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Terry

LiPo capacity checker

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Before I start a new project that I don't have time for can anyone tell me if I can buy a Lipo capacity checker that discharges each cell though the balance lead and outputs the capacity readings of each cell on an LCD screen ?

Thanks, Terry

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Single cell capacity checking is common on the more elaborate chargers. Reporting capacity on several cells in parallel isn't something I have seen, but I'll bet it exists in commercial form.

But why rely on a low cost ready to use solution when you can build your own? Sure, you're going to spend more and consume a lot of man hours, but in the end you'll have plenty of interesting things to share in the forum.

That's what you get for asking in a DiY forum. :)

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I haven't seent hat yet. Maybe this beast can?

Hmm, upon reading it seems not: "Equalizer current: 250 mA"

All balancers I've seen use simple resistors between cells that are switched on or off... which is of course a real pain if you need to balance a 16Ah pack that has 2Ah imbalance, that's a lot of hours of balancing...

What I do is discharge the pack, and once the charger switches off because one cell is too low I then discharge the others individually. Much faster.

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Well for the time being I have made a little unit that cuts the lipo off when any cell gets down to 2.5v then I read the capacity from my astro watt meter. I would still like an all in one unit that gives the capacity of all the cells but this will do for now.

If anyone is wondering why I don't just read the capacity from the charger it's because if one cell is bad the readings are way out. I had a small pack that I use to power my video TX go dead after 15 min in the air and the charger said it should last for an hour minimum.

Terry

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To me it seems all you need is a little multi-cell voltmeter, or a charger with an integrated balancer. Suppose your pack is charged, you connect the pack to the charger, start discharge. As the charger monitors the voltage of each cell it will stop once the first of them has reached the minimum. There you have the "usable" battery capacity, and by just having a look at the individual voltages you'll quickly see if there's something wrong like one being way lower / higher than the others. If it's the case, you should dig further into the problem. I'd first charge normally, wait until the charger stops because one cell is too high (if it's the case), and start a balance process if needed. Then discharge/charge once again the same way and check if the balancing cured the problem.

If one cell really has a lower capacity than the others, as in it's always the first to trigger the end of the discharge then you'd simply want to toss the pack.

Instead of the charger with balancer you could just use a voltmeter - check the voltages of each cell regularly. You have more risk of damaging your pack that way though, as a charge/discharge won't stop if one cell is exceeding limits.

If anyone is wondering why I don't just read the capacity from the charger it's because if one cell is bad the readings are way out.

If your cell is that bad your pack is most likely already good for the trash in the first place... but after a discharge/charge cycle the capacity indicated by the charger should be pretty close to what's usable anyway. If not your pack might have gone bad after the last charge or in flight.

Edited by Kilrah

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If your cell is that bad your pack is most likely already good for the trash in the first place...

For sure it is trash but I would like to know if the other cell is good so that I can use it in another pack. I don't like to throw away good cells, often these can be used for many more months. Think green :D

My main issue is with the charger ( cellpro 4s ) as it always shows the capacity as way over what is useable so gives a false impression of how long it will last in use. This could have led to the loss of my plane but I was lucky and it was still in visual. I would just like to warn others that the reading of the capacity when charging could be missleading and the capacity should be checked while discharging. I'm sure some of you guys do this already but I guess there are some like me that thought the capacity on the charger was much more accurate.

Terry

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Couldn't you hack something like this...

http://www.hobbycity.com/hobbycity/store/u..._300mtr)_870mhz

wireless checks your cells up to 6, 300m range so you would have to fly by every once in a while. Or use it on the ground, just add the balancing circuitry and ur done.

Edited by headhunter23

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Thats a very clever little gadget but I see no real need for it unless you are maybe flying a copter. I'm more interested in keeping a closer eye on battery performance on the ground so I never put a bad one in the air. I use a balance charger so I don't need another balancer, I just want to know the capacity of all my cells.

Terry

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Start with a "balanced" freshly charged pack. Put it on the charge system (Triton or something similar) and set it for a full pack discharge cycle. At the end of the cycle, you will see the mAh for the pack. If you choose a reasonable discharge current it should be similar to the pack rating (or the measured mAh when the pack was new). Now measure the voltage of each cell and confirm they are all within a few millivolts of each other and are above the minimum allowed voltage. Open cell vs. loaded cell voltage specs are different, so be sure to use the correct specs.

If at the end of this you find that something is goofy, then you have a pack with one or more bad cells. Finding the bad cell(s) will be easy.

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Ahh so your saying I should buy a charger with a discharge function, I was hoping to find a stand alone discharger. I will have to visit my local model shop :)

Terry

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I hear real good things about this one http://www.hobbycity.com/hobbycity/store/u...Balance/Charger and it's little brother the 106.

There is an ongoing string on RCG with the Mfg. worth looking at. http://www.rcgroups.com/forums/showthread.php?t=839657

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For sure it is trash but I would like to know if the other cell is good so that I can use it in another pack. I don't like to throw away good cells, often these can be used for many more months. Think green :D

Well.. if you've been using that pack with a damaged cell for some time, it means that the others have repeatedly been overcharged/discharged. So I wouldn't reuse them for something sensitive. And as I already have a heap of those "unsure" remade packs I never know where to use in the end, I now toss the entire defective packs. Or have some fun with fire... ;)

Ahh so your saying I should buy a charger with a discharge function, I was hoping to find a stand alone discharger.

Well, I guess a discharger only with measuring functions etc wouldn't cost much less than a full-blown charger ;)

I personally have that one :

http://www.hobbycity.com/hobbycity/store/u...alancer/Charger

Very happy with it. And the PC interface is neat :)

post-30-1220688510_thumb.jpg

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Thanks Kilrah, will it give a graf like that for each cell or only for the whole pack ?

EDIT ok I can make out the numbers now and it looks like each cell, thats good.

Now to see if it's availible in the UK.

Terry

Edited by Terry

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Well.. if you've been using that pack with a damaged cell for some time, it means that the others have repeatedly been overcharged/discharged

No, I have been charging with the cellpro charger that charges each cell via the balance lead. The faulty cell that has discharged quckly has never gone under minimum volts until this last time and the good cell was well up.

Terry

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Thanks Kilrah, will it give a graf like that for each cell or only for the whole pack ?

The charger gives a bunch of infos (total pack voltage, individual cell voltages, current, temps, input voltage, charging power, capacity,...).

I'm using LogView to capture and display the data, where you can choose all the curves you want. There I only had pack voltage and current displayed. But as it was a single cell... ;)

I was testing an A123 cell over a couple of cycles to see what the curves looked like.

Now to see if it's availible in the UK.

If you really want to pay double/triple, yes...

Just order from hobbycity. And be careful, one tends to spend a lot of time and ultimately money on there with their insane prices ;)

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And be careful, one tends to spend a lot of time and ultimately money on there with their insane prices wink.gif

Boy! That's an understatement if I ever heard one.....

Edited by W3FJW-Ron

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This topic remember me my small lipol voltage monitor I did for heli on tiny13 uPC , alarm triger is regulated by potentiometer .

This is the funy version with airwolf music as alarm :

Normaly the alarm is not music , but is very laud and anoing - landing must be done for reset that noise .

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That's great. You should make kits or finished units available. I'd sure buy one.. How far away can the sound be heard?

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That's great. You should make kits or finished units available. I'd sure buy one.. How far away can the sound be heard?

Sound normally can be hear in 50M distance , when the unit stored in for exapmle plane balsa or depron body is working as resonanse case - the distance I check personally (when was serching lost plane) is about 100meter . When flying in air - even more .

A yes , after a small anonse on my domestick heli forum I had many asks about this monitor from users , now a hundrets of them are flying in many helis and planes in Poland . The main goal is that alarm triger is regulated by potentiometer - so can be customaized for any electronic and engine setup on variouse weight heli and planes , can be regulated for custom time we need to landing . Wth planes are not so big problem but heli without power are charm gliding like hammer .

Now all units are sold out , however project of new improved version is already ready .

Here is history of project : http://www.epheli.pl/index.php?name=PNphpB...84&start=60

And now - some translations .

The price was about 10USD with two superbright blue leds . The functionality is mainly explained on the film from post above . Working well with 3S , 4S , 5S batterys , was tested even with 6S as well . Working also with other type like NI-MH .

LEDs are intended for emulation of position lights (can be connected or not , that is not important) , near the alarm level are flashing quickly , when the voltage get lower of triger level - alarm is turning on and can be turn of after landing and reconnecting power .

The lipol monitor have also build-in function of 30minutes timer turning-on alarm after that time (thanks for that "theorethical" function I was able to find my plane in real practice :) ) , finally that function bacome very usefull after any unfortunate far in-bush landing , or in case if someone forget to disconnect the battery after fly .

As the software improvement for volage measurement in especially for heli - the monitor is immune for any quick changing votages in case of fast throtel pushing - so this help to aviod any false alarm trigering for cases of quick gas lever using .

Alarm is trigered only when the voltage is lower the triger level for period more than a 4-6 seconds .

This is how it looks :

regulacjacx2.th.jpg

How connect LEDs:

s6300364cz6.th.jpg

How connect unit for battery :

s6300400kw7.th.jpg

Here is the complete documentation and software as rar archive for dowlaod . For personal use only , not for commercial use alowed .

There are 3 type of software - in functionality are the same - the difference is only when you connect the unit to battery - in frst case it just start flashing , in second it made a short "pi-pi" signal , in third is play short part of toccatta of Bach :) .

http://www.sendspace.pl/file/87v5gJXz/

or

monitor_flash_sound.rar

Here is the how to mount device by hands (normally units was mounted by mashine) :

s6300431sh7.th.jpg

So that is I think complete info about .

I forget to show also - this is new version , what will be probably avaliable soon - weight lighter , with new improved harware , new better software and probably will be cheapper :

2layersij9.png

heliat13flashtesttm3.png

Edited by remzibi

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Thanks Remzibi. When I find out how & where, I'll buy 1 of your new units when they become available. In the meantime I'll spend some time looking over the forum with the help of Babblefish of course. I do like that music. It's a real attention getter.

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