I recently bought a 2021 T@G Boondock in December 2024. It came with a Diehard Gold RV battery (24DC-2). Over the winter (Dec 2024 - Mar 2025) I removed the battery and kept it on a trickle charger in my garage. The reading when I put the battery back in the T@G from a voltmeter was 13.5V.
We went camping a few weeks back and have the trailer stored uncovered at a storage facility. The Victron app shows that the battery voltage is 13.8v however my voltmeter shows 10.0v at the battery terminal. The battery settings in the Victron are set to default. Due to the discrepancy, it doesn’t seem like the solar panels will ever charge the battery (ie it shows no current to the battery) as it thinks the battery is charged.
The unit is a Victron SmartSolar MPPT 75/10 A054. Firmware is v1.64
Looks like you have a bad connection between the battery and the controller - either a loose connection, a blown fuse/popped breaker, or a high resistance point like an off-brand circuit breaker. The controller appears to be measuring its own voltage, not the battery voltage - the big clue is a 0v minimum reading, which would never be the case if the connection to the battery was good.
Half the voltage issues I see over at DIYSolarForum.com are due to poor connections. Check everything, make sure the connections are clean and tight. Remove connectors, clean with brake parts cleaner if the surfaces are greasy, then follow up with CRC QD Electronic Cleaner. A light coat of NO-OX-ID will help with conductivity and prevent rust and corrosion. Tighten fasteners to spec.
If your battery really is in the 14.4 volt range then it makes sense that the solar charge controller isn’t doing any charging. Do you have another charge source active?
Thank you! The MPPT is behind a panel inside the teadrop. I’m going to pull the panel and check the connections as well as the 20A fuse on the Victron.
I checked the fuses in the battery compartment yesterday and both looked good.
It’s fixed! I went down at lunch and removed the panel to find that the 20A fuse in the MPPT was blown. After replacing it, all the widgets lit up! Thank you all for the suggestions and quick replies!
What scenarios would cause that fuse to blow? The battery cables have 2 wires going to positive, both have an inline 30A fuse (both were fine).
Well, that’s what you have to figure out. The solar charge controller shouldn’t be putting out any more than 10 amps. It should have been able to blow a 20 amp fuse. A lead acid battery shouldn’t be able to cause a spike like a LiFePO4 BMS can when it cuts off the charge. So you need to keep an eye on things.
Note that your PV voltage may be too low. The solar charge controller won’t start charging until the PV voltage is +5 volts over the battery voltage. You mentioned solar panels in plural. If they are wired in parallel, switch them to series to get the PV voltage up.
My mistake on typing “panels”. The teardrop has a single panel. For electrical, there is a 30A shore receptacle, A/C, a small space heater, electric brakes and 7-pin connector all built into the trailer from the factory. The former owner wired in a wireless backup camera where the center marker light would go. The panel that hides the MPPT also has the TV hook up. It’s possible the former owner wired something incorrectly at one time. Everything behind the panel and inserted into the MPPT looked in good shape yesterday. Ill keep an eye out.
The panel is too small in terms of voltage. The panel voltage may come up to a useful level when the sun is in the perfect position. But until that happens, you’ll get no battery charge from the solar charge controller. A bigger/different panel or a second panel wired in series is going to help.
