Firstly a deep cycle deltec battery is not a lead acid battery. Its a sealed calcium battery that doesn't charge the same as lead acid. the way u are charging ur battery WILL reduce its life and won't be charging the battery to its full capacity. Another thing u must know is that u must never leave the battery uncharged for a long time as the de energised plates start to oxidise thus causing the battery to loose life \ hold its charge. And lastly never leave cheapo charger connected to the bat. U could have a nasty leak or explosion on your hands. Just trying to help Mate! U may as well carry on using ur cheapo charger but when u need a new battery invest in a multi stage intelligent charger, that can be left charging inevitably.