GPS Tracker + 12V Lead acid battery + motorcycle battery. Parallel connection?

[BaltarWithSix]

Hello. I have small GPS Vehicle tracker. It is connected to small 12V Lead Acid battery (the one used in UPS devices). GPS Tracker runs on the small battery for about 3 days. I was wondering if it is wise to connect the small battery also with 12V motorcyle battery (parallel connection). The Idea is that GPS Tracker + small battery are both hidden inside a motorcycle but connected to motocycle battery. When rideing, both small battery and motorcycle battery takes charge and when parked, the GPS device lasts more than 3 days. And when motorcycle battery is disconnected, the GPS Tracker still runs on the small battery for 3 days.

The GPS Tracker is designed to be connected directly to vehicle battery but when a theif disconnects the vehicle battery the GPS is turned off. Thats why I want to use small battery between the GPS and motorcycle battery.

 

[john monks]

May or may not be. If you use a motorcycle battery for your GPS tracker then you might want to use a relay to connect the battery in parallel with the regular vehicle battery to charge it up. The relay coil would be connected to the "ON" switch so the whole system does not drain your regular battery while it is sitting idle.
On the down side, the wires between the regular battery, the relay, and the motorcycle battery would need to be short so as to get enough voltage from your 12V system to charge the motorcycle battery. And if the motorcycle battery ran completely dean and you turned on your vehicle you might draw enough current through the relay to damage the relay.
I'm afraid you just have to try and see what happens.