Spinnaker

I have a couple of battery questions about the 288 volt hybrid battery pack. So far I have not succeeded in getting answers that were anything more than guesses from several dealer service techs and no answers at all from customer service at Lexus Corporate . It's pretty amazing that this information is not readily available given that the hybrid batteries are at the heart of this car.

Here are the questions:

1. After how many months of storage will the total capacity of the battery be compromised even if it is re-charged?

2. Is there any way to keep the hybrid batteries charged other than by driving the car?

The Lexus Corporate website gives only general advice, but not specific enough to make it useful. They say, "..to keep the [hybrid] battery in good condition, drive the vehicle at least once every several months for at least 30 minutes or 10 miles."

In that we are going to be away from home for about 6 months, this is something that would be nice to know. Just to be clear, I am NOT worried about the 12 volt battery (I will put that on a battery maintainer).

Has anyone left their RXh for a long time and can share their experience or any other knowledge?

alaterreur

I dont know if this helps but I went on vacation for almost a month and vehicle started with no problems.. The Hybrid battery was still in the middle and appeared to not move..

Lexmex

I would not know specifically for an RX400h. I have had several friends who use dry cell batteries, like an Exide, Optima or Odyssey, and the have left the car for months and they start up without issue. Not sure about those batteries in the RX though for the hybrid system.

Spinnaker

Thanks for responding. Being a bit obsessive, I've now done some reading of technical literature in scientific journals. Here's the summary:

All battery types (i.e. NiMH, NiCad, LiIon, etc) are distinct in their behavior. The good news is that for a variety of reasons Nickel Metal Hydride batteries are a very good fit in hybrids, but those reasons are not relevant to the question I am trying to answer, so I won't bother to mention them here. However, one bit of bad news is that one NiMH characteristic is a high "self-discharge rate". This refers to their loss of charge while sitting idle -- at 70degrees fahrenheit (depending on which tests you read) NiMH batteries lose something in the range of 1-2% of their capacity each day. At higher temperatures, the discharge rate is higher.

That would mean they lose from 30-60% of their charge each month in storage. Not a problem if you drive the car regularly, but a potential problem if you plan to be away for an extended period. It's clear that being away for 6 months would mean returning to a fully discharged battery.

That may not be a problem as long as I can be determine that sitting fully discharged for an extended period will not damage or permanently degrade the battery performance or capacity. I have only been able to find one reference to that question and that one calls a discharge of 80% (to 20% of total capacity) an "end of life" criterion. It doesn't say whether this is only a caution if it happens to a battery under load, but I believe that is what it means.

So far, still can't determine if sitting passively and discharging in excess of 80% would be damaging. No luck in tracking down the authors of various technical publications yet. These guys change jobs too often!

Nextourer

If it helps, someone over a PriusChat just came back from some station (army). He lives in Alaska and he was gone since May. The HV battery was in the exact same charge (as shown on the screen) as the day he left it.

Spinnaker

Interesting. Can you tell me which thread it's in?

Nextourer

here you go

http://priuschat.com/index.php?showtopic=24177&hl=

Tammy

The batteries would be under warranty, wouldn't they ?

Spinnaker

Nextourer -- took a look at the posting for the Prius -- thanks for sending the link.

I can understand that the battery in the soldier's car may have tolerated a large discharge during storage and still been able to accept a recharge when he returned, but it is a bit of a puzzle why the battery condition indicator would indicate the battery was still in the same condition as when he left. I don't know what this indicator is reporting (i.e. voltage, amperage or estimated amps remaining) but if it is the later, then its reading may have been thrown off by the discharge of the battery. I know this can be a problem because I have a battery condition indicator on a sailboat with a very large battery bank, and it is not reliable under certain conditions.

The report the soldier made that the battery condition indicator showed the battery unchanged from when he left is also inconsistent with the published technical literature that all reports self-discharge at a fairly high rate is a characteristic of NiHM batteries.

It also doesn't square with the advice given in both the Lexus and Toyota websites that say the car should be run at minimum every few months so the battery stays "...in good condition...." Whatever "good condition" means isn't clear, since they don't say - but the message is clear -- you have to run the car or the battery will discharge below acceptable levels in a few months.

At the end of the day, it doesn't now appear as if I can leave this car in storage for 6 months expect to return to an uncompromised battery. If I could get information from Lexus/Toyota that this is not so, then buying this car would be a clearer decision.

Spinnaker

Tammy -- the batteries would certainly be under warranty if they completely failed. But, what do you think the dealer would say if their performance was substantially reduced after a long storage? You might see this in reduced gas mileage (or in some other way) that didn't mean they failed but just weren't operating like they did before you stored the car.

I think the dealer would say, "There's nothing wrong with that battery - it still works." Based on the answers I got from dealer service techs in asking questions about storage, I doubt they would see it any other way. Most of the answers I got were just made up from guesses the techs were making.

Thanks for responding.

HarrierAWD

Just ask your house sitter, friend, family, or neighbor to drive the RX400h once in a while.

Nextourer

The battery indicator he's referring to is simply the battery meter on the screen. In other words, the no. of bars didn't change from when he left in May indicating little or no discharge of the HV battery. It's possible that Toyota is referring to the 12V. I know on the Prius, our 12V is small and can be discharged quickly. I'm not familiar with the high rate of discharge associated with NiMH battery. Granted, I'm neither a chemist nor a physicist so I'm not familiar with the detailed internal workings of different battery types. If I recall correctly, it's Li-Ion batteries that discharge quickly.

http://priuschat.com/index.php?showtopic=23005&hl=
"2006 Prius, less than 300 miles. I left it in the airport parking lot from July 13th thru Sept 4th (that's 54 days). When I got back, the car started like as if I drove it every day. Main battery showed 3 bars left upon startup. I didn't turn off the Smart Key either. FYI."

tod071

ditto. there must be someone willing to start it up

Spinnaker

Getting a neithbor, friend, etc, to help is the obvious answer, and one I had already considered. By the way, Lexus says the car has to be driven for 10 miles or 30 minutes, and not just started and run in place, so it has to be a neighbor who is (1) willing to do this every couple of months, and (2) someone you are willing to have drive your car around, and (3) are confident they will reconnect the 12V battery maintainer when they return the car to the garage. Otherwise, that battery will be dead too.

So I am still where I started at my original post, which asked if there were other ways to charge the battery other than by driving the car -- at this point, I think not. The second question I asked was, if I let it fully discharge, will that compromise the battery?

As to the battery meter, the point in my earlier post is that the number of bars may mean nothing if the batteries have been fully discharged. Devices like that frequently reset to a default 'FULL' condition once the are reconnected to power. Not worth going into the technical details why.

I appreciate all the responses, but I am starting to think I am working too hard at trying to justify buying this car. Maybe conventional gas is better for me right now.

tod071

If you have'nt purchased the car yet, why don't you pick it up after your 6 month trip. Otherwise, you're probably right by going with a gas RX, especially if you'll be on more trips in the future.