Storm Warning

[Tony Gower]

i bought a Storm 850ma Rx battery [LiFe]. Charged at 1/2C I got "contact break". At 1C or 2C [2C is ok per label] it charged ok. But it only charged to 93% [yes, i know about how [in]significant that is but everything else goes to 99%]. It then self discharged over a few minutes to 65%. Told my LHS who immediately replaced it. Same prob. And again; same prob. Knowing I make up my own A123 packs and buy Lipos & enerloops from them and test everything they then asked if they could charge this 3rd one [maybe he's getting too old?]

LHS charged no.3 ok- to 93%. Put a meter on it I said. They watched it self discharge steadily over 3 minutes to 63%..... They sent the 3 back. And gave me a fourth "from a different batch".

Nothing wrong said supplier. LHS owner sent them back again and we are still waiting. I think we will wait.... The 4th one? Discharged over days not minutes- still much worse than a NiCd. Came back from holiday; 53%. Tried to recharge "contact break"! Bought a Zippy LiFe; seems ok. No more Storms 4 me. Be warned.

[Allan Bennett]

Because of their very flat discharge characteristics, it's difficult for chargers and meters to estimate charge percentage from voltage alone, unlike with LiPos. My chargers usually show something in the low 90s for % when they've just completed charging my 2300mAh A123s, and those batteries have been giving good service for several years now.

I agree that they shouldn't be self-discharging as quickly as you say though. You're not holding the voltmeter on them to watch the voltage dropping, are you? That could cause them to discharge through the voltmeter, especially with such relatively small battery size.

I have no experience of Storm batteries, so am not arguing that they're good ... only starting a discussion

[Tony Gower]

I have 2300 and 1100 A123 [A123s are also LiFe] packs that are 2 and 3 years old now holding 96-99%. Smartmeter attached [takes negligible current] to them and they are stable. Smartmeter on or OFF the Storms I bought and they discharged rapidly. I could certainly not trust them in a plane and have now got my money back. But never my time wasted with them.

Thanks for the comment on low 90%s, I know not to be too surprised as they get older- they were all at 99% till recently..

Have you seen comments at RC Groups re Storm flight batteries? Broadly as i read it people there disassembled some, following problems, and report they were from a variety of sources, with the label advising a higher capacity than the original label.

I look forward to next month's RCM&E which should have a report on some tests against Storm's claims. I do wonder though to what extent any magazine which accepts big adverts could really give a report which is similar to those peoples' findings, if their own findings are similar [I have no experience of any other Storm batteries, and I never will have].

[Peter Beeney]

This is quite an interesting little story. I must admit, on the face of it, it does seem as though the cells are discharging quite quickly but would it be worth trying an alternative method of testing? I’d consider that the voltage is just falling somewhat more than usual, though, it’s unlike they have a short circuit somewhere, for instance, as it’s unlikely they would not charge properly to begin with, anyway. I take it some sort of capacity reader was being used, not a standard multimeter? I’ve personally never been totally convinced by those things; and indeed recently when a pilot crashed his model soon after take off I was convinced it was due to a flat battery but someone checked it with a capacity checker and it read as satisfactory. However, when I then checked it properly it was completely flat. So far I’ve been unable to catch up with that particular battery test unit to find out what’s wrong with it.

Allan, I think the input impedance of an average modern voltmeter would be in the order of 10 megohms, or 10 million ohms. Thus at 6 volts the discharge rate is 600 nano-amperes, or 600 billionths of an amp. If you used this as a discharge load you would eventually be in Rip Van Winkle territory, with a long white beard that goes all the way there and back again, and still waiting for a result!

A rather more expensive class of meter would be an even greater input resistance still, in excess of 1 giga-ohm, I believe.

Some of these modelling consumer cells can sometimes be a bit reluctant. I was recently given some brand new lipos to examine, which the charger had rejected as faulty, plus another charger had not been able to charge them, but after I insisted that they charged up they started to behave and after a few forced cycles they became normal, with slighter greater than the labelled capacity. They are still in regular use today; and I have many stories of nicads and particularly nimhs that were considered scrap but just required a spot of sorting out to restore them to good health.

With regard to any low capacity cells, this is sometime I’ve been trying to flag up for years, but perhaps without much success, many packs do not always contain what is printed on the label, sometimes by a considerable margin! The ideal way is to do your own initial capacity check and then stick your own label on.

I think it would be a good idea it we had a close-up look at a couple of these Storm LiFe packs, and if Tony’s LMS still has a couple of packs still in stock that would be an ideal place to purchase them from, if that could be possible, we could then be reasonable sure they came from the same batch.

PB

[Peter Beeney]

Unedited photo direct from camera.

Because I was somewhat intrigued by these batteries, I like little mysteries, I’ve now purchased by mail-order a Storm LiFe 850 mAh receiver pack to kick around. I’m going to use LiFe as receiver power in the future anyway, so it will eventually be used as intended. I bought this one to see I could find out what was occurring with them.

When it arrived yesterday, I checked the open circuit at 6.000 volts, then each cell and they were both exactly 3.000V each, now the pack again, that reads 5.999, completely insignificant. Then to check the capacity I did a fairly sedate discharge at 200 milliamps, this started descending steadily but then suddenly ran down to 4 volts and terminated. The capacity being 396 mAh. The open circuit voltage of number 1 cell, positive end of pack, was 2.235V, and the other cell 2.636V. Quite a big discrepancy here, now, and very low capacity; indeed it does begin to look at if there might be a bit of a hiccup looming. However, I learnt years ago never to pre-empt anything, and particularly batteries, you need to complete everything properly.

So I then gently charged each cell individually at 150 mA, number 1 taking 794 mAh, up to 3.664 volts, and 2 soaking up 719 mAh, up to 3.670 volts. Then a discharge at 600 mA straight away, the result being in the photo. The capacity has now improved to 853 mAh, better than the manufactures label; but only just, that’s from a start voltage of 6.830 volts, down to 4 volts. The charger says 3.99V, but the actual accurate voltage at the pack was 4.032V. The discharge rate being 600 mA for no other reason than it’s just below 1C, not too fast for a new pack but sharp enough to show a nice discharge trace on the screen.
At this rate I noticed the voltage fell quite rapidly to just below 6.6 volts, within a couple of minutes of the start, but then continued to hold this level for a while, but of course the voltage of any battery being discharged will always slowly decline.

So on the basis of this so far I would deem this pack to be a success, certainly within spec. here, so far. The label gives a maximum charge rate of 2.5 amperes and a discharge rate of 17 amperes. If it will truly discharge at this rate this would indicate that the internal resistance is quite low, certainly easily capable of coping with any servo loads placed on it without dropping the voltage too much. It would be unlikely that I would want to use this small size of pack in anything much above the standard 46 - 53 size, 5-6 servo model anyway. Charging at 2.5A says that in theory you can fully re-charge in 20 minutes, although I expect that would tail off toward the end, extending the time by some minutes. But you could certainly put quite a lot back in in quarter of an hour.

In conjunction with the Hextronik on-board LiFe voltage monitor, with a total weight of probably less than 50 grams, I reckon this might be ‘magnificus purfektus’ as regards a receiver power supply.

Don’t you just love it when a plan comes together……

One very slightly negative point though, it comes with heavier power leads, for a battery that is ostensibly a receiver pack, but no connector plug. As I sometimes solder the pack straight onto the switch harness that’s not a big deal for me anyway, but for anyone not used to soldering this might be something of a minefield. It comes in a small cardboard box, and there are some fairly comprehensive instructions and advice lines, including one that says completely finish and insulate one wire before you do the other. Logical but not always necessarily adhered to, perhaps!

Also a Warranty and Accepted Terms of Use - part of which reads - “As the end user of this product it is your repressibility to thoroughly inspect this battery before and after use and before and after charging and as such you accept full responsibility for any injury, loss or damage resulting from you using or mis-using this product”. I’ve not seen anything like that related to batteries before, although it’s written on the box, rather than the battery.

I shall continue to bash it about, next it will be a full charge and then rest it for a week before discharge. Although I’m fairly confident this will not now be an issue. Plus some heaver discharges, just to see if it is sincere or just boasting.

It’s not wise to use the open circuit voltage of nickel cells as an indicator of state of of charge, it doesn’t tell you at all what the remaining capacity is; I’m beginning to think that perhaps the open circuit voltage of these cells might be a mite unreliable too; but this would need some more investigation. Also some brand new nickel cells have played up in the past, with the loss of some models, although they are not faulty, just not accepting the initial charge properly, it’s now looking as though there is some evidence to suggest this might also be the case with LiFe’s. Up to a point, anyway.

Always a good plan to check everything first!

PB

For 'repressibility' please read 'responsibility' It's correct in the post box, but the site can't, or wont, read my writing properly. *!*)(* 

Edited By Peter Beeney on 09/06/2012 14:03:02

Edited By Peter Beeney on 09/06/2012 14:10:45

[Tom Wright 2]

Excellent work Peter .But it does highlight the amount of knowledge necessary to ensure safe flying and is it reasonable to expect every Sunday flyer to understand the characteristics of the many different types of DC sources ?

Even with a basic understanding it does not necessarily follow that a user is qualified to take the correct course of action when a problem occurs.

Tom.

[Tony Gower]

Peter seems to have been lucky with his one, so I am pleased for him. Yes, the spec looked good [lighter than own assembed 2S A123 1100s, cheap, tho much more expensive than the A123s] but I was not lucky, 4 times. So for me the proof of the pudding means I cannot trust them, except as a guaranteed waste if time.

The LHS sent 3 back for credit. The 4th they discharged and disassembed. They said it looked well put together but had no meaningful marks [e.g. capacity, manufacturer], just a code on the cells

.

[Peter Beeney]

Tony, - with the greatest respect, but do you think there is any chance of your LMS still having one of these packs lurking about that I might be able to purchase, please? I would then do an identical discharge test and it would be then be an ideal situation to be able to get a direct comparison. It does seem to me that four batteries being duffy in a row is slightly unusual. Also I’ve played around with some LiFe’s, a few of my own and also a number for other people, and without exception they have all been right up to speed, so I was beginning to think that the quality standard might be quite high. But I’ve never tried the Storm variety before.

I recharged my pack on Sunday last and I’ll discharge again it this Sunday, 7 days, to make sure there are no self-discharge problems, I’d expect it to very similar in capacity, 853 mAh, but I’ll give it the benefit of the doubt if there are just a few milliamps short.

I’d quite understand should you not wish to pursue this any further, too, but it would only be from just the interest point of view. And a possible guideline for any future reference, maybe.

Hoping this meets with your approval…

PB

[Steve Hargreaves - Moderator]

Interesting stuff as always Peter....I too am looking at LiFE cells as a way to power my radio....the better voltage stability & negligable self discharge appeal to me.

I have a pair of A123 1100mAh cells that I've been kicking around a little bit. Slightly lower capacity than expected at around 950mAh based on a 0.5A discharge & charge. The voltage stability is impressive....they sit at around 6.5volts for the first 600mAh or so.....dropping to 5.9 volts by 900mAh & then rapidly collapsing to 4.0 volts at the 950mAh mark......& boy when they go do they go quickly.....

I got similar results with a 2A discharge...again the voltage holds up very well until the cells are nearly exhausted.....like Peter I noticed a big difference in the cell voltages when the battery was flat but they charged OK & came back up to the same voltage....they may "improve" with a few more cycles.....I uderstand that these cells like to be used.....

Interestingly Hobbyking have just started stocking Turnigy Nano Tech LiFE batteries for Tx & Rx use but these are the foil packed versions rather than the metal cans.....this 1450mAh unit looks very interesting.....I particularly like the 20-40C rating which makes me wonder if there really are people who might need 58A to power their radio ......

I already have a 3S LiFE pack in my Transmitter & this has been brilliant.....

By the way has anyone noticed the LiFE cells on ebay.....same 18650 can as the (1100mAh) A123 cells but 1800mAh capacity.....h'mmmmmm

[Martin Harris - Moderator]

...and 3.2V ?

[Steve Hargreaves - Moderator]

Yes....intruiging isn't it.....

Almost worth ordering some to have a look-see

[Bob Cotsford]

I've been running the HK 'Zippy' 1100mAh LiFe foil packs in several models for a couple of months without problems.

I say without problems, I don't count my attempt to immolate the Marabu by trying to charge the pack as LiPo. Didn't do the pack a lot of good, they bloat just like LiPos y'know.

The Altair is running two packs through a HK twin regulator switch, the others are just plugged in the same as a Nixx pack would be. So far I've yet to put more than 3-400 mAHr back in after a days flying, though I usually take several models so they only get 2 or 3 flights at most.

[Peter Beeney]

The Storm packs are metal foil types, too, and they certainly can look a bit like a Lipo battery at first glance.

Oddly enough, all the1,100mAh LiFe cells that I’ve looked at have always seemed to have been a bit down on capacity, whilst the larger ones have been well up to capacity. Also this was the findings of a mate that test discharged a rx pack of 1100’s, he remarked only recently they were around the 950 level. So it may well be that this is is fairly universal, and these need to be generally considered at a lower capacity, say at about 950mAh, perhaps?

Any cell that has a very flat discharge characteristic is always only ever going to fall off very rapidly at the end. My way to ensure trouble free battery power is first to use a voltage monitor; then equally to know the state of health of your batteries, capacity etc; always start any flying session with fully charged batteries and lastly have some idea of the expected amount of discharge, so that you know that the receiver pack will last a reasonable time, anyway. Plus a little point that is not always in place, make sure the socket/plug is secure and cannot become unconnected.

In very general terms I’d like to think that 3.2V per cell might actually be slightly more conservative than the 3.3 figure; and so in effect may be a slightly better indicator. The manufacturer is always going to be as optimistic as possible. I see one reason for this figure as being the multiplier to calculate the watt-hours for a battery, a 1Ah pack looks better at 3.3Wh than 3.2! This has to be an average, though, and I suspect the average voltage is probably closer to 3.2 than 3.3 during the whole of the discharge. Certainly LiFe cells tend to come off the initial high voltage level quite quickly and then flatten out.

The average value of a Lipo cell is calculated like this, the mid point between 4.2V and 3V is 3.6, this was the original figure quoted, until someone somehow managed to squeeze a little more out and changed it to 3.7V. Where it’s remained ever since.

Having said all that, the eBay examples do look slightly unusual. I don’t have a PayPal account, but if I can find someone that will buy a couple for me I’ll make a rx pack and give them a try. A direct voltage comparison with the Storm battery would work perhaps, making the appropriate adjustments for the difference in capacity.

I have a colleague with an Eagle Tree logger, so maybe I’ll be able to borrow this and run a discharge and find out what the average voltage level on an A123 actually is. Or with some careful monitoring, I might be able to get a good idea using a standard discharge.

With regard to the 20 - 40C rating, this may well be useful, not in terms of the all out current supply, but the fact that the lower resistance will ensure that if there is a sudden demand, all servos working together, say, then any battery voltage drop will be kept to a minimum. Plus the fact you can also re-charge in double quick time means you can use a smaller and importantly lighter pack, if you so wish. I’m sure that with proper management it’s quite possible this 1,450mAh pack could be used in quite large models, I’d certainly be quite happy to do that. If we assume that the average 60” span 4 servo trainer radio has a constant quiescent (idle) current of about 50 milliamps, but that’s a bit of a calculated guess, and the model uses 120mA per hour, the power used to actually drive the servos and steer the model is fairly minimal anyway. Around 70mAh, but this is only a bit of a guesstimate, it would need some more careful checking.
Using these figures, we have 12 hours of flying on this battery; and 7 hours on the 850mAh Storm.

Going back for a moment to that 3.3/3.2 voltage figure, having now done a discharge on a single 2,300 A123, see photo above, I’ve had a slight re-think. Again this was at the 2 amp rate. On the figures I recorded the average voltage over the whole of the discharge was 2.766V, which I straightaway think is somewhat misleading. If we ignore the last 310mAh and just consider the flat 2,000mAh line, the time up to 60 minutes, (the 64 on the bottom line is the time in minutes), and this is the part that really matters, the average voltage over this part of the trace was around 3.262V. This average is never going to be as high as 3.3 volts, though, because at 6 minutes the voltage had dropped below 3.300 volts. But, very significantly, the voltage only fell 250 millivolts during this 2,000mAh part of the discharge. I do have a full set of figures if anyone’s interested.

A couple of points, this cell is right up to capacity, indeed, 10mAh over, in fact, and again although the charger is saying the charge termination voltage was 1.95V, the true voltage at the cell was 2.146 volts.

Just for interest, I will post the results of any further runs I do on the Storm later.

PB

[Bob Cotsford]

I did cycle an '1100' LiFe once, I think it came out at 9xx mAHr rather than the stated 1100, but that's ok. I used to fly 4 channel models four or five times on a 500 DEAC, then 700m and 800 Nixx became the norm and I still managed to get my flights in, so 900 is more than enough for 'average' power models.

As the Altair is a bit bigger than average with digitals all round it gets 2 packs. It does help that my FrSky gear provides programmable low battery warnings!

[Peter Beeney]

I’ve now given the Storm LiFe pack a further discharge after fully charging it last Sunday and then just leaving it dormant for 7 days. This is the result.

The open circuit voltage was 6.712V, first cell 3.352V and then 3,360V. Discharged, as before, at 600mA. After one minute the voltage was down to 6.482V, at two minutes it was 6.462V. At ten minutes it was 6.441V. At 75 minutes, and 745mAh, the voltage was 6. 098V, this is about the point at which I estimate the discharge curve turns over and starts falling quite steeply. The discharge finally terminated at 4. 093 volts, at 85 minutes, having now recorded a total of 849mAh. A couple of hours later the open circuit voltages were 5.765, 2.804 and 2.961 volts. At 4 milliamp hours short of the first discharge, over 7 days, I’d consider this acceptable.

So from this I think I would conclude that there is no self-discharge problems with this Storm pack. The voltage fell 384 millivolts from 1 minute to 75 minutes, very stable, with an average voltage of 6.290 volts.

The next test will be a bit of a bashing at some higher discharge rates, with a check on the volts drop; and if it passes this, i.e. no big dips and I’m sure there won’t be, then I will use it as a receiver pack. I’ll keep a careful eye on the individual voltages, too, because I won’t balance the cells for a time, at least not until I have to. Also it might be a good opportunity to get some accurate figures on current consumption by carefully monitoring flying times and conditions. I think this will just sightly augment all the information that’s out there already, it requires less rather than more radio power to fly models.

All in all, so far, I’d say this one at least is a success story……

PB

[Steve Hargreaves - Moderator]

Well I've been having a bit of a play with some LiFE batteries too.....I ordered one of these from HK & it turned up along with a voltage monitor......a quick charge & then a full discharge & charge at 1C both ways showed a capacity around 550mAh so a good bit less than the advertised 700mAh.....the voltage was very steady however & this is the packs first cycle so things may improve.....

I am also struck by the sensitivity of the monitor......when I first plugged it in I got a top green which soon dropped to a second top green but with the LEDs above & below slightly illuminated.....moving the servos dropped another green & illuminated the ones below & above as before. Odd thinks I that a couple of servos can drop the pack voltage like that so I got the meter out & the voltage was stable at 6.58 volts dropping to about 6.52volts when both servos were moved. The monitor therefore is very sensitive with a drop of 1 LED corresponding to 6 hundreths of a volt...

Given the way the voltage drops off a cliff as the pack nears exhaustion I guess they need to be sensitve to give much advance warning.....

It will be interesting to see how much goes back into a pack after a flying session......

[Steve Hargreaves - Moderator]

A bit more news......I made up a LiFE battery from two 1100mAh cells for another model (typical 5 servo 40 powered hack) & charged it up about 1 month ago.....I flew it over the weekend for 4 x 10 minute flights which I flew flat out pretty much the full time with sticks regularly in the corners......

At home I put the battery back on charge to see how much had been taken out by the 40 minutes of flying.......it took 77mAh according to my charger....

So, a months storage & 40 minutes in the air equates to 77mAh......not bad!!!

Personally I think thats a bit low so I want to do a bit more testing/checking but its an interesting result.....

[Bob Cotsford]

I've noticed that my LiFe packs generally (when I've noted the charge) take about 90mAH for every flight in my .60-.90 two stroke sized models. That would be three or four minutes starting the engine, another minute or two carting the beast of choice across to the fightline, ten minutes or so flying, and one or two minutes more before switching off the model. Say eighteen minutes, with half of that on the ground so not much servo action. The Altair has all digitals, the Extra and Chipmunk analogues and the Tornado a mix, so in normal sport use servo type doesn't seem to make much difference.

It also fits with the 4 or 5 flights we used to get out of a DEAC!

[Steve Hargreaves - Moderator]

Interesting stuff Bob thanks.......like you I have the usual faffing around on the ground but the 40 minutes actual flight time is accurate based on the 10 minute timer I have set for this model (it runs out of fuel at about 11.5 minutes!!)

Based on the 77mAh put back thats less than 20mAh per flight........not a lot is it..... in fact I can't actually believe it as I would have thought the "at rest" current was greater than 20mA

Edited By Steve Hargreaves - Moderator on 23/07/2012 12:12:22

[Bob Cotsford]

Plucking figures out of the air, what does a receiver take, about 30-50mA? Servos at rest <10mA? Your 77mAH over 40 minutes is about 120mA average current drain (call it 80mAH /40 minutes*60 to get the power consumption over 1 hour) so not unreasonable. Or have I got that wrong?

[Bob Cotsford]

ps - working that out makes me feel much happier about the fact that my .60 powered sports models are fitted with single 1100mAH LiFe batteries.

[Steve Hargreaves - Moderator]

I think your maths is spot on Bob...no problems there.....

What does confuse me is that I think I would usually put at least double that back into NiMH cells after a similar flying session......

Self discharge of the NiMHs perhaps??

[Bob Cotsford]

Depends on when you do the charging Steve. My practise is to charge the night before I hope to go flying, so chances are the pack has been sat for 5 or 6 days since it was used, probably more if it's not one of my favourite models. Older Nixx typically take a lot more charge so yes, I think self-discharge is a big factor, and more noticeable if you take several models and might only fly some once. If you fly a model 4 or 5 times, then self-discharge will be a smaller proportion of what you put back in the next week.

edit - that made me think, I've got a couple of LSD packs and I had thought they took less recharging than the old style.

Edited By Bob Cotsford on 23/07/2012 13:49:19

[Steve Hargreaves - Moderator]

I think you are right Bob but as per your edit I too have LSD packs in most of my models.....like you I tend to charge 'em a day or so before flying....I've never brought myself to trust the LSD tag....

With the LiFEs though it appears that self discharge is a thing of the past & this is their main appeal to me.....come home, charge the models, take out & fly in a few days/weeks/months time & the batteries are still charged..........

Certainly the LiFE battery I fitted to my Tx seems to work like this...I get hours & hours between charges (max so far 5 hours use but still only took around half the nominal capacity to charge it up...) & with the amount I fly hours & hours equates to many weeks (months??) between charges....

[Peter Beeney]

Steve - I think we’ve been here before with regard to the amount of power the radio consumes in flight. I think we came to the conclusion long ago that it is indeed very little, although of course it will be in proportion to the size of the model, type and number of servos etc. The radio idle current will be a small but steady amount, so if we consider that the main demand might come from the servo motors and that if that power is in proportion to the time the servo motor is running and also the load on the motor, then I think we would conclude that it is indeed not a great deal at all. From this we might assume that the servo does relatively little work. This is why I’ve always felt that servos are quite trouble free, in my experience they seem to generally go on for ever, and I’ve personally witnessed very few failures. The motors, when you look closely, are in the main very basic small permanent magnet carbon brushed types, which if given any hard work to do, I think would tend to wear considerably more. So that the overall conclusion I would come to is that it takes very little effort to actually steer the model around the sky.

I also did a definitive check on the Hextronik monitor, which is posted in a thread somewhere. In fact I did four together, as a cross reference, and as I remarked at the time when I connected all four in parallel, they all lit the bottom red led exactly simultaneously, so that’s extreme accuracy in my book. That bottom red led lights up at possibly 3 times normal power when the battery voltage gets down there, too, so you won’t miss it; and it comes on well before you get to the bottom of the battery.

I would consider this to be an expanded scale voltmeter, measuring in millivolts rather than volts, so maybe it’s just recording a touch of volts drop across your switch harness. To prove this, plug the battery straight into the receiver and the monitor into the channel next to it. Then waggle the sticks and notice if the led’s waver at all. If they do, I’d say this is not particularly good news, the success of the LiFe is largely down to it’s low internal resistance. We also have noticed that all the LiFe batteries come off the top led fairly quickly, but are then very stable after that. So I’m wondering if the 3.3 nominal voltage given for LiFe’s might be a touch optimistic, but in the event I don’t suppose it makes very much difference. All the time the voltage at the rx stays at or above 6 volts nothing is going to come to much harm, I guess.

Interestingly, I’ve just tried to road test a couple of the 3.2V 18650 LiFe’s mentioned previously in this thread, and they were a complete failure. Whilst lying idle for a short while one went completely short circuit, in my book that is very unusual indeed, a one-off. My colleague bought them, and if we can get some replacements I will try these.

Another way of checking the the power consumption is to check the rx pack for capacity so that you have the exact number of milliamp hours, then fly for as long as possible, taking the battery well down and noting the total time of course, then discharge the remainder of the pack at a fairly slow rate and see how much is left. Take this from the recorded amount and you have a precise record of how much you have used, without having to consider any extra for recharging etc. It does work, that how I’ve always done it.

PB