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Here is my alarm for the 12 volt battery. A makeshift affair at this point but low cost. Parts used are: Voltage monitor with LED and audio (beeper) alarm functions. Bought it here from New Harbor because it shipped from the US (it came in like two days). It is made for monitoring batteries in model aircraft so you know when to land! There are all sorts of things like this out there. Cable to connect to it easily - here's the link. Also from New Harbor. Three 470 ohm 1/4 watt resistors. A 1/2 amp fuse (do not connect anything to the battery without a fuse!) Red and black clip leadsThe monitor looks like this (the two black thing on the left are beepers): It can monitor up to 6 lithium cells at about 3.5 volts each. So I use the resistors to make it think its connected to a 3 cell battery with about 4 volts on each cell. You can set it to alarm (lowest cell) anywhere from 3.00 to 4.00 volts in 0.05 volt steps. Mine is set at 3.60 which, with my crummy resistors, should alarm at about 11.2 volts on the car battery. Here is the whole mess connected to my camping battery - monitor/alarm, resistors, fuse and clip leads: The display cycles through total voltage (shown above), largest delta between "cells" (don't care about that), and each "cell" voltage. The lowest one is important since it will trip the alarm. It is now connected under the hood all stuffed in a plastic bag near the grille and duct tapped in place (don't know if it can stand the heat). The beepers are quite loud so I should hear it out in the garage if I'm awake and in the main living area of the house. Asleep is another story but a $15 audio only baby monitor should solve that problem. The battery monitor draws 27 mA. The current goes to an average of 60+ with the alarm going off. I hope this is all a waste of time!

The 2nd replaced, about a year and a half ago, 12V battery on my CMAX is probably not getting charged even after driving on highway for 50mins to 1hour recenlty: 01/20/2015 11:15AM, after parked the car for 3 hours after hi-way driving 1hour, turned the key to ignition postion 1 to get the radio playing. After 3mins, the radio shutoff, turned the key to ignition postion 3, the "low battery..." message appeared. Turned the car off, and turned the key to postion 1 again, 1 to 2 minus later the radio turned off again. Turned the car on, the "low battery" appeared again. This time I left the key at position 3 for 10mins, hopefully the 12V get charge. 01/21/2015 7:40AM, right after hi-way driving for about 50mins, parked the car, removed the key, radio still playing (have not open the door yet). After 1min, the "low battery" appeared but the screen immediately shutoff. Turned the key to position 3, and there it was the "low battery" appeared again. For each time, I got into and looked at the ET screen for the 12V voltage. If key was at postion 2, the 12V had 12.4Volt constantly. And when I turned the key to postion 3, it showed between 14.3 and 14.4 (flickering between those 14.3 and 14.4). I could have radio on for 20mins or more when key is at postion 1 or 10mins when the key is taken out before I open the driver door. The "low battery" happened from time to time before but never in twice in a row like the above. There were times I saw the "low battery" message and the radio was auto-shutoff. But immediately after that, took out the key, turned the key to position 3 and back to position 1: no "low battery" for 20mins or more until I shut the car off and opened the door. There were also times I saw the "low battery" message on the previous days. And after driving 1 to 2 hours, parked the car for 3 to 4 hour, and then the key to postion 1 and the radio play for 50mins or more before I turned off the car and locked the car. It is probably whatever computer component controlling the 12V battery charging or reading has gone haywire. Or it has always been like this, I do not know. Or the 12V battery is in need of another replacement, but then that replacement get no charging as it is always supposed to. Or another problem adding to the unknown phanthom discharge that still not sovled by Ford.

The 12V battery problem hasn't gone away so I want to monitor actual current into/out of the battery. Measuring voltage, although helpful, has problems. It can be OK one evening and dead the next morning if there is too much current flowing all night. Here's what I've done so far. Removed the big plastic cover/tray that goes across the back. There are 3 screws along the front edge and one 10mm(?) nut in a deep pocket near where the ground cable bolts to the frame. The two outside rear corners are held in place with spring clips - you pull the whole thing straight up once the screws and nut are removed. Connected a two conductor wire to each end of the big ground cable that runs from the negative post to the car's frame. The ground cable now acts as a current "shunt" producing a very small voltage that is proportional to current per good ol' ohms law. Ran the wire under the rear compartment "flooring" into the rear seat area where it could be connected to a digital multimeter set for DC volts. You need one that can indicate down to 0.1 millivolts. DO NOT CONNECT ANY WIRES TO THE POSITIVE TERMINAL! Calculated the resistance of the ground cable by measuring the current through a light bulb connected across the battery and the voltage drop across the "shunt". Two different bulbs gave the same value of 0.54 milliohms (0.00054 ohms). Now you have the value so "don't try this at home"! Current can now be calculated as: 12V Battery Current (amps) = Voltage Reading (millivolts) / 0.54 Or in "round numbers", just take the DC millivolts and multiply by 2 to get amps. If the car's frame is positive (relative to negative post), the battery is discharging. If the battery post is positive (relative to car's frame), the battery is being charged. With car OFF, opening/shutting the door sends the current to about 8 amps. After a minute or so it steps its way down to about 0.4 amps. Then after maybe 30 minutes or more it finally drops to under 0.01 amps. (Used a very high resolution meter here as you are down in the microvolts.) The rear cargo lights appear to draw a bit over 1 amp. They eventually turn off if hatch is left open (at least it happened once while testing). Next step should be to build a little micro-power monitor I can run from the accessory jack that can stay in the car all the time. Just look through the window and see how it is doing. But we shouldn't have to do any of this!!!Here are the monitor connections. For the curious, here is the sticker on my new battery. The bar code number you can't read is 31508 53155. Note the 100 month warranty (36 months free)! Since it doesn't start the ICE it should almost last forever. Quite a pity we're having ANY dead battery problems. The left side of the battery compartment looks like this with the HV battery fan (Made In USA!). It should point straight out the back for a bit of jet assist! :lol: