Ajoe

Base on Lipo Charger designed by Scott Henion
http://shdesigns.dyndns.org/lionchg.html

I have made 3 charger combined in single PCB, each charger has output voltage 4.2V.
Cascade them to become Charger fit for 2 or 3 cels Lipo pack.
They have worked well. The transformed that used here has 3 x 8VAC secondary output.

xuzme720

that's awesome! I bookmarked that link for my next rainy day I have free...if I ever get a free day, rainy or not! lol

Ajoe

The homebrew charger on duty

Charging 2S Lipo (8.4V), Two LEDs are ON

Charging 3S Lipo (12.6V), Three LEDs are ON

Trex

does each charger charge one cell of the 3S lipo?

How much does it cost to build the whole thing? Individual components are rather cheap but once its all ordered and purchased the total may be higher and smehting like a cellpro charger cheaper ...

Still its nice to build your own stuff

By the way ... NS makes a Lipo charger IC that can also be used for self made chargers .. i thought about it once but decided its not worth it...

Matt

Ajoe

Hi Trex,
Yup, each cell of Lipo was charged by one dedicated charger, look at the picture there are 3 chargers. Each of them has charging voltage 4.2V.

The cost are arround US$7 or US$8, maybe different depend on the country. For example the LM317 is only 20 cents here (Indonesia).
In my case, several parts are recycling from dead electronics equipment, it's make them become cheaper.

Sometime, DIY equipment is'nt worthed compare to ready build one from factory.
But self satisfaction is invaluable, isn't it?

Trex

Couldnt agree more!

I have a 3A - 6V BEC that I made from a LM350 for a few $

Matt

CHELLIE

Hi, Thats a neet looking charger, it seems to charge each cell individually, but it does not look to balance charge the cells, I could be wrong, or maybe you dont need to balance charge each cell by charging them seperate, Hmmmmm very interesting, take care, Chellie

Ajoe

@Matt,
Pls share me the cheap BEC

@Chellie
You are right, this charger doesn't balance each cell.
In my mind, due to each cell was charged individually, when they fully charged also become balance .

CHELLIE

Yes that make sence Ajoe, Take care, Chellie

fr4nk1yn

Great idea using three and the "low" voltage transformer. I've been using the DIY charger for a couple months after my bought charger died. I had the parts on hand from an abandoned project. In 3s it takes 17v which I can't feed with enough amps to pull off more than a 650mAh initial charge.
Used a .68Ω resistor that should be charging over 1amp.

How did you change the AC to DC?
What rate is the batteries charging?

Trex

The best source for ALL needs of RC is a ATX power supply.... Every cheap one will give you 12V / 10A or more.

I am just blinging mine out with Dual Selectable voltage from 1.5 - 12 V and build in volt and ammeter.

Matt

Trex

@Chellie:
By charging each cel with its own charger you dont need a balancer .. thats in general how the Cellpro 4S works...


Here is my BEC

It is built on a National Semiconductor LM350 ADJ. You can set any (as long as its below the input) output voltage by varying the drain resistor.

You can download the datasheet for the LM350 which shows the schematics for the voltage regulator setup. If you need any help or details let me know!

You dont need the capacitors but I added 1000uF on the output to make sure there arent any power surges

You do need a little heatsink.

If you dont need 3A you can also use a LM7805 (1 AMP) which can be found on soundcards, older PC power supplies and older mainboards.

In general you can recycle a plethora of parts from old PC!! My heatsink and 1000uF cap came from a mainboard

Here is a pic for size comparison. You need to assure adequate cooling under the load the are pulling from it to make sure it doesnt burn up.

I am also working on a SWITCHING 3A BEC that will be much more efficient but its harder to build.



http://img245.imageshack.us/img245/1725/becsn6.jpg

Ajoe

Just using simple bridge rectifier and Cap 4700 uF, My charger is capable to feeding up to 600 mA.

CHELLIE

That is really neet, that some smart people can use a old comp. and make a motor from the cd drive/hard drive to power their planes with and other old pc. parts can be used for chargers and BEC, thats really clever, i wish i had learned a little more electronics, I just know the basics, and it seem very interesting, my son and i did make a simple square wave oscillator , using a 555 chip, and made a custom amp regulator for a hydrogen generator for autos, using 3 NPN 2N3055 15 amp transistors, and regulated each one to only allow 5 amps to pass through it, and connected them up so we only got 15 amps total @ 14.1 volts we were trying to use each transistor at only 1/3 of there output to keep things cool, reason we had to do this, is because the amperage/draw of the hyd. gen. was regulated by the amount of electrolite in the gen, and it was temp. sensitive, and would vary with temp and the electrolite getting weak, so now we can use a lot more electrolite, and the amp draw will always stay the same, one problem solved, BTW this hydrogen generator works great, it uses lead plates, and will double the fuel mileage on most cars @ cruise speeds, we have been working on this project for a few years, it uses distilled water, breaks it into hydrogen and oxygen and is drawn into the eng. with vacume, and has a auto fill water system, and makes hydrogen on demand, we will be selling the plans soon, it can be made with material bought at like home depot and radio shack, take care, Chellie

Trex

Do I understand this correctly that you use power from the vehicles 12V on board power system to break water into hydrogen (and oxygen) and you feed this into the engine?

Interesting idea but wouldnt it consume more energy to make hydrogen as you gain by burning it?

Matt

CHELLIE

Hi Trex No it produces more energy, with a cars 12v+ ,although the hydrogen generator is not overunity in its self, there are a lot of things going on here, first you have the added hyd fuel, second the hyd. fuel catalyzes the gasoline and makes it burn 25% more efficient, third you have pure oxygen that makes everything burn better, and the fuel is produced in a vaccume, more volume than if made not in a vaccume, lots of things going on, so your not really getting more energy from just the hydrogen fuel being produced, but from all the other positive events that are taking place with the hyd. fuel and oxygen, its been called brown's gas, Rhode's gas and a few other things, when oxy & hyd gas/vapors are mixed together, the hydrogen that is made, produced these gas savings at cruise speeds only, here is why, it takes only about 8 to 10 hp to maintain your cruise speeds, the hyd produced will make 4 to 5 hp, the gasoline makes up the other 4 to 5 hp, so half of your fuel to maintain cruise speed is made with hyd. for up to a 50% gasoline fuel savings, take care, Chellie

Ps I listed one hyd generator, but mine is much better

http://www.eagle-research.com/fuelsav/hyztechld.html

N3CLI

Chellie

How is yours better? Is it available as a kit?

Fred

CHELLIE

Hi Fred Its bigger with bigger plates in it, so it makes more gas, it workes under vacume, and has a float switch, hooked to a solenoid valve that draws water into the generator Via vacume to refill the generator as the water is depleated, then turns off, and is a simple design, no electronics to it really other than a amp regulator, at this time we are working with carbon fiber plates, so we can take the lead out of the generator, we will be selling the plans to it, and later maybe the kits, with the carbon fiber plates, still need to do some R&D with the carbon fiber plates, so should know soon if the CF plates will work as well as the lead, we have tried stainless steel, copper, and other metals, and lead so far workes the best, hoping that CF will work as well or better, take care, Chellie

CHELLIE

how to make a lithium polymer charger with output 24V/10Ah?

Hi, Will that charger be for a EBike ? it will be cheaper and better to just buy one, this one will charge at 24 volts 10 amps

http://cgi.ebay.com/2-8-cell-BMS-LiF...item4cec90828a

lvjet

Hmmm, If each voltage reg is set to 4.2 VDC and you have to have a positive and a negative lead to charge " individually" at 4.2 VDC you would short out the cells. If your talking about the 1st 317 reg set at 4.2 and the second 317 reg set at 8.4 and so on , then you could use the the standard strip to plug into the battery. Ive been there done that. If your method is to set each 317 reg 4.2 VDC higher than the other it will charge but with a very inconsistant cell voltage. Not good!. The fact is you cannot charge a 3 cell to 12.60 VDC with 3 positive leads of 4.2 VDC in parallel.

kyleservicetech

Yup
I made something like that last year for my A123 cells. The charge rate was only about 200 Ma, since its purpose was only for balancing the cells. And that balancing worked very well.

As it turns out, balancing only requires that at the end of the charge cycle, each cell in a series string of cells winds up at the proper voltage. that is, 4.2 Volts DC for a LiPo cell, and 3.6 Volts DC for an A123 cell. And, that charger must never allow any cell to ever go over that 4.2 or 3.6 Volts DC value during the charge cycle.

Nowdays you can buy a ready to go charger for less $$$$, but there is some satisfaction in doing it your self.

rcers

Wow - 5 year old thread back to life....

kyleservicetech

Yeah, nowdays, you can buy a LiPo/A123/LiFe quality charger for less $$$$ than it costs to build one from scratch. (I've done this several times!)

rf96816

Maybe. But this home-built charger is better than most you can buy. It charges each cell separately and doesn't need to balance.

Balancing is slow and often wears cells out quicker by wasting charge
during balancing. Balancing chargers are more complex and error prone.

Independent, non-balancing chargers like this one are better and simpler.

Balancing is bad. Charging each cell separately to the right voltage is way better.

JetPlaneFlyer

Err.. Isn't that exactly what a good balance charger does

It's certainly what my iCharger does, you can see each cell individually coming up to it's final target voltage as the charger does it's stuff.

Modern balance chargers don't balance like old fashioned 'stand alone' balancers i.e. they don't discharge the highest cells to match the lowest cell.

This is a fun project no doubt and 10 years ago when commercial liPo chargers were expensive and not very good, maybe a practical proposition, but lets not pretend it does anything 'better' than a decent modern retail charger. For instance what use is 600ma charge current these days? It would take 10 hours to charge a 4000mAh battery (bear in mind you shouldn't leave it unattended for those 10 hours) ! I could charge that battery in 6 minutes (c rate permitting)