12V Battery Power switching to 230V without losing power

Thread Starter

mramstedt

Joined Sep 23, 2022
2
Hi,

As energy prices have soared in the last few months, I am trying to build a system to my cottage where I can charge two 180Ah 12V AGM batteries overnight from 12am to 8am (when the cost of electricity is below 9c/kWh). I would then connect a certain circuit with around 250wh of consumption to this circuit between 8am to 12am and then it would switch the circuit automatically to mains 230V AC between 12am to 8am. So I guess I would need two timer relays? Is there any way to avoid power loss (spike) between the switches?

Thanks,

Marko
 

Ian0

Joined Aug 7, 2020
6,294
A relay will change over in less than 10ms. That is quick enough to avoid problems in most electronic equipment.
A few things to bear in mind:
1) charging a battery is not a perfectly efficient process. You will lose at least 10% of the power you use to charge the battery, plus any losses in the charger.
2) an inverter is probably about 96% efficient, BUT it consumers a standing power of about 1% of its rated capacity.
3) your batteries will wear out after about 300 charge-discharge cycles and need to be replaced.
 

Thread Starter

mramstedt

Joined Sep 23, 2022
2
Thanks for your reply. Would this be the same with solar power batteries, would they have to be replaced every year?
 

Ian0

Joined Aug 7, 2020
6,294
Thanks for your reply. Would this be the same with solar power batteries, would they have to be replaced every year?
Look at the datasheet.
I have not seen VRLA batteries, even ones specified for deep cycle use, that manage much beyond 300 cycles.
You should use tubular plate batteries. They are usually supplied in single 2V cells, but some manufacturers such as Rolls and Trojan make them In 12V blocks.
They should outlast a lithium battery at about half the price, and are fully recyclable when they eventually fail.
If you really want long battery life, choose NiFe cells. They will probably outlive you.
 
Top