I am currently running the DEI 520T backup battery. I want to use a larger battery that can take care of my horns even though the disconnect the power.

I guess my question is.

Can I just use a larger battery with the 520T backup module?

Any helpful info I need to know.?

One time my battery died when I was at the theatre when I used the key to open the door my horns made a chirping noise but but no full sound....

 

I'll let Teken answer the part about using both.
But I would just use 1.
http://www.autotoys.com has two different models. a 1.2amp and a 7.5 amp model. Teken stated in a previous thread that the 1.2amp would only last for 1.5 alarm cycles. Your current DEI 520T is only .7 amps.

Here is the link for the 7.5 amper. http://store.autotoys.com/cgi-bin/wf...iew/bupbattdlx