I have copy and pasted this from another thread per the request of a few other users. I decided to put it in the general HCH forum since it applies to I's and II's.I will keep this post updated with any new info I find about the current IMA situation and what we as consumers can do to make our cars last as long as they are supposed to(betting on 150-200k miles).

Ok 1st a little advice about the NIMH cells that Honda chose to use, they are all small cells and they are tightly wrapped together, not the best engineering move, but understandably done for cost reasons(who wants a 200000$ car with experimental batteries?)

However, there are a few things you can do to extend the viable life of a battery pack such as this one. Like most D-cell NIMH batteries they each have a expected life of ~400-600 complete charge and recharge cycles. Now here is where the problem lies for many people who don't understand batteries all that well. Toyota's Prius smartly included a feature to keep their NIMH battery pack between 30-70% most of the time, no matter what the driver does. If a NIMH battery is never fully cycled then it has an almost magical property of repairing itself over time and lasting 5-10 times longer than if it were fully cycled. There is a trade-off though eventually the batteries start losing Amp Hour capacity and still need to be replaced… but at much longer intervals.

It works sort of how halogen headlights last 2-5 times as long as their old counterparts. The halogen keeps "redepositing" the evaporated tungsten back onto the element rather than all over the bulb. Just an analogy….

Another problem with using hundreds(Honda uses 120) of small batteries is they usually don't all fail at once, one or 2 of them will go bad at first, then they start dragging down the voltage of the good ones, actually causing intense heat which damages the adjacent cells further, you see the pattern.

The Honda user is responsible for never letting those SoC bars fall below 2(also don't let your car sit for 2-3 months, it will never be the same) or sit at full for any long period if possible. This makes the HCH-1-2 both much more difficult systems for the user to manage. Most people like to get in the car and drive, this car requires more.

Ok now the TLDR tip list:


1. Seriously, drive like a grandma if you want the MPG the EPA claims and plan your routes ahead of time, if not, be happy with your 32-37 mpg that you get from a good running, hard driven HCH. It's still way better than most cars weighing 2800 lbs.

2. Keep your cabin cooler than 80 in the summer, please don't overdo it when hyper-miling, (your battery pack needs to be kept cool!) I might have an aftermarket solution to this dilemma available in the future.

3. Look into replacing your pack in the future with L-ion, when it becomes available. www.reinvolt.com looks like they will have it first right now.It's an easier to deal with battery for many reasons and IMO what Honda should have gone with in the very beginning for it's hybrid vehicles. I know there used to be issues with max AH ratings and heavy load heating, but those are pretty much moot now with TFP-LION(thin film polymer lithium ion) technology it can be, lets say, shaped right for max cooling.

4. For HCH II owners only (Keep your SOC between 2-7 bars if you have an unaltered HCHII) Don't get the update unless you are willing to accept the consequences. It's a bit like a pill for an heart attack, it makes you feel like @%^ but it keeps ya alive if you cant manage to on our own, eat right, not smoke etc….. Please ask your Honda dealer to fully test your IMA battery before accepting the update.

5. Enjoy learning a new way to drive, and for all those who are considering a current generation HCH you will need to do research on how to drive your car most effectively, I think Honda needs to offer training classes to all buyers, but i can see how they wouldn't(might scare off customers).

6. I know HCH II cars have this feature, could someone confirm if HCH I cars do as well? If you are in stop and go traffic and you find your SoC meter getting too low you can downshift to L for 3 bars of charge in idle and much more aggressive charging while driving slowly than D would permit.

7. (from cwerdna) Related to #2 and assuming NiMH batteries are better left stored in cooler temps, I'd suggest parking in the shade or in covered parking, if possible. IIRC, one guy on Priuschat who needed HV battery replacement under warranty lived in a hot climate and hilly area. If you must park in the sun, use a sunshade and park w/the windows cracked open a bit to keep the cabin temp (lower).

 

Any other suggestions are welcome of course =)

 

(I have no HCH, just a 2nd gen Prius.) Related to #2 and assuming NiMH batteries are better left stored in cooler temps, I'd suggest parking in the shade or in covered parking, if possible. IIRC, one guy on Priuschat who needed HV battery replacement under warranty lived in a hot climate and hilly area. If you must park in the sun, use a sunshade and park w/the windows cracked open a bit to keep the cabin temp.

At my apartment complex, I have a covered spot, but the back of the spot still receives sunlight. In the summer, I back into the spot so only the hood area receives sunlight and the hatch area where the HV battery is, stays cool. (The Prius' 12 volt on 2nd gens and beyond is also in the back, not under the hood.)

http://www.gpbatteries.com/html/faq/index.html and http://www.eneloop.info/home/faq.html seem to concur about cooler temps. (I wish I were a battery chemist.)

 

It's about both storage and a warning to hyper-milers and all who drive with all the windows down in 95 deg. weather, that will kill these NiMH packs fast, since they full cycle the packs faster(more often) as the cells heat up.

Think of it this way the hotter the cells are, the smaller of an energy sponge(Literally like taking the battery and cutting it in half at a certain temp) they become, eventually leading to their doom as they cycle faster and recal more.

Btw thats a good idea to keep the cabin cool when you aren"t in the car too (go do a look up of D-cell NIMH batts and their specs) then you will understand they really do have a pretty narrow operating temp range, compared to, say an alkaline battery. and if you flog the batts when they are out of their temp range you will do damage to them simple as that. Honestly, I bet much of the reason these packs wont pass 100k usually is due to their diminutive size and the sheer amount of usage some people put on the assist, since they are used to driving compact cars with 150+ hp…. one of my first cars I had was a 1982 toyota tercel(guess I have always been Eco-minded) and this HCH has way more power than the cars I am used to having as DD's, lol I don't even use the assist much at all.

 

Jamchel, any progress on your after market solution for point #2. I'm very interested.

 

This quote is 100% back ashward wrong.

1. Hypermilers do not drive with the windows down. Driving with windows down creates a large drag, but we do drive with the front windows open about 1 to 1-1/2 inch.

2. Hypermilers do not full cycle the batteries. HCH 1 (not sure about the HCH 2) hypermilers use the pack as sparingly as possible. Good ventilation with a very seldomly used assist is not detrimental to battery life.

I am fast approaching 200,000 miles and the car was hypermiled more than 100,000 of it. I have not had a single recal.

I've heard a lot of silly reasons why people shouldn't hypermile, and I've only heard that comment once before. It was from my Honda dealer's assistant service manager back in 2004 who didn't know what she was talking about and no longer works there.

I will argue that excessive use of the packs is what will cause them to heat up, which would be a heavy lead foot, lots of passing and excessive exelleration.... The opposite of hypermiling.

I no longer hypermile myself, but I encourage anyone interested to learn the skill which can be applied to any vehicle and once learned is easy to duplicate if needed.

Incorrect rumors and hearsay isn't helpful. A hypermiled car can last much longer than a vehicle non-hypermiled because the stresses on the entire vehicle are considerably less.

Sorry and I don't mean to jump your bones, but it had to be said.

 

Sorry for the 7 year thread bump, but I assume this means the ECU IMA update DOES prevent the Hybrid battery pack getting that low? My HCH2 rarely (if ever) goes below 3-4 bars on the battery gauge, even under hard continuous acceleration. I've never seen it go to 1 or 2 bars. To me, this means I must have the IMA ECU update. Correct me if I'm wrong here!

 

In response to the quoted above, asking a dealership to "fully test your IMA battery" is hilarious. They will hook up HDS, check for codes, tell you your battery is fine if there are none, patch it and accept $150 or so for their services. The HDS reported "usable capacity" value is denied by dealers that it even exists.

Consequences of patch... if your battery is actually healthy, it will have no noticeable effect and probably last longer. If your battery is typical (deteriorated and imbalanced), you will be treated to recalibrations out the wazoo as the 11 voltages go out of sync with each other at the upper and lower limits. My first '06 did this for about 1.5 years before it ever threw a P0A7F code.

I'm still in touch with the new owner of my first '06, and he confirms this behavior of a KNOWN patched car. For a truly healthy battery, it will typically stay between 5 and 7 bars. That goes lower with heavy stop and go traffic and heavy A/C use here in Phoenix. I have never personally seen it go to 2 bars UNLESS it was in a negative recalibration and conducting a forced charge.

Given that the patch was issued in 2012, it's likely that it's been applied if it's been in a dealership since then.

 

Yep, I feel very lucky that I've not had any re-calibrations so far, at least none that I have noticed. Interesting the patch came out in 2012, likely my car got that around the 70,000km mark in that case, so probably why the battery in mine still seems to be OK.

So this definitely appears to be the case then! What led me to also think this is on page 69 of the manual it says this about the battery gauge:
The gauge reading may drop near the bottom under driving conditions that require IMA motor assistance for a long time, such as prolonged acceleration or climbing a long hill. The engine will recharge the battery as you continue driving.

There is a long sustained hill on a highway on my commute, and even on that, the bars never go below 4. The car simply does not allow the assist to drain the battery the way it describes in the manual, so I have a feeling that the manual is describing the first version of the software here. Just need someone with an un-updated car to really confirm it, if there are any still on the road.

One of the first things I wondered about when I got the car was whether it was updated or not, so at least now I'm sure it was.

 

Sounds like it.