di2 external battery mounting

pedalbasher

Bit of a DIY question.

I bought a bike with external di2 battery recently. Bought the frameset and the groupset separately, so have had to build it up.

I have noticed (well, actually my LBS noticed) that there is a bolt missing. Basically, the long thin plastic bracket (on to which the battery is mounted) is bolted on to the down tube using (i) the two bottle cage bolts and (ii) an additional bolt/screw below the bottle cage bolts i.e. closer to the bottom bracket. This additional bolt was not included in the pack of bolts that came with the groupset. The issue is that the battery itself sits directly above the hole where this additional bolt should go, so the bolt (or screw?) needs to attach the mounting to the frame and sit as flush as possible to the mounting - otherwise, the battery cannot slide in to the connection point. I have tried using a standard M5 bolt (the same as the standard water bottle cage bolts) but it obviously sticks up too much and the battery can't slide over it.

Can anyone tell me what type of bolt or screw I need to get? I am thinking possibly something like a panhead M5 bolt (10mm). It just needs to sit as flush as possible to the mounting.

Any other suggestions? The mounting needs to be secured down at this additional point because without being fixed here, the mounting/battery rattles up and down against the frame when riding.

Thanks in advance.

Hereford Flyer

Di2 battery mount holes on my frame (Scott Foil) are M4 - so a little smaller then the standard M5 bottle cage bolts. The missing bolt will be the M4 one.

pedalbasher

Thanks. I'll check the sizing again tonight, had assumed they were M5. What heads do they have on them? I'm more concerned about them sitting flush.

janwal

I have the same battery holder on my Ridley Excalibur but it just came with and the top two bolted on with the bottle cage a tie wrap through the base of the battery holder onto the downtube.It could be an option perhaps.

Bar Shaker

It's designed to only use the two water bottle cage bolts

jon33

M4 bolt on my Scott Foil, used a counter sunk bolt then I used a drill to lightly remove some of the metal around the opening so that the bolt sits in flush and doesn't stick out.

pedalbasher

Isn't it an absolutely ridiculous design? I mean seriously, why? The battery is obviously going to rattle if the lower portion of the mounting isn't attached. Why not include a bolt that fits? I've ordered M4 bolts now, with panheads, hope they go flush enough. Will test later.

Bar Shaker

They don't rattle with a little bit of double sided sticky foam pad under the battery housing.

For a retro fit, it works pretty well.

pedalbasher

Bar Shaker wrote:

They don't rattle with a little bit of double sided sticky foam pad under the battery housing.

For a retro fit, it works pretty well.

Great shout!