Diode Battery Isolators vs Relay/MOSFET Isolators

[Kosmofreeze]

I just learned why I can't get a full charge on my batteries while charging off my alternator. I'm pretty sure it's the voltage drop from my diode type battery isolator. Best I see when charging from the alternator is about 65% ... per my Victron battery monitor. I guess I could try to increase the output voltage of the alternator or switch to a more efficient isolator ... or, do nothing?

 

[dingbat]

I just learned why I can't get a full charge on my batteries while charging off my alternator. I'm pretty sure it's the voltage drop from my diode type battery isolator. Best I see when charging from the alternator is about 65% ... per my Victron battery monitor. I guess I could try to increase the output voltage of the alternator or switch to a more efficient isolator ... or, do nothing?

Far better off with a automatic charge relay (ACR)

 

[Chris1956]

Gee, the voltage drop of the diode is about 1 volt DC. Alternators often charge at 14+Vdc. I would think you should be able to get more than 65% charge. Something is wrong.

You might check the diodes in the VR of the alternator.

 

[boscoe99]

What voltage are you seeing at the battery when the isolator is allowing charge current to reach the battery?

Even with the voltage drop across the diode the voltage should be higher than the resting battery voltage, allowing the battery to be charged. It will just take longer.

 

[Scott Danforth]

Did voltage drop should be 0.7volts

Most diode style isolators also have a dedicated sense terminal for the alternator

 

[alldodge]

My 1994 Formula started with an isolator and the Alternator output wire was disconnected from at the starter and the ALT. Formula ran a new wire to the isolator and from it they ran to each Bat. This way the sense wire remained connected to the start Bat via the regular harness

Do agree ACR is best