Lipo experiences. Please post your personal findings!

[recumpence]

I know, I know, many people will think "Oh my gosh, another Lipo thread? I thought this has all been hashed out!"

The reason for this thread (the mods can move it to a different section if they deem necessary) is to post our personal experiences with Lipo chemistry. I felt the need to start this thread based on some misconceptions floating around lately. So, with that being said, here are my personal findings..........

I have been running Lipo in my RC models since the beginning. I remember the first pack I had was rated at 2C. That pack lasted hundreds of cycles before it died. When it died, it reduced its C rating (it had less power and more voltage drop under load) and its total AH capacity. However, it died from pulling too many Cs through it. It ran totally perfect until I went with a larger motor in the heli it was in. Next I went to 10C packs. These lasted a very long time (hundreds of recharges)-(this is a long time in hard RC use). These packs finally went bad from overdischarging them. I was taking them down to 10% state of charge. :|

After that, I met Brian from Tanic packs. He and I worked out a deal for a huge number of cells. These were all 10C as well. I made many packs and had mixed success. These were still very old technology packs (maybe 7 years ago?) that sat for a long time before use.

At this point, I began getting a bad feeling about Lipo, though I still ran them because they were the lightest option available. Then disaster struck......... I had a tiny 2S-320 mah pack explode in my house when my charger failed. My wife put the fire out and I thought that was it for me with Lipo. But, I stuck with it and was determined to figure out what went wrong and how to fix it.

A number of people told me the new generation cells and chargers are light years better than the old crap I was running. So, I upgraded my charger and my packs and BINGO, they were right! All charging issues went away. Also, my packs lasted nearly forever. In fact, I was selling packs to friends when new technology became available because they were lasting so long.

Fast forward to 3 years ago when I built my recumbent. That pack is still old technology cells (10C cells that sat in storage for a couple years). I have over 1,100 miles on it with no signs of degradation.

Here is the state of Lipo right now.........

#1 The cells are way better than they were even two years ago.

#2 The chargers are light years better as well.

#3 If used correctly, Lipos last a very long time.

#4 The safety issues with Lipo are roughly the same as other chemistries these days.

What is correct use? That is in the Lipo use thread. But, I will put it this way------ Stay under the C limit and keep over 25% state of charge in the pack and it will last 1,000 recharges before any degradation is noticed. To illustrate that point, I have a lipo (V1 5C pack) in my RC heli transmitter from 5 years ago that is still running like new. Why? Because it is never drained below 25% and is never run past its C limit.

All chemistries have their degradation issues and their safety issues. At this point, Lipo is on-par with pretty much all other chemistries in regards to safety, number of recharge cycles, and overall ease of use (if proper charging is maintained). Heck, I have had Nicad packs burn up, I have had Alcaline cells burn up, and I have seen A123 packs burn vehicles to the ground. They all need to be treated with respect. In fact, Lipo packs are actually more stable than others in regard to staying in balance. If they are kept above 20% state of charge, I have NEVER had one (and I have run over 100 packs) go out of ballance beyond .1 volts.

That is my take on it..........

I know others on this forum have had bad experiences with Lipo. But, I would hazard a guess that something caused the problems wether it was overdischarging, or some other outside force at work. Of course, anything can happen. I have also gotten a bad pack from Hobby King. So, there are various factors involved.

Lastly, it seems as though Lipo problems are posted readily on this forum, while problems with other chemistries are not mentioned. But, I hear about them through PMs and emails. There seems to be an aversion to mentioning problems with the "Safe" chemistries. But, I have seen my share of problems with A123, Headway, Ping (lots of Ping problems) and others and I have had my own problems with various chemistries, including Lipo.

Matt

 

[Arlo1]

#1 Lots of power more AH then rated for the turnigys
#2 Charged 3 cells to 4.36volt acidently and never caught fire!
#3 Distcharged 3 cells to <1 volt and recharged and still using my first 10ah of lipo!!!
After abusing them like that I only get 6-8 ah out of a 10ah pack but they are far from destroyed!
I LOVE LIPO!

 

[spinningmagnets]

Make sure you have a working Low Voltage Cutoff (LVC) and also some type of standalone low voltage warning system (flashing-light/buzzer). To avoid "puffing" them.

I am now charging with the Lilo setting (4.10V max) edit: at 4.10V max, I'm told there are fewer bulk-charging issues with cell balance and pack health. I only want to balance-charge each cell on the weekends when I have plenty of time to keep an eye on them. 9 out of 10 charges are a simple bulk-charge to 4.10V.

I am stopping use when the pack gets down to 3.5V per cell (instead of 3.3V), to extend pack life rather than get a little more distance from the pack. I will report how that is working out after I have some significant miles on this newest pack.

 

[Whiplash]

I don't have nearly as much info as you others here, but I can say, I LOVE Lipo and I would NEVER use anything else! I bought a used pack from a member here that had a 150-200 cycles on it, and I am still going strong with them now with about 1000 miles on the bike! Its a Hub motor, and not real powerful, (does about 37MPH no pedaling) but hey I love em! I couldn't imagine running a big heavy turd of a battery after having these!

 

[Ricky_nz]

I've been running 2 packs made out of turinigy 5Ah packs. both 7S2P paralleled using balance taps.
I used them in series of faster bikes and in parallel or single for slow bikes.
Ie 14s2p or 7s4p or 7s2p. They stayed in balance well, charged every second day on average (used down to 50% at that point).
Sometimes I take them down to 90% discharge although not very often.
In most cases I used both packs.

I had one incident where I was using one of my 7s2p packs and I took it too low (worst cell approx 2.3V, Charged it back up (100mA charge until over 3V then hit it with 4.2A) and seemed good but a couple of months later one of the cells in the 2.3V paralleled pair puffed up. The balance wasn't too bad up till that point. ( I check with a cellmon 8 regularly).
I replaced the cell and everything is back to normal. The pack is now >1 year old and the balance isn't as good as new but it is stable at 40 - 50mV between the extreme cells, most are much closer).
My RC charger accucell 8 150W is too slow to balance it and I haven't bothered messing with it as it has plenty of range for what I need and charging to 4.1V max allows the 50mV balance difference to not cause any issues when bulk charging.

I estimate I have done over 1400Kms on these packs and they are still going well.

The cells are 20C and my bikes pull 30 - 40A max from them so they are not too stressed.

 

[neptronix]

I have been running on 5AH 10S zippy lipo packs with an iCharger 1010b+.

They seem to stay in balance up until 3.6v; after that is when massive voltage deviation happens in the cells & the voltage drop per mAh gets sharp and rapid.

So i charge to 4.15v and discharge to 3.6v.
I figure it is good for the battery's lifespan to charge up to ~80% anyways. By allowing that headroom, i avoid having to be worried about disbalance so much also.

Also another thing i like about lipo is that it has tons of internal resistance to spare. As it ages, it will sag some, but not like a lifepo4. I think if you have a large pack and thus draw a low C rating out of it, you may get 1000 cycles or more until they are completely kaputz.

 

[Andje]

I have just hopped on the Lipo wagon with my first build which is almost finished, so I can only report so far on my purchase from HK and the wiring experience. That said, I benefit from years of people on here testing the stuff first and the trial and error that has already been done, and I tried to do it pretty well the first time.
So I built a 100v 15ah pack from Turnigy 5Ah 20C Lipo:
http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=9176
At the time I started ordering the Hyperion that can do 12s wasn't out yet, so I didn't consider it as a charging solution, although I probably would have just gone with it as a simple solution if it had been available. Instead I decided to balance with 4 battery medics, also from hobbyking. So for 12 batteries, some wire, connectors, battery medics, and Meanwell PSU's for charging, that came to about 850$ with shipping to Ontario, Canada.
I just mostly finished the pack last night, and charged and balanced it for the first time. I can say that although making a 24s3p pack was scary only because of the power involved, doing it was no harder then making a much smaller pack, just longer. Everything worked fine though, and I am well pleased with the final product. I am "bulk charging" with two meanwell s-350-48 in series to make 107v at around 8 amps; this charged the pack in about 40 mins from 93v to 100v last night. Each 3p section has paralleled balancing taps and the Battery medics can be plugged in and balancing at the same time as the MW. All of the balancing taps will eventually be run out of one large 36 prong connector so that i dont have to plug and unplug jst's and so that the entire balancing/charging solution will be two plugs.
I think I learnt a few things when making it even with the months of research.
-when designing your pack remember to consider the balance wires coming out; i wouldn't want to squish those too hard, so placing batts end to end I wouldn't want to stack them as load bearing
-jst-xh connectors are a total bitch to crimp and solder yourself; also, use the wire AWG they are rated for, smaller wire is the bane of crimping these. Buy extensions and cut them. I couldn't because they were out of stock
-epoxy or hot glue your jst female connectors; the crimps will hold the wires, but the metal housing itself tends to get tugged out of the plastic housing resulting in cells not getting balanced. EPOXY.
-precharge resistors would be fine too, but i really have to admit that i like my westinghouse 100 amp switch a heck of a lot. Sure it's huge and ridiculous, but it is also awesome.
http://cgi.ebay.ca/ws/eBayISAPI.dll?ViewItem&item=230587711995&ssPageName=ADME:L:COSI:CA:1123
-i also really like the ANL fuses; at my wattage they should actually work as fuses, and they really work well for paralleling the positive/negative wires even if i dont get that much real protection from them

I am going to track the stats of the pack once i start using it, and it's designed for a 3 year commute back and forth to the local college, so it will rack up the cycles daily. My application in particular would have been impossible with any other chemistry; my batteries are all in a back pack, and I wanted that voltage and needed that ah, but cannot really fit any extra weight. The idea that lipo will just get better is exhilarating. Ill post back here in a year with stats.

 

[liveforphysics]

Remember, if you use Lipo, or even just see a picture of Lipo online, your house and friends and children will explode into flames. Don't have children? It creates children for you and then bursts them into flames.

 

[geetarboy]

Hey Matt, Good topic! I have been wondering how long my lipos are going to last. I have bought 20 - 6s 5000mah packs in the last several monthes. 2 of those failed shortly after I started using them because of defects and 1 got dropped & killed a cell, and 1 got hooked up wrong and discharged too fast and killed a cell. 4 of them are 15c packs and they are all puffed, so I don't expect them to last as long. However, I rarely discharge below 80% and when I have, they stay above 3.3v per cell. I always balance chage each pack singlely and they stay within .05v or less. So, it seems like you can get alot more life than advertized out of lipo. Thats Good news - Mark

 

[snellemin]

I've been an A123 user for years with my RC hobby. And Lipo user as of late. As mentioned before, take care of the packs and they will last a very long time. Abuse them and lifecycle shortens. If the batteries survive in my high amp RC setups, then they will last a long time in my low amperage bike. I've vented A123's before. I've overheated them to 198F from drawing max amperage in RC dragracing. And that overheated pack still lasted 1 more year, before it finally gave out. I'm using the same 5000mah 40C Acepow hardcase lipos in my RC's and bike. I only use about 3000mah one way to work, running 14S lipo with my cheapy Ebike kit. So the packs never see abuse and will last a long time. Doing burnouts with my RC for 30 seconds or more, pulls 100-120A continuous. Peak is in the 190A range. I have vids of battery test burnouts on youtube. My bike peaks nearly 60 amps and pulls about 15 or so Amps continuous. Nowhere near what they see in my RC toys. Another nice thing about current lipos, are their ability to take 5C or more charge rates. I've been charging A123's @ 20A with no adverse effects. Charing my lipo's @ 40A. Notice I had waiting on batteries to charge.

 

[Arlo1]

I have used 8 packs of 6s 20c 5000 mah for a year now and done everything you are not suposed to!!!
I have charged a couple cells to 4.4 volts and discharged 3 cells < 1 volt!!!
The still pull strong and I still get just under 10 AH out of them. I just pulled >280 amps continious out of them as I was power wheelieing leaning over the handlebars!
I love them so much I just orderd 12 packs of 4s 5000 mah 20c for $21 a pack Thats 21cents a watthour!!!

 

[grindz145]

Stop doing that Arlo, I've been waiting to order them until they're in stock, now I'm going to have to pre-order them... :lol:

LOVE lipo

 

[Thud]

LiPo is bad mmkay'

Addictive & the more ou have the more you want.....then you want faster chargers & heavyer wire...& faster chargers still again....where will it end?

 

[Doctorbass]

What i have found is that making a really strong case around them help keeping the IR as low as possible and avoid make them puffing.

I am using 24s 3p in 12 packs of 6s 5000mAh and they are in 3 row by 4 lengh.

I fitted them realy stiff in a aluminum box opened on the top for the conections.

What i did to choose the right case dimensions is to measure the dimensions of each 6s pack when they are EMPTY

Than i have put them in the case.. they fitted really stiff!

and than than i charged them.

The battery box became really hard!!! but never deformed (it's made with 1/8" thick aluminum all welded on each edged of the box)

I tested the internal resistance of the pack when are in and also out of the box. The internal resistance (always measured at 50% soc) varied by 20% !!.. so the IR was 20% lower when the battery was in the realy stiff case

This is a huge difference and i'm hapy with the result!

So when desining a lipo box... ensure that the lipo are empty when taking the measurement and ensure the pack fit already stiff when puting them i the box.

When they charge they will be compressed and that pressure will help keeping the internal resistance as low as possible :wink:


An anecdote: I also observed that just by knoking on the box with my hand, i can know the aproximative SOC fo the pack just with the sound it make!.. when cells are nearly empty, the box sound is more deep frequency.. like "TOC....." and when fully charged it's lile "TIC.."


Doc

 

[nicobie]

I have had way more trouble with my Ping packs than I've had with my lipos. I guess the ping packs are ok but they have to be ran at LESS than 1.5C. My 20ah Ping couldn't handle running 30a peaks. Whereas my lipo can handle more amps than my controller and motor can.

 

[kfong]

That's a unique way of keeping the IR low Doc. I wonder how much pressure the seems can take? I"ll have to try that on my rc stuff. Keep us posted on the long term effects.

What i have found is that making a really strong case around them help keeping the IR as low as possible and avoid make them puffing.

I am using 24s 3p in 12 packs of 6s 5000mAh and they are in 3 row by 4 lengh.

I fitted them realy stiff in a aluminum box opened on the top for the conections.

What i did to choose the right case dimensions is to measure the dimensions of each 6s pack when they are EMPTY

Than i have put them in the case.. they fitted really stiff!

and than than i charged them.

The battery box became really hard!!! but never deformed (it's made with 1/8" thick aluminum all welded on each edged of the box)

I tested the internal resistance of the pack when are in and also out of the box. The internal resistance (always measured at 50% soc) varied by 20% !!.. so the IR was 20% lower when the battery was in the realy stiff case

This is a huge difference and i'm hapy with the result!

So when desining a lipo box... ensure that the lipo are empty when taking the measurement and ensure the pack fit already stiff when puting them i the box.

When they charge they will be compressed and that pressure will help keeping the internal resistance as low as possible :wink:


An anecdote: I also observed that just by knoking on the box with my hand, i can know the aproximative SOC fo the pack just with the sound it make!.. when cells are nearly empty, the box sound is more deep frequency.. like "TOC....." and when fully charged it's lile "TIC.."


Doc

 

[nieles]

doctorbass,

did you put pressure on both sides of the pack? or did you only put pressure on the thickness of the cells (the direction the cells are stacked)


arlo,

where did you find the 4s 5000mah packs for 21 dollar? hobbyking?

 

[neptronix]

drbass that is hilarious.. BUT.. i don't know about your advice on making sure the cells are tight.

The extra room for the cells to puff is good for safety i think. If they cannot puff to the sides, they will puff upwards, downwards, which ever way they can go. if they have no motion, it seems like they will just explode.. much like how cylindrical cells will just violently blow their tops !

Call me a naturalist but i think lipo should be allowed to puff some. It's a warning sign that something is wrong, and if you remove that warning sign, if you have a failure it's going to be a big surprise

Also as they get older and the IR goes up.. they will surely puff more.. and more..

 

[nieles]

drbass that is hilarious.. BUT.. i don't know about your advice on making sure the cells are tight.

The extra room for the cells to puff is good for safety i think. If they cannot puff to the sides, they will puff upwards, downwards, which ever way they can go. if they have no motion, it seems like they will just explode.. much like how cylindrical cells will just violently blow their tops !

Call me a naturalist but i think lipo should be allowed to puff some. It's a warning sign that something is wrong, and if you remove that warning sign, if you have a failure it's going to be a big surprise

Also as they get older and the IR goes up.. they will surely puff more.. and more..

i always wrap my lipos in ducktape, to make sure the packs stay compressed.

but you are right, if something goes wrong.. it will go violently.

 

[recumpence]

This is something we used to do with our SLAs in the car audio world. It does work to keep the IR low.

Oh, if the box is strong and you have a pack problem, the packs will not explode, they will "Vent". So, as long as there is room above the packs (where the wiring is), they will vent upward and not explode.

Matt

 

[bobc]

That's important info from doctorbass - I'd been wondering what sort of box to put the lipos in (there will be a lot in the landspeed record car) & he reckons having them under compression in a rigid housing 1) stops the swelling and 2) actually reduces series resistance.
I'd instinctively erred towards allowing them to swell, but if this is right I should squeeze them tight! Has anybody else done this? Any horror stories? (1st hand obviously.....)

 

[Ypedal]

linked the wrong video a moment ago.. i made a video but have not loaded to YT yet.

pictues will do :



and :


Wood clamps to compress the packs, and secure them with filament tape that will not strech keeping the cells tight.

 

[Doctorbass]

drbass that is hilarious.. BUT.. i don't know about your advice on making sure the cells are tight.

The extra room for the cells to puff is good for safety i think. If they cannot puff to the sides, they will puff upwards, downwards, which ever way they can go. if they have no motion, it seems like they will just explode.. much like how cylindrical cells will just violently blow their tops !

Call me a naturalist but i think lipo should be allowed to puff some. It's a warning sign that something is wrong, and if you remove that warning sign, if you have a failure it's going to be a big surprise

Also as they get older and the IR goes up.. they will surely puff more.. and more..

I still think compressing cells pouch is better than to let them to puff.

What make cells to go in flames is that when they puff.. they have deformation..... the electrode inside have also a deformation.. and THAT CAUSE SHORT OF THE CELL... THAT CAUSE IT TO FLAME.

preventing any deformation of the cells is preventing them to short.

Thats's also what the electric car industry believe. I read some document about that and that's why i did that.

I also added some 6mil FR4 sheed between each pack and rubber on the last layer between the pack and the aluminum box to protect against mechanical vivration and keep the pack in place.

Doc

 

[Doctorbass]

doctorbass,

did you put pressure on both sides of the pack? or did you only put pressure on the thickness of the cells (the direction the cells are stacked)


arlo,

where did you find the 4s 5000mah packs for 21 dollar? hobbyking?

I compressd both sides.. there is only teh top of the pack that would allow a venting.

Doc

 

[kfong]

Will the compression process actually prevent a cell from puffing? Someone should test this out by closing off the cell under compression, but allow the top to go off. Overcharge and see what happens. Will the cell actually be better off or explode. Will it vent in a safe manner. Good to know rather than speculating. How good are the actual seals, overtime will the seems blow out due to the expansion and compression process. It still only a foil baggie, what is the burst pressure of such thin foils? Please do all this in a safe manner, since we are talking of possible compressed explosion? If it only vents with out fire then that would be good to know. If the compression process doesn't allow the chemistry to breakdown. Maybe venting is all that take place, but if it goes off in a spectacular fashion, I would worry about where the flames go. Sitting next to a torch is going to likely hurt. If we are increasing the risks due to this then losing a few cells due to puffing is perhaps a more cautious approach.