I had the same problem with the 12 V engine starting battery
early August. I have followed the Amel instructions and I have
replaced the battery ( which was paid by Amel) as it was discharged
after a few days of not using the boat. After the replacement of
the battery everything was operating ok. The last two week-ends I
have not started the motor and this week-end I faced again the same
problem. The 12 V Battery was discharged and I had to start the
engine by following the bridging of the last 24 V battery with 12 V
battery . By doing this the motor and generator started without
problem. After the first time of the problem I have wired a special
dual switch system to do the bridging without opening the battery
box. So in an emergency you can operate the system very easily but
anyway I do not like to use this.

It seems that there is a leak in the circuit. Can anybody advise how
to solve the problem as it is very annoying if you try to start the
engine after sailing and you find out that the 12 V battery is out
of current when you have the 24 V fully charged. Please advise if
somebody had similar problem or I am the only owner with this
problem.
I really can not imagine that the electrical system is so bad
designed without a backup for the 12 V battery.