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February 3rd, 2025 00:20
Latitude 7420 2-in-1 replacement battery
Hi, I am looking at getting replacement batteries for a couple of Latitude 7420 2-in-1 laptops that have failing batteries. They shipped with the 42Wh (11.4v 3cell) batteries. Can I straight swap in the 63Wh (15.2v 4cell) battery as a direct replacement (with longer battery life)? Those two replacements are about the same price when bought third-party. However, they have stern warnings on those sites saying make sure you buy the right one as the two batteries are not compatible with each other! I am assuming the warning is just alerting that the batteries are different voltages and hence very different from each other... but that it is fine to ignore that warning because the laptop seamlessly works with both voltage batteries anyway. Is that right?
emardee
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March 2nd, 2025 23:14
Thanks for the concern. I double checked everything and decided to take a risk. Fortunately, I can confirm that on our 7420 2-in-1 laptops here, that we were able to upgrade from the lower capacity 42Wh battery (part: 9JM71) to the higher capacity 63Wh battery (7FMXV) just fine. Both batteries are identical dimensions (the lower capacity battery has a plastic spacer where the 4th cell would be), and the same thickness, so they take up the same room in the laptop chassis. There was no issue with the voltage difference either, they just worked!
Note: My replacements came with the battery lead supplied, whereas many come without the lead. I am presuming the leads are identical though, so higher capacity battery would presumably still work with the lower capacity battery's lead.
ejn63
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February 3rd, 2025 01:02
The two batteries are different in physical size -- the 63 Whr battery is larger and on most of the newer systems, won't fit the palmrest assembly that ships in systems with smaller batteries. Unless you're willing to physically modify (say with a grinding tool) the palmrest, or are willing to replace the palmrest assembly, you cannot install the larger battery.
emardee
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February 3rd, 2025 02:14
Thanks for the info. So the motherboard should work fine with either voltage... but it is just the physical size that limits the larger battery?
Interestingly, on this site ( https://www.nzbattery.co.nz/dell-nz/battery-dell-latitude-7420.htm ), it shows the two batteries as being identical size and fittings... and it looks like the 3 cell battery just has a spacer piece on the left where the 4th cell is on the larger capacity battery. So I might be lucky for this model.
I guess I can open one of the laptops up, and check if my current battery also has that spacer in the 4th Cell spot... and also that the base-unit has full depth space there for the 4th cell. Presumably if so, there is a reasonable chance it will fit and work.
(edited)
ejn63
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February 3rd, 2025 02:19
Also check the palmrest assembly -- it may not have the accommodation for the fourth battery cell. That is the case with multiple newer models. Unfortunately, replacing the palmrest is very labor intensive (the entire system has to come apart to do the job, as just about everything in the system is mounted to the palmrest assembly.