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Discussion Starter #1
Is it possible to use or modify the Insight's stock regenerative braking to charge the 12V battery without the IMA being installed?

If so, how? If not, why?

(Please don't turn this into a why-did-you-remove-the-IMA discussion).
 

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Yes it is,. There are MANY threads to that effect here at ICN.
Use the search function, top left of this page for best results.

HTH
Willie
 

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Discussion Starter #3
I think you may have confused my question. I wasn't asking about charging the 12V battery with the IMA disabled, but rather if some form of regenerative braking can be used to keep the 12V battery charged up, in addition to the DC-DC. Normally the regenerative braking charges the IMA battery, but with that being disabled/removed, regenerative braking goes away. My question was if it was possible to modify the Insight's regenerative braking to directly charge the 12V battery rather than the IMA. I did not find any threads addressing this in my search.
 

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Discussion Starter #5
No, you can't push enough power fast enough to do any kind of meaningful regen into an Insight's 12V lead battery.
Why not? If regenerative braking is sufficient for the high voltage IMA battery, why wouldn't it work for the much smaller 12V battery?
 

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No, you can't push enough power fast enough to do any kind of meaningful regen into an Insight's 12V lead battery.
Why not? If regenerative braking is sufficient for the high voltage IMA battery, why wouldn't it work for the much smaller 12V battery?
Maximum charge rate for a high quality lead acid is about 1C... Roughly 50 amps or 600 watts. Regen with the high voltage battery is more like 10,000 watts. If you went to all the trouble to engineer and program a system to accomplish what you are describing the net effect would be impossible to feel. A fool's errand.
 

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It has to do with the charge rate for lead acid battery chemistry. I don't know the exact numbers offhand but, lets say your 12V battery would accept a 50 amp charge rate. That's only 480 watts. While that is something, it's chump change compared to regular regen rates.

But lets talk about other problems.

You would need to solve the technical hurdles of actually being able to selectively discharge and charge your 12V battery. Assuming you did all that, you would then find your 12V battery doesn't appreciate all the abuse and it'll probably start failing in short order. There are more issues related charging leaded batteries in general, but this should be enough cold water for now.
 

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Discussion Starter #8
You both make points. It seems like what I am trying to accomplish can be easily accomplished through the IMA system "disabled" in a way. Correct me if I am wrong, but there are 5 things that the IMA does:
#1: Provides electric assist when demanded
#2: Regeneratively charges the battery upon braking
#3: Provides support to the DC-DC by keeping the 12V at a higher voltage when the DC-DC is in low-power mode.
#4: Takes a small trickle charge off the engine that doesn't show up on the charge display to make up for #3 (noticeable when the IMA bars slowly increase on highway drives with no IMA use. This is what I believe causes the IMA to reduce highway economy slightly).
#5: Does forced charge when the battery is low.

If this is the case, then using an IMA boost device or IMAC&C could disable all of the above but #3. This seems like it would result in the IMA slowly discharging as a slight drain is put upon it to aid the DC-DC in keeping the 12V at ~14V. Normally whenever more juice is demanded from the IMA to get the 12V charged back up, an increased load is put on the engine, which reduces fuel economy (something I experienced when doing extended EOC at night with the IMA enabled). However, with an IMA boost device or IMAC&C, all regen and assist could be disabled, and then regen could be applied to charge the IMA when braking to make up for the slight drain on it to keep the 12V charged.

Or am I misunderstanding this whole thing completely? This seems to follow what I experienced with the IMA enabled.

Tagging @retepsnikrep in case I am incorrectly describing how the IMA boost device or IMAC&C function.
 

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You are missing the point about charge rate. Lead acid doesn't like to be charged above a rate of about 1C, and that's only for the bulk stage. Topping the battery up to 100% takes much longer.

1C means a rate that is one times it's total capacity per hour. In real world terms, this means that if you had a lead battery at 40% state of charge, it will take 1/2 hour to charge it 50% to 90% SOC. Or in your case, you would need to brake for 30 minutes straight to charge it to 90%.

You can't charge a small lead acid battery fast enough to regen brake into it. This whole idea is, as ackattacker put it, a fool's errend.

Don't believe us? Read up on Mazda's i-ELOOP system. Instead abusing the lead acid battery, they are using super capacitors.
 

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As has been stated by others the lead acid battery can't accept the high regen rate provided by the ima system.

The IMA can provide 50A regen into 180V or so, so 9000w (9kw)

The 12v battery might if you are lucky, be able to accept 12v x 50A for short periods = 600w.

So you see they are not compatible by factor of at least 15 and that's discounting the technical hurdles required to make it possible.

In fact the 12v system can't take more than 6.66% of the available IMA power.

Of course you could limit power to 600w but then you would be wasting regen opportunities and power in your brakes.
 

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Discussion Starter #11
Is it really that complicated? My thoughts were that since the Insight already has a regenerative braking system set up, that it wouldn't hurt to simply step down the voltage on it and allow for some small charge to the 12V. Obviously the charge would be very little. I don't use my brakes much, but this would be a "tiny" savings at what I figured wouldn't be a too complicated modification -- simply reconfigure the Insight's stock regenerative braking toward the 12V, obviously stepping it down a bit. If it's too complicated then I won't bother, but I didn't think something like that would be that complicated since the Insight already comes with regenerative braking as OEM; it would just be modified, not built from scratch.
 

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Is it really that complicated? My thoughts were that since the Insight already has a regenerative braking system set up, that it wouldn't hurt to simply step down the voltage on it and allow for some small charge to the 12V.
Depending upon how you disabled your IMA system, isn't the IMA motor still being used as an alternator for charging the 12 volt battery using the DC-DC converter? If so the 12 volt battery and 12 volt system load are already using what power they require.

As others have pointed out you have to have a suitable load to dump the same amount of power that the IMA battery could handle to have the same amount of regenerative braking affect.

You need to find some other electrical load to dump the IMA motor output into when the brake lights are on. Maybe four 220Vac space heaters wired in series parallel & switched on with a heavy duty solid state switch?

Which of course creates another problem, what do you do with all that heat? :rolleyes:
 

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Is it really that complicated? My thoughts were that since the Insight already has a regenerative braking system set up, that it wouldn't hurt to simply step down the voltage on it and allow for some small charge to the 12V.
This is what the DCDC does... it steps down the high voltage BLAC motor's output voltage to either 12.x or 14.x volts (chosen by ECM).

It sounds like you're trying to replicate the system that's already back there.
 

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Is it really that complicated?
...simply step down the voltage on it...
...I figured wouldn't be a too complicated modification -- simply reconfigure...
...I didn't think something like that would be that complicated...
...it would just be modified...
I like your enthusiasm, but from your wording it's clear you don't really understand what goes into these electrical systems...

Electronics that have been designed specifically to charge a large, high-voltage battery cannot be "simply" modified. The circuitry cannot be adapted without significant redesign, rewiring, and modification. You wouldn't be able to use almost any of the stock circuitry.

In addition, it sounds like you're hoping to get back some regenerative braking, not just keep the 12V battery charged. As people have said, the 12V battery is not capable of taking that kind of charge.

When the car is regeneratively braking, all that inertia and kinetic energy (of the car moving forward) is being converted into electricity by the motor and forced into the battery. This is where that energy is actually "going" when your car is slowing down.
The high-voltage battery is designed to be capable of handling this amount of energy going into it in such a short amount of time. The 12V battery is not.
If you took the same amount of energy that normally goes into the IMA battery during regen and put it into the 12V battery, it would catch fire and/or explode.
So even if it were easy to convert the stock circuitry to charge the 12V battery directly, you would have reduce the amount of power going into it a lot. Less power into the battery means less power coming out of your car's kinetic energy, which means you won't slow down nearly as much. Your new regenerative braking would only be about 6% as effective as normal.

You would also need to ensure the battery is always nearly empty, so that it can take a charge on demand. But what if you park your car with the 12V battery depleted? You might not be able to start your car in the morning.

It's just not practical or useful. The DC/DC already does the job you're describing, and there's a reason you don't feel it slowing the car down. Because as stated above, the energy actually going into the 12V battery is insignificant.
 

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Discussion Starter #15
Good points. It does make sense that this would be a needless, useless, and complicated modification.

I suppose I am still trying to figure out whether to remove the IMA or use IMAC&C.

Depending upon how you disabled your IMA system, isn't the IMA motor still being used as an alternator for charging the 12 volt battery using the DC-DC converter? If so the 12 volt battery and 12 volt system load are already using what power they require.
This is what the DCDC does... it steps down the high voltage BLAC motor's output voltage to either 12.x or 14.x volts (chosen by ECM).

It sounds like you're trying to replicate the system that's already back there.
Yes, I probably was trying to replicate it. Actually more like aid it, but as seen this would be quite useless.

Even with my lighter electrical load on the car (LEDs, no AC), the DC-DC doesn't provide enough current to keep the 12V charged at my low RPM city driving if I do a lot of EOC or start/stop (i.e. pizza delivery runs). The starter is used multiple times and the RPMs are rarely high enough to get much decent charge. I can't imagine that cutting that one wire to keep the DC-DC in high power mode would help that much.

Yet if I kept the IMA I might kill the battery due to overheating it (no AC use) even if I used IMAC&C to reduce IMA use and extend the battery's useful life to me.

I like your enthusiasm, but from your wording it's clear you don't really understand what goes into these electrical systems...
This is true, hence my questions and desire to learn. :)
 

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I struggled pretty hard trying to understand this - I think I get it, now...

In essence, 'all' you want to be able to do is replace the energy going into the 12V battery that now comes from burning gasoline (ICE > IMA motor > DC-DC > 12V system/battery) - with kinetic energy via regenerative braking. You're not interested in regenerative braking per se; you're interested in charging your 12V from kinetic energy, perhaps only kinetic energy. Right?. And I think you're really interested in having ALL your 12V energy coming from regenerative braking, not just whatever the residual amount is needed to keep the 12V battery charged...

Pretty sure this is really what you're after, and I think this is a little different from what others have addressed, at least to a degree... And also, the crux here is that you want this without the IMA in place - the IMA that more or less already does this...

I think, in essence, what you need/want would be something akin to running the car off the 12V battery all the time - and only charging the battery when you're braking...

Would it be worth it, i.e. what's to be gained? Well, I don't have the patience to do all the math, but back of the envelope, the 12V load running your car is roughly 20 amps X 14V=280 watts. 1 HP=0.735kW, or 735W, so if you could get all 12V energy from braking, you'd save whatever gas it takes to run a ~1/3 HP engine (or something like that)... I'm sure there's some conversion calcs floating around...

Ideally you'd have a battery that could sink all the kinetic energy from braking. The IMA pack can't even do that...

In practice you'd need a battery and a management system that could recoup as much regen energy as is needed to always be able to put out that ~280 watts. How much would that be? How much braking would you need to do? Gettin' too complicated for me... But picture how long a typical coast-down regen takes, the power you can deliver, and then the power you'd be able to absorb with whatever storage medium/system you create...

Starting to sound a lot like the stock IMA system to me...
 

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Discussion Starter #17
This wouldn't be to replace the DC-DC, but rather help it in city driving and short trips when the RPMs are too low for the DC-DC to compensate for start/stop and shorter trips.

However it is quite obvious now that such a system would provide too little benefit for the complexity of creating it. And as you said, it would basically act like the IMA, minus all other IMA functionality, which is making me strongly consider IMAC&C to be able to disable the battery but keep it's functionality for autostop, 12V aiding, and any little assist or regen I might want to do. The calpod mod isn't compatible on my 2006.
 

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This wouldn't be to replace the DC-DC, but rather help it in city driving and short trips when the RPMs are too low for the DC-DC to compensate for start/stop and shorter trips.
Someone correct me if I'm wrong but my understanding is that with the IMA system disabled, the DC-DC converter doesn't work properly at *high* RPM's (over 4000). Low RPMs are fine. The problem is that without the IMA battery as a buffer, high RPM's produce a high voltage from the permanent magnet motor-generator, which causes the DC-DC converter to disconnect momentarily and the bat light to come on. At low RPM's the voltage output is lower but still plenty for the DC-DC converter to produce 14V output.
 

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Discussion Starter #19
Someone correct me if I'm wrong but my understanding is that with the IMA system disabled, the DC-DC converter doesn't work properly at *high* RPM's (over 4000). Low RPMs are fine. The problem is that without the IMA battery as a buffer, high RPM's produce a high voltage from the permanent magnet motor-generator, which causes the DC-DC converter to disconnect momentarily and the bat light to come on. At low RPM's the voltage output is lower but still plenty for the DC-DC converter to produce 14V output.
Yes, the DC-DC shuts off whenever the engine is at or higher than 4000 RPMs.

To my knowledge, at 1500 RPM or 1300 RPM or less the DC-DC requires additional power from the IMA to keep 14V. With the IMA disabled, anytime my RPMs are 1300 or lower, the 12V only reads 11.9-12.3V, with the lower end being at idle.
 

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Yes, the DC-DC shuts off whenever the engine is at or higher than 4000 RPMs.

To my knowledge, at 1500 RPM or 1300 RPM or less the DC-DC requires additional power from the IMA to keep 14V. With the IMA disabled, anytime my RPMs are 1300 or lower, the 12V only reads 11.9-12.3V, with the lower end being at idle.
This is also my understanding. However, I don't imagine you're hurting anything by letting the voltage drop a bit? Have you had any specific issues yet?

For what it's worth, I'm very happy with my Mean Well DC-DC converter, but the stock one was working well enough for me too, even given my typical low-RPM driving habits.

In answer to what I believe your question is, you would like a supplemental DC-DC converter to load the engine when you press the brakes. You can do this relatively easily, but I don't think it's worth the time. Here's how I would do it though:

I'd buy a large Mean Well DC-DC converter, maybe a 1000w or higher unit. Bypass the rectifier, and hook it up in *parallel* with the existing DC-DC converter. Have it on a relay that's activated by your brakes, so that it powers up when you press your brakes. It will provide additional load on the IMA motor (which is already lightly loaded by the stock DC-DC) and give a very low power sort of regen braking. However, it begs the question of, why not just use this aftermarket DC-DC converter all the time, if your stock one isn't doing its job well enough?
 
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