All Victron batteries must have a manufacturing error after a lot of test and research on around 300 batteries from Victron mainly super cycle 25AH over 250 and 18 batteries Gel Deep Cycle 220Ah.
Most of the super cycle they fail within 6 months to 1 year even if you have them on float voltage and not cycling them, if cycling them on a solar system best you can get is 6 months. 30% got a catastrophic effect of swelling. Other manufacture of batteries with 4 year floating still there and running without a problem the only difference is that is 18Ah instead of 25Ah.
After 1year of using them new ones with serial numbers came out thinking they fixed the problem but at the end they all failed from 25Ah day one measured with a proper load tester they all end up at 3Ah the ones that are always on float voltage , the ones doing cycles are 100% dead. It was a big loss for us and there is no support or guaranty from our local dealer since they are not replying to our calls. They tried at the beginning to help but that didn't help since there is no response.
The 220Ah at a controlled environment at 25-30 degrees Celsius 70% state of charge as a discharge they get a half capacity if not less on some of them after 1 year.
After 1 year and 2 months it was failing cause of some of the cells in series of the 4 was actually close to 50Ah and some on 119Ah on 2 strings parallel of 4 in series.
All batteries show a good voltage like a new graph but with the difference of the capacity instead of 220Ah there new capacity 120Ah or 50Ah, on the small ones 25Ah when new but after 6 months to 1 year 3Ah if not swelling.
Note that internal resistance was measured but it can’t be trusted since it was showing good on a lot of cases but the capacity was not there, most test where done with C20 and C10 when new even C2 was good.
Hope this 2 year test and research on Victron batteries will help.
What is your experience with the Victron Lead Acid Batteries?