switching voltage

Gregory said:

I woul like to know how to switch a main battery when the battery reaches 13.5Volts. When the other battery reaches 13,5 volts the charging circuit is switched back to the main battery I would like to switch a relay which then switches a solenoid.
Could you supply a circuit for this progect.

Click to expand...

ericgibbs said:

hi,
A precise way would be to use a dual comparator IC, each comparator circuit driving a transistor/relay.
When the main battery is less than 13.5V its comp/relay is ON, charging the main battery.
As it reaches 13.5V, comp/relay #2 secondary battery charge circuit is Enabled.
If the secondary battery is less than 13.5V, the secondary battery starts to charge.

Should the main battery fall below 13.5V then it will disable the secondary comparator.

You will need to add hysteresis to the comparators to prevent the relays from chattering at the 13.5V switch over point.
OK.?

Click to expand...