Understanding NiMH hypercycles (to prolong Prius HV battery life)

great info and pretty much the way lead acid batteries works which leads to the
" great lie" EV car manufacturers are perpetuating. my EV was supposed to have a range up to 40 miles well that was at 25 mph. that was too slow, so i had the thing reset to do 35 mph. well, that dropped the range to just under 30. that was ok, but soon realized that my batteries were starting to fail and that happened in less than a year. batteries replaced, started charging at work so now, i rarely use more than 50% of my charge before recharging.

so far so good.

Li does not have the charge life issues, only the cost issues. not putting any more money into the Zenn, holding out for a highway capable EV that will do at least 100 miles

 

So I suppose it is bad for the battery life to run it down to 3 to 4 bars as opposed to keeping it at 6 bars?

 

no, not necessarily. its says best option is a 10% discharge. it does not mean 100% to 90%...in fact, pretty sure fully charged is not good either.


10% can also mean running from 70% to 60% which i think you will find is just about where your Pri spends most of its time. on a Pri... well, at least on the classics, 8 bars is 80%, zero bars is 40 %...

running between 6 bars to 3 bars is probably around a 15% change give or take.

 

This seems to support the notion that owners who live in mountainous terrain can expect shorter traction battery life. I live at 1,100 ft elevation and have had two battery failures (thankfully covered under the hybrid system warranty) out of three Toyota hybrids.

The 2004's battery hasn't failed yet but it cycles daily from eight green bars down to two red bars. The SOC is moving up and down more quickly than in the past, which implies reduced battery capacity.

 

So for those of us who are not the science types and not the math types, and who are new or recently new to Hybrids & Prius specifically, what does this mean in terms of our everyday driving? At lower speeds, say 40 mph and below, can we effectively control the battery discharge? I think this is different from controlling the point in acceleration when the gas engine engages by aggressive take-offs, jack-rabbit starts, or other fuel inefficient practices.

Thanks, TK

 

Any comment/updates on how the above information on prolonging battery life applies to the Gen 3?

 

so by limiting EV mode to max 25 mph, i guess we now know the max safe amperage levels...so how much would that be for Gen 2 owners who can monitor that?

 

Great Info.

Here's yet another little nugget for those willing to add to the great info already in this thread.

Understanding your HEV NiMH battery pack

Cheers;

MSantos

 

This is a interesting discussion with some very interesting information. As almost a total ignorant my question becomes how does driving with an emphasis on extending battery life affect gas mileage?

At some point don't you just have to drive? I mean when you start to apply hypermiling techniques, then look at battery hypercycling techniques at what point are you thinking too much every time you put your foot on the pedal?

I think most people buy a Prius with an eye to MPG and less fuel useage so I can understand hypermiling techniques being adopted to different extents by individual owners, but I'm afraid I'd have to leave battery discharge and maintenance primarily up to the Prius and the computer system itself.

However, in my time observing Prius Chat I've learned that a great number of Prius Owners are very dedicated and technically exacting. So perhaps my question is obviously totally premature, but how different are the characteristics of a Lithium Ion battery? Would the recharge characteristics be so different that we are talking about an entirely different approach, both from a automatic operational standpoint and an ownership standpoint? Is it just too early to know?

 

Speed has very little to do with amperage draw. It is based on acceleration, (F=m*a). So if you accelerate very very slowly up to 25, you pull much less current then if you slam your foot down and get up to 25 in a quarter of the time.

But I think I have read the prius does +/- 120A charge/draw under high loads... Might have seen that in the 70mph EV mode thread in the video with the scanguage. 120A at 220VDC is 26.4KW which is a hell of a draw...

 

This is all very interesting and I appreciate the information about the life of our batteries, although I am perplexed by how we can use this new understanding to maximize the life of our batteries. Does anyone have practical suggestions about things that I can do during my daily drives to ensure that my Prius batteries get all of the life that they deserve?

 

Perhaps I can add a bit based on my own experience and interpretation. Please interject if you wish:

- Minimize the use of extended EV sessions whenever possible and restrict their use only for instances where it is strategically advantageous (maximum distance covered per unit of charge consumed).
- Ensure that the amplitude and frequency of charge discharge cycles remain low. Too many of these cycles will definitely shorten the pack's life expectancy.
- Make strategic use of the air conditioning. Too little use can lead to increased thermal stress in hotter days, and exacerbated use may also cause higher thermal stress too. Seek a happy medium by allowing hot air to escape the car first, then when in motion, set the temps to the highest possible settings while very slowly dialing it down until comfort is achieved.
- Avoid storing the car for more than a couple of weeks without a brief power-up. This is not only because NiMH packs loose a bit of charge with time but so does the 12V battery supporting the 12V subsystem.
- For hypermilers: Avoid chronically static SoC's as these are also not desirable in the long run. Although not as severe as their chemical siblings, the NiMH chemistry is still affected by the proverbial "memory effect". Using a bit of charge now and then is a good thing.
- In cold days allow the system to manage the state of charge even it it means the ICE will run a bit longer. It may seem wasteful and downright depressing to see one's mileage plummet, but the way it works is neither accidental nor without merit.


Cheers;

MSantos

 

Just purchased a 2010 Prius IV solar roof on 7-23-10 and live well under 1 mile from work I noticed a two bar on the charge and at times can get three or four. Need some help here to avoid premature battery failure...What suggestions can you guys give me. Thanks for your time and help.:rockon:

 

do ever need your car during the work day? if so, i would be walking most of the time. (i dont do bad weather and dont expect anyone else to either) or more likely riding a bike. it would not even take me 10 minutes from saddle up to lock up.

if not that, i would definitely invest in a plug in kit.