Batt Discharger

[Zflyer]

I suppose this is something of a poll. Do i really need a batt discharger?

I tend to charge up a number of batteries before i go flying, something a couple of days before, but then I may not get to use them all so leave till next time. So far no issues.

I also note on this and other sites that battery resistance gets mention, I checked mine and found some were quite high, no puffing or apparent loss of power. Another scare issue, how many actually check cell resistance. Apart from the obvious of not charging in a safe environment and keeping a watchful eye I sometimes wonder whether I get over concerned. I know there are people who have no regards whilst others seem Over The Top. I often think that storage in fire retardant/proof sites is a good thin, mine live in ammo boxes, but then I think about all the model shops where they just hang on display units or stacked on shelves to no harm. 

I am in no way making light of the potential issues just raising an eyebrow.

Please do not regal with tails of people having fires and causing damage to homes or vehicles, I can relate those from club members so suffered.

[Phil Green]

40 minutes ago, Zflyer said:

Another scare issue, how many actually check cell resistance.

Just a comment on this this point, IR isnt a scare issue at all, increasing IR is just the natural degradation of a cell over time.  IR has zero effect until some current is flowing and so can be ignored whilst cells are in storage.

Ammo boxes - yes, they're cheap, convenient and almost designed for the job  🙂

Discharging to storage v is a good plan if the packs are left unused for an extended time ie over winter, but less essential if you fly every weekend - you can trade convenience for some loss of longevity. At one time discharging was a chore but now almost all chargers have a storage function so theres no reason not to 🙂

It sounds like you're well within the happy medium between paranoia and apathy, you obviously respect their potential and you've taken steps to minimise the risk.   Its all good 🙂

Cheers

Phil

 

Edited January 1 by Phil Green

[Andy Stephenson]

It's quite often the case when a battery isn't performing in flight, that one cell is going high resistance.

One good way of checking for single cell degradation in a multi series pack is to use one of those checkers that you plug the balance lead into. Whilst monitoring the cell voltages run up the motor with a prop using suitable precautions of course, and while under load see which cell(s) are dropping their voltage significantly relative to the rest.

[Graham Bowers]

All I can add is that not all chargers are equal in their capability to discharge. My Overlander charger can discharge at 10Watts per channel, so an unused 6S4000mAhr would take around 4 hours to 50%. So I made up some dischargers that use  two 12V 21Watt bulbs in series. No control system so they need monitoring, however I need to try a lipo alarm which'd work fine, I expect.

 

Plan A is always to fly the batteries I take to the field, but it doeesn't always work out, for one reason or another.

[EvilC57]

10 hours ago, Phil Green said:

Just a comment on this this point, IR isnt a scare issue at all, increasing IR is just the natural degradation of a cell over time.  IR has zero effect until some current is flowing and so can be ignored whilst cells are in storage.

Ammo boxes - yes, they're cheap, convenient and almost designed for the job  🙂

Discharging to storage v is a good plan if the packs are left unused for an extended time ie over winter, but less essential if you fly every weekend - you can trade convenience for some loss of longevity. At one time discharging was a chore but now almost all chargers have a storage function so theres no reason not to 🙂

It sounds like you're well within the happy medium between paranoia and apathy, you obviously respect their potential and you've taken steps to minimise the risk.   Its all good 🙂

Cheers

Phil

 

What he said. But if using ammo boxes (like I also do), don’t forget to remove the lid seal, so won’t explode if there is a fire.

[John Lee]

I've been restoring my LiPo's to back storage charge for a few years now using an ISDT FD100 discharger &/or my chargers. It soon became a routine upon returning home to bring all the batteries to 3.8v/cell, whether they needed charging or discharging. If I bring a few batteries back unused I often use a parallel charging board with the discharger.

 

The batteries seem to be lasting better. I've no data to support that statement but subjectively that is the case & certainly puffing has been totally eliminated, including those used regularly in EDFs over 3+ years.

 

A side effect is that for charging everything is always in balance for parallel charging and I only ever have to charge from 50%ish.

[Frank Skilbeck]

Check if your charger has a storage setting, if it has it will charge/ discharge your lipos to the storage voltage depending on the starting condition.

[Fly Boy 3]

Hi all, still in the dark at the moment re electrics , but willing to learn.

     What is the difference of discharging Lipos to storage volts, or leaving them discharge to this voltage. Is it a matter of time ? Thank you

[Frank Skilbeck]

A full discharge takes them to 0%, a storage discharge (or charge) takes them to around 40%, 3.8 v per cell

[Andy Stephenson]

Fly Boy, I think you are referring to self-discharge, this is a process where the charge leaks away internally within the cells without external connection. It is fairly slow with Li-Ion batteries so it won't help in a storage situation. Leaving a Li-ion battery charged much above 4V/cell will degrade it's holding capacity due to side reactions in its chemistry driven by the extra voltage.

[Geoff S]

1 hour ago, Frank Skilbeck said:

Check if your charger has a storage setting, if it has it will charge/ discharge your lipos to the storage voltage depending on the starting condition.

 

Many chargers do but most (all?) do it very slowly. If you only have one to get to storage, it's not a problem, but if you have several it may be. The storage function on my icharger  will charge or discharge as needed.  However, I do have a discharger that will draw up to 35 amps if required and I find it useful.  If I want to discharge a faulty battery for safe disposal, I have a car headlight bulb.  Not tried it with anything bigger than a 4S pack; I suspect 2 bulbs in series might be advisable for higher voltage packs to avoid damaging a nominal 12v bulb.

[Frank Skilbeck]

24 minutes ago, Geoff S said:

 

Many chargers do but most (all?) do it very slowly. If you only have one to get to storage, it's not a problem, but if you have several it may be. The storage function on my icharger  will charge or discharge as needed.  However, I do have a discharger that will draw up to 35 amps if required and I find it useful.  If I want to discharge a faulty battery for safe disposal, I have a car headlight bulb.  Not tried it with anything bigger than a 4S pack; I suspect 2 bulbs in series might be advisable for higher voltage packs to avoid damaging a nominal 12v bulb.

Yep, or just pop it in the model and run the motor for a couple of mins. Problem with the light bulb method is that if you get distracted then you could over discharge the battery. But I have one dual and one single charger so can put 3 batteries on storage mode at once.

[Fly Boy 3]

Thanks all for informative info.  Will be buying new Lipos soon and I hope I can look after them better. Do new Lipos arrive in storage voltage ?  Thanks

[David Holland 2]

I do as Frank does. Connect with a wattmeter in series and run at about half throttle down to about 3.8 volts, which will recover slightly when off load. Obvious safety precautions apply

[David Holland 2]

PS. After a couple of years of getting involved in electric flight I adopted a more disciplined regime for the use of my lips, i.e. dropping to storage voltage if not used in a particular flying session and they now last and perform much better.

[Fly Boy 3]

As Lipos come with different plugs, are adapters a good or not so goood thing ? Thanks

[Bruce Collinson]

One more point of potential failure plus they take up room in smaller fuselages.   Why not standardise connectors across your fleet, e.g. XT 60 for anything upto 4S then XT90 anti-spark for 5S and above?   My LMS changed a dozen Deans to XTs for the cost of the plugs and they are much better at soldering than me, although I still had the sockets to do on the ESCs.

 

This might spark off another debate on connectors but I find XTs best for numerous reasons.

 

BTC

[Simon Chaddock]

A LiPo has a limited cycle life particularly the way we use them. They also deteriorate faster if left at high charge.  They also deteriorate simply over time.

So it comes down to which of these parameters, or combinations of them is going to have the biggest impact on the useful life of your LiPo.

As it so much depends on how you use them there is no "right" answer.

 

As a relatively low rate user on each of my LiPo I am always conscious that if I charge and then discharge it to storage unused that is one cycle used but the battery can then be safely left for an extended period. 

 

Adaptors are not "good" in a high current situation due to possible increased contact resistance but this potential penalty has to be traded against the benefit of convenience. Again no "right" answer 

 

[MattyB]

This thread seems to come up about every 2-3 months! Anyway, here is my std recommendation - don’t use the discharge function on your charger (too slow and increases likelihood of a charger failure), but instead build a cheap discharge rig with 2-3 of these units wired in parallel…

 

 

[John Minchell]

Well I always have discharged any cells I use or ones that are still fully charged and didn't use back to storage charge.  Including the 150mAh 1s indoor cells.  I have not had to throw away any battery for over a year now.  However, since this cost of living crisis, I have been using the larger batteries 3,4,5 & 6 cells to charge up my phone, or tablet or laptop.  Since I have already paid the utility company to charge the battery anyway why waste it on storage charging the battery back to 40% and still paying to top up the phone/etc from the mains.  Works for me.

[Geoff S]

One of our newer members is retired and very enthusiastic. He lives near to the airfield and flies every day unless the weather is really bad (because I have a longer drive I only go if it's decent weather).  He puts a tick on his batteries for each charge (usually 4 to 6s large capacity) and I've seen upwards of 30 to 40 cycles on the batteries he uses a lot more than I do mine.  He also rarely uses the throttle except as a switch :).  He's driving his batteries hard. It seems that regular use is beneficial to longer battery life. 

[Engine Doctor]

13 hours ago, Geoff S said:

  He's driving his batteries hard. It seems that regular use is beneficial to longer battery life. 

Like most things , use it or loose it 😉. 

[EvilC57]

5 hours ago, Engine Doctor said:

Like most things , use it or loose it 😉. 

Certainly true of lead acid batteries in cars in my experience. A battery in a car used every day will usually outlive one in a car only used occasionally.