From Zmilin
I see this subject come up on the forum a lot and there is always a ton of great feedback from members. I thought Id put together a little something as a reference guide when I came upon an article already written. This was geared towards automotive but applies to our world. I pulled out some information that does not apply and added a couple minor things that do apply for us.
I may even do a video to accompany this at some point.
If you’re constantly finding your battery dead after the vehicle sits for a couple days, maybe even just sitting overnight, you might have a current draw. Keep in mind, there are several other factors that might cause a dead battery besides just a current draw. First, you want to check your charging system and make sure there are no problems there. If you still find yourself with a dead battery, you need to start looking for the current draw that is draining your battery. The problem is trying to find what is causing the draw.
What you’ll need
The only tools you will need is a DMM (Digital Multi Meter) and whatever is needed to remove the Negative (-) battery post on your vehicle (wrench, socket, etc.). I would also recommend having a set of “jaw” type accessory probes for your meter. If you don’t have any, you can make yourself some with alligator clips.
How to
Step 1 – Make sure the battery is in working order and is fully charged. Taking current draw readings on a dead battery is a waste of time.
Step 2 – Make sure the vehicle is OFF and all doors are closed. If you have a hood light (or trunk light depending on battery location) you need to fool it into thinking the hood/trunk is closed. For a Motorcycle owner that means all accessories are off.
Step 3 – Loosen the Negative (-) battery terminal, but do not disconnect it.
Step 4 – Prepare the meter for measuring Current per the meter instructions. (WARNING!!! Do not take any Voltage measurements while the meter probes are configured in this position. Doing so can damage the meter!)
Step 5 – Attach the RED probe to the Negative (-) battery post so that you don’t have to hold it. This is easily done with an alligator clip or “jaw” type probe accessory.
Step 6 – With the RED probe secured on its own, hold the BLACK probe tip near the base of the battery post so it does not interfere with the terminal. The object will be to remove the terminal without having to move or reconfigure the BLACK probe.
Step 7 – With your free hand, remove the negative battery terminal while holding the BLACK probe in position on the battery post with your other hand. Optimally you will have a clamp probe accessory on this lead as well that can clamp to the battery post. Allow a little time to pass for the vehicle modules to come to complete rest*. Also known as allowing the modules to go into SLEEP mode. If you are monitoring the Current as this happens, you will see the Current decreasing until it rests at a relatively steady draw. You will then be able to read what your draw is and troubleshoot further from that point.
All vehicles have some form of small or continual (parasitic) current draw. This is caused by things like, clocks or alarm LEDs, etc. All these items need a minimal amount of power all the time to retain their memories, so there’s always a draw. 25-30 mA (milliamp) or less is considered acceptable. It will look like “0.025 A or 0.030 A” on your DMM. Above that, you may have a problem.
If that is the case, start pulling fuses of aftermarket equipment and see if the draw goes away. Car dealerships are well known for blaming aftermarket equipment for this problem, often without ever doing any real troubleshooting, so this is a good place to start. In their defense, most dealership technicians are trained on their brand vehicles and do not even know or understand aftermarket electronics enough to troubleshoot them. If none of your aftermarket equipment is found to be causing the problem, move onto the vehicles fuses.
Changes of 3-5 mA (0.003-0.005) are not necessarily an indicator of something wrong. When you pull a fuse and see a large drop on the meter, that’s when you want to investigate the circuit that fuse was providing power to and find out what is causing the problem. Using this method and testing each fuse (i.e. circuit) one by one, the culprit of your current draw can be found and isolated. You will then need to take whatever actions are needed to fix that problem, but now you know what was causing the problem.[i/]
