Discharging LiPos to Storage Charge Level

[Tosh McCaber]

Don't know if anyone can help.

I've just bought an FD-200 discharger, on the advice of club-mates, who tell me that it is essential to store batteries at storage charge. 

https://www.amazon.co.uk/ISDT-Control-Battery-Balance-Discharger/dp/B07VW7HZLJ/ref=asc_df_B07VW7HZLJ/?tag=googshopuk-21&linkCode=df0&hvadid=501156581681&hvpos=&hvnetw=g&hvrand=5368442662330318663&hvpone=&hvptwo=&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=9046836&hvtargid=pla-823020257985&psc=1

I'm having problems (as several reviewers have pointed out) with the left hand button, which is somewhat non reactive and temperamental, not allowing various rates of discharge. However, I think that working it from the App for it will be OK.   I'll persevere a little before a decision to send it back to Amazon.

The instructions are not very clear.  To clarify a major confusion for a novice to batteries (me!), the discharger has, firstly, a selection of 2S up to 8S batteries (controlled by the temperamental button).  It also has various rates of discharge- ranging from 5 to 25 amps on the other button. (As well, there is obviously the C rating for the battery in the computation.) I don't want to discharge at a rate too high for the battery voltage and amp-hour rating 

To my question! 

Will I be safe to set a battery discharge rate to whatever the voltage (S Rating) the battery is, and then calculate the rate of discharge to make sure that it is below the Amp Hour rating x C rating for the pack?  For example, if I have a 2200mah 3S battery pack rated at 40-50C, I assume that, so long as the discharge rate is less than 2.2x40 = 80amps, I could select any of the discharge. But what safety margin should I use?

[leccyflyer]

Tosh - I don't know who told you that you needed to blow £70 on a device to discharge your batteries when there are significantly less expensive and simpler ways to achieve discharging your packs to a suitable storage voltage. Most of my chargers have a discharge function, which can be used in the background when you are in the workshop working on something else. If your charger doesn't have such functionality then the simplest way is to just run the motor, with the model well restrained and a wattsmeter in the circuit until your pack has reached a suitable level - personally I like to store my batteries at around 3.8v/cell and that's about what I aim to land with.  

 

Think about it - when you fly your model for 5-8 minutes, your packs should be coming down at a decent storage level. The calculation that you are using to determine the discharge rate sounds like you will be caning the batteries and doing more harm to them than any perceived benefits of storing them in a discharged state. I bet none of your models are pulling 80amps on a 2200mah 3s1p pack. Take the C ratings on most batteries with a pinch of salt. You are far better discharging those packs at a very modest discharge rate <10amps is good, it just takes a bit longer. It looks like the device that you've bought has a maximum discharge rate of 25amps anyway, so that 80amps is a red herring.

Edited October 13, 2023 by leccyflyer
Clarification.

[Ron Gray]

Personally I charge my batteries, fly within them then leave until the day before I go flying again. If for some reason I don’t use the batteries (weather prevents flying etc) then the batteries get left until I do go out again. Now because I may chose to fly different models those batteries can sometimes get left in a charged state for a couple of months 😱 but they don’t seem to suffer and I’m including my 6s edf batteries in that statement. I know that this flies in the face of ‘good practice’ but it’s my own personal experience (circa 50 batteries in my ‘stock’).

[leccyflyer]

Ron - no issues from me leaving the unused batteries as they come back from the field for up to a couple of weeks, if I don't manage to fly again in that time. However having been bitten hard by the spectacular failure of some so-called intelligent drone batteries, which had their own internal self-discharge protocol, taking them down to a storage level, but then ultimately completely killing them, I'm taking a few additional measures these days. I'm very uncomfortable with the so-called intelligent battery management built into more recent Spektrum batteries, which automatically discharge the packs if not used for a few days. No thanks, I prefer to be wholly responsible for my own battery management.

[Phil Green]

1 hour ago, Tosh McCaber said:

on the advice of club-mates, who tell me that it is essential to store batteries at storage charge.

It isnt essential at all.  It helps their longevity if they're not stored full, but the actual state of charge for storage really isnt critical, anywhere around 2/3 capacity, so on your last flight of the day, fly roughly about a third of your pack and you're good.  Dont take them to storage level at 80 amps on a discharger, thats ridiculous! At that current your discharger cannot control cell balance because 80A is 200+ times greater than the typical maximum balance current, also it cant measure static cell voltage under maximum load.   One amp will take a full 2200 to storage in 45 minutes relatively safely, and the balancer should be able to make adjustments as it goes.  You can of course discharge without balance monitoring, but a bad cell could reverse and pop!

 

 

 

Edited October 13, 2023 by Phil Green

[Mark Turner 12]

Wouldn’t one of these charge and discharge to storage two batteries at once for less money?  https://www.modelsport.co.uk/product/skyrc-t100-dual-battery-lipo-balance-charger-444856

 

I have this one as we 12v batteries from a solar supply at the field and it does 12v and 240v input https://www.modelsport.co.uk/product/skyrc-d100-v2-ac-dc-dual-balance-charger-421359

Edited October 13, 2023 by Mark Turner 12

[John Lee]

On 2200MAh and up I discharge to storage at 6amps using the ISDT 100.

 

I do find it a very handy tool for battery management. I started using it some 6 years ago and developed a habit of returning all my batteries to storage voltage after every flying session, charging or discharging as required. It does seem to keep the batteries in much better condition than my previous rather casual approach and puffiness has been all but eliminated.

[Shaun Walsh]

5 minutes ago, John Lee said:

On 2200MAh and up I discharge to storage at 6amps using the ISDT 100.

 

I do find it a very handy tool for battery management. I started using it some 6 years ago and developed a habit of returning all my batteries to storage voltage after every flying session, charging or discharging as required. It does seem to keep the batteries in much better condition than my previous rather casual approach and puffiness has been all but eliminated.

Same here, 3Ah 3s battery discharged at 6 amp with an ISDT100 much quicker than discharging with my Radient Duplex charger which discharges 2 batteries at 0.8 amps each

[GaryW]

I use the Ultra Power 120AC Duo ( pic below)

 

I only ever charge all of my flight  lipos at 1C.... the night before I got flying as im doing right now ready for tomorrow & sunday

 

2150mah 2S = 2.1amp

2200mah 3S = 2.2amp

2800mah 4S = 2.8amp

 

All lipos the at the end of the day that have been used get charged as listed above for the following day then on Sunday evening all 2 3 & 4S lipos I use at the weekends whether they get used or not ALL get put into Storage Voltage whether they are fully charged or been used usually around 25% charge after use as listed below

 

2150mah 2S = 1.0amp

2200mah 3S = 1,0amp

2800mah 4S = 1,0amp

 

All lipos when not in use are always kept at Storage Voltage I NEVER keep lipos at Full Charge, Thats just asking for trouble keeping lipos fully charged  & All my Lipos are kept/stored in a metal fire proof box

 

 

 

Edited October 13, 2023 by GaryWebb

[Graham Bowers]

If you have a "sticky button" then it's a no brainer - return it.

 

However to your question about discharge rate. I have no idea what's considered best practice, however would have thought quite a bit lower than the in-flight discharge rate would be conservative. 5C or so with that type of equipment?

 

If I need to discharge batteries I use a couple of 12V 21Watt wire filament vehicle indicator bulbs soldered up in series for up to 6S batteries. I have a couple of those, and as I try hard not to bring charged batteries home, it works for me. I get them close enough using the bulbs, then a charger on "storage" setting to finish off to about 3.8V per cell, but the charger only pulls about 10 Watts so is much too slow for the whole job for big batteries.

 

I'll store batteries fully charged for no more than 2 days, otherwise pull down to storage. Although try to estimate how many I'll need at the field and charge an appropriate number. Before I knew about storage charge, I didn't bother, and killed a few packs. Not sure when they died as they were left for months.

 

 

[Ron Gray]

1 hour ago, GaryWebb said:

Thats just asking for trouble keeping lipos fully charged

My own experience says otherwise!

[Shaun Walsh]

23 minutes ago, Ron Gray said:

My own experience says otherwise!

Probably depends on the lipo.

My first set of lipo batteries were stored fully charged over one winter as I knew no better, most are severely compromised, effectively useless apart from low current applications and one became spherical when I charged it.

Edited October 13, 2023 by Shaun Walsh

[GaryW]

27 minutes ago, Ron Gray said:

My own experience says otherwise!

 

You may have a rather different view if you have one suddenly go up on you

[GaryW]

 

[GaryW]

 

[GrumpyGnome]

I'm with Ron.

 

I charge and go fly.  If I don't use them, they stay charged. If I do use them, they stay as discharged as when they came out of the plane.

 

I've never deliberately put a LiPo to 'storage' charge.

 

The two issues I had were pre-balance charger events, when charging.

 

It should be said that it's not often that a week goes by without me using them......... although the other day I needed to swap out the battery on my starter as I'd broken off one of the balance leads.  I grabbed a 4S LiPo from the stash that had last been used about 18 months when I trashed my last 4S plane, to find it practically fully charged (and with beautiful square corners).

 

We should do what works for us, and treat them with respect, but not fear. As I have said many times, I don't have big, or expensive packs, and I don't try and extract 100% of power from them, and I always charge at less than 1C.

[Ron Gray]

9 hours ago, Shaun Walsh said:

Probably depends on the lipo.

My first set of lipo batteries were stored fully charged over one winter as I knew no better, most are severely compromised, effectively useless apart from low current applications and one became spherical when I charged it.

I have 2 5s 5000 packs that were fully charged over 2 years ago (they were in my ammo box for 5s packs and I didn’t realise they were charged). I put them in the model they were meant for as a 10s pack and happily flew with them with no issues and they were then charged and ir checked, results? No different from when they were first bought! They are HK Zippos.

[Ron Gray]

9 hours ago, GaryWebb said:

 

You may have a rather different view if you have one suddenly go up on you

True, but I’ve been using my somewhat extensive range of Li-Po batteries (at a guess in excess of 50) over the last 8 years + in this way (and some of the batteries are that old). Li-Pos can catch fire even if they are correctly stored, but one thing I do do is that if one gets really puffed through use (in my case I’ve had maybe 5) I fully discharge them and dispose.

 

I’m not saying I’m right and the science is wrong but each to their own.

Edited October 14, 2023 by Ron Gray

[Ron Gray]

9 hours ago, GaryWebb said:

 

Oh I have experienced a LiPo fire, it happened on my way back from the flying field. I had left a battery in the trailer and on the journey home, what with the bouncing of the trailer the starter motor’s aluminium cage must have punctured the LiPo. The trailer has a hinged, sealed lid so I had no idea what had happened until I got home and opened it!

[Frank Skilbeck]

10 hours ago, Shaun Walsh said:

Probably depends on the lipo.

My first set of lipo batteries were stored fully charged over one winter as I knew no better, most are severely compromised, effectively useless apart from low current applications and one became spherical when I charged it.

Yep, I never used to bother discharging fully charged batteries, but after a couple of 6s 5000 lipos lost capacity and increased IR after being left for a few months, so now I do discharge to storage level if I'm not going to use them for a couple of weeks, excessive maybe, but both my chargers have this feature so easy to do.

[leccyflyer]

That's just about where I am now Frank. If there's a prolongued period of bad weather forecast and I haven't flown out the packs I took to the field, after a couple of days I'll put the larger packs on a discharge via the charger at 3amps, whilst I'm in the workshop. Like you said easy to do.

[Ron Gray]

Do you discharge multiple packs in one go? 

[leccyflyer]

No, just one at a time -it's just gently going away in the background, whilst I'm doing something else in the workshop. When the pack is down to 3.8v/cell the pinger goes off, I swap the pack for the next one and update the Lipo Charge State on the whiteboard. I can tell at a glance which packs are charged and pick the aeroplanes of the day on that basis.

[Cuban8]

All of my chargers have a discharge/storage setting but I never use it. As has been said, I either store the batteries discharged after flying, usually with about 20% charge remaining or just run an unflown  battery in a model for a few minutes until my checker widgit reads 20% or so.

I never saw any fall off in performance with batteries that were left fully charged for ages, but I wouldn't store batteries like that any more. Far better to keep them at a safe discharge level and hence containing much lower levels of energy in the event of a fault, so a better chance of containing a fire with the right precautions.

[leccyflyer]

Having been a charge at the field and leave the batteries as they are from one session to the next practitioner for many years, I've had to modify my charging regime as the time to charge at the field is now much more limited - with a 90 minute+ drive to my old club field, waiting half an hour with two chargers working to start off the first few packs eats into the time too much. I still don't like to have all my batteries at storage voltage and for my smaller packs I don;t bother discharging them - they get cycled much more frequently in use than the larger packs.

 

I'd intended going flying this afternoon, but the wind got up this morning and it's now blowing a hooley. Then still having two sore arms from my jags yesterday, I've just been stung on the ankle by a massive wasp -in October! Very painful. So I'm feeling a bit sorry for myself and am down to a single unpunctured limb 😞. Forecast is a little bit better for tomorrow, so some of the charged packs will get used, hopefully.

 

Here's the current Lipo Charge State board, showing how many packs are charged, since my last flying session on Monday last. It's a whiteboard, so is updated daily - the tally marks keep tags on how many packs are charged. The printed sheets list some of the models that are in service, colour coded by their preferred pack and which transmitter that they are assigned to. Bottom right of the whiteboard has the  selection of aeroplanes for the day listed, to help make sure that I don't leave any at home - that's also weather and field dependent. It'll do for tomorrow morning instead.