noob needs new pack

P

porter

1 µW
Joined
Apr 6, 2016
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3
Hi,
New here, with practically no electrical knowledge, I've enjoyed a 2013 build by someone else who is no longer around. Now it's time to replace batteries (made the big mistake of fogetting to recharge a very depleted pack so most modules died). My question: Can I replace my 72 volt LiPo pack with a 52 volt (Luna Cycle) pack and expect it to work safely if connected to my 18 FET IRFB4110 controller or does that need to be reprogrammed or replaced? Anything else I'm unaware of? I already assume there'd be less power and shorter range. Or anyone have recommendations for a low priced (like Luna's) 72v pack?
Thanks in advance for your time and expert advice.
Porter,
Greater Toronto Area
 
You can indeed run a lower voltage pack to reduce the speed. The decrease in speed should be roughly proportional to the decrease in voltage. 50mph @ 72v should be around 35mph @52v. You don't even need to give up any range if you get a pack with the same overall watt hour capacity (votage * Ah). A 72v 10ah pack is 720 watt hours. A 52v 15ah pack is 780ah. So the range would be about the same.

Depending on where the controller is from you may need to change some things to run at the lower voltage. Some controllers come ready to run at a wide range of voltages and some do not. If it is one that does not, you will need program the low voltage cutoff to a lower value since the controller would think 52v was a dead 72v pack. If the controller already has a programming connector then its a relatively easy process only requiring a cheap cable. You may also need to change a resistor or 2 to keep it happy. Don't let that scare you. The resistors are big and easy to access inside the controller so its a good beginner soldering project.

Do you know where the controller is from?
 
Thanks Dan,
All I know about the controller is from the builder's email to me in 2013:
- Monster @EV 18 FET IRFB4110 controller.
Features: 5kW peak output, 9AWG power wiring, high quality connectors, an X8M06 microproccessor, German components, eighteen genuine 4110 FETs, and waterproof.
Porter
 
Im not sure about the monster thing. Lyen controllers are very common and he calls some of his monsters but I thought that was only the 6 FET versions. Most of his controllers are grey.

First thing I would do is check to see if you have a programming cable coming out of the controller. The programing output will be a 5 pin cable that is not being used for anything else on the bike. Next, If you remove the 4 screws that hold on the end plate on the non wire side you should be able to see the input power resistors I was talking about. You may also be able to identify the number on the circuit board. That would be a big help in figuring out which software settings to use to program it and which programming cable to use.

Here is a very informative post about common ebike controllers. https://endless-sphere.com/forums/viewtopic.php?f=16&t=7361
The input resistor info is the bottom part of the first post. There is a chart on which resistor values to run for common max voltages. There is some wiggle room in these values so you might be ok if yours falls somewhere in between the 52 and 72v values. Hopefully someone with more experience can chime in if I am steering you wrong here. I have always modified the input resistors on my controllers to make sure they were correct but I am not sure exactly how much wiggle room there is.

Controllers are relatively inexpensive so If you really want to get the 52v pack and don't want to mess with the controller at all you can always get another one that is set for the lower voltage. I really enjoyed modding my controllers when I finally got over the initial fear of messing them up.
 
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