Is leaving a circuit breaker open bad?

Burrrrrton

New Member
The later model Rangers have a current shunt on the battery negative. All negative connections must be on the chassis side of this, including the main vehicle chassis earth. This is so the so called smart alternator can adjust it's output according to load.

If you put a large load (eg 2nd battery charging) on the wrong side of the shunt, the vehicle computer won't adjust the alternator output to compensate, so it will run the start battery down. They only charge the start battery to about 85% anyway, by design.

I have a 2020 Ranger, 140aH AGM battery and Redarc BCDC in the tray, earthed to chassis behind the cab. Never had a problem in this vehicle or the identical setup in my previous BT50 (non-smart alternator in the older Mazda).

Thank you. Helpful and detailed explanations. I have not encountered a similar problem, but for the future I will already know. The main thing is not to accidentally forget.
 

yorke7

New Member
I moved the grounding of the aux battery to the chassis and took it back to supercheap to get the starter tested again, that solved whatever problem was stopping them from being able to test it but turns out the starter battery is on the way out anyway. Thanks for the input everyone, glad i was able to fix the grounding before anything went too wrong.

Much appreciated,
Cheers.
 

Bru9

Active Member
and took it back to supercheap to get the starter tested again
Oh no! you didnt?
Your just wasting money and time (time is money to non philistines)
In my glove box is a quality battery tester I got from china that checks the impedance, very accurate and powerful metric, not the toys you get at the hardware. I use it to get a baseline when new and check every few years. Testing your batteries is something you gotta do frequently and on your own. Also observing the taper current at correct absorb voltages and open circuit voltages will usually give a good idea. I never use a "load tester" just start my car when battery is at ~ 50-80% charge and can tell straight away if its healthy.
 

yorke7

New Member
Oh no! you didnt?
Your just wasting money and time (time is money to non philistines)
In my glove box is a quality battery tester I got from china that checks the impedance, very accurate and powerful metric, not the toys you get at the hardware. I use it to get a baseline when new and check every few years. Testing your batteries is something you gotta do frequently and on your own. Also observing the taper current at correct absorb voltages and open circuit voltages will usually give a good idea. I never use a "load tester" just start my car when battery is at ~ 50-80% charge and can tell straight away if its healthy.
Money is also money bud! Supercheap testing is free, 2 mins down the road for me and doesn't require the purchasing of a Chinese product. Also you may want to give this a read: https://www.dictionary.com/e/your-vs-youre/ (you're welcome)
 
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