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I left a door slightly open on my 2005 Prius for maybe a couple of days. I went to start my car this morning and everything is dead -- no lights, no lit security icon, etc.

Could leaving a door ajar cause a dead battery?
 

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It takes a very small current to power up the car. When I did that I got power as soon as I attached the battery charger, and I only have a trickle charger. As soon as it powers up, the high voltage battery provides power to charge the 12 volt. If you're not driving far, you may want to put the charger on it. It takes a while for the 12v to recharge.
 

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A light can be left on even with all the doors locked if somebody, for example a four-year-old daughter, plays with the switches overhead. When it is daylight it is tough to see that a light is still on.

Also, I would question powering up the car from just the trickle charger. I know the Prius doesn't pull a huge amount of power during power-up, but I would at least let the charger work for half an hour to an hour, then take the charger off and see if it will start. tochatihu has said there is about a 10 amp pull when the Prius boots up, so that wouldn't do the trickle charger any good.

If you ever attempt to recharge the auxillary battery directly you must be careful about the amperage it is charged at or you will possibly destroy the battery. In the manual it says no more than 3.5 amps (for 2005), so when I had to recharge one I left it on a 0.75 amp battery tender for about 24 hours.

I also have wondered about the jump point under the hood. If you attach a charger there does it then directly charge the battery, or is there something between the hood and the battery to make sure you're not charging at more than 3.5 amps? So what happens if you use a diesel pick-up to jump-start the Prius? Will the battery be getting 100 amps or so from the pickup's electrical system?
 

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No, there's nothing between the jump terminal and the battery as far as I know. Which has me scratching my head about the 3 amp charge limit, since the DC-DC converter is connected practically parallel to the aux battery and to the rest of the car, so I can't see where there's a current limiter to the battery. There certainly isn't one FROM the battery, since it is fused at 120A.

Well, there is a white sense wire going to the fusable link block at the battery from the DC-DC converter, which is fused at 5A.
There isn't alot of detailed description on the aux charging system and the DC-DC converter though, such as if the S lead is the current limited charge lead or simply to detect the voltage at the battery end, relying on the slight but still finite resistance between the 12V lead from the back of the car to the front.
 

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DanMan32 said:
No, there's nothing between the jump terminal and the battery as far as I know. Which has me scratching my head about the 3 amp charge limit, since the DC-DC converter is connected practically parallel to the aux battery and to the rest of the car, so I can't see where there's a current limiter to the battery. There certainly isn't one FROM the battery, since it is fused at 120A.

Well, there is a white sense wire going to the fusable link block at the battery from the DC-DC converter, which is fused at 5A.
There isn't alot of detailed description on the aux charging system and the DC-DC converter though, such as if the S lead is the current limited charge lead or simply to detect the voltage at the battery end, relying on the slight but still finite resistance between the 12V lead from the back of the car to the front.
DanMan, if I would like to replace the dreaded oem battery with a newer one of different brand and a bit larger AH, what type of chemistry would I be looking for in the retailers shelf? AGM, Gel, Flooded????
Thank you.
 

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Some folks went larger with the classic Pruis, but I wonder what kind of a warranty problem you would have with Toyota with "ANY" type of electric problem you could have from "then on."
Better just be darn carefull with anything using the interior lights and extended absences.
And be darn sure you know where to connect "jumper cables."
 

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Because the battery is in the cabin, most people would require either an AGM or gel cell as a replacement - if it gets crushed in an accident either of these will not spill any liquid acid. Be aware, the battery connection terminals are non-standard, so you would have to deal with that issue as well. An a proper hold-down clamp and venting system would have to be made. All lead acid batteries can vent in certain circumstances, even though they are "sealed". They all have pressure release vents so they don't explode when they do build up pressure.

The charging voltage for the AGM and gel cell are slightly different, but they both change more over temperature extremes, so the difference would probably not be noticable in practical use. Personally, I prefer the AGM over the gel cell type, as it is easier to recover if it goes dead and sulphates.
 

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One should use a sealed 12V battery of at least 35AH, preferably with a gas venting system, especially if the battery chemistry can potentially emit toxic or explosive gases. LA batteries emit hydrogen gas. Sealed LA batteries normally keep the hydrogen contained, but some conditions can cause it to escape the containment, and you wouldn't want to contain hydrogen in the cabin airspace with the potential of being ignited.
 

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You might try one from a Mazda Miata; that battery is stored in the trunk and is fitted with a vent tube so it won't offgas inside the car. Also, I believe it's near the same size, physically, as the Pri 12v battery. The diameter of the posts is a bit bigger (if I recall correctly) however.
 

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Pinto_Girl said:
You might try one from a Mazda Miata; that battery is stored in the trunk and is fitted with a vent tube so it won't offgas inside the car. Also, I believe it's near the same size, physically, as the Pri 12v battery. The diameter of the posts is a bit bigger (if I recall correctly) however.
I replaced mine with the Miata replacement, it is a little shorter in high and the terminal posts are larger; I supplemented the difference with a piece of 2x4 between the chassis and the new batt. case and better cable and bronze terminals. Everything worked well and I'm a happy :) camper again.
 
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