Secondary AGM battery won't power inverter - Suggestions?

Really need a voltmeter to check charging volts, and then load test once charging is verified, to know battery condition.

New doesn’t always guarantee ‘good’ these days.

 

Well you have it all mixed up.

The first thing is that your laptop is drawing watts and the battery is rated at cold cranking amps.

Let's break it down what that means.

For simplicity sake let's say your laptop draws 120 watts, that is at 115 volts the laptop will draw a little over one amp.

For the inverter to produce one amp at 115 volts, it will require a little more than 120 watts, more like 125 watts.

On the 12 volt side that 125 watts turns into at 12 volts (using that number for calculating everything but it is actually higher), this means you will draw 10.4 amps, which is alright for most configurations.

However we need to look at your setup.

I am going to assume that the batter you bought is TX-14 size batter, AGM is just one form it is sold in and the Everlast isn't bad but pricey.

This exact battery does have 220 Cold Cranking Amps (CCA) which means that when used to start a motor, it produces 220 amps when it is cold. I won't get into those details but it won't work for you because it isn't the number you need to look at.

The number you need to look at is one of two numbers, either one will work. The first is Amps per Hour number also know as Amp Hour or ah.

This number tells you how many hours the battery will work above 10 volts drawing one amp. There is differing numbers used, some use 2 amps others use four, but this size batter it should be one amp.

The other is number is called reserve capacity (RC) which means the number of hours a fully charged battery will work drawing 25 amps until it drops to 10.5 volts.

OK so back to your setup, your battery has no RC listed, but it does for ah, which is 12 amp hours. This means that you running your setup for 1 hour will deplete the battery.

So if you got that, great, if not read it again.

AND to another issue. charging an AGM.

An AGM is to be charged with a battery charger made for AGM batteries, not hooked up to the truck system, it has to be specific to that battery type. I venture to guess that you are putting just a voltage on the the terminals and it never gets properly charged.

OK now my recommendations, put that battery in to an ATV where it belongs.

Go get a good battery charger that will work for an AGM.

Get a proper battery that will supplement the power from the truck's battery, I would think a good deep cycle battery from Optima or Trojan would be better.