ICE alternator current display/logging

[rhills]

Hi All,

One of our vehicles is an ICE motorhome and for various reasons, I'd like to display the current going into/out of the vehicle battery as well as the current being produced by the Alternator. Ideally I'd also like to log both of these.

As our Alternator is rated at 80A (no indication if that's peak or continuous, but I assume peak) so most of the commercially available display devices are much help as they seem to have a range up to 10A. As an aside, what ICE never has more than 10A entering/leaving the battery?

Anyway, given my desire to log from two different sources (battery and Alternator), I figured I'd either have to spend heaps of money (not) or make my own. The MYO path seems likely to involve something like an Arduino/clone or a Raspberry Pi. From my limited reading so far, I think I could do what I need with a small Python program running on an Arduino + a couple of appropriately sized shunts + voltage sensor boards.

Has anyone else tried doing this sort of thing? Any suggestions/recommendations before I splurge on an Arduino/clone as a Christmas present for my wife

[jonescg]

Current clamp. So much easier.

[rhills]

Current clamp. So much easier.

Chris, I'd considered those, but had concerns about how robust the setup would be in a motorhome that regularly travels on corrugated roads, eg the clamp bouncing around and wearing the insulation on the encircled wire. Also I was concerned about possible inaccuracies arising from external EM radiation (eg the alternator itself). However, I only know enough about these things to be dangerous, so I'm very open to re-education!

[jonescg]

So you want to be able to look at currents as you drive? A bit like the old ammeters you still see on vintage tractors and the like.

[rhills]

I mainly want to log them, so I can track what is being supplied to the vehicle battery and thence (via a DC-DC Charger) to the house batteries, as well as all the peripherals like lights, instruments etc.

I figured if I was logging them, it would be useful to have a display so I can see what's going on from time to time.

[T1 Terry]

Victron make a battery monitor that can be linked to a computer by cable or Bluetooth, the part number is BMV702. after you have finished logging the alternators input you can reposition it to watch/record what is going on with the house battery. the standard shunt is rated at 500 amps, but higher capacity shunts are available. Simple to wire and program and does monitor quite a few things that are very useful for monitoring the house battery via the Bluetooth app to a phone.
Another possible method is using a Junsi Cell logger with data recording and us the first 2 pins to record input from a shunt and next pin to the start battery positive so there is enough voltage to powers it. The record interval set at 30 secs rather than 2 secs will give you roughly 7 days of data before the log file is full. Be careful not to over flow the file because it will start to write over the original file and all will be lost. I haven't actually tried this method, I just use the Junsi logger to monitor the cell voltages and the Victron BMV to monitor the battery.

T1 Terry

[rhills]

Hi Terry, thanks for the info.

I was aware of the Victron monitor but as I already have a very comprehensive monitor for my house batteries as part of their BMS, the Victron would only provide a little extra functionality for me which doesn't really justify the price for my situation.

On the other hand, the Junsi Cell Logger looks like it might work well enough, simple, measures exactly what I want and no more, and very affordable. I can live with having to extract the data inside of 7 days. It would be nice to convert the voltage from the shunt into a Current display, but for $50 or so for this gadget, I could probably do that in my head. That said, programming an Arduino/clone could be quite fun...

[T1 Terry]

I guess we all have different views of what fun is The programming part is only the beginning, debugging is the part that kills any fun the first part might have generated

T1 Terry

[peter_mcc]

There are some Hall Effect current sensors around which may be easier to use than a current shunt.

If it's the current clamp type (eg the Redarc GS-AMPS) then you might have to protect the wire from abrasion but that would have to be a heap easier than reliably inserting a current shunt! (The Redarc GS-AMPS is made by a NZ company - there aren't many other options around that are as neat).

If you're going the current shunt method you need to either put it in the negative feed or using something like a TI INA196 to shift the output voltage down from the positive side.