Most chargers do not have the smarts to stop charging when the battery is full. When a lead acid battery is charging, some of the liquid gets converted to hydrogen and oxygen gas, and gets vented (which is why it is important to have a vent on these batteries). If you leave it always trickling, you'll lose a significant amount of the liquid (and most batteries now a days are sealed, so you can't add distilled water to replace the vented gas). Once the lead is exposed, you've effectively killed the battery. 

> On Feb 5, 2020, at 11:06 AM, Eric Caron <ericcaron96@COMCAST.NET> wrote:
> 
> Funny, I was thinking the same thing.  
> 
> Glad you asked for more details.
> 
> I tried hard to get a trickle charger set up on my batteries to preserve them.
> Not all the chargers are created equal but I didn’t thing there was harm to a trickle charger. 
> 
> Now looking for a charger that can stay out of sight in my bus and either fast charge or trickle charge depending on the need. Have plugged in so that once I connect to shore power it just works.
> 
> But, I certainly hope my current system does more good than harm.
> 
> Eric Caron 
> 85 GL Auto 
> 
> 
>> On Feb 5, 2020, at 10:53 AM, OlRivrRat <OlRivrRat@COMCAST.NET> wrote:
>> 
>> On 4 Feb , 2020, at 6:08 AM, Dennis Haynes wrote:
>> 
>>> Leaving them on trickle or other dumb chargers will also do them in.
>> 
>>               DH
>> 
>>       As You always seem to be able to do so eloquently > Would You please expound on this a bit ~