It is very cold, how do I know if the car battery is good and the car will start?? What is the best car battery test method?

[Whitenuckler]

I see what the problem is/was with the small 1.8A charger I am using. The one I had in there before let the voltage go down to 12.27V, and I'm not sure if it would have come on in. I must have left it in maintain mode, as if it were in charge mode, it would not have shut off. I have the "bad" one hooked up to another battery in the garage and will keep an eye on it.

The "new" one I put in yesterday was left on "maintain mode" so I could get a curve of how it works.
The voltage got down to 12.34V (55% Charge) and then switched on.
I am not going to use that mode anymore, as an AGM voltage profile is higher, so it is letting it get too drained if set up for a flooded.
In one hour the voltage dropped from 12.43 to 12.38 so 0.05V per hour. That is with the battery charger still connected and the BM200.
I will need to hook a meter up to the battery neg and measure the milliamp parasitic draw.
I conclusion, I recommend these BM200. I am impressed with the quality of the data, and the crank/charge test. Very good app. Good trend screens.
I am able to hold it near my kitchen window about 30 ft from the truck and update the data.
My battery seems good, the problem was that it was not getting charged properly and I didn't know.

Followup - Again I can't say enough good things about the BM200. I have been watching the voltage verses time with another 1.8A charger of the same type, one I thought was "good". I have seen the Jeep battery discharging even when I left the charger on (not maintain). Then I went and lifted the hood and the charger had switch to off. A closer look at the data showed it spent about 2 hours at 14.5V, then about 2 hours at 13.5V, then shut off and did not turn back on. When I was shopping for more chargers I did see some said they had a built in timer. I will have to read the small instruction paper that came with it and check. I have a work-around for it. I hooked it up to a wifi plug under my hood and set a timer. 2 hours on, 1hour off ect. That way it's gets restarted. I have 2 new battery charger coming, two different types, so I will be testing them out when I get them.

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