Choosing an ignition backup battery for an electronic ignition piston aircraft engine

[Neal]

Here is the pigtail for the Optimate 10A charger. I ordered this and will consider installing this on the battery.

Amazon.com: OptiMATE Cable O-11, Weatherproof Battery Lead, Heavy Duty/Auto/Marine : Everything Else

Amazon.com: OptiMATE Cable O-11, Weatherproof Battery Lead, Heavy Duty/Auto/Marine : Everything Else

www.amazon.com

This is the Optimate charger I use on my EarthX starter battery:

Amazon.com

 

[Neal]

TCW responded to my inquiry about using their IBBS battery like we use for our G3X as a backup for the Light Speed electronic ignition:

Neal, yes one of TCW Technologies IBBS Battery Back Up would be a suitable replacement.
TCW Support

As CubCrafters has a mount already designed for this, and possibly a dual mount I hear may be used in XCubs? This seems like an ideal solution to have two of these back to back in the right forward panel area, one for the G3X and one for the Light Speed.

 

[Neal]

I think an advantage of the TCW such as the 3AH model is that you could wire this into the GEA 24 to view voltage readings on the G3X. Although our current ignition backup also does this so it's probably moot. But form factor wise this seems like something to consider.

Product:

Integrated Battery Back-up System (IBBS) - TCW Technologies

The Integrated Battery Back-up System (IBBS) provides an engineered solution to enable an endurance bus for critical loads found in aircraft. The IBBS system provides back-up power to critical electronic loads such as EFIS, GPS, Autopilots and engine monitoring systems.

www.tcwtech.com

I didn't look at dimensions to compare the 3AH to the 6AH model. Curious so I'll look those up later.

Documentation:

https://www.tcwtech.com/wp-content/uploads/2020/03/725.0022-Install-Instr-1.8-IBBS-12v-3ah.pdf

 

[Neal]

If/when I install my EarthX backup battery I want to perform a test on the removed (recently installed) PowerSonic battery. I'd like to put a simulated load on it such as 1.2A and chart the voltage drop. The question also is when is this battery considered unusable and needs to be replaced. Typically AGM/Lead Acid batteries below 50% are potentially damaged. People performing tests such as ground runs until engine running rough need to be aware of an excessive discharge on this battery.

I welcome any tips for testing the removed PowerSonic battery so we can see how long it will take to run it down and monitor/measure the test.

 

[Cactus Charlie]

I welcome any tips for testing the removed PowerSonic battery so we can see how long it will take to run it down and monitor/measure the test.

The simplest test setup is to connect a load and a voltmeter across the battery terminals and start a stopwatch. Log the voltage before load connection and then periodically, say every 10 minutes. Terminate the test at about 10 V to avoid deep discharge damage.

I use high power wire wound resistors but a tungsten filament car brake light bulb can be used. (Brake light will change resistance with current and skew the discharge curve but it will still provide a baseline for comparison.)

First enhancement to that test method is to add a second meter to measure and log the current.

Fully charge the battery before testing but let it rest for at least an hour before running the test.

 

[Neal]

I need to figure out how to get a simulated load matching the Plasma III ignition module, i.e. find something that's a 1.1A continuous load. I also need to determine the 50% voltage point on the PowerSonic battery. Some batteries use 11.9 in the RV (motorhome world of golf cart batteries) and some use 12.1. Just need to do some research when that time comes for testing.

 

[Cactus Charlie]

The Yuasa data sheet shows typical discharge plots for their AGM batteries. If an ignition module draws 1.2 A from an NP2-12 battery (2AH) then the plot of interest is the 0.6CA curve. That curve stops at about 9.5 V after 60 minutes.

The Genesis manual has a similar plot:

PowerSonic does not give a 0.6CA curve but they appear to claim significantly greater capacity but at a lower temperature than the others:

And here is a discharge plot for the first battery I removed from my FX-3:

I don't think this data tells us anything new and I don't think the test you plan will either. Any of these batteries will keep the engine running for over 30 minutes when in good condition. A discharge plot of a new battery tells you nothing about how it will perform after 6 or 9 months in the aircraft. Only on aircraft testing, or removal for test, will do that.

 

[Neal]

What catches my attention from your discharge plot, bottom most chart, is your starting voltage. The battery was either not charged or damaged to only have a starting voltage of 11.4V.

 

[Cactus Charlie]

What catches my attention from your discharge plot, bottom most chart, is your starting voltage. The battery was either not charged or damaged to only have a starting voltage of 11.4V.

The test was run several years ago but I have no doubt the battery was changed before testing. It was removed from the aircraft because it was no good.

 

[Neal]

How long was the battery in use? I assume you followed the guidance of annual replacement. That's what concerns me about these cheap batteries. If this is the state at the end of a year, or your plane was not sufficiently charging it?

 

[Cactus Charlie]

The voltage plot may be misleading. Voltage sampling started when the load was connected. There is no record of the unloaded battery voltage.

This was the original battery fitted by CubCrafters and the aircraft first flew May 2020. As I have said before I change the ignition battery on condition and test it at runup.

This battery looked very good when in-flight tested but had significantly deteriorated since then. I have all the test data but I'm not going to dig it out now.

Here is in flight test data (ignore the Amps legend that plot was removed):

 

[Neal]

No need to go back for anything. Was just an observation. Most of us only see the charge voltage and don’t know the actual state of the battery. Last night I showed 12.5 prior to start. 13.7 with engine running. Drain down to 12.1 during right ignition backup test and I waited to see where it would stabilize. Realizing plane has been sitting for two weeks.

 

[Cactus Charlie]

Here is the history for that battery. Just had to open the file and capture the image -