12V Battery near-dead after charging HV battery :-(

Here are my results...

I took my PiP (2014 March production, E.U. model, Executive trim) for a ride, came home with 6.6km (4.1mi) EV estimated range left. I wired amp-meter in serial with 12V battery in the trunk. The voltage readings were made at the terminal under the front hood. The car key was in my pocket all the time. The measurements were:

1. The car is off, cabin and trunk lights off, only rear trunk open: 12.8V/1.15A
2. I put amp-meter so I could see it thru the window and closed the rear trunk: 12.8V/0.09A, 0.01A a few minutes later
3. I opened the charging port: 0.03A
4. I connected the L2 charger: behold 13.6V/-5.5A. Yes, the PiP started pushing the current back to the 12V battery. It's charging it!!! Current dropped to -2.5A after a few seconds, T+1min=13.6V/-1.8A, T+5min=13.6V/-1.44A, T+10m=13.6V/-1.24A, T+15m=14.7V/-0.72A, T+30min=14.7V/-0.22A...

 

Nope. Won't happen.
The battery itself, if it is a conventional wet-cell type will not be above 12.8.
An AGM might read 13 but most won't.
No car battery "should be" above 13 volts.......unless it is connected to a charger at the time.

 

It sounds like your charger isn't working right and if that's been going on long enough the battery might now be shot too.
Have you checked the battery voltages with each of the chargers in use ?
Does it show a similar drop ?
Anyhow, if you don't fix the underlying problem, the new battery won't last long either.

 

hummm,
I noticed in your initial post ( see step 9 ) - when my HV battery is finished charging and I plug the car in again, it wouldn't start charging again. Why is you car charging again after your car has finished charging, even if for only a few minutes? Did you actually use the car in READY mode for a short period of time before plugging in a second time?

Another thing you can do while plugged in is to put the car in ON mode by pushing the START button twice without your foot on the brake.
Then look at the HSI for the charging session. If your car is like mine the ON mode will stay on for 10 minutes than shut off as charging continues.
You can put the car in ON mode as many times as you want while plugged in and charging.

You can also try running the a/c while plugged in, but since it is getting colder outside you have to make sure the the a/c temp setting is lower than the outside air temp for the a/c to start

 

good catch, when my car finishes charging, if i plug it back in again, the light comes on for a couple seconds and shuts off. just enough to taste the full battery i suspect. i don't know how long it would have to start charging again, more than a day i suspect.

 

Hello,
Been following this thread so I just went out to my car and put a voltmeter on it and it reads 12.4 volts. This is after having the battery tender plugged in all night. I also checked the voltage when being charged with L2. The reading was 13.4v after just a few seconds.

 

Never the less, your 12V battery is finished after all that has been happening to it lately. You'll have to buy a new one any way you slice it.

What if your 12V battery simply takes too much current to charge, PiP notices that and disables DC-DC charger to prevent overloading it. Maybe with a new battery, everything will get back to normal. However, do have 12V battery tender ready and monitor the voltage closely for the first few days.

If the PiP still doesn't charge it, put the old battery back, take the car to the dealer & charge the new battery back to prevent sulfurization.

 

There is something wrong with this picture.

After being connected to a good tender all night, your battery should read considerably more than 12.4......IF the tender is still connected.
Reading only 12.4 might indicate a bad charger or a bad battery.

If it reads 12.4 after the tender is disconnected, it might be normal depending on what electrical state the car is in at the time.

 

Its definitely toast.

 

Might not be the case if his battery tender is the same as mine. When I connect mine to my motorcycle it does a quick test to see, the battery is still OK, then it falls to sleep mode. Then wakes a few hours later, does some other stuff I don't actually care what it is... The case is it is definitely not trying to keep the battery at 100% 24/7. Since I have this battery tender, I didn't need to replace the battery ever again.

 

If the battery is sulfated, there may be a short inside a cell. Trickle charging won't resolve it; it only charges it up briefly, until the internal short brings the voltage back down again. The frequent low-voltage condition also adds to the sulfation problem and could create a battery-killing short at any time. A high-amperage desulfating charge may be a remedy, but often with these automotive cells, replacement is the best option.

 

From: Battery Sulfation : Technical Support Desk

"When hard sulfate is present, the battery shows a false voltage, higher than it's true voltage, fooling the voltage regulator into thinking that the battery is fully charged. This causes the charger to prematurely lower it's current output, leaving the battery discharged. Charging at a higher than normal voltage and low current may be necessary to break down the hardened sulfate."

 

good diagnosis, all the best! this is the second or third bad charger i think.

 

This is normal behavior. Quoting Toyota,

"When charging, the auxiliary battery voltage is lowered to the limit of the control range (13.5 V) in order to reduce the current applied to the accessories and auxiliary battery."

The HV charger applies voltage to the 12v battery to run the fans and energize the SMRs - this is the 4-5 amp draw you are getting.

Also per Toyota,

"DC 13.5 to 15.0 (normal condition)

DC 11.5 (plug-in charge activated at low temperatures)"

When charging when cold, the system also lowers 12v charging voltage to prevent damaging a cold battery.

So I think your car is AOK.