I’ve been seeing a lot of talk on other forum posts about battery extenders, and the common consensus I see across all of them is that usually people are just buying a USB battery bank to keep their laptop going. This isn’t an unacceptable solution, but I personally would like something that’s a bit more purpose-built for Frameworks, specifically my 16” model or something that works on all 3 currently available sizes. All the posts I saw are from 2024 or before, so I figure I’d see if anything has changed since then. Does anything exist for this purpose, or are we still left with USB batteries as our only current option?
I’m actually kind of surprised that the Framework 16 doesn’t have an ‘extra battery’ expansion. I wonder if it’s for legal reasons around the maximum battery size allowed in airplanes.
No, you can have multiple 99.99Wh batteries with you for the laptop.
https://www.faa.gov/hazmat/packsafe/lithium-batteries
It’s risk avoidance. @nrp mentioned avoiding invention-related risk when talking about the Framework Desktop. The strategy would apply to all of their products, I assume.
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Nah, it’s fine. the limit is 100wh, but you can have multiple batteries on a flight. After all, the other companies released their own second batteries.
Would charging even work through the connector? Or is that where the problem lies?!
Not for legal but for technical reasons. How to connect the second, hot swappable battery into the circuit? In parallel? The voltage must be precisely matched before connection, so hot convenient or hot swappable. Use an additional DC-DC converter? Energy loss and additional bug, see how many CPUs stuck at 544MHz on FL16 with only one battery.
Just be aware that a number of airlines are getting antsy about taking power packs into aircraft cabins. If travelling make sure that you can take extra batteries with you - and that the return flight will also allow it.
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I would think the way to add a hot swappable battery would be for it to function similar to the current USB charging. Rather than adding the total capacity to the battery (two 85Wh batteries for 170Wh) use the hot swappable one to charge the internal battery and/or run the laptop and when it’s empty the FW16 goes back to running off of the internal battery (i.e. disconnecting the hot swappable one).
Now I have no idea how feasible that is to design but I would think it might be more energy efficient since there shouldn’t need to be any conversion between batteries.
Sure, that’s probably what I would be thinking too. It’s not the best because it would introduce a likely lossy conversion from whatever the battery voltage is to 48V (or whatever PD voltage would be decided upon) but my initial idea was something that would clip onto the bottom of the laptop under the back module, (This does mean the laptop sits at a higher angle, lets just call it more ergonomic lol) and you could plug it either into the back or a different USB-C on the side.
As for a hot swappable battery, I know how awesome that would be, and I do long for those day to return, these laptops weren’t designed with that in mind. It would be nice, but that sorta stuff comes from a day when laptop batteries could get you 60 minutes and only that before needing to be charged. Today the baseline for a “good” battery is set as something like 10 hours, and frankly I’m still used to only getting 2 hours due to highly degraded batteries. So as far as it goes, I’m actually quite happy with getting 5-7 hours out of my laptop, but that amount of time does still mean I usually need to charge it once while I’m out and about during my day. An extra battery would be really nice.
As replied by @Elliot_Gawlinski , the 16V → 48V → 20V conversion is too lossy. Even with synchronous rectification, the efficiency is still 90% * 90% = 81% and the heat generated is 240W * (1-0.81) = 45.6W, as high as the CPU’s TDP.
I would rather have an aftermarket DC barrel jack.
- The FL16 has a two stage DC-DC, one from 36V~48V to 20V(buck), the other from 20V to battery(NVDC, buck-boost). If 100W or lower is connected the first is not used but the performance is lowered.
- The latest version of FL16 supports 240W input from 1,2,3,4 USB-C expansion card and from the dGPU USB-C port.
We can infer that the interposer supports power transfer from the mainboard to that dGPU and from the dGPU board to the mainboard. Therefore, it’s technically possible to build an aftermarket circuit and a DC5525 port on the dGPU/Expansion bay that connects 20V directly to the VSYS rail on the mainboard. Then it’ll be easy to buy a 20V 12A(or more) power supply or simply use a bench power supply and adjust to 20V 12A if you have one.
My thought for battery to battery charging was that there wouldn’t need to be a conversion between different voltages, that’s assuming the batteries run at the same voltage.
Usually they don’t. I can’t speak in terms of the FW battery (although Charlie_6 says it’s 16V) most laptop batteries I see are rated at 7.4, 11.1, 14.8, usually any multiple of 3.7 due to the lithium cells that I’ve seen used. Side note the FW is probably 14.8V but 16V at a full charge if I guessed. Personally I’d be able to live with 81% efficiency, because it would probably keep my laptop going for at least a few hours more, which is all I really need, but if the heat is as much as the CPU that means it needs a heatsink like the one on the CPU which is already fairly bulky, and a fan which will be constantly running… that’s a bit much. I could deal with an unwieldy expansion on the bottom of the laptop, but having it hot and constantly making noise while I’m on the go (in my university classes) would be a complete dealbreaker, and probably not great for plenty other people too. Real unfortunate, but oh well. I do like what Charlie_6 says about the DC barrel jack, but if I understand the explanation behind how that would work, it seems like it would take a bit of doing and Framework wouldn’t probably make something like that. It’d be a DIY thing, which I’m not adverse to but I don’t have the engineering experience quite yet to make it work. For now, unless Framework puts a solution out (Hey, there’s an event coming soon, you never know) I’ll just stick with my battery bank.
Edit: The batteries WOULD be at the same voltage, but it’s definitely not that simple is what I meant to say.