I've been chasing a parasitic draw on a Komatsu wheel loader and in reading different web pages I have some questions and have also found some information that may be helpful to others. It seems that most equipment manufactures rarely publish things like what is an acceptable amperage draw with the machine shut down. Some of this info is something I should probably know at my age but unfortunately I don't. I'm told that in the automotive world certain controllers may not go to sleep "completely" for up to several hours after the ignition is turned off. Has anyone run into that in the equipment world? While I think a controller should basically work the same way in either world I have never heard of this before. Any circuit with current flowing will have a voltage drop across the fuse. I discovered some handy charts on a PowerProbe web site. If you measure the millivolts drop across a fuse, these charts convert it to milliamps. For instance, if you have a 0.7 millivolt drop across an ATC 5 amp fuse the chart shows a 39 milliamp draw. This is for a 12 volt system, I think a 24 volt system would read differently, correct? If so, how would you convert it? The benefit to using this method of checking is that you do not need to unplug a fuse to check the draw at the battery. Every time you unplug and re-plug a fuse you wake up the controller so if indeed some controllers take several hours to go completely to sleep you've have to wait that long to continue. A helpful bit of info. To find the maximum acceptable parasitic draw for a specific vehicle, divide the battery reserve capacity by 4 or the amp hour rating by 2.4. The parasitic draw should not exceed this number. I have never had any "formal" training in electrical diagnostics, everything has been picked up along the way so I'm hoping I can get these questions answered and hopefully we can all learn something. Thank you.
On my komatsus, all off them, a main power relay disconnects everything except the key switch feed and the ECM and radio memory feeds. With that said, most unmodified Komatsu machines that deplete the batteries in a short time typically have one bad battery that effectively handicaps the other one. Disconnect the ground to frame wire and install ammeter between. Key off draw should be negligible.
This is a WA200-6 and there are 7 fuses that remain hot after ignition is turned off. I'm suspecting the batteries on this one also but these are questions that I would like to find answers for. Just something I should know.
I've always had a bad time with Komatsu wheel loader electrical systems. Too many relays, too many individual wires, wire insulation that goes bad and cross talks in other circuits and on and on. All the Komatsu wheel loaders I've had my hands on have the battery disconnect that when off, only has one hot wire to the key switch. If there were other wires that were hot, there was something wrong. Saying someone patches a wire into somewhere that it shouldn't have been or there was a failure in the disconnect.
There's only 1 wire but it powers 7 fuses. I don't have my notes here but ECM, HST controller, ign sw. I believe there's a couple for lights.
Since the fuses for a 12 V or 24 V system are the same that would mean the resistance of the fuse would be the same and now you have twice the voltage, so I would venture to guess that the milliamps would be doubled. So I would think your 0.7 mV drop across the ATC 5 A fuse would become 78 mA. Just for haha's, I emailed Powerprobe. Will see what they say (if they respond??).
-6 should be straight up tier III no actual emissions external. Maybe EGR through engine controller. None of your controllers should be awake with the exception of Komtrax, if it has it. The computers need a bit of time to save info and power down, that's where the delay comes on these older units. I wouldn't think it would be any longer than 5 minutes. As mentioned, I would measure battery condition, if it has the serviceable cells, measure specific gravity and fluid level. Good luck.
If you have volts and resistance, ohms law should apply, correct? Make measurements before disturbing the system and write down all your values prior to opening a circuit for actual ammeter readings. I got this thing from blue point called an amp hound, touch probes to fuse and it gives you the circuit current without disturbing anything. For whatever reason, you have to tell it what fuse you are measuring ATO, ATC, ATM etc. But it works pretty good for me.
That was my thought, that you would double it but was not sure. Thanks.
Stopped by the machine yesterday and there was no draw at all at the battery. Thanks.
Powerprobe got back to me and they said the same chart is used for both 12 and 24 volt systems.
Thank you for checking.