Potential new Honolulu i-MiEV owner

Like JoeS, I own an original Honda Insight which we shipped to Uppsala, Sweden, where we live half of each year and are now until the fall. This has left us with no car in Honolulu, our other home. I am actively researching the purchase of an EV for Honolulu because, in many ways, Oʻahu is ideal for EV usage. This has suddenly developed increased urgency because I think that Hawaiʻi's $4,500 EV purchase rebate plus $500 EV charging equipment purchase and installation rebate seems destined to run out of funds by the end of May. I've noticed some Hawaiʻi owners in this forum. I would like to ask them whether I am correct about the status of these rebates.

If these rebates are about to run out of funds, what would you think about my purchasing a i-MiEV sight-unseen from Cutter Mitsubishi? Is there anyone at Cutter whom you would recommend I contact? Cutter seems to have several i-MiEV's in stock, so purchasing one before the end of May should be doable, I would think. I prefer a light-colored ES, but Cutter seems to have only one of them in stock. I don't value the additional SE features, especially for driving around in Honolulu for only half of each year.

A problem with i-MiEV ownership would be my parking it for about 6 months each year. This has caused serious problems with my Insight NiMH battery pack due to differing self-discharge rates of each battery cell and a BMS that doesn't rebalance cells. I understand that the i-MiEV BMS should rebalance cells during full charging. Is that correct? Does the included 120 v. battery charger have the option of "storage" charging (only partial charging) like the Leaf charger? I could probably ask a friend to charge my i-MiEV occasionally while we're away so that its battery pack doesn't fully self-discharge which is apparently not good for a Li-ion battery pack, but I would not want him to have to monitor the charge level to prevent full charging which also is apparently not the best way to store a Li-ion battery pack.

alohart, you hit us with many questions. I'll let the island residents answer you Hawai'i-specific rebate queries.

The white iMiEV I would think to be the most suitable for your climate simply because white reflects the sun's rays better than any of the other colors. The added advantage is that it is more visible at night. I think the iMiEV would be ideal for O'ahu!

For long-term storage (I presume your car will be indoors) you have the two different batteries to deal with:

For the 12v battery you can elect to simply put a small (less than an amp) smart float charger (float voltage of around 13.1v @ 80degF after it goes through its initial absorption phase) on it, with perhaps a timer to turn it on every few weeks for a few hours. DO NOT use an old-fashioned unregulated "trickle charger" - those are best thrown away. What depletes this battery is the alarm system and other minute current draws. All modern cars have this problem and it's not limited to EVs and hybrids. I did this when I stored my Insight, and I actually left my float charger on all the time. I still use the float chargers now plugged in all the time even though we drive the Insights at least once every couple of weeks. Disconnecting the 12v battery to keep it from depleting on the iMiEV I don't know ... on the Insight that scrambles the BMS memory.

For the 330v main battery -
It's my understanding that the optimal storage SOC for Lithium Ion batteries is around 40%, which would mean to leave it stored at around 7 bars. DO NOT fully charge it up before leaving, and I would leave the power plug unplugged just to ensure some friendly soul doesn't decide to do you a favor and 'top it up'.
Have your friend check the fuel gauge every couple of weeks initially, to see if it's moving. I don't know what the self-discharge rate for this battery pack is, but I suspect it won't budge at all. After a couple of months it might drop a bar, if at all. I would be inclined to then charge it briefly to bring it back to 7 bars, even though it would probably be better for the battery pack to fully charge it to let the BMS balance the cells and recalibrate itself and then drive the car back down to the seven bars (but you probably won't have the car insured while it's being stored). I'm speculating here and I haven't dug into the Mitsubishi manuals to see what they have to say about storage. Someone may wish to chime in?

JoeS said:

alohart, you hit us with many questions.

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Yeah, I realized that after posting. I should have broken it up into separate threads.

JoeS said:

For long-term storage (I presume your car will be indoors) you have the two different batteries to deal with:

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Yeah, indoors in a parking garage where temperatures average around 80º.

JoeS said:

Disconnecting the 12v battery to keep it from depleting on the iMiEV I don't know ... on the Insight that scrambles the BMS memory.

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I always remove the 12 v. battery from my Insight and store it in our warm apartment during the 3-6 months of storage of our Insight in our unheated carport. The BMS memory is quickly refreshed when the car is first driven after storage, so that's not a problem. I assume that the i-MiEV's BMS can recover well from an interruption in the 12 v. supply.

JoeS said:

Have your friend check the fuel gauge every couple of weeks initially, to see if it's moving.

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I'm guessing that the 12 v. battery would need to be connected for the fuel gauge to function.

JoeS said:

I don't know what the self-discharge rate for this battery pack is, but I suspect it won't budge at all.

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I've read that Li-ion battery cells don't self-discharge as rapidly as NiMH battery cells. The self-discharge rate increases with temperature, so at ~80º, I would expect noticeable self-discharge in an i-MiEV battery pack over 3-6 months. I just need to figure out how to prevent battery pack damage during storage.

Art - I haven't disconnected my 12v battery yet, so I don't know what it would take for the BMS to find itself and properly indicate the main battery SOC on the fuel gauge after reconnecting. I suspect the charger would need to be plugged in for a while. I've noticed that during charging my car charger occasionally turns itself off for ten minutes before resuming charging - I've assumed that's the BMS recalibrating itself. Mitsubishi sent out a letter asking us to at least once a year discharge the main battery pack down to two bars and then allow it to fully charge itself back up. I've been tempted to replace the FLA battery under the hood with an AGM just to ensure no corrosion there in the future.

JoeS said:

I haven't disconnected my 12v battery yet, so I don't know what it would take for the BMS to find itself and properly indicate the main battery SOC on the fuel gauge after reconnecting. I suspect the charger would need to be plugged in for a while.

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That's a good point, JoeS. As you know, with the Insight, starting the ICE causes the IMA motor/generator to force-charge the IMA battery pack after the BMS has lost its charge level information. The BMS can detect a fully-charged state within at most half an hour with the ICE running.

In the i-MiEV, the charger would probably need to charge the Li-ion battery pack up to the point where its voltage would indicate that it's nearly fully charged before the BMS could determine the charge level. That could take many hours (unless the BMS retains charge level information even with the 12 v. battery disconnected).

JoeS said:

I've been tempted to replace the FLA battery under the hood with an AGM just to ensure no corrosion there in the future.

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I've been happy using a small 13 Ah Odyssey AGM battery in my Insight for several years. Not only does it prevent corrosion, but it's considerably lighter since the smallest standard automotive-size FLA battery has a much larger capacity than is needed by a car that rarely uses its 12 v. starter motor. I would think that the 12 v. needs of the i-MiEV would be minimal as well, so a small 12 v. AGM battery should suffice. Is that a reasonable assumption? What size is the 12 v. i-MiEV battery?

Well, my potential i-MiEV ownership has receded into the future a few months…

I called the Internet Sales Manager of an Oʻahu Mitsubishi dealer with i-MiEV's in stock to inquire about purchasing an i-MiEV before Hawaiʻi's $5,000 EV plus EVSE purchase rebate funds are depleted. The good news for EV enthusiasts is that Hawaiʻi is currently processing 60 purchase rebate applications, so EV's (probably mostly Leafs) are selling pretty well in Hawaiʻi. The bad news for me is that, with only $160,000 remaining today, the funds will run out before the outstanding applications are processed. So the early bird gets the worm, but I'm not an early bird. Adding $5,000 to the purchase price makes an already rather senseless (economically) purchase (I would drive it less than 2,000 miles and 6 months each year) even more foolish. I've driven my Insight only about 25,000 miles in 10 years, so the last thing I need is another car that I don't use much. But I like fun new tech toys

Plan B is to wait until I return to Honolulu next fall to reassess the EV market. Maybe there'll be a used i-MiEV for sale for a good price (i.e., less than the ES net price of ~$16,000 after the Federal tax credit and Hawaiʻi purchase rebate). In 2002, I bought my 2000 Insight in Honolulu from the original owner for about 2/3 of its original purchase price. Maybe I'll get lucky again…