Recently I had a critically low battery warning whilst the battery was showing 30%+. The battery has been otherwise sound. I realise it could have started to die but that's not the point of this thread.
Given that the battery has been otherwise sound I had a look at the connector inside the drone to see if there was something amiss.
Incidentally what connections are used to sense the battery condition etc?
I noticed that the rear most pillar to which the connector screws was cracked and wondered if this might be allowing the connector to move whilst the drone was in flight so I decided to try and glue/reinforce the mounting. I thought it best to strip the drone and that was interesting.
It turns out the pillar had cracked right the way through and that pillar ( there are two) wasn't securing the connector at all. The break approximately corresponded with the end of the screw.
I decided the best solution was to tap the pillar (it is hollow almost all the way to its root) for a machine screw then screw in a piece of 'threaded bar' (long screw with the head cut off) and use a nut to clamp the connector. A 2mm thread might do but I do not have 2mm taps or screws so I used 8BA instead, clearing the 'swarf' from the pillar's blind bore was the hardest bit, I used a damp needle as the smallest drill bit I have was too big.
I tried to ream out the broken off bit of the pillar so that the screw thread would pass through it (trying to tap it didn't seem wise). It already had a length wise crack and in this weakened state was split in two by the reaming. I should have bound or wrapped the broken off bit before reaming it. I was able to glue the halves back together using a shaved down match stick as a mandrel but ultimately the bit got misplaced, it will turn up but I didn't want to wait.
I decided to use epoxy putty to make a 'replacement' for the misplaced bit. I had a loose connector and encased it in ONE layer of cling film, to prevent the putty sticking to it, the cling film was loose so that it could deform, and put connector in situ.
Aside from two screws the connector also has a spigot which mates with a casting in the shell. Then I pressed/squashed the putty into place and down the remaining pillar, when the putty had gone off enough to be like silicon rubber I tried to remove the connector but there are some depressions in the connector that the putty had faithfully molded to and the connector brought the putty (I will call it an insert from now on) off with it. I trimmed these protrusions off with a scalpel and smeared the bore of the insert and outside of the pillar with expoxy glue and put it and the connector (encased in a new piece of cling film) back in situ, then checked that the connector would come away leaving the insert in place, it did.
Next day, success, one firmly attached and solid insert and the connector removed.
When I started to reassemble the drone I noticed the the second battery connector mounting pillar had a fine length wise crack in it, so, lesson learned, I bound it with a thin but strong thread. I used a clove hitch to anchor the thread and then a series of 'half a clove hitches' to "whip" it, then smeared the whipping in epoxy. Note the pillar fits into a recess in the connector so it is not wise to whip the pillar right to its top. (the insert molded itself to its recess).
I didn't think to photograph the repair before now sorry
Given that the battery has been otherwise sound I had a look at the connector inside the drone to see if there was something amiss.
Incidentally what connections are used to sense the battery condition etc?
I noticed that the rear most pillar to which the connector screws was cracked and wondered if this might be allowing the connector to move whilst the drone was in flight so I decided to try and glue/reinforce the mounting. I thought it best to strip the drone and that was interesting.
It turns out the pillar had cracked right the way through and that pillar ( there are two) wasn't securing the connector at all. The break approximately corresponded with the end of the screw.
I decided the best solution was to tap the pillar (it is hollow almost all the way to its root) for a machine screw then screw in a piece of 'threaded bar' (long screw with the head cut off) and use a nut to clamp the connector. A 2mm thread might do but I do not have 2mm taps or screws so I used 8BA instead, clearing the 'swarf' from the pillar's blind bore was the hardest bit, I used a damp needle as the smallest drill bit I have was too big.
I tried to ream out the broken off bit of the pillar so that the screw thread would pass through it (trying to tap it didn't seem wise). It already had a length wise crack and in this weakened state was split in two by the reaming. I should have bound or wrapped the broken off bit before reaming it. I was able to glue the halves back together using a shaved down match stick as a mandrel but ultimately the bit got misplaced, it will turn up but I didn't want to wait.
I decided to use epoxy putty to make a 'replacement' for the misplaced bit. I had a loose connector and encased it in ONE layer of cling film, to prevent the putty sticking to it, the cling film was loose so that it could deform, and put connector in situ.
Aside from two screws the connector also has a spigot which mates with a casting in the shell. Then I pressed/squashed the putty into place and down the remaining pillar, when the putty had gone off enough to be like silicon rubber I tried to remove the connector but there are some depressions in the connector that the putty had faithfully molded to and the connector brought the putty (I will call it an insert from now on) off with it. I trimmed these protrusions off with a scalpel and smeared the bore of the insert and outside of the pillar with expoxy glue and put it and the connector (encased in a new piece of cling film) back in situ, then checked that the connector would come away leaving the insert in place, it did.
Next day, success, one firmly attached and solid insert and the connector removed.
When I started to reassemble the drone I noticed the the second battery connector mounting pillar had a fine length wise crack in it, so, lesson learned, I bound it with a thin but strong thread. I used a clove hitch to anchor the thread and then a series of 'half a clove hitches' to "whip" it, then smeared the whipping in epoxy. Note the pillar fits into a recess in the connector so it is not wise to whip the pillar right to its top. (the insert molded itself to its recess).
I didn't think to photograph the repair before now sorry
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