Where would I put the battery monitor?

BB. wrote: »

There is an LVD (Low Voltage Disconnect) terminal on many charge controllers... They are typically current limited (8amp or so for many) and can turn off loads if the battery is near dead (not accurate, does not "save" a battery from damage)--but if you attach large loads and/or loads with surges--it can blow the LVD output electronics. So, not normally recommended to connect too.

If you are talking about eleminating the battery and just you panels and a charge controller... Not usually a good idea... Many charge controllers need a not-dead battery to "wake up" and charge. Also, the battery does most of the voltage regulation (and supplying heavy currents for surges). A solar charage controller is not usually designed to regulate without a battery attached.

If you are asking about connecting your load to the charge controller's battery output connections... For several reasons that is generally to be avoided...

1. The charge controller needs accurate measurement of the battery voltage. Placing loads that vary in current requirements (especially AC Inverter) can confuse the controller and actually cause the controller to drop MPPT current regulation.

2. Safety--the load current available is the sum of the battery + charge controller--or almost double the availabe current -- so there needs to be fusing/wire awg sizing to make it safe.

3. Connecting all loads/charge sources to the battery provides the most stable, lowest voltage drop (in general) and clearest wiring / safety of system. Usually, the battery is the center of the "star" and each + lead that leaves the battery goes through an appropriately sized fused.

Usually the shunt is connected to the negative terminal of the battery (battery on one side, Common - bus connections on the other).

The battery monitor shunt needs to measure all current into and out of the battery.

Other shunts may be installed to measure other currents as needed.
The controller is generally rated on output current.

• For a PWM controller (pictured in your post)--the input equals the output current.
• For a MPPT controller--the output current is either equal too or greater than the input current (depends on your Arrays Vmp voltage configuration--one or more panels in series, etc.).

-Bill