1999 mazda miata battery does not have pos or neg stamped on battery and both cables are black so its hard to tell which cables to attach for recharging...

If all you are doing is changing to a side post battery, just connect all the positive cables from the old pos post to the new pos holder and all the neg ones to the new neg holder. If you've already cut them all off and not sure where each wire goes, all the reds are positive, all the blacks are neg. To make sure use your continuity meter to test. Connect one meter lead to any good clean metal part on the car and test between each black wire in turn, the neg ones will show a circuit, the pos ones will not.

should be red pos, black neg.

Pull off the neg and use jumper cables connected to another vehicles battery. Attach the jumper normally on the other vehicle, attach the Pos to your battery pos and then attach the neg jumper cable to the disconnected neg cable on your truck. My suspicion is that your battery may test well with a volt meter but cannot take any load on it. It should be floating at 13.5 to 13.8, not 12vdc.

I should tell you running the car with the battery disconnected can cook the alternator and the engine computer. The alternator needs the battery in the circuit to keep power flowing in the right direction.

Generally speaking it has some red on it normally the negative cable has black on it. The negative (-) cable goes to the engine block or grounded on the frame. The positive (+) cable goes to the fuse block, or the starter. This is the general case for all cars.

The negative battery cable is black and the positive battery cable is red.
The positive battery cable will lead to the starter while the negative battery cable will connect to the body of the car which is negatively grounded.

Always remove the neg. battery cable first, and then the pos. battery cable second. And install in the opposite direction, pos. battery cable first, and then finally the neg. battery cable to the battery.

Also, many batteries have the (+) and (-) posts labeled in an embossed fashion on the plastic case.

Do not reverse, or else the vehicle's electronics can be fried.

Good luck on this repair.

hook them up in parallel, pos to pos, neg to neg from one battery to another, then pos cable to battery prs and ground cable to neg battery

Get a New battery that one is stuffed.

yes just jack up so can slide under, most to remove will be the cable brackets which hold them down, not hard to do

it is in the trunk under the mat not to hard remove the mat take off the cables disconect hold strap replace the battery replace strap cables and mat just make shure you pot pos cable on pos and neg cable on neg