battery problem?

[Dingo]

my 2008 696 has a problem
I keep it connected to an optimiser and the voltage is about 12.4v after charging but if I go for a ride the engine management light comes on around 30 miles later and dash says battery error
voltage from optimise leads is 14.3v, voltage from leads connected to battery with bike running is under 12v, new battery, new reg/rec or both?

[rollo22]

could be as simple as a knackered battery

search under Fried Reg/Rectifier and should give you some assistance.

[Darren69]

Under 12v means its not charging. Does it not go above 12v when you rev the engine? If it doesn't then suspect the reg/rec or the connections and wires to it.

[Mr Gazza]

Nothing in your post to indicate anything wrong with the battery. You should be seeing about 14v at the battery terminals when the bike is running. So this implies a fault with either the Alternator or Reg/Rec.
My first check would be to make sure the alternator and rectifier are properly connected to each other and the battery, with all the cables in good condition and most importantly, the connections from alternator to rectifier must be good, clean and firm.

Any sign of melting, burning or charring to the above could well mean that the reg/rec is toast... But not always.

[Dingo]

thanks for the replies,
Had a look at the reg/rec, wiring and connectors, all outwardly look good, no sign of overheating/bad connections

[Dingo]

update:-
stripped the bodywork off to get to the connectors

output at the alternator connector on all 3 phases 20v at idle rising to 60+ when revved, all good!

Checked output of reg/rec nowt

checked battery and with ignition on 12.8v the voltage dropped steadily, bikre running, same scenario

new motobatt battery off Ebay and mosfat reg/rec from M&P

now with the bike running the voltage at the battery is 14v ish happy days!!!

[Mr Gazza]

Well done. Logically tested and swiftly fixed.

You probably didn't need to change the battery, but a Motobatt is a damn good investment anyway. You should be well set up now.

Do keep an eye on those alternator/reg.rec connections and cables though. They are the Achilles heel of the whole system and take no prisoners if they get a little corroded or loose. They need at least an annual check or they can catch you out.