Battery safety
Things you should know about battery charging and good practice
We all know about flat batteries — usually it’s the TV remote going on the blink just when you want to watch something.
Anyone who has experienced smoke alarms going flat in the coldest part of the night will understand that temperature has something to do with this magic.
All batteries are a chemical reaction, and for the typical battery in your remote, once the reacting items have done their thing, it’s time to dispose of them.
Rechargeable batteries are more environmentally friendly and, depending on the intended use, usually work out a lot cheaper over the life of the item.
However, not all batteries are the same, and the charging methods vary, so the point of this article is to raise awareness and maybe help prevent some potentially dangerous situations.
Battery history
According to the Battery University (batteryuniversity.com), batteries could have been around much longer than 400 years, but it was in 1796 when Alessandro Volta started developing a useable battery, albeit a single-use version (known as a ‘primary’ battery). In 1859 Gaston Planté invented the first rechargeable lead-acid battery and this system is still in use today.
Nickel-cadmium (NiCad) batteries were invented in 1899, but it wasn’t until 1947 when they were sealed that they became popular, and then in the 1990s they became unpopular in Europe due to the risk of cadmium leakage when disposed of.
NiMH, or nickel-metal hybrid, batteries became the replacement as they are more environmentally friendly.
Lithium batteries came on the scene in 1991 when Sony became the first to use lithium ion. It seems that the invention was due to work by John B Goodenough but was patented by Sony.
Voltage
Normal alkaline batteries are 1.5V, while the rechargeable ones are 1.2V. While the voltage difference may cause some devices (cameras mainly) to misbehave, it is the current available from a rechargeable that can cause issues.
So the point of this article is to raise awareness and maybe help prevent some potentially dangerous situations
Most alkaline batteries can only deliver 1 to 2A, but a rechargeable can provide 10 times that. It can melt connections and destroy wiring in most toys if the motor gets jammed or stalled and, as you know, the kids always think it’s fun to run their toy as fast possible up against the wall to see what gives first.
Lipo
These look like a normal AA battery, but are 3.2V and I’m aware of one or two ‘accidents’ that have killed the device. So be careful picking up one of these from those battery stands at the local shop.
If in doubt check out the fine print.
NiCad
NiCad batteries were popular and needed special charging to prevent a ‘memory’ build-up — the battery didn’t actually remember anything, but the discharge process caused the electrolyte to crystalize, and short discharge, then charge cycles would increase the buildup, which reduced the charge available, hence the ‘memory’. Eventually the crystals would short the battery and it wouldn’t charge. A high-amperage pulse across the battery would blow away the crystal build-up and a few full charge/discharge cycles would bring it back to life.
They have a high leakage, so they need regular charging to stop discharging even when not in use.
Li-ion
These were introduced about the time that mobile phones became portable and got rid of the memory problems faced by NiCads. The voltage had changed from 1.2 to 3.6 and the phone handled all the charging duties. The early ones only had a charger socket, so mixing and matching of chargers wasn’t the problem that it is now.
There are many different mixtures making up a modern lithium battery. Some are designed for low discharge rates (1C) and have protection circuits between the cell and the leads. Others are designed for high current (20C) and have no protection. Try to use the type appropriate for your purpose.
Charging
I’ve heard it said that a charged battery is like a hand grenade with the pin partially pulled out, and while this might be true for a lithium-based battery, all batteries pose a risk.
Lead-acid batteries vent both hydrochloric acid and hydrogen as part of the charging process. As the battery ages, the effects can usually be seen as oxidation on the terminals, or rusting of the holddown clamp or the battery mount.
Baking soda will neutralize the acid and greasing the terminals stops the acid from having a surface to attack, but charging a car battery should be done in a well-ventilated space and, more important, with a quality charger that can control the charge being delivered.
The charge time for a lead-acid battery is 12–16 hours, and while higher charging rates with special chargers can reduce this to 8–10 hours, it is not a quick process.
Most new car batteries utilize calcium and require a higher charge voltage, so you need a special charger to recover a flat battery. In older vehicles the alternator charges at 13.6V, while modern cars are often 15V to suit the newer batteries. I have heard of people jump-starting a vehicle then driving it, only to find when they stop at the destination and then get back in, that it’s still flat.
Deep-cycle batteries, as used in mobility scooters, etc., have a much heavier plate construction to handle multiple discharges and recharges. The trade-off is that they are not designed for high discharge such as when starting vehicles.
For batteries on constant charge, there is a trade-off between restoring full capacity and electrolyte loss, and we found 13.2V was a good figure to use. Lead-acid batteries left for long periods will discharge, but, more important, the acid will stratify, which tends to wear the bottom of the plates. A charge, ‘boil’, or shake mixes the acid, but I’m not sure how you safely shake a lead-acid battery that contains liquid that tends to spill out.
Battery fires
Lithium batteries require even greater care when charging, as the heat buildup when charged can cause thermal overload. This can spread to the other cells, and with the constant size reduction, the cells are being packaged closer.
There have been plenty of reports of mobile phones catching fire, and this has been extremely costly to rectify, even for the very large multinational company involved. However, this hasn’t just been a problem for mobiles, as Boeing (en.wikipedia.org/wiki/ Boeing_787_Dreamliner_battery_ problems) and others (nexceris.com/ learning-from-4-damaging-lithium-ionbattery-failures/) have found out.
Today we can buy lithium batteries from cheap, foreign-sourced suppliers, and we can find chargers for batteries at equally low prices. The big problem
There have been plenty of reports of mobile phones catching fire