Guess I should have know better than to trust a sales man......
Quoted from Wikipedia
" A deep-cycle battery is a lead-acid battery designed to be regularly deeply discharged using most of its capacity. In contrast, starter batteries (e.g. most automotive batteries) are designed to deliver short, high-current bursts for cranking the engine, thus frequently discharged of only a very small part of their capacity. While a deep-cycle battery can be used as a starting battery, the lower "cranking amps" imply that an oversized battery may be required.
A deep-cycle battery is designed to discharge between 50% and 80% depending on the manufacturer and construction of the battery. Although these batteries can be cycled down to 20% charge, the best lifespan vs cost method is to keep the average cycle at about 50% discharge,[1] as there is a direct correlation between depth of discharge on the battery and the number of charge and discharge cycles it can perform.[2] "
Sad part is our company does quite bait of business with this guy. Was well worth the couple hrs of my time reading up on batteries for myself.