viper_crazy

The best I can tell from my searching is the ammeter is on the ground cable just before the negative post on the battery. So, you should be able to run a lead off the positive battery post and make sure you find a good chassis ground or another solid ground point so the ammeter can still read the current flow.

stormsearch

If you have a 2.7L, Ford has the BMS sensor mounted directly to the battery negative post. You may connect wiring anywhere and the sensor will measure the additional current and provide an accurate state of health for the battery. Other engines which are currently non start/stop, have a hall effect sensor (doughnut) wrapped around the negative battery cables. It is generally located just a few inches away from the negative battery post. If you care if the system monitors battery health accurately, then make sure no battery negative tapping occurs between this sensor and the negative battery post. If the cable you wish to tap with is small enough, try passing thru the hall sensor.

Note - there is also a hall effect sensor between the alternator and battery positive post. This is only used to measure alternator output. Tapping to the battery positive post at any location between this hall sensor and battery positive is want you want to do. It doesn't effect battery parameters, but is used for engine torque algorithms.

Overall, what I would suggest is tap directly to Battery + post, then attach the negative to the nearest ground strap or ground your device to the frame. Just protect from corrosion. Very high loads like for winches and snowplows should have a seperate terminal setup that takes all of this into consideration, but anything below these loads should be okay. Lots of people install audio systems that draw high current and ground either to the rear cab well or down to the frame with no ill effects (if done properly).

tvsjr

If you want to have real fun, add a second battery and an isolator system (required for the communications equipment we typically install - police and fire vehicles). Fortunately, if you disconnect the sensor on the ground cable, the charge system goes back to "old school" mode and doesn't set a CEL.

Probably a great idea for 99% of the users out there, but a real PITA for some of us.

stormsearch

Ford changed that behavior recently about not setting a DTC. Since the BMS is part of the fuel economy savings, EPA/Ford now mandates that it be flagged to the user. This was a running change. Beforehand, a DTC would be captured, but no dash warning light; now a "Check Charging System" message along with a battery light indicator will appear.

TexasFording

iTrader: (14)

unnecessary expense and trouble for what you get. I am running two JLs putting 1200 RMS and my voltage never drops below 12V. You only need to do the "big 3" if you're running a competition system, i.e. tons of amps and subs and chit.

Lare

Thank you for the info, viper_crazy snd stormsearch. It makes sense to tap from the bsttery and use a vehicle ground, I just wanted to make sure that I didn't let out any of the magic smoke.

tvsjr

Interesting. My 16 has had the Hall Effect sensor unplugged since day 1. I wonder if a newer firmware/calibration will change this - that would be a serious problem.

It goes to the dealer next week to get a few items fixed, so I guess I'll find out then.

stormsearch

They would need to change the BCM s/w. I don't think it is something that is being pushed out like PCM updates.

stormsearch

tvsjr - I ran into the calibration supervisor today, they have not pushed this change to have light on dash if you disconnect the BMS sensor. I guess there is an issue for Europe, so what you were doing before will still work.

tvsjr

Thanks! I'd love to know if he has any better suggestions on how to do what we typically do. The trucks are being used for communications/command post and emergency response. We replace the factory battery with an AGM in the stock size (less maintenance), add a Blue Sea ML-ACR 500A automatic charge relay between the two (disconnects the batteries when the truck isn't running or is cranking, connects them when running and when the start battery voltage is accpetable), then add a 200Ah AGM battery in the rear. The technical loads are connected to the rear battery through a low-voltage disconnect. The loads can exceed 100A at times.

If we were running everything off the start battery, we'd just configure it to run through the sensors. But, since we're adding substantial additional capacity that's only present some of the time, this would very quickly confuse the BCM's state of charge calculations.