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8) Has any one had experince with the 12 volt battery discharging while the car is sitting in the garage for many weeks with out being the car run? I understand the small battery in the trunk that has to maintain the computer system will completely dischage over about two weeks if the car is not run to charge it up.
 

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This fear is much exaggerated. I've left my '02 for longer than two weeks with no adverse effect on the 12v battery. But to allay your fears, I'll repeat this advice: go to that big-box store whose name rhymes with "all-f*rt" and buy yourself a Campbell-Hausfeld rechargeable cordless tire inflator, model no. CC2300. With this device you can jump start the Prius through the "cigarette lighter" outlet (modified at the fuse box with a $5 kit from http://www.coastaletech.com ), and also keep your tires inflated to their proper pressure (42/40 in the case of the OEM Potenzas. NB: this differs from Toyota's 35/33 recommendation!).
 

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I have had considerable experience with 12 volt automotive batteries in vehicles and equipment that sometimes sit idle for long periods prior to use. I personally prefer solving problems through prevention rather than fixing it afterwards. There is an engineering basis for my choice. The lead acid storage battery will remain healthier if maintained in a charged condition and not allowed to self discharge or be run down by various loads.

In my case I have some pretty sophisticated and extensive alarm systems which even on a diesel truck with parallel 100+ amp hour batteries will run the batts down in a relatively small number of weeks especially in cold weather with low batt efficiency.

There are battery maintainers about the size of the plug-in-the-wall power supply for cordless phones (some are larger) that plug into a standard wall outlet and attach to the batery or convenient connecton point. These are designed to prevent long term self discharge or discharge from alarms, computers, whatever... Some of these are designed to mount near the battery and remain connected all the time. In use, you connect an extension cord to the unit's short power cord when you park the vehicle and disconnect before you drive away.

In self defense, I mounted one of mine so that if I forget to unplug, it will unplug itself harlessly as I drive away. On another vehicle (street legal VW dune buggy) that gets used infrequently I installed a maintainer of a different design. It plugs into the wall like the afore mentioned power supply. I have a quick disconnect plug and socket (Radio Shack for a buck or so) to use to hook up the cord from the maintainer to the car. I have leads permanently attached to the battery cables in the car. I located the plug and socket where it was convenient to get to but not in the way and it too will "auto-disconect" if forgotten and the vehicle is driven away.

These maintainers are not designed nor capable of effectively charging a deeply discharged battery. They are to keep a fairly well charged battery at full charge for an extended period of time without damage to the battery. Most common automotive type battery chargers will damage a battery if connected for extended periods of time.

These battery maintainers are commonly available where automotive accessories are sold such as your FLAPS (Friendly Local Auto Parts Store), JC Whitney catalog or web site, farm/ranch supply stores, etc. I have found them for less than $10 and as much as about $25. I have not noticed any problems with the cheap ones or the more expensive ones. I have used them on small batteries (chipper shredder) all the way up to parallel diesel truck starting batteries with excellant results and nary a problem. They are specifically designed for long term connection and do not "boil" out your electrolyte like many regular charges can, if left connected for extended peripods.

I even use one to keep my moms emergency lighting system battery (deep cycle 100 amp hour maint free) fully charged. It stays connected year round.

I'm not knocking the portable jumpstart battery thingy. They are extremely handy! They will probably work for what you need but they just aren't my prefered approach for the stated reasons above. I have both. If you don't have a screw driver, you can drive a screw with a hammer but I recommend the right tool.

:D Pat :D
 

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Dead battery recovery 2001

Went away for 3 weeks and came back to a dead prius.
Boosted the battery and she started but the display said to return to dealer and did not seem to enjoy life.
Overnight she discharged again.
Read the manual which instructs to boost by attaching to the positive terminal, and for the ground to the closing hasp of the lock that secures the trunk lid.
This worked just fine, and she has behaved ever since.
SO IT IS IMPORTANT ON BOOSTS NOT TO USE TH BATTERY NEG TERMINAL BUT A PROPER GROUND TO THE CAR BODY... I don't why, but may have something to do with resistance to the principal battery?

Jim
 

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Re: Dead battery recovery 2001

Jim Johnstone said:
Read the manual which instructs to boost by attaching to the positive terminal, and for the ground to the closing hasp of the lock that secures the trunk lid.

SO IT IS IMPORTANT ON BOOSTS NOT TO USE TH BATTERY NEG TERMINAL BUT A PROPER GROUND TO THE CAR BODY... I don't why, but may have something to do with resistance to the principal battery?

Jim
Jim it is an important safety consideration on all vehicles/equipment that when "boosting"/"jumping" a battery that you not hook up the last connection made to the battery post. For example: After ensuring that the clamps aren't touching each other at one end of the cables, you can attach the other end to the "donor" battery posts. Then, and this is the critical safety issue, attach the positive clamp to the positive terminal of the "recipient " battery A N D then attach the remaining (last) clamp to a good ground, AWAY FROM THE BATTERY! This last part is THE CRITICAL ISSUE.

Sparks are always made when you make the last connection (complete the circuit.) Lead acid batteries, deep cycle, regular old fashioned ones, or maintenance free can and do emit hydrogen gas which can be ignited by the sparks from making the last electrical connection. If the hydrogen gas is ignited, it can explode with enough force to rupture the battery and spray you and the surrounding area with the components of the battery which include lead, lead compounds, strong sulphuric acid, and the battery case materials, etc.

NEVER NEVER NEVER make all the booster connections direct to battery posts. Make the last connection be to connect the ground (negative) to a good ground point AWAY from the battery.

In my even more ignorant past I didn't follow this safety rule and didn't blow up a battery but that does not imply I was safe. You can walk across the street without looking for traffic and make it but if you keep doing it, tragedy will result. I did weld too near a battery once and an errant spark(s) went by the vent caps, ignited the hydrogen and blew out the vent caps. They smacked into the ceiling 20 ft overhead. It was just dumb luck that the fuel/air ratio was not right or the resulting explosion would have been much more spectacular. Sulphuric acid at normal battery concentrations can blind you faster than you can get first aid, even if it is handy and someone administers it to you immediately (you won't be able to do it for yourself.)

Sorry to run on but I would hate to think someone got blinded and disfugured because I was afraid to make a full explanation.

:D Pat :D
 

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Trickle Charging battery with solar panel

Has anyone tried using one of the small solar panel trickle chargers? They seem to be prevalent in the RV industry. I use two that are approximately 4" x 12" each plugged into my cigarette lighter outlet to keep the batteries on my motorhome charged up. Without them the slight discharge of various electronics runs the battery down in about two weeks of non-use, necessitating a jump start. Obviously, this will only work for vehcles stored outdoors. Hope this helps.
 

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Sev, It is easy to buy or make an extension cord for the solar chatrger. With an extension cord you place the charger in the window of your garage. You could roof mount it but they you'd need separate units for home and away. If that isn't possible you could use one of those portable battery booster batteries,

My experience with motor homes is that you need more than one battery anyway so one can be isolated (diode type isolater) or a simple knife switch and will not run down when parked. If yoiu put a knife switch on the starting battery it will protect it against discharge.

The worst case I have had is starting the aux generator from its battery to charge the engine starting battery. Now I have a solar farm on my motorhome and camper 12-14 amps in full sun. Still I use a plug in battery maintainer when parking indoors for over a week.

:D Pat :D
 

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Battery cut-off switch

If you want to make it easy to disconnect your 12v battery, check out your local marine or RV parts dealer or catalog (e.g. West Marine, Boat US, etc.). There are switches made for easy disconnection of low voltage/high current electrical circuits.
 

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Solar battery trickle charger

A solar battery trickle charger can help prevent the 12 volt battery from discharging. A number of manufactures do make solar battery trickle chargers. They come in a varity sizes and styles. Some come with a standard 12 volt automotive plug on the end. Others have lugs or clips that attach directly to the 12 volt battery. It's important that solar panel be placed in direct sunlight for it to work. Note window tinting does reduce the intensity of the light hitting the solar panel. Reduced light intensity will reduce the electrical output of the solar panel. Clowdy weather will reduce output also. Snow cover blocking light from hitting the solar panel will likewise have the same affect. Note: That indoor lighting is not intence enough to charge the battery

:idea: Besure and get one that is designed to work inside a hot car.
1.5 Watts is very small power output.
30 Watts is a good size for battery charging.
I have not done the math and calculated how large of a panel it would take to keep the Prius batter charged. But by adding one it will exstend the time the Prius can be parked.

Radio shack does sell Solar Batter trickle chargers. You can check these out on thier web site. http://www.radioshack.com

Since i do not own a Prius yet. I don't now it the 12 volt power socket(ciggarret lighter) stays on when the car is parked. If it does power down. connect the solar charger directly to the battery. Radio shack doe make a adapter with battery clips that attach to the battery directly. It has a automotive style 12 volt jack on the other end. Catalog number 270-1527.
I only use Radio shack as an example because they seem to be everywere.
Other retailers may have better prices.
 

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5 Watts is very small power output.
30 Watts is a good size for battery trickle charging.


I unfortunately strongly disagree with the above statements. Trickle charging, by definition, is charging to offset inherent charge losses within a battery and/or to overcome small charge losses resulting from milliamp quiescent current drain from onboard computers. Most vehicle manufacturers design their vehicles such that no more than 200 milliamps of quiescent current is drawn from all onboard devices with the ignition off. Charging with more than 300 milliamps may result in excess current being supplied, which has the effect of boiling the acid, causing evaporation, and ultimately battery failure. 5 Watts is what you want, resulting in about 300 milliamps of charge at 13 volts. 30 watts would result in more than 2 amps of charge current, enough to damage the battery unless a charge limiter is in place. I see no charge limiters on the average car solar chargers, those offered for about $50, just an assumption that the sun does not shine 24/7, thus the average charge over time is generally acceptable. The small Prius battery will be very easy to overcharge since its capacity is smaller than a standard size car battery.
 

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I got the numbers current draw from the battery, and battery capacity.

The battery capacity is 28 amp hours.

Current draw headlight switch off and car off is 0.036 amps.
28aH/0.036amps=777.8 hours
777.8/24hours=32.4 days

Current draw headlight switch on and car off is 0.047 amps.
28aH/0.047amps=595.7 hours
595.7hours/24hours=24.8 days

These number hold true only for a battery that is fully charged, and brand new. But as a battery gets older its storage capacity decreases.
This just proves that after 32 days the car will not start.

So a battery that is less than 1 years old will probably start a car that has been parked for 21 days or less. A battery that is 3 or 4 years old may not.
Now for picking what size solar charger you will need.
0.047amps*24hours=1.128aH

A 5 watt solar charger output is 0.350 amps.
Average sun hours for wisconsin 4 hours.
0.350Amps * 4 hours = 1.4aH
California is about 5 sun hours.
:idea:
This is fine if the panel is mounted on the exterior of the vehicle. But because of the High Solar Energy-Absorbing glass solar energy entering the Prius is significantly reduced. It's because of this that a 5 watt solar charger may not be able keep a charge in the battery. Put will exstend the time in between engine starts. Chargers over 8 watts should have a charge limiter or charge controller. Some of the better solar chargers have them built in.
 

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Looks like the site that used to sell the cigarette lighter mod for the earlier model has disappeared. I was hoping to see a new model for '04 Prius.

Ideally I'd like a 5 watt solar panel with cig lighter plug and just plug it in without any fanfare. Without the fuse mod, I would have to connect direct to the jump post under the hood.
 

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The 12v power outlets (aka cigarette lighter outlets) in the Prius, both the classic and the 2004, turn off when the car is off.

There is this mod for the classic Prius, to always have the outlet "hot":
http://www.coastaletech.com/powermod.htm
 

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Toyota solar battery charger

Toyota should offer a solar trickle charger as a after market add-on. It could clip on to the dash, or in the rear window. This would solve the long term battery discharge problem. :idea:
 
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