My 2005 FEH is exhibiting low SOC readings when it sits for 2-3 days and I normally start it up and move it so it has a 12V trickle charger on it. I have seen 03% SOC readings yet, the vehicle starts right up and will charge up to a normal SOC value with the ICE running. Once in the normal range, vehicle operates as normal. Got to get a photo of this low SOC reading. I assume the issue is the aging HVB pack. Still can pull 32-35mpg on the highway at 55-62 mph if there is no significant headwind and normal summer temperatures.

 

If it drops that low and still starts I'm amazed!. Mine drops to 30% overnight lately. I have to make sure and drive it at least every other day. Fuel economy is down to the 26.6 range. Something ain't kosher but I'm not sure what. I would like to sell it and get something newer, but I can't in good conscience sell it like this.

 

Hybrid Automotive's website is down, though the information pages are still available on Wayback.
Looks like the FEH harness is not gonna happen.

 

I will take a photo sometime this week early in the am. A search on this site will reveal a like 11% soc that I posted maybe 10-11 years ago under the word/title "Record low SOC".

 

Started right up without issue: see another thread

 

Hi guys, new to the forum to discuss this particular subject.

My 2008 FEH has been experiencing the same issue described by the others in this thread. SoC will be normal (40-54%) when the car is parked. Next time I start it up, which is usually 15-72 hours later, the SoC will be much lower than it was when I parked it. Usually it's around 28-30%, but I've seen it as low as 18%. The engine still starts fine (albiet a bit roughly), but it drives like a hog until the SoC is back into a normal range, and regen is disabled until the next engine start unless it's a 30+ minute drive. This SoC drop used to be pretty infrequent, but has been occurring more and more often over the past 2-3 years. Now it happens about 25% of the time. I kept logs of it's occurrence for a period of 6 months and found no correlation with outside temperature or other any other external factor that I could think of. It also did not occur with any kind of pattern - sometimes it will go 30 days without doing it, and other times it will do it 3 days in a row.

In February 2020 I went on a vacation for 2 weeks and left the car parked in a driveway during that time. I pulled out the HV battery plug to see if it would still have a low SoC when I returned. And when I put the plug back in and started the car 2 weeks later the SoC had fallen from 53% to a mere 9.2%, which is the lowest I have ever seen it. The engine still started. However the fact that it dropped by over 40% with the plug removed solidifies the idea that the issue is with the battery pack itself.

Has anybody here had any success with re-balancing the pack, with either an off-the-shelf solution or doing so by hand? I am pretty wary of purchasing another used pack from somewhere, especially since there is no guarantee it's not in worse shape than the one I have now, and a new car is not in the cards for me at the moment.

 

Plug has no impact on self-discharge of the battery. The voltage sensing taps sprinkled throughout the pack are the source of the car-related discharge. They are present and connected even when the safety plug is removed.

These Sanyo cells tend to fail first in excessive self-discharge. Once they get to this point, they're generally done. You're fortunate to have the HV jump system available as a last resort. "balancing" is probably not needed since the issue is pervasive - affecting all cells to one degree or another. Grid charging to 100% might be beneficial, but there are no off the shelf solutions. There is a long thread about jump starting a FEH (later models w/o jump start) that would enable you to do it yourself for about $50.

If you're not coding, I would just continue to drive it. For instances where the SoC drops substantially, letting the vehicle idle for 30 seconds while it charges the HV battery may improve life. Periodic use of the the HV jump start (takes 8 minutes) when it's sat for the longer periods may also improve longevity.

The registered version of Forscan is supposed to have a function that forces the vehicle to force charge the battery to true 100%. I've never personally used this, but you can find accounts of it. It's probably a solution you can attempt with minimal $ and no wrenching. I believe it requires you to allow the vehicle to idle for an extended period while it force charges the battery.

 

S Keith, I'm not entirely convinced the problem is self-discharge of the pack. If the pack was constantly and steadily discharging, I would expect the loss of SoC to be pretty consistent from one day to the next. However my experience has been the opposite. Most of the time the SoC only drops by about 0.1 or 0.2% per day. I've left the car parked for over a week before and returned to find the SoC is only 1% lower than it was when I parked it. But sometimes it will drop by more than 20% in less than 8 hours. Occasionally it loses 30% in that same time span. One time it lost 20% after sitting parked for just 4.5 hours. But most of the time the SoC doesn't drop at all. And moreover it has NEVER dropped by only a few percent. It's always either pretty much exactly the same as it was when it's parked, or it's dropped massively, and never anything in between. Indeed I have never once gotten into the car to find the SoC anywhere between 31 and 40%. It's always higher than 40 (the same SoC as when it was parked) or it's at 30% or less. This seems to me more like the symptoms of a bad cell in the pack, or perhaps a sticky relay contact that is preventing the HV battery from disconnecting from the rest of the vehicle when it's shut off. The fact that it drained so much while the plug was removed rules out the latter option. I was considering disassembling the pack and testing the battery modules individually to see if I could find a bad one, but it looks like a hell of a job for someone who lives in an apartment and doesn't have another vehicle to use. Thanks for the FORscan suggestion - I'm going to explore that idea a bit further - it looks like it might be very helpful at further diagnosing the problem and the "force 100% charge" function could be an asset. I did already see the other thread where you very generously outlined the entire process of grid charging it, and will keep that option in mind as well.

 

Large variations in pack temperature can produce significant swings in SoC due purely to temperature change. Is the vehicle's A/C 100% operational?

 

When I first bought it back in 2013 the AC was not working. I bought one of those refrigerant fill kits and refilled it, it worked for the summer and was empty again the next. I did it again and it lasted another summer. On the third summer I use a sealing agent first before refilling it and it's worked fine ever since. Not amazing, but fine. On the hottest days (35 degrees C or 95 F) it is only just able to keep the cabin comfortable with recirculate on.

That said, I'm in Toronto where the summer temperature can reach 35 degrees C (95 F) and the winter temperature can reach -25 C (-13 F). My car is parked outside at work for 8 hours and then is parked 2 floors underground in an apartment complex where the temperature is very stable and rarely is more than a few degrees away from 15 degrees C (59 F). In the spring and fall that's not much of a big deal but in the heat of the summer or cold of the winter the pack is probably experiencing a temperature shift of 20-35 degrees C (36-63 degrees F) twice a day. This alone could explain the problem in summer/winter, but now I'm wondering if these large temperature cycles have had a cumulative degradation effect over the last 7 years of owning the vehicle. That definitely would explain why it's gradually gotten more frequent over the years, but still doesn't explain why the sudden SoC loss is intermittent and occurring in the spring and fall as well.