SDS CDI vs Pmag

[rv6ejguy]

Originally Posted by 6 Gun

Ross in the new model put a 9v back up battery.
Bob

This is a good idea. Powering the CPI with it is no problem with the .1 amp current draw. Powering the ignition coil would be challenging though. I'm interested enough to do some testing though. Perhaps an up sized AGM battery would give you 15 minutes or so in case of a complete electrical failure. We may have room on top of the unit for such a backup.

Appreciate the comment. We'll look into that.

[Chkaharyer99]

A sized up battery is something many of us using glass are familiar and comfortable with. It's become, for lack of better words, the experimental industry standard. Examples include the newly released G5 which has an optional battery that can be added.

Plus one on this idea.

[tspear]

Ross,

What about selling a super capacitor option for both the coil and the CPI?
The super capacitor could be sized to provide anything from a few seconds to minute of capacity. It would give constant current and voltage, and should buffer and voltage spikes.
FYI, this is way beyond my knowledge, except we used one on a printed circuit board we had designed about eight years ago. The board was designed to run in a super dirty power environment.

Tim

[rv6ejguy]

Originally Posted by tspear

Ross,

What about selling a super capacitor option for both the coil and the CPI?
The super capacitor could be sized to provide anything from a few seconds to minute of capacity. It would give constant current and voltage, and should buffer and voltage spikes.
FYI, this is way beyond my knowledge, except we used one on a printed circuit board we had designed about eight years ago. The board was designed to run in a super dirty power environment.

Tim

I know nothing about these but I'll do some reading tonight. Thanks.

[tspear]

Originally Posted by rv6ejguy

I know nothing about these but I'll do some reading tonight. Thanks.

Enjoy;
Here is a summary I found: http://www.electronicdesign.com/powe...energy-storage

And this looks close to what we used. We had two in series to get a stable 5 volts.
http://www.vishay.com/docs/28421/220edlcenycap.pdf

The specific concept was called "micro ups".

Tim

[Walt]

A 60 farad capacitor rated at 40-50V would proably the size of a garbage can!

[rv6ejguy]

Looks like a super capacitor would not be suitable for what we have in mind- to run the coil and CPI for 30-45 minutes and get you back over an airport. We've already looked at an AGM battery which weighs about 1 pound and would do the job. Considered some automatic health monitoring and switching already.

[tspear]

Originally Posted by rv6ejguy

Looks like a super capacitor would not be suitable for what we have in mind- to run the coil and CPI for 30-45 minutes and get you back over an airport. We've already looked at an AGM battery which weighs about 1 pound and would do the job. Considered some automatic health monitoring and switching already.

Correct, not to run the system for long. There were concerns about transient voltage issues taking out the CPI system. Which implied could end up with the engine stumbling and which would affect the alternator which would....

The goal is to have a UPS for the ignition and injection system for some period of time. Most wanting 30-45 minutes. LiPo batteries are very well suited to the sustained power draw requirements, however, they are susceptible to power issues when used for a UPS because they are not tolerant of voltage variations (current is often mitigated also by the battery controller), either high or low. There are a couple of ways to handle this voltage variations, you can either use a MOV or similar device to handle the over voltage, and then drain the battery some on the low voltage side.
The problem with this is the the number of cycles on the battery. Now if the battery is lead/acid it is not much of an issue; but it can be a problem for LiPo. So one viable solution is to buffer the transient dirty power with super capacitors. I would guess you only need about 15-30 seconds of power in the super capacitor. This would practically eliminate the draw down of the LiPo except in an actual emergency.
The advantage of this is you can then select a LiPo battery for maximum energy density and minimal cycles. (balanced with cost of course.)

Tim


Tim

[rv6ejguy]

While the LiPO battery would be light, I see too many potential issues with them in this application. For the CPI, we're looking at a Powersonic PS-1212 AGM battery.

We're not too worried about transients, it will function from 7.3V to at least 18 (we'll test how high eventually). If voltage falls below 7.3, the CPI auto resets as soon as voltage returns, takes about .2 seconds.

[gasman]

Originally Posted by rv6ejguy

While the LiPO battery would be light, I see too many potential issues with them in this application. For the CPI, we're looking at a Powersonic PS-1212 AGM battery.

We're not too worried about transients, it will function from 7.3V to at least 18 (we'll test how high eventually). If voltage falls below 7.3, the CPI auto resets as soon as voltage returns, takes about .2 seconds.

I have had one of these Powersonic PS 5ah on my bench for over 5 years and has maintained an 90% charge for a 12 month standby period. It gets charged once a year.