Fix or replacement for battery with 12v DC output

I’ve got two Anker Astro Pros, 20000 mAh. I got them because of the form factor and also because they can output 9v / 12v DC which I use to power a field audio recorder. Unfortunately I think they’ve been over-discharged or I went too long between chargings at some point because now it seems like they have trouble maintaining a full 12v output, as frequently my recorder will have to swap from the external battery to the internal AA’s. This is an issue because the recorder can burn through eight AAs in just a few hours. Pressing the button on the side will wake it back up and it’ll start outputting 12v again but it doesn’t last long. As for charging capacity it doesn’t SEEM to have been affected. I do check that it is on 12v and not 9v so that is not the issue.

Does anyone know if there’s an easy fix, or is it time to replace? If so, does Anker have another battery of similar shape that also outputs 12v dc? The PowerHouse is no good for me, it’s too big.

Have you tried using the recorder with just the pack plugged in and no internal batteries?? That could cause it to not power off. Or, It could be that it’s beyond its age now and the internal batteries need to be replaced, if you are handy you can carefully replace them yourself. Otherwise it would be best to just replace it with a new unit.

Have you tried using the recorder with just the pack plugged in and no internal batteries

The recorder will not power on without internal AA’s. However in the past when my external batteries were newer, the connection to external was constant and reliable. The switch to internal happens when the recorder detects that the external supply dips a certain level below 12v. Thus, it thinks the external is out of juice and automatically switches to internal to maintain constant recording.

It could be that it’s beyond its age now and the internal batteries need to be replaced

The internal batteries consist of eight AA’s in series (1.5v*8 = 12v of course), and I always start each job with fresh.

Otherwise it would be best to just replace it with a new unit.

I assume you are referring to the external batteries, not the recorder.

Yes I was referring to the internal batteries of the battery pack. They could be beyond its age so replacing them would be a viable option

Oh, I see what you mean. I’ll open it up to take a look, thanks.

They are highly likely 18650 cells. 3350mAh 3.7V. 6 of them = 20000mAh.

You’ll need a tester meter to measure voltage of each. Chances are one is failed and so acting as a resistor. You can replace it with solder. It won’t be as neat but you can tape it up afterwards.

There are teardown videos online.

Recommend doing it outdoors in shade just in case.