Replace your car battery with capacitors!

[sreeve212]

What about this? Boost module solo test no battery: youtu.be/oTi1GWjxeo8

He manages to start a v8, although it has no electronics. I have a 20 watt (14 volts) solar panel I could use to keep it charged during the day although it could drain at night. My car is a wimpy 2.0 liter, 4 cylinder.

Edit: Does anyone know what the cold cranking amps equivalent of this module would be, if it can even be calculated?

[redpoint5]

Originally Posted by sreeve212

What about this? Boost module solo test no battery: youtu.be/oTi1GWjxeo8

He manages to start a v8, although it has no electronics. I have a 20 watt (14 volts) solar panel I could use to keep it charged during the day although it could drain at night. My car is a wimpy 2.0 liter, 4 cylinder.

Edit: Does anyone know what the cold cranking amps equivalent of this module would be, if it can even be calculated?

I had forgotten about that video, and more embarrassingly, that I have started my own car with the same exact boost caps. My car has a parasitic drain of 21.5mA, and I guarantee it wouldn't be able to start after a night of discharging if using 350 Farad caps.

Here is some rough math using my car and these formulas:

1 / Quantity_Series_Connected_Capacitors * Capacitor_Farad_Rating = Total_Series_Farad_Capacitance

1 / 6 series connected capacitors * 350 Farads = 58.33 Farads

(Max_Volts - Min_Volts)*Farad_Rating/3600 = Bank_Amp_Hours

(15.5v - 13v) * 58.33 / 3600 = 0.041 Ah

*15.5v is the most you would want to charge the cap bank up to, and 13v is about the lowest voltage that would start the truck in the video.

Amp_Hours/(Multiplier*Draw) = Hours_of_Runtime

0.041 / 0.0215 = 1.9 hours

* I'd get just shy of 2 hours of parked time before the caps drained so low that it would no longer start my car.

Your first step is still to determine the parasitic draw of your vehicle, which you haven't indicated that you have. It's easy to do with any cheap multimeter. Keep in mind that these figures don't factor in things like having a door open, which turns on the dome light, which rapidly drains the capacitor.

Don't get ahead of yourself. Step 1 is not to buy parts, rather, that is the last step.

The "cold cranking amp" rating is equivalent to the max discharge rating of an individual capacitor. In the case of the BCAP350, the max discharge rating is 170 Amps. Product comparison is here.

[sreeve212]

Ah, all of that is very helpful! I did forget to mention that, yes, my car has electronics so it will have a draw.

I'm assuming that is measured by using a multimeter to measure amperage between the positive terminal of the battery and the positive connector of the car while it is off? I'll go do that.

[redpoint5]

Originally Posted by sreeve212

I'm assuming that is measured by using a multimeter to measure amperage between the positive terminal of the battery and the positive connector of the car while it is off? I'll go do that.

You will want to pop the hood of the car, close all the doors, and let the vehicle sit for a few minutes. Cars with electronics often go into a "sleep" mode after some period of time after opening or closing a door.

You can measure the current by putting your meter in series with either the positive battery terminal and positive cable, or the negative battery terminal and the negative cable.

Try to put the test leads on both the battery terminal and cable before removing the cable from the battery. When a car looses power, even for a fraction of a second, it often has a power spike once it's reconnected. Attaching the test leads before removing the cable will keep continuous power to the car. Especially helpful if you have a radio or navigation system that requires a security code to be entered whenever power is disconnected.

[sreeve212]

Sweet, thanks for the help! It came out to be around 10-20 ma draw which makes sense because it has such basic electronics (no security system, etc.).

Is there anyone out there who has tested these in vehicles for a long period of time? Maxwell gives them 1500 hours life if they are used in high temperatures, which would be usual for engine compartments. That would be my next concern, is whether or not they would actually out-live the life of a car battery even if they (the capacitors) are used in parallel with the battery instead of as a replacement.

[redpoint5]

Originally Posted by sreeve212

It came out to be around 10-20 ma draw which makes sense because it has such basic electronics (no security system, etc.).

Is there anyone out there who has tested these in vehicles for a long period of time? Maxwell gives them 1500 hours life if they are used in high temperatures, which would be usual for engine compartments. That would be my next concern, is whether or not they would actually out-live the life of a car battery even if they (the capacitors) are used in parallel with the battery instead of as a replacement.

I'd get a more precise reading. 10-20 mA is a huge range considering that you would have half the standby time if the drain was 20mA when compared with 10 mA.

The caps are rated to 150 degress F, so it shouldn't be too big of a concern. I don't think it gets much above 130 under my hood. I'm basing this off of the intake air temperature which is drawn from air inside the engine compartment. Of course, lifetime will improve with reduced temperatures.

Everything you could ever need to know about the caps can be found here.

[Enki]

You can also put them in a box and insulate it so it won't ever get hot inside.

[oldtamiyaphile]

So since the cap bank alone wouldn't start my Fiat, I've paralleled it with the lead acid battery in my Renault, in an effort to prolong the battery's life in stop start use.

Problem is the car is now reluctant to cold start. If left for a few days it will start (the ECU always revs to 1500 on start), rev to 1500 stumble and die. When restarted, it will rev to 1500, stumble, and then idle fine.

If left over night it starts, stumbles and then idles fine. Hot starts are no problem.

Any ideas as to what is going on?

[redpoint5]

Originally Posted by oldtamiyaphile

Problem is the car is now reluctant to cold start. If left for a few days it will start (the ECU always revs to 1500 on start), rev to 1500 stumble and die. When restarted, it will rev to 1500, stumble, and then idle fine.

If left over night it starts, stumbles and then idles fine. Hot starts are no problem.

What is the voltage after the car sits for a few days? How does it compare to the voltage just a few minutes after turning off the car?

Maybe when the car sits for a while the cap drains lower than normal after starting the vehicle, and then absorbs too much of the output from the alternator after starting to properly supply the ignition coil with adequate juice.

[oldtamiyaphile]

That's not a bad hypothesis.

I haven't actually measured voltage (embarrassed to say), but it's a new car with new battery (although of course the battery could be a year or so from manufacture) so the voltage shouldn't be sagging. I have my UG in this car so can't monitor the battery without some additional doodad.