I've been using my upgraded Inpiron 17R SE happily for a couple of years by now. I've even gone as far as buying an 128GB SSD to futureproof it. This is the only drive - besides the DVD drive - currently present in the laptop. However I've had an issue for quite a while:
Whenever I try to boot the Laptop only using the Battery (even fully charged) it Posts then loads Windows and turns of just before the Login-Screen (I can't see it). When I proceed to turn it back on, it Posts then beeps and says that there is a Real Time Clock Error and gives me the option to proceed booting or to enter Setup.
This however doesn't occur when using the Power-Brick. Moreover it isn't always the case. Sometimes the Laptop boots and works fine just using the battery, but then upon opening a Programm (while under battery-power) it shuts of and gives the same error message again. If it decides to work the battery still lasts for 2-2.5 hours.
I'm really confused to what the problem is. It could be a power delivery problem, but it's still the original battery and laptop with only the HDD changed to a SSD.
I'm aware of it being a rather old machine, but selling it is my only hope for getting a new laptop for college, but I can't sell it in this state.
I'm at a lost and really really sad because of this issue. I'm sorry for any typos or grammar mistakes, I'm a non native english speaker.
I am not sure on the main battery issue you're having as it could still be a battery related issue, but the Real Time Clock Error is related to the coin cell battery (also known as CMOS battery) on the motherboard. You can find the Service Manual for your system by entering your service tag at this link I would recommend replacing this battery first before moving on to looking at the laptop battery. Fortunately this could be a quick fix as these coin cell batteries typically cost only a few dollars or less. Obviously it could be a more serious issue than just replacing the CMOS battery, but having the clock error is typically related to the CMOS battery. I hope this helps out!