We have two batteries, about two years old, on our 2007 HiLo. They have been running down and we can't figure out why. We also have a solar panel on our roof. Our trailer has been sitting in our driveway the last several days. We haven't been running any appliances, but the battery has gone down. We drove it 120 miles round trip today and hoped the batteries would recharge but they didnt. Aren't they supposed to recharge while you are driving? Does it matter what position the master switch is in if you aren't running anything in the trailer?

Most tow vehicles don’t have the wire gage to really charge I don’t understand why they are built that way. Maybe it’s a brake battery thing. Not a trailer thing.

Engineering????

Are you SURE nothing is on in the trailer? My 2007 HiLo was bought new and it had a radio/TV/CB/DVD unit installed that was NOT "switched". It was connected directly to the battery, bypassing the Master Switch. The battery ran down in it too, due to the "keep alive" circuitry in the radio. When I finally figured this out, I installed a simple on/off switch in it's power line, which stopped the power drain.

I think the 15W solar panel that HiLo offered as an option, is mostly a decoration. It supplies very little power.

If your battery did not charge when you were driving it around, your vehicle's 30A fuse to the battery charging wire may have blown. This happens very frequently when you raise the top of the trailer with it connected to the tow vehicle and the TV's engine is running. If the trailer battery is weak, the lifting motor will pull enough Amperage through the charging wire to blow that fuse. I always disconnect the trailer before operating the lift system.

If you put the Master Switch in the middle position, it SHOULD turn everything in the trailer off except for the refrigerator.

- Jack

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Hi-Lo 1707T - Tire Minder TPMS on Tow Vehicle and Trailer, 300W Solar Battery Charger, Equal-i-zer WDH, Progressive Dynamics Converter, Fan-Tastic Fan, LiFePO4 battery 12V DC Electrical System, SoftStartRV mounted on A/C
2024 F150 Platinum FX4 3.5L PowerBoost SCrew

The fuse was blown. We will get it replaced and we now know that we need to unhook before raising or lowering our trailer. Thank you!

Cost control. On my Mustang, Ford found it cheaper to run two 10 AWG wires to the alternator, rather than one 6 AWG.

Part of the charging challenge is low starting voltage at the alternator. To fully charge a lead acid battery requires a charging voltage between 13.8 and 14.1 volts DC. The battery will still charge at 13.5v DC, but never fully charge (which may not be that important as long as AC power is used periodically). If the alternator is starting at the optimum voltage, you'll end with less at the end of a 15 foot wire due to Ohm's law (current/resistance). Because the voltage is so low and the current is so high to start with, losses to resistance are high. You must use at least 10 AWG to get 13.5v at the end, 8 AWG (13.6 VDC) and 6 AWG (13.68 VDC) is better.

Additionally, the manufacturer is unlikely to have supplied enough charge current for the additional batteries, so upgrading the alternator is advisable.