Large voltage drop

[brian 56]

Large voltage drop. 2 months ago installed 2 new batteries wired parallel 560 amp/hrs.Run a 65 litre fridge drawing max 5 amps lights and radio in tiny house. Ran perfect for a month very little draw .Batteries stayed around 13 volts. Batteries ran flat 2 nights in a row Disconnected fridge. One afternoon battery voltage went from 13.6 and within an hour when sun was off panels 12.5! Shall I check solar controller (10 yrs old) mmpt 40 amp 450 watts of solar and load test Batteries? Any ideas thanks

 

[OzSolar]

Large voltage drop. 2 months ago installed 2 new batteries wired parallel 560 amp/hrs.Run a 65 litre fridge drawing max 5 amps lights and radio in tiny house. Ran perfect for a month very little draw .Batteries stayed around 13 volts. Batteries ran flat 2 nights in a row Disconnected fridge. One afternoon battery voltage went from 13.6 and within an hour when sun was off panels 12.5! Shall I check solar controller (10 yrs old) mmpt 40 amp 450 watts of solar and load test Batteries? Any ideas thanks

What kind of batteries?

 

[brian 56]

Agm

 

[OzSolar]

One afternoon battery voltage went from 13.6 and within an hour when sun was off panels 12.5!

Actually, that is a normal voltage drop for lead acid. Lead acid voltage can drop several volts the moment the loads exceed the charging source(s). It's a bit confusing that you're just now experiencing (noticing?) this.

Shall I check solar controller (10 yrs old) mmpt 40 amp 450 watts of solar and load test Batteries? Any ideas thanks

What do you mean by the batteries ran flat? Did the inverter hit the low voltage shut down?

Your current situation is a good example of why voltage should not be relied on as a state of charge.

If you don't have something like a Victron Smart Shunt it's time to add it.