What's up with my Lipos?

[GrumpyGnome]

My little ducted fans give me 4 mins max....

 

 

Edited May 25, 2023 by GrumpyGnome

[GrumpyGnome]

I set my timer to 6 mins on most of my planes (except petrol); typical flight times are about 8 mins as the timer slows down at low throttle 🙂 

[paul devereux]

2 minutes ago, GrumpyGnome said:

My little ducted fans give me 4 mins max....

 

 

Is that typical? I had no idea that electric planes had such short flights. My only previous experience has been with a R/E soarer, where power was only needed to gain a bit of height, the  whole point of the flight after that was finding thermals. The downside of that of course is just drifting about is a bit boring- well, quite a bit boring after a while.

[GrumpyGnome]

Not atypical - the edfs deplete packs VERY quickly.  And you do tend to have the throttle high 'cos they're supposed to fly like jets 🙂

[MattyB]

36 minutes ago, paul devereux said:

Thanks to everyone who responded. Sub-10 mins doesn't give much flight time per battery does it?  I'm a bit surprised it is so short. Though obviously worth it to get more longevity from the batteries. I didn't realise I should have aimed to keep a minimum charge either, I thought it was better to drain them and then recharge like the Tx battery.

 

There is lots of good info out there to read up on - an hour or so invested now will save you a lot of money in knackered packs over a lifetime...

 

From the Battery Univeristy site...

• How do lithium batteries work
• How does rising IR affect performance
• What causes Li ion packs to die
• How to prolong lithium based batteries
• How to store batteries

 

...and of course there is a whole e-flight for beginners section of this very forum with sticky threads on motors, ESCs, batteries etc that are all useful resources.

 

Edited May 25, 2023 by MattyB

[paul devereux]

8 minutes ago, GrumpyGnome said:

I set my timer to 6 mins on most of my planes (except petrol); typical flight times are about 8 mins as the timer slows down at low throttle 🙂 

I can see now setting my timer on 13 minutes was a tad optimistic!

[Simon Chaddock]

paul

Flight duration comes down to the proportion of the battery weight to that of the rest of the plane and electric batteries are relatively heavy compared to a liquid fuel.

Furthermore just putting in a bigger battery makes the plane heavier so it has to fly a bit faster and thus needs more power. Bigger batteries become a case of diminishing returns. The extra weight is also likely to make the plane harder to control and it will crash that bit harder too. It has to be a compromise.

Less 'sporty' planes with more efficient aerodynamics, like a powered glider, can usually fly for quite a bit longer without using thermals.

 

I have some home built planes that can get close to an hour at low power on all the time but it too becomes a bit like just 'cruising' aimlessly about. 🙂 

[MattyB]

15 minutes ago, paul devereux said:

I can see now setting my timer on 13 minutes was a tad optimistic!

 

Yup. The simple rule with electric flight is don't guess or assume anything, otherwise you may end up expensive magic smoke and puffed packs, or (in the absolute worst case) a major house fire. Modern electric flight is very safe once you know the basics, but it can bite back if you try and operate beyond your level of knowledge.

 

Buy a wattmeter, use it, learn to do some basic calculations to understand your powertrain (if you don't like doing maths there are tools such as eCalc that will help), assume all battery C ratings are 100% over labeled, allow at least 20% headroom on your ESCs, and (most improtantly) treat your batteries with care. If you don't understand all of those things yet that is fine, but don't try and adjust a known powertrain or come up with a new one until you 've done the reading or had your questions answered by someone with expereince (lost of the members here rate George at 4-Max for the support he can provide).

 

Edited May 25, 2023 by MattyB

[leccyflyer]

13 minutes ago, paul devereux said:

I can see now setting my timer on 13 minutes was a tad optimistic!

I was trying to be diplomatic. 🙂

 

As  I said earlier, on a 2200mah 3s1p pack I'd typically have a 7 minute flight on my less thirsty aeroplanes. My timer is usually set for five minutes for my 1100mm span funfighters which use that size of pack. In the winter, I'll usually lower that by a minute, to be on the safe side.

 

[leccyflyer]

17 minutes ago, Simon Chaddock said:

paul

Flight duration comes down to the proportion of the battery weight to that of the rest of the plane and electric batteries are relatively heavy compared to a liquid fuel.

Furthermore just putting in a bigger battery makes the plane heavier so it has to fly a bit faster and thus needs more power. Bigger batteries become a case of diminishing returns. The extra weight is also likely to make the plane harder to control and it will crash that bit harder too. It has to be a compromise.

Less 'sporty' planes with more efficient aerodynamics, like a powered glider, can usually fly for quite a bit longer without using thermals.

 

I have some home built planes that can get close to an hour at low power on all the time but it too becomes a bit like just 'cruising' aimlessly about. 🙂 

Good points all.

Back in the day, our club had a Longest Day event, where we aimed to keep at least one model in the air for the whole duration of out flying day, by flying in relays. My GWS Tiger Moth was equipped with one of those new fangled Li=Ion packs - 700mah IIRC and acted as a backstop, with the longest flight logged at 59 minutes just doing gentle circuits.

Edited May 25, 2023 by leccyflyer

[Nigel R]

Excellent advice given above. 

 

I would only add, the imax b6 you see on ebay are almost certainly copies of unknown quality. 

 

Real thing will be nearer £50.

 

https://www.unmannedtechshop.co.uk/product/skyrc-imax-b6ac-v2-charger/

 

 

 

[paul devereux]

1 hour ago, Nigel R said:

Excellent advice given above. 

 

I would only add, the imax b6 you see on ebay are almost certainly copies of unknown quality. 

 

Real thing will be nearer £50.

 

https://www.unmannedtechshop.co.uk/product/skyrc-imax-b6ac-v2-charger/

 

 

 

If I got a genuine ImaxB6, what are the actual advantages over a B3? 

Also. I do have one of those little battery checkers people have suggested I just never thought to use it.

After just 8 mins flight of the Wot 4 this morning the battery showed 13% while before flight it was 97%. I've knackered the Lipo, haven't I?

[leccyflyer]

14 minutes ago, paul devereux said:

If I got a genuine ImaxB6, what are the actual advantages over a B3? 

Also. I do have one of those little battery checkers people have suggested I just never thought to use it.

After just 8 mins flight of the Wot 4 this morning the battery showed 13% while before flight it was 97%. I've knackered the Lipo, haven't I?

The advantages are those outlined in various posts above

- You will have a readout of individual cell voltages

- You will know exactly what you have put into the battery with each charge

- You will be able to charge at 1C, giving the optimum between charge time and battery longevity - no more three to four hours to charge a battery

- Because of that additional information you'll develop a better understanding of what is happening, your batteries will be in better condition and you will have more control.

 

First of all though - use the battery checker that you have got and monitor the charge state of your batteries after each flight. Modify your flight times until you achieve an acceptable charge state after flight. Set your timer to that and use it. If that gives a 7 minute flight then enjoy the 7 minute flight. If you are on a budget, provided that your lipos are not completely goosed, are reasonably balanced, not puffed and in otherwise good condition, you can live with a shorter flight time.  You'll only be able to tell if the cells are reasonably balanced if you monitor the per cell voltage.  The percentage figure doesn't give you the information necessary to monitor pack health.

[steve too]

36 minutes ago, paul devereux said:

After just 8 mins flight of the Wot 4 this morning the battery showed 13% while before flight it was 97%. I've knackered the Lipo, haven't I?

 

Ignore the percentages. What were the cell voltages 15 minutes after the flight? 

[Graham Bowers]

The linked document is  best practice tips, and all in one place.

I've destroyed a few packs out of ignorance, and now practice pretty much all of what's stated - it's a good document in my opinion.

 

My departures from it are fairly minor and are as follows:

*Vendor. Haven't tried 4-max packs yet, on my list of things to do.

*Balance charging. Almost always do this, however use a "fast charge" when charging at the field to save time on the odd occasion. "Fast charge" doesn't use a higher current, it omits balancing and a final phase I don't remember, but results in a 95% charge. I only do this with packs that are in balance to start with, and do a balance charge when I next charge.

*Charge at 80% (that's 0.8C). I usually charge at 1C however some of my pals using very expensive packs charge at 0.9C so think I'll change my ways.

 

Everything else I do. In particular, after a flying session, popping all of the packs on the charger one at a time to bring to storage charge state. I have enough chargers to be able to do 3 packs at a time. I'll typically use 8 3S2200's on a flying session.

 

https://www.4-max.co.uk/pdf/prolong-life-lipo.pdf

[MattyB]

Most of that is good, stuff, but a couple of key points...

 

1 hour ago, Graham Bowers said:

*Balance charging. Almost always do this, however use a "fast charge" when charging at the field to save time on the odd occasion. "Fast charge" doesn't use a higher current, it omits balancing and a final phase I don't remember, but results in a 95% charge. I only do this with packs that are in balance to start with, and do a balance charge when I next charge.

 

The occsaional non-balanced charge shouldn't do any harm to the pack itself (provided it was well balanced to start with), but remember when doing so the charger cannot see individual cell voltages. This means if an issue were to occur with any single cell in the pack it may cause an overcharge which in turn could result in a fire. For this reason I would never do a non-balance charge indoors. For beginners like the OP I would stick to George's recommendation to always balance charge - doing so is safer, establishes a good routine, and is one less decision to get wrong.

 

1 hour ago, Graham Bowers said:

*Charge at 80% (that's 0.8C). I usually charge at 1C however some of my pals using very expensive packs charge at 0.9C so think I'll change my ways.

 

I know that some cell manufacturers recommend that 0.8C charge rate, and for packs that are going to need very long cycle lifes (e.g. EVs etc) going even lower will be a good thing. However, for our model lipos (which are quite different in makeup to EV packs) have come on a lot since the early days, and I doubt that 0.2C delta will make any meaningful difference in terms of cycle life (I've certainly not seen any data on it, even in this BU article). 

 

Other than leaving packs at elevated SOC for long periods, the main killer of lipos is excessive heat, whether that is generated during discharge or charge. As long as you don't charge an already warm pack straight out of the model, charging at 1C should be fine - it isn't enough current to warm anything other than tiny indoor 1S/2S batteries of less than say 250mah (these always tend to have a pretty short cycle life, probably because their IR is higher and the chargers cruder). The best test for me is the mk1 finger(!) - if you can feel no discernible heating of the pack on charge, you will be fine. Whislt I generally charge at 1C in parallel on 90% of occasion, if I do need to charge quickly at 2C I will do that; some packs that I've done that with have 250+ cycles and are still perfectly usable, so (compared to leaving packs at elevated SOC) it would appear the occasional charge at rates up to 2C is a less significant effect.

Edited May 26, 2023 by MattyB

[MattyB]

2 hours ago, paul devereux said:

If I got a genuine ImaxB6, what are the actual advantages over a B3? 

Also. I do have one of those little battery checkers people have suggested I just never thought to use it.

After just 8 mins flight of the Wot 4 this morning the battery showed 13% while before flight it was 97%. I've knackered the Lipo, haven't I?

 

You have almost certainly reduced it's cycle life, but I would not say it's knackered beyond being usable - 7-8 mins is pretty typical for a model of that size and type on a 3S 2200. Just take it as a learning that you need to take a bit more of a scientific approach to battery usage and care in the future; we've all done it (my Dad killed his entire first set of lipos because he insisted on charging them to full immediately after use, then they were frequently left for weeks on end between flights in the off season... that was an expensive lesson!).

[Nigel R]

2 hours ago, paul devereux said:

If I got a genuine ImaxB6, what are the actual advantages over a B3?

 

Think the responses already cover the advantages over the simpler B3 unit.

 

However. If you mean, the genuine over a clone, then I would say the genuine unit will work at its rated limits... but a cheap clone may well skimp on the internals - and only really be able to work safely at a much lower output. 

[Nigel R]

1 hour ago, Graham Bowers said:

Fast charge" doesn't use a higher current, it omits balancing and a final phase I don't remember

 

Final phase? I've only ever heard of the fast and balance phases for lipos. Maybe thinking of lead acid? Lead acid has three phases (bulk / absorbtion / float).

[Cuban8]

Re the Cheaper Imax chargers. How do you tell the copies/'genuine' apart so one is not being had by a reassuringly dearer price tag?

Both of my Imax chargers were not full price items bought ages ago, but I've no reason to question their quality or performance thus far. Is this another Spektrum V fruit brands issue?

[Graham Bowers]

28 minutes ago, Nigel R said:

 

Final phase? I've only ever heard of the fast and balance phases for lipos. Maybe thinking of lead acid? Lead acid has three phases (bulk / absorbtion / float).

I just looked up the instructions for the charger (Bantam BC8) and it truncates the Constant Voltage phase. I'm no expert on this, I just remembered there was something in the instructions about it. I attempted to load an image of the instructions however as is mostly the case, the image failed to upload. twice. 69KB jpeg!

[Simon Chaddock]

According to Hobby King the clone B6AC is slightly lighter at 580g compared to the genuine at 623g.

The decals on the front are a bit different but that could just be the result of cosmetic updates.

In performance there is none although HK do say on their site that the fault returns are lower on the genuine Imax B6.

You pays your money and takes you chance.  

[Nigel R]

C8 the clones probably have the exact same chip controlling the thing, but old or early version software, ie more bugs etc. The expensive bits are the power components that control the output into the lipo and any power supply fitted. These may likely be not as capable. Possibly skyrc might actually do some qc. Build quality e.g. heat sinking of power components may not be up to scratch in clones. There are a lot of corners that can be cut internally.

 

I inherited several chargers that failed and in both cases they had awful quality power supply modules and the main FET was not even using a heatsink in one of them. 

 

As posted, you pay your money. 

 

You can also get lucky with a clone. 

[MattyB]

I know many people love these IMAX 4 button jobs with AC/DC compatability, but at 60W they are pretty low power, lower quality fakes conterfeits are commonplace and they are just a bit outdated IMO. If you are confident you'll be in the hobby for the long term I think it is better investing a bit more and getting one of the more powerful digital chargers that have emerged in recent years from the likes of ISDT.

 

Personally I'd go with a DC version with server PSU to power it, but if you prefer AC they have those as well. If I didn't already have a couple of nice Junsi iChargers I'd go this route; they are cheap enough that you could buy 3, run them all off the same server PSU and eradicate the need for parallel charging the vast majority of the time.

 

https://www.t9hobbysport.com/isdt

 

 

Edited May 26, 2023 by MattyB

[Philip Lewis 3]

Hey Hey, Matty

 

you've pretty much described what I have to a T and I can confirm it all works very well, I use three of these chargers fed by two ex server PSU's, 12 packs charged all at the same time is a good days flying for me with no waiting around to change over batteries on chargers, whole lot done in about 45 minutes.

 

Phil