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This paper measured a cell, they reported a max of 0.5% expansion over a charge cycle: Source: Expansion of Lithium Ion Pouch Cell Batteries: Observations from Neutron Imaging Figure 7 Over the lifetime of the battery, it swelled more than 1.5% Source: Expansion of Lithium Ion Pouch Cell Batteries: Observations from Neutron Imaging Figure 9 One could ...


9

Some PSU's have physically disconnectable outputs (i.e. a relay on the output) and/or some other kind of over voltage detection/protection when on. OVP is usually a marketed feature, but doesn't necessarily mean it will work when the PSU has no power at all. Physically disconnectable outputs is not a feature I've typically found advertised. Regardless of ...


8

Yes, most smartphones have a single cell battery. Most of the components on the smartphone mother board are low powered and run on voltages lower than the typical 3.7V provided by a single lithium ion cell. Hence a series combination of multiple cells is not worth it at all. Having a parallel combination of cells is also not useful because of the ...


6

This is quite the multipart and deep question. You seem to understand the basics but just in case, I’ll recommend this website as a good overview, albeit dated in terms of current ICs and BMS competitors. http://liionbms.com/php/index.php Chips This is dependent on application. For small packs like the one you’ve drawn, there are a wide variety of chips ...


5

Why is the MOSFET source connected to load and drain to battery? As shown in the schematic, the MOSFET has a body diode connected from drain to source. If the MOSFET were attached the other way around, USB power could flow through D1 and the body diode into the battery, charging it faster than is safe. (Note that when is MOSFET is on, it allows current to ...


4

Both types of construction have similar characteristics in terms of degradation, charging behavior, and susceptibility to deep discharge problems, but: Li-Polymer have a slightly higher energy density because of the way in which the separator (salt bridge) is made. This comes at a 10-30% increase in cost, however. It's possible to make flexible batteries ...


4

Just substituting a supercap for a LIon is not going to be good. A LIon dies if the voltage exceeds 4.2v, the charger will limit to handle this. A supercap dies if the voltage exceeds 2.7v. Oops! Two series supercaps, with DC balancing resistors to protect each against overvoltage, might work OK, but with the charger stopping at a max voltage of 4.2v ...


4

Your "mobile charger" is actually just a 5.2V Constant Voltage power supply, which is unsuitable for directly charging batteries, so no. Doing so might result in fires/explosions. The battery "charger" of mobile devices is actually inside the cellphone/tablet, not on the USB power supply.


3

I've been doing LOTS of research on this for the past several hours on Google. Here is what I've found: Lithium METAL cells (coin cells like the common CR-2032 and possibly other Li-primary batteries, but I'm not as sure) truly have uncombined lithium metal in them. Li is the lightest of the alkali metals (along with Na/sodium, K/potassium, Ru/rubidium, ...


3

I think a better way would be to isolate the fire, but there isn't much lithium in batteries. Simple Guidelines for Using Lithium-ion Batteries Lithium-ion batteries contain little lithium metal and in case of a fire they can be dowsed with water. Only lithium-metal batteries require a Class D fire extinguisher. Lithium polymer batteries shouldn't ...


3

I was hoping to be able to uniformly shift the voltage below 3V using diodes or a voltage divider but from a couple google searches it looks like current fluctuations would make that impossible. That sounds like BS, do you have a source on that? A simple resistive voltage divider can be used to linearly scale down the voltage: simulate this circuit &...


3

I have randomly purchased several of these relatively cheap lithium ion batteries from ebay, originating from China. I have a fairly high quality battery charger/analyzer that I use to test these batteries. They have all been the advertised voltage, but he capacity is nowhere near what they claim. A 5000 mAh battery tested at 333maH. Another 5000 mAh (...


3

[first things first: read the MCP73831 datasheet, of you haven't done so already] This is a fairly simple charge controller. The load (SYS_OUT, aka SYSTEM_LOAD) is wired directly to the battery, so it draws current from both the battery and charger. "Couldn't this ruin things?" That alone shouldn't ruin things. The charger is current-limited. Of course,...


3

I don't see an overly-compelling reason to boost up the voltage to 5V. Unless you're doing some intense time-critical math heavy calculations, I doubt 16MHz will buy you any advantage over 8MHz for the application you're describing. Single-purpose hardware can get a lot done at 8MHz. A 3.3V linear regulator with a dropout voltage of 0.3V or less should give ...


3

Four cells will put you over the nominal voltage of a single Li-Ion cell and it might be OK considering they will use a switch-down converter. However that is not guaranteed, it may damage the phone, it may have over-voltage protection that will prevent it starting up or worst case may have some form of clamps that will damage your batteries and/or cause a ...


3

You are thinking of the power pin in a digital manner. The power pin is not set to be an input or an output. It is just the positive terminal of the power rail. If you want to power the trinket using a 5V power source, you'll put it in there since its the positive terminal. If you want to power another device that uses 5V and it just so happens that the ...


3

Q: What is the reason Lithium Polymer batteries are limited to 1C charging? A: They're not, at least not fundamentally. You can get 5C and 10C charging batteries from e.g. A123 systems. The reason batteries are limited on paper to relatively slow charging rates is to avoid internal hot spots, caused by a chemical-physical phenomenon that causes lithium ...


3

I am also using this load sharing circuit and it works for me. You say that the diode is heating while the battery is charged. This means you have 5V at the input and the Mosfet is closed. To help you we need some more information voltage drop across Diode voltage drop across the transistor If you have 5V at the input you should have a voltage drop about 0....


3

Q2 is a mosfet used to disable power draw from VBAT when 5V or VUSB is present. Disconnect the trace from pin 3, and place a switch between pin 3 and the trace from VBAT. Based on what I see on the schematic. This means it can still charge from 5V. But will only power the 3.3v regulator when the switch is on. Edit: based on https://macsbug.wordpress.com/...


3

You're limiting yourself with the choice of components. A tablet manufacturer would probably not choose the display you're using. 12 V 1.5 A is 18 Watts of power so this is a very power hungry display. A tablet display should use LEDs for the backlight (perhaps yours uses CCFL tubes) and use only a couple of Watts. LEDs used in displays need about 3 to 4 ...


3

Depends on the current draw of the laptop. See the graph below with varying SoC (State of Charge) values. If you draw lots of current, then lifetime is reduced. However, total energy units may actually be higher. Case 1: 75–65% SoC offers longest cycle life but delivers only 90,000 energy units (EU). Utilizes 10% of battery. Case 2: 75–25% SoC has 3,...


3

Li-ion batteries usually follows the naming convention according to size, so for example an 18650 battery is 18 mm in diameter and 65 mm in length. 0 denotes cylindrical form. In the past, a tailing 5 wound indicate a prismatic cell but yours doesn't. Anyhow, my best educated guess is that 35 denotes the length, 08 the width and 3 the thickness and all ...


2

You can do this with a relay but its contacts have to be rated to carry the current that it may be switching. You haven't mentioned this but there are plenty of relays that can switch 10 amps at much higher voltages than 60 V dc. What you may not have is a control voltage to activate the relay coil. Most typical relays will have variants that cover 5 volt ...


2

LiPo's are usually rated by a discharge value "C". This is capacity multiplied by the C value. For example, a 11.1V 5C 1000mAh battery: 5 x 1000mAh = 5000mA or 5A discharge You should be able to draw at-least 1C safely from most lithium batteries. Check the eBay listing again to see if they include a C value, it might be there. I always try to order ...


2

Short answer: Yes. Before giving the long answer, think about how fast-charging a lead-acid battery works. Applying a lot of current raises its voltage; however, the negative plates are not able to react with the sulfuric acid quickly enough, and so the excess voltage is not helping it charge faster. On the other hand, the high voltage does damage the ...


2

In section 3 of the datasheet, it states that the device supports charge currents of up to 10A. The controller needs external support circuitry to do this, see the typical system diagram (from page27 of the datasheet): The current is set by external components for the constant current phase, as is the cut-off current level when in constant voltage mode. On ...


2

Here is the answer as in the datasheet page no:3


2

The LDO regulator has an inhibit input so use a small voltage comparator looking at the Li-ion battery terminal voltage and when it drops to a certain low level, have the comparator switch so that the LDO Reg turns off via the inhibit input. It's called UVLO (under-voltage lock-out) by quite a few chip suppliers. You might be able to use that inhibit input ...


2

The 100/500mA maximum that the MCP73831 will provide can be used by the battery, or the load, or both sharing it, which means @ the 500mA setting & if your load is operating at its maximum ~300mA, there'll only be ~200mA available to charge your battery, so it'll take longer to charge. This arrangement is only appropriate to power electronics that can ...


2

2 1.8Ahr cells in parallel is the same as 1 3.6Ahr. Its called a 1s2p cell. Sometime LiIon chargers stop charging after a fixed time. Something like the capacitry / charge rate * 1.5. So you might not end up with a fully charged pack after a single recharge. Using a single cell LiIon batteries in parallel (with the same specifications and age) is ...


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