Regulator by-pass at engine start?

Oct 19, 2019
921
Albin Vega 27 Limerick
Hi.

My 2 12 V batteries are wired in parallel.

They are close to end of useful life - voltage measured at bus bar
drops to about 12.5 V 24 hours after charging.

Not a prob as still plenty of amps to crank engine - but only with
alternator regulator disconnected.

Presumably - because batteries are partly discharged - reg is taking
too much current at start to allow starter motor to crank fast
enough... a vicious circle if I ever heard of one.

Present "solution": connect reg cable once engine starts - sooner or
later I'm going to screw up & disconnect cable with engine running -
blowing the reg.

Planned "solution": "improve" setup by putting a make/break switch on
the field line between reg & alternator - off when starting, switch it
on once engine has started.

I know that switching off positive supply to alternator once engine
running will blow regulator - am I right in thinking that even if I
accidentally knock off field line no harm will ensue?

Please don't reply suggesting I buy 2 new batteries - family, house ,
car etc all need to be kept in good order too!

Thanks

John

Vega 1447 Breakaway