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I'm going to think once you hit the low voltage it switches off the IMA battery pack via the relay.

Since the car gas engine is not running and sending power to the DC/DC converter, there is possibly no way to power the DC/DC converter, so you will not charge your 12 volt battery pack.

I don't know, but that is probably the reason.
 

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^ That's about what I was saying. I think it has to be a bit more than 'low voltage' though, like it's either low voltage (at tap level) + conditions, or slope detection, etc. Otherwise, you'd have the pack disabling under all sorts of normal driving circumstances - where 'low voltage' per se is perfectly allowed, for example, ~12V at tap level under heavy load.
 

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Various things can disable the DC-DC.

1) The ign switched 12V power to it is cut.
2) The Grn/Black wire is intact and the MCM says DC off and pulls the line low.
3) The engine is off and the HV contactor is disengaged. (Ign may be on) It can't work without a HV power source
4) The HV input voltage falls below the dc-dc operating threshold. (That's about 70/80V or so, so very low)
5) Blown HV input fuse.
6) Internal overheating.

If you have a car sitting ign on feeding the dc-dc from the pack and you have cut the grn/blk, wire then the only way it can be disabled is 1,3,4,5,6.

The most likely scenario is 3. Caused by the MCM disengaging the HV contactor due to low pack voltage or imbalanced tap voltage signals from the BCM.

Even a BCM fooler can give unbalanced tap voltages if not made with at least 0.1% precision resistors.
1% resistors if badly matched can give a couple of hundred millivolts of imbalance.
 

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^ I don't think it'd be "imbalanced tap voltage signals." Pretty sure imbalance doesn't become a problem until the imbalance is really extreme, like >1.2V and for a time duration. I've run my pack without issues with pretty imbalanced taps.
 

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I just killed my 12 volt battery by draining it down to 8 volts or even less yesterday. Not sure if the 22 amp charging did anything to it either. The battery is so bad that it doesn't really hold charge and quickly drops to 10 volts. I had to jump the car in the morning.

Was this battery on the way out, or did I kill it by draining it to 8 volts or possibly lower yesterday?

Anyway, I planned on converting my 12 volt to a 6 cell LTO pack and I guess this will force me to do it ASAP. I've had enough of this lead acid battery junk anyway, its worse than the NiMH.

I'm going to cut the Wht/Green wire and this will keep my LTO pack at 14.2 volts. Which is perfect for a 6 cell LTO pack.
 

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^ fyi, When I worked with the 12V and DCDC, I measured 13.85V at battery with wire cut (DVCT signal high). It will be a little higher when engine is stone cold, but will quickly revert to about 13.85V...

Here's a link to that work, with a list of PWM duties vs. output voltages: Mod to Adjust DCDC Converter Output Voltage

Your LTO cells have a nominal of 2.3V, right? Doesn't seem like 13.85V is high enough, with 6 cells... When I've charged my high power LTOs at 1C, which have a 2.4V nominal, they hit about 14% SoC at that nominal voltage. Floating at about 2.4V would add a little bit, but not much. 13.85V would be 2.31V per cell for the high energy cells. I wouldn't think they'd be charged much more than 20-25% if floated there... You think that's enough? Or maybe you've measured differently?

I'd think you'd want to 'float' at around 2.5V, if not a bit higher, like up to 2.60: 2.5V X 6 cells = 15V - you can get the DCDC to output 15V (15.1V), but that's probably not good for the 12V components. 2.5V X 5 cells = 12.5V - a little too low. 2.6V X 5 cells = 13V, also a little low...

2.4V X 6 cells=14.4V, 2.45V X 6 cells=14.7V...

6 cells at 2.4V I think would probably be the best option. I think that'd probably get you to about 60-70% SoC. You could do up to 14.5V, or 2.417V per cell... 2.4 would be a 30% PWM duty, 2.417V would be 10%, the highest voltage you can go with the DCDC without 'faulting' to 15.1V... Of course, you can see that you'd need to hack the DVCT line and mod DCDC output voltage...

hmm... Maybe the charge curves for the high power vs. high energy cells are more different than I realized. I'm looking at a high energy charge curve, and I'm seeing about 50% SoC, if not a little higher, at 2.3V nominal, 0.2C charge. So maybe 13.85V would be just fine - about 50-60% SoC, 10-12Ah usable capacity...
 

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Actually, I'm working on a special project here. I'm tired of constantly getting dead batteries in the insight, happened way too many times, tired of being stranded. I once got stranded in the middle of the new mexico desert.

What I intend to do is hook up a small DC/DC converter that will draw its power from my IMA battery. This will keep the charge level of my 6 cell LTO pack around 13.5 volts with a diode. This way if my LTO battery ever falls below 13.5 volts it will be charged by my DC/DC converter.

I will cut the DC/DC converter WHT/GRN wire so that my voltage output is around 14 volts, this will keep my LTO pack charged to 14 volts most of the time. This will keep it around 55-60% SOC, whish is perfect to be honest.

The reason why 50-60% is perfect is because you should not be drawing much power from the 12 volt pack as the DC/DC converter should mostly be powering everything, especially if you cut the wire so it stays on when the car is ON like in auto-stop.

The 50-60% is also good for long cycle and battery life, and also good for long term storage as if the car isn't being used.

To keep LTO pack from any kind of self discharge, or possible voltage drops of the pack if its not able to charge quickly enough to 14.2 volts, this is where the backup DC/DC converter will kick on and charge it to 13.5 volts, I could set this higher, but it has to be below the DC/DC converter output voltage.

With this perfect setup, I will never have another 12 volt dead battery again, I will never have to constantly replace the 12 volt battery. Since I have extra LTO cells laying around it will be very cheap to do the conversion, I just need to buy the mean well power supply.

I'm looking at a meanwell HRP-100-15 which is a 7 Amp constant current power supply and only $40 bucks.
 

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...With this perfect setup, I will never have another 12 volt dead battery again, I will never have to constantly replace the 12 volt battery. Since I have extra LTO cells laying around it will be very cheap to do the conversion...
Yeah, that's about the way I feel about my NiMH stick-based 12V. Even not-very-good sticks do the job, and I have plenty of those. So I'll never have to buy a lead acid 12V for this car again, and it's all free.
 

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The 12V is dying in my project car, and i'm coming around to the idea of changing it for a a few LTO Cells or a couple of 5 cell NIMH sticks.

That lead is really heavy..

In fact this might be todays project..
 

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^ Sounds like 6 of the Fit LTOs make a really nice 12V battery. If you have extras I think I'd recommend that. The NiMH sticks work, but unless they're good sticks, they can be weak for 12V starting if you ever need that. The total capacity is small - so to ensure that you've got enough charge it's best to use Civic sticks, which have a lower charge voltage than early Insight sticks, and/or hack the DVCT line and adjust DCDC output to about 14.2V (50% PWM). Which is to say, if you can do it with the LTOs by just bunging together a battery of 6 cells, seems like the better option.

I think the only thing NiMH sticks have going for them is that we usually have a bunch that would otherwise just end up in the rubbish heap.
 

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Big issue!

I replaced my 12 volt with a 6 cell LTO battery.

Every time I turn the car off and back on, after waiting as long as 30 seconds, the car will throw a P1445 error with the IMA light on. I then have to go and disconnect the battery to reset it.

However, if I unplug the battery and reset the error code, it will start fine, until I restart the car the next time.

Any idea why it would be doing this?

Here are some things to point out:
Battery voltage is now 13.XX volts resting voltage.

When the car starts, the LTO battery will draw or charge as much as 50 amps charging! This is with only a 1 volt differential between the DC/DC converter 14.1 volts and the batteries 13.1 volts resting.

The DC/DC converter puts out 14.1 volts stable.
 

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^ It sounds like the issue Peter mentioned earlier, when cutting the GRN/BLK DCDC wire, or something related... Maybe Peter will chime-in.

Here's some text for one of the P1445 codes, I think this is what he was talking about:

DTC P1445 (62): Bypass Contactor Problem

General Description

The high voltage contactor between the battery module (BM) and the motor power inverter (MPI) module is turned on to activate the integrated motor assist (IMA) system after turning the ignition switch on. Before turning the high voltage contactor on, the bypass contactor is turned on and the motor drive module (MDM) condenser is charged gradually by limited current that is determined by the bypass resistor. When the difference between the voltage on the MPI module side and the BM side is within a set range, the high voltage contactor is turned on, then the bypass contactor is turned off. If the difference between the voltage on the MPI module side and the BM side is out of a set range for a specified time period or more after the bypass contactor is turned on, a malfunction is detected and a DTC is stored.

Malfunction Threshold
The difference between the voltage on the MPI module side and the BM side is 37 V or more for at least 2 seconds after the bypass contactor is turned on.
 

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Interesting and I hope that is not the issue.

I never cut the WHT/GRN wire yet, but I do have the GRN/BLK cut.

I let my battery equalize with the DC/DC converter or when the charging rate was only 3 amps at 14.2 volts.

Now everything seems fine, but I would need more testing.

So is the issue the high charging rate? I noticed that when the battery charging dropped from 50 to 25 amps it still cause the p1445 error upon restarting the car. However, this 25 amps could have been higher once I turned the car off for 30 seconds and restarted it. I'm not sure if that is the issue and its just a thought.

Kind of bummed here until I figure this out. The only saving grace is that I put XT150 connectors on my battery and its very easy to disconnect it now.

 

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retepsnikrep: Not sure if you saw my previous message because we sent them at the same time.

It seems to be working fine now that my battery voltage and DC/DC converter output are much closer.

Why do you think I'm getting this issue, and if its working fine now do you suggest I still reconnect the grn/blk wire?
 

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So is the issue the high charging rate?
Not positive how these circuits interact, but my impression was that, with the GRN/BLK cut you now have a load - and at times a seemingly big one - that can pull the pack voltage down. Meanwhile, the voltage/measurement at the MPI goes unscathed, so it'd be high(er) while pack voltage would be lower, than normal... With GRN/BLK intact, there's no extra load on the pack, since the 12V is powered by the 12V battery alone...
 

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When you turn the car on the bypass contactor engages and charges up the big MDM capacitors via a resistor then turns on the main contactor after a few 100 ms.

The MCM then turns on the dc-dc.

If you cut the green/blk wire the MCM can't control the dc-dc, so it starts working straight away and the filter caps don't get charged properly or in the correct amount of time as the dc-dc is dragging them down.

Hence the bypass contactor code appears..
 
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