the next dayi drove over 100miles when i checked them with a hydrometer it still showed the batteries as being discharged....am i wrong in thinking they should have charged up?....or do i have to drive all damn day to replenish?
IIRC, you have the capability with everything being perfect, of charging your batteries at 20 amps through your vehicle's charging system.
If you have two batteries, you are charging them at a maximum of 10 amps each.
Think of a battery as a one gallon milk jug. One gallon is 128 ounces. If you fill the jug at a rate of 10 ounces per hour, it will take 12.8 hours to fill the jug.
A deep cycle battery accepts a charge slightly differently, but it still takes quite a while to charge it fully.
Without going into a huge discourse on battery theory, Brett is right, you could have one bad cell in one battery that is draining both of them. Another possibility is that if the batteries have not been used/charged for a long time, they could have become sulfated. That means the Sulphur in the battery acid has coated the lead plates, drasticalliy reducing the batteries' capacity.
The best thing to do with them is to disconnect them both from the trailer, make sure they have enough water in the cells to cover the tops of the plates (don't fill to the top, it will overflow), and charge them both until the hydrometer reads at least 1.265.
Allow them both to sit undisturbed for about 24 hours, then check again with a hydrometer. If they both still read 1.265 on all cells, hook them up to the trailer, and go from there.
I am getting a real charge from this electrifying thread...