Ignition battery

[Andy]

Jim,

I doubt the voltage of the main battery would be sufficient to fully charge the emergency ignition battery. However, if the main battery is on charge (either from a charger or the alternator), and the MAIN bus voltage is close to 14 V then, yes, the emergency ignition battery will be charged.

Same caveat as with alternator though - if the ignition battery is significantly lower than full charge the unregulated charging current may be higher than recommended by the battery manufacturer. A good AGM charger will limit both voltage and current. Your main battery charger has no control over the current going to the ignition battery.

I wouldn't trust a 5 year old ignition battery without running discharge capacity tests. It may be easier to simply replace it as you should be able to buy one for under $30.

[Andy]

During pre-flight earlier this week my emergency ignition battery dropped into the red alarm range with less than 10 seconds discharge. This battery has been in service for about 18 months. I do not understand why these batteries, that should last 5 years, are failing so quickly. This battery has never been discharged more than 15 seconds and has normal off charge and on charge voltage.

I am considering dumping the emergency ignition battery and fitting a second TCW IBBS dedicated to right ignition. It looks like it can be done as a completely reversible mod by adding to the existing wiring and taking some existing wiring out of service.

What I don't know yet is whether a 3AH IBBS can be fitted in the space vacated by the ignition battery. Has anyone done this mod before or will I be the first?

[aflyer]

During pre-flight earlier this week my emergency ignition battery dropped into the red alarm range with less than 10 seconds discharge. This battery has been in service for about 18 months. I do not understand why these batteries, that should last 5 years, are failing so quickly. This battery has never been discharged more than 15 seconds and has normal off charge and on charge voltage.

I am considering dumping the emergency ignition battery and fitting a second TCW IBBS dedicated to right ignition. It looks like it can be done as a completely reversible mod by adding to the existing wiring and taking some existing wiring out of service.

What I don't know yet is whether a 3AH IBBS can be fitted in the space vacated by the ignition battery. Has anyone done this mod before or will I be the first?

I did this when I first built my EX-3. I had previously used the diode/battery system in an RV-8, and in 8 years I replaced the battery every year. So, I used the TCW battery, the same model as the one for the G3X backup. It is mounted next to the two ignition brain boxes on the right sidewall.

After 18 months and 200 hours, the TCW battery system works as new. I often test it during a cross country trip by running one side ignition from it. The voltage output falls during the first 10 minutes or so to 12.5, then stays there for an hour.

Thanks for all your help on this forum Andy.

[Andy]

I did this when I first built my EX-3.

Good to know it's been done before, thanks. Do you have any photos of the installation that you could share? Private message to exchange email if you prefer.

Thanks,
Andy

[Gary K]

Can someone post some pics of the TCW's battery location if used to replace the ignition backup battery.

Thanks
Gary

[aflyer]

I rolled my own electrical system, so things look a little different.

ign battery.jpg

[Ak Paul]

The IBBS manual from TCW’s website is informative. For storage beyond 9 months TCW requires the battery to be recharged, either with their charger or via the aircraft battery. As my project is slow (but most enjoyable), I picked up their charger. The jack on their charger connects conveniently to the batteries.

[jjoffe@me.com]

I rolled my own electrical system, so things look a little different.

ign battery.jpg

Hi - The IBBS battery from CubCrafters looks identical to the two batteries in your system - so why do CC suggest a second battery that is less mHA from a different supplier?
Advice is welcome thanks
Julian

[Andy]

Hi - The IBBS battery from CubCrafters looks identical to the two batteries in your system - so why do CC suggest a second battery that is less mHA from a different supplier?
Advice is welcome thanks
Julian

The photo shows an installation using 2 TCW 3AH IBBS units. CubCrafters standard design is one IBBS for the G3X Touch system and a 2 AH AGM battery for ignition backup.

The IBBS retail price is about $250 but the AGM battery is about $35. The AGM battery will, if in good condition, power the ignition for 30 minutes. I assume CubCrafters though the AGM battery was "good enough".

The TCW IBBS is not perfect. It should power the ignition system for a lot longer than the AGM battery but its internal battery pack can be permanently damaged by accidental deep discharge.

Like many things in aviation the choice is a compromise and, if the aircraft is Experimental EAB, the builder or owner can make a different choice than the designer. I plan to replace my FX-3 ignition battery with a second IBBS this winter.

[jjoffe@me.com]

The photo shows an installation using 2 TCW 3AH IBBS units. CubCrafters standard design is one IBBS for the G3X Touch system and a 2 AH AGM battery for ignition backup.

The IBBS retail price is about $250 but the AGM battery is about $35. The AGM battery will, if in good condition, power the ignition for 30 minutes. I assume CubCrafters though the AGM battery was "good enough".

The TCW IBBS is not perfect. It should power the ignition system for a lot longer than the AGM battery but its internal battery pack can be permanently damaged by accidental deep discharge.

Like many things in aviation the choice is a compromise and, if the aircraft is Experimental EAB, the builder or owner can make a different choice than the designer. I plan to replace my FX-3 ignition battery with a second IBBS this winter.

Andy Thanks for the explanation - perhaps I am not reading the wiring diagram correctly on my EX3 manual but I do see an IBBS connection to plug 244 on the gea 24 box pin # 22 - my assumption is that the diagram uses the IBBS style battery for the ignition system or is that only the monitoring portion? I see no other Ignition back up power going to the Lightspeed boxes in the diagram - sorry to bother you
Thanks
Julian