Fly Boy 3 Posted January 16 Share Posted January 16 I have a lot to learn. I have read storage volts per cell are 3.8. Yet nominal volts/cell is 3.7v. What have I got wrong ? Cheers Quote Link to comment Share on other sites More sharing options...
Dickw Posted January 16 Share Posted January 16 Nothing wrong - both are correct. Storage and nominal volts are two different things. Dick Quote Link to comment Share on other sites More sharing options...
Rich Griff Posted January 16 Share Posted January 16 I am sure flyboy3 us gunna ask, what is the difference please. Obviousely 0.1 volts, but ..... Quote Link to comment Share on other sites More sharing options...
Phil Green Posted January 16 Share Posted January 16 'Nominal' is pretty meaningless in practise. Its often used as an 'average' voltage which it isnt really, especially not in our typical usage. Its also often used as a 'leveller' to compare batteries, which again, it isnt really. Dont worry about 'nominal voltage' just pay attention to charge, discharge & storage voltages 🙂 1 Quote Link to comment Share on other sites More sharing options...
Rich Griff Posted January 16 Share Posted January 16 I have looked but is there a thread especially for beginners about batteries ( especially lipo batteries ) on here to explain the somewhat confusing for beginners terminology... Eg, 1s 5c 2000mah ( I am sure a battery like this does not exist ? ). Beginners battery ( lipo etc. ) Thread ? Quote Link to comment Share on other sites More sharing options...
MattyB Posted January 16 Share Posted January 16 Better than that, there's a whole forum... https://forums.modelflying.co.uk/index.php?/forum/57-electric-flight-for-beginners/ Specific battery thread: 1 Quote Link to comment Share on other sites More sharing options...
Rich Griff Posted January 16 Share Posted January 16 (edited) There you go flyboy... George over on 4 Max has a good info sheet as well as good info on bmfa site... Maybe a "sticky" at the top of the battery section on here would be a good idea.........? Edited January 16 by Rich Griff Quote Link to comment Share on other sites More sharing options...
Phil Green Posted January 16 Share Posted January 16 All the info you need is there Flyboy but there is one particular thing thats always worth repeating: Dont charge indoors! Quote Link to comment Share on other sites More sharing options...
Geoff S Posted January 16 Share Posted January 16 2 minutes ago, Phil Green said: All the info you need is there Flyboy but there is one particular thing thats always worth repeating: Dont charge indoors! I charge indoors. I do it right next to a closed but unlocked outside door, on fire bricks, and never leave the room without stopping the charge. During WW2 my father charged dozens of lead acid accumulators (for battery radio valve heaters) every night (though I agree the technology is different it, still involves a lot of energy but coupled to glass sulphuric acid and lead). During the winter, where else are you going to charge when it's both dark and with quite possibly sub-zero temperatures outside? I'd also need an outside mains supply to power my 12v source. Not really very practical. 3 Quote Link to comment Share on other sites More sharing options...
leccyflyer Posted January 16 Share Posted January 16 I also charge indoors, in a pair of firesafes on the bench in the workshop and do not leave the batteries charging unattended. I wouldn't be able to charge outdoors in the winter, without charging in very low temperatures and would also need to secure some form of external power supply, which are both impractical at home. I suppose I could charge at the field, from my leisure batteries, but it's far from ideal during the winter. 2 Quote Link to comment Share on other sites More sharing options...
GaryW Posted January 16 Share Posted January 16 (edited) I Also charge indoors,,, In the Kitchen actually . All Lipos are stored at Storage Charge in a fireproof metal box & the lipos are charged on a section of fire/welding blanket which I'm always sitting next to doing other things while Lipos are charging,, As I charge my Lipos the night before each Flying Session they go back in the Lipo Storage Box over night till I leave for the Flying Field the following Morning, And ALL Lipos whether I use them all or not always go on the Charger & put back to Storage Charge before putting them away back in the Storage Box, I NEVER keep any Lipos at Full Charge other than as I mentioned above and I NEVER leave Lipos unattended while on charge Edited January 16 by GaryW Quote Link to comment Share on other sites More sharing options...
Phil Green Posted January 16 Share Posted January 16 (edited) Geoff, Brian, Gary - you are all experienced Lipo users. You know the score, you've assessed the risks. You're confident in your equipment and you're familiar with your LiPo packs. If theres trouble, you have a plan. Here we have a query from a new user, with as yet little or no experience. Are we recommending that he charges his new LiPos indoors? Edited January 16 by Phil Green Quote Link to comment Share on other sites More sharing options...
leccyflyer Posted January 16 Share Posted January 16 I don't know the OPs situation Phil, or his current charging regime. I think the most important things are to not leave charging lipos unattended, not charge them within reach of anything flammable, to use a proper balancing charger and not to charge at >1C, storing the lipos in some form of fireproof, or at least fire retardant receptacle. Given the practicalities, in our climate, I wouldn't state categorically to not charge indoors. I suspect most lipos are charged indoors - which includes in workshops, garages, sheds and other structures. 3 Quote Link to comment Share on other sites More sharing options...
Geoff S Posted January 16 Share Posted January 16 A few years ago, a clubmate set out deliberately to mistreat an old LiPo to see what happened. He set it up on our hard tarmac runway well clear of anyone or anything. IIRC he tried to charge it at a high constant current using either the NiCad or NMH functions on the charger. It took ages to start smouldering. In fact, we got bored watching and continued to fly on a clear part of the runway. It was disappointingly uneventful. However, there is clearly a risk, but it can be mitigated by a sensible approach. Incidentally, in addition to the precautions I outlined above, I also charge at or even below 1C - it's not a problem as I have the facility to charge 3 LiPos at once and my batteries are never fully discharged. Quote Link to comment Share on other sites More sharing options...
GaryW Posted January 16 Share Posted January 16 (edited) 1 hour ago, Phil Green said: Are we recommending that he charges his new LiPos indoors?..... Personally I'm not recommending anything Phil... and i admit my failing in not actually answering the OP's Question is "" I have read storage volts per cell are 3.8. Yet nominal volts/cell is 3.7v. What have I got wrong ? ""... So to answer The original Op's Question ...... An individual LiPo cell has a nominal voltage of 3.7V. When fully charged you will see nearly 4.3V on the cell but it will quickly drop to 3.7V under normal use. When depleted, the cell will be around 3V. This means your project will need to handle various voltages if you are running directly from a cell. As to where lipo users New & Experienced charge their Lipos is their own free choice to make, I myself like others some who have mentioned in above posts have chosen to charge indoors also I admittedly store my Glow & Diesel fuel indoors which both are in their original cans & tins which are all in the cupboard under my kitchen sink.... which yes we are well aware of the risks that poses where others choose to only charge and store lipos outdoors again that is their free choice to make .. The fact that i store and charge indoors and more based of my health and disability which wudnt normally allow me to work outdoors or say in a shed/workshop specially this time of year..... That and the fact my garden doesn't have sufficient available space for a shed/workshop although I do wish my Bungalow had a Garage that I can convert into a workshop Edited January 16 by GaryW Quote Link to comment Share on other sites More sharing options...
Martin Harris - Moderator Posted January 16 Share Posted January 16 Do you have any reservations about charging outside at low temperatures Phil? If they are fully charged and then brought indoors, isn't there a chance that they will go over voltage as they warm up by maybe 20 or more degrees? I don't know if this is actually a problem for either battery life or more importantly, safety but it could be worth considering terminating the charge before 4.2v/cell when charging outside. Quote Link to comment Share on other sites More sharing options...
Don Fry Posted January 16 Share Posted January 16 It’s a serious issue for longevity of the cell, as it warms from full volts to room temperature, the cell volts go up. Cells hate overcharge volts. This is not a new issue, there are threads all over the internet, discussing storage temperature, and charge temperatures. Me, charge/store/discharge in workshop, take precautions, see loads of threads, fire suppression strategies. Store in workshop. Lazy, perhaps. I might say eliminates senile mistakes, where the disaster, ie idiot set the charger wrong, has already covered that bet. Crystal memory is the term psychologists use. For younger readers, read daft for senile. Ignore crystal memory, you haven't got it yet. Quote Link to comment Share on other sites More sharing options...
Outrunner Posted January 16 Share Posted January 16 1 hour ago, GaryW said: An individual LiPo cell has a nominal voltage of 3.7V. When fully charged you will see nearly 4.3V on the cell but it will quickly drop to 3.7V under normal use. When depleted, the cell will be around 3V. This means your project will need to handle various voltages if you are running directly from a cell. If you discharge your lipo to 3v per cell they ain't going to last very long. If your batteries are quickly dropping to 3.7v under load then you have a problem. Quote Link to comment Share on other sites More sharing options...
Phil Green Posted January 16 Share Posted January 16 Sorry, a bad choice of words (& pics!) posted without proper consideration. What I intended to suggest is not to charge in your house but in an outbuilding, shed or workshop, but I had in mind flying & charging in summer, not the sub-zero temperatures we're enduring at the moment, and of course we shouldnt charge cold and then bring the charged lipo into warmer surroundings. It didnt occur to me that anyone would be flying and charging while its so bitterly cold... hardy souls! 😊 Apologies for the misleading post. I'll get back in my box now 😏 Cheers Phil 1 Quote Link to comment Share on other sites More sharing options...
GaryW Posted January 16 Share Posted January 16 (edited) 14 minutes ago, Outrunner said: If you discharge your lipo to 3v per cell they ain't going to last very long. If your batteries are quickly dropping to 3.7v under load then you have a problem. Nominal Cell Voltage - The average voltage a cell outputs when charged. The nominal voltage of a battery depends on the chemical reaction behind it. A lead-acid car battery will output 12V. A lithium coin cell battery will output 3V. The key word here is "nominal", the actual measured voltage on a battery will decrease as it discharges. A fully charged LiPo battery will produce about 4.23V, while when discharged its voltage may be closer to 2.7V. https://learn.sparkfun.com/tutorials/battery-technologies/all#:~:text=An individual LiPo cell has,running directly from a cell. Edited January 16 by GaryW Quote Link to comment Share on other sites More sharing options...
leccyflyer Posted January 16 Share Posted January 16 You really, really, really do not want to be discharging your lipos down to 3v/cell and certainly not to 2.7v/cell. Quote Link to comment Share on other sites More sharing options...
GaryW Posted January 16 Share Posted January 16 13 minutes ago, leccyflyer said: You really, really, really do not want to be discharging your lipos down to 3v/cell and certainly not to 2.7v/cell. Personally I can't say I've ever tried to myself I'm more than happy with ,y lipos being at 25% around 3.7-3.8v per cell 11.3-11.4v on a 3S lipo after each flight Figures are just estimates of coarse Quote Link to comment Share on other sites More sharing options...
Dickw Posted January 16 Share Posted January 16 I have seen 3v or even a bit below on extreme loads (e.g. 100 C) but the cells soon bounce back to 3.7v plus when the load is removed. A cell at 3.7v off load is effectively fully discharged I.e. flat Dick 1 Quote Link to comment Share on other sites More sharing options...
leccyflyer Posted January 16 Share Posted January 16 Yep - a lipo cell at 3.3v under load will rebound to 3.7v off load and personally I don't want mine any lower than that, such that I aim to store them at 3.85v/cell. Quote Link to comment Share on other sites More sharing options...
leccyflyer Posted January 16 Share Posted January 16 48 minutes ago, Phil Green said: Sorry, a bad choice of words (& pics!) posted without proper consideration. What I intended to suggest is not to charge in your house but in an outbuilding, shed or workshop, but I had in mind flying & charging in summer, not the sub-zero temperatures we're enduring at the moment, and of course we shouldnt charge cold and then bring the charged lipo into warmer surroundings. It didnt occur to me that anyone would be flying and charging while its so bitterly cold... hardy souls! 😊 Apologies for the misleading post. I'll get back in my box now 😏 Cheers Phil No worries Phil - we fly year round up here in the frozen North, you know 😉 I built an insulated lipo bunker last year and my intention was to store my lipos entirely outdoors. However, monitoring the internal temperature over a few weeks it was obvious that it was dropping to below freezing during the night and I didn't fancy that. So, they still live in their lipo bags and sacks inside a vented steel cabinet in the workshop - mostly at storage voltage. Quote Link to comment Share on other sites More sharing options...
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