ISDT and SMART chargers - what charge rate can I safely use on my 4S batteries

[toto]

OK ..... back to something I don't really understand but have been promising myself that I would get a grip of.

 

Charging batteries.

 

I currently ( excuse the pun ) work of two main chargers.

 

An ISDT K2 Air

A SMART S2200 G2

 

both are twin port chargers.

 

I am ( as we speak ) charging some of the following battery types

 

Volts 14.8 volt 30C 4S 3300 mah Lipo

Seee 14.8 volt 50C 4S 3300 mah Lipo

 

Normally I have the chargers set to a very safe 1.0A charging rate but noticed that when I switched on my SMART charger, one of the port settings was set to 5.5A charging rate.

 

Is this ok for the battery types above. I have ..... just for the hell of it set both the SMART ports to 5.5 A as I am sure that this is a reasonable charging rate for the batteries but just wanted to check. I am ..... as always..... baby sitting the chargers in my shed as the batteries charge.

 

any quick answers ...... before my shed burns down ...... would be great ...... cough ... cough .... that smokes getting pretty thick ....😆

 

cheers

 

toto

[Richard Wills 2]

standard charge rate of 1C would be 3.3A on those batteries.  Personally I charge at 3C (9.9A on those batteries) which I consider safe, but make your own mind up on going higher than the 3.3A 1C charge rate

 

Edited May 5 by Richard Wills 2

[toto]

Thanks Richard,

 

they have just finished at the 5.0A rate with no issues. I really need to get a better understanding rather than the ..... try it and see approach that I just adopted. .... very risky.

 

However the charge rates on some of these chargers .... intended for up to 6S batteries goes up to 20A.

 

I had heard folks doing 4S batteries at 5.0A without incident .... but the " law of rumour " isn't a great one. The " playing it safe at 1.0 A " approach isn't great either one either as it leads to ridiculously long charging times. 

 

At least I am starting to look into it though ...... got to be a good thing.

 

Toto

[Richard Wills 2]

Until your have done some research into it, best to stick with the 1C rate and you won't go wrong. (1 x the capacity in ah, so 3300 mah is 3.3A charge rate).

[Chris Walby]

From the top.

 

It does not matter what the cell count is with regards to the charging rate e.g. 6S2000 (IMO should be charged at 2A, as in 2000 mAh) but a 3S5000 should be charged at 5A.

So cell counts for nothing, but what your charger needs to be set to, although I have some chargers that auto detect cell count so I just set the charge rate.

 

Note

A few people (inc Richard) charge their packs at a higher rate than 1C or the rating of the pack e.g. 4S4000 (4000 mAh = 4A for one hour) so 3x 4A = 12A and if you check your manufacturers information it may well say it can be charged at a higher rate than 1C (universal conservative value). The interesting point is how far they discharge their packs as they are still getting plenty of cycles out of them

 

Don't with lipos (speaking from experience!

• Don't discharge lower than 30% capacity
• Don't discharge at very high rates >50C, tricky with edf's but just don't keep it WOT for the entire flight!
• Don't operate lipos that are cold e.g below 15C

 

There is an opinion that if you discharge at 50C then you should be able to charge at a much higher rate than 1C 

 

I am intrigued as to why you think its safer to charge at 1A as opposed to 3.3A when you can discharge the packs at 99A and 165A (theoretically)? 

 

Edited May 5 by Chris Walby

[Ron Gray]

I now also charge my LiPos at 4C but only charge to 4.17 per cell.

[toto]

Hi Chris ..... possibly my total misunderstanding of the whole subject. Hence the need to educate myself.

 

I thought that the lower the charge rate, the less stress or heat or whatever placed on the battery and the less chance of overheating or a fire. My very unknowledgeable mindset. hence .... potentially very dangerous to be messing with things I don't understand.

 

I will get my head around it enough to be able to operate as safely as possible given their potential for fires etc. 

 

I would like to be able to charge them at a rate that does not necessitate a sleep over in the shed though.😄

 

cheers

 

toto

[toto]

just caught your post Ron.

 

There you go ........ I am aware that you can ( on some chargers ) limit the voltage that you try to reach .... I think so that you don't overcharge. .... I have ( at the moment ) no idea how to do this.

 

I'm just dipping my toe in at the moment and my ability to take on some of this information is diminishing with age I think.

 

A City and Guilds in Electrical Installation ( from when I was in my teens .... not yesterday ) and an Honours Degree in Building Economics & Quantity Surveying I hope demonstrates my ( past ) ability to soak up relatively technical principles and jargon but I must admit ..... there is more flowing out than is flowing in. 😄

 

Hopefully I can retain just enough .......

 

toto

[GrumpyGnome]

toto, all sorts of useful information here ....https://forums.modelflying.co.uk/index.php?/forum/57-electric-flight-for-beginners/

 

John Smiths in left hand, type/scroll with right hand, read with eyes 🙂

[toto]

Thanks for the operating instructions tothelink Grumpy ..... much needed ..... 

 

Toto

[Richard Wills 2]

Whilst you are reading up Toto,  if you have several packs of the same cell count it may be worth looking at parallel charging.

[toto]

Is that when you use those extension board thingmies ? 

[Martin Harris - Moderator]

Don’t confuse charge current with C ratings.  Your 1A would be disastrous if you were charging a tiny 100mAh pack and ridiculously low with a 10,000 mah one. 
 

You need to base your charge rate on the capacity of the pack.  If you’re charging a 2200 mAh pack then your 1C rate is 2.2A - with a 5000 mAh one it’s 5A (I’m sure with your electrical background you’ll know that 5A equates to 5000 mA but some reading this may not).

 

Should you decide that your packs are capable of higher rate charging, simply apply this to the C rate required - so for a 3C charge, which will theoretically do a full charge in an hour divided by the C rate i.e. 20 minutes, your 2200 mAh pack would need to be charged at 6.6A

 

 

[Phil Green]

Chris is right, you seem to be relating cell count to charge rate:

>>𝘸ℎ𝘢𝑡 𝑐𝘩𝑎𝘳𝑔𝘦 𝘳𝑎𝘵𝑒 𝑐𝘢𝑛 𝐼 𝑠𝘢𝑓𝘦𝑙𝘺 𝘶𝑠𝘦 𝘰𝑛 𝑚𝘺 4𝑆 𝑏𝘢𝑡𝘵𝑒𝘳𝑖𝘦𝑠
>>𝐼 ℎ𝘢𝑑 ℎ𝘦𝑎𝘳𝑑 𝑓𝘰𝑙𝘬𝑠 𝑑𝘰𝑖𝘯𝑔 4𝘚 𝘣𝑎𝘵𝑡𝘦𝑟𝘪𝑒𝘴 𝘢𝑡 5.0𝘈 𝘸𝑖𝘵ℎ𝘰𝑢𝘵 𝘪𝑛𝘤𝑖𝘥𝑒𝘯𝑡 
 ... when in fact the cell count takes no part in your charge calculations...  if you had two 1Ah packs, one is 6S and one is 2S, a one amp charge would charge either in an hour, two amps would do it in half an hour, three amps would charge them in 20 minutes, four amps 15 minutes and so on.  Cell count doesnt come into it 🙂

Your 3.3Ah packs (regardless of cell count) will charge in an hour at 3.3 amps. Or half an hour at 6.6 amps. 

time-to-charge=capacity/current

 

Not sure if I'm helping or causing further confusion  🙂

 

Cheers

Phil

 

[Peter Christy]

1C charging (ie 2.2A for a 2200 mAH pack, or 5A for a 5000mAH pack) should always be the safe option. Charging at higher rates is possible, but can shorten the life of the packs - which is short enough already, considering the price! Personally, I would be reluctant to go beyond 2C for safety reasons and normally charge at 1C.

 

Even at 1C it is possible for a pack to burn, though this shouldn't happen unless its been damaged. I'm always very wary of packs that show signs of significant puffing.

 

Remember, these packs contain a LOT of energy for their size, and releasing it all at once is likely to be catastrophic! Treat with respect!

 

--

Pete

 

[John Lee]

Agreed Pete.

 

All batteries are not the same & I'd be weary of applying generic advice to specific batteries when thinking of charging at more than 1C.

 

Every battery comes with an information & safety leaflet specific for that battery (or at least it should do). All I have seen have stated the maximum charge rate which should be observed. They are usually stated such as 1C, 2C, 3C etc, and may have warnings that the higher charging rates may shorten the battery life. 

[Phil Green]

14 hours ago, Phil Green said:

...  if you had two 1Ah packs, one is 6S and one is 2S, a one amp charge would charge either in an hour, two amps would do it in half an hour, three amps would charge them in 20 minutes, four amps 15 minutes and so on.  Cell count doesnt come into it 🙂

Your 3.3Ah packs (regardless of cell count) will charge in an hour at 3.3 amps. Or half an hour at 6.6 amps. 

time-to-charge=capacity/current

 

Sorry this wasnt meant to imply that you should generally charge at over 1C it was just a failed attempt to explain the maths and the irrelevance of cell-count.
I fully agree with Pete & John. I'll get back in me box... 🙂
 

Edited May 6 by Phil Green

[Engine Doctor]

Ive always charged my batteries at 1C . Recently at  our club field a new member who had been a model car enthusiast said he regularly charges his pack at 3 or 4c and never had an issue. He said the batteries last just as long as those that are charged at 1C. 

I have set aside a couple of packs that I use on cheapy models and will charge them at 3C and seehow they stand up to it. 

Not very scientific but i will get a real world idea. Oh and they will be charged out on the drive .....just in case 😉 .

[Richard Wills 2]

A couple of years ago I made a mistake charging at the field and forgot to change the charge current from the 25A I had used at home to parallel charge.  I charged a 6s 1300 mah quadcopter pack at 25A, over 19C!!  I knew something was up when after 3 mins the charger started beeping to tell me balance charge complete!  I am now far more careful with setting the current, but pack is still going, albeit performance has now dropped off a little. just replaced it this year after hundreds of cycles  being charged at 5C.

[GrumpyGnome]

There's quite a long thread on this forum about field charging at >1c, and some good information about longevity.  In a nutshell, charging at >1c does less damage than charging to 4.2v, and deeply discharging them....

 

Having said that, I have never charged at >1c, generally around 0.8c. I'll take around 15 packs to the flying field - charged at home using multiple chargers (incl 4 x 2200 3S parallel charged). I never field charge. Usually, my charging occurs outdoors on a concrete hardstanding. I'll prep my models and bag, and drink coffee, for the hour or so it takes to charge. I am lucky that I rarely need to discharge/storage charge.

 

As with most things in this wonderful hobby, there are multiple ways to skin the cat in question....

[toto]

What exactly is parallel charged ?

 

Toto

[toto]

Another point ......

 

I do have quite a few batteries in different states of charge. Many of them over 3 / 4 charged. 

 

Whilst playing around with my chargers I came across " storage " in the menu. I presume this is to take the battery either up or down to a storage charge.

 

Is it simply a case of plugging the batteries in and hitting the storage button and the charger does the rest. Also ...... do you have to set the rate at which the charger will achieve this ? ..... similar to selecting the rate at which the battery charges.

 

I do have loads of various size batteries and would like to get them to their optimum level for storage to lessen the chance of knackering them due to non use. I find that I am only using my 4S 3300 mah at the moment for my supercub whilst training.

 

I have loads of 3S and 6s batteri3s that won't see the light of day for some time ......... don't ask why I charged them in the first place.

 

How long will the batteries hold at the storage level forbefore you have to top them up ?

 

Toto 

Edited May 6 by toto

[leccyflyer]

Toto

 

I'd suggest that, as you are relatively inexperienced and have lots of other things to get up to speed on, that you limit your battery charging to the easily understood and conservative 1C charge rate, Parallel charging, charging at several C and other more sophisticated methods are best left for when you have some experience of safely operating battery charging and storage.  I believe that I did remark that jumping right in at the high energy 6 cell end of things, without having built that experience, would be a steep and potentially expensive learning curve. Most folks start electric flight with relatively modest power trains and smaller batteries, then work up to the meatier packs.   As you have quite a few largish packs - 6s1p 5000mah packs IIRC then you might also like to use the storage function on your charger to keep these at the storage level of around 3.8v/cell. That has benefits in helping cell longevity, since packs, especially larger packs, stored fully charged for any significant length of time - weeks or months do definitely have reduced lifespans. That is well established.

 

You can set the same rates for your Storage function as for charging - namely 1C  to take packs up to that storage voltage that might have dipped below 3.7v/cell. There are other means of taking the batteries down to a safe storage charge if you haven't used them at the field, or you can set your storage discharge on your charger to a higher rate than you would normally charge at. The best way to take your packs to storage charge level is to fly them - you aren't wasting any of the pack's lives then!

[toto]

Hi Leccy,

 

I'd agree about discharging by actually using the model but it's u likely that the models ..... for example .... for my 6S's are my Beaver and my Twin Otter which are both built but u li,Ely to fly as I am already sticking to the very good advice given about learning and sticking with one model at a time ..... currently my super hero the Supercub.

 

I could set up the twin otter in my back garden on a bungee and just turned the throttle up but not ideal in full view of my very inquisitive ( and dodgy ) neighbours.

 

I also bought a load of 3S batteries destined for two gliders as I had been considering looking at hitting the slopes as a means of getting stick time. .... So bought some appropriate batteries with that intension but it never materialised. No harm the batteries will keep but they have been charged fully. I need to check their current levels.

 

I know I have jumped in on various occasions ( as I am sure all will agree with ) but I have slowly learned to calm down a bit. However, I am where I am and just trying to get to the b3st position with currently redundant batteries. I think, one way or the other, I will start to reduce or increase the batteries that are less likely to be used anytime soon and hopefully remove them from the back of my mind ..... for  a while at least until they are needed.

 

Does that sound reasonable ?

 

Toto  

[leccyflyer]

Aye, that sounds fine.

 

It is what it is - your discharge function on the ISTD charger will take them down beautifully to a storage charge level, it will just take a bit longer for the larger batteries.

 

If I really need to discharge a pack, I just set up the fuselage in the model stand, put the battery in and run it at half throttle for five minutes or so. I have the battery meter connected to the balance lead so that I can see what per cell voltage I am taking them down to. With the model well restrained, held secured with my hand and sitting in the stand, from a position behind the model well away from the prop arc it only takes a few minutes - but you do need to be very careful running motors in the workshop like that.  You also need to ensure that there is sufficient colling to motor, ESC and battery.