Beeping when trying to trickle charge?

Some trickle chargers don't supply enough power to get over the initial current that is required to "restart" the electronics that is on when the car is off. It could very well be the alarm that is tripped as they usually do trip if power is removed then reapplied. Try resetting the alarm with the fob. If that doesn't work, you'll need a charger with more oompf or a good battery to jump from.

It's also possible the brake booster is trying to run for a 1/2 sec. (40 amp pulse) and that WILL overwhelm a trickle charger. Many systems on the Prius will run if they see the fob, without your trying to start the car or pressing the brake pedal. It's designed to "get ready" when it sees the fob. You could also try leaving the fob in the house and applying the trickle charger.

But it sounds like you need a battery or charger with oompf.

 

If you really want to use the trickle charger, then disconnect one of the cables off the 12 volt battery. That way, you can charge the battery without anything drawing down the power.
The fact that you are "head first" in the garage shouldn't be an impediment to using jumper cables, as the battery is in the back. Since you're already accessing the battery, simply attach the jumper cables as you would for any car. It will be a lot quicker than using a 1 or 2 amp trickle charger, and as soon as you get it started, the HV battery will take over charging the 12 volt. Just leave the car "on" and in Park for a while, or go for a short drive.

 

Gene, I think I mis-read your original post. It appears you are trying to trickle charge the battery from the jump posts under the hood, not directly at the 12 volt battery.
Maybe one of the electrical engineers can voice an opinion, but I would think there might be too much resistance in the wiring for a 1 or 2 amp charger to be able to charge the 12 volt battery from the front of the car.
I imagine that you've got the vehicle going by now. What did you do?

 

I had the same issue as described by the poster. When trying to charge through the jump port under the hood I heard the rhythmic beeping/honking. I then got an extension cord and went on to charge the battery directly, which worked fine, without the honking.

 

Well if your 12 volt battery is so low that a trickle charger is struggling with it the battery needs to be replaced. Charging the battery directly on a G2 is very dangerous to your wallet as so many posters have messed it up and caused big damage to the car. It should make little difference charging to the front jump point except its much more safer. I have been trickle charging my healthy battery for over 13 years never ever at the battery itself with no issues.

You are not measuring the battery voltage at the front jump point to see how low it is. It may be completely dead when the battery is completely dead putting a charger on it sometimes does really bad things. Bad things are it pulls alot of initial inrush current creating a surge on the 12 volt buss which is very bad.

If I killed my 12 volt battery dead on my G2 I would not bother charging it I would go buy a new battery as that dead battery will be suspect from here on out as sulphation has begun. It will never be reliable and will never hold a full charge again. Its no big deal on any other car but on a G2 shenanigans with the 12 volts can be very expensive. It is the last thing you should mess with on this car.

If you had a volt meter I could prove my point to you.