My wife's 2010 Prius iv was completely dead this morning when she left for work. Lights were dim, dash would not light up at all. After several YouTube videos, I found that these signs point to the 12v battery being dead. I brought out a jump box to try and get the car to start, but had no luck. I removed the battery from the trunk area and brought it inside to put on my Viking automatic battery charger. I realized after about an hour on standard battery mode at 2 amps that I had screwed up. I had found out that these batteries are agm style. The charger showed that the battery had gone from a starting voltage of 9.8 up to 12.2. I took the battery out to the car to try it out. The car did turn on, but all the dash lights were lit up and the "ready" light didn't come on, nor did the engine start. I brought the battery back inside and set the charger to agm mode at 2 amps. I am worried that that original charge may have toasted the battery. It didn't feel warm when I discovered the mistake and took the charger off. Should I be worried about this and have to get a new battery? Or should it be ok to just try charging on agm mode at 2 amps for a few hours and see if that works?
You should be fine continuing the charge on the AGM setting. At a 2 amp charging current, you will need to charge the battery for about 12 hours or more for a full charge. How old is the 12v battery?
Once you reconnect the 12v battery the car needs to reinitialize the ECU's by pushing the power button twice and waiting for the completion on the navigation screen. Then power off and start as normal.
Thank you for the reassurance. I did charge it up for about 5 hours and it brought mama Prius back to life. Honestly I don't know how old the 12v battery is since it appears to be an oem Toyota battery with Japanese all over it. We bought the car off carvana back in May and it had 83k on the clock. As it sits now there are 99k on it since this is my wife's work vehicle. I have noticed that the prior owner has had the hv battery replaced, but since we have been getting the dreaded triangle of death and check engine light, I assume that it may be on its way out.
Smart battery chargers will lie to you and are notorious for doing what you told it to do, not what you want it to do.... An hour of charge @2A isn't going to give any battery a significant charge. You need to kick it up to 8A and at least 3 hours. That 12.2 VDC reading you got was only a surface charge. If you let it rest for 5-10 minutes and take another reading you probably got it up to 10-11 VDC. Charge the battery @8A for at least 3 hours, then take it down to an auto parts store for a free evaluation/test. If an 8A charge for 3 hours is too much for your battery to handle, your 'smart charger' will automatically dial it back. Money well spent.... Hope this helps....
AFAIK the only diff when charging an AGM battery, is, if it’s spiral style, it “may be” charged at slightly higher voltage. Charging per regular, flooded acid battery is fine though. sounds like you’re using a fairly old charger though? There are some newer smart charger; they’ll run a charging program, then fall back to a maintenance charge level, can be left on indefinitely.
