Standby current metering

toyota
rav4

#1

Ok, i admit, i got a bunch of aftermarket electronics in the car, already when i bought it and since then it’s been an ongoing fight to keep batteries alive, because there is always one or the other thing that creates standby currents of several hundred mA.



I’ve already put a cable for a DMM around a battery disconnect switch to quickly measure the draw when the battery has yet failed again, but i would really love to have a meter on the dashboard that can show me standby current (with at least 10 mA accuracy) without having to open the hood and cabling up a DMM myself.



Even better would be something that could data-log the standby current on an SD card or the like. Or at least show the average mA usage since the last time the motor was started.



Isn’t there anything out there on the market that does that ? I could not find anything with Google. Only thing i could find are analog amp-meters that are way too inaccurate in the mA range of the standby current. ANd of course nothing that would integrate an average over time. And last year i had the bloody alarm constantly going off when i was away that of course sucked the battery dry, but was not happening when i returned. Only indication of that happening where red-faced neighbors.


#2

Since your battery is not located in the passenger compartment and I do not think you will go to the the expense of using a RF controled soleniod, your parameter of not having to open the hood makes this request impossible for me to fill. If you want to switch your battery cable from passing current through the meter to bypassing the meter via a RF controled solenoid it can be done.


#3

Rather than gather data and study it when you already know what is happening, get an auxiliary battery to power your add-ons; mount it in the trunk and isolate it from your starting battery with a motorhome type isolator. With one of those, you can run the aux battery flat yet start your engine and charge both batteries from your single alternator. If you will run the aux battery flat, it should be a deep discharge battery.

Check www.omega.com to see if they have a suitable d.c. current logger data acquisition device that can be adapted to your wants. You may need an inverter and an auxiliary battery to operate it. It will likely cost more than you want to pay.


#4

I’m with WhaWho on this one. Vehicles that have numerous accessories, like cop cars, ambulances, fire chief cars and the like, have heavy duty alternators, heavy duty batteries, and auxilliary batteries. That’s why cop cars can sit for hours with their lights going without having to worry about starting up again. The lights are running off the auxilliary battery.

There should be aftermarket systems to modify your car in this way.


#5

Your County must have more money than mine. My Chevy Dealer got cop cars in frequently for warranty work and they did not have dual batteries, not real well maintained either.

My Fluke 87 will data log and it is from 1999. The newer models have even more features that will make logging and viewing the data even more convienient


#6

Understood. But i could not find any product, be it using a solenoid or a very low resistance (0.001 ohm or the like) resistor. Any pointers ?


#7

If i believe the PriorityStart web page then police cars often use that product to switch off the main battery when it is running low. And it is actually working fine for about two years on a battery, but afterwards (see above) i think the battery has lost so much capacity that it will not start the car anymore at the voltage level the prioritystart switches it off.


#8

With all the electronics have your upgraded the alternator? Perhaps you are not recharging the battery with enough current, since when the car is running the audio is likely on as well. Also, did you install a much bigger battery than OEM?

If you know you have current drain when the ignition is off you need to isolate the component causing the drain, or install all the extra electronics on a separate line and put a switch in the circuit to cut power to the add on electronics.

A separate 2nd battery is a good idea if you can find space for it, but you’ll need the upgrade to a higher capacity alternator to keep both batteries charged and run the electronics.