911hillclimber Posted April 19, 2021 Share Posted April 19, 2021 I have a 3S 2200 lipo in my vintage plane, all works well. However, once flown I have no idea what is left in the battery and so cannot be sure to use it again for a second flight. Is there a simple checker available that will state, for example, '30% of battery charge left'? Thanks, Graham. Quote Link to comment Share on other sites More sharing options...
john davidson 1 Posted April 19, 2021 Share Posted April 19, 2021 Yes , a combined watt meter and battery checker , readily available from all the usual retailers for little money. The watt meter is invaluable in setting up a new drive train Quote Link to comment Share on other sites More sharing options...
Shaun Walsh Posted April 19, 2021 Share Posted April 19, 2021 You need something like this https://servoshop.co.uk/index.php?pid=OL8SCHECKER&area=BATTERY Quote Link to comment Share on other sites More sharing options...
RottenRow Posted April 19, 2021 Share Posted April 19, 2021 It’s not a great idea to use a partially discharged battery for a second flight. Many speed controllers use the battery voltage at first connection as a reference for when to go into low voltage cut-off mode. If you start off with a low voltage then the ESC will miscalculate the cut-off and the battery could be damaged by over discharging it. Not all ESCs work in this way but many of the cheaper ones do. Having a battery checker will enable you to see how much of the battery capacity you are using in a typical flight, and you can increase your flight lengths accordingly if you like. Don’t discharge below 20% and your battery should last a long time. Brian. Quote Link to comment Share on other sites More sharing options...
911hillclimber Posted April 19, 2021 Author Share Posted April 19, 2021 Thank you all, it is very much knowing how much has been used more than anything. I think I'll get another battery from 4Max so to have a pair of batteries fully charged. seems the etiquette on the flying field is to be in the air for 5 minutes. The plane wafts along on almost zero motor rpm so current draw must be quite low over the 5 mins. Great help as ever, thank you. Quote Link to comment Share on other sites More sharing options...
kevin b Posted April 19, 2021 Share Posted April 19, 2021 These are good, cheap and in the U.K. I have one very similar. https://www.ebay.co.uk/itm/LiPo-Battery-Tester-Voltage-Checker-Capacity-Li-Ion-NiMh-NiCd-LiFe-SAMEDAY-POST/174723072189?hash=item28ae4e80bd:g:OJsAAOSwUL9gbatj 1 Quote Link to comment Share on other sites More sharing options...
911hillclimber Posted April 20, 2021 Author Share Posted April 20, 2021 Both the options above look good and will do what I need. thank you everyone. Graham Quote Link to comment Share on other sites More sharing options...
Capt Kremen Posted April 20, 2021 Share Posted April 20, 2021 (edited) Additionally to a good meter and use of a watt meter to calculate matters. Get a fellow flier to time several flights for say one or two minutes from motor start to final stop. Fly as you normally would with that model e.g. perform loops, rolls, touch 'n goes or just circuits etc. Do this for several flights, always with the same fully charged Lipo. After each flight measure the indicated capacity and always using the same meter for instrument consistency. (These are not scientific accuracy devices you're using!) Say your LiPo indicates 98% at start and after a normal two minute flight the pack indicates 68% (approx. as each flight will be slightly different), you can see your flight, with that model, in the style you normally fly, has used approx. 30%. By extrapolation, you would likely consume approx. 60% if you doubled your flight time and so on. These are very rough guides but give an indication of how long you can safely fly for with that model and LiPo AND flying in the same manner. Allowance has to be made for conditions, temperature etc. e.g. If you subsequently fly almost full-throttle on a flight, you will naturally use up the stored energy sooner and so on. If, after a while, you notice you are not measuring the expected capacity after your 'x' minutes of flight, it would be prudent to check that particular LiPo for signs of deterioration e.g. one cell always out of balance with others. Edited April 20, 2021 by Capt Kremen Spelling! Quote Link to comment Share on other sites More sharing options...
911hillclimber Posted April 20, 2021 Author Share Posted April 20, 2021 Thank you. This is what I need to do. I am a novice in all this world, and have flown the vintage Buccaneer (like a Junior 60) just once! I have little idea how long I was in the air, but guess 5 mins as the gent with me said it was time to land, others were waiting to fly. The lipo I have (new from 4-Max) took quite a time to change when home, so might have been at the end of it's capacity, but i want to know. Graham. Quote Link to comment Share on other sites More sharing options...
Dwain Dibley. Posted April 20, 2021 Share Posted April 20, 2021 Set a timer to count down on your transmitter, I always set 7 minutes on every thing except my easy pro glider, cos that's up there for ages using no power. When you are a new flyer you will find you will land before the buzzer goes off, as you progress you will be up longer. D.D. Quote Link to comment Share on other sites More sharing options...
Chris Walby Posted April 21, 2021 Share Posted April 21, 2021 Ask a few club members if they have a 5 minute rule or its just a understanding when they are busy 5 minutes is what's expected and TBH I find 5 minutes for a trainee or if I am really pushing it that's enough of a concentration burst. If you are charging at 1C e.g. 2.2A for say a 3S2200 it should take close to 60 minutes from 0 to 100% (not that you should ever drop it to 0%), so as a rule of thumb it takes 30 minutes then it was about 50% discharged. Handy to know if you don't have a voltage/capacity meter handy or if you are at the field and just flown, swap your lipos and check the one coming out. If its reading say 50% and you put it on charge you know that it should be fully charged in about 30 minutes (fly on the other lipo chat, cup of tea and prep for next flight) and then you are ready to go. For me 10 minutes is nice with a pleasant flying model....or one of my demanding edf's 3 min 20 sec and 15% left is more than enough ! Quote Link to comment Share on other sites More sharing options...
Cuban8 Posted April 21, 2021 Share Posted April 21, 2021 The battery checkers are handy to see that cells remain balanced or to check that you're not fitting a discharged battery by mistake. The capacity remaining/used function is, because of other factors and IMHO, only an extremely rough indication and is tempting fate if you rely on it to 'have another flight' or estimate charge times. Let your charger do the thinking! Quote Link to comment Share on other sites More sharing options...
Shaun Walsh Posted April 21, 2021 Share Posted April 21, 2021 If there is room in the fuselage, fit one of these to the balance lead of the battery. Battery voltage alarm Set the alarm to 3.75 V and it will go off when there is approx 25% left in the battery Lipo capacity vs voltage Quote Link to comment Share on other sites More sharing options...
911hillclimber Posted April 23, 2021 Author Share Posted April 23, 2021 (edited) I think the 5 mins is just about right, concentration when you are frightened like me of The Big Crash happening, and right for those waiting to go next. a fellow helper set a 5 mins warning on my Tx, didn't know you could do that... My little checker arrived today, £6.30 pff ebay, and all works my charging of the 2200 was left for 6 hours and indeed shows 100% charged. New battery on order from 4 Max, same spec as the current one. I think this will satisfy my amature appetite for now unless the sock is drooping at 6 o'clock! Edited April 23, 2021 by 911hillclimber Quote Link to comment Share on other sites More sharing options...
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