IBBS - confessional

[Andy]

I was at the hangar and loaded a new G3X database but didn't fly. That broke the normal routine and I managed to leave the hangar without turning off IBBS. It was a week before I found out and the IBBS battery did not seem to take any charge on a 1 hour flight. IBBS voltage did not rise above 7 V.

I spoke with TCW and had my fears confirmed. The battery is too deeply discharged for the charge controller to enable charging. Only fix is to replace the internal battery pack.

The good news, if there is any to be found, is that TCW now allows experimental IBBS owners to change the battery pack themselves. The manual I have on file says IBBS must be returned for battery change.

[ceslaw]

I was at the hangar and loaded a new G3X database but didn't fly. That broke the normal routine and I managed to leave the hangar without turning off IBBS. It was a week before I found out and the IBBS battery did not seem to take any charge on a 1 hour flight. IBBS voltage did not rise above 7 V.

I spoke with TCW and had my fears confirmed. The battery is too deeply discharged for the charge controller to enable charging. Only fix is to replace the internal battery pack.

The good news, if there is any to be found, is that TCW now allows experimental IBBS owners to change the battery pack themselves. The manual I have on file says IBBS must be returned for battery change.

Don't be too hard on your self. I did exactly the same thing. Replacing the battery was straightforward. Hasn't happened again. Yet.

[Andy]

Don't be too hard on your self. I did exactly the same thing. Replacing the battery was straightforward. Hasn't happened again. Yet.

The cost of replacing the battery pack is insignificant compared to the annual cost of insurance. However, I was surprised that the IBBS did not self isolate to prevent its own destruction. I asked Bob at TCW about this and he explained there was a design compromise between getting the maximum possible time out of the IBBS in a real emergency use and protecting the batttery pack against deep and unrecoverable discharge.

Thanks for sharing that you made the same mistake. Maybe our talking about it will save someone else.

[olympiashorts]

I know "someone else" that did something similar and ended up making a big sign on the hangar door with this and a couple other checklist items like: "Flight Plan Closed?", "CO Monitor Off?" etc... I'm told that this list keeps getting longer.

[Rick Bosshardt]

Andy,
Im in the same club, and had to do the same fix.
I havnt forgotten since!

[Andy]

I checked the data log for this accidental IBBS discharge event. Start IBBS volts was 12.5 and log ended after 1 hour 56 minutes with IBBS volts 8.2.

An intentional IBBS discharge test I had run May 2022 was manually terminated after 2 hours 33 minutes with start volts 12.6 and end volts 12.0.

It appears that the IBBS battery had deteriorated significantly in the last 2 years.

[ceslaw]

Good information.

Wonder if replacing the IBBS battery at regular intervals should be considered?

[Andy]

Good information.

Wonder if replacing the IBBS battery at regular intervals should be considered?

I think a periodic discharge test would be prudent and TCM recommends that.

"Battery life depends strongly on many factors including operating and storage temperature, number of discharge cycles and depth of discharge. The battery capacity should be checked at least annually for suitable back-up power operation of the connected equipment. When the battery capacity no longer meets the operating criteria of the aircraft it must be replaced."

I would only change the battery if the test showed significant loss of capacity not just based on calendar time. (That's what I do with the emergency ignition battery.)

[Andy]

Discharge after fitting the new IBBS battery showed a difference of over 1.5 hours capacity compared to one that had been in service for 4 years.

I was curious so I tested the old battery pack and attempted to charge each cell with a charge controller having a proper current/voltage profile. 3 of the 4 cells charged normally but one accepted no charge. I dismantled the battery pack and inspected the bad cell. The CID (current interrupt device) on the bad cell did not appear to have tripped.

I'll be very interested to see discharge plots of other IBBS if anyone decides to run a discharge test. If you don't know how to extract and plot the data you can send me your CSV log file.

[Andy]

Since I am not the only operator to have discharged the IBBS, and probably won't be the last, I'll share what I did to continue operation with a dead IBBS.

IBBS normally does nothing except before engine start and after engine shutdown unless the main battery charging system has failed. If the charging system fails, and IBBS is inoperative, the G3X system will continue to operate normally until the main battery voltage drops below about 8.5 volts (or until an EarthX shuts off).

For a short VFR flight with main battery in good condition I consider the probability of loss of G3X system to be very low and would accept flying with IBBS inoperative.

The biggest problem when operating without IBBS is the sag in main bus voltage during engine start. Normally the GDU, GSU and GEA will auto transfer to IBBS power and will "ride through" any main bus voltage sag. With IBBS failed the GDU, GSU, and GEA may re-boot or, less likely, be damaged.

I avoided the voltage sag issue by pulling PFD, GSU, and GEA circuit breakers before selecting master on. Engine start is done with no engine display which should be no problem for anyone familiar with their aircraft. After engine start the PFD, GSU, and GEA circuit breakers are restored and remain in until the next engine start.

The IBBS will attempt to charge the internal battery pack if main bus is live and the IBBS circuit breaker is not pulled. If the IBBS voltage does not rise to more than 12 V in the first hour of flight it is likely that one or more cells are not accepting charge and the battery pack will need to be replaced.