12v Battery showing 9.6v after headlight assembly replacement

Well, I would never have thought that was likely either. But it is probably more likely than anything to do with the LED bulbs.

 

If you have a charger of 4amps or less you can charge it overnight, if possible.
That should be enough to revive it. If it doesn't hold the charge, then it would be time to change it.
Since it's only 2 years old, there should be a warranty.

 

Batteries can fail in two years

 

THIS.
Charge it up and pray.
Check the charging voltage when running too (ready mode).

 

Put the car in Ready mode in PARK P mode after you jump-start it for about 2 hours. It should get enough voltage to be tested. Press the Power button 2X and see if the Voltage is stable above 11V. If it keeps going down and below 10V after about 2-3 minutes, your battery is permanently damaged.
If it passes the IGN ON above 11V, turn the headlights on for 1 minute, it should be more than 10V all the time. Those are just the bare minimum before you will get Battery warning CEL.
Voltage reading alone is not enough, Testing it under normal load tells you more about the battery condition. You also can visit Autozone, or Advance Autoparts to get tested by them for free. Just tell them what battery you have and how much CCA is in it.

 

Put it on a charger till the green full light comes on.

Then when done charging and with car off check it’s sitting voltage at the front jump point.
A healthy 12 volt battery should be at 12.6.

Then with car still off turn on the headlights in high beam. Leave them on for
5 minutes. After 5 mins while lights still on measure front jumppoint again.

After that measurement turn the lights off wait a minute and measure again,

what are those 3 voltages?

A healthy recoverable battery should not drop one volt on this test.

 

A freshly charged AGM battery, in decent condition, will display close to or over 13.0 volts, due to the “surface charge” effect. Best to let it rest at least a day, then check.

 

I can't imagine that the LED bulbs are using more power than the original incandescent bulbs. But neither can I imagine that they would have had the lights turned on for much of the time that they were changing out the bulbs. The 12V battery in our 2015 Prius is the original one and has not so far given any trouble (and the car was put into service only several months after it was manufactured, so the battery was sitting for all that time. Would they have trickle charged it from time to time? I don't know).

 

98% they left it on and forgot about it. They jumped it and sent it out the door. I would put it on a battery maintainer like a Battery Tender Jr rather than fast charge it with the car at 50-60 amps.

However ten days later it is probably charged up and these last five posts are just blowing electrons around the internet.

 

I agree with you all, most likely the shop forgot to turn everything off and drain the battery. LED bulb in Prius are often not last long and overrated. Some are indeed good like GTR Ultra 2, Morimoto, SL1, etc. and they always consume less than the halogen (~110 watts). The charging rate from the car is very dynamics and has temperatue compensation too, don't worry about it. You most likely still have warranty on the battery. Very often you can get new replacement under 3 years and prorated after that.

 

Places like detailers, tinters and the like, should get savvy and acquire smart chargers. If they're going to be working on a car for hours, doors open, they're doing detriment to the battery. Maybe even advertise that they use chargers when your car's in their shop.

 

The surface charge usually disappears with any use at all......like opening the drivers door or turning on the headlights for 15 seconds or so.
A really healthy AGM battery should have a no-load resting voltge of 12.8 or 12.9 when fully charged.
Less than that is suspect.

 

Using open voltage/no load is a good first step. After doing REPAIR mode with a Smart charger on a dying battery, we often get open voltage for more than 13V, but the actual battery is still bad. Once we put a load such as headlights On or IGN ON, the voltage will drop below 11V. If we turn everything off, it can not start the car 6 hours later. That was what I observed in my dead 8y old 06 Prius 12V battery.

In my current 6-year-old battery,
Finish external charging 12.5V IGN ON 11.7 V (5minutes test)
Normal usage, 12.3V IGN ON 11.7 V (5 mins)
Repair Mode 13.1V IGN ON 11.9 (1st min) saturate to 11.7 V (from 10-15 minutes)
Conclusion: Aging battery, Still hold the charge, still can start after parking for 1 week, but the capacity is unknown <70%.

I believe that Repair mode does not help normally worn batteries. It may be useful for someone that forgot to turn the doom light for 2 days and cause a new battery to deplete. Repair Mode indeed may help or prevent it from complete death in a recent depleted battery. In NOCO 5, Repair mode charge at a constant 1A rate until reach 14.6V and do pulse charging for 4 hours. This Pulse voltage can be as high as 16.5 V. The slow charge helps in recovering a recent depleted battery, not old/worn battery. NOCO 5 has 3 optocouplers and manages voltage and current rock solid.