While all this talk of battery and electronics is great,
My apologies if we seem to have usurped your original question, but that's the nature of forums. The moderators will keep us in check if we stray too far away from the subject.
explain why in a mature manner like Harlow?
Cheers. I try to be fair. I've fallen into the trap of imprecise language on many occasions and had my "comeuppance".
Anyway, to add and illustrate, if you take a single, standard
AA battery, that is indeed a "battery". A (as in one) 1.5V battery.
I'm old school (and people call me pedantic) for using terminology learned when studing for a degree in electrical engineering and electronics. I was taught that a cell is a single unit and a battery is a group of cells.
https://circuitglobe.com/difference-between-cell-and-battery.html
However, many (if not most) definitions on the internet define a battery as both single and a multiple unit, which is not what I was taught. When talking with friends and family, I use the term battery loosely and speak of AA batteries and watch batteries. If I were to call them cells, I'd get puzzled stares or objects thrown at me. But when I'm discussing power systems with other engineers, I use the term cell to describe a single unit. Hence, in engineering parlace, I'd describe a PP3 and PP9 as 9V batteries, but AA and AAA as 1.5V cells. It's being needlessly nit picking, but we all have our foibles.
while the battery may be designed for 19V
Sorry, but again I think this should read "while the
laptop may be designed for 19V", substituting 'laptop' for 'battery' in your sentence. Saying "the battery may be designed for 19V" makes it appear the battery is built up of cells to give a
terminal voltage of 19V. As already described above, laptops incorporate 'buck converters' to generate all the various different voltage rails needed inside, including the charger supply. The backlight behind the display in the lid might require a 'boost converter' to generate a high voltage for the backlight. In some cases this is over 100V and capable of giving the unwary a shock. Thus you will have several voltage rails below 19V and possibly one above 19V, all generated from a single 19V input.
I pretty sure you know a laptop battery can have a significantly different terminal voltage to that of the power brick, but not all readers may be able to infer this subtle nuance, when talking about "19V". I thought it worth mentioning to save disappointment and confusion, if anyone goes out looking for a "19V laptop battery" on eBay or Amazon .
If your laptop came with a 100W supply, I would be very leery, and advise against the use of a 65W supply. 35% less capacity is a lot. Running just the laptop "may" be okay, but I would make sure the battery has been removed first. If lucky, at worse the laptop would just crash and recover fully upon booting with a suitable supply. But if unlucky a crash could result in file corruption, or perhaps worse. I would also pay close attention to the temperature of the power block to make sure it has lots of ventilation to avoid it getting too hot.
OK. I've run a few tests this morning on my Lenovo laptop with a USB-C meter connected in series with the "wrong" 65W USB-C power brick from the Huawai laptop.
The laptop is idling (no big programs running) and the USC-C meter shows 19.22V (nominal 20V USB-C under load) at 3.05A and 59W in. Note this is 6W less than the nominal 65W rating of the Huawei PSU. Passmark's batmon program shows a varying charge rate between 10W and 48W, depending on CPU activity. When the CPU demands more power, the restrictive output from the 65W supply means less power is routed to the battery charger. Hence the charging rate goes up and down. Not perfect. It will take longer to charge the battery, but the laptop still works.
Switching over to the correct 100W USB-C power brick supplied by Lenovo gives 19.90V on the USB-C meter (much closer to the nominal 20V USB-C specified output), at 3.3A and 65W in. Passmark batmon shows the battery is now charging at a constant 53W. The additional 35% headroom from 65W up to 100W allows both the CPU and the battery charger to work at optimal levels, as opposed to variable charging levels when using the restrictive 65W supply.
As a final test, with the 100W USB-C PSU connected, I started the Aida64 stress test. The USB-C meter shows 19.72V , 4.70A at 93W. Interestingly, batmon shows the battery charge rate has dropped from 53W to 5W. A red warning showed up in Aida64 saying the CPU was overheating so I ended the stress test after 60 seconds. Obviously the 100W power brick cannot supply the CPU running flat out and charge the battery. Conclusion. The design engineers have done their job. Power is diverted from charging the battery and routed to the CPU when necessary,
with both the 65W and the 100W chargers.
I don't envisage any laptop crashes when running from a 65W brick, especially when with lightweight tasks and no silly benchmark stress tests. Unlike a desktop system starved of power by an inadequate ATX PSU, a laptop can usually fall back on the battery when the mains brick fails to provide enough power. When the battery gets low, Windows (etc) normally executes a shut down to avoid a crash. N.B. As with many modern laptops, my laptop's battery is buried inside and cannot be unplugged easily, unlike some older laptops.
In hope this reassures you I'm not totally mad running my laptop on an "under-rated" power brick. Engineers like myself are renowned for experimenting. It's part of our job. That's why I tested specific equipment at ambient temperatures down to -51°C (-60°F) and up to +60°C (+140°F), performed shock & vibration checks, EMC emissions and immunity + electrical safety compliance, etc. As with many complex systems, both electrical and mechanical, there's a (designed in) margin between safe operating levels and a smoking ruin. I apply this knowledge and work experience to computing. Sometimes I get it wrong. Most times it's OK.
Each battery cell is usually charged individually up to around 4.2v, not in series as a lump sum.
Interesting. Thanks for the clarification.
In the past, I remember finding 18650 cells in laptop batteries with unequal terminal voltages. Some cells were "normal", others were "low". Some even displayed a small reverse voltage.
At the time, I assumed batteries were charged as a single entity and not on an individual (per cell) basis. However, given the multiple contacts on many removeable laptop battery packs, I suspect even 15 to 20 years ago, they were charging each cell separately.
