Have a geeky question here and if someone does electronics they may be able to help.

[tyromeo55]

The key is to wire the caps in parallel with the pony battery. Forget about all the other crap

I’m not good with typing up explanations If you want to discuss Feel free to pm me your number and we can talk about it and I can share my free opinion

 

[NightShade]

The key is to wire the caps in parallel with the pony battery. Forget about all the other crap

I’m not good with typing up explanations If you want to discuss Feel free to pm me your number and we can talk about it and I can share my free opinion

I was kinda thinking about that. I may just use two small banks in parallel for the caps but when they discharge won't the battery take a hit?

 

[MacFromOK]

I was kinda thinking about that. I may just use two small banks in parallel for the caps but when they discharge won't the battery take a hit?

No, because the battery will also be supplying power to the starter and maintaining charge to the caps. Voltage won't drop that much.

But this doesn't use only the charged caps for starting either.

 

[NightShade]

No, because the battery will also be supplying power to the starter and maintaining charge to the caps. Voltage won't drop that much.

But this doesn't use only the charged caps for starting either.

My main thing is that if I have a deep cycle battery in the system I would like to keep the power draw from it at a point where it's not detrimental to the battery hence the addition of the caps. But when the caps need to recharge between starts it either comes from the alternator should it actually start or from the battery if it doesn't.

 

[MacFromOK]

My main thing is that if I have a deep cycle battery in the system I would like to keep the power draw from it at a point where it's not detrimental to the battery hence the addition of the caps. But when the caps need to recharge between starts it either comes from the alternator should it actually start or from the battery if it doesn't.

Hence "all the other crap" ...

 

[NightShade]

Hence "all the other crap" ...

Yeah, Exactly. May just grab a 4D or 8D and throw that in the bed and be done with it. Should be enough power to do whatever I need and not draw down too much if I listen to some music with the engine off.

 

[tyromeo55]

I was kinda thinking about that. I may just use two small banks in parallel for the caps but when they discharge won't the battery take a hit?

Forgive me i'm going to try to do my best here

Most vehicles do not use any real amount of energy to crank the engine. Like 2 watt hours. Do the math. figure 200 AMPS (average over the entire start cycle. I know initial is more) for 3 seconds or so. 200A X 12.5V = 2.5KW/HOURS to go from hours to minutes divide 2500Wh / 60min = 41.666 , divide again by 20 to get to 3 seconds crank time. 41.666/20 = 2.083 Wh consumed to start the engine Lots of factors going on with the battery but a couple ones at the top of my head are....

chemistry - A 8Ah 12V SLA pony battery can easily come up with a ton of power for a fraction of a second. Pull a spec on one. I know that it won't list what we are wanting to know but it will show the theory. It can come up with a ton of current for a short period of time... The longer the duration of time the lower the amount of current you can expect. This is a good read look at page 9 for a chart https://www.power-sonic.com/wp-content/uploads/2018/12/Technical-Manual.pdf. I think 20C is not too unreasonable for a couple seconds

Internal impedance of the battery and hookup wires - The impedance of the battery and connecting wires will have a definite affect on the amount of current the caps will be allowed to take from the pony battery.

Here is a fun one. an AA battery has about 4.5 Wh of power. You could charge a good super capacitor bank with one and start a car.


If you do try to get a couple super capacitors and try it out I would caution how you initially balance them to the pony battery. In my car stereo days I had a small incandescent 12v lamp that I soldered some leads and banana clips onto. Used it in series to recharge the cap bank. When current is flowing the lamp with light up and dim as it equalizes out.

Yeah, Exactly. May just grab a 4D or 8D and throw that in the bed and be done with it. Should be enough power to do whatever I need and not draw down too much if I listen to some music with the engine off.

Ummmm. yea..... That is a complete 180 from your original post.


T?he Supercap idea is pretty cool and all but it would not work in my application and for less money I can more flexible. A AGM Odyssey battery and nothing else to worry about (at least for what I do).

 

[MacFromOK]

In my car stereo days I had a small incandescent 12v lamp that I soldered some leads and banana clips onto. Used it in series to recharge the cap bank. When current is flowing the lamp with light up and dim as it equalizes out.

Actually... this should do exactly what you want, John. You could either use a switch to load the caps when desired, or leave it connected all the time.

And unless you add a silicon device (diode, etc.), there should be no voltage drop because there's no outflow from the caps once they're charged. So anything wire-wound should equalize to the battery voltage as Tyrome mentioned.

Dunno what I was thinking, but I'm blaming the new BP meds (lol, they are actually messing with me).

 

[NightShade]

Actually... this should do exactly what you want, John. You could either use a switch to load the caps when desired, or leave it connected all the time.

And unless you add a silicon device (diode, etc.), there should be no voltage drop because there's no outflow from the caps once they're charged. So anything wire-wound should equalize to the battery voltage as Tyrome mentioned.

Dunno what I was thinking, but I'm blaming the new BP meds (lol, they are actually messing with me).

I fully understand what you mean. For a few months now some things just don't work right in my head. It's all given me a lot to think about though, just need to decide what exactly I want to do.