Something strange with the HV battery
 

Last night I left the SOC very low when I parked for the night. This morning I was on my usual run I noticed the SOC on the nav screen was showing a charge well after it normally does and the "green" bar was higher, just touching the - + part of the box. I have never seen it this high and after some eving it did not return that high and went back to normal. This morning was very cool for around here, 67 deg. So I wonder if the battery temp has something to do with the allowed SOC limit? John what do you think? By the way I got a longer ev out of the HVB so I dont think the gauge was off.

Re: Something strange with the HV battery
 

If one puts plain old nimh batteries in the freezer and chills them well before charging, they will hold a much larger charge.

I do this for camera batteries often.

MM

Re: Something strange with the HV battery
 

When the green touches the botom of the + sign, you are at 60% SOC, the near impenetrable maximum. You can only go above 53% SOC with regen. If you were ICE charging above 53%, something unusual was going on. Battery temp seems to effect the charge/discharge limits, but not the SOC. I have never seen sub-freezing temps, so I can't really say much about that end of the spectrum. I have had the battery PIDs displaying on my ScanGauge for a few weeks now, and it has really helped me improve my mileage. EV is definitely easier to hold at higher SOCs. Before I was working between 40% and 43%, but now I see this isn't the best strategy for me.

We also had temps in the 60's this morning (first time in 4 months), and I was able to log a 60 MPG commute, starting at 39.8% SOC. I'll post the picture after I download it from my cell.

Re: Something strange with the HV battery
 

Mark, I think I have your answer. But how many miles are you at now?

Every so often, the battery goes through a "Refresh/rebalance/reset SOC" mode. I'm not sure how often this happens, or if it is on an "as needed" basis, or what, but I've seen it twice.

The battery will do an intentional "super charge up" followed by a "super discharge" then returns to normal. This is a type of battery re-condition event. It is also a way for the internal software to measure the heath and status of the battery.

Once at a little past 10,000 miles, my warm engine would not turn off at stoplights, and I noticed it was charging the battery from arrows on the screen, plus I could hear the engine "lug" while the battery icon was 100% green. It charged for 2-3 minutes past 100% green. Then I went into EV mode and I was able to drive for a whopping 6.x miles in residential stop and go conditions. Then everything went back to normal.

Funny you should bring this up! Just last week, at 42,000 miles I noticed the exact same thing happen again. So perhaps it occurs at roughly 10k intervals and I just wasn't paying attention and missed it at 20k and 30k?

-John

Re: Something strange with the HV battery
 

Cold in general is not good for batteries.
Cold reduces both input current and output current ability.
Cold reduces chemical reaction rates, so cold slows self-discharge when you store batteries for extended periods.

Home battery chargers ( for AA / C / D, etc ) are designed to shut off charging when batteries exceed a certain temperature, or current for that matter. By starting with cold batteries, you delay this. But I don't think this is a good practice. Does the battery manufacturer recommend this?
If not, you probably are shortening the over-all life-span. But if a few "big" charges suit your needs better than extensive "average" charges, then go for it.

Re: Something strange with the HV battery
 

I expect this is a calibration cycle for the state of charge program. If so, the battery processor totalizes charge and discharge current and subtracts the sum form the total battery capacity to determine state of charge.

Re: Something strange with the HV battery
 

John I have about 8k on my FEH, but what you described is consistant with my experience, the ev seemed to go on forever. This morning it didnt do it with the same conditions, so maybe it counts charge cycles or its been about 4K since they replaced my PCM. I have been doing alot more eving and have seen my mileage zoom up, but I think I must have experienced a battery refresh.

Re: Something strange with the HV battery
 

Could be either SOC re-cal or battery re-balancing. If it was what John said, then the module delta voltage value would have exceeded some threshold, and the re-balancing routine resulted. If it was what David said, the SOCmax and SOCmin values would have diverged beyond some threshold, indicating that the SOC calculation got lost with a need to re-cal. I originally thought the SOCmax and SOCmin PIDs were to track the SOC, but I think that they actually bracket the SOC calculation.
I have never seen anything but 0 for the delta module voltage on my FEH, but the SOCmax and SOCmin have gotten fairly far apart on occasion. I have never had what Mark described happen to my FEH. The only interesting thing I have noticed is that in the morning after warm-up has been reached, my charge limit will drop to 0 with resultant loss of regen. This happens fairly frequently, but only lasts for a little while.

The PID 493A will tell you exactly what happened, but I don't know how long the bit for the mode would stay set. Probably cleared when the operation is finished.

Re: Something strange with the HV battery
 

Rebalancing of a pack with this many batteries in series requires precise control and a lot of time. Otherwise, the pack can be damaged.

Maybe they do that as a last ditch effort to save the pack if the battery pack does not produce sufficient voltage. The process would have to be engineered to work with interruptions to the process, like when you get to work! And, the process usually requires the batteries to be discharged, then recharged very very slowly for the first phase. If you turned the vehicle off during the first phase, it may not start again!

Re: Something strange with the HV battery
 

The data I have says the re-balance / re-calabrate / reset can take place over several cycles if interrupted like you say, with a key-off in the middle.

Without interruption, the 2 events I witnessed took 15 minutes or less.