Hi guys, my f1 has managed to make one battery expand like a balloon and another started smoking and spewed battery acid all over the bike..

Safe to say they're overcharging?

Just done diode test on the reg/rec and it shows 510 on all 3, a bit high but all the same so is it bad? Also tested the resistance on the stator and it shows 0.3 ohms all 3 ways.

Anything else that could cause the battery to massively overcharge? Or is the regrec bad afterall?

Thanks
Will

 

What's voltage reading at battery at idle?
What's voltage reading at battery @ 4000rpms?

 

Ill check once I've got a new battery but from memory it was fairly normal when I checked last

 

if normal voltage, then RR + stator is working properly.

You may have short that's draining battery quickly and overheating it. Causing melting, bloating, etc.

 

Any advice on checking for that sort of thing?
Electrics are all new to me

Cheers
​​​​

 

Get one of these and learn to use it to measure voltage and resistance.
https://www.harborfreight.com/electr...ter-63759.html

Then we start measuring wires at various junctions.
Compare to values from manual
Where numbers are different than they should be is problem.

 

So, just checked it, and at first it was fine (around 14.6 at both idle and 4000rpm)
But as idle dropped when bike warned up it was showing over 17 at which point I cut it off to avoid destroying the battery

And just to clarify, it now goes above 17 at anything other than idle, just double checked.

 

Just a thought, could running super low on fuel potentially cause this? Just been running it with tank off so pump is running with nothing going through it. And when last battery smoked up it was almost dry on the reserve, I was on my way to petrol station

 

Done resistance test on the Regrec as stated in my Haynes manual and its out of spec so perhaps its that afterall. Diode test checked out but some of these values are way out, I'll try the new one I've ordered and hope for the best.

 

petrol level shouldn't affect RR output in any way.
17v !!! certainly appears you've identified RR is culprit.
will want to replace that before it fries another battery.