I read a lot about chargers failing.
I used to be in a business that did a lot of land surveying. The instruments used in the field used 12 volt agm batteries. These batteries were used hard. In very harsh conditions on construction sites. 365 days a year. Only tough chargers could tolerate the field conditions of the temperatures in the summer on the ground close to 110 degrees and in the winters cold, wet and muddy conditions found on these construction sites. These batteries were being used or being charged, all of the time. The sophisticated chargers I used were made by zivan. They were very smart, it did not matter what state the battery was in, cold, hot, discharged, it sensed the batteries condition and charged the batteries properly every time.
Now, I used to own a boat with gel cell trolling batteries. Big heavy 90 pound batteries. Again, tough chargers to charge these after a day fishing.
Now, I certainly did not think a little tiny 1 lb 5 amp charger, my soneil 2409 is a 4.5 amp charger, was going to last long with daily charging a 864 watt hour pack 2 times a day. That I got 8 months use with this charger on this bike actually surprised me. Actually it shocked me! I only bought it because it was the only charger I could find that could be left hooked up to the battery all of the time. It has no cooling fan, it ran very hot every charge. I thought, based on my previous experience charging batteries for 25 years, that the little soneil did an outstanding job! Except for the fact that the soneil charger does not sense the internal temprature of the battery it is charging, I would certainly purchase these in the size necessary for my pack.
A charger needs to be matched to the size of the battery to prevent overloading and overheating the charger so that it can charge properly. I suspect I should be using chargers with an output of about 36 amps for my agm battery pack of 864 watts. When I was in contruction and in my boating experience, the chargers always cost more than the batteries. Good chargers lead to good battery life. Cheap chargers lead to very poor battery life. And, cheap chargers don't last long.
In my experience, the charger is as important as the battery, and, in my opinion, the charger should cost more than the batteries they are charging. I used cheap chargers and burnt up quite a few batteries, I learned my lesson, I never lost a battery when using a good charger.