Continue to Site

Welcome to our site!

Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.

  • Welcome to our site! Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.

Cheap AA and AAA battery charger

Status
Not open for further replies.
The new Energizer Ni-MH cells that hold a charge for one year say on the label "Pre-charged"and are guaranteed for 5 years. Old Energizer Ni-MH cells were guaranteed for 3 years.

I have some Chinese AAA Ni-MH cells that came in solar garden lights that work pretty well. The ones marked 300mAh and 600mAh measure about 250mAh. The 300 and 600 ones look and perform the same except for the number wrongly printed on them.
 
just read from mne energizers ''made in china'' :)....
 
Modern Ni-MH cells do not need a trickle charge because they hold a charge for one year. Sanyo/Panasonic Eneloop and Energizer have them.

That's right, they don't need a trickle charge but they do need a topping charge to achieve full capacity. So after the -dV point they need a further charge to realise full capacity. This is the difficult bit as far as battery life is concerned: too much topping charge will overheat the battery and reduce its life.

Incidently, the life of a battery depends on temperature. For the longest shelf-life store it at around 10 deg C at 66% of full charge.
 
Last edited:
i'll switch to candles, easier :D....
 
Too true! batteries are troublesome things- love em and hate em- just like women! :sorry:
 
Battery charger ICs take care of the problems. They fully charge a battery but avoid over-charging it.
 
That's right and many companies have the chips so you can make a charger quite simply and cheaply if you need to. At one time making a charger was more difficult.

I asked already, but doesnt anyone use LiIon bats for projects. I bought 8 CR123s about 6 years ago meaning to use them in projects but, as usual never got around to it. Every year or so I check their charge and apart from one which was down a bit when I checked a couple of days ago- 15 min on charger- they have all been fine. The handy thing is that they have a nominal cell voltage of 3.7V, unlike the 1.25V for NiCad and NmH. This means that you can do some electronics using a single cell.
 
I have some 18650 Li-Ion cells from my daughter's first laptop computer about 15 years ago. Each cell charges to 4.20V. 6 years ago I used batteries made with two of the cells in series in a model airplane and last year I tested them and their voltage dropped to about 3.9V per cell so I put two in series in a handheld vacuum cleaner and they work fine. I have smaller Li-Ion cells from my daughter's first cell phone 17 years ago and they still hold a good charge after sitting all that time.

My radio controlled model airplanes use small lightweight Li-Po 2-cell batteries. They are fully charged by their balanced charger at 8.40V and the airplane's electronics turns off the main motor when the voltage has dropped to 6.4V. I store them during the winter at 3.7V per cell. I will buy some more Li-Po batteries on Black Friday because the batteries wear out after about 400 charge-discharges and each year they make new batteries with more power and more capacity.
 
Ah yes 18650s- magic things. I have done the same- salvaged cells from laptop batteries. Normally just one in a bank go US and the rest are OK.

Model airoplanes me too again, but not electric: sailplane and diesel. Haven't done aything for years but do watch the men catching the thermals with their motor assisted sail planes. We are by the coast with good breeze and plenty of hills which helps.

The best thing I ever saw was at an RAF base in Singapore: B17 bomber replica about four feet long, complete with four glow plug motors which were a job to balance. The aircraft wasn't a kit but built to scale from scratch. I miss the smell of dope and diesel fuel.

We also have a model car track in the area. They have a meet at least once a week in the summer.The speeds they get are amazing- must see what batteries they use, fast charge/discharge high current types I think.

I've heard about LiPro but never investigated further. Presumably they are high current types, may be like the model car boys use.

I've also played about with lead acid batteris too. Made a portable PSU for testing equipment in EMC chambers. Thats when I learn't about deep discharge lead acid batteries. First I just used a standard car (auto) battery from the garage down the road. I was very surprised when it didn't last very long! After all, if they can do 100s of amps to start a car they shoul be able to supply 10 amps or so, no trouble. At one time, before all this battery technology took off, lead acid was the only way for a decent amount of power.

When money was tight and welders expensive, I was going to make a welder with a stack of car batteries, say six, but a friend gave me a pro welder that was his Dad's so that project never took off. The welder I was given was a monster and although it had taps for different currents none were low enough for the sort of stuff I was making. Say you wanted to weld a chassis seam- there would be a big flash and and a big hole. The guy down the rad used to borrow it to make anchors for his boat out of old angle iron- he got on Ok with it. I plan to get a TIG welder with AC so you can weld ally.

On EOT there was a thread about charging batteries. Can't find it now, but one member suggested using a welder as the power source for charging a battery array- good idea I thought. You can get an 60A arc welder dirt cheap in England, low as £40 UK, if you shop around.

I had a 50A 4V transformer- scrap from some earth continuity test gear- and wanted to up the voltage for a battery charger. So I had this idea to make it resonant. I tried various capacitors across it. Nothing happened untill one capacitor hit the spot- scared me to death. There was this almighty hum, the transformer vibrated the whole bench and it started smelling right away. I instantly turned off and forgot about that idea.
 
Last edited:
When I was a kid my model airplanes used glow plug engines that burned methanol and castor oil. My smallest was 0.010 and the largest 0.35 cubic inches displacement. I used a big and heavy #6 dry cell to start the glow plugs.
I have a small American (ThunderPower) 2-cells Li-Po battery for my airplanes that weighs only 14 grams and is rated at 325mAh/70C. The 70C indicates its maximum continuous current is 0.325A x 70= 22.75A and its peak momentary current is double that.

My latest model airplane is an F-16 jet. It has an electric ducted fan inside that screams at 81000 RPM in my hand but faster when flying and it flies very fast (like a jet). It is lightweight so it can also fly slowly with its nose up high.

I never used a lead acid battery for anything except my car and my son's riding car when he was little.
 
Status
Not open for further replies.

Latest threads

New Articles From Microcontroller Tips

Back
Top