# Tag Info

91

According to the German Duracell website: As you press the points, a current will flow through a metal strip getting warm. The display is a thermochromatic one. So the increased temperature will result in a change of color from black to yellow or red in your case. The strip has to be designed in a way so that the heating of the single elements corresponds ...

26

Can I charge as fast as I want, provided that I cool down sufficiently? No. To charge faster you need higher voltage to overcome internal resistance. If the voltage is too high it may cause damage due to electrolysis or other effects, depending on the battery chemistry. A lead-acid battery will 'gas' when the voltage reaches ~2.45V per cell, as the water ...

22

You certainly cannot charge as fast as you want, but you can indeed increase the charging rate if you keep cooling the battery in the process. Though the point is not to make the battery colder than normal, rather, you want to prevent it from getting hotter. For example, check out this teardown of Tesla battery pack, revealing the cooling system which is ...

15

As well as demonstrating some basic electricity generation you will be demonstrating why we don't generate commercial electricity using NZ coinage and vinegar! simulate this circuit – Schematic created using CircuitLab Figure 1. Every battery has an internal resistance which causes a voltage drop as current increases. The effect of internal ...

15

If you connect the 39 + 3 batteries to a load and that load is connected for a longish time you might find that the higher ampere-hour batteries are still running OK and trying to push current to the load but, the lower ampere-hour batteries are forced below their recommended lowest terminal voltage. In short, you might damage the lower ampere-hour batteries:...

12

A lot of the chemical limitations to which speeds you can charge or discharge a battery actually get worse with decreasing temperature. For example: the charge carrier mobility in a cold battery will be lower than in a warm one. That leads to a higher internal resistance. So you can't charge or discharge as fast, because the charges simply don't move as ...

11

When any battery is connected to a load its output voltage will drop a bit due to the internal resistance of the battery. If you are constructing a battery then there are four simple things you can do to reduce the internal resistance of the battery: Make the electrodes wider. The resistance of the electrolyte is going to be inversely proportional to the ...

11

Self-discharge of a 9V alkaline with a 20% down shelf life of 5 years and 500mAh capacity is about 2uA, so I don't think that <2uA is any kind of a possible problem. There is no net charging taking place. On the other hand, Schottky diodes can have very high leakage at high ambient temperature. The self discharge current will also go up with temperature ...

8

If you charge too fast, then because the heat transfer is not instantaneous the plates buckle due to thermal expansion and create localised « shorts » which can then cause catastrophic failure. And yes, been there seen it done : hi rate charger set to 24v on a 12v battery : By someone a few slices short of a loaf...

7

The Duralock battery has improved alkaline cells (improved purity of actual chemical ingredients) not only this but the Duralock battery protects the anode and cathode with separators that limit power transfer when the battery is not in use. On top of this, it has a sort of triple corrosion protection that surrounds the contents in an acid resistant, anti-...

7

Yes, Lithium-ion bateries degrades over time, even if unused. It is due to a chemical/physical reaction that starts right after manufacturing of the cells. I can't answer on the state of your batteries. Because it highly depends on the storage temperature and also the charging level of the cells during the storage. I don't remember the optimal number, and ...

7

Li-ion is primarily chosen for higher energy density (by weight and volume), but also for higher power, higher voltage, more flexible form factor, cheaper and easier manufacture, more efficient charging, lower self-discharge, more cycles and higher reliability than most other battery types. Why don’t electronics companies try a different type of battery, ...

6

I think this is due to how you are measuring the current. Your results all make sense if the resistance of your current meter is higher than the internal resistance of the battery at the measured current. Think of the limiting case where the batteries are pure voltage source (no resistance) and you put a fixed resistance accross them (your current meter in ...

6

Batteries store chemical energy. The two different metals and the electrolyte react in such a way that electrons will flow through an external circuit from the negative terminal of the battery to the positive terminal. As the reaction proceeds, the metals are converted to another material and the electrolyte becomes weaker until finally, the reaction stops....

6

The cathode end is connected to the outer can of the battery (not the plastic casing but the metal directly under it), it's all one piece that is separated from the anode on the anode end. There is a metalized plastic film (PVC) over the can which has the battery markings printed on it. This is called the casing and no it is not conductive. If you scratch ...

6

Let's start with a very important point: With Lithium based batteries a thermistor is a nice last line of defence, but you seem to be making it the centre point of your thoughts. If your thermistor triggers on a Lithium based battery, purely from charging, you might want to hook that up to an airhorn so you know to start running. Do not get me wrong: I ...

6

Storing them "discharged" to ~3V with the device they were used in still preserves lots of energy in the battery. At 3V a Li-ion battery has almost no capacity left. In this graph two 800mAh batteries were discharged at various rates. At 0.1A there was virtually no capacity left at 3.0V. Even at 1A they were 99% discharged.

5

No to both questions. Turning one cell around in a two-cell pack simply creates a pack that has zero net terminal voltage, and this can't harm either the circuit or the cells themselves.

5

Plant a lemon tree - this will cover CO2 generation. You will also get some oxygen, shade, and other useful stuff. Don't ever burn any part of the tree or you may get CO. AS far as LED goes, wait till lemons are ripe and make yourself a Lemon Battery. You will need zink and copper metals for the electrodes, a US penny will provide both inexpensively.

5

If you look at the graphs for performance you will see that best cell capacity for various loads implies a minimum load resistance of about 3 kohm. Much lower than this and cell capacity drops from about ~900 mAh potentially down to ~600mAh at 1k loading. These approximately correspond to currents of 1mA (3k load) and 2.5mA (1.2 k load) and approximately tie ...

5

A cell is a bunch of chemicals between two electrodes. A chemical reaction produces an excess of electrons on one terminal, and a lack of electrons on the other. Once the potential difference reaches a certain level (the voltage of the cell), the reaction slows to a halt. If you connect a load to the battery, the electrons can travel between the two ...

5

Ah means ampere-hour, not ampere per hour (otherwise the battery would last forever). But your calculation is correct, the battery has enough capacity for delivering 2.15 ampere (for one hour), so if your robot uses 1.8 A, it lasts for 2.15 Ah / 1.8 A = 1.19 hours, which is 1.19 * 60 = 71.6 minutes.

5

Fully discharge and charge battery This can sometimes be useful as a step to correct capacity estimates in some "smart" battery packs, like those found in a cell phone or laptop. It is unhelpful for batteries which do not have a built-in controller, and outright dangerous for unprotected cells. Freeze the battery for 24 or more hours Chilling can be ...

5

Your concern is somewhat misplaced. At 1 A charge-discharge, normal 18650 Li-Ion batteries do not heat up. Consider that normal battery heats up only due to Joule dissipation over ESR, and the ESR of most 18650 cell is under 100-150 mOhms. So the maximum internal dissipation is under 200 mW, which, for the physical size (and surface area) of 18650 cell is ...

4

It may not be acceptable, but with minor modifications it can be. You must keep the current flowing into the battery within the limits specified by the battery manufacturer (not some random dude editing Wikipedia). For safety reasons, you should also ensure that no single point of failure can cause a high current (beyond the manufacturer-specified limit) ...

4

You can estimate the internal resistance (hence the shourt-circuit current), without using an ammeter. All you need is a single external resistor and a voltmeter. First, a battery can be modeled as a series of an ideal voltage source of $V_{BATT}$ volts and a resistor of $R_{BATT}$ ohms. $R_{BATT}$ is the battery's internal resistance. This model is ...

4

That basically depends on the manufacturer. I've had one laptop that would indeed fully charge the battery, then switch to battery power until it dropped to 95%, then restart charging. The battery died within six months, and I haven't bought from that vendor since. Typically, the battery is disconnected when fully charged, and then monitored for self-...

4

The chemical processes that happen inside a battery when it is being discharged take time to occur - if they cannot keep up with the load on the battery the voltage will drop and it will be seen as dead. One name for this is polarization. If the battery is left for some time the chemical processes can catch up and you can then discharge the battery again ...

4

In addition to internal resistance phenomenon which lowers the battery voltage under load, you should pay close attention to @Jasen comment about internal short circuits. Take a look at industrial-grade batteries, and you will notice that individual cells never share electrolyte. I suggest you try to put a non-wettable film (like pieces of a plastic bag or ...

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