Hello all,

Hope this is the right location to post these questions.

I'm looking at using a couple pre-made boards to handle UPS duties for my 12V network electronics. Searched around the forums already but not seeing exactly what I need - I don't want to make a circuit from scratch.

One of the concerns I have is switch time and what capacitor I might need to support the devices during failover if the device is not instantaneous. I'm not sure if any of these inexpensive boards are instantaneous and am looking to support a 5A load...

These are the couple I am looking at.

https://www.ebay.com/itm/284232250492
https://www.ebay.com/itm/383760213828
I also looked at some alarm modules, but those got pricey quick.

I was considering devices only that take input from source and battery and do not charge. I want to connect a low power charger directly to the battery when power is active.
The latter one can enable and disable the charger but, using a dedicated charger for the cell chemistry, I'm not sure I need that - or want to mess with setting the voltage on that board to kick the charger on at the right point.

Appreciate any thoughts, thanks!
-Pete

 

This is basically a battery backup and doesnt really need much of components if built super simple.

 

Thx for the reply! Will the load voltage be the higher of the 2? (Depending on charge mode, it could be higher on the battery side) Which was another concern I had about some of the pre-made options where you could tweak the charge voltages (I removed those from consideration right away - they were not smart chargers).

I'm not a big fan of releasing the magic smoke, and was trying to keep the battery charging separate from the mains thinking it would be safer using an appropriate charger.

 

Thx for the reply! Will the load voltage be the higher of the 2? (Depending on charge mode, it could be higher on the battery side) Which was another concern I had about some of the pre-made options where you could tweak the charge voltages (I removed those from consideration right away - they were not smart chargers).

I'm not a big fan of releasing the magic smoke, and was trying to keep the battery charging separate from the mains thinking it would be safer using an appropriate charger.

The primary path should be higher, through D2.
There are numerous variations how to construct a simple backup system, Google "12V backup battery circuit", pick the one you like and which fit to your need.