Impotent Rambo Megatron

dino2104

New Member
Region
USA
I bought a 2021 Rambo Megatron for nearly $7,000, and at first, it was an incredible machine. After serious heart issues, I needed a bike that would let me continue hunting on my property. My land is mostly hills—50 acres in the Southern Tier of New York, with a top-to-bottom grade of about 14%, which is fairly steep. The bike handled that hill easily, towing me and a 200-pound deer in a trailer at about 14 mph in 2WD. It was absolutely awesome.



On 6/25, with fewer than 100 miles on the bike, it would not turn on. I thought it might be a switch or the display, so I called Rambo, and that is when the nightmare began. The technician told me the original system was garbage and said it made more sense to upgrade so I would be worry-free for a while. I paid the $800, and the parts arrived—wrong ones at first. Eventually, I received most of the parts and had a video call for the installation, which they said was “plug and play.” One piece was missing, so when it arrived, I connected it, finished the installation, and turned on the battery. There was an arc flash, and the battery was ruined. I took the bike to a dealer listed on Rambo’s site. At first, Rambo said I was out of luck because the warranty had expired. However, after the technician working on the bike found an issue with the parts Rambo had sent, Rambo agreed to cover the necessary replacement parts. I still had to pay the technician out of pocket.



After months of parts being shipped back and forth—including three different controllers, two monitors, and different wiring—I finally got my bike back. The factory settings in the new display were wrong again; at one point, it showed a top speed of 153 mph. I decided to let that go since it was not the biggest issue. Excited to try the bike, I rode it to a nearby park and found a small hill about 25 feet long with a 10% slope. I tried climbing it using the front wheel first, then the rear. The bike that used to handle my steep property with ease could not make it up this small hill. After many emails back and forth, Rambo said they would make it right, so I shipped the bike to them. A couple of weeks later, they told me it was ready to be sent back, which cost another $250. At this point, I have about $8,000 invested. I specifically asked whether the bike had been tested under load and was assured everything was fine. It was not. The bike performed no better than before, and now it also has a brake issue.



Then it was back to emailing. The bike was advertised as having two 1,000-watt motors, and I had never questioned that. However, while researching the issue today, I found that the front motor is a Bafang FM G06 750-watt motor and the rear is an RM G06 750-watt motor. WTF? Could the issue be related to the controllers, or was there possible motor damage from the electrical ground fault? Any help would be appreciated.
 
If it feels underpowered compared to before the controller was replaced and the motors were not replaced, most likely the controller is limiting the motor current (phase amps). That could be a programming issue. It could also be that the battery is unable to supply enough power to the controller. But if it is the same battery and you don't see voltage sag on the battery under load, that is not likely. A battery will develop internal resistance and lose capacity as it nears the end of its lifecycle. So even a well cared for battery will eventually need to be replaced.
 
thank you
If it feels underpowered compared to before the controller was replaced and the motors were not replaced, most likely the controller is limiting the motor current (phase amps). That could be a programming issue. It could also be that the battery is unable to supply enough power to the controller. But if it is the same battery and you don't see voltage sag on the battery under load, that is not likely. A battery will develop internal resistance and lose capacity as it nears the end of its lifecycle. So even a well cared for battery will eventually need to be replaced.
thank you, How do reprogram?
 
That depends on the controller. Sometimes through a configuration mode on the display. Sometimes through a separate programming cable connected to a laptop or PC. Sometimes the manufacturer locks it down so that only they or their authorized dealers can program it.
 
Just based on the age of the bike before reading everything in the OP, I was thinking battery. Bikes in northern climates typically sit the Winter in storage from the about the end of October to the end of March. That is five months or so. Batteries do not like that. And I agree about the controller programing. You likely have two controllers. I would first check voltage sag after a 15 mile ride. It could also be programed for the wrong voltage and or amps. A bike this week came in programed for 36V when it had a 48V battery.
 
Testing the battery should be pretty straightforward.
See if it will take a full charge.
Then test sag under load.
Temperature affect is more with charge/discharge... Not storage. That said, proper storage voltage is important
 
Just based on the age of the bike before reading everything in the OP, I was thinking battery. Bikes in northern climates typically sit the Winter in storage from the about the end of October to the end of March. That is five months or so. Batteries do not like that. And I agree about the controller programing. You likely have two controllers. I would first check voltage sag after a 15 mile ride. It could also be programed for the wrong voltage and or amps. A bike this week came in programed for 36V when it had a 48V battery.
I'll check for sag. I'm comfortable the battery situation is good. The battery that blew, was replaced with a new battery and it's a dual battery system so I expect one for sure is good.
 
Testing the battery should be pretty straightforward.
See if it will take a full charge.
Then test sag under load.
Temperature affect is more with charge/discharge... Not storage. That said, proper storage voltage is important
Both batteries are fully charged, One battery is brand new and a replacement for the single battery that was on when it to ground.
 
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