That would depend on how the batteries are connected to each other. If they’re connected in parallel, the total amperage will increase, but not the voltage. Charging might require more amps at that point, though, which could be a problem.
Yeah, but I wouldn’t want to directly connect them in parallel as they have a nasty habit of unequally sharing, and the talk was of ‘stacking’ them on top of each other, suggesting the two cells would be in series, thereby doubling the voltage.
Nothing about the word stacking implies connecting in series. Or in parrallel. These are individually insulated cells with solder legs welded on. Not stacked bare cells like in a flashlight. Multi-cell packs of all chemistries are routinely spot-welded in whatever combination of parallel & serial the application requires. 2, 3, or 4 cells directly hard-wired in parrallel, or series if you wanted the voltage to add up, are perfectly fine. You just can’t mix chemistries or capacities or ages. Individual cell management is only needed in high current or especially “dynamic” chemistries like lipo. These only require a particular voltage and current for charging, a pretty narrow range but otherwise no especially exotic management. The motherboard is producing the correct voltage, and the current will be less than the battery could tolerate, making the full charge time take longer and making it merely easier on the cells.
One possible problem is the parallel cells could possibly try to draw more current from the source, if the source were not current-controlled, but it is so there is no chance of drawing any more current even if there were a dead short wire in place of a battery. There is no danger of hurting the charging circuit, but there is a possibility that the charging IC senses the less-resistive load and treats it as some kind of short in the battery and decides it better stop providing power. So maybe it fails to charge simply because the charging circuit says “something funny here, I’m going to be safe and shut down”. In that case I just remove the extra cell, or add a resistor.
Yes, in this case, obviously the connection is parallel. Also the + goes to the + and the - goes to the -, and all the bits are insulated with kapton or other insulator instead of allowed to short all over the place.
Yes, at some point one of the cells will be the first to start behaving a little different from the rest enough to make the whole pack no longer viable. That day is no sooner than with a single cell.
In other words, this is not an issue.
Yes, that’s true, I didn’t consider that. Connecting them in parallel would require a more complex setup than stacking them in series.
No it’s not complex. It’s not like the main battery that needs each individual pouch individually monitored, nor like a car or house or even a power tool with high current and heat etc. You just solder the pins together.
Quite the opposite, for most battery chemistries parallel is significantly easier than series
Wandered off the original topic about the main battery, but just to wrap up the talk about the cmos battery, I did end up getting 2 ML2020’s from digikey and soldered them right to the terminals on the battery holder with wire-wrap wire.
It went fine, easy to do. Seems to be working fine and I see no reason to worry electrically.
So the end effect will be that these cells are getting charged a slower rate than a single one would have, and less current doesn’t hurt anything. (the battery manager ic or circuit will be limiting current since that’s 90% of the definition of it’s job, so a single larger cell will take longer to charge to full than a single smaller cell, and 2 larger cells will take even longer, but it doesn’t change how much charge you get in say an hour. Say on the original single small cell you get a week of standby time from 2 hours of charging time (I don’t know the actual number, just use this as example), the much larger cell will take longer to get full, but you will still get the same standby hours per charge hour, just you will get more total of both. So the board should be able to sleep with no power a lot longer.
I got cells with solder legs and soldered them together in parallel, seperated by 2 layers of kapton tape and bundled together by kapton tape.
In the CoolerMaster case (not the laptop!) there is a ton of space to the right of the ML1220 holder. You could actually fit at least 4 cells, maybe even 6 in 2 stacks of 2 or 3, but the aera further to the right is a bit shallower and also that area gets warm, while the space directly next to the normal holder has more room and doesn’t get warm, so it’s a better place to put cells, and even a single ML2020 is a big increase over a ML1220.
If you do this, remember, the chemistry is critical, you must use MLxxxx not anything else.
The exact cells I used are: https://www.digikey.com/en/products/detail/panasonic-bsg/ML-2020-V1AN/431504
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@Brian_White
Just out of curiosity, why do you need a larger RTC battery?
How long do you need the RTC clock to last while the laptop is switched off?
The original battery is undersized. Any motherboard should be able to hold cmos settings for 5 to 10 years without power.
The original Framework dies in as little as a week.
Even with power, the original battery dies and stops taking working at all after just 2-3 years, as we have all now started to discover the hard way.
Mine died and would lose it’s settings instantly when turned off, and no amount of charging time worked. The cell no longer took a charge. This is especially annoying when the motherboard is not in a laptop any more and no longer hooked up to the default video and keyboard. I need it to retain it’s settings.
There is no specific time that it must last without power, but a week or even a month is too little. There is no excuse for it not to last at least 5 years. That is not some entitled demand, that is the norm since the 80’s.
The problem is a combination of 3 things: using a rechargeable battery instead of non-rechargeable, using such a small one, and the motherbaord draws too much current while asleep.
We can’t do anything about the motherboard drawing too much current, and putting in the right kind of battery (a CR2032, which in this case would also require adding a diode to prevent charging) will still drain too fast because of the motherboard as well as the voltage drop across the diode.
The easiest thing we can do is just keep buying new ML1220’s every couple of years and keep the machine plugged in at all times so it never goes a month without power.
The next easiest thing is just install a larger capacity of the same type of battery that the charging circuit is designed for. (which is what I just did.)
https://community.frame.work/t/laptop-wont-power-on-unless-i-plug-in-ac-power/
https://community.frame.work/t/viability-of-an-ml-1220-rechargable-battery-for-rtc-cmos-11th-gen/
Framework themselves proposed this fix which I think is a bit ridiculous as a solution, but shows that they recognize it’s a problem, something they did wrong and need to come up with some kind of fix for:
https://community.frame.work/t/rework-instructions-for-11th-gen-mainboards-to-enable-powering-the-rtc-circuit-from-the-main-battery/
I see now. The RTC circuit is just badly/wrongly designed.
I have seen other computers keep their RTC settings for 4 hours without a battery at all, and with the ML1220 battery it lasts months(no one has measured the time).
As a comparison, ARM pc’s work just fine without using RTC or storing anything in CMOS. It’s just X86 PCs and their overly complex BIOS that need it. All the settings in X86 BIOS could have been stored as config in the OS, skipping the need for any bios screens at all.
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The bios settings control things that can’t be managed by the os, they are hardware settings that need to be in effect when there is no OS.
You can’t store hardware settings in the os when the settings determine how to even find the os, what video device to use, whether to insist on a password, etc.
Some platforms do this with flash or eeprom instead of battery-backed sram, but a pc needs to maintain a running clock anyway, and it’s handy to have a guaranteed way to erase all settings to factory default to clear any error by just removing power rather than requiring some more complicated and error prone active process to rewrite eeprom or flash.
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Did the battery spend most of its time at 100% full, or did you use BIOS settings to keep it at, for example, 70%, or was it regularly cycled fairly deeply by often using the laptop for a significant time without AC power?