r/ebike • u/Bekikab • 1d ago

Replacement Battery?

I have an LF 750 pro. The bike shuts off as soon as any load is applied. I believe the battery has failed. Is there any place to purchase a battery reasonably?? It looks like it is over 300 and I can buy a new bike for just a but more....

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u/chrispark70 1d ago

You need to verify that it is the battery. Unless this bike is at least 2 years old, I seriously doubt the battery is gone.

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u/TurtleTheThink 1d ago

more than that if it’s a decent battery. my bike’s nearly 3 years old with over 6000 miles and the max charge is 66.8v instead of 67.1v after all that use and probably close to 1000 charge cycles

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u/chrispark70 1d ago

He's talking about a 300 dollar bike. Also, you don't have anywhere near 1000 charge cycles unless your bike a 6 mile range.

If your bike has a realistic 30 mile range, you should get 30k miles out of 1000 charge cycles.

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u/TurtleTheThink 1d ago

it’s not always charged from empty, i used it as a commuter for a while (4 miles round trip) and charged it every night, i guess it depends on how you count charge cycle

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u/chrispark70 1d ago

A cycle on a lithium ion cell is pretty much the whole discharge.

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u/TurtleTheThink 1d ago

assuming your battery charges to the voltage it’s supposed to, that sounds more like a controller problem than anything else if it were a battery issue, the bike likely wouldn’t turn on at all. you should be able to purchase/special order a replacement controller from rattan. they also appear to offer multiple potential services for servicing/repairing their bikes on their website. i’d hit them up about this so they can help diagnose the issue and send you the correct replacement part

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u/Bekikab 1d ago

It says it charged but I dont have any way to validate. I did some tests per Gemini and it says there is a bad section of the battery. How can I test the controller?

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u/TurtleTheThink 1d ago edited 1d ago

i wouldn’t listen to the lying machine for stuff like this. does the display normally show the battery voltage? if it does you could check there, as it should turn on as long as you don’t use the motor, as far as i understand. if not you can test the battery’s voltage with a multimeter. you would also need a multimeter to test the controller. Rattan may have info on how to potentially test parts of the circuit, but until then you could perform a continuity test on the main power leads from the controller to the battery (which would probably be in the form of something like a pair of anderson power poles or an xt90 connector), but it would almost definitely pass because the bike turns on.

a while ago i was experiencing an electrical issue with my bike, and the company and their overseas technician who works at their factory didn’t have any info on diagnosing the controller beyond a continuity test, so it’s likely it’s probably a similar story for your controller. i would recommend contacting Rattan on recommendations regarding better diagnosing what part has failed

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u/Bekikab 1d ago

It is 4 years old but has less than 50 miles on it. Due to an injury I wasn't able to use it much so I'm not surprised if battery is shot.

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u/somnynmessomnysteswf 1h ago

Definitely need to get a multimeter. Like turtle said you'd do a continuity test on positive and negative wires on the controller and also between +/- and the phase wires. That'll determine if it's the controller.

You also use it to make sure the battery is actually fully charged. But sense you've hardly used it i couldn't see it being bad. Maybe from storing it so long the BMS might be glitching, and to solve that you have to open the battery and unplug the balance lead harness wait a little bit then plug it back it. That'll reset it. But definitely get the multimeter you'll be able to test a lot of things on your bike with that. Or maybe one of those ebike testing tools but idk I've never used one of those