Working on car electrical systems used to be easy. The battery simply provided power for the car’s starter motor when starting or to run the small number of accessories when the engine wasn’t running. The rest of the time, the alternator charged the battery and provided power for the rest of the vehicle and the ignition system. While very early cars didn’t have batteries, and some old cars had 6 V positive ground systems, most of us have lived our entire lives where car batteries come in several sizes (controlled by Battery Council International) and cars have a 12 V, negative ground system.
Times have changed. Cars don’t have distributors anymore, they have computers. They also have lots of gadgets from GPS to backup cameras and cellphone chargers. Batteries have had to get beefier and the modern trend is to also require less maintenance So, today, you’ll find that there isn’t just one kind of car battery. But how do these other batteries work and what was wrong with the good old lead acid wet cell?
For the purposes of this post, I’m not talking about electric car batteries which is a whole different topic — and most of them have a regular car battery, too. Continue reading “Car Batteries: More Than Just Wet Lead”
The news sites seem never to be without stories of Elon Musk and his latest ventures, be they rapid transit tube tubes in partial vacuum, space flight, or even personal not-a-flamethrowers. Famous for electric vehicles, Musks’s Tesla also has a line of solar products and offers the Powerwall home battery power system. These are tantalizing to anyone with solar panels, but the price tag for one isn’t exactly a dream.
[Nathann]’s budget couldn’t stretch to a Powerwall, but he did have access to a hefty ex-datacentre uninterruptible power supply (UPS) and a large quantity of lead-acid cells. From this he built his own off-the-grid power in the cellar of the home. It’s not as elegant as a Powerwall, but it can power the house on moderate usage, so he claims, for up to ten days.
On one level the installation is more of a wiring job than one of high technology, but the logistics of dealing with nearly 100 lead-acid cells are quite taxing. The UPS takes four battery packs, each clocking in at 288 V. The cells are joined with copper straps, and the voltage and current involved is not for the faint-hearted. An accidental short vaporized a screw and a battery terminal; if this were our house we’d put fuses in the middle of the battery packs.
The batteries are stored on wooden pallets atop brick pillars in case the cellar floods. The basement installation now is ready for the addition of solar and wind-based off-grid sources. Maybe your battery power solution will be less hair-raising, but it’s unlikely to be cheaper. Meanwhile this isn’t the first such project we’ve seen, though others usually go for 18650 Li-Ion cells, the use of lead acid remains a viable and economical solution.
Despite a lot of advances in battery technology, lead acid batteries are still used in many applications due to cost and their ability to provide a lot of surge current. But they don’t last forever. However, [AvE] shows that in some cases a failed battery can be restored with — of all things — epsom salts. If it makes you feel funny to use the stuff grandpa soaks in when he has a backache, you can call it magnesium sulfate.
You can find a complete explanation in the video below (which includes [AvE’s] very colorful language), but fundamentally, the magnesium sulfate dissolves lead sulfate build-up on the battery plates. The fix is usually temporary because this build-up occurs with other failure mechanisms like plate material shedding and collecting at the bottom of the battery. Obviously, epsom salt can’t repair damaged plates or do any other magic cure.
Continue reading “Epsom Salts Restores Lead Acid Battery”
When a friend finds her caravan’s deep-cycle battery manager has expired over the summer, and her holiday home on wheels is without its lighting and water pump, what can you do? Faced with a dead battery with a low terminal voltage in your workshop, check its electrolyte level, hook it up to a constant current supply set at a few hundred mA, and leave it for a few days to slowly bring it up before giving it a proper charge. It probably won’t help her much beyond the outing immediately in hand, but it’s better than nothing.
A lot of us will own a lead-acid battery in our cars without ever giving it much thought. The alternator keeps it topped up, and every few years it needs replacing. Just another consumable, like tyres or brake pads. But there’s a bit more to these cells than that, and a bit of care and reading around the subject can both extend their lives in use and help bring back some of them after they have to all intents and purposes expired.
One problem in particular is sulphation of the lead plates, the build-up of insoluble lead sulphate on them which increases the internal resistance and efficiency of the cell to the point at which it becomes unusable. The sulphate can be removed with a high voltage, but at the expense of a dangerous time with a boiling battery spewing sulphuric acid and lead salts. The solution therefore proposed is to pulse it with higher voltage spikes over and above charging at its healthy voltage, thus providing the extra kick required to shift the sulphation build up without boiling the electrolyte.
If you read around the web, there are numerous miracle cures for lead-acid batteries to be found. Some suggest adding epsom salts, others alum, and there are even people who talk about reversing the charge polarity for a while (but not in a Star Trek sense, sadly). You can even buy commercial products, little tablets that you drop in the top of each cell. The problem is, they all have the air of those YouTube videos promising miracle free energy from magnets about them, long on promise and short on credible demonstrations. Our skeptic radar pings when people bring resonances into discussions like these.
So so these pulse desulphators work? Have you built one, and did it bring back your battery from the dead? Or are they snake oil? We’ve featured one before here, but sadly the web link it points to is now only available via the Wayback Machine.