Power max converter keeps blowing 30 amp fuses

The two 12s are in parallel ok in that old photo. Your negs go on the neg of one battery and the pos wires go on the pos of the other battery. Your negs are on the top left so all the pos go on the top right with the batteries reversed like that.

Your reds should go to the same post on the one battery, not one to each.

I am not sure what the white wire is there, so you would need a meter to check if it is pos or neg.

Disconnect the DC wires into the converter and check the voltage across them for that 26v. It should be more like 12.7 with new batteries in parallel.

Did you put the new batteries in the same way, reversed, or if they are now lying the same way, but wired the same, that might get them in series and 26v.

Haha sorry this is an old photo! I have new batteries in now with the same wiring as the old.

The top left is three black wires (ground) and the top right has one red wire

That cloth covered white looks like it goes to a fuse so probably correct on the positive.

Hard to tell what is at the top of the picture in the shadows.

Eight years on Everstart is pretty dang good BTW.

So would I need to put that white wire some where else?

Red (pos) and white (neg) load wires to the same post?

26v DC sounds like two times 13v, which you would get with your 12v batteries in series instead of parallel.

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