If the grid heater relay is not disconnected, I had the thought that having a voltage PID on my iDash gauge layout might allow me to notice a drop when the grid heater is cycling, to see how often or even if mine cycles after the initial engine start. I have two PID choices: "B-Bus Battery Voltage" and "ECU Battery Voltage". What exactly is the difference? Should they always read the same no matter? And is one or the other likelier to show voltage drop when the grid heater cycles? Thanks.
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B-Bus battery voltage vs ECU battery voltage?
- Thread starter Will_T
- Start date
So all I could really find online comparing these is a thread where it was agreed that the initial "B" in "B-Bus Battery Voltage" stands for "Banks". That does not make sense to me and the only Banks item on my truck is the iDash. Why would the truck have something that stands for Banks? But if you Google the term in quotes, there are very few results and all seem to relate to Banks. That is the PID I have on the iDash now, but I will change it to ECU voltage.
H3LZSN1P3R
You're doing it wrong
I really don’t think it would be enough difference to see anyway but the B-Bus may be the IDash bus internally the PID’s are setup by banks on their Idash so it does make sense why you see that.
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That's what I was thinking too. My CTS3 only has one option for voltage, but my Touch and then MM3 both would show internal voltage and voltage reported by the ECM.
Another possible path is to add a way to monitor current flow.
The two main methods are to run the power through a "shunt" - which is a very precise, low resistance "resistor". The voltage drop is measured and displayed as current. This is more or less the gold standard for how current is measured.
en.wikipedia.org
In mobile / RV applications, this is a big deal, so they are very common. Here is an example of a company that produces the monitors. There are a number of them, I am just familiar with this one.
and a photo of some shunts
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The other way is to use a coil approach. In some ways, this is easier as the shunt does not need to be hard wired in. They are less accurate and the readings will vary some depending on if you are driving N- S or W-E. ( it picks up the earth's magnetic field as background noise ). Still plenty accurate for what you are trying to do.
en.wikipedia.org
The two main methods are to run the power through a "shunt" - which is a very precise, low resistance "resistor". The voltage drop is measured and displayed as current. This is more or less the gold standard for how current is measured.
Shunt (electrical) - Wikipedia
In mobile / RV applications, this is a big deal, so they are very common. Here is an example of a company that produces the monitors. There are a number of them, I am just familiar with this one.
What is a Battery Monitor and Why do you need one?
Trimetric Battery Monitors are reliable & accurate fuel gauges for battery banks that provide information how much charge or energy is left in a battery bank.
www.bogartengineering.com
and a photo of some shunts
Useful Accessories for Battery Monitors -
Cable Assemblies for TriMetric Meters Cable Assemblies for Trimetric Meters. These connect Trimetric meters to shunts and batteries. They have four, #22 AWG gauge wires (two twisted pairs) with a 1A fuse and ring terminals for the battery shunt. Two black wires, one white and one red. - 35 ft...
www.bogartengineering.com
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The other way is to use a coil approach. In some ways, this is easier as the shunt does not need to be hard wired in. They are less accurate and the readings will vary some depending on if you are driving N- S or W-E. ( it picks up the earth's magnetic field as background noise ). Still plenty accurate for what you are trying to do.
Hall effect sensor - Wikipedia
Do you guys mean enough of a difference to see between the two choices or to see when the grid heater is cycling? I just set it to the ECU voltage so I'm not going to think about that anymore. But I was using that PID in the hope that the voltage would drop noticeably whenever the grid heater came on. This was just for my own curiosity more than anything else so not a big deal if you don't think the great heater would create enough of a draw to drop the voltage in a way that I would notice it.
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Depends on your alternator configuration. With dual 220A’s it’s indiscernible.
The dash voltmeter is plenty accurate to show grid heater cycling with smaller alternator configurations.