iRobot Roomba 780 Incorrectly Identifying Charged Battery as Low - Possible U2/U4 Issue?

Hello,

I have iRobot Roomba 780.
Description of the problem - the robot correctly charges the battery, up to 19-20V.
Unfortunately, after inserting the battery, it passes 5 seconds and informs you about the low battery.

I discharged the battery manually to a voltage of 10V and after recharging it recharged to 19-20V. Unfortunately, the problem repeated itself.
It behaves the same when charging from the docking station as well as the outlet. This indicates a malfunction of the battery verification mechanism.

Has anyone met this yet? In older diamonds it was a typical U2 and U4 problem, here the motherboard is completely different.

Hello,

evilsnail wrote:

the robot correctly charges the battery, up to 19-20V.

If the mechanism (system) verifying the battery level were damaged, it would not charge at all.
These symptoms clearly say about the wear (failure) of the Battery.
The battery has lost its original capacity and the moment reaches the charging voltage through which information about the fully charged battery is transmitted.

zumik998 wrote:

Hello,

evilsnail wrote:

the robot correctly charges the battery, up to 19-20V.

If the mechanism (system) verifying the battery level were damaged, it would not charge at all.
These symptoms clearly say about the wear (failure) of the Battery.
The battery has lost its original capacity and the moment reaches the charging voltage through which information about the fully charged battery is transmitted.

Thank you for the information. I thought that in this robot it could be two different systems, or the system could be damaged in such a way that it simply transmits the charging voltage all the time regardless of the battery level.

I verified the battery by connecting a 1.5A load under it.
The battery maintains 12.6V in this case. The battery is described as 14.4V. In that case, does such a voltage drop under such load suggest battery wear?

Best regards and thank you for your reply.

These charging systems usually break down so that you connect to the charging and it immediately says that it is charged, not charging for a moment - this was the case in not one drill / screwdriver

You know what, voltage drop under load depends on the value of the internal resistance of the battery.
Give me the capacity of this battery from this robot, this information is next to the voltage and is expressed in [mAh]
What device do you supply with this Battery through which 1.5A current flows?

Quote:

These charging systems usually break down so that you connect to the charging and it immediately says that it is charged, not charging for a moment - this was the case in not one drill / screwdriver

Good to know

Quote:

You know what, voltage drop under load depends on the value of the internal resistance of the battery.
Give me the capacity of this battery from this robot, this information is next to the voltage and is expressed in [mAh]
What device do you supply with this Battery through which 1.5A current flows?

A few meters of LEDs at 12V.
14.4V 3000mAh NI MH battery

I will tell you so 1.5 A is 1500mAh, so when fully charged, this LED pack should shine for approximately 2 hours. Plug in and see if the battery can be barely lit after 30 minutes

I had a similar problem recently with the quite old 620. After fully charged, it drove five minutes and was tired and the voltage was perfect. After replacing the battery, the roomba is nice and I haven't managed to unload it so that it stands in the middle of the room.

Quote:

I will tell you so 1.5 A is 1500mAh, so when fully charged, this LED pack should shine for approximately 2 hours. Plug in and see if the battery can be barely lit after 30 minutes

The results of the discharge test of 3000mAh 14.4V batteries with 12V LEDs.
After connecting to a charged battery:
- 12.6V, current 1.5A

After 1h 10m voltage on 10V LEDs
After 2h 20m the voltage on LEDs 9.3V and still shine ...

What to think about it?
Sure, the battery is a little worn out and I can replace it. Only should a battery with this degree of wear behave so binary? So once it rode, and now after connecting it goes 50cm?

I do not insist - the only thing I do not want to buy a battery is in vain
Added after 1 [minutes]:

Quote:

I had a similar problem recently with the quite old 620. After fully charged, it drove five minutes and was tired and the voltage was perfect. After replacing the battery, the roomba is nice and I haven't managed to unload it so that it stands in the middle of the room.

Thanks for the feedback - as it was before. Have you seen the gradual discharge? Rode less and less? E.g. first 15, then 10 minutes, then 5? Because for me it got quite binary. He drove long times and suddenly, after charging, he does not drive for 5 minutes, but 5 seconds

evilsnail wrote:

Thanks for the feedback - as it was before. Have you seen the gradual discharge? Rode less and less? E.g. first 15, then 10 minutes, then 5? Because for me it got quite binary. He drove long times and suddenly, after charging, he does not drive for 5 minutes, but 5 seconds

Virtually every day, we noticed a strong loss of desire to work. Earlier he flew around the whole apartment (55 sq m) and returned to the dock in red, but he managed. One day he made half the room and stood in the middle. I even charged it with a cable and the same thing continued. It puzzled me to such an extent that I stripped it to the last screw and did a general review. However, replacing the AKU with a new one made Roomba fly better than after the purchase
PS.
AKU (replacement) I bought on aledrogo, the user advertised with Polish links.

This test came out average, I'll tell you honestly. But there is also such a thing that you probably have between the cells and the robot such a system that counts recharges just like in a laptop, and when the quantity is full, he gives info to the robot that he is used battery. However, I am not sure if there is such a system in this model. But I think a battery replacement should solve your problem

Added after 3 [minutes]:

Of course, let us know about the effects of your actions on Elka

Quote:

Virtually every day, we noticed a strong loss of desire to work. Earlier he flew around the whole apartment (55 sq m) and returned to the dock in red, but he managed. One day he made half the room and stood in the middle. I even charged it with a cable and the same thing continued. It puzzled me to such an extent that I stripped it to the last screw and did a general review. However, replacing the AKU with a new one made Roomba fly better than after the purchase
PS.
AKU (replacement) I bought on aledrogo, the user advertised with Polish links.

Quote:

This test came out average, I'll tell you honestly. But there is also such a thing that you probably have between the cells and the robot such a system that counts recharges just like in a laptop, and when the quantity is full, he gives info to the robot that he is used battery. However, I am not sure if there is such a system in this model. But I think a battery replacement should solve your problem

Quote:

Thanks - replace the battery according to the advice and let me know what the effect was.
I immediately warn you that unfortunately I won't be able to order the battery in a week, so no response does not mean an abandoned topic

I was in your place immediately advertised equipment, because it is known that sometimes there will be some damaged models, even good products. Fortunately, my Mamibot doesn't have such problems. It charges it twice a week and it's enough to vacuum the entire house every day throughout the week.

HubertF2 wrote:

I was in your place immediately advertised equipment, because it is known that sometimes there will be some damaged models, even good products. Fortunately, my Mamibot doesn't have such problems. It charges it twice a week and it's enough to vacuum the entire house every day throughout the week.

Unfortunately, the copy is already a few years old.

I ordered the battery - testing on Monday

My equal lasted five years.

evilsnail wrote:

HubertF2 wrote:

I was in your place immediately advertised equipment, because it is known that sometimes there will be some damaged models, even good products. Fortunately, my Mamibot doesn't have such problems. It charges it twice a week and it's enough to vacuum the entire house every day throughout the week.

Unfortunately, the copy is already a few years old.

I ordered the battery - testing on Monday

Hello everyone.
It was a battery issue - it works like a new one after replacement.
The high voltage read from the battery was due to the fact that my meter (quite good, not trash for PLN 10 from the supermarket) had such a discharged battery that the spoke said voltage readings, overstated by about 20%.

Thank you all for your help