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Discussion Starter · #161 ·
Yes, the car will run with the 12 volt battery disconnected. I don't recommend this for safety reasons (e.g. airbags, ABS, etc won't work if the IMA disconnects).

I want to make it clear that I don't see any reason to cut the GRN/BLK wire in a vehicle with an even remotely healthy IMA battery. Cutting the GRN/BLK wire should only need to happen if you're stranded on the road with a dying 12 volt battery (i.e. because the IMA battery is in really bad shape).

Yes, you will get CEL if you turn the DCDC off and back on too rapidly. For example, this can happen when you turn the key off, wait for the IMA contactor to open, and then immediately turn the key back to on. You shouldn't see the CEL when you leave the key in the ON position, and then start it... of course, if you previously turned key off and then back on, that's probably what's actually setting the CEL you're seeing.

I do recommend cutting the WHT/GRN wire, as this ensures the DCDC always outputs 14.x volts when it is enabled.
 

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I did run my old Lithium Solarvan years ago without a 12V battery, it had a 15V 56F supercap instead.

IIRC It's dc-dc converter activated from a manual switch.
This charged up the 56F super capacitor in a few seconds which was the 12V battery.
That could store enough energy to supply stuff for a short time.

Get in flick switch, cap charges, by the time you get key in ignition and turn it cap is charged enough to operate contactors etc.

99% of the time the supcap was charged already from the previous drive,
unless you left the lights on etc.

The vehicle had no parasitic drain, alarms, memory backups etc etc.

If you have no 12V battery or permanent supply on the Insight all the computer modules will forget settings every night.
ECM, TCM, MCM, BCM etc etc Radio etc...

As John points out the Insight has lots of systems that won't like or be safe with no 12V battery.

Cutting the Grn/Blk wire also causes issues with some hacking mods...
 

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Thanks for the replies.

I agree with you, I would not recommend cutting the GRN/BLK wire either. Its a bit of a hassle with getting the check engine lights too easily, even if you are careful.

The reason I like cutting the GRN/BLK wire is that I can sit in the car and listen to the radio without the 12 volt battery dying. I don't really do that too often, but now I'm fixing up my car and I like to keep the radio on for hours while doing this. It is really nice having this option.

my insight would always give me a dead battery with like 10 minutes of listening to the radio.

What I am think is I'm going to put a 2nd DC/DC converter, 23 amps output constant current, in the car that has a mechanical switch to turn it on and off. This will act as a backup for things like my battery failing, the insight DC/DC converter failing. I could also use it when I want to run the radio and I would not even need to put the key to the ON position, I could put it on the accessory position. If I decide to sleep in the car with a cross country trip, I could run heated clothing from it since it gets very cold in the winter to sleep in the car and I don't have to run the car to stay warm.

It just has a lot of possibilities and relatability benefits for such a cheap price $80 to not add a 2nd DC/DC converter for backup. I could also easily put a low voltage cutoff to not over discharge my IMA pack.
 

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Discussion Starter · #164 ·
Why not just add an SPST switch to control whether the GRN/BLK wire is connected?
Fun fact to consider: If you move the DCDC's HVDC input to the battery side of the contactor, then you can turn the DCDC on whenever you want. This is a simple "remove one screw, attach another" modification. The DCDC pulls almost zero power (from 12V & IMA batteries) when the GRN/BLK wire is held low. When enabled (GRN/BLK high), but idle, the DCDC pulls 9 watts from the IMA battery.
 

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Thanks, good advice.

I thought about adding a switch to the GRN/BLK, but then I wouldn't have the 2nd DC/DC as a backup. I would also not be able to have the radio on by having the key in the ACC position.

I do not really want to mess around with the cars DC/DC converter too much. What happens if the IMA high voltage relay does not switch on to power the DC/DC converter? I also wouldn't have the 2nd DC/DC converter as a backup for anything that could go wrong with the cars DC/DC or how it gets its power from the IMA. There could be too many variables I am not familiar with that could give me issues.

The beauty of a 2nd DC/DC converter is that worse case scenario, you can push start the car and be able to drive the car or charge the battery with the DC/DC converter, or even without a battery. This would give me the ultimate in reliability. I've had so many issues with the 12 volt battery dying for so many reasons that I really would like a backup DC/DC converter for emergency use.

Thinking about it I may actually put a switch on that GRN/BLK wire and run it to the front of my car. I have cat 5 wire run to the front already that has spare wires I can connect to. This would allow me to get the full 50+ amps of the DC/DC converter if needed. For instances where I may want to keep the lights on for long periods of time with the car off. I wouldn't want to run that off my my 23 amp backup DC/DC converter, especially if I have the radio on at the same time.
 

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Discussion Starter · #166 ·
IMO there's zero reason to have a backup DCDC... that device is built by the best in the business (TDK Lambda) and simply doesn't break... ever. Given that the DCDC is rock-solid reliable, I don't see a reason to add a redundant one, but obviously it would work... it's just completely unnecessary. I'd be surprised if ANYONE has ever seen a broken DCDC.

In fact there is a way for you to have the radio on (and powered by DCDC) with just the key in the accessory position... you'd just need to switch the DCDC's logic power input (12 volts) to an always on location (there are several in the IMA bay).
 

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Hey guys, looking for any insight into placement of a low voltage cutoff device for the 12 volt battery I bought. I need to cut the main battery wire to the car, not the starter. There are two wires from the battery, one directly to the starter and one to the car.

I don't see any other way but to cut the wire at the location in the picture with the red arrow. Do you see any other place I may be able to put this small low voltage cutoff device or is that probably the best place?

Thanks




This is the small low voltage cutoff device that must be placed on the battery positive line.
 

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I have been keeping watch of the 12 volt battery voltage for a while now and came to the conclusion why the insight 12 volt battery may not last so long. I do not think its what some people claim that the insight keeps the 12 volt battery charged at too low of a voltage, this should not prematurely wear out the battery.

What is happening is the insight constantly changes the charge voltage of the 12 volt battery while driving, so it will jump from around 13 to 14 volts, pretty often.

What is happening is you are constantly cycling your 12 volt battery as it changes the voltage.

Optimally you would want the insight to stay at the same voltage and not have the 12 volt battery be used much at all while driving, that should lead to optimal battery life.

Best to cut the wires to force it to 14 volts all the time, or keep your lights on all the time.
 

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I wouldn't characterize DCDC behavior as you describe it - 'constantly jumping from around 13 to 14V'. When cold it's about 14.2V, it settles down to 13.85V once engine warms up, and then it drops to low power mode of about 12.2V 'at times', depending on stuff, like whether headlights are ON, how much stop and go you do, etc...

I don't know much about lead-acid batteries, but the above is the DCDC basic behavior. As I recall, from what others have said and when I looked it up once, lead acid needs to be charged pretty high most of the time, like 50% or less is bad, while the voltage at which it will be charged above about 50% is pretty high. As I recall 12.2V is low, I think below 50%, so if the type of driving you do results in more 'low power mode' more often than not, then I think that'd cause problems, premature degradation...

The duration of the toggles between DCDC normal power mode and low power mode seem pretty short-lived, I wouldn't think that would result in a lot of 'cycling', not with a big ~30Ah battery? But, over time, and depending on the type of driving, it could result in the battery tending to stay at a lower charge state than it should be kept most of the time...

Not sure though. I'm not really sure how lead acid voltage responds to current. IR is high, so the rate might be high for a brief blip, but otherwise would just slow to a crawl, I'd think. I guess the battery would see action, get some cycling - more than if voltage were fixed at say 13.85V. But, is that really bad for it, that bit of cycling?

Oh yeah, another thing: Do we really know that Insight 12V batteries suffer more than other cars? Anecdotally, we hear complaints seemingly often, but who really knows? There could be tons of things that factor-in to it. Most cars have CV of about 13.85V, and they also drop to lower voltage (my 1992 Previa van even does this). I don't see much that's different with the Insight 12V charge behavior, though perhaps it can dwell lower longer, and perhaps that low voltage cutoff is lower than other cars... Plus, the battery isn't used for starting... If there's a difference, that'd be my guess - the fact that it's not used for starting, while the batteries themselves are designed for starting, they're not 'deep cycle' types. Something in that vis-a-vis how it's used in Insight would probably be the difference.
 

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Discussion Starter · #170 · (Edited)
@insightbuyer. I disagree with your premise that 12.x mode isn't causing the problem, but agree with your conclusion: you should definitely cut the WHT/GRN wire going to the DCDC.

To your theory, I propose that it is in fact the 12.x volt condition that kills the battery. Keep in mind that 12.x volts isn't enough to charge a standard lead acid battery. In fact, when charged, a lead acid battery's resting voltage is 14.x volts at 90% SoC with ~C/10 charge rate. Therefore, when the ECM cycles the 12 volt rail down to 12.x volts, this causes the battery to discharge. Theoretically, at C/10 the battery can discharge all the way down to 15% SoC before it hits the DCDC's 12.x volt output... basically dead.

I say it's the 12.x volt condition that kills the battery, because the 14.x condition is always good for the battery, whereas the 12.x condition is not. It's not that the states change between the two values that kills the battery... it's that the 12.x state exists at all. If instead we shorted the WHT/GRN wire to ground, the battery would always be completely discharged... You probably couldn't turn the car back on after driving around in this condition for a few hours.

When the ECM brings the DCDC back up to 14.x mode, the battery recharges. Each time this cycle happens, the battery is discharged for a while, then recharged for a while. Since car lead acid batteries are not deep cycle by design, this causes severe plate wear. Without getting into the details, car starter batteries have spongy-like plates to maximize surface area. This allows insane impulse current, but also makes the batteries fail quickly when slowly discharged/charged.

So I propose the issue isn't the minor (temperature-controlled) voltage fluctuations when in the 14.x mode... because the battery stays charged in this state... all current is sourced from the DCDC. However, in 12.x mode, the DCDC isn't really doing anything until the battery voltage drops to 12.x volts. Under high load conditions, the DCDC would theoretically pick up the slack (as the voltage sagged under load). However, Honda prevents this from happening by always going back to 14.x volt mode when the current exceeds a certain threshold.

Overall, I think we're saying mostly the same thing. I'm just providing some clarification. based on my several year experiment, cutting the WHT/GRN wire is a night and day difference for battery life. Before I cut that wire, my 2 Ah 12 volt battery would always be dead after driving around town... not even enough juice to flick over the IMA relays (and thus power 12V with IMA battery). After cutting that wire, my 2 Ah battery remains charged and can always get the IMA battery going.
 

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Was just reading through this thread and realized there's no clear pic anywhere for the unassimilated....had my IMA compartment open and snapped one....correct me if I'm wrong...cut HERE where my finger is touching.


 

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^ Yes, but instead of cutting you can pull the terminal out of the connector. Seems 'cleaner' and more easily reversible.
 

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I cut mine after trying to figure out how to get that connector out safely, I could not get it out.

I would be careful here because if you mess up that connector trying to get it out, then you may not have good contact if you want to put the car back to normal.

This actually happened to me when trying to fix the driver side window, I was messing around with the pins and it didn't make good contact after I put the connector back in. I had issues and thought it was the passenger side motor and wasted time diagnosing the issue.
 

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^ I don't know, I had no problem getting that terminal out, I don't recall it being a big mystery. To each his own, I guess.
 

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I cut mine after trying to figure out how to get that connector out safely, I could not get it out.
My experience with these has been that there's a "tang" or "barb" on the metal insert to the plastic connector which prevents pullout. Obviously the tang, wherever it is, needs to be depressed to remove the insert, and suggests starting from the component, front, or business end of the connector and working towards the wiring.

Best experience, if the connector will permit it, is to insert a slightly oversized copy, if available, of the insert over the top of the insert. (I imagine such insert-removal tools exist.) However probing with a very thin flat-blade screwdriver will probably do it.

Incidentally, for those who must cut, consider using a 2-pair "Euro-style" plastic terminal block, to ease reconnection later; after cutting, connect the two ends to different terminals of the block. Reconnection is left as an exercise for the reader.
 
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