Should The Bright Way Switch Mode Battery Charger BRW77FR Go To Zero ohms When Not Plugged In?

Updated 11/04/2025 | Published 07/31/2025

Question:

My dump trailer has to spend a lot of time away from a 120 volt plug in. If it’s more than a month, unit not used but starting with a fully charged battery, the battery will be flat. Ohmed out the two leads on the charger and there are 6.6k ohms. Is this unit supposed to go to zero ohms when not plugged in? This is a class2 battery charger. 5 amp fully automatic for 12 volt battery.

asked by: Chris R

Expert Reply:

Hi Chris!

The Bright Way Switch Mode Battery Charger for Hydraulic Lift and Dump Trailers - 12V - 10 Ah # BRW49FR incorporates circuitry that uses very small output pulses to detect if a load (like a battery) is connected. This allows it to "turn on" when a device is plugged in and minimize power consumption when idle. The 6.6 ohms likely reflects the resistance of this internal detection circuitry, not a fault in the charger. Measuring resistance also helps chargers determine the appropriate voltage and current to deliver, preventing overcharging or damage to the battery.

Hope this was helpful and please let me know if you have further questions!

Out of curiosity, why does your dump trailer spend so much time idle?

expert reply by: Lazer S

Chris R.

8/5/2025

It is used on the farm and stays in or at a barn with no electricity.

Lazer S.

8/5/2025

@ChrisR That makes sense. Let me know if there is anything else I can help with!

Chris R.

10/31/2025

@ I took the FC charger off the dump trailer 3 months ago. When I used it last week, the battery was still fully charged. The class 2 charger was definitely pulling enough amps to run the battery down. FYI. Chris.

Lazer S.

11/4/2025

@ChrisR Thanks for getting back to me! Sorry it was running your battery down though. This is honestly the first time I have heard of this happening with one of these. Guess I wasn't much help here, but let me know if there is anything else you need. I'm typically quite helpful!