Mouse Posted January 13, 2014 Share Posted January 13, 2014 Hi there I am relatively new to flying and the use of lipo's and regularly see posts about storing them when not in use. However most of these posts seem to be about charging a discharged lipo up to a storage charge, what I want to know about is how to discharge a fully charged lipo down. At the moment I have 5 lipos all 3 cells and about 2200 mha and when I go out I charge them up before I go but sometimes I do not get to use them all or on occasions I do not get to go at all which leaves me with all fully charged battery's and I might not get to use them for several weeks. When I used to use ni-cads in buggies and boats I used to use a car headlight bulb to discharge them down to when they went dim but I am not to happy about using the same method for lipos. Any advice please. Mouse. Quote Link to comment Share on other sites More sharing options...
Olly P Posted January 13, 2014 Share Posted January 13, 2014 Hi Mouse, There are 2 possible approaches - if you are not going to store them for long, then don't worry too much - I have stored fully charged Li-Pos for extended period when my flying has been limited unexpectedly Otherwise, most chargers with a storage setting will actually discharge rather than charge if you select this program and have a fully charged lipo plugged in. Olly Quote Link to comment Share on other sites More sharing options...
The Wright Stuff Posted January 13, 2014 Share Posted January 13, 2014 Good question, and one I asked myself not long ago! My charger does not have a discharge setting! My solution was a 50W, 12 V lightbulb - the kind you get in bathroom ceilings. The GU5.3 fitting will conveniently plug straight into an EC3 connector on the battery, if that's what you use. Trial and error told me that it takes about 9 to 10 minutes to discharge to storage voltage from fully charged. Since this is about the same time it takes to discharge the battery when flying, I think it's a safe discharge rate for a 3S lipo. As you said in the OP, you don't want to leave it until the bulb goes dim, but time it, so you only discharge to a safe level. Obviously, do this with the same precautions you would use to charge the battery, and don't touch the bulb, or place it on anything flammable or meltable, it WILL get VERY HOT! I just use the garage floor! And it goes without saying: don't leave unattended!!! Ian Edited By The Wright Stuff on 13/01/2014 12:14:19 Quote Link to comment Share on other sites More sharing options...
Mouse Posted January 13, 2014 Author Share Posted January 13, 2014 Hi and thanks for the reply's Olly, you say that you have kept your lipos for an extended period of time but could you say what that is as I am looking at a month or so, and also what state of charge should I keep them at if I do discharge them % wise. and if I go below that I assume that it is o.k to recharge up to a "storage voltage". Mouse. Quote Link to comment Share on other sites More sharing options...
The Wright Stuff Posted January 13, 2014 Share Posted January 13, 2014 In terms of storage voltage, generally between 40% and 60% capacity (11.25 to 11.55 volts for a 3 cell) is the advice. One assumes that this means for longer storage, they should be 40%. For less long storage, 60% is sufficient. What an 'extended period of time' means is a good question. I don't really fly much in the winter at all, so for me, it's 4 or 5 months. I would say that fully charged stored up to a month would be probably fine - SO LONG AS the temperature is fairly constant. Capacity reduces with temperature, so if they get cold in the winter, they can be potentially damaged as they become overcharged. To be honest, though, I don't think any of this is rocket science -just general guidance. I've yet to meet anyone who has had failed Lipos that can be categorically attributed to incorrect storage voltages! 'Yes' to your second question! Quote Link to comment Share on other sites More sharing options...
Mouse Posted January 16, 2014 Author Share Posted January 16, 2014 Thank you for the reply's. I have decided to go down the bulb discharge route and go with what Ian has suggested but I will get a bulb with a holder and put a xt 60 on the end and possible fit a switch so that it will be easier to connect/disconnect. Mouse. Quote Link to comment Share on other sites More sharing options...
Delta Foxtrot Posted January 16, 2014 Share Posted January 16, 2014 Or. You can just solder a 12v car tail light bulb onto one end of your pair of wires and the male battery connector onto the other. This is what I use to discharge lipos that I want to decommission before taking them to a battery bank. Edited By david fillingham 1 on 16/01/2014 20:58:01 Quote Link to comment Share on other sites More sharing options...
John Privett Posted January 16, 2014 Share Posted January 16, 2014 Posted by Mouse on 16/01/2014 15:44:26: I have decided to go down the bulb discharge route and go with what Ian has suggested but I will get a bulb with a holder and put a xt 60 on the end and possible fit a switch so that it will be easier to connect/disconnect. Mouse. Well if you're going to do that you'll need to keep a very close eye on the voltage as each battery discharges. Otherwise you risk doing more harm to the battery by over-discharging it than if you'd simply put it away in a normally-charged state! Quote Link to comment Share on other sites More sharing options...
PatMc Posted January 16, 2014 Share Posted January 16, 2014 Why not just connect each lipo in turn to a model or bench mounted motor & run them for a few minutes at part throttle with a wattmeter monitoring the voltage. Personally I don't bother discharging them at all, I just store them fully charged. Quote Link to comment Share on other sites More sharing options...
John Privett Posted January 16, 2014 Share Posted January 16, 2014 Posted by PatMc on 16/01/2014 22:08:40: Personally I don't bother discharging them at all, I just store them fully charged. I was going to say much the same Pat! Trouble is, I can't honestly say whether the batteries might last a bit longer if I did discharge them. Seems like a lot of extra hassle though for a probably very limited return! Quote Link to comment Share on other sites More sharing options...
Kevin Wilson Posted January 16, 2014 Share Posted January 16, 2014 I am with Olly on this one. Even my cheap clone 4 button charger automatically charges or discharges to get the battery to 3.8v per cell. Not an obvious stated function but thats what it does. I have always heard that 3.8 to 3.9 is the optimum storage value. But temperature is as (if not more) important than voltage. 5degC in a fridge was suggested in the podcast www.allthingsthatfly.com episode 276 I discharge unused packs if I am not going to use them within a month. Quote Link to comment Share on other sites More sharing options...
Olly P Posted January 17, 2014 Share Posted January 17, 2014 Extended period in this context is about 13 months so far! Quote Link to comment Share on other sites More sharing options...
Mouse Posted January 22, 2014 Author Share Posted January 22, 2014 There seems to be a lot of divided opinion on this. I am now debating keeping them at about 80% so that if i get a sudden chance to go flying it will not take to long to top up my battery's and i think (hope) that they will be o.k for a few months in this state. Mouse. Quote Link to comment Share on other sites More sharing options...
John Olsen 1 Posted January 22, 2014 Share Posted January 22, 2014 Some chargers will discharge the batteries down to the storage level, eg depending on the state of charge, the same setting on the charger will either charge the cells up or discharge them. They can do this because the balancing feature on the charger has the ability to discharge cells. The advantage of using the charger is that you don't have to remember to stop it at the right time since it will stop itself. Having said all that , I have to admit I don't worry about storage charges myself, but then I live in a climate where it doesn't usually get very cold. John Quote Link to comment Share on other sites More sharing options...
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