How to measure power requirement for zener

I want to run a 24W 12v LED strip using a 12v deep cycle marine battery.

I want to back up my battery with a back up battery using the attached circuit, but this zener is $25.

Are there better/cheaper options? The batteries shouldn’t get down to 12.2v.

Dual Batt.jpg

1N6059 is "1500 WATT BIDIRECTIONAL TRANSIENT VOLTAGE SUPPESSOR"
Seems mistake, what this circuits needs is a diode schottky, get a couple for about $1

And a 55V rated TVS at that. Completely the wrong part number, probably meant to be one of the 1N58xx
series ?

Using diodes like this doesn't give a backup option, its safe a way to parallel batteries that aren't
at identical states of charge (normally a bad thing).

Both batteries will reach full discharge together, so I wouldn't call it a backup circuit, which would
switch from one battery to the other and give some sort of indication that the first one needs recharging.

Hi,
OPs circuit.
a1fa1ba2cc120739eef4ca81d3367c176ab09835.jpg
Tom… :slight_smile: