recharging 12v battery

[chabor]

I have a dead prius (left the door open for 4 days). I need to recharge the 12v battery. can i do this from the jumper posts, or do i need to connect directly to the battery. when attaching the charger to the jumper posts, it lights up the whole car. fans come on, things beep. not sure if this is normal. any guidance would be appreciated. thanks.

[David Beale]

Yes, you can recharge the battery from the underhood posts. The lights etc. come on because the computers are confused as the power was off. Just make sure you have a good ground connection for your charger, and that it's not a really cheap charger. The cheap ones have a "noisy" output, and that can also confuse the computers.

You don't have the fob plugged in do you? Perhaps you left the car on and it still thinks it's on. Try turning it off. That may stop the lights, beeping etc.

[chabor]

Thanks for the info. No, no FOB plugged in. It may have been detecting it as it was in the room above the garage.




<div class='quotetop'>QUOTE(David Beale @ May 19 2007, 12:03 PM) [snapback]445707[/snapback]</div>

Yes, you can recharge the battery from the underhood posts. The lights etc. come on because the computers are confused as the power was off. Just make sure you have a good ground connection for your charger, and that it's not a really cheap charger. The cheap ones have a "noisy" output, and that can also confuse the computers.

You don't have the fob plugged in do you? Perhaps you left the car on and it still thinks it's on. Try turning it off. That may stop the lights, beeping etc.
[/b]

[Bill Merchant]

Once you connect 12V under the hood, you should be able to start your car, since the 12V battery is just used to boot the computers and close the main relay. Once your car is running, it will charge the 12V battery in the back. Note that a drained 12V battery may never be the same, so you may want to start doing some research for a replacement, should you need one.

[Mkappy]

My previous auto (a 2003 VW) came with a solar 'pad' to keep the battery charged when VW was not being driven for an extended period( eg Airport parking, etc) When I traded the VW for the Prius I kept the solar panel. It uses the power port to 'trickle' charge the battery. Question: can I use it with my 2008 Prius?

[Patrick Wong]

Originally Posted by Mkappy

...When I traded the VW for the Prius I kept the solar panel. It uses the power port to 'trickle' charge the battery. Question: can I use it with my 2008 Prius?

The 12V aux power sockets are disconnected when the car is IG-OFF so the solar panel charger will not help. If you want the charger to be useful, you'll need to modify the circuitry so that the power sockets are live at all times.

[jelloslug]

Make sure to not set your charger at too high of a current setting. I was able to recharge an utterly dead 12v battery with my charger set at 2 amps. Anything higher than that and you risk overheating the battery. It took several days to recharge that battery.

[litespeed]

I have used a " Battery Tender " on my motorcycle for 3 or 4 summers ( I am gone for 3 months or so) with excellent results. The smaller model has pretty low output..and my mc battery appears to be much smaller than the Prius 12V. Anyone have an opinion on Battery tenders for the prius for long term storage ? I take delivery of a 2008 Prius in a couple of weeks.

[tigerpilot]

I think the Battery Tender is one of the better chargers out there. I use mine for all me 12 volt batteries. The output is 1.25 amps until the battery reaches a 'full charge voltage' and then it goes into a maintenance charge that will NEVER overcharge the battery. I think the Prius battery is about 26 amp hours. If this is true it shouldn't take more than 24 hours to charge a discharged battery. Remember that the Prius is drawing current for accessories all the time you can't go wrong using a Battery Tender for storing the car extended periods. I think they cost about $50.00
for the regular model.
Regards, Don

[WayneF]

Re: maintenance battery chargers

FWIW, I have this one ($29) which works great:
Amazon.com: Schumacher SEM-1562A 1.5 Amp Slow...
A good leading brand, and the manual is here:
http://manuals.batterychargers.com/m...-99-000402.pdf

Page 3 says it charges at 1.5 amps until 14.4V and the current has fallen to 1/2 amp, and then it drops off to maintain 13.2V forever at only milliamps (or until the current might increase to 1/2 amp, when it starts over again). My own voltmeter measures it at 14.5V and 13.3V, which is possibly my meters problem.

The Prius is said to charge the 12V battery at 3.5 amps. Which is not very much for a ten minute drive, compared to alternator cars. So in my case, driving habits of only short trips in town with Smart Key (a continual discharge 24/7) resulted in the battery always being only about 12.4V, which is only 50% charged... which causes harmful sulpherization, which is harmful to the life of lead acid batteries. I turned off Smart Key because of too many short trips, too many days apart.

Just be extremely careful to connect Red to Red when connecting it in the fuse box, else it is said to be a very expensive repair if reversed.