Just something worth mentioning....I have a Schumacher 12/8/2A Speed Battery Charger that I bought from Walmart about 10-12 years ago. When I connect it to any battery and don't touch any of the settings...it tells me the battery is bad. But, if I press the button to set it to deep cycle (RV battery) and then set it for 2A charge, it kicks on, gives me a reading of percentage charged and current Amp output and it works like normal. I don't know if you happen to be using the same kind of charger, but if so...this has been my experience ever since I bought it.
Where we've been:
2000 Rockwood Roo M-18 Hybrid
2006 Dodge Ram 2500 Auto 5.9 Diesel
Gone but not forgotten -1986 Rockwood 1003 PUP