EDF lipo battery level

[Rocker]

What is the lowest level you should let your lipo get to before landing.? 

[J D 8]

Having flown EDF for a dozen years I would say no lower than 15% but prefer to have over 20%

 However more important I recon is using the right sort of lipo, that is high C ones that can better handle the more or less high continual power draw and are still only warm to the touch after 5/6 mins of ripping up the sky. [ don't see the point of flying a DF jet at less than flat out.]

[Chris Walby]

IMHO normal models 30%, edf 25% and it will shorten the life.

My SU37 did 3 min and 15s, and landed with 4%....one knackered 6S4500 that was never the same. Expensive lesson and no change of a go around so not a good place to be in

[PeterF]

As with post above, I target 20% as a minimum.

[Martin Harris - Moderator]

31 minutes ago, Rocker said:

What is the lowest level you should let your lipo get to before landing.? 

Somewhere in the region of 5 - 7 inches on an average model.  Gliders and other models with no undercarriage can go a little lower  ?

[Outrunner]

The battery doesn't care whether it's powering an EDF or propeller it won't like being over discharged. An EDF might discharge the battery quicker though....

[GrumpyGnome]

18 hours ago, Chris Walby said:

IMHO normal models 30%, edf 25% and it will shorten the life.

My SU37 did 3 min and 15s, and landed with 4%....one knackered 6S4500 that was never the same. Expensive lesson and no change of a go around so not a good place to be in

 

Lots of people in my club seem obsessed by the % remaining in their LiPo's.  They fly for a few minutes, land, check LiPo, repeat until they get bored, or the LiPo is 'low' (when I asked whether the remaining % was from a zero baseline or something like 3.85V per cell, they did not know.

 

What I do when I get a new plane is this.....

 

1. Potter around for a few minutes to make sure trim is OK, all functions work etc., see what happens with flaps/gear. Land.

2. Change battery to one that I know is good, and fully charged, of the lowest capacity I am going to use

3. Fly normally until LVC cuts in or my battery monitor (if fitted) reaches my cutoff

4. Set my timer for 30 seconds less than 3. above.

 

Not killed a LiPo using this method - yet!

 

On my little edf's, I do reach lvc before the timer occasionally - but usually if the cells are a bit past their best. 

 

My caveat is that I have no packs greater than 4S so they're not hideously expensive.

 

 

[john davidson 1]

The battery capacity and C rating are interlinked, if after 2 minutes of full throttle the battery is very hot , not just slightly warm on landing it is being abused and should be changed  for one of greater capacity or C rating, carrying on will end up in a puffed  battery

[Chris Walby]

GN, Feel free to fly my SU47 and see if you can squeeze more than 3 minutes out of the flight time, but believe me if it was an easy floater there would be more models with forward swept wings and thrust vectoring + moving canards!

 

[leccyflyer]

I never use a % figure, I monitor the individual cell voltage after each flight. If it's around 3.85v/cell then I'm happy and my timer is doing it's job. If it's 3.7v/cell then I'm working the pack too hard and so I reduce my timer accordingly. In very cold weather I tend to reduce the flight time by a minute.

Bench testing has shown that a resting voltage of 3.75v/cell on my most common 3s1p 2250mah packs equates to around 3.3v/cell and I'm not keen on going lower than that. Left for 30 seconds off load those packs will rebound to 3.75v/cell on my battery checker. I've no idea whatsoever what any of those voltages nominally equate to in terms of percentages.

[PeterF]

22 hours ago, PeterF said:

As with post above, I target 20% as a minimum.

I do this because I have added current sensors to all models which integrate the current with time and return used mAh to the Tx. No need to rely on timers and it means that if I want an absolute hooligan flight I can do so without worrying about running out of juice quicker than a normal flight. Really does take the major concern out of flying larger EDFs.

[Trevor]

. . As long as you can keep track of what the real useable capacity of the battery is as it ages.

[Simon Chaddock]

Quote

As long as you can keep track of what the real useable capacity of the battery is as it ages

A good point. Not only capacity but internal resistance (in effect the C rating) also decreases with use. What might be an acceptable discharge rate for a new LiPo may well be damaging it as it deteriorates. The harder you work a LiPo the faster it decays.

A 20 C discharge rate equates to a full power run of 3 minutes maximum and less if you want to 'kind' to the LiPo. ?

[Geoff S]

54 minutes ago, Simon Chaddock said:

A good point. Not only capacity but internal resistance (in effect the C rating) also decreases with use.

 

If only.  I know you actually meant internal resistance increases and hence the C rating decreases but ... ?

 

I find once IR goes above 10 milliohms/cell  (or even before for some applications) the battery is toast.  Lower than 5 milliohms/cell is better.  Though I don't make big demands of my cells as I don't fly ducted fans and use the throttle in both directions.

[Trevor]

I think it may have been said before in this thread but, if you don’t want to bother monitoring your batteries’ internal resistance etc., I think the simplest way to check whether you’re abusing them is to check their temperature immediately after the flight. If the pack is more than very slightly warm, then the battery has been stressed. This maybe because of high current draw, (e.g. in EDFs or when aerotowing) or because of discharging the battery too deeply. 
 

As Simon says, as the battery ages, you may well find that a particular model and flying style warms the battery more than it used to. This is a sure sign that the internal resistance has gone up and the battery is now struggling. If you wish to prolong its remaining life, it’s time to re-deploy it on lighter duties, e.g. in a less demanding model.

 

Trevor

[Jeffrey Cottrell 2]

On 04/04/2022 at 16:54, Geoff S said:

 

 ?

 

I find once IR goes above 10 milliohms/cell  (or even before for some applications) the battery is toast.

Hi All

Was going to start a new thread, but Geoff's post was enough to start the discussion, so here goes:

I am a big fan of Turnigy Blue lipos, but since it looks unlikely that HK will ever re-start deliveries to UK, looking round for a suitable alternative brand.

Seen suggested that HRB lipos were good, so bought a couple of 2600 4s for a try. Came from Amazon, delivered withing a day and good price, so no complaints there.

However, checking IR on my ISDT charger came out with figures of 15.7, 18.4, 16.1 and 16.1 for each cell. Geoff's quote would indicate these batteries are already 'toast' before they've even been used.

As a baseline, I pulled a TGY 2650 4s from my dwindling stock and measured 7.6,7.2,8.0 and 8.8. Even a used one measured 6.9-7.6.

I do not punish my LiPos, so unlikely to see an issue with the HRB ones, but I was disappointed to see them below par straight from the factory.

Any thoughts?

Jeff

[leccyflyer]

Measuring many of my most used packs, which have scores of charge cycles used,  On my G-Power packs I see frequent IRs of 17-25milliohn/cell and the packs still perform well - they are far from toast. My HRBs -which are newer - are typically measuring 2-6milliohms/cell, my Turnigys are measuring 4-16milliohms/cell. I guess the proof of the pudding is seeing how they perform in flight -unless you're thinking of sending the packs back with the assumption that they are toast?

 

Note I'm talking about flying aeroplanes with propellors, not specifically ducted fans.

[Jeffrey Cottrell 2]

Hi leccyflyer, thanks for the quick reply.

Although I have no doubt these packs would perform ok in use, I am considering sending them back anyway. This only because they are new packs showing an IR more suited to ones that have had many cycles.

Have a question in to the supplier via Amazon. Will see what they come back with.

In your post you said that HRB's you have are showing 2-6 milliohms, which is what I would want to see on new packs.

Definitely something wrong with mine.

We'll see

Jeff

[Jeffrey Cottrell 2]

Hi All

Just to add fuel to the fire, did an IR test on the second pack and the figures are even worse.

I'm getting 18,21.4,19.1 and 19.1.

These are definitely going back.

In general, anyone using HRB packs on a regular basis, what do you think of them?

Would like to think my results are a one-off, but not sure.

Any thoughts?

Jeff

[leccyflyer]

I've been pleased with my HRB packs, which have become my go-to supplier, via Amazon, since the supply of my favourite G-Power packs dried up during lockdown

 

So far I've had 4 x 3s1p 2200mah 30C packs, 2x 4s1p 2600mah and 2x 4s1p 3300mah 35C packs and they have all been very good in practice. Can't fault the fuss-free next day delivery from Amazon and the bundling to supply the packs in pairs. I'm thinking of getting at least a couple of their 6s1p 4000mah packs too.

[Jeffrey Cottrell 2]

Hi leccy, thanks for that.

Looking for a go-to supplier for my lipos.

Anyway, have a question in to the suppliers regarding these two in particular. Will see how they respond, might tell me if mine are a one-off.

We'll see

Meanwhile, changing the subject slightly.

Put a question to HK regarding resumption of supply, got this reply:

'We are very close to finishing all the paperwork needed to start again. Should be done by end of May'.

I know, we've all heard this before, wait and see.

Never ordered anything from Global, on principle. However looking at the price including shipping, seems the more you order the cheaper they got.

Tested with an order for four 2650 4s. Working out the price per unit, comes out at some £29 per. That's way more than the EU price but in the ballpark with what you can get over here direct.

Food for thought?

Jeff

[J D 8]

            Needing some new batts for my EDF F16 and hot set up Zaggi wing last year I purchased some Zeee 3s 2200Mah 50C batts on Amazon, £43.99 for a pair inc delivery.  So far after some used I am pleased as after been thrashed around the sky flat out [ no point in flying those planes around at half power ] batts are just warm to the hand.

  Available with several of the popular connectors.

Edited May 16, 2022 by J D 8
extra info

[Jeffrey Cottrell 2]

Hi All

Have a saved search on e-bay for HRB batteries. Just got an e-mail from them with a new addition.

Seems HRB also do an Alien Pattern led table lamp.

Who'd have thunk it?

Jeff

 

https://www.ebay.co.uk/itm/134119747904?mkevt=1&mkpid=0&emsid=e11021.m43.l3160&mkcid=7&ch=osgood&euid=151aa7e596fc48e7944ca82798c6cd2e&bu=42993982027&ut=RU&osub=-1~1&crd=20220516055144&segname=11021&sojTags=ch%3Dch%2Cbu%3Dbu%2Cut%3Dut%2Cosub%3Dosub%2Ccrd%3Dcrd%2Csegname%3Dsegname%2Cchnl%3Dmkcid

[Tim A]

Having always measured the IR of my battery packs, I have found that the pack temperature makes a huge difference to IR readings. One new battery I received a while ago (4S) from China recorded all cells around 10 mohms. After warming to approx 25 degrees they tested around 3-4 and have stayed that way for 2 years. I have batteries that are around 15-20 that seem to perform fine (may lack a little punch?) if not required to deliver above their constant discharge rating.

[Trevor]

Yes, IR is very temperature sensitive and also different devices will often give significantly different readings. So it's best to take all your measurements on the same charger, in similar conditions. Surprisingly, state of charge of the battery seems to be less of an issue. With all those caveats, attached is the table I use to guide me on whether to put a green, yellow, or red sticker on a particular pack: