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· Registered
30 Posts
Discussion Starter · #1 ·
Hello all.

Three questions:
How long can an Insight sit before I should start worrying about the battery? Does downtime matter more if it's sitting a hot climate? And, is there a way to assess a battery after a long period of nonuse (say three months)?


· Administrator
14,392 Posts
Battery Life

I would say three months is a long time, too long really.

Nimh cells have a high self discharge rate, and may well be flat when you come to use the car again, even if full when stored. The cells could certainly be badly out of balance within the pack.

This could cause an eroneous battery detrioration code to be set along with an IMA light when you start using it again, I imagine you will see a few recals straight away, and then a fault code. However if your pack is relatively new, well balanced with no weak cells you may be OK. Even if you do get a code, an IMA reset and some regular use may re-balance the cells quite quickly.

It would be best to get someone to drive it weekly for you, doing you, them and the environment a favour!


· Registered
459 Posts
re. lead acid batteries ...

- If you pull a good battery from a car and plant to put it on the shelf for two weeks or more, put what is known as a "trickle charge" to it. Most small battery chargers have this built-in facility.

- If the battery is ten (10) or more years old, expect it to fail - soon.

Hope this helps.

Fred :)

· Registered
221 Posts
There is no way (without alot of homebrew) to determine the capacity of the battery.

In my best guess, the BCM does not keep a clock and factor in self-discharge while the battery is sitting. So, after a long period of inactivity, the BCM may think the battery is fully charged when it's mostly discharged. So it may allow large loads on the battery while it is mostly discharged which it a great way to damage a battery. So my advice to anyone who lets their insight sit for over 2 weeks is to force a recal before starting it. (if you don't know how to force a recal, search).

· Premium Member
4,836 Posts
Good advice Marty :!: :)

However, its for _long term_ extension of the IMA batteries service life that only the middle range of capacity is used. To deplete the true SoC ("true" is not shown on the gauge) to lower that the normally used 20% limit once in a blue moon IMO will cause no long term damage.

But an unexpected recal when driving is never a welcome situation so a reset after a long "down" time IS a very good idea. :)

HTH! :)

· Registered
170 Posts
There's the issue of the SOC indicator being confused when you start up, and there's the issue of damage to the battery. I think that the NiMH IMA pack will self discharge and confuse the SOC indicator, but that won't damage anything. But the lead-acid 12 V battery will get damaged more if it is allowed to dwindle. When I leave my Insight for more than a week, I like to put it on a 12 V battery maintainer.

I do think that the IMA pack self-discharge goes faster at high temperatures. I once had the experience of leaving the car for about 3 days in 90+ temperatures on a wide-open asphalt parking lot. The temperatures inside the car were surely well above 100, perhaps 120. The pack was nearly full before the 3 days, and I had a re-cal almost immediately when I left the parking lot.

Here's a good reference that shows on the bottom of p. 10 the
self discharge vs. time and temp:

Panasonic NiMH battery manual

At 20 C, you can leave them sit for 4 weeks and lose less then 20% of the
charge. At 45 C you lose 40% of the charge. But in neither case are
the batteries damaged. In fact, I've seen it recommended to store NiMH at about 40% charge. That's in sharp contrast to lead acid which degrades rapidly if it sits at anything below full charge.

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