I have a trailer with an electric jack, and an interior light driven by a 12 volt car battery.

The battery is maintained by a solar panel tied to a voltage controller to ensure a trickle charge.

Notwithstanding the controller reading voltage in from the solar panel, the battery keeps going dead. The battery is recent, less than 6 months old, so I very much suspect it is fine.

If the panel is generating electricity, the voltage controller is delivering power through its alligator clip outputs, and the battery is otherwise good, how do I test for the draw that is killing the battery? There is no fuse panel, so I can't isolate the light or the jack in that way, and switches to both are off.

The jack and the interior light are the only devices that use power wired to that battery?

At minimum, you will need a voltmeter and test light, (a small amp clamp that reads milliamps would be the fastest and best but maybe not required).
Disconnect one battery cable and measure voltage across battery posts.
Reconnect the battery and check voltage when charging.
The above will determine if it's charging.

Disconnect the positive terminal and place the tip of the test light on the battery post and the clip end of the test light on the battery cable (inline with the circuit). If it light up you have a considerable draw (more than 350MA).
You still may have a battery draw if it doesn't light up, amps clamp would work the best from there on.

Thank you!

You should install fuses in each power line within about 12-18" of the battery as well. It is good for fire prevention anyway and it will allow you to isolate the two devices for purposes of figuring out power draw.

It is possible that there is an internal short in the battery even if it is new, though I'd be checking termination points at the jack and light to see if there are any loose strands of wires that might be grounding out.

I'd use a multi-tester and just connect it in line from the battery to the two items and see if they are drawing current then if they both are isolate and then figure out how to fix....

quote:

Originally posted by Blume9mm:
I'd use a multi-tester and just connect it in line from the battery to the two items and see if they are drawing current then if they both are isolate and then figure out how to fix....

The test light check has been used for many years, now they have low current probes that you can put over the battery cable without disconnecting anything. But I figure he does not have one:
https://www.aeswave.com/Low-Cu...Probe-DMM-p9006.html

For voltage leaks, I recommend using electrical tape to seal the leak.
Yea, Sorry.

I am sure you have already cleaned the battery terminals and connections.
Have you checked the electrical ground connections to make sure they are electrically sound and not causing a voltage drom due to the resistance?

Does the controller use more power then the solar panel provides? Disconnect the feed to the jack and light from the battery’s terminals. Monitor the battery to verify that it maintains a full charge.

If it does, hook up the jack or the light if possible to separate them. If not, you may need to disconnect one of them at the load i.e. remove the light bulb or take the cover off of the jack housing and remove the wires. Monitor the battery level ti identify which is the issue.

If it seems that both of the loads are causing the issue separately, pull new wires.

Sounds like a simple system with only two loads, so you likely have no need for a master switch. This was really helpful on a tractor with a (stupid expensive to replace) computer that was killing the battery when it sat. Installed a master switch on the ground cable. Turn it on, start tractor and use. When finished, park tractor and turn master off. Battery stays just fine.

From your description it sounds like either the solar system isn’t chargeras much as you think or the loads are pulling more than you think. It might be worth disconnecting the loads and checking battery voltage upon disconnect and some time later (day or two if the panel is small). If the battery isn’t well charged after a couple days with no load you have a charging issue.

Get a clamp on multimeter and test every wire from the battery to the tail lights for current.

Something like a Klein CL390.

By switches, are you saying battery switches? If so, the only way there could be a parasitic draw is if there was a wire bypassing the battery disconnect. On my 5th wheel, the electric brakes and CO/smoke detector bypass the disconnect. I disconnect the neg at the battery now.

quote:

Originally posted by thumperfbc:
You should install fuses in each power line within about 12-18" of the battery as well.

Absolutely!

Not having protection is just asking for troubles.

quote:

Originally posted by trapper189:
Get a clamp on multimeter and test every wire from the battery to the tail lights for current.

Something like a Klein CL390.

By switches, are you saying battery switches? If so, the only way there could be a parasitic draw is if there was a wire bypassing the battery disconnect. On my 5th wheel, the electric brakes and CO/smoke detector bypass the disconnect. I disconnect the neg at the battery now.

Klein & Fluke are excellent, but if a $100 meter is out of range for this project, here's a less expensive version.
AC/DC Clamp meter

When shopping for a clamp-on amp meter, make sure it will do DC, some will only do AC (there is a cheaper option in the link that is AC-only)

Clamp it on the main line, if there is current flowing with everything off, disconnect devices 1 at a time until the current stops flowing - then you know your culprit. Cheap bulb fixtures are notorious, as will as wires getting rubbed through & grounding to a trailer chassis. Wire sleeving is your friend.

Thanks again, everyone. I will see if my clamp meter has low voltage dc functionality. If so, that is the easiest path.

I appreciate all the help.

A

quote:

Originally posted by ArtieS:
Thanks again, everyone. I will see if my clamp meter has low voltage dc functionality. If so, that is the easiest path.

I appreciate all the help.

A

Low current . You need something with resolution in the milliamp range .