Sudden Coach Battery Failure

[gksmith]

I was recently surprised by sudden complete failure of both of my coach batteries! I have not used my 2003 LT Van this summer, as I had it for sale due to my purchase of a new Panoramic Van. I have been showing it periodically this summer, but have been traveling quite a bit in our new van. Hence, I have been gone for periods of time between showings. I am quite sure that earlier this summer my 12volt system was operating properly after sitting over winter. However, a couple of weeks ago, I noticed that the 12 volt lights would not turn on. I did not think too much about it and connected the van to shore power. I was in a rush for my next trip, so I did not do any further testing, and disconnected the shore power. But, a few days later, when showing it to another potential customer, I still did not have 12volt power in the coach, so I reconnected to shore power. Yesterday, I disconnected the shore power and found that I STILL do not have 12volt power when disconnected from the shore power. So, I tested my batteries, and they were badly discharged, but still showed low but some voltage. I checked the electrolyte levesl, which were fine. So, I put my farily late model baterry charger on the batteries and it subsequently showed "Battery Failure" on both disconnected batteries! Going through the repair mode on the chrager does not seem to help. So, I fear they are toast!

So, my question is, "Could something in the 12 volt system cause simultaneous complete battery failure?" I know that completely discharging lead acid batteries is bad for the batteries, and I admit that this is unfortuntately not the first time they have been abused by too much discharge, but I have never had complete battery failure! I do have a late model power convernter in the coach, so I believe they were properly recharged (if that is possible) while on shore power. I do not want to put new coach batteries in the unit and have them prematurely fail if it seems that there might be something wrong in my 12volt system other than possbile battery abuse and possible accidental deep battery drainage between showings.

Any comments or suggestions? Any testing I can do? Thanks in advance!

[GeorgeRa]

Small current drain overtime can discharge batteries if battery stays connected. If you didn't use your battery disconnect before extended storage battery will likely discharge. Try to charge them.

[michaelingp]

From your description it seems like the likely cause is you left the batteries in a totally discharged condition for considerable time, weeks or months. You can get away with discharging completely if you charge them in a timely fashion, like the next day but they will sulphate and be destroyed if you leave them for weeks or months. If you can disconnect the batteries completely from the 12V system, then they should last for months if they start fully charged (figure on 5% self-discharge per month), but if you cannot disconnect them, then a light or detectors can discharge them in a couple of weeks or less. Based on your description this seems more likely than a problem with the charging system. You cannot charge a battery once it is destroyed.

[SQUASHMIRE]

You need a dumb charger that does not analyze batteries. Like the one I have from 1970. The batteries will likely charge and then when they are mostly charged you can switch to your so-called smart charger.