Charging rates and times

[Made2Fade]

Sheryl it dont matter what the voltage is... Its more to do with heat being developed during the charge cycle and IR. Every time they are charged then theres a 'cool down' period afterwards. This counts as one charge cycle. By simply topping the cells up its almost like doing another cycle also. At least thats how the cells see it anyways. Ive experimented with different charging methods over the last few year and it definately has a major effect on the packs.
In fact i think if you check the documentation that comes with the better lipo packs youll probably find it tells you not to top them up. Obviously Turnigy packs and such dont come with such documentation but the higher end packs usually do.

[helijohn]

Sheryl it dont matter what the voltage is... Its more to do with heat being developed during the charge cycle and IR. Every time they are charged then theres a 'cool down' period afterwards. This counts as one charge cycle. By simply topping the cells up its almost like doing another cycle also. At least thats how the cells see it anyways. Ive experimented with different charging methods over the last few year and it definately has a major effect on the packs.
In fact i think if you check the documentation that comes with the better lipo packs youll probably find it tells you not to top them up. Obviously Turnigy packs and such dont come with such documentation but the higher end packs usually do.

There goes my topping up routine.

[Made2Fade]

Ive known many people to leave packs fully charged... Its a fact that lipos loose around 1% of their capacity per month. So a few months go by and a few % has been lost. They then go 'top up' the pack and go fly. Big no no IMO... Best thing to do is just go fly the packs and not worry about the few percent thats been lost.
So you miss a few seconds flight time No big deal is it really in order to look after you expensive lipo packs you just invested in. Effectively in that scenario you are potentially damaging the packs twice.

[Made2Fade]

Check this out, Paul knows his stuff too - Guarantee « ElectriFlyer
Those guys sell Hayins and Gensace packs which both are also my go to batteries at the moment.

[helimadness]

All good info.
So I typically run my lipos down to say 25% average. Almost never go below 20%. So should I not be putting them back in storage charge after flying if they are going to get left for a couple of weeks? Am I better to just leave them flat and charge one time before I use them next ?

Cheers

[Grumpy]

Providing they have between about 3.7 and 3.9v in after flying then I'd just store them as they are. If they come off around 3.7-3.75v the only real advantage of storage charging from up to 3.85v is that it reduced the final charge time slightly.

PS... In answer to your original question on charging... why not just get a more powerful power supply? You can make one from a couple of DPS-600PB server supplies £30, so no point in limping along with an inadequate supply.

[Grumpy]

Ive known many people to leave packs fully charged... Its a fact that lipos loose around 1% of their capacity per month. So a few months go by and a few % has been lost. They then go 'top up' the pack and go fly. Big no no IMO... Best thing to do is just go fly the packs and not worry about the few percent thats been lost.
So you miss a few seconds flight time No big deal is it really in order to look after you expensive lipo packs you just invested in. Effectively in that scenario you are potentially damaging the packs twice.

It's not really the topping up before flying that does the damage, it's the storing fully charged. The 1-2% per month that they loose when stored fully is a permanent loss of capacity due to damage of the battery, you cant put that lost capacity back by topping up. If you store (say) a 5000mAh battery for a year fully charged you might end up with only a true 4000mAh capacity battery at the end of the storage period. Not only does the capacity deplete but internal resistance increases, effectively the c rating drops, so voltage will sag under load too which is usually what kills the battery for our purposes.

[helijohn]

It's not really the topping up before flying that does the damage, it's the storing fully charged.

So now I am getting proper muddled.

I go once a week, very rarely twice, and I bring the 5 amp batteries back at 1.5 amps or a tad under. Sometimes I don't go for a fortnight and in winter it could be weeks - like at Xmas. Soooo, what on earth do I do? Leave them at 1.5 amps, do a storage charge or what? And in the mornings I have to go out for 15 minutes slap bang in final moments of charging if I do an am charge. I charge the night before and do a top up in the morning most times. I will use the batteries no matter what as long as I see 4.1v per cell on the charger - what should I do for the best?
Interestingly I asked a question a few weeks back if it was better to have five batteries and use them to 25% remaining or have four batteries and use then to 20% remaining. The usage time gives about the same.

[helimadness]

Providing they have between about 3.7 and 3.9v in after flying then I'd just store them as they are. If they come off around 3.7-3.75v the only real advantage of storage charging from up to 3.85v is that it reduced the final charge time slightly.

PS... In answer to your original question on charging... why not just get a more powerful power supply? You can make one from a couple of DPS-600PB server supplies £30, so no point in limping along with an inadequate supply.

Yep have ordered a new PSU. 55 quid for a 1500w one. 0-30v adjustable. Should do it. The question has been answered fairly well. Looks like better to charge the night before at a slower rate. before I would only charge my 5000 mah lipos 2 in series at 1c so took a while to get through a few. Just being able to do them at 2c which still sounds reasonable would be a big help.

[Made2Fade]

It's not really the topping up before flying that does the damage, it's the storing fully charged. The 1-2% per month that they loose when stored fully is a permanent loss of capacity due to damage of the battery, you cant put that lost capacity back by topping up. If you store (say) a 5000mAh battery for a year fully charged you might end up with only a true 4000mAh capacity battery at the end of the storage period. Not only does the capacity deplete but internal resistance increases, effectively the c rating drops, so voltage will sag under load too which is usually what kills the battery for our purposes.

I agree that being left stored at full charge does the majority of damage but top ups reduce cycle life... thats as bad as damaging them in my book

[Made2Fade]

Yep John id just go fly them and make sure you are coming down with 25% + left in the packs. When you get home just leave the packs as is and do a full charge the night before you are about to fly again. Id charge at 1C typically but every now and then dont be bothered about giving them a 2C charge to help speed things up. It wont damage them doing a 2C charge.

[helijohn]

Yep John id just go fly them and make sure you are coming down with 25% + left in the packs. When you get home just leave the packs as is and do a full charge the night before you are about to fly again.

Thanks.

Might sound like a daft question but what are the ways to check in general terms what's left in the battery. I actually use an icharger 106B+. I ask because I have one 4 amp battery and when I gave it a storage charge it was down to 20%

[Grumpy]

Just get one of those cheap little LiPo voltage checkers that plugs into the balance plug of the LiPo. Most people fly to around 3.7-3.75v per cell, measured with the battery 'resting' after flying. That voltage equals roughly 20-25% capacity remaining.


PS.. for what it's worth i almost always charge immediately before flying. I use a couple of parallel charge boards so i can charge up to twelve packs at a time. Personally if i was regularly charging the night before flying I'd probably pop the batteries in the fridge overnight in a sealed 'tupperware' type container. Chilling them is almost a good as having them as storage charge as far as battery health is concerned. Possibly i'm going a bit over the top, but it only takes a moment to stick them in the fridge, so it's no hardship. Just take them out in the morning and allow an hour or two for them to warm up before using.

[Made2Fade]

PS.. for what it's worth i almost always charge immediately before flying. I use a couple of parallel charge boards so i can charge up to twelve packs at a time. Personally if i was regularly charging the night before flying I'd probably pop the batteries in the fridge overnight in a sealed 'tupperware' type container. Chilling them is almost a good as having them as storage charge as far as battery health is concerned. Possibly i'm going a bit over the top,

That may sound far fetched guys but Grumpy is 100% right with those comments. If you were going to store the packs for a long time its recommended
Its not something id like to do personally for fear of moisture getting into the packs etc. But as long as they were left in the air tight container until fully at room temperature then there shouldnt be a problem.

[Made2Fade]

Check out this chart it shows capacity loss vs storage conditions...
http://uterc.org/files/LipoStorageTips.pdf