Voltage sensitive switching and 'garage type chargers'

[cygnusv]

My garage type charger has served me well over the last 10 years, but... All I want is a voltage sensitive switch. To turn something (a battery charger) off at 29 volts and turn it back on again at 26 volts. How can that be difficult?

Answers that don't include the words 'Sterling' and 'lots of money' appreciated

 

[William_H]

Because you want a VSR to operate in reverse sense ie on at low volts off at high volts. You may have trouble finding a commercial item.
You could if you were electronically inclined build 2 voltage comparator circuits to sense voltage accurately operating a relay to turn the mains off and on again.
Another alternative might be to smooth the output from the charger and feed it to a battery charger controller circuit. UC3906 is one such integrated circuit
http://www.alldatasheet.com/datasheet-pdf/pdf/29407/TI/UC3906.html has data and diagrams.
Another alternative would be to feed the battery charger into a simple linear regualator to leave on charge full time but on a regulated 27.75 volts. An LM 338K is adjustable and good for 5 amps. PM me if you want more advice good luck olewill

 

[nigelmercier]

It would be cheaper in the long term to buy a new charger from CTEK. A dumb charger, even with a VSR controlling the on-off cycle, will reduce the life of your batteries.

http://www.ctek.com/gb/en/chargers/24v

And example: http://www.amazon.co.uk/exec/obidos/ASIN/B005PKGFH2/dolcetto-21

 

[nimbusgb]

A pair of op-amps and a few components will give you a window comparator.

Couple of quid.

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