if you read the manual that is not how the back up battery works from my understanding, the battery back up works like a power bank to recharge the built in battery I also do not connect the cable from the power bank to the legend I carry the back up battery power bank in the holder but do not attach the cable to the Legend, from my understanding the back up power bank is used to recharge the onboard battery in the legend when the onboard battery gets low, you could do the same thing with one of those backup power banks that you carry in your car (the type that comes with a small set of jumper cables )as long as it had USB ports on the power bank, to plug the Legend charge cable into, the backup power bank that comes with the Legend in the pro pack is basically the same thing
Im no expert in metal detectors but do have quite a bit of knowledge about how litho batteries work. To my understanding same as if you hook up a external battery pack( power bank)to a cell phone.
Take the mophie external battery for example. It’s basically a power bank in a case. You put your phone inside the case hooked into the charging port of your phone. The case(power bank) has its own charging port.
As your phone is being used the internal battery is drawing power but at the same time the (power bank) attached to it is also keeping a constant charge going to it, like having it plugged in to wall charger therefore depleting the external power bank first before the the actual internal battery is depleted.
If the power bank( external battery) is attached it doesn’t know to wait until the internal battery ( also just a power bank) is completely drained before it starts to charge it. So the internal battery stays fully charged until the external one is completely dead then it starts using the internal charge.
If you look up the instructions on how it works it clearly states it draws from the external one first then the internal. Again a good thing because most the wear will be on the external battery. All rechargeable batteries, power banks, only have so many charge cycles so why use up the charge cycles on your internal one first.
Personally i would rather use up the external(power bank) because replacing the internal one requires sending it in to be replaced. One reason not a fan of internal batteries.
There could also be software that actually keeps track of the voltage of the internal battery and once it gets to a certain level only then does it tell the external battery to send a charge to recharge it. I am assuming it is the more simpler method being used. Usually having software to regulate charging like that is in more complex situations.
Another similar analogy would be your car.
While running your alternator( external power bank) is actually supplying power to everything while keeping your battery charged. Other than starting your car doesn’t draw from battery first. Maybe not greatest example but just the chain in order.
Maybe NM can clarify if it indeed has software to only draw from the inside first before using the external, I don’t recall reading that in the manual. Otherwise to me if you have the external attached already while hunting it only makes sense to have it plugged in. But this is a free country you can hunt with your detector turned off if you so desire.
If anyone can find out how NM actually has it set up that would be great
