Planning on adding solar and a battery monitor (or just upgrading)

[TitanMike]

If planning on adding solar panels and a battery monitor to your RV here's something to consider.

First off, when charging batteries from your solar system pretty much every volt matters and losing any due to line loss from he converter on the way to the batteries is not desirable. Often to prevent this the Solar Controller is mounted as close to the batteries as possible. Sometimes it's not possible if the batteries are mounted outside or in a remote compartment. This can also be compounded by the need or desire to have the solar controller in a place the owner can watch it. In installations like this the wire size is often increased between Controller and batteries (the "12 volt output") to minimize voltage drop. Not bad but often the controller won't accept a large enough wire to reduce all voltage drop.

Why does this matter? Chargers and Controllers today have charging stages. When current draw by the charging battery is high the voltage drops and the Controller keeps putting out as much current as it can. When the battery is charged the voltage on the charge wire rises. When it reaches set levels, the controller will switch to the next lower setting and current drops. Any voltage drop on the wire between Controller and Batteries will send a false signal to the controller and it switches to the Absorption stage when it should still be in Bulk. This results in essentially wasted solar energy and longer charge times.

There is a solution that does not require larger wire. Remote Voltage Sensing.

This is where the control voltage for the controller is measured AT THE BATTERY, not at the output terminals of the Controller. Any voltage drop in the wire from the Controller is essentially ignored.

This is where the Battery Monitor comes in. Battery monitors utilize a shunt that is installed as close as possible to the battery as it needs to monitor everything that comes out or goes into the battery. A good battery monitor will share the information it gets from the shunt with a compatible solar controller.

A good example of this is the Victron family of Battery Monitors and Solar Controllers. With Bluetooth tech they network and share this voltage that is measured by the shunt and voltage drop from a distant solar controller is history.

Victron may not be the only manufacturer to employ this method of remote voltage sensing but it's a feature I'd certainly recommend if installing Solar new. I'd also recommend if planning an upgrade.