Pesky Little 1S Lipos!

[Keith Miles 2]

Following on from my initiated thread on E-Flite lipos and their cost versus their quality and being concerned about an apparent inconsistency in general, I thought that this might interest some of you, or not!

Anyway, here goes.

I'm a relative newcomer to electric flight and fly IC only outdoors and electric only indoors (the latter for obvious reasons!).

Most of my little models, fixed wing and helis, plus one quad use those little 1S lipos of 130-175mah. From an early stage their longevity seemed to be something of a lottery, new ones failing after little use, others lasting for much longer and irrespective of cost or make. I have found it very annoying especially when my little helis drop out of the air without warning albeit rarely with any damage. After much research, hearing of others experience, suggestions, shared frustrations etc. I finally got around to doing a little experimentation.

For those still reading, I won't bore you with a list of figures and, anyway, I can't be bothered to type them all out.

I took my 15 Overlander !S 175mah batteries some of which had been on storage charge since the end of last indoor season, in March, and some which had been used recently at the start of this season. Charger used was a good quality I-Charger 208B allowing adjustable charge rates, voltage and IR measuring etc.

The only consistency I found was that Internal Resistance (an often quoted means of monitoring battery health over time) rises with rising voltage, thus confirming, at least, that the laws of battery physics were being followed. So far, so good!

As for end of charge IR and voltage measurements these figures were all over the place and, similarly, bore no relation to the number of times the battery had been used nor to each other! Nope, no clear trend or relationship whatsoever!

(I should point out here that as a result of early frustrations, I started keeping a record of each use of each battery on a small piece of paper, inside a small plastic bag, with the battery. Yes, I know! Sad, isn't it).

Here's a summary: (Still with me?)

Highest charged voltages of 4.19,4.18, 4.18 were recorded on older cells used 28 times, mostly last season, and then used recently.

Newest cells (although there is a theory that, up to a point they initially improve with use), used 8 times, recorded lower charged voltages of 4.06,4.09,4.09, 4.13.

Lowest charged IR (ohms) value recorded was 0.952 after 28 cycles.

Highest IR value recorded was 1.778, again, after 28 cycles.

Both of these were also in the highest voltage group 4.19 and 4.18 respectively but note the significant difference in IR compared to the insignificant voltage difference.

Of the five cells that had been left on storage charge after 34 uses, highest voltage was 4.15 with IR of 1.090 and lowest voltage 3.9 and IR 1.294.

The two oldest cells, used 42 times and left on storage charge recorded values of 3.7v/1.667ohms and 3.9volts/1.034ohms.

Oh, and having otherwise used a charge rate of 200ma for this test, one of the newest cells (8 uses) refused to accept a charge from 3.8v until the rate was adjusted down to 100ma.

Conclusion?

So (for those still here i.e. fellow anoraks), I can find no direct or consistent relationship between age, storage, voltage, IR, or use as far as these little blighters are concerned and no obvious or simple means of monitoring their state over time despite suggestions to the contrary that I've read in the past, albeit concerning lipos in general.

Secondly, it has always been my understanding that unless lipos are clearly marked otherwise, they should be charged at 1C. With the one exception mentioned, I used 200ma in these tests due to charger limitations.However, in the past, I have used one of those cheap four port chargers with LED indication only and a fixed 300ma charge rate. I am wondering if this might be part of the problem in addition to possible, probable or actual inconsistencies in manufacturing tolerances.As with other lipos brand names and cost seems to bear little or no relation to quality.

To that end, I see that a more sophisticated four port charger is now available (I wonder why?)with four types of 1S socket per port, infinitely variable charge current, and digital display showing charge current, charge voltage and charge state. They seem to be exactly the same charger but with different names and in two different colours i.e.Hitec/Sky RC and either red or blue. Cost is about 40 quid or so and Christmas is coming.....

Thanks to those still reading for staying with me and I hope that you found it both informative and worthwhile! I did!

[Tim A]

Due to a winter of very little flying due to our field being flooded to a depth of 15 feet I placed my lipos in storage charge, 2 of them, both no older than 6 months and one unused have failed to charge on 2 out of 4 cells.

After a discussion at the club the consensus is that storage charge is a waste of time as others have experienced similar results and it seems that a charge of 90% capacity is better.

Not scientific I know but having seen others comment on this forum and elsewhere to having similar experiences I am wondering if they are right.

It is annoying when you do what is accepted practice only to find that it might only be wrong and expensive.

[Denis Watkins]

For indoor micros I keep approximately 10 working 1s lipos ready for winter flying indoor

And for fear of them going flat during the 6 month lay off, they are put away charged.

As each season approaches, these are taken out to be checked and routinely the are 3 duds.

The numbers required are then ordered to make up the flying stock.

There is no rhyme nor reason, make or supplier for which lipos go dud.

This just becomes a necessary annoying expense each season

[Paul Marsh]

I found that most of my micro 1s batteries have all failed, probably only last one season, where some of my 3s Lipos are still ok after 10 years. And leave them fully charged all the time and don't find any problems with them failing because of being charged.

Some have puffed up, either because of age or being cooked in an edf, one 4s 4000mah is had failed and the other is just ok in a foam P-51 that doesn't take much current.

The Eflite 2s ones seem to last much longer, maybe because the 1s are working at the limit and their charger is charging more than 1c, which doesn't help.

[Keith Miles 2]

Hello, anoraks!

Some more info for you.

I have just noted that all of my E-Flite 1s 150mah cells, each supplied with a model have a stated max. charge rate of 3C i.e. 450ma.

The supplied E-Flite chargers and a later simple 4-port one purchased are both 300mah charge rated so, in theory, neither type of charger should ever have overcharged the E-Flite 3C cells.

I now note that every single one of those supplied E-Flite batteries failed after less than 10 flights!

In my view, this is not simply annoying, it is totally unacceptable, especially for batteries possibly costing £6.00 each to replace (I just checked the price of the E-Flite one on a U.K. model shop site).

Taking into account the relatively good quality of the models flown (Blade MSR/MSRX/NanoCP helis plus Hobbyzone Champ and Spacewalker fixed wing) and their individual cost, averaging around £80 or so each, it seems unfathomable to me that these wonderful and technologically advanced little models are let down (quite literally) by, seemingly, a technologically flawed, overpriced, unreliable and short lived power source!

Furthermore, such unreliability, whatever the cost of the battery, is also likely to lead directly to crash damage to the model and the expense of repair, or to a write -off, especially to a CP Nano in the hands of a relative beginner (guess who?).

I've said this elsewhere, but I cannot understand why a company like Horizon Hobby, at least, with an otherwise good, even excellent reputation (and a virtual monopoly in this area), would not want to do something about what seems to be a very common and significant issue. Such failure seems to me to be very short sighted.

If there is an insurmountable and universal manufacturing problem with this particular size of lipo battery, Horizon Hobby could, at the very least, stop charging a ridiculously high price for an item that is either no better, or even much worse, than the competition rather than leading us to assume otherwise.

As Denis points out, this is indeed an annoying seasonal expense. Not just seasonal, however because I would like to practice my little heli flying at home throughout the year without it working out more expensive than running a fleet of IC powered outdoor models!

So, here goes, looks like I'm about to order another batch of Overlanders so we'll see how they perform.

Grrrr!

[John Robertson 3]

I've had cracking results from 6 Charsoon 250maH 30/60C cells from Banggood at about £3.80 each. I run them in a little UMX Radian. I bought original eFlight 250 maH 25C cells, and also tried a 45C version. Of the 5 x eFlight cells, only one (a 25C) has lasted the season. The eFlight cells weighed 5 g (L 44.1mm W 11.01mm D 6mm) and the 250 maH ones 7g (L 53.7mm W 11.55mm D &mm). The 250maH cells gave the motor MUCH more punch and the plane would climb at a VERY steep angle, which it would not do with the eFlight versions. If not using the full 60C kick I can easily get 15 minute flights, with a bit of wind assistance, whereas the others gave me concern after half that time. The Charsoon cells are still with me, apart from I which was physically damage in the connector are by me and my clumsiness.

[Geoff S]

I just buy 200mAh 1S LiPos for my indoor heli (V911) from Banggood. I don't think I bought any last winter but the ones I have lacked capacity last week so I've ordered 10 for just a few pence over £20 (£2 each) and I expect they'll last the next winter too.

Indoor models are so light and are obviously flown low and close in that any battery failure rarely has serious consequence. Mid airs are not unknown and models are usually flyable immediately afterwards.

I've never actually bought any EFlite LiPos mostly because I was staggered at the prices ... and the vast majority of my flying these days in or or outdoors is electric so I but all sizes up to 6S.

Geoff

[MattyB]

Not sure why, but the small 1S indoor packs all seem to be impossible to keep healthy for any significant length of time. I am a religious storage charger and it works great for all my larger packs, but anything of 300mah or less seems to go the way of the dodo sooner rather than later. Maybe it's harder to make these physically smaller packs to the same levels of quality?

[Keith Miles 2]

MattyB. My conclusions exactly. I have tried several makes before settling on Overlander and mainly because they have tended to be more readily available rather than noticeably more reliable.

Referring back to my earlier posts, I can now report that I took all of the aforementioned Overlander IS/175s indoor flying last night. Immediately before leaving home, all were put on my fancy charger and, where necessary, given a 100ma top up charge. Only two failed to charge to 4.06v or more and were set aside.

As a control, I used my MSRX heli, which usually gives 4 minutes flight on a new battery plus a healthy 1-2 mins margin.

Of the 13 batteries flown, all but 3 failed in less than 4 minutes, some lasting only 20-30 seconds!

Although most had been used from 28- 40 times, 4 had only been used 8 times, so even a relatively new one had failed!

I have also now proved, that measuring IR values is pretty pointless as these can vary significantly between batteries whether old or new and irrespective of voltage, and can even vary on ONE battery simply by disconnecting it and then measuring the IR again! Try it yourself!

Measuring voltage or the end of charge voltage is also no guide to battery health, as I proved last night! In fact, 3 with the highest measured voltages were not the longest lasting!

As with all batteries, they can only be accurately tested and measured for health when on load and in this case, the only practical means of doing that is to fly ‘em and try ‘em!

Just tried, for the umpteenth time, to order some little Nano Techs from Hobby King, Hong Kong warehouse only and no UK delivery option, they say! Useless!

Best price found, so far, is still Wheelspin Models for 6-pack of the Overlanders at under13 quid and from where I bought my last lot.

So, we’ll see how long these last!

[Keith Miles 2]

Posted by Geoff Sleath on 18/11/2017 22:27:

I've never actually bought any EFlite LiPos mostly because I was staggered at the prices ... and the vast majority of my flying these days in or or outdoors is electric so I but all sizes up to 6S.

Geoff

Indeed, I was also staggered!

Up to £5.99 for ONE tiny 3.7v 150mah battery!

I would want a minimum operational hours warranty for that kind of money,

High price and a seemingly comparatively very short life. I’m amazed that they sell any at all!

[Keith Miles 2]

Oops, apologies! Those Overlanders are just over 16 quid at Wheelspin not 13 as I said earlier! My mistake! Still the lowest price I’ve found, however.

Oh, and the cells that seem to prematurely fail in an MSRX (and I have two) can then be absolutely fine in the MSR (I have two of those as well).

Ask me how I know!

Almost certainly a matter of differing current demands of the two models and of on load voltage drop at higher currents triggering the cut-off sooner.

Another reason why it’s a pity that they no longer make the MSR!

Fini.

[Simon Chaddock]

I think Keith has identified where some of the problem lies. The actual discharge rate plays a significant part in the life of a LiPo.

If you can keep the maximum rate of discharge to no more than 10C,with a flight average at half that (and never discharge below 40% capacity!) any LiPo is likely to have a long useful life..

The problem is of course the tiny LiPo in mini quads have to be worked a good bit harder than that to fly at all!

No LiPo battery manufacturer states what the effect is on the performance and life of the battery if you actually use the maximum claimed discharge rate. .

[MattyB]

Posted by Simon Chaddock on 21/11/2017 10:54:30:

I think Keith has identified where some of the problem lies. The actual discharge rate plays a significant part in the life of a LiPo.

If you can keep the maximum rate of discharge to no more than 10C,with a flight average at half that (and never discharge below 40% capacity!) any LiPo is likely to have a long useful life..

The problem is of course the tiny LiPo in mini quads have to be worked a good bit harder than that to fly at all!

Very good point. I have never put a wattmeter on any of my micro/indoor models (mainly cos I don't have any connectors for that and them being RTF jobs had never thought it was necessary), but I am sure you are right that we are pulling much higher currents out of them relative to their size than in larger sport models.

[PatMc]

I've noticed that some of the indoor helis & rtf fixed wing models either don't have any LVC or it's at such a low level that it's not apparent until the model simply can't maintain flight.
Perhaps this is a significant factor in the short life of many low capacity 1s lipos.

[MattyB]

So in summary it looks like a case of "failure by design"!

[onetenor]

In the car industry it's known as PLANNED OBSOLESENCE

[brokenenglish]

Gentlemen, I don’t want to start a conjectural debate, but I need some knowledgeable advice and guidance.

I’ve been using a large capacity (1S 5.0 Ah) hard case RC car battery for a bench running spark ignition circuit. For several years now I’ve been charging this battery at 1C (5 A) and it has become very swollen.

A couple of days ago, I had a very lucky escape. I was charging the battery as usual, and it started emitting crackling/sizzling/spitting sounds. I immediately stopped charging, obviously, and very gingerly disconnected the battery and took it outdoors. It was very hot !

Obviously, that battery can no longer be used, so I’ve ordered a replacement (1S 6.4 Ah) (with a Lipo bag!!!).

I suspect that the problem with the old battery may be that, for the first 2 or 3 years, I used to leave it permanently fully charged, which leads to my simple question:

What charging current should I use to charge this new battery? And also what discharge current, for "storage" charging.

Note that I’m never in a hurry for charging, and I wouldn’t be at all bothered by a low current / long period charge.

Expert opinions invited please!!!

[Denis Watkins]

1C charge for the lipo is fine BE

Yours lasted a long time, and I doubt you did anything wrong

The cell demonstrated the type of failure that can occur

Your normal routine does seem adequate

Edited By Denis Watkins on 24/11/2017 08:53:23

[Simon Chaddock]

brokenenglish

I would avoid leaving any LiPo for long periods (months) fully charged. At best it reduces the available capacity a bit, at worst it can cause what happened! Yours is a big cell with a lot of energy in it.

Unlike other cells LiPo do not like 'low slow' charging. The important factor is the cell voltage must never be allowed to exceed 4.2V. This requires the charger must absolutely stop charging as soon as that voltage is reached.

My bench test LiPo is used 'as required' and it is only charged when I think I have used at least half the capacity and I want to use it some more, otherwise I leave it alone. It is a retired (slightly puffed) flight battery and is now 3 years old.

[MattyB]

Posted by brokenenglish on 24/11/2017 08:36:09:

...I suspect that the problem with the old battery may be that, for the first 2 or 3 years, I used to leave it permanently fully charged, which leads to my simple question:

What charging current should I use to charge this new battery? And also what discharge current, for "storage" charging.

Note that I’m never in a hurry for charging, and I wouldn’t be at all bothered by a low current / long period charge.

Expert opinions invited please!!!

Yes, leaving a lipo fully charged for extended periods will reduce the capacity and effective C rating (ability to deliver high current) and increase internal resistance. This is due to chemical processes within the cell, the main one being dendrite growth on the anode which can ultimately lead to an internal short (probably what happened in your case). The best advice would be to use a 2S LiFe battery instead - they are much more resilient to be held at elevated SOC for long periods, and should be fine with your ignition circuit; you don't hve to charge them to their full voltage anyway if it's just a bench pack.

Re: charge rates, 1-2C is absolutely fine (most modern lipos are rated to 4-5C, though I never bother to charge them that hard as I have a meaty parallel charging setup instead). Discharge to storage is more likely to be defined on the maximum watts your charger can safely dissipate as heat - normally they are limited to 1-1.5A on a 3S pack, you might get a smidge more at the lower voltage of a 1S.

Edited By MattyB on 24/11/2017 09:36:22

Edited By MattyB on 24/11/2017 09:38:46

[brokenenglish]

OK, Thanks for all the answers. Just about what I hoped for.

Rereading all this, it occurs to me that replacing the battery every three years or so would obviously be a wise policy. Plus the fact that I expect to get better (safer) results now that I've realised the importance of a storage charge.

I'm relieved to learn that I wasn't doing anything ridiculous... but it's a bit disturbing to learn that you can perpetrate a major disaster (house fire) without doing anything ridiculous!

Finally, Thank you all!