Here is the story

I left the overhead passenger light on by mistake since last Friday night. I was sick for the past couple of days and I didn't use the car at all. Finally last night I tried to get the car to the pharmacy which is 0.25 miles away and I realized that the car was dead. No battery juice at all. Finally I managed to recharge the 12V battery with a booster charger. This process took about 4 hours. I estimate that I got about 60-70% charge back to the battery.

I put the battery in the car. I drive around until I get about 4 bars in the IMA battery. I drove about 20 minutes total around town to recalibrate the computer. Today I start the car and I see that the IMA battery has dropped from 4 bars to 0 bars. When I started the engine the charging mode was enabled until I got 2 bars about 2-3 minutes later(I was trying to enter the Unlock code for the radio and reprogram the time and the stations). Then I used the "Forced charge" mode(rev the car at idle at around 2k RPM) and I got about 3-4 bars.

The only issue I could say it that I only drive the car during the weekends and I might make 1-2 very short trips per week. So to say the car has been sitting allot.

I just want to find out if this looks like an expected behavior. I hope that I do not have a more serious issue at hand. Any feedback on this issue will be greatly appreciated.

Thanks in advance.....

 

12v is only needed to boot up the ECU. once the engine is running, the system will charge it up nicely.

If you're this concerned, get a small trickle charger and wire it in so you can leave the car plugged in with the battery topped off for peace of mind.

 

This past Saturday I had something similar happen. When washing my car, I let my kid play in it. After I was finished washing the car, I took my kid out, locked the door, and went inside. Three days later, I went out to drive the car but couldn't get the keyless entry to unlock the door. I manually unlocked the door and the first thing I noticed was the instrument cluster lights didn't come on. Looking around the car, I see the overhead light was left in the on position.

I put a trickle charger on the battery and after a few hours the car started right up. Of course, the computer had to reboot and the GPS took 5-10 minutes to reacquire a signal. The SoC indicator had no bars and the car started to regen with a few bars of green right away. After two bars appeared on the SoC indicator, the regen stopped. All that took about 5 mins. And as expected, the car ran normally after that.

 

Okay, update to the problem I had with draining my 12V battery.

Apparently, the 12V battery didn't like being drained down by leaving my overhead light on for three days straight. I had put it on a trickle charger, and it worked fine since then. But today, it just wouldn't start! I took it to the dealer and they replaced the battery for free. If I recall correctly, the factory battery has a 36 month free replacement period and pro-rated up to 100 months. I felt a little guilty letting them replace the battery under warranty, knowing I caused the problem. But not guilty enough to tell them not to do it!

I've got to say, Arrowhead Honda in Phoenix really impresses me. I've always had good dealings with them. From purchasing two vehicles from them, to servicing and maintaining both of them, I've always been happy with the service I receive. Anyone in the area, if you want to buy or maintain your Honda, rest assured Arrowhead Honda will take very good care of you.

Case in point: after getting my car started this morning around 8:30, I called the service department and asked about the battery warranty. The service manager told me about the warranty and said to bring the car in. His first available appointment was at 3:30, which I booked. Around 11:30, I got a little anxious about my 3:30 appointment because I had another appointment at 5:00 quite some ways away from the dealership. I drove over to the dealership and turned my car in at 11:54. I let them know I was early and that I'd wait if they could work me in between appointments. They actually had a tech open and took my car back right away. Sure enough, at 12:23, my car was ready to go!

 

bar10dah

Interesting you just had your battery replaced as I replaced mine about 30 days ago and have been holding back my observations till I was SURE about what I am seeing.

My battery was good enough but it tested weak on various testers at auto shops. Only reason I had it tested in the first place is because I changed out my battery in my other car which was weak and before taking the new battery I had the guy test the one of the shelf to be sure it was good per his test set. The first one we grabbed was NOT ! Anyways, while he had everything out, I asked if he could wheel the test set out to the hah and he did, it said 'charge and retest' I charged it, the charger said FULL in a couple hours but left it on over nite. The charger was HOT unlike it is with a normal battery (normal meaning not bad battery)

Anyway, long story short, the battery still failed and I bought a new one.

What I am noticing is unreal. My IMA is super active now just as I would have expected. I see assist the way I would have expected it to be.

Before the replacement I would rarely see any assist at all.

This result is not from disconnecting the battery for a bit because I had done so in the past with no such results other than the ima battery recalibrating itself.

The mpg is up and I will know how much more up it is because we are taking a road trip this Sat for a week.

This new battery is like the entire car has be reprogrammed.

My hunch is that the traction battery was occupied keeping the 12v battery charged to its liking which seems to have taken priority over ima assist.

Hope you have the same good results.

 

I haven't noticed anything like you have, so far. But, I've only put maybe 30 miles on the car since the battery replacement. I'll try to keep a better eye on things to see if there are any noticeable differences in how the car operates.

 

bar10dah,

I tossed and turned all nite and hoped I would remember to comment on this in the morning, and I DID.

Perhaps the difference in my battery swap is that I pulled the battery and did not use one of them memory minder devices to keep all the settings in the radio and probably in the ECUs too.

Even though I disconnected my old battery a day before replacing it and reconnecting it, I only witnessed the battery recalibration process, not the exciting amount of Assist I now get.

MPGs in town are up and we will find out on the road trip which starts later today, about 900 miles worth of trip.

Anyways, my idea was, IF YOU KNOW your radio security code, consider power cycling the system, but as with anything here, at your own risk,

 

Thanks for the info, Tony. When my battery was completely dead a couple weeks ago, I did have to enter all my security codes. After putting the battery on a charger overnight, I didn't notice any difference in the way the IMA worked. But, like you said, when I did have Honda pull my old battery and put the new one in, they probably used a memory device to keep voltage in the car while doing the swap. I'm not really too concerned about going through the trouble of resetting the ECU. So I won't be pulling the power anytime soon.

Good luck on your trip! Definitely post your mileage when you get back.

 

Made it to my destination. averaged 38.7 for a total of 970 miles at mostly 72 miles per hour. In the past, I was having difficulty getting a constant 34 hiway mpg.

Car was loaded to the gills too. I carry a spare in my 05 which weighs nothing in comparison to the baggage my wife packed.

I am expecting same or better mpg on way home.

 

I've got a question.. Does a hybrid car have an alternator?? If so, then the alternator would be the problem if the batteries act awkward..