an 'unbalanced' pack can make. The car didn't even want to start, my Interrupter didn't work and my CANBUS didn't work because the 12V supply voltage from the BMS stopped.
Can you elaborate on all this?
What's an interrupter?
 

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Discussion Starter #226 (Edited)
The Mini Interceptor and the Fooler seems to be in the spotlight lately, I believe because some people have included one or both with their LTO conversion, and some people use a pre-resistor and others may not. It can be confusing to ask and answer questions unless the setup is known.

I have the pre-resistor and 190V software in my Interceptor. From the beginning my dash has shown Regen with the battery voltage at 182V, whereas other members it doesn't. Is the charging the expected behavior when using the pre-resistor?

I've been having problems with my IMA going on frequently. My pack is relatively balanced but there is a 12-cell pack that's 50-60 mV out. I also had the OBD2C&C Current hack set to 166, although I never 'hammer down'. The IMA will reset after the car is off for 20 seconds. Sometimes if I try to start the car too quickly the only (easiest) way to recover is to pull the 30A fuse under the hood.
Can you give me a quick run-down as to what can be setting the IMA light. Thanks
 

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Discussion Starter #228

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Discussion Starter #230
My problems occur when I'm on the road and the only way to clear the IMA code is to reset by pulling the fuse under the hood. The CEL codes include P1585, P1649 and P1440.
I leveled my new pack using the power supply and it works like a charm. I anticipate the lights will go away.
 

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Discussion Starter #231
Just got the new pack installed. I topped them all to the same level. Car starts... that's good for me. However I continue to have an Alf flag. It cancels but immediately comes back just as quickly. I'd just as well turn it off, but I think it's telling me something. Also my OBD2C&C is not reading my LTO BCM cell voltages through the CAN BUS even though nothing was changed. I see it counting with the red blinking LED. Are the two related or is that noise on the CAN BUS?
Slf Flag.jpg
 

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What is/are the ID's of the new pack?

Have you amended the block ID's in the menu to account for the new block/s and the ones you removed.
 

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Discussion Starter #233
the same BCMs or the same Block IDs are being used. I think I found that 12V is not present.
What about the Alf flags?
 

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The flags are being set because the CAN is not working, therefore the voltages are below the minimums.
 

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Discussion Starter #236 (Edited)
My biggest and most inconvenient issue is the IMA and CEL light. The darn IMA & CEL come on occasionally and it's darn inconvenient! The car has to be turned off until the last relay resets before the car can be restarted (IMA off) and the CEL can be turned off by the OBD2C&C. If I try to start too soon, before relay resets, the car will not EVER start and gives no indication of starting, not even with the 12V. I have to pull the fuse under the hood to reset everything. This set of circumstances is always initiated when I'm in-town driving, usually going from 3rd-2nd or 3rd-1st, and an event happens like a reverse spike or quick drag on the drivetrain which activates the battery charging function, like 'popping' the clutch too quickly, same effect on charging function. This week I removed the rear harness and re-soldered or checked every add-on connection I've made for the LTO conversion so I'm confident they are all good. I know you'll want to know P-code but I don't have it now. a 1440? or a 15xx. Whatever it is it always seems to get triggered by an 'event', not driving on the highway.
EDIT: exact P-codes to come

My LTO pack voltage seems to be declining from 183V, even though the Charge bars light and regenerative braking functions well. I remember jime mentioning his battery voltage reducing to at or below 170V before he would get regen, but I'm already getting recharge bars. After some driving my pack voltage is down to ~173-ish. Is there a pack voltage that will be maintained once I reach a lower number?
 

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1) I do want the P/IMA code we can't diagnose properly without it.

2) Your average LTO pack voltage depends on a number of factors, including...
How much assist v regen you use.
They will find a natural point that depends on your driving style, terrain, routes and setup.
You have a 72 cell system with pre resistors,
so it also depends on what the car thinks the voltage is (Bvo) not what (Ltp) says.
Parameters or components might need tweaking to encourage more regen and less assist etc etc etc.
 

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Discussion Starter #238
that's my point, I don't have to encourage or discourage Regen or Assist with pack voltage ~175. What prevents the pack total voltage from staying relatively the same? Although the total pack voltage has been decreasing it hasn't gotten to 170V. I think jime mentioned was his threshold before his assist/Regen to worked.

I now see when my IMA and CEL both light they are telling me two different things; today the IMA light only went on but I still has assist and regen capability; when they both go off (seemingly frequently) I lose that capacity. I’ll get those P-codes when they happen. I believe tyhe MCM mod you just posted will mitigate the IMA from lighting. We'll see.
 

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that's my point, I don't have to encourage or discourage Regen or Assist with pack voltage ~175. What prevents the pack total voltage from staying relatively the same? Although the total pack voltage has been decreasing it hasn't gotten to 170V. I think jime mentioned was his threshold before his assist/Regen to worked.
I don't have the two pre resistors installed, but I never reach an equilibrium voltage where the Vbo will sustain itself with regen. I do get lots of regen, and the battery voltage drops slowly over time and driving cycles, but NEVER stabalizes. I've occasionally watched Vbo drop all way to 144V(2.0V/cell) and it never stabalized.

I do start to see regen resume when the battery voltage drops to approx. 175V. Above that, I don't get regen at all. It concerned me when I first did my conversion, but as Peter explained, it is pretty much normal.

I think that with the 10K pre resistors, the regen/assist balance "might" occur before reaching 144V, or it might require 20K????

Even with the 72 cell configuration, the nominal operating range of the pack is somewhat above the nominal, i.e. stable, operating range of the OEM NiMH pack.

I just haven't gotten around to doing the pre resistors. I drive so little that I go months before the the pack needs to be topped off.
 
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