Battery Differences?

I suspect EBH = Engine Block Heater, but see what acronyms get us into?

 

a.s.s.u.m.e.?

 

...lots of assumptions on the site, so it's OK

 

The Tesla's, and Volt, have an active thermal management system for the battery. It cools the battery during the drive and charging, but will also heats the pack when the battery is too cold. The energy it uses during charging is partially made up by the fact keeping the battery at the right temp makes charging it more efficient, and it prolongs the battery life. With typical Li-ion, the battery can be damaged by charging it if the electrolyte is below freezing temps. Batteries are being developed that contain a heating wire that will self power when the battery temp get low.

I don't know if any of the chargers work the way you describe, but I think just timing the charge start so it ends when you are ready to go will give the same result. Plug ins that can precondition the cabin might also prewarm the battery if it is too cold.

They make battery heating pads for starter batteries to use in real cold locations. There are also 12volt electric blankets. Since the traction pack isn't as exposed as a starter battery in an engine bay, care needs to be taken in selecting and installing such, or the battery might get cooked.

 

As I recall, even the Insight-I had a routine to warm the battery up when it got too cold overnight. I can't recall if it aggressively used the battery or discharged it (either way waste heat is generated) but it was a pain when driving for mpg.

Given all the variables of temperature, state of charge, temperature of the pack, etc, I'm not sure how one could predict when charging would finish, and how to do it so that the pack (and the interior of the car) would be at perfect operating temp when it's time to leave. It would be really handy to have program that would achieve this while monitoring all the parameters and charging the pack in a way that would be best for the pack's life. And minimizing electricity usage for those on the grid. Plus some people on the grid get lower rates at certain times of the night. Would be nice if this program incorporated a way to delay charging until the rates are lower.

 

I'm pretty sure the plug ins available now aren't simply plug it in and it starts to charge, but include built in timers of varying sophistication. Some might be capable of doing what you are suggesting.

The NiMH in early hybrids was less hurt by cold, but the battery coming up to temp was part of the warm up period during start up. Comments for an Escape hybrid driver, that uses the same type of cells as the Insight, were that the pack heated up pretty quick, and it and the Insight had a cooling coil from the A/C system to deal with getting the heat out of the pack.

 

Just a noob query from a 1st time near Prius owner. Was actually looking at the Honda Vezel/H-RV hybrid as well.
In Singapore, the 2016 Prius comes with 2 types of battery (NIMH for the basic and Lithium for the Premium models).
Models are expected to be available in Aug/Sept 2016 though.
How does both battery fare in a country with avg temp of 91F assuming the car is parked in an unsheltered car park for say, 4-6 hours?

I was told that the heat may affect the batt performance and life-span.
Is this true?

 

Heat is the enemy with the Gen-1 (2001-03) Prius. Fortunately, Toyota has been working the problem for over a decade.

The Gen-4 Prius puts the traction battery under the rear seat and that should improve heat management. It also has glass and paint designed to reduce solar heating effects. But as a general rule, you want to keep the car out of direct sunlight and have some way to minimize heat accumulation in the cabin. For example, we use 'rain guards' so the windows can be slightly opened without risking a wet cabin if a random rain shower shows up.

Bob Wilson

 

Thanks, Bob. You are right. I was advised to use the rain-guards/visors and leave the windows slightly opened (about 0.5inch opening for all 4 windows) to 'release' the hot air in the cabin. We have 4 seasons of intense summers here. Keeping the car out of direct sunlight is a challenge actually

 

I have long wondered if an external sun-screen held by the windshield wipers might be more effective. Reflective mylar (aka., heat blanket) over a fiberglass backing comes to mind.

Bob Wilson

 

i reckon the best option in my case would be a NiMh based Prius rather than a lithium model?

 

Tough call. Singapore being warmer climate.
We don't even know yet if Gen3 NiMH are going to behave better than Gen2, because so few Gen3 have failed so far. We don't know what Li failure is going to look like because they have been on the market less years. We don't know if Gen4 NiMH will age better than Gen3 which Gen3 have not started to fail much yet.

Best you can do is take a shot at what Toyota seems to be pushing (seems to be NiMH in EU/Aus). Maybe wait to see any short term Gen4 surprises.

 

I thought I read somewhere that Li-Ion batteries degrade over time (rather than use) more than Ni-Mh.

 

If you look in Wikipedia, the list of different types of Lithium battery chemistries is staggering, so I don't see how we could possibly generalize. All of these NiMH/Li batteries need controlled conditions (temp etc) so there is sometimes criticism of cooling/control systems, but I have not really heard a blanket statement about Li batt chemistry aging - actually better if anything at the expense of higher cost.

The main generic thing true about Li batts is some reliance on organic lithium (potentially flammable) electrolyte. Most other batts (eg; lead acid) have a water-based electrolyte.

 

NiMH deteriorate more rapidly with use due to voltage depression induced by short-cycling. This condition can be eliminated via reconditioning, which extends service life, but requires concerted effort that is not typically provided for in normal operation. Age is also a factor. Note that there is a permanent deterioration in potential capacity of 1-2%/year of normal use, so reconditioning can only go so far.

Li deteriorate slower but in a permanent fashion. Their lighter weight allows for added capacity vs. the same weight of NiMH. If you use LESS of a LARGER capacity, you decrease the cycle depth, which increases the number of cycles to failure (longer service life).

 

For reference, AZ has 4 months of >100°F weather per year.

I would tend to agree. NiMH have a sweet spot around 100°F and seem pretty happy up to 120°F, but higher heat does accelerate voltage depression. With what I've seen on the NiMH AZ cars - recovery of 80% capacity after 8 years, 140k miles, I think I would lean towards NiMH.

 

It depends. Apparently some LiON chemistries generate a very small amount of inert material that ages the battery like a tire loses a little bit with each rotation. In contrast, NiMH only moves hydrogen ions around.

In the grand scheme of things, tires wear out and I am OK with battery replacement.

Bob Wilson

 

Me too Bob, replacing a battery in 10 years time is cheaper than buying a new car on which you would lose the cost of a new battery in the first year in depreciation.