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.

[Andy]

I had replaced my IBBS battery pack after the accidental deep discharge but was only seeing IBBS 12.9 V when the engine was running. This voltage is in the green range but I knew it was not normal.

I removed the IBBS from the aircraft for bench testing and found it accepted no charge current. I contacted Bob at TCW to ask for diagnostic assistance and a schematic. He declined both but did offer to diagnose the problem if I returned the IBBS to him. I expected a significant diagnostic charge and a large repair bill as the IBBS was 5 years old and well outside any warranty. When I asked about charges I was told TCW stands by its products and the only charge would likely be return shipping.

TCW diagnosed the problem, repaired it, and will be returning it to me for only the shipping cost. Kudos to Bob and TCW for the excellent support.

Now back to the real reason for posting -

An IBBS that is accepting no charge current will be slowly discharged since it is used at every engine start and likely also for database loading. The IBBS may have greatly reduced capacity if it is ever needed when the alternator fails. The IBBS voltage is in the green for this condition which is misleading. 12.9 V is an acceptable voltage when the IBBS is in use and being discharged. 12.9 V is not an acceptable voltage when the IBBS is not in use and should be accepting charge.

Recent updates to G3X software have added the capability to change scale color bands based on other external conditions. It may be possible to have two different IBBS voltage scales, one with color bands appropriate for "in use" and discharging, the other with color bands appropriate for not "in use" and charging.

If I'm able to implement this I'll post the details. (IBBS scale details are hidden in the standard config file - GEA 24 GP2 Not Configurable - but I have already reverse engineered the IBBS scale and made GP2 user configurable.)

[Andy]

Recent updates to G3X software have added the capability to change scale color bands based on other external conditions. It may be possible to have two different IBBS voltage scales, one with color bands appropriate for "in use" and discharging, the other with color bands appropriate for not "in use" and charging.

I've been working on this idea, on and off, and I have a first draft requirement that I hope to implement soon. I've been looking at IBBS voltages for a couple of different IBBS units and the behaviour on charge is not what I expected. The main battery (SBS-J16) and the standard emergency ignition battery (2 AH AGM) are always charging when the engine is running but the IBBS is not.

The IBBS internal charge controller brings the battery pack to full voltage then shuts off and the voltage slowly decays towards the fully charged resting voltage. If the voltage drops below the charge initiation threshold then charging starts again. This means it is normal to see the IBBS voltage changing in flight even when the IBBS is not in use.

The two IBBS I have available have similar charge initiation and cutoff voltages but I do not know that they are typical of all IBBS units.

My longest FX-3 flight was during phase 1 and it was close to five hours. It shows the IBBS charge cycles very well -

[kshunz]

My FX-3 (#148) has a similar IBBS charge cycle, ranging from 14.2V down to 13.3V with a period of about 95 minutes.

[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?