6S8P Li-Ion high-C LiPo field charging solution in a case (fly all day on two LiPos)

[Duncan Disorderly]

1 hour ago, Philip Lewis 3 said:

I do recall that charging to 95% according to the information should double the amount of charging cycles a pack can take before it becomes of no more use

 

I've just had a quick check of my logs (shout out to leccyflyer's current topic!) and the 4 Zippy batts in my 1st post have each had 333 cycles in just one plane (Pilot NG, 1332 flights) in the last 30 months, plus whatever else they've flown on top of that. They've never seen 4.18v. They haven't had much of the 4C charge treatment yet though - all of that has been on the 3300s @ 125 cycles each over the late autumn & winter.

 

When I started in 2015 I used to think I'd be happy if a LiPo lasted 100 cycles. Clearly that requires updating! At the very least, those £40 Zippy packs have done 400 flights each so I'm very happy at 10p per flight (+2p per recharge) - and that's assuming that they've all died today, which they haven't. They appear to be in better condition now than they've ever been. I can't explain it but I'm beginning to think some of the golden rules need updating, or relaxing a little. I think the 4.17v max charge is a lot of it, and the best thing about that is it makes absolutely no difference at all to your flight time, because if you're flying your batts down to the last 0.03v then that's why your batteries are knackered.

 

Does anyone else have an opinion on them only being fully charged for 10 minutes, or is that a red herring? Chemistry was never my strong point but if you took the mantra of "don't leave them charged up" to its logical conclusion, you'd only charge them immediately before use. I didn't really set out with doing that in mind, it's just a by-product of the new routine. But I like it.

 

Two other things occur to me:

 

I like to have at least 6 flights, which meant 6 packs. Then when I started flying 12S it meant 12 packs, which could cost almost as much as the plane. It was a bit like running a care home for batteries too. Now 4 packs get me a whole day at the field flying 12S. If the new routine happens to be a better way of managing them then that's a win-win. We'll see if the high C charge rate kills them but I've done 125 charges on each 3300 pack now, and they had a couple of hundred cycles on them at 1C to begin with... how many cycles do you want for £50? If you do fewer flights of a day then just knock the charge rate back to suit your style of flying. Often there's only Russ & me at the patch so we like to bang out the flights alternately (so we could actually get away with just one/one set of batts, rather than two). If your circumstances only allow one flight an hour then you can do this and still stay at 1C. The extra available speed is there if you need it.

 

I can't explain enough how useless I am at making things, so if anyone is sitting there thinking "It's all well and good for him being able to do that" then think again. I was insanely proud of myself that day. I'm not even very good at assembling ARTFs. I'm quite a good pilot though!

 

[leccyflyer]

That's a great post and I'm getting the feeling that this could really be a game changer for the larger models - those with 6s1p and larger capacity packs - with actual cost savings in terms of battery purchasing, beyond the initial set up costs. I'd have to look deeper to see if that was practical or desirable for the smaller pack, of which I've got loads in use. Those are very impressive stats on the total number of charge cycles that you are getting on what are essentially budget, rather than high end, expensive packs.

[Duncan Disorderly]

4 hours ago, PeterF said:

Well the strategy is that I keep them at storage charge and at that charge I can take them to the field and use them for a flying session using my normal sized planes. However, if I go with a larger plane (largest is Tony Nijhuis Vulcan using 2 x 8S 6,250mAh) I charge the field pack up in the morning. I have a 40A charger so I can get it from storage to full in less than 1 hour at the same time as charging the batteries to take with me, load the car etc etc.

 

That's a cunning plan. It didn't occur to me to go big on mAh and leave them at storage voltage, which would still give many charges due to the mAh "overkill". And a quick charge of a morning if it's going to be a heavy day. Brilliant. Totally gets around the storage charge problem, which my brain was too small to conquer.

 

I love how this thread has brought all these different strategies to light!

[Geoff S]

You've inspired to tear apart a 10s cycle battery that fitted on a bike I no longer have and converted back to standard before I sold it.  It's full of Samsung CR18650 Li -ion (as opposed to Lithium Iron -LiFe? Battery chemistry isn't my strong point!)  They would have been wired a 10s5p (there's 50 of them).  Interestingly, it looks as though the built-in charger, driven from a simple mains to DC 'charger', appears to balance charge the batteries. 

 

Hopefully, I have the makings of a portable energy source to use at the field.  I don't know why I didn't think of it before!  How should I wire them, bearing in mind my iCharger is only good for 8S?  I usually (always) drive my charger at 12v but it's OK up to 24v.  Probably 4S would be enough but that would mean 10/12 in parallel. Is that a disadvantage?

 

Thanks to DD for starting me off on this track.

 

 

PS

The cells are at 3.5v each (35v for the whole pack), which is comfortably above the safe minimum of 2.4 to 3.0. Hopefully, they'll do the job.

Edited January 24 by Geoff S

[Duncan Disorderly]

7 minutes ago, Geoff S said:

You've inspired to tear apart a 10s cycle battery that fitted on a bike I no longer have and converted back to standard before I sold it.  It's full of Samsung CR18650 Li -ion (as opposed to Lithium Iron -LiFe? Battery chemistry isn't my strong point!)  They would have been wired a 10s5p (there's 50 of them).  Interestingly, it looks as though the built-in charger, driven from a simple mains to DC 'charger', appears to balance charge the batteries. 

 

Hopefully, I have the makings of a portable energy source to use at the field.  I don't know why I didn't think of it before!  How should I wire them, bearing in mind my iCharger is only good for 8S?  I usually (always) drive my charger at 12v but it's OK up to 24v.  Probably 4S would be enough but that would mean 10/12 in parallel. Is that a disadvantage?

 

Thanks to DD for starting me off on this track.

 

 

I have no idea! As Ian Dury once sang... "Don't ask me, I'm an idiot I'm afraid". But it certainly looks like you have the makings of a decent amount of energy storage there. No disadvantage to have fewer in series and more in parallel but a 5S10P configuration would use them all up and maybe even mean you could leave them in those nice holders. Mine's powering a pair of chargers so I thought 24v would hold up a bit better under load. The Li-ion charger just sees it as a massive 6S LiPo for charging (yes, a LiPo not a Li-ion - set with a 4.16v cutoff). Rather amusingly, given how I've been banging on about charging at high C rates, my home charger dribbles out a rather feeble 4A, so I'm recharging the Li-ions at a vertigo-inducing 0.1C

 

Glad it's inspired you. I've been inspired in turn by what everyone else is doing. All these brilliant methods that people have come up with. Seems like the lead acids and the generators can be pensioned off, other than for permanent sites.

 

[Duncan Disorderly]

1 hour ago, leccyflyer said:

That's a great post and I'm getting the feeling that this could really be a game changer for the larger models - those with 6s1p and larger capacity packs - with actual cost savings in terms of battery purchasing, beyond the initial set up costs. I'd have to look deeper to see if that was practical or desirable for the smaller pack, of which I've got loads in use. Those are very impressive stats on the total number of charge cycles that you are getting on what are essentially budget, rather than high end, expensive packs.

 

Yes, I didn't realise I was getting so many cycles, though I'd noticed that I hadn't bought any LiPos for ages. Good job I keep a log! Without it I'd just have to guess, which would be useless as evidence.

 

I'd say it'd make sense for anything 4S or above if you need more than 4 of them. The £285 includes a £55 charger so knock that off if you already have something you can use at the field. For anything using packs in series it's a no brainer. Last summer I was flying 12S and 10S planes on the same day, 6 flights on each, 24 batteries to fettle. It was getting ridiculous!

[Philip Lewis 3]

1 hour ago, Geoff S said:

 Interestingly, it looks as though the built-in charger, driven from a simple mains to DC 'charger', appears to balance charge the batteries. 

 

Hopefully, I have the makings of a portable energy source to use at the field.  I don't know why I didn't think of it before!  How should I wire them, bearing in mind my iCharger is only good for 8S? 

 

 

 

 

I would do exactly the same as Duncan so you have 6 cell 8 Lithium Iron Pack, you don't want or need any more than 24 volts output especially as your current charger has that as a maximum input voltage, your charger only then needs to charge a six cell pack and you will have two spare cells left over.

 

If there is a BMS board wired up (highly likely and that would be why the charger is a simple DC input), you will need to disconnect it as it's for a ten cell pack which it won't be anymore, just balance charge it by  wiring in a balance lead as shown in DD's photo's and balance charge it. 

[Philip Lewis 3]

1 hour ago, Duncan Disorderly said:

Rather amusingly, given how I've been banging on about charging at high C rates, my home charger dribbles out a rather feeble 4A, so I'm recharging the Li-ions at a vertigo-inducing 0.1C

 

 

So a charge time of ten hours from flat, and of course you wouldn't dream of leaving it charging unattended would you? 😁

[Duncan Disorderly]

2 minutes ago, Philip Lewis 3 said:

So a charge time of ten hours from flat, and of course you wouldn't dream of leaving it charging unattended would you? 😁

 

What, me? 😇

 

I did attend the first couple of charges, mainly because I did the soldering... But I normally charge inside a metal filing cabinet in a tiled room in a semi-derelict house (because I spend all my money on damned LiPos!) and that's about as good as it's going to get. I've seen the hideous pics but I've also poked a fully charged LiPo with a sharp stick until it blew up, then assessed what my risk was, several times over the years. It takes a surprising amount of poking and produces a hell of a lot of smoke but I'm not having much success in making them flare up like torches, even when I pierce several cells at once. Many, but by no means all, LiPo fires are down to parallel charging and/or not balancing, so I avoid both of those. Knocking the max voltage back a notch must help a little bit too. I also set timers to cut the charge off after a certain period regardless of charge state, and rubber band together each charge + balance lead from the 4 port chargers so I can't inadvertently cross-wire balance and charge leads across the ports.

 

I have an old outside loo that I dream of converting into my battery emporium! The thing is, if this works as it appears to work, I'm going to have an awful lot of batteries for sale and no need for the emporium.

[Philip Lewis 3]

20 minutes ago, Duncan Disorderly said:

It takes a surprising amount of poking and produces a hell of a lot of smoke but I'm not having much success in making them flare up like torches, even when I pierce several cells at once.

You're just not trying hard enough, 😂try connecting a six cell pack in parallell with an eight cell pack and stand back and see what happens! (don't ask me how I know).

 

Li-ion and LiFe a lot safer than LiPo though.  

[Duncan Disorderly]

 

This is the pair of Turnigy Heavy Duty 6S 3300 60C batteries that drew the short straw and are currently being subjected to my brutal charging regime. I was expecting them to at least puff a bit. The one side that looks a bit out of shape has got fluffy velcro on it. Reminder - they'd each had somewhere around 200 charges at 1C before having 12 amps stuffed into them 125 times. I was trialling one of them at 15 amps but couldn't bear it any longer (me, not the battery). IR constant at 1.2/1.3 per cell whenever I get to measure it at the same temp and SoC, so I'm not noticing any degradation despite my sadism. They're used in several planes so the previous flight data is a bit trickier to extract with my simpleton logging system, but the 12A x 125 is accurately logged cos it's part of The Great Experiment.

 

 

[Geoff S]

Having dismantled the surplus Cycle battery pack, I configured the batteries as best I could to convert the arrangement from 10s5p to 5s10p. I kept the battery holders, partly for convenience and partly because it would be difficult to extricate them without the risk of damage or inadvertent s/c (I've had a couple of those, hopefully without damaging the cells. At least it showed the cells had stored energy!).

 

I found an underused aluminium case which has an insulated lining and they fit a treat with the cells held on a 3mm plywood base.  I intend to make a ventilated box to keep them in place and that leaves plenty of space for my  iCharger 308 Duo.  I can't think why I didn't think of this before.  Assuming it works, of course!

 

 

The wiring is less than optimal but I had to go with how the batteries had been configured before dismantled the original.  I've ordered a 5s balance connector for charging the pack and I'll install 2 pairs of 4mm sockets for output and probably use for charging, too. 

 

The idea is to fit a vertical 3mm ply wall which will carry the output sockets and a ventilated lid. Not sure if ventilation is necessary - the original case had none.  Is an output fuse a good idea or overkill?  It weighs a fraction of the old lead/acid car battery I'd given up using because of the physical effort needed to carry it (and the danger of acid spill - our old Ford van which dad used for his accumulator round during WW2 had a wooden floor, eaten away by acid, as was the overall coat he wore 🙂 )

 

I was puzzled by this inlay in the 3mm ply. It's part of a brand-new sheet I bought from SLEC some years ago

 

 

It's roughly 35x25mm

Edited January 25 by Geoff S
grammar!

[Outrunner]

41 minutes ago, Geoff S said:

was puzzled by this inlay in the 3mm ply. It's part of a brand-new sheet I bought from SLEC some years ago

 

Probably where there was a knot or fault in the wood. Often lengths if wood and dowel are joined together like that if you go to the DIY sheds.

[Geoff S]

5 minutes ago, Outrunner said:

Probably where there was a knot or fault in the wood. Often lengths if wood and dowel are joined together like that if you go to the DIY sheds.

 

Yes, but this is in the middle of a sheet. It's a perfect fit and doesn't compromise the use of the sheet but it's so well done and must cost some time.  I'm just surprised they bother repairing rather than scrapping a short section.

[Duncan Disorderly]

1 hour ago, Geoff S said:

Having dismantled the surplus Cycle battery pack, I configured the batteries as best I could to convert the arrangement from 10s5p to 5s10p. I kept the battery holders, partly for convenience and partly because it would be difficult to extricate them without the risk of damage or inadvertent s/c (I've had a couple of those, hopefully without damaging the cells. At least it showed the cells had stored energy!).

 

I found an underused aluminium case which has an insulated lining and they fit a treat with the cells held on a 3mm plywood base.  I intend to make a ventilated box to keep them in place and that leaves plenty of space for my  iCharger 308 Duo.  I can't think why I didn't think of this before.  Assuming it works, of course!

 

 

The wiring is less than optimal but I had to go with how the batteries had been configured before dismantled the original.  I've ordered a 5s balance connector for charging the pack and I'll install 2 pairs of 4mm sockets for output and probably use for charging, too. 

 

The idea is to fit a vertical 3mm ply wall which will carry the output sockets and a ventilated lid. Not sure if ventilation is necessary - the original case had none.  Is an output fuse a good idea or overkill?  It weighs a fraction of the old lead/acid car battery I'd given up using because of the physical effort needed to carry it (and the danger of acid spill - our old Ford van which dad used for his accumulator round during WW2 had a wooden floor, eaten away by acid, as was the overall coat he wore 🙂 )

 

I was puzzled by this inlay in the 3mm ply. It's part of a brand-new sheet I bought from SLEC some years ago

 

 

It's roughly 35x25mm

 

 

That looks fantastic! I wish I could get around to things as swiftly as that.

 

The fuse is overkill. I did it because I just copied Russ's and even he said it wasn't necessary, just dotting the Is and crossing the Ts.

 

Let us know how you get on with it.

 

That inlay is weird! Maybe laser cut in before the sheey of ply was laminated up?

 

[Geoff S]

Got it finished today but not without some hitches.  I wired it fully and started to charge it but one cell (actually 10 in parallel) had very high resistance and once the 5 amp charge started had a much higher voltage than the others (probably because of the high IR), Fortunately it was at the end of the line and I opted to remove it electrically and go for a 4S10p battery - still more than capable of supplying my iCharger.  The balance connectors I ordered arrived so I've connected the last 2 wires (the most positive) to the same place. I still plugged it into the 5S socket, but it thinks (quite rightly) that there's only 4 in series, and it all charged OK.

 

I have another 'scrap' cycle battery that I replaced for my wife because of its intermittent operation.  The batteries may well be usable, so all is not lost.  I may make up a flight pack and try it in a model - more watt hours than a LiPo and capable of delivering a lot of current.  It will need some investigation.

 

So here it is.  I decided not to vent the ply retaining box because there are lots of bare connections in there and I didn't want to risk dropping a tool and shorting out parts of the battery. I may try and find some close plastic mesh if there's a problem.  All I need now is some decent weather for my old bones 🙂

 

 

The balance has stress relief inside by holding it with tie wrap.  The connection from the battery to the 2 terminals is able to be released as I've included 4mm bullet connectors.

[Andy J]

Out of interest what type of charger is used to charge the main battery packs. Also what electrical configuration is given to a BMS to avoid issues whilst charging the main pack. Only ask as one continues to see many household fires started by people charging large packs for e-bikes etc.

[kc]

21 hours ago, Geoff S said:

I have another 'scrap' cycle battery that I replaced for my wife because of its intermittent operation. 

" intermittent operation"  - dinners late again?     Geoff I had to laugh at that!   Sorry!  

[Geoff S]

1 hour ago, Andy J said:

Out of interest what type of charger is used to charge the main battery packs. Also what electrical configuration is given to a BMS to avoid issues whilst charging the main pack. Only ask as one continues to see many household fires started by people charging large packs for e-bikes etc.

 

When the battery is charged on the bike, there's a simple mains powered 42v rough dc source connected straight to the battery case.  Inside the battery case is a balanced battery charger for the 10s5p Li-Ion battery.  My modified battery to use for charging at the field is 5s10p (now 4s10p, because of one faulty 10p pack) and I charge that with my iCharger in Li-Ion mode.

[Andy J]

Duncan, did you fit or use a BMS for your home built battery packs to monitor the pack during charging? 

 

Looking at some of your pictures  I can see there is a voltage monitor connection against each string of interconnected cells but I fail to see how this would protect against one of the cells breaking down and demanding more current resulting in the other parallel connected cells receiving an over charge and hence possibly getting hot or catching fire.

[Geoff S]

BMS?

[Philip Lewis 3]

BMS = Battery management system. Onboard internal balancing circuitry. 

[Geoff S]

2 minutes ago, Philip Lewis 3 said:

BMS = Battery management system. Onboard internal balancing circuitry. 

 

Thanks, Philip. 

 

@Andy J Other than the balance connector, does any battery we use have anything more sophisticated?  It's quite complicated to monitor the current delivered or drawn from every cell in a battery.

[Duncan Disorderly]

23 hours ago, Andy J said:

Duncan, did you fit or use a BMS for your home built battery packs to monitor the pack during charging? 

 

Looking at some of your pictures  I can see there is a voltage monitor connection against each string of interconnected cells but I fail to see how this would protect against one of the cells breaking down and demanding more current resulting in the other parallel connected cells receiving an over charge and hence possibly getting hot or catching fire.

 

No, I didn't use a BMS. This is my prototype and I wanted to keep it simple.

 

To mitigate against the risk of overcharging a cell, I'm charging to 0.05v per cell below the maximum allowed voltage. There are 8 cells in the parallel chains, so if one decides to go rogue and stops charging to 4.15v then there's headroom in the system to allow the 7 other cells in that parallel chain to take up the slack on the duffer's behalf. With the seven at 4.2v, the duffer can be as low as 3.80v and the charger will still see 4.15v coming back at it and terminate the charge. Because I charge it so slowly, I should pick up on those cells beginning to take longer to charge way before anything begins to start getting warm. (However, as an aside, this may be a fine reason against making the parallel chains too short, as the shorter the chain the more each cell will have to contribute to make up any shortfall - so longer chains are better? Discuss!)

 

I also used high quality, new cells. Not the best, but HQ. They were all at an identical voltage when soldered into parallel, so I haven't soldered in any imbalances. The whole system is pretty much at tickover, so nothing is being stressed. None of which flawlessly picks out a dying cell, I agree - I'm mitigating not eliminating - but I don't know of many BMS that will isolate a single dying cell either - think of the wiring harness! - so I'd probably just fuse each cell first anyway.

 

None of the above is to disagree with the fundamental of your comment, which is: Use a BMS, folks!  To which I'd add: "...and if you don't then build in a sensible amount of headroom instead - and understand what can still go wrong".

 

It's why this thread is a "Here's what I'm doing..." rather than a "Step by step guide to..."

[Philip Lewis 3]

No sorry I disagree, do not use a BMS, that is because if you have a balance lead and are therefore presumably balance charging with your charger, in that case the BMS is in your charger because it is doing the balancing, if you try and put a BMS in there then it and the charger could fight it out but more likely the one with the lower voltage cut off will just cut in first, you can't really use a BMS and use a balance lead and and balance charge, no BMS will pick up a dead cell but it will terminate the charge at 4.15 volts, it will only see the highest voltage it won't average it out over the cells and therefore will not overcharge the other good cells.