Optimate connecting instructions - humour me

[SometimesSansEngine]

So I've had delivery of an Optimate solar charging kit for when the bikes are in the shed.

The instructions (which aren't exactly the easiest and most thrilling read for a relatively normal person) are very clear, if connecting up with the battery in situ with the crocodile clips, connect the positive connector to the battery, then the other to a metal part of the chassis/engine block away from the battery.

Yet all the pictures on the box, on their website etc show you connecting the black lead to the negative terminal.

Further if you want to leave a plug situ, you can connect the ring terminals/y lead with the weatherproof connector.

Not that the info will change much, I'll be using the ring terminals on our bikes, but it's just for my idle curiosity as I haven't a clue about these things. Why would grounding the crocodile clips on the chassis be suggested, yet the ring terminals... and pictures of the crocodile clips in use.... go straight on the negative terminal?

[raesewell]

You can connect to either, chassis or negative terminal. Sometimes it may be easier to connect to the chassis if there is limited access.

[WD-40]

I think it's because when you charge a battery it gives off hydrogen and oxygen gases. They can ignite from the spark caused by removing the charger clamps. I remember watching a mechanics show on Discovery channel a few years ago called Jock's Garage and the guy was charging a battery that was located in the car's boot. The gases from the battery must have got trapped in the boot because when he took the charging clamp off the battery it blew up in his face and got acid all of the boot of the car

[TimR]

Reason being as with any removable form of connectionit is so that you are more likely to connect to the correct terminal .

Same principle as jump leads but with those it is so that you don't also 'spike' the ecu which can occur if uour5 connected to the battery direct with both leads.

Remember Connecting & disconnecting battery terminals follow the following to minimise any potential short circuits or sparks

Disconnect earth lead first then positive

So on event of spanner touching chassis or dropping posiive lead it can't earth out

And reverse for connecting

Positive first and then earth ..