greetings to all DIY gurus here,
 
 i was looking for diy lipo charger and found that scott henion is very famous and best known, need you help in deciding to build or not to..

here is the link:
http://shdesigns.org/pdf/lionchg3.pdf

as far as i got it, it uses a 12.6 v to direct charge battery, no balancing, can you say if it is ok , many people have been using it without any complaint, and did anyone make it in our forum???

pls help in deciding...

If you're building it yourself because you like making stuff and you know how the schematic works, go ahead.
Make sure the circuit has at least a full charge cut-off or indicator.
Also, look for schematics that come with a battery monitoring IC made for LiPo/Li-Ion, they have better voltage regulation and a more accurate cut-off voltage.
Find out the cost of materials and decide if it's worth a DIY or just buying an off-the-shelf item.

There are LiPo chargers as cheap as about 600/- that come with balance feature and can handle up to 3s. And for all know I about LiPo packs, I'd buy a charger.
Good luck!

I would advice against experimenting with Lipoly Batteries.

Check ur pm sir, I'm having charger and can afford u at very reasonable rate.! Don't build it, lipos are not good to play around with.

@Anjanbabu- after seeing the post in rcforum i was exited to build one and the cost was around 300 only, but thats not about the cost it's about interest that what keeps diy alive, and it does have a led as an indicator.

@lastrites- yeah thats what backing from doing this project

@incredible007- i do have a charger, thanks for ur offer

 thanks guys for this super fast reply, the circuit do has a good reputation as i have seen, the problem is it doesn't balance charge the lipo rather than it provides exact 12.6v which should be applied at the discharge wires, any word on this...

Welcome

guys depending on the input from you guys i will decide whether to build one or not, so pls help...

i think its not a good idea cause no two cells are having same characteristics in a pack if you directly charge them one may get over volltage
if it happens you will destroy your lipo
just my personal opinion

       thanks pratap for ur opinion but was just wondering how come there was such a craze for this circuit, more than 2 lakh downloads, and atleast 10,000 done it without any problem...in btw where do u live in vizag, didn't know there was plane lovers in vizag, will be glad to meet u..

Ok, not accusing the posted schematic to be faulty, just suggesting that there are better ones that use specialized battery monitoring ICs.

When it comes to LiPo chargers, quality matters. It may seem to work fine but on the long run you'll know how bad it affects your battery if the charger has inaccurate cut-off voltages. And the lack of balance feature is obviously a downside if you're planning on using it regularly.

hmmmm ok.... good point..

One more point to Add,

The components we get are called either Hobby grade or Student Grade and have high value of tolerance.
Lets say a 1K resistor, the Student grade might vary from 900ohm to 1.2k and its Commercial or Military grade counterpart will be exactly at 1K.
Lipos are too sensitive and it cannot take any slight abuse and it may tamper the useful life of the battery.
Commercially available chargers a made of commercial grade components and may go little off the Ideal values to save the battery

Lipo charging without balancing? Strict NO NO.
And those lakhs of downloads, no one knews how many actually built it.
Im a DIY guy but wouldnt take chance for a Lipo.

If you have a very old used swollen Lipo that you wouldnt mind burning, you can go for it.

Ashok.P

woww... that i didn't know thanks for sharing that Ashok, highly appreciated

Me and my friend build one each, we are now building 7 of then and no problem at all, ( my batteries range from 1s 50mah to 2s 4000mah)

http://www.rcindia.org/batteries-and-chargers/diy-lithium-ion-charger-1-3-cellsselectable-current-for-60-conditions-apply-!/

REF :      the link:

http://shdesigns.org/pdf/lionchg3.pdf

PLEASE NOTE THE CIRCUIT IS A Li-ION CHARGER AND NOT A LI-PO CHARGER !!!

THERE IS A DIFFERENCE

Please elaborate your version of so called DIFFERENCE 

As far as i'm concerned both are same
http://en.wikipedia.org/wiki/Lithium_polymer_battery

AND i have personally worked on battery tech. (mainly graphene and its applications in battery)

SO TELL ME.

This circuit seems to be able to charge the whole Battery at once and not the "cells individually"

Well, that's the basic idea behind the LiPo's. You need to charge each cell seperatly or else if cell1 gets 100% charged while cell2 still at 80%, this circuit will continue to charge even cell1 which directly will lead to cell1 getting overcharged. And you end up with a fire maybe?

The most significant difference between a Li-Po Charger and a Li-Ion charger is that a Li-Ion charger charges the whole battery at once but a Li-Po Charger charges each cell individually.
There are other differences too like LiPo chargers are more precise and sensitive when compared to Li-Ion chargers.

No both employ same technologies i.e charging and balancing and are very precise!


yes that's correct but there is more to it.


This is one of the scenarios where balancing is required !

 

Here is a question.

Hyperion selling top quality Lipos doesn't provide balance cable up-till certain capacity ?

Ex. these are 3S, are they fire proof ? one can charge them at 5C !

1.http://www.hyperion-world.com/products/product/HP-LG325-0120-3S
2.http://www.hyperion-world.com/products/product/HP-LG325-0180-3S
3.http://www.hyperion-world.com/products/product/HP-LG325-0450-3S
4.http://www.hyperion-world.com/products/product/HP-LG325-0240-3S

When and how cell in-balance occurs in a pack ? how do our charger work? do they balance and charge at the same time or at the peak or initially how ?

I Agree. Few of the Li-Ion batteries like the one in laptops are balance charged.

Well, Balance charging is always paramount to Li-Po batteries for safety and longevity.

Here is an excerpt from a Document from Hyperion explaining the reason for the absence of balance leads from their smaller batteries:
http://media.hyperion.hk/dn/eos/EOS0606i-MAN-EN.pdf

IMPORTANT NOTE: Lithium polymer cell types should be charged/discharged while connected to
Balancer. Charging/Discharging without balancer connected greatly increases the chance of
accident. The larger the pack is, or higher the cell count, the more critical it is that Balancer be
used. Only very small LIPO packs in 2S or 3S configuration (such as 100~300mAh) should ever be
charged without balancer (these often do not have a balance connector, to save weight).

While balance charging these small cells are still recommended for the safety and longevity of the cells, Hyperion considers the weight being saved to be more beneficial and have sacked off the balance leads from these batteries. Since these batteries contains small capacity cells, it's not going to be that big issue with regular use but once the cells depletes or accidently gets slightly overdischarged, their depreciation certainly will accelerate. There is no doubt about it.



Some of the major reason of a Cell imbalance:
1. Difference in Internal Resistance between various cells in a battery.
2. Accidental over discharge by the user leading to one or more cells getting depleted and loosing part of it's capacity.
3. Heat. The centre cell stays hot longer than the outer cells in a 3 cell pack.

Also, Since LiPo's goes to high discharge rate while being used, the slightest difference in the IR values is enough to create the imbalance.


Let's look at how balancing work.
Balancing while "Charging":
The Balance charger just tries to charge each cell to a specific voltage (lets say 4.23v). Once that happens it simply stops charging that cell. Since the Balance charger does this for all cells, basically you end up with a battery with voltage on each cell as 4.23volts. Which means a balanced battery.

Balancing while "Balancing"
In this option the charger tries to get the voltage of all cells to a specific voltage (as specified by the user) by discharging the cells which are "over the mark" and charging the cells which are "under the mark"

To sum it up, Balancing is all about "getting the voltage of each cell to be as close to each other as possible; either by charging or discharging".
It's all about "Monitoring each cell while charging" and stopping individually as soon as the desired level of voltage in the respective cell is attained. No rocket science in it.
But in order to attain Balancing you need to work on each cell individually which the charger in the above circuit is unable to do.

@ sahilkit sir the link is not working for the thread.

All this is because of poor cell manufacturing, also there is the rate at which one charges these packs !

Well simply put it works for me and the people i know, have put about 70 plus charges of various capacity (2s @ 70% of 1C)  

Strange but that seems to be the case. (search the thread)

sahilkit quote "Please elaborate your version of so called DIFFERENCE  "

One is forgiving of the charging voltage and TIME the other LiPo is not... It will swell and burst... when over charged or current or voltage is high. As a lot of mobile users will tell when their phones have exploded ...

Anyways the choice of what you want to do is yours.
The risks was asked, suggestions and opinions have been given...

[based on experience and as a hobbyist electronics and aeromodelling]