Starting Gen 3 with dead 12v battery

EDIT: Post removed until we can check this out, there is some discussion below about current draw What I originally recommended may not be sufficient at far as wire size and battery capacity are concerned.

 

tumbleweed is right... the car really doesn't need too much power to turn on. i've even used a "dead" dewalt power tool battery.. they are at 18 volts normally.. dead it was somewhere around 14 or so... the car started rather quick.

a small group of D cell batteries would probably work... so... lantern batteries would be really easy.

you could also use jumper cables and jump it from another car...

just pop the hood... take the cover off the fuse box.. and hook the positive end to the + jumper (should still be under a red cap)... attach the negative to a bolt on the strut tower.

what's nice about the portable charging kits is that they have way too much power... but it's good for many jumpstarts.. or a few on a traditional ICE. (just in-case someone else with a traditional ICE needs a start but you don't want to use your car to jump them... so use the jump pack)

 

Jump from the jump point in the electrical box under the hood (bonnet).

Earlier testers reported that booting a Prius requires a short draw of about 40 Amps. Any small jump box should work.

Tom

 

Wouldn't 40 amperes fry small wires (like the 14-16 gauge mentioned earlier)? I also doubt typical carbon-zinc or alkaline flashlight or lantern batteries could put out 40 amperes. Nickel-cadmium batteries probably can, but those self-discharge so quickly they'd probably be useless for emergencies.

 

I agree 40 Amps would be to much for wire sizes I mentioned unless it's just a transient. I am a bit skeptical of that figure though, where is all that current going? maybe there is a big capacitors to charge or something. Or, ah ha, perhaps current to start the booster pump.

Post 10 on this thread http://priuschat.com/forums/gen-iii...-12v-battery-questions-prospective-buyer.html David Beale indicates he measured 50A for 1/2 second, I can't find the graph that is mentioned.

I have removed my original post suggesting 6V lantern batteries in series and 14 or 16 AWG wire. May not be enough current capacity. Need to check this out. It might work for a 1/2 second and V8Cobra did said he did it with a depleted battery pack from his drill but maybe that was a Gen2, would that be different?

 

It's just a transient, so even zip wire will work. Small batteries would also work, but they need to be low impedance batteries. There used to be a type of D cell battery called "photoflash" batteries. They had the same 1.5 volts, but had low internal impedance. While they couldn't source as much total energy as normal batteries, they could source a lot of amps for a very short time. This made them ideal for popping flash bulbs. As flash bulbs have gone the way of the dodo, I don't think you can find photoflash batteries anymore.

A small lead-acid battery would work well, but that's what you get with many of the small jump packs. Why not buy one of those and be done with it.

Tom

 

That's probably the best solution but I was trying to think of something light in weight, easy to store, and maintenance free (no charging). I picked up a couple of the best alkaline 6V batteries I could find today, expiration date Dec 2017. I'll give them a try next time I have my 12V battery unhooked.

 

Light in weight, long life, easy to use. OK. Get 10 NiMH cells either tabbed or not. If not you will need a low impedance holder. There are aluminum ones made for most common cell sizes. A AA pack would work just fine as long as you keep the interconnects at low impedance, so either tabbed or the aluminum cell holders (made by Keystone). Run #10 wire from each end with alligator clips (solid copper is best - Meuller for example). Make sure you get rubber covers for the clips and perhaps some insulated storage holder for them. Run another cable to both ends of the pack through a diode (in the correct direction to charge only) and a series resistor of about 100 ohms to limit the charge current to about 40-80 mA when it's plugged into 13.8 V. This cable ends in a cig. lighter plug, which you will leave plugged into the car. The battery pack will remain charged (though it only charges when the car is in accy or ready but won't discharge when off).

A lot of work and probably about as much money as a booster pack. So that's why most recommend just purchasing a small booster pack. Then you can also give -other- people a boost (which you should NEVER do from the Prius!).

 

For reference here's the Gen 2 battery current for startup:

Prius Startup Current

The peak current drawn by the previously mentioned transient, varies depending on the state of the brake booster when the start button is pushed. Even if your jump pack was a little undersized for the peak current it will probably work most of the time anyway.

 

The current requirements we have been discussing are all for booting the Prius. Something else to keep in mind is the dead battery hanging on the other end of the cable. Unless you disconnect the dead 12V battery, it will draw power as it tries to charge. This isn't a problem for a normal jump box, but it could easily be enough draw to suck the life out of small battery before you even press the Power button to boot your Prius.

Tom

 

Has anyone heard of or used the'Self Charge Auto Jumper'

The unit is in essence a NICad battery, charged from the cigarette lighter socket, or to start car plugged into same, allowed to discharge to flat battery which then has enough power to start standard engine.
Occures to me that as power requirement of Prius is low - this unit would easily power up the car if battery flat.
- Input: 12V
- Output Current: 5000MA 14.5V
- Simply plug into your 12V cigarette lighter socket to use
- You can recharge your Auto Jumper whilst driving or at home
- AC/DC Adaptor included
- Easy to use
- Jump starts your dead battery in 10 minutes!
- Includes LED emergency light

 

The only problem with this (unless UK-spec Priuses are different) is that the 12V power sockets are not connected to the 12V supply until the car is in any of the 'on' states (Ign-on, Acc, or Ready), thus you couldn't use it to jump-start it via the 12V power connector.

 

Thanks for prompt reply

Not sure of UK spec - however this piece of kit is very compact so do you think it is worth persevering with - eg by using flying connection to fuse box jump lead terminal.

.

 

Further to my note - UK spec is as you state - 12V sockets only connected when car is in any of the 'on' states.

 

I think I have found an OK solution that will work for me. It's a bit more involved the just hooking up jumper cables but since I don't really expect a failure I think it's good enough.

I will use two 6V lantern batteries in series. Be careful if you buy them, get the heavy ones they have more current capacity.

If my 12V battery is dead I will unhook one battery lead from it, pull the brake booster pump fuses, connect my lantern batteries to the under hood jumper terminal and start the car. Then I should be able to unhook my lantern batteries, reconnect the 12V battery terminal, and replace the fuse module.

I haven't verified this yet but it looks like the booster pump fuses are F20 and F21 in the under hood fuse box. F19 is also in the 3 fuse module and it supplies part of the headlights and the horn.

I was going to use smaller wires but I found some nice stranded 12 ga in my shop that was left over from another project so I made jumpers out of that. I paid $6.50 each for two good quality lantern batteries, alligator clips I had on hand. Now I dare my 12V battery to go dead.