[Solved] Lenovo A7-10F Tablet - Does not start, does not respond to the charger

Hello,
I have a problem with a Lenovo tablet. Discharged overnight, in the morning after connecting to the charger did not react at all, neither the display nor the charging diode. I tried a long charge (3 days) to no avail. I thought the full discharge protection did not work and the battery fell off. I ordered an identical one from the broken model, but the tablet did not react to it either.
I checked both with a multimeter, the measurement of the old battery showed 3.68 V, while the measurement of the new one was 0.01. Apparently, this was due to the fact that the B6 charger was charged and discharged to check the capacity.
Is it possible for a functioning battery to be discharged to such a level? Should the measurement, even when the battery is not charged, oscillate around the first value?
I tried to charge it but I can't say for sure if the charging system in the tablet works, so I can't prove that the battery is the fault, not the device. I don't have any other device on which I could check it. I don't want to invest in a motherboard if it would prove to be a guilty battery.

Hello.

barabash22 wrote:

I checked both with a multimeter, the measurement of the old battery showed 3.68 V

The device is too low for operation.

barabash22 wrote:

while the measurement of the new one was 0.01

The battery should not be discharged to 0 V - this negatively affects its life.
Charge both batteries off the tablet to a voltage of just over 4 V (the maximum voltage for the battery from the photo is 4.35 V) and then on such a charged battery try to start the tablet.
Are the tablet socket and the charger plug working properly?
greetings

Dydelmax wrote:

Charge both batteries except the tablet to just over 4 V

I just don't have how. I do not have an external charger, and from what I read, a simple voltage supply from an external power supply (if I could arrange it) can cause a battery explosion.

Dydelmax wrote:

Are the tablet socket and the charger plug working properly?

I don't know that. There are certainly no mechanical damages, and any problems with the motherboard and charging system were to be determined after eliminating the most likely battery. For the first time I met with sending a completely discharged battery, which put my whole plan.

Without a Li-po charger, I suggest you don't try to charge. We service it with a workshop power supply, but we keep an eye on the mileage. The link dropped to zero is unlikely to be raised anymore, in any case I do not remember such a case. I suggest advertising it. I don't remember what voltage the cell has in this tablet, but it seems to me that nominally 3.8V - if charging does not start at 3.7, something is wrong. After connecting the power supply does the voltage appear on the board?

zjo wrote:

After connecting the power supply does the voltage appear on the board?

The meter stayed at work, so I won't be able to check until Monday. Do I understand correctly to check it on the battery connecting pins when the charger is turned on? Or elsewhere?

If I remember correctly, you have control fields with the USB connector on the A7 - check the voltage at the extreme. If 5V appears after connecting the power supply - the problem is with the charging circuit or the battery itself. If it does not appear - with the power supply, socket, or charging circuit (short circuit).

A layman's question, but is it about these two fields?

Advertise batteries where you bought them and replace them with new ones. If you want, you can try to "resuscitate" it by connecting to a regulated power supply and set the voltage to 4V.

The seller claims that the battery is good, just charge it. Without the certainty that the fault is not on the tablet side, I can not prove otherwise.

The batteries can be charged in the tablet only when it has its nominal voltage (3.8V). Below 3.8V, you will not charge the tablet battery with only an external charger or service adapter.
Since the battery is 0.01V, it is not good. she probably lay in the warehouse for a long time and unloaded.
Give this information to the seller and don't tell him that the battery is good.

The battery went to the complaint. Thank you all for your help.