Gorfllub
Posts: 74
Joined: Sat Aug 04, 2018 6:08 pm

Any tips to NOT damaging the main battery?

Thu Sep 06, 2018 11:54 am

What frowned upon (but not warranty-voiding) practices should I stay away from to prevent untimely battery death?

Let her freeze up really good in the winter on zero charge?

Or?
Last edited by Gorfllub on Tue Sep 11, 2018 9:55 am, edited 1 time in total.

jray3
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Re: Any tips to damaging the main battery?

Thu Sep 06, 2018 12:04 pm

Haha, you dirty dog, trying to push a cell over the edge, are you? :twisted:
That's quite a gamble, but if I were a gambler, I'd drive into the turtle EVery time and then DCFC only, with no nice n long balancing recharges. Of course, the dealer should try a full L1 recharge if you come in complaining....

Our packs don't seem very vulnerable to heat or cold. If that were the case, MALM and other sunbelt drivers would've experienced more pack failures.

Saltwater intrusion would not be a warranted failure, same as any other physical damage.
2012 i-SE "MR BEAN" 93,000 miles
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Gorfllub
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Re: Any tips to damaging the main battery?

Thu Sep 06, 2018 1:34 pm

Shhhhhhhh..... Don't tell anyone!

Only 1 QC charger in town and it isn't free :(

Currently enjoying free power from work!

I think I have til dec 2019 for battery warranty. I wouldn't be too upset if I managed to get it replaced for free. :)

I only turtled once on a range test. But I can certainly do that daily. Lol.

Don
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Re: Any tips to damaging the main battery?

Thu Sep 06, 2018 3:02 pm

If you do your best to destroy it, I predict it will die a couple weeks after your warranty expires! :lol:

Don
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2012 iMiEV SE, White
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kiev
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Re: Any tips to damaging the main battery?

Fri Sep 07, 2018 4:14 am

Well i have a dumb idea--just let the car sit unused with a drained pack for a few months.

It looks to me that the 12 Cell Monitoring Unit boards inside the pack are constantly powered up using some of the cells in the module to which they are attached. Over a period of time those cells will be pulled lower than the rest and get out of chemical balance. The CMUs don't have any mechanism to disconnect cells or turn them off if they go too low, they only provide resistor-shunt bleed-off-balancing at the top end during charging. And it is a very low-level balancer, not capable of large corrections.

So if a cell gets drained to the point that it crosses below the reversal threshold voltage, then metal ions will begin plating out at the electrodes. It will get damaged by the metal dendrites that will grow and puncture the separator during subsequent charging and internally short out the cell.

Then when the damaged cell gets cycled and exercised fully between full and empty, it will aggravate the situation such that the pack won't charge up to 16 bars anymore, which is how the dealer determines the pack is bad.

But the dealer also has the MUT which can read out data list items from the BMU about the charging history of the pack. One of the conditions of the warranty is that you must leave it connected to the EVSE when not being used for an extended time. And you will have to fill out a questionnarie that asks about usage and charging history. So they have access to usage and charging data thru the MUT to know the answers if they choose to investigate and could deny the claim. Just sayin'...
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Gorfllub
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Re: Any tips to damaging the main battery?

Fri Sep 07, 2018 7:46 am

LOL @ Don

As far as the BMU memory...... Gotta be a way to disrupt that information. Maybe even unplug it after depleting the battery. Or disconnecting the 12v?

Without power, then it certainly cant record anything.

Don
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Re: Any tips to damaging the main battery?

Fri Sep 07, 2018 7:55 am

kiev wrote:Well i have a dumb idea--just let the car sit unused with a drained pack for a few months.

It looks to me that the 12 Cell Monitoring Unit boards inside the pack are constantly powered up using some of the cells in the module to which they are attached. Over a period of time those cells will be pulled lower than the rest and get out of chemical balance.

I suspect it would take a long time - Evidently, the BMU doesn't draw very much. We left one of our cars sitting unused for a year with 4 bars showing on the gauge and when we fired it back up again (after installing a new 12 volt battery) it still showed 4 bars on the gauge

Don
2012 iMiEV SE Premium, White
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philou
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Re: Any tips to damaging the main battery?

Mon Sep 10, 2018 6:54 am

Isn't it possible to force the balancing load of one cell to turn ON by sending a CAN command to the BMS ?
Or, on a harder way, open up the battery and put a resistor in parallel to one of the cells. That will certainly drive that cell to death by undervoltage.

Edit: found this topic, this should do the job...: http://myimiev.com/forum/viewtopic.php?f=23&t=4092#p36644

JoeS
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Re: Any tips to damaging the main battery?

Mon Sep 10, 2018 1:15 pm

Hey guys (and gals), sorry, don't mean to offend anyone -

I have an ethical problem with this thread.

From the perspective of the manufacturer, their engineers did their best to design a battery management system to protect the battery so that Mitsubishi management could stick their necks out and commit to a 8-year (or 10-year) free-replacement warranty (at least, in the US). Mitsubishi was the first to do this with a large format Lithium-ion pack, following their predecessors (Honda and Toyota) who also took a big gamble with their NiMh packs at the turn of the century.

One has to appreciate the technical difficulty of doing this so the battery can not only survive but also operate while soaking in some pretty horrendous temperature extremes, especially without resorting to liquid thermal management. To their credit, Mitsubishi did it better than their successor, Nissan.

One battery replacement probably eats up any profit Mitsubishi made on the sale of that car.

At that point in time, despite accelerated life testing, there simply wasn't enough long-term real-life data available. So, I suspect in order to limit their exposure, Mitsubishi purposely did not warrant a battery degradation percentage - something we were aware of when we bought the car, and certainly not happy about. As early adopters, we joined the manufacturer in taking a chance, and were certainly concerned at what the future battery replacement cost would be.

History has shown a gradual capacity loss of the battery pack that is, to me, better than I expected (I feared 40% within five years). History has also shown that a single cell failure is readily identified by the car's BMS and in every case I know of Mitsubishi has bellied-up to the bar and replaced the pack without a squawk, deeming it a cell failure and not overall pack degradation.

So far, so good.

Now, along comes someone purposely trying to damage the battery in order to cash in on the warranty deal. Not cool, in my opinion.

That said, I am quite upset with Mitsubishi and their failure (to date) to do anything about the charger/dc-dc that their data must now show has had an uptick in module failures. We'll open up a separate thread to discuss that and what recourse we have, as Mitsubishi's replacement price for that one module now comes close to exceeding the value of the car on the used car market.
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Gorfllub
Posts: 74
Joined: Sat Aug 04, 2018 6:08 pm

Re: Any tips to damaging the main battery?

Mon Sep 10, 2018 4:51 pm

I work at a dealership.

This type of thing happens every single day and is part of doing business in the automotive world.

In fact, I see things warrantied all the time that aren't actually bad, just to make a customer feel better. Approved by the mfg.

I don't feel bad about it in the absolute slightest. Warranty work keeps my fellow technicans employed. I am certain our dealership generates as much revenue in warranty work as retail work. Maybe even more. It actually helps my local economy.


But I'm not talking about opening the pack or anything extreme, but merely operating it in such a way that any owner could do. I do plan on using the car hard in the future. May as well do that now to see how things hold up. And hey, if the battery fails while still under warranty, that would be much better than after it expires.

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