What on earth is that !?  Yixiang LiFePo4 Battery case vibration - Page 1
Forum section: electronics / beginners

author: hgg
author_rank: Frequent Contributor
timestamp: May 03, 2025, 07:17:46 am
content: Hi,I have the Yixiang 48V LiFePo4 DIY battery box and when I use the kitchen oven and drawing 3.4kW,the battery case is vibrating!I noticed it by accident when I touched the case. Only the side of the positive terminal isvibrating. It feels like a small fan, but there are no fans. The inverter is completely isolatedfrom the wall with rubber mounts and produces no vibration anyway. There is no AC voltageon the case.In each frame of the video (5 sec) you can see 18 oscillations and if you look closely at eachone you can measure around 13 to 14 high frequency oscillations as well.(Measured with the smartphone's vibration sensor.) 18 x 13 = around 234HzYou can measure on the inverter output, switching noise 200 to 300Hz(measured on PE - Neutral)What is happening here? Is it possible that the inverter switching noise is vibratingthe positive terminal under high load(no heat at cables, batteries, inverter)Everything is working smoothly except the vibrating positive terminal.When 2kW are pushed back into the battery from solar charging, there is zero vibration.Any ideas?

author: TERRA Operative
author_rank: Super Contributor
timestamp: May 03, 2025, 09:05:22 am
content: My first thought is magnetics in the inverter under heavy load are causing other magnetic things nearby to vibrate.

author: hgg
author_rank: Frequent Contributor
timestamp: May 03, 2025, 09:10:55 am
content: What do you mean magnetics in the inverter?Solar is right now pushing 2.4kW back into the battery with no vibrations whatsoever.

author: amyk
author_rank: Super Contributor
timestamp: May 04, 2025, 02:15:38 am
content: 3.4kW at 48W is around 70A. The inverter may be drawing pulses of current more than that, and the resulting magnetic forces on the wires making them vibrate.

author: radiolistener
author_rank: Super Contributor
timestamp: May 04, 2025, 02:37:09 am
content: My 80W linear lab PSU vibrating pretty high during power on. With 3 kW power it can be much more significant. I think the main vibration component in your case is transformer/inductor.

author: mikerj
author_rank: Super Contributor
timestamp: May 05, 2025, 01:19:02 pm
content: Quote from: radiolistener on May 04, 2025, 02:37:09 amAs far as I can tell the the YIXIANG battery box is just a bunch of cells in a box with a BMS, there is no inverter built in:https://szsyixiang.com/yixiang-48v-16s-diy-lifepo4-battery-box-jk-200a-bms/

author: Vovk_Z
author_rank: Super Contributor
timestamp: May 06, 2025, 12:56:20 pm
content: Quote from: amyk on May 04, 2025, 02:15:38 amI agree, that may be current pulses (inverter own consumption). So the vibration can be a result force of attraction or repulsion between two current-carrying wires (is often called Ampère's force law).Or BMS have some small vibrating DC-DC (?).Or a vibration goes through thick DC wires from the inverter itself.

author: thm_w
author_rank: Super Contributor
timestamp: May 07, 2025, 12:55:29 am
content: The battery box has no major DC/DC in it, or inductive filtering. You can see from the photos online:https://www.aliexpress.us/item/3256807107302953.htmlIt does have this BMS inside, with an inductor:https://www.jkbms.com/product/jk-pb2a16s20p-jk-pb2a16s-20p/But that should only draw a small current to power the circuitry.It does have active balancing, but that is also only 1-2A, not so much to cause low frequency vibration.My guess is what amyk says above, 70A is a lot, this can cause vibrations in the wires alone.