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Discussion Starter #1
There was some talk a while back on one of these forums about using a battery-powered tire inflator from Walmart to jump-start a Prius with a dead accessory (12V) battery. For reference, it is a Campbell Hausfeld CC2300. As I recall, many people said it should work, but no one had actually tried it. So I did.

I disconnected my accessory battery positive terminal (to simulate a dead battery), and connected the tire inflator's power jack to the battery harness with clip leads. I put a current meter in series with this circuit to measure the current drain. Here is a rough sketch of my layout: (pardon my crude textual "graphics"--display in a fixed-width font)

.from chassis to negative terminal........
.|........................................
.|.....from relay block to positive terminal (lifted)
.|.....|..................................
.|.....|.___________________.___..........
.|.....|/...................|Adc|.current.
.|..__________......________|___|.meter...
.|./..........\.....|.....................
.|/............\.../|\....................
.-_____+........\__|||.tire inflator......
.|.12V.|...........|||.male-to-male.......
.|_____|...........|||.power cord.........

Here were my measurements over time, with notes about what was happening:
1. Started by unscrewing the cable (the part containing the fuses) from the positive terminal, lifting it from the battery, and connecting my inflator/meter. The inflator was off, so the car was dead (trunk light off), and the meter read 0 A.
2. After waiting at least a minute (so any capacitors could drain), I switched on the inflator. Current spiked to 1.44 A, immediately dropped to 0.80 A, and (after about 10 sec), dropped to 0.35 A. (This was presumably the current needed to light the trunk lamp and the standby electronics.)
3. Opened the driver's door. Current increased to 1.43 A (to run lights). Car appeared operational.
4. Inserted key. Current spiked to 1.69A and immediately returned to 1.44A. (This may have been the immobilizer system querying my key.)
5. Turned key to ACC. Current increased to 3.14A for about 5 sec and then dropped to 3.05A (multi-display was the only thing on).
6. Turned key to ON. Current increased to 6.69A for about 5 sec and then dropped to 4.15A.
7. Turned key to START briefly and returned to ON. Car started normally. Current spiked to 6.9A and then immediately went to -2A as the 273V battery began recharging the 12V battery (i.e. the tire inflator). This negative current slowly dropped as the inflator recharged. After several minutes, it had dropped to 0.65A.
8. Switched off the inflator (0A). The car continued to run normally, confirming the fact that the 12V battery is unnecessary in READY--the 273V battery runs everything.
9. Turned key to ACC. Everything went dead.
10. Re-connected 12V battery. Everything worked normally again.

Not surprisingly, my radio preset stations were lost. However, I was surprised by some of the other artifacts. Here is a list of things I noticed upon re-start:
1. Radio Preset Stations were returned to factory defaults. (The tenths were all odd--I thought Japanese FM radio stations used even tenths.)
2. Clock retained the time, but apparently didn't "tick" when the 12V power was off, so it lost a few minutes.
3. Average MPG and distance were retained.
4. Trip odometers A and B were reset to 0.0 mi.
5. The first time I turned the key to ON after power was restored, the outside temperature readout was in Celsius. I turned to START and it changed to Fahrenheit. I never saw Celsius again.

Conclusion: The tire inflator is a great way to jump-start your accessory battery, but don't leave the key in ACC or ON for long before turning to START.

Does anyone have questions or comments to add? In particular, can anyone suggest why some parameters are apparently stored in Flash or EEPROM but others are retained only in RAM?

Douglas (2002 Silver, Wisconsin)
 

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As a side note, If you have a nav. system it will probally reset the settings to the factory defaults, but keep your stored points. (This includes setting the dreaded avoid toll roads routing option).

It is also a handy way to get your nav. system back from metric to english. I had someone do this to me recently playing with the language settings.

I am surprised that the Average MPG and distance were retained ... Both times my system was reset they were not.

Kevin
2002 Moon Blue Pearl 11K miles 5 months
 

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Discussion Starter #4
It won't work without modifications, because the accessory outlet is not connected with the key OFF. When you turn the key from OFF to ACC (or ON?), the 12V battery is used to flip a relay which provides power to the accessory outlet. So, you cannot use any rechargers or jump-starters which rely on a cigarette lighter. Of course, you can modify your accessory outlet to be always on (http://www.coastaletech.com see Power Outlet Mod) if you want to be able to do this. But, be careful not to leave accessories connected for long--the 12V battery will discharge quickly with a minor power drain. (BTW, I thought it has a 10A fuse?)

Douglas (2002 Silver, Wisconsin)
 

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Darn it, that means I cannot use a "trickle charge" solar pannel with the ac outlet? There are ones that fit on the dash and are supposed to keep a battery charged in a conventional car. I wonder if it would add power if you have a device like this plugged in while driving?
 

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Discussion Starter #6
A solar trickle charger will only work if you modify your accessory outlet or wire it directly into the 12V accessory battery. And, it is only useful for maintaining charge in the 12V accessory battery (i.e. when the car is off). It will not provide power for driving, because of the voltage difference. You would have to get two dozen of these little 12V panels and wire them in series to get enough voltage (274V nominal) to provide power to the drive battery. And, of course, you'd have to wire into the high voltage system (orange cables). Few people want to mess around in there; although, I recall hearing about someone who wired an extra lead-acid battery array in parallel with the 274V drive battery. Apparently this was successful at increasing the time he could spend in stealth mode.

Douglas (2002 Silver, Wisconsin)
 
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