mickey-gem

Is it possible to somehow, bring a lipo pack back once it has dropped below 3 v. per cell?
I have a cell lipo 860 ma that is at about 7-8 v total for the pack. Is it salvagable? Can anything
be don to re-condition it? Thanks for your replies!

Matt Kirsch

My Feedback: (21)

It won't be 100%, but you can slow charge the pack with the right power source to gradually bring it back up to 3V per cell. If you went below 2.5V per cell, the pack will be pretty severely damaged.

What's the right power source? Depends on how many cells in the pack. You don't say how many cells are in the pack.

mickey-gem

Oh, it is a 3 cell thunder power 860 ma pack. I have a great planes Trition charger.

woodduck-RCU

You might be able to get the voltage backup close to 3.5 but the pack will never have the same mah capacity. I would doubt if you could get a 100 mah charge into it. Unfortunately an expensive lesson we have all had with lipo's

miltm

My Feedback: (3)

The 3V per cell rule is a very conservative number, but would ensure maximum life and health of the pack over the long run. A more realistic number is 2.5V as an "absolute" min.

That being said, I inadvertantly left a new Kokam 1500 3S1P pack plugged into my plane's ESC for about a week. Even though the ESC has a switch, that's still a no-no, since power is still slowly drained. When I discovered my mistake, the cells were down to about 1.8V each! I figured I'd just ruined a brand new pack, but using my Triton was able to coax it back to life with a very gentle charge rate of 0.1A until the pack was back to 9.0V. Then I used my AstroFlight 109 to charge it back to full at a rate of 0.3A.

I then put it on my West Mountain Computerized Battery Analyzer (a great tool) and dischared it at 1.0A. When compared to the initial tests I had run on this pack, fresh out of the bag, I was amazed to see that the Voltage drop was slightly less throughout the cycle, and the capacity had gone up about 10% after my SNAFU!

Only time will tell if the life expectancy of this pack was compromised (I'm guessing yes), but the point is that there's a good chance some the "hard and fast" rules about LiPo's may be partly the manufacturers fear of liablility. Of course you should always strive to abide by the rules for safety's sake!

--- Milt

Matt Kirsch

My Feedback: (21)

The cell's capacity and longevity have been compromised, but by 90%? Maybe, but probably not. 8 Volts for the pack is still well above the absolute minimum of 2.5 Volts per cell, where the REAL damage starts to happen.

Now, did you run the pack down too far in an airplane, or did the pack just drop to 7-8 Volts on its own?

If the pack's voltage dropped down on its own, then the pack is bad. You must dispose of it properly, by soaking in a salt water solution until it stops bubbling, then tossing in the regular trash.

If you ran it down by mistake, you MIGHT be able to revive it. This process will require extreme care and extreme caution. You will want to literally hover over the pack with a voltmeter while it's charging, so as soon as the pack goes over 9 Volts, you can pull it off and go to the LiPoly charger.

The point is to slowly bring it up to 9 Volts. You can do that by using the transmitter side of a wall wart charger on a 3S LiPoly.

A10FLYR

My Feedback: (1)

Matt, can't that be done with a 109? I think the stated min is 50 MA but I think it can be set lower.

miltm

My Feedback: (3)

Matt,

With all due respect, I strongly disagree with your suggestion to use a "wall-wart" charger on a LiPo pack!!!! Although you did warn the guy to hover over the pack, it is still unwise to recommend such a potentially dangerous procedure. He mentioned he has a Triton charger, and that is a better tool to use for this job. As I mentioned on my post, I was able to bring a badly discharged pack back to life using my Triton. It did only go for about 15 minutes at a time until giving me a warning error. Then I just unplugged the battery and plugged it back in. Repeated this two times until I got the pack back up to a more reasonable voltage.

My point is... the Triton was monitoring the pack much better than I could have done with a "wall-wart" and voltmeter. I was still hovering over it for safety purposes, and I believe the Triton can do a lot better job of Constant Current-Constant Voltage charging than any wall transformer.

A10FLYER ---

As far as using a 109 in this case... You have to be very careful to check what the 109 "thinks" it's charging. In my case, it read a 3S pack as a 1S pack. that's when I figured it would be better to go over to the Triton.

--- Milt

mickey-gem

Thank you for your responses. I left the pack connected to my speed controller overnight
and well in to the next day. I did not want to attempt charging it again until I knew if it was
even safe or worth the attempt. Thanks , I will try charging at .1 on the Titon to bring it over 9V.

A10FLYR

My Feedback: (1)

Ahh yes....I hadn't thought of that!![]

rieger202

im so lost on what ya'll are talking about. all this voltage stuff. i have a BLT but im getting a E-Starter and i was gonna get a li-po battery and charger but u guys make them seem so complicated and confusing. Should i just stick with NiMH for now? Or can u clear this up. it seems that if u leave them running to long u can ruin them or sumthin??? im lost plz help.

A10FLYR

My Feedback: (1)

By all means GO WITH LIPOLY!!!! You'll be glad you did!!! Do Yer research and treat the batteries with care. You won't regret it.

PaulVi

There is a ton of both good and bad information on the forums about lI-Po's

2 things i recomend (good or bad)

1) buy a computerised charger like the triton (you will not be sorry) it can be used for mantinace charging as well as full pack charging
2) make sure you have a speed controller designed to cut the motor off at the correct voltage (3.0v per cell) (Safety voltage) (2.5 is the arguable part)

If your ESC knows when to shut the motor off you ability to drain the pack to a point that is not reversable will be greatly reduced.


LI-PO's are great as long as you follow the directions; When charging an automotive battery do not exspose to sparks or open flame (No Smoking) we have all learened to follow simple safty rules for other battery types LI-Po's are no diffrent just more rules..

mickey-gem

I feel your pain. I was playing with a new plane and motor (did not test VDC or AMP Draw) just went flying, plane was a screamer for the first 2 minutes and then shut off. Humm lets try another pack and another test... Same thing Try the 3rd pack... Well all 3 1200mha 2 cell packs were not recoverable slow charged them and every thing... the pack voltage is fine and every thing looks great untill you put a load on the cells then Nada.... I think the packs put out aroung 150Mha before giving up and voltage starts to drop..

I hope you have better luck follow the slow charge till 9vdc and and medium charge rate till full... in your case after reaching 9.0v take it off the charger and let it rest for a bit then measure the pack again (No voltage drop continue to step 2) if there is a voltage drop put it back on the charger at the lowest rate you can untill it is at 9.0v again.. repete this step until the pack remains at 9.0v off the charger for about 30 minutes.. then move to step 2 make sure to set your 2nd stage charge rate to about 1/2 the rated capacity or no more that about 430 mha .4a would work and let it finnish charging..

While you most likely have reduced the capacity of your pack you may still get usefull life from it..

Good Luck

A10FLYR

My Feedback: (1)

OK. I had a chance to try it myself today. I had a 3S pack that read 5.6 V. I hooked it up to the 109 and it read 2C1. After a few minutes it changed to 3C1 and continued to charge as a 3S pack. I left it at .45ma for about half hour then turned it up to 2 amps to finish the charge. Everything seems OK at this point. It accepted a little over 1500 ma. Will see how it performs.

airborne1107

Just my two cents, been to lipo, back to Nimh after seeing the way it burn...on a field experiment.

My Lipo 2 cells 1500 mah about 90g

NiMh 6 cells Kan 650 about 90g, it produce higher Voltage after charge , higer amp draw capability

So instead of using one Lipo for a 10 min flight for example, I go with 2 packs of Nihd for 5 Min flight each. If your wing loading is ok, add in one cell for two to the NiMh pack to give a little more punch.

BTW, the best cells I have use so far is Sanyo AR500. If you want effciency, work on the motor loading, prop it correctly with wind condition airframe drag and stall charateristic of aircraft.

Sprink

Read this for someone else who rescued their lipos - 3 cell pack down to 0.3v accross each cell!

http://www.*************.co.uk/4um/i...?topic=13664.0

altacom

My Feedback: (3)

I've been using Li-Po batteries exclusively for over a year now and will never look back. At first I was so confused about how they needed special care etc. but now after learning to use them and make them happy, So am I. Happy that is.

At first I turned 2 of them into sausages, and on an occasion at a flying field created a fire. But in all cases that was OPERATOR ERROR. I neglelcted to check the charge rate after charging higher MAH packs.

I have a set of rules that I have established for myself and it seems to work.

1. If a motor needs 2000MAH batteries, I will make sure to have a Pack capable of 3000 MAH or better. Batteries run cooler, fly longer, and may last a long time. I set my transmitter timer to give me a good flight time and still not take the batteries into cutoff. I try to never have the pack go into cutoff.

2. After each pack comes off the charger I rotate the control knob on my ASTRO 109 all the way down. This has become a habit, and I find now I even do it on the 110 with Nicads.

3. If a Li-Po pack is rated at 3000 MAH, it can be charged at 3.0 AMP on the 109. I always set the charge rate to somewhat less than the highest. For the 3000 packs I set for 2.90 Amps Charge. Keeps the batteries cool and the extra 5 minutes or so it takes to charge is insurance.

These 3 rules have become second nature now and I no longer fear using the Li-Po batteries.

I have seen gas cans at flying fields burst after sitting in the sun for an hour. Li-PO batteries are no more dangerous - if properly handled, and a person educates themselves about them.

A10FLYR

My Feedback: (1)

I do 1 and 3 also. An electronics engineer who I fly with has the same advice.

AgCat1982

I think some people are not getting the benefits of Li-Po technology because of unwarranted fear of them. EVERY battery used in the RC field can explode and injure someone if charged improperly! As mentioned before, above, car batteries can and do explode! I have seen it happen by sparking the charge cables when boosting! The individual involved was severely burned! Everyone who has a car has a car battery! Read the instructions, follow them, and have fun!

This is my personal opinion.

Zim5

Wow, I was wondering what happened to my 2 lipo packs until I read this post. I have a kokam 2-cell 1500mah pack, and a 2-cell 340mah pack. I believe they are both ruined. The 1500mah pack only holds about 200mah. My 340mah pack is weird. It has about the same capacity as it used to, but when I have the airplane on full throttle, The rpms oscillate (muck like the pack is about empty) but if I pull the throttle back just a little bit, It stops oscillating and the pack runs about as long as it used to. I am running an axi 2208, and a 8 amp speed controller.

I thought my charger was the problem, But now I know what the problem is. I have my speed controller set on soft cut-off, and Im letting the batteries discharge too much. Is there any suggestion for using the soft cutoff- I really like it for hovering/sport flying.

altacom

My Feedback: (3)

Depending on the ESC you are using, you have to set the EPA differently.

I had a similar problem on a Castle Creations ESC, and when I set the EPA to 120% it works perfectly. On JETI controllers I have the EPA set to Zero. No explanation, but it works.