lead Acid units? what size are they? would say that Lead Sulphate build up lowers storage capacity, depending on size they could be reconditioned by a professional but can be expensive, Gel batteries Lithium etc have different service lifecycles......are they large size batteries in a battery area in a plant room? Google Alber Battery, its a company in the USA (Florida) that I have had dealings with before, they have a lot of information available about Battery maintenance and servicing, manuals etc.....they hold a big battery conference in the USA every year ......they do testers like the Celcorder unit, Battery electrolyte Hygrometer etc, they can post you free handbooks/ battery information and software on DVD etc from the states......you can print out information from their website to use for reference and show your customers etc showing reasons for changing/maintaining industrial batteries...