Battery Isolator for MPPT solar charger

[rossny]

Hello,
Hooked up a solar array to a MPPT solar charger and it worked great for my house bank but my start battery was not getting topped off. So....copying my Balmar alt I added a batt isolator to split the charge wire to both banks and keep them isotated from each other. When I hooked it up the battery voltage from both banks averaged out on the volt meter and then the solar controller turned itself off. When I direct wire the controller to one bank or the other it works fine and charges that battery bank. What did I do wrong?

[Maine Sail]

Originally Posted by rossny

Hello,
Hooked up a solar array to a MPPT solar charger and it worked great for my house bank but my start battery was not getting topped off. So....copying my Balmar alt I added a batt isolator to split the charge wire to both banks and keep them isotated from each other. When I hooked it up the battery voltage from both banks averaged out on the volt meter and then the solar controller turned itself off. When I direct wire the controller to one bank or the other it works fine and charges that battery bank. What did I do wrong?

You can't use diode isolators with solar controllers because the controller is looking for an "turn on voltage" and it can't see a voltage on the input stud..

Use a battery combiner/ACR (voltage sensitive relay) instead. If it is just for a start battery you could also use an Echo Charger or Balmar Duo Charger. Not much good about diode isolators.......

[rossny]

Thank you Maine...I thought it might be something like that. Must be getting warmer up there, enjoy.

Sent from my VK810 4G using Cruisers Sailing Forum mobile app

[dansken]

I know this is an old thread, but: Can I supply the "turn on voltage" from the "energize stud" on eg. a Victron Argofet battery isolator (this stud is normally used to energize an alternator if is needs so)?

[dansken]

...just got a reply from the local Victron dealer: the Victron MPPT does not need a "turn on voltage" to function. I.e. it can be connected behind a battery isolator without problems....

[kevin439]

Originally Posted by dansken

...just got a reply from the local Victron dealer: the Victron MPPT does not need a "turn on voltage" to function. I.e. it can be connected behind a battery isolator without problems....

Dansken thanks for your post - I am planning to do the same thing. One question: did you connect both your alternator and MPPT to the same input on the isolator, and is it working well for you? Thanks!