Intermittant Power Shutdown While Riding

[tomjasz]

A 14S8P made with used 18650's with compression contacts is going to be problematic.

What is the kit? If a Vruzend kit and you're having cells lose contact it's a poor build on the OP's part. I have had every Vruzend kit version made and the devil is in the building details, not in the kit.

 

[quasimodo]

A 14S8P made with used 18650's with compression contacts is going to be problematic.

Now that you said it started after a bump, I understand. You probably should probe every cell in each 8P group to see if they're at the same voltage as their neighbors. That might reveal any bad contacts.

Check your balance. Are all 14S groups more or less at the same voltage?

You have a weak series group in there sagging below the BMS' LVC (low voltage cutoff). Maybe it will be spotted with your series voltage test.

Hi Harry...Yes, it looks like I will be busy this weekend checking voltages. I just purchased a device that supposedly checks motor, controller, and throttle, brakes and 5 volt terminal. Will see if it offers any clues. I still think it is a bad connection somewhere in the battery, but ??..Thanks for your input.

 

[quasimodo]

What is the kit? If a Vruzend kit and you're having cells lose contact it's a poor build on the OP's part. I have had every Vruzend kit version made and the devil is in the building details, not in the kit.

Thomas...Yes, it is a Vruzend kit. Not the latest one, but the one just before it with the red and blue end caps. I bought the BMS off of the same site. It was fun putting the pack together but rather tedious. I used all the strongest cells I had to build the battery pack, but like I said, I am a novice at this electronic stuff. Up until now, all I have used is my digital voltmeter. Thanks for your help.

 

[harryS]

Here's one bad connection scenario.

A bad connection could knock one of your series strings from 8P down to let's say 5P. Now that string will deplete faster than the other 13, and maybe it's just a half volt lower. As soon it hits 2.8-3.0 volts, battery shuts off. Other's are at 3.6V,

When you charge it, the charger shuts off as soon as one of the other groups hits full charge (4.2V) and that 5P group cannot not catch up. So it will go out early again and shut the battery down. EVen if it does catch up with balance, it will go out early. ALl of this assumes none of the other cells work loose.

While Tom can make his Vruzend work, I've seen a few posts in other forums where the owner had the connections popping loose. Usually the bigger packs are hard to keep in tune.

 

[tomjasz]

Thomas...Yes, it is a Vruzend kit. Not the latest one, but the one just before it with the red and blue end caps. I bought the BMS off of the same site. It was fun putting the pack together but rather tedious. I used all the strongest cells I had to build the battery pack, but like I said, I am a novice at this electronic stuff. Up until now, all I have used is my digital voltmeter. Thanks for your help.

So did you make certain the caps are all compressed? With some sort of hard plate on top and bottom to reduce any movement? As harry s wrote you might want to recheck all connections and cells.

 

[tomjasz]

Here's one bad connection scenario.

A bad connection could knock one of your series strings from 8P down to let's say 5P. Now that string will deplete faster than the other 13, and maybe it's just a half volt lower. As soon it hits 2.8-3.0 volts, battery shuts off. Other's are at 3.6V,

When you charge it, the charger shuts off as soon as one of the other groups hits full charge (4.2V) and that 5P group cannot not catch up. So it will go out early again and shut the battery down. EVen if it does catch up with balance, it will go out early. ALl of this assumes none of the other cells work loose.

While Tom can make his Vruzend work, I've seen a few posts in other forums where the owner had the connections popping loose. Usually the bigger packs are hard to keep in tune.

Sound advice Harry! In my experience, the failures are most often due to some cells being slightly wider with the earliest kits. And not using a pressure plate top and bottom. The newest have evolved to nickel-coated copper and better plastics AND long bolts to snug down top and bottom compression plates.

 

[quasimodo]

Thanks Fellers for your tips and input. I just bought the Turnigy 180amp Watt meter and will use it to do some testing. I think, begore that, I will take the expose the cells and check the connections. I need to redo the BMS connections anyhow because I was told initially to just stick the bare wires under the connectors and tighten down. I have since saw a video that showed this to be wrong and I want to correct it . It said that you lose a lot of the connection on the nickel connector pad when you put it underneath. makes sense to me. Think I will put a connector on the wires and install them on top under the little nut instead. Thanks again guys, and I will post back when I find out anything.