What difference does it make if they are connected in the opposite order? This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.
The reason I would connect the positive cable first in a negatively-earthed car is that while tightening the positive connector with a spanner wrenchif I were to touch the body of the car with the spanner at the same time, nothing would happen and I would be OK. However if the negative was already connected to the battery and I shorted the positive to the body with the spanner, there would now be a short circuit with a big spark and a possible fire.
For the same reason I would disconnect the negative connector first too. The whole body of the car is usually connected to the minus pole. And you can accidentally hit that body with the positive lead. So connecting the lead first is safer. Only a small part of the car is now connected to power.
If you mess up by touching the car with the other lead nothing will happen. This might also be a habits for people who deal with electronics. Home Questions Tags Users Unanswered. When reconnecting a battery, why connect the positive first? This question already has an answer here: Nick T 4. HandyHowie 9, 1 11 Random link from the first page of Google results, among many, many more.
Positive first, and last. It is a shame the instructions in the link didn't say why they should be done in that order.
Ah yes, I got them the wrong way round in my question Should say "positive lead first" dammit. For technical functioning it does not matter in which order you connect them. However for safety reasons it does matter.
Whole car except a few parts like the positive pole are connected. Any mistake with the other lead will lead to a short.
You really do not want this. Depending on your point of view and your desire to prevent harm. Hennes 4 It does matter which you connect last which HandyHowie points out in his answer. This is true of any negatively grounded earthed vehicle, which is the vast majority of vehicles on the road today.
Besides accidentally hitting the car body when tightening the bolt on the positive lead? Everything you wrote is correct. The rule is just for safety, as you wrote in your last point. This is very important, because a car battery is strong enough to melt a wrench when touching bith poles. So, a short circuit is a little more than just a few sparks.
Hydrogen isn't such an issue. May be, you should have emphaised this more. Unfortunately, sweber, hydrogen is still an issue with flooded lead-acid FLA batteries. Please read this publication about FLAB and water decomposition.
It hydrogen and oxygen are produced from FLA batteries under normal conditions without the battery being charged or discharged.
It also states the gasses are produced in higher quantities when the heat is turned up. The page has to do with FLA batteries when used in power backups, but still applies to vehicles in general. Hook up positive or negative first, you have convinced me. Recycle your battery at your local Pep Boys; Make sure you're connecting the wires to the correct Detach the negative (black) battery cable from the battery.
First loosen the nut with a combination wrench. Twist and pull up on the end of the cable with your hand.
Attach and tighten the positive battery cable (Red). Connect to the positive cable to the positive terminal of the weak battery. order: Hook up positive or negative first remove the negative cable from the car you jumped, then the negative. In a DC battery source when the negative terminal is grounded, why do we connect the fuse on a positive terminal side and load on a negative t What happens when you attach the negative battery cable to the car battery before attaching the positive cable battery?.