fast charge vs lipo chargd

[Chris gregg]

hello i have the imax b6 charger unit and charging my batteries at lipo charge and every month will do a balance charge....my question is i have a 11.1v 3200mah lipo what setting can i do in a fast charge setting? if im at field and want a fast charge what is safe?

[MattyB]

It should tell you the max charge rate in C for your pack on the outside - most batteries now have a rating between 2 and 5C. Opinions vary greatly on this topic, but I generally never charge above 2C in order to preserve the cycle life of my packs; in your case 2C = 2x3200 = 6.4A. I would also recommend that when charging at home you balance charge every time, as this should of lengthen the life of your batteries and many of today's chargers rely on being able to see the cell voltages in order to utilise their more advanced safety features I.e stopping the charge if an issue is detected.

Edited By MattyB on 07/11/2016 09:23:33

[Chris gregg]

would it damage the pack charging it at 5.0amp all the time??

[Cuban8]

Second everything that MattyB has said - good advice. As for your 3200 3S being charged at 5A, I'd say you'd be perfectly OK but why not try starting at 4.5A and increment subsequent charges to 5A? Check the pack to see if it shows signs of getting warm (I charge my 3000 packs at 4.2A and they remain at ambient temp throughout the charge) if the battery is warming, then stop PDQ.

[Peter Jenkins]

Chris, you won't damage your pack if you charge at 5.0 amp all the time - as this is below 2C as MattyB has pointed out above. Assuming that your pack is rated at 2C and above.

Having read the post title, I had thought you were asking about fast charging and full charging. Generally, a fast charge will take you to about 95% of capacity in under an hour whereas a full charge can take longer depending on how much balancing the charger needs to do to make sure that all the cells are at the same voltage of 4.2 v. As you get close to 4.2 v for each cell then there is much more inter-cell balancing that the charger needs to undertake and that's reflected in the difference in charging time for fast and full charges. Generally speaking, 95% capacity is perfectly adequate provided you are not aiming to get the maximum safe charge out of the pack. You are probably aware that you should aim to discharge no lower than 20% of capacity to prolong battery life.

[Biggles' Elder Brother - Moderator]

I am a bit fussy with charging. Some personal "rules" I follow:

1. Always balance charge unless there is a good reason not to - for example at the field and you want fast charge. But balance that battery on its next charge.

2. Never charge at a rate above 2C

3. If poss - ie if I rememeber and have time - cycle batteries once a month - discharge to balanced cahrge - to check capacity and record it. Look for trends.

OK sounds a bit of a palava - but I have a lot of "old batteries" (well old by many people's standards) who have done a an awful lot iof cycles and are still going strong. So I get my reward that way!

BEB

[Peter Jenkins]

BEB, the other thing I also keep tabs on is the internal resistance. You can get a good indication of that by the heat of the pack after discharge. Some are hotter than others - assuming similar use of course - and that is a function of increasing IR and therefore heat being generated in the pack. Around 23 mili ohms for a 5S pack seems to be where things start to go downhill.

[Chris gregg]

well i have bought myself a safeguard checker, just charged my batteries at 4.0 and it was faat enough for me on normal charge mode, got to field, i got 10 mins out of each battery and checked my battery it was 35%

[Former Member]

[This posting has been removed]

[Bob Burton]

Posted by Percy Verance on 07/11/2016 13:59:58:

I balance charge every charge.........

Me too. It takes a little longer but is well worth it for the peace of mind it gives.

[Geoff S]

Me too, Percy. I also only charge at the 1C rate. I also keep an eye on the internal resistance though not in a formal way (ie I don't write it down or record it) but I know once the cell resistance get up to 10 milli-ohms it's getting very much past its best.

Geoff

[Former Member]

[This posting has been removed]

[Chris gregg]

so if i charge well under 4.0 my lipo will last longer than one that charges at 3.2?

[Simon Chaddock]

Chris

Its actually heat that damages LiPo. The heat generated is a function of its internal resistance whether charging or discharging.

We tend to accept that a LiPo will get warm on discharge simply because we need the high currents to fly but the heat generated from charging is under our control.

For most LiPo a 1 C charge will not raise the temperature of the pack more than a few degrees so this is 'norm' for maximum battery life.

A high C battery has a lower internal resistance so can be charged at a higher rate (up to 5C) without generating any more heat than a lower C rated battery.

The problem is the very heat generated by a LiPo will over time raise its internal resistance which means it generates more heat when in use which then raises the internal resistance still further.

Unless you can afford to treat a LiPo as a short life 'consumable item' it pays to look after them!

Edited By Simon Chaddock on 07/11/2016 22:06:32

[Chris gregg]

right so i should balance charge at 3.2 from now on this will prolong the life thanks

[Former Member]

[This posting has been removed]

[Simon Chaddock]

Chris

As Percy says a 1C charge will be 'kinder' to your battery than a fast charge but be aware that the practical life of LiPos seems to be almost randomly variable. Even when identical batteries are treated in the same way some will last longer than others.

Many peps have their 'favourite' brands but a trawl through the forums show there there is little commonality.

All you can do is treat your battery as kindly as you can.

[Biggles' Elder Brother - Moderator]

To be honest - having done both - I do not think there is any major difference between 1C and 2C. I totally agree that charge rates significantly above 2C are questionable in terms of battery life. As stated above I regularly charge at 2C and my batteries certainly outlast most people's around me. I put that down to two facts (both of which I personally think are more important in the overall effect on battery life); first is the fact that I never discharge below 20% capacity - usually more like 25-30%. Secondly I always balance charge - only very, very, rarely doing otherwise.

As I say I can get excellent battery longivity from these two and 2C charging.

BEB

[Nigel R]

Posted by Percy Verance on 08/11/2016 14:17:56:

I'm given to understand a normal (non balancing) fast charge will take the pack to about 90%, whereas a balance charge will get it fully topped up, assuming the pack is in good health.

Depends how long your balance charge takes, my understanding is that a full 100% charge will take a good 2 or 3 hours, regardless of the speed of the fast charge phase.

[Peter Jenkins]

Firstly, I never charge a LiPo without using the balance function - without that you run the risk of overcharging one or more cells and undercharging others. If you have a balance charger use it in balance mode and if you don't have a balance charger then it's in your own interests to get one!

I charge 2 x 5S 5000 packs in parallel and with a Fast Charge to 95% capacity at 1C they are done in less than an hour. If I go for a 100% charge it takes about 10 to 15 mins longer. If it's taking 2-3 hours to fully charge then you have a problem with the charger or battery or both.

[Dave Bran]

Has anybody mentioned that a lot of chargers won't actually achieve the higher charge rates anyway.....

[MattyB]

Posted by Biggles' Elder Brother - Moderator on 08/11/2016 16:25:53:

To be honest - having done both - I do not think there is any major difference between 1C and 2C. I totally agree that charge rates significantly above 2C are questionable in terms of battery life. As stated above I regularly charge at 2C and my batteries certainly outlast most people's around me. I put that down to two facts (both of which I personally think are more important in the overall effect on battery life); first is the fact that I never discharge below 20% capacity - usually more like 25-30%. Secondly I always balance charge - only very, very, rarely doing otherwise.

As I say I can get excellent battery longivity from these two and 2C charging.

Completely agree on all points - with first generation lipos there was undoubtedly value in charging at lower rates, but I have not seen any appreciable heat build up/degradation in performance from charging at 2C with more modern (i.e. from the last 4-5 years) packs. They are a lot more resilient than those early examples!

[MattyB]

Posted by SuperNash on 08/11/2016 17:09:42:

Posted by Percy Verance on 08/11/2016 14:17:56:

I'm given to understand a normal (non balancing) fast charge will take the pack to about 90%, whereas a balance charge will get it fully topped up, assuming the pack is in good health.

Depends how long your balance charge takes, my understanding is that a full 100% charge will take a good 2 or 3 hours, regardless of the speed of the fast charge phase.

I don't know what charger you are using, but that is absolutely not the case with those I have used. Both my iChargers will balance charge any pack within their capability range at 1C in under an hour and at 2C in ~30 mins to an indicated 0.01-0.02V/cell variance. I'd call that fully balanced!

[Former Member]

[This posting has been removed]

[MattyB]

So if you set it up to balance charge at 1C your packs will take 2-3 hrs before it tells you the charge is complete? Wow. What voltages is it saying the individual cells are coming off charge at, and what accuracy does it measure the voltages to?

My cheaper i106b iCharger only measures to a 1/100 of a volt whilst the 406 measures to 3 decimal places. The actual accuracy of balance doesn't seem much different though if a pack off the 106 is measured on the 406 immediately after charging. Both terminate a 1C balance charge after about 45 mins if charging from a storage voltage of 3.75V/cell, though the 406 actually has multiple balance charge cycles of various different speeds (it has a much higher max balance charging current which I guess helps here).