HoSS

+1 for blue sea, very good https://www.mudstuff.co.uk/dual-usb-socket.html

What charging profile are you talking about, please clarify. Lead-acid, AGM and deep cycle all use the same charging principle, constant voltage.

^ what he said. For 10% the cost of a CTEK you can get something that perfoms 95% as well. FWIW my solution is integrated into an arduino which monitors both batteries contents and chooses when to link or unlink the batteries (my own program), I also have a manual bypass switch for jumping or winch use.

The charged battery will charge the discharged one, its not all supplied from the alternator, and unless the VSR is switching in and out the load will not change. You're thinking about it the wrong way round. A lead acid is charged constant voltage (not constant current like NiCad, Lipo etc) its charge current is self defined by the fixed input voltage and the internal resistance.

Thats the part i disagree with. Alternators do not have an current sensing (except maybe the very new digital ones) the regulator provides a fixed output voltage, and that determines the battery termination. Both batteries will be taking the current they need based on internal resistance and the applied voltage. But connection is important, see this https://www.impactbattery.com/blog/tutorials/how-to-charge-marine-and-rv-batteries-in-parallel/

2 Batteries will charge slower than 1 as the current is split, but i dont see any reason why they will not reach 100% as the alternator voltage will still be the same at termination. Of course you are correct that the intelligent chargers are kinder on the batteries. But within a budget theres nothing wrong with the relay method.

If you have not bled correctly or a leak the brakes will be spongy. If you have lost vac assist they will be firm but need a lot of foot force. Different symptoms.

IIRC there a 3 different sender models (blue, yellow, green?) each for a different tx case ratio

I have a Clarke (machine mart) air ratchet thats been going strong for 15 years. And yes dead handy in certain circumstances - spinning stuff off long threads etc

I have a tri-power one. 230V / 12V / Gas 230 V if i have hook-up or generator 12 V en-route Gas when camping

Usually with these things the std is a certain number of vehicles (VINs), and the pro unlimited.

I would just watch how well the pot is mounted to the bracket, if it slips you might have no throttle or WOT when you dont want it.

Actually, reminds me back when i was a First Aider for my company, was chatting to one of the girls on the production line about where you can take a pulse (honest guv, dont tell the missus). She replies - "Wots a Carrot Archery?"

I find a good rough method of calibration is to check it against another torque wrench by coupling them together.

Probably why i binned it