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Discussion Starter #1
This summer I plan on removing my IMA (by choice, not from any major IMA degradation) but keep the stock DC-DC converter due to it's ruggedness, higher current output, and proven reliability over the Meanwell PSU.

The plan is to remove the aluminum IMA compartment cover, relocate the tools area in the back to where the IMA battery was, open up the back behind the battery for storage space, and then build a cover to go over it all with sections removable to access the DC-DC, new tools area, and the expanded rear storage area.

Post IMA delete, idle RPMs will be back down to around 900 vs the 1200-ish that they are currently with the dummy lights on. To compensate for this my plan is to replace the 12V battery with a marine deep cycle battery.

I've seen deep cycle batteries that can sustain a 25A draw for over 6 hours, but they weigh over 60 lbs. One with a couple hours should probably suffice, I'm thinking. Enough for me to do extensive engine off coasting at night with headlights on without draining the 12V down too low.

Are any of you currently running deep cycle batteries in your Insights? Which brands and capacities work best for you? How long is the typical lifespan of a deep cycle battery compared to a typical 12V battery? Costwise I'd like to keep this under $200 if possible, but I'll go up to $300 if a more optimal capacity battery costs more and if their lifespan is long enough to justify the expense.
 

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Post IMA delete, idle RPMs will be back down to around 900 vs the 1200-ish that they are currently with the dummy lights on. To compensate for this my plan is to replace the 12V battery with a marine deep cycle battery....
I don't think there's much if any difference in output at 900 RPM vs. 1200. Probably the first, main thing you'd want to do is clip the wire responsible for putting the DC-DC into 'low power mode' (~12.2V output vs. ~13.8V). Here's a link to a post with a graphic mudder made about which wires to cut. There's two wires that do slightly different things, can't remember which one to cut to simply disable 'low power mode' vs. preventing the DC-DC from turning off completely: https://www.insightcentral.net/forums/modifications-technical-issues/85641-shed-easy-22-lbs-stick-based-nimh-12v-battery-4.html#post1278738

I think it'd probably be a good idea to use a deep cycle marine in your circumstances regardless, at least it'd be more appropriate than a normal starting lead acid...

edit: ^Actually, I forgot that, without the IMA you'll be using the 12V to start - so I don't know if a deep cycle marine would be more appropriate or not. Probably, a lot of them still have good cold cranking power and the Insight doesn't need much.
 

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Discussion Starter #3
Isn't 1200-ish RPM the lowest engine speed where the DC-DC converter will run? I always presumed that <1200 RPMs triggered the dummy lights, just like >4000 does.

Will cutting those wires allow the DC-DC to charge better at lower RPMs or does it just ensure that the battery is always at 13.8v?

CCA doesn't seem to be an issue unless you live in the far north from what I've read. Some of the deep cycle batteries I've looked at have higher CCAs than my current 12V (500 or 550 CCA).
 

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ANY lead acid battery with the proposed > 120 minute reserve capacity (25A for 2 hours) will have ZERO issue with any load the Insight starter can impose.

"Deep cycle" is frequently mis-used and misleading. You need to find batteries that have cycle lives in excess of 300 with 80% depth of discharge. If you can't find that information for a battery, don't buy it. AGM will cost more but give you better results/life.

Bigger is better. When you start looking at depths of discharge of only 40%, cycle lives can push into the 2000s.

Buy the biggest, highest capacity, best cycle life battery you can find, and count on replacing it every 3 years for a cost of ownership analysis.

I don't have any specific recommendations, but avoid anything made by Johnson Controls (including Optima) and anything else made in Mexico.
 

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Isn't 1200-ish RPM the lowest engine speed where the DC-DC converter will run? I always presumed that <1200 RPMs triggered the dummy lights, just like >4000 does.
In general it's always running, just that it doesn't put out much if any power at low RPM. My comments were mainly based on my experience when I started experimenting with a NiMH stick-based 12V battery, and I had the IMA disabled. Idle speed was bumped up automatically - to around 1200 - but as I recall it still wasn't fast enough to charge the 12V. I had to bump it up more I think to something like 1400... As I recall I was watching the 12V parameter on the OBDIIC&C and that's how I determined whether it was charging or not...

Will cutting those wires allow the DC-DC to charge better at lower RPMs or does it just ensure that the battery is always at 13.8v?.
Cutting one of the two wires, not sure which, will just ensure that the DCDC doesn't drop into low power mode, where it only maintains a voltage at the battery of about 12.2V. So yeah, it will usually be at 13.8V-14V...
 

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Discussion Starter #7
"Deep cycle" is frequently mis-used and misleading. You need to find batteries that have cycle lives in excess of 300 with 80% depth of discharge. If you can't find that information for a battery, don't buy it. AGM will cost more but give you better results/life.
I must've had bad luck tonight; the only AGM deep cycle batteries I found with such information listed had 600 cycle lives with 50% depth of discharge.

In general it's always running, just that it doesn't put out much if any power at low RPM. My comments were mainly based on my experience when I started experimenting with a NiMH stick-based 12V battery, and I had the IMA disabled. Idle speed was bumped up automatically - to around 1200 - but as I recall it still wasn't fast enough to charge the 12V. I had to bump it up more I think to something like 1400... As I recall I was watching the 12V parameter on the OBDIIC&C and that's how I determined whether it was charging or not...

...

Cutting one of the two wires, not sure which, will just ensure that the DCDC doesn't drop into low power mode, where it only maintains a voltage at the battery of about 12.2V. So yeah, it will usually be at 13.8V-14V...
The comment about the modes on the DC-DC makes sense. Regardless of whether I am driving in 5th gear at 1200 RPM around town or 2000 RPM on the highway the voltage cycles between 12.5 and 14.2, so I figured that the DC-DC's lower limit was around that 1200.

I think I will try cutting that GREEN/WHITE wire when I remove the IMA and see if that helps. I haven't had any issues with the 12V staying charged during EOC, except on longer coasts at night with the headlights on, and even then only sometimes. I am led to believe that the cause for that is the DC-DC being on the "low power mode" before I began my coast, and thus the 12V was already low before shutting the engine off, rather than a lack of capacity of my 12V. We shall see.

How much idle do you plan to do?
I only idle on short coasts, when making non-stop turns at intersections, and whenever I'm with a passenger who is paranoid about my hypermiling. Any extensive coasting is engine off.

Why not install a voltmeter?
I've been monitoring voltage with a Scangauge.
 

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I haven't had any issues with the 12V staying charged during EOC, except on longer coasts at night with the headlights on, and even then only sometimes. I am led to believe that the cause for that is the DC-DC being on the "low power mode" before I began my coast, and thus the 12V was already low before shutting the engine off, rather than a lack of capacity of my 12V. We shall see.
I saw earlier in a random chart that 12.2V on a lead acid is about 50% charged. So, I don't know, if that voltage can be treated like a float voltage (i.e. DCDC maintains at least 12.2V at the battery), and the float voltage is more or less the same as the resting voltage, then the battery is being maintained at about 50% - which doesn't seem too low... If you have say a 28Ah regular car battery, and it's at 50%, you should have 14Ah in it. Engine-off coasting with headlights and some stuff, maybe 300 W load? (Do you actually turn the key OFF?). 300W/12.2V=26 amps, 14Ah/26A=32 minutes... Factor-in some slop and, yeah, you really don't have a ton of energy at your disposal...

Normally, the DCDC can go into low power mode for quite long durations. I've never seen it do it with headlights ON...
 

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50% charged in a LA is in effect flat! You have in reality only the top 50% of an LA to use, also for it to have a long life it want to be at 100% as often as possible. If you can set the voltage on the DV to DC converter a Lithium drop in would be the best bet
 

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Have you driven it around with the IMA shut off? I can't imagine removing a healthy IMA from one of these cars.
 

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The 12.2V seen in the car is a LOADED "float" voltage as the 12V system is still supplying all needed current. This is well above 50% SoC. A charging battery that has just attained around 14.0V is at about 70-80% SoC.

Peter's point about keeping 12V batteries full charged is absolutely true. LA below 70-80% SoC eat themselves.

IMHO, anyone running sans IMA battery should be putting the 12V on a charger weekly if not nightly.
 

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ANY lead acid battery with the proposed > 120 minute reserve capacity (25A for 2 hours) will have ZERO issue with any load the Insight starter can impose.

"Deep cycle" is frequently mis-used and misleading. You need to find batteries that have cycle lives in excess of 300 with 80% depth of discharge. If you can't find that information for a battery, don't buy it. AGM will cost more but give you better results/life.

Bigger is better. When you start looking at depths of discharge of only 40%, cycle lives can push into the 2000s.

Buy the biggest, highest capacity, best cycle life battery you can find, and count on replacing it every 3 years for a cost of ownership analysis.

I don't have any specific recommendations, but avoid anything made by Johnson Controls (including Optima) and anything else made in Mexico.
I realize I'm violating a couple of my recommendations (Johnson Controls + Mexico), but the Interstate batteries post some good numbers. The only reason I'm even looking at them is somebody near me is offering a 6 month old interstate SRM-24 on CL for $60... :)

The flooded cell Interstate SRM-24 is relatively inexpensive ($114 MSRP) with a 140 minute RC and a 1000 cycle life to 50% DoD. Their 34M-AGM is equivalent, but it's over twice the price at $270 MSRP.

They are a little squirrely on the rating because they designate end of life at 50% rated capacity instead of the more typical 80% rated capacity typically used.

I'm likely picking this thing up for my motorhome since it's got to be better than the Everstart turds that are in there....

You'll have to find another place for it instead of the stock location.

I've attached a PDF from Interstate.
 

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I only idle on short coasts, when making non-stop turns at intersections, and whenever I'm with a passenger who is paranoid about my hypermiling. Any extensive coasting is engine off.
So, less than two minutes of idle each time...

Just get a store brand 12v battery with decent warranty and go.

I use my IMAless Insight for food delivery, lots of engine stop/starts with idle while using a/c. No issue here.

You're way overthinking a non-issue.
 

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Discussion Starter #14
(Do you actually turn the key OFF?)
Key off for 2 seconds, then back on to accessory for EOC.

50% charged in a LA is in effect flat! You have in reality only the top 50% of an LA to use, also for it to have a long life it want to be at 100% as often as possible. If you can set the voltage on the DV to DC converter a Lithium drop in would be the best bet
Lithium 12V replacements are quite expensive if one wants any kind of decent capacity.

Have you driven it around with the IMA shut off? I can't imagine removing a healthy IMA from one of these cars.
Definitely prefer driving it around without the IMA. Highway fuel economy improved plus there isn't any slight drag on the motor to keep the IMA charged even when no bars of regen are displayed.

The flooded cell Interstate SRM-24 is relatively inexpensive ($114 MSRP) with a 140 minute RC and a 1000 cycle life to 50% DoD. Their 34M-AGM is equivalent, but it's over twice the price at $270 MSRP.
Specs look fair. Would there be a way to wire this up with the stock 12V battery, or would I just replace the 12V with this?

So, less than two minutes of idle each time...

Just get a store brand 12v battery with decent warranty and go.

I use my IMAless Insight for food delivery, lots of engine stop/starts with idle while using a/c. No issue here.

You're way overthinking a non-issue.
Problem is that with engine off coasting the car isn't even idling, so it's just draining the battery at a fairly decent speed.

I haven't done any delivery post-IMA disable yet, but there really isn't much engine off coasting done during delivery runs to run the 12V down that far.
 

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Unless you're planning engine off coasting for 30 minutes at a time, I still think it's a non-issue, speaking from someone with the perspective of having an IMAless car and uses it food delivery.
 

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Definitely prefer driving it around without the IMA. Highway fuel economy improved plus there isn't any slight drag on the motor to keep the IMA charged even when no bars of regen are displayed.

Based on that statement, I'd say your IMA was far from healthy.
 

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Discussion Starter #17
Unless you're planning engine off coasting for 30 minutes at a time, I still think it's a non-issue, speaking from someone with the perspective of having an IMAless car and uses it food delivery.
Could be, which is why the first plan is to cut that GREEN/WHITE wire on the DC-DC to prevent the low-power mode and see if that keeps the 12v topped off.

Based on that statement, I'd say your IMA was far from healthy.
It's definitely not new, but I never had any issues with it except on long mountain grades that drained the battery down. Other than my temporary issues from corroded ground straps. IMA only really helps with acceleration, but you have to regen to charge it rather than coasting engine off, which reduces coasting distance and fuel economy.

By the "slight drag on the motor to keep the IMA charged" I mean the tiny constant charge that the IMA receives under coasting - visible when the bars on the battery go up slowly on highway drives without any visible regenning on the gauges. Only time forced regen occurred was near the tops of mountain passes or when I disconnected the 12V to replace it last year and the SOC reset to zero.

Highway economy improved because I can now engine off coast without having to worry about keeping the car in gear to charge the battery back up. I'm sure driving it the same way with the IMA as without the IMA would result in lower mileage with the IMA bypassed, but with my driving style I don't really experience any economy loss, except in extreme stop-n-go situations. Tire pressure in and of itself is worth much more than an IMA in terms of fuel economy, and the laws of physics make it clear that removing the weight of the battery will reduce the amount of energy needed to get up to speed.

If I had a MIMA or IMAC&C I'm sure I'd get better fuel economy with the IMA enabled, but those are expensive. Plus, without the IMA, I don't have to worry about a $2000 expense every so many years, or have to invest heavily in battery maintenance equipment.

If I ever do return it to hybrid form, it will be as a lithium PHEV with some form of IMAC&C and 20+ miles of EV only range, but that won't be for quite a while when I have both the funds and the knowledge for such a complicated conversion.
 

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Here's a link to some thread I found that has some seemingly good bits of info in it, on lead acid, state of charge vs. voltage, etc: https://electronics.stackexchange.com/questions/177032/how-bad-is-it-to-undervoltage-a-12-volt-lead-acid-battery

Here's one thing that speaks to the 50% charge idea/s, depth of discharge and battery life:

"Battery life is directly related to how deep the battery is cycled each time. If a battery is discharged to 50% every day, it will last about twice as long as if it is cycled to 80% DOD. If cycled only 10% DOD, it will last about 5 times as long as one cycled to 50%. Obviously, there are some practical limitations on this - you don't usually want to have a 5 ton pile of batteries sitting there just to reduce the DOD. The most practical number to use is 50% DOD on a regular basis."
 

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