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^ The DCDC doesn't turn ON until after you start the car, though, so I think something a bit different is taking place... Or, I guess it's the same thing, just the sequence is different.
 

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eq1: Actually with the GRN/BLK cut the DC/DC turns on as soon as I put the key to ON position or before I start the car. This allows me to use the radio without the gas engine running.

I guess the issue is that if there is too high a battery charge rate, like pulling 50 amps from the DC/DC converter to charge the battery. Somehow this throws an error code with the GRN/BLK wire cut somehow.

The big question is why doesn't it do it if I disconnect the battery for 30 seconds and reset the error code, then start the car. It only does it after restarting the car after it was already started. Being that if I get the error code and I can always start the car normally by disconnecting the battery first, I'm just going to leave it how it is.

As long as I keep the voltage close to 14.2 volts, I seem to be fine. I don't think this is going to be an issue because now I will definitely use my small 12 volt DC/DC converter to keep the LTO pack always charged around 14 volts.
 

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eq1: Actually with the GRN/BLK cut the DC/DC turns on as soon as I put the key to ON position or before I start the car. This allows me to use the radio without the gas engine running.
Yeah, I know. I was describing the normal operation.

hmm... I think I get it. Peter is saying that the DCDC load at key-ON w/ GRN/BLK cut prevents MDM filter caps from charging properly - not high enough, not fast enough, etc. That would probably result in low voltage on the MDM side (or too slow). I was thinking the load on the pack might pull pack voltage down, i.e. low voltage on pack side triggers the code. That's probably not what's happening, as even a 50 amp load at 12V is small for your LTO cells - and that bit of text I posted says the difference has to be 37V or more. That's a huge difference.

So, I think when your 12V LTO battery isn't fully charged it sinks so much current so fast, interfering with charging of the filter caps, that voltage on the MDM side is too low or doesn't rise fast enough.

I'm no electronics expert, but the idea that one could probably finagle the bypass contactor power resistor size to alter the time it takes to charge the MDM filter caps crosses my mind. If the resistor resistance determines the rate under normal conditions, you could lower the resistance, for instance, to get the caps to charge faster... Just thinking out-loud...
 

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Would anyone know, I just cut the GRN/BLK wire and not the WHT/GRN wire.

My battery voltage is always 14.2 volts, it doesn't seem to change from that. I thought I would need to cut the WHT/GRN wire for that?

Or if you cut the GRN/BLK then you don't need to cut the WHT/GRN wire?
 

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^ As far as I know those are independent signals. Under the right conditions, you should see 12V system voltage drop... I guess I've never actually tested it though.

Try driving with headlights OFF for a period, go into auto-stop - as I recall there's very few times that the DCDC won't drop into low power mode at such a time... On the other hand, your LTO cells are probably so good that they could easily uphold 12V system voltage on their own, so the drop could be very small and you may not notice -- especially since you're floating the cells right around their nominal voltage.

If you have your IMA lid open, you can hear the DCDC do the switch - there's a distinct chirp-tick every time the DCDC toggles into and out of low power mode, it's hard to miss.
 

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We are going round in circles a bit here.

1) The ECM controls the wht/grn wire. If you cut this you get the higher voltage mode 100% of the time.
If you don't cut it the ECM may be commanding high output anyway. In the just started car scenario it's logical for the ecm & dc-dc to boost the 12v battery by commanding high output for a few minutes. Idle speed is higher for those first couple of minutes so some regen power will be available. The engine temp also affects dc-dc 12V output voltage.

2) The MCM controls the grn/blk wire dc-dc enable/disable wire. As stated if cut the dc-dc turns on immediately with the ign and the filter caps don't/might not charge correctly. Even a modest dc-dc load will seriously affect the cap charging speed. Now some codes don't throw the IMA light on the first drive cycle, it may take a couple before it says I've had enough of this and faults.

3) Lowering the bypass resistor value will stress the bypass contactor and alter the charging speed.
I don't recommend that. The MCM can be quite fussy about the capacitor charging.
Remember it expects no HV load apart from the filter caps when the ign is first turned on.

4) Your 14.2 volts could be accurate/inaccurate due to temperature or other circuit component tolerance variations.
I would not worry about it. My 12v battery hovers between 13.8 and 14V FWIW.
 

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Discussion Starter · #147 ·
Peter is nearly 100% correct about everything he says in #146.
Only thing I want to clarify is #2: The DCDC turns on ~500 ms after the first key on, but ONLY if the DCDC's internal logic capacitors were previously empty... this takes about 30 seconds after each key off event. The only reason I clarify this is that the DCDC won't affect the precharge circuit as long as it's turning on from 'cold' (i.e. key has been off for more than 30 seconds). When the DCDC is 'warm' (i.e. the key has been 'ON' within last 30 seconds, then the ~500 ms delay doesn't occur; the DCDC turns on immediately, which prevents the HV capacitors from charging with the specified time, hence the P___ contactor error code.

tl;dr: If the key has been 'OFF' for more than 30 seconds, then you won't get IMA light error for the failing contactor.
 

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Mudder are you saying that, even with my issue of getting p1445 codes when the DC/DC converter was charging the battery at 50 amps. I would not have gotten that code if I waited a minute between turning the key on and off?

One interesting thing about that is one time I unplugged my 12 volt to reset the code, but only waited only like 5-10 seconds to reset the code, and then when I went to restart my car right after I got the error again. Even though I completely unplugged my 12 volt battery to reset the code. Then I went and unplugged it longer and then it reset.
 

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I decided to check the parasitic load on my car. Its 6ma or .006 amps.

If my calculations are correct this means that it would take (.006 amps) (24hours) = .144 amp hours a day.
1 amp hour / .144 amp hours = 7 days.

This means that every 7 days my battery will lose 1 amp hour of capacity. Assuming the battery is charged around 11 amp hours, this would mean I could let my car sit for 2 months with it still above 2.00 volts per cell.

If I charged my battery fully, it would last about 126 days with that parasitic load. Since Lithium has a close to nothing self discharge, it would really last that long.

What does this mean for me? I really never have to worry about my LTO battery dropping enough to cause a 50 amp charge rate since my battery will always be close to the insights 14 volt DC/DC output. Assuming I drive the car once every 2 weeks.

 

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One issue that crossed my mind, with cutting GRN/BLK DCDC, that I'm unsure about, is this: Would load from DCDC at merely key-ON impact current sensor calibration similar to how having a grid charger hooked-up and running at key-ON does?

My understanding is that the 'current sensors' are zeroed-out or whatever at zero load at key-ON, and if you have a grid charger connected and charging, the calibration of those sensors will be off - because it will treat say a 350mA current as zero current thereafter, so 'counting current' will be inaccurate...
 

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I decided to check the parasitic load on my car. Its 6ma or .006 amps.

If my calculations are correct this means that it would take (.006 amps) (24hours) = .144 amp hours a day.
1 amp hour / .144 amp hours = 7 days.
Wow. That's a lot (more than I'd want currently from hardly driving during COVID-19).

Not to mention the discharge that normally occurs on the main 12V battery without the BLK/GRN mod. Starting batteries are made with really thin plates to provide a lot of surface area to maximize current during cold starts. But the thin plates erode and crumble when repeatedly charged and discharged this way.

Your battery may last longer than the car as long as it doesn't go out of balance. (do you have a balancer in mind for that?)

It would be interesting to know the starter current after a deep cold soak in the dead of winter.
 

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It would be interesting to know the starter current after a deep cold soak in the dead of winter.
As I recall the starter motor is 1000W, so current will depend on how well the 12V battery can uphold voltage. I think my NiMH 12V battery was at something like 8V or 9V when starting once, 'cool' but not dead of winter cold. 1000W/8.5V=118 amps... I think Julian Edgar once reported he measured 130 amps.
 

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I measured 290 amps, this is probably a peak number, when starting my LTO pack which had a voltage at the time around 13.2 volts.

 

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Discussion Starter · #154 ·
One issue that crossed my mind, with cutting BLK/GRN DCDC, that I'm unsure about, is this: Would load from DCDC at merely key-ON impact current sensor calibration similar to how having a grid charger hooked-up and running at key-ON does?

My understanding is that the 'current sensors' are zeroed-out or whatever at zero load at key-ON, and if you have a grid charger connected and charging, the calibration of those sensors will be off - because it will treat say a 350mA current as zero current thereafter, so 'counting current' will be inaccurate...
Yes, but not when starting the car from 'cold'... at least not appreciably. Under normal use for the last few years, I've seen at most 100 mA error (versus a calibrated current probe I installed for my own purposes). Of course, even that 100 mA error will cause battery recalibration from time to time.

If starting from 'hot' (i.e. the key was 'ON', then 'OFF' for less than 30 seconds, then turned 'ON' again), then the calibration error would theoretically be severe, but the IMA system is disabled when the pre-charge relay fails to charge the caps in a sufficient amount of time.
 

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SO far with just the GRN/BLK wire cut. NOT the WHT/GRN.

I drove for almost 2 hours today, city and a little highway. My voltage stayed around 14.145 - 14.25 volts depending on if I was giving throttle or coasting.

It never once dropped below below that range. I did have the lights on.

I'm just not seeing this drop below 14 volts ever. Could it be the LTO modifications not letting it drop or the GRN/BLK being cut?
 

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^ Quick question - 14.145 - 14.25V - where/how are you measuring this? I measured carefully at the battery and the normal voltage always dropped to 13.85V, so, 14.1 or higher seems high to me. I saw 14.1 when the engine was stone cold, and it never lasted long...

-I don't think I've ever seen low power mode with headlights ON. And if it's in low power mode and you turn headlights ON, it will pop out of it.

I mentioned at some point that going into auto-stop with headlights OFF is usually a frequent, typical low power mode time. BUT, I realized like yesterday, that for the past couple years I've been running my pack at very low charge state, usually real charge state and generally nominal as well. You get low power mode much more frequently if the pack is 'low'. Not sure what determines 'low', maybe that QBatt signal. Just recently I've been driving at high charge state and I haven't seen low power mode as often, particularly in auto-stop. I do still see it though...

So, it's possible your IMA charge state could impact DCDC low power mode (LPM), but that depends on what signals you actually have left with your LTO setup. In general, higher charge state = less frequent LPM, low charge state=more frequent.
 

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Discussion Starter · #158 ·
If the headlights are on, the DCDC will NEVER drop to 12.x mode.
 

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One thing I noticed with cutting the GRN/BLK wire is that if you turn the key into the accessory position, or the position before the ON position. If you let it sit there for more than a couple of seconds, it will throw an IMA error code once you move the key to the ON position.

If you do this modification, you have to quickly turn the key from off to ON, and not stay on accessory for any length of time.

Another thing which mudder mentioned, which seems to be true, is that if you you do get an IMA light and wait over 30 seconds or so it will reset the code without having to unplug the battery.
 

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Would anyone know what would happen if you disconnect the 12 volt battery while the car is running? Would it still continue to run without the 12 volt battery?

I need to figure out if the car could be started by a 2nd DC/DC converter that replaced the 12 volt battery.
 
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