I can't see that would be a problem most modern chargers reduce there charging rate as the batteries come up to voltage so as not to overcharge the batteries. Make sure you don't place the charger on top of any thing flammable as they can get warm also make sure not to block any ventilation holes in the charger. if you are talking about a portable charger.
-- Edited by landy on Wednesday 29th of August 2018 09:43:25 PM
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You can only leave batteries on long term charge if the charger is capable of performing a "Float charge". This means it must be in constant voltage charge mode and maintain a terminal voltage around 13V7.
If the charger cannot charge in this manner it will degrade and possibly destroy the batteries. Tell us the charger make and model and we'll try to provide more info.
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