Battery Charger
Philldapill
Posts: 1,283
Late last night, I went out to my car to find that my dome light was on. It must have been on for >24hours, and my battery was prrretty dead - radio came on, but the engine just clicked. This was at 2am, so getting someone to jump me wasn't really an option.
Anyway, long story short - I had another battery in my apartment, so I connected it to my car battery with aligator clips. I let it "charge" my car battery for 30 minutes, and when I measured it, about 1A or 2A was flowing from my charged battery, to my car battery. After 30 minutes, I tried cranking it, and it hesitantly started.
This got me thinking. Having some sort of small device that could trickle charge a car battery when no other option is available, sure would be nice to have. However, lugging around a 25lb battery isn't really an option for most people. Lugging around 4 D cell batteries is, however.
Looking at D cells, most alkaline battery's have a capacity of about 12A-hours. If I were to have 4 of these in series, that should be about 5 or 6V at 12AH. In theory, that should be around 237.6kJ. If the average car takes 250A of starting current for 2 seconds, that is only (12V*250A*2seconds) 6kJ to start the car.
My plan, is to make a fairly high power boost converter, and take the 6V from the D cells, and bump it up to 12V, with about half the current. If I were to drain the batteries in 30minutes, I should get about 1/3 the capacity out of them, so maybe 4AH, or ~89kJ. Since the car takes 6kJ to crank, I'm thinking that this may be do-able.
The point of this device, would be to suck some small, compact disposable batteries dry in 30min, but give an injection of battery charge so you can start your car. I think mounting all this in a small, 6" x 2" x 3" box that you could store under the seat, would be a pretty nice thing to have when put in a pinch.
What do you guys think? Techincally feasible? Economically Feasible? I sure don't want this to happen again, without any solution.
Anyway, long story short - I had another battery in my apartment, so I connected it to my car battery with aligator clips. I let it "charge" my car battery for 30 minutes, and when I measured it, about 1A or 2A was flowing from my charged battery, to my car battery. After 30 minutes, I tried cranking it, and it hesitantly started.
This got me thinking. Having some sort of small device that could trickle charge a car battery when no other option is available, sure would be nice to have. However, lugging around a 25lb battery isn't really an option for most people. Lugging around 4 D cell batteries is, however.
Looking at D cells, most alkaline battery's have a capacity of about 12A-hours. If I were to have 4 of these in series, that should be about 5 or 6V at 12AH. In theory, that should be around 237.6kJ. If the average car takes 250A of starting current for 2 seconds, that is only (12V*250A*2seconds) 6kJ to start the car.
My plan, is to make a fairly high power boost converter, and take the 6V from the D cells, and bump it up to 12V, with about half the current. If I were to drain the batteries in 30minutes, I should get about 1/3 the capacity out of them, so maybe 4AH, or ~89kJ. Since the car takes 6kJ to crank, I'm thinking that this may be do-able.
The point of this device, would be to suck some small, compact disposable batteries dry in 30min, but give an injection of battery charge so you can start your car. I think mounting all this in a small, 6" x 2" x 3" box that you could store under the seat, would be a pretty nice thing to have when put in a pinch.
What do you guys think? Techincally feasible? Economically Feasible? I sure don't want this to happen again, without any solution.
Comments
There are many small battery emergency kits available already - take a look in the auto shops.
Cheers,
- Howard
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Eliminator Inteligent Battery Guard - Automatically kills power to the car lighting if batery is getting to low.
I have even seen a battery pack designed to charge your car through the cigaret lighter but can't find who makes it.
Still just because the product exists does not mean it is worth trying yourself.
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