Victron DC/DC or Cyrix-ct ?

[Papawads]

I have Victron shore power charger, panels and MPPT and a huge amount of wasted solar power. I want to top up the bow thruster bank from my house bank (see great thread this week on that), so I asked Victon if I should use their DC/DC charger or their Cyrix-ct. Their answer .... "ask a dealer"

Do you guys have a view?

Also (sorry) what is isolated vs not-isolated DC/DC charger???

Huge thanks
Papawads
:-)

[Tupaia]

Originally Posted by Papawads

I have Victron shore power charger, panels and MPPT and a huge amount of wasted solar power. I want to top up the bow thruster bank from my house bank (see great thread this week on that), so I asked Victon if I should use their DC/DC charger or their Cyrix-ct. Their answer .... "ask a dealer"

Do you guys have a view?

Also (sorry) what is isolated vs not-isolated DC/DC charger???

Huge thanks
Papawads
:-)

If both banks (House-Thruster) are LA based (AGM or FLA) then the combiner will work fine. If one or other bank is a different chemistry (lithium based) then DC-DC is the way to go. If both banks are (lithium based) then no need for any switching device.


You only need an isolated DC-DC charger if the two batteries that you are combining do not share a common ground (-ve) circuit. Pretty rare.

[SailingHarmonie]

Originally Posted by Papawads

Also (sorry) what is isolated vs not-isolated DC/DC charger???

Huge thanks
Papawads
:-)

A non-isolated DC converter has the negative of the source and the supply connected together. With an isolated charger, there is no such connection and the two systems are free to float at their own potential (unless there is another connection somewhere).

On most (but not all) boats, the DC connections of different battery system share a common negative, so an unisolated device seems a good choice. But, there is a catch. Best design practice has the negatives connected at ONE and ONLY ONE spot. This avoids setting up ground loops where different parts of the negative wiring are at slightly different voltages, and current flows between them. This can cause all kinds of hard to diagnose problems.

There is no downside to using an isolated converter in a system that already shares a common negative, and there can be a downside to adding a connection of the negatives in a new place.

There are places where a non-isolated converter is the better choice. For example, if you are using a 24 to 12 V converter to supply power to your NMEA 2K buss, and using the same 24V system to power some of the instruments. You would want the instrument power and the buss power systems to have a common ground.