Dual Sensing Charging through Alternator

[isdehart]

Hi All - Can't seem to find the answer in old threads...

I have the aux battery system connected directly to alternator via blue sea acr. Aux batt system receives charge from 200a solar panel to top off. When aux batteries are sufficiently charged the acr is dual sensing so should allow charge to flow the other direction and charge started battery...

there is no direct connection to start battery from aux, only through alternator...

is a charge able to flow to start battery from aux batteries via the alternator?


thanks

 

[Nautamaran]

Yes, the alternator is connected directly to the starting battery via the PDC box on the Pos(+) battery terminal (it’s on fuse #1), so if you have connected the Blue Sea auto charge relay directly to the alternator then power will flow from there to the start battery.

Note that the opposite is true: you’ve connected the ACR to the start battery via the alternator fuse, so that will be always live - even when the engine is off - so should be treated with due respect.

-dave

 

[isdehart]

thanks for reply.
Does this risk any damage to alternator?
Power flowing to it as well as from it. Power flowing through it when engine is off.

 

[autostaretx]

thanks for reply.
Does this risk any damage to alternator?
Power flowing to it as well as from it. Power flowing through it when engine is off.

Power does not go through the alternator when you have two batteries connected to it.

It sources power which will go to the batteries. The batteries will fight it out between themselves as to who gets the most energy from the alternator (and perhaps from the other battery, it one is low enough).

Here is the circuit (drawn by extracting germane items from the service manual)



You can see that the flow does NOT go "through" the alternator (generator).

From your description, the BlueSea attaches to the little round circle on top of the generator (just below the "RD" on the drawing) ... its current still doesn't go "through" it. All you've done is remove the protection of the alternator's fuse. The alternator's regulator diodes prevent "backflow".

If you do not have a rooftop air conditioner, there is a "spare" fuse position on the Power Distribution Block (PDC) that's bolted on to the starter battery's positive post.

--dick