I have an issue where the battery goes from 50% to 10% in about 10 minutes when I use it. 468 cycles. I sent it in for repair, and they said they just needed to rebalance it.

My other two batteries have a difference of 0.01V between the highest and lowest cells, but this battery has a difference of 0.15V.

From my reading, this big a difference in V between the cells is a problem and points to problems.

What is my recourse? Do I send it in again for rebalancing, or can I dictate that they either fix it by replacing the cells or that they replace it with a battery with the same cycle count? How do I enforce the 10-year warranty?

Has anyone had issues with a sunsynk battery that they had to replace?

Just FYI the last rebalance took 5 months for me to get it back.

Hi There,

Is it not a function of the BMS to keep the cells in balance?

How are you reading the cell voltages?

5 months to get your battery returned......you must be kidding !!!

Contact Keith Gough directly.......

Solarassistant gives more details about your battery. So it show cell voltage

I had a similar issue with my newest purchased Leoch 48100-S pack. From the beginning cell 15 showed significantly higher voltage at charge and lower at discharge. This being a brand-new pack I contacted the official importer and seller, Averge, with a guarantee claim. But they didn't want to do anything about it. I asked to allow me to open the pack without voiding the guarantee to check the cells connections. They wrote me the permission and so I did. I tightened all M4 hexagon bolts of the cell bridges with a socket wrench. Some allowed up to a half turn. After reassembly and re-connection the issue with cell 15 no longer persists. It looks like all cells run the same voltage within a few mV. This proves to me that all cells are in good health.

As @Beat mentioned, most of these issues typically are related to loose connections, or balancing issues. Since it was already rebalanced, it's probably a loose connection.

A good way to diagnose it, is if the lowest cell is always consistently the same when top balancing it, or when reaching a full charge.

This is mainly why I can never get behind off the shelve batteries. Fixing a simple issues voids your warranty, and retightening the nuts is a maintenance item.

13 hours ago, rterblanche said:

Solarassistant gives more details about your battery. So it show cell voltage

It shows 3 values only, Highest, Lowest and Average for all cells.
It does not show which cell either unfortunately