Lipo batteries Question

[MJW]

Ok, so I'm new here and to drones,

My drone came with a lipo battery, it is shipped in a plastic bag, sits on the shelf until it's purchased.

All safety precautions taken when charging, lipo safety bag and all,

So here's my question, once fully charged how much of a risk is there with these batteries just storing them?

Are they dangerous just sitting there?
Like can they randomly explode?

 

[MJW]

I did a short search after making this topic post, I guess I answered my own question.

 

[holtneil]

Never leave a lipo fully charged always store charge of you not flying for a few days

 

[Dugdog47]

I don't think they're dangerous storing them fully charged but that will shorten lifespan of the battery.

 

[MJW]

Morning, I thought about this and back when we were racing RC, we charged lot's and lot's of batteries, conditioned them in discharge boards, and yes they get hot when a full load is taken on them, also when charging at max rate, in those years I only maybe remember one pack went south and I tried and tried to condition it back, but in all that it never popped.
I always stored them just above full discharge, and stored them in a plastic box

The only guys having issues with their batteries were exceeding safety precautions, charging beyond the recommendation amp of the cells.

I can understand the precaution of the Lipo bag as that I'm sure if there are people in a hurry they will exceed precaution and charge rates, that will damage batteries, but if there's such a danger with Lipo's why doesn't the manufacture of my drone kit also supply a charge bag for the supplied batter?

In the video that I saw linked on another thread that doesn't appear to be a hobby shop, but an office of type's, there's something that's not being told there.
And the purple transmitter damage, yeah seen that too, either wrong battery or overcharge, not uncommon with the number of people doing things wrong.
In all the times I charged my TX it never burned.

I will take due cautions and check with the local hobby RC shop to see if this is more hype than is due.
I have bags on the way, and when I get the new batteries I'll check with their customer support about my questions.

 

[MJW]

Weird, the last post I made about batteries is awaiting approval, anyway I did a youtube search on lipo's and explosions, seems that 99% of them are deliberate damage to the cells.

 

[RENOV8R]

Weird, the last post I made about batteries is awaiting approval, anyway I did a youtube search on lipo's and explosions, seems that 99% of them are deliberate damage to the cells.

Also by over-discharging, you should never let your lipos get below 3.5v/cell

 

[wafflejock]

Being extra cautious about fire is never a bad thing unless you like the idea of you and those around you dying in a fire. You should take short circuit current and other potential sources of ignition around fuel seriously, there are no if ands or buts about it. Boeing is currently under fire by the FAA because of a fuel indicator in the tank that has electrical connections and could be a source of ignition, Boeing says the chances are low and so they will not fix the issue.... Who do you think is right in this scenario? In my opinion there is no such thing as being overly cautious when it comes to fire prevention and mitigation. No reason to see lithium as the devil or anything but treat it with respect it wants to react when it is charged.

 

[MJW]

Hi and good afternoon, well after a couple of days and a few fights and a battery tester that works for each cell I have good news, batteries don't go below 3.7 volts any cell at the end of the flight, drone won't power back up after it's landed on the fail-safe low battery mode functions.
I picked up a Horizon Prophet Sport Mini, it has a 1 amp and 2 amp selection for charging, the guy at the hobby shop said any of my batteries should be fine at 2 amps.
He seems to know what he's talking about, admitted a few battery burnouts but his batteries are exposed, he races or has raced in the past and they were damaged packs from high speed crashes,

Is he correct in saying 1800 lipos can be charged at 2 amps?

I've got two more batteries coming due to a defective plug in one of the batteries I just got, so good job to Blomiky for customer support.

The charger is only an AC source type so home charging only, dang,,,,, doesn't seem to be any DC source in my price range.
The bags showed up today, have two,

So far I'm having fun so all's good,,,,,,,,,

 

[wafflejock]

Yah 1800mAh can be restated as 1.8 Ah and the C rating for charge and discharge is related to this number so a 1C charge is 1 times 1.8Ah or 1.8A max charge rate going a few percent above this isn't going to be a big deal you wouldn't want to charge at anything more than like 2C or 3.6A for those cells to stay in the safe for the cells region faster you charge the more heat builds in the cells from their internal resistance and the lithium ions and electrons flowing around in there... If I'm in a big rush I'll charge at 2C and means your batteries will be full in 30 min at 1C they should be done in 1 hr (if empty). At 3.75V you still have some juice in the tank which is good and charge time even at 1C should be less than an hour, once you are comfortable with how differences in voltage causes current to flow can pick up a parallel charge board with fuses in it and if batteries are close in voltage when discharged can hook them to each other and charge together but need to be cautious since when hooking batteries or cells in parallel the voltage dumps from the one with more charge to the one with less rapidly (only stopped by internal resistance in the cell).

 

[MJW]

Thanks, kinda figured the hobby shop wouldn't steer me wrong.

EDIT:
I didn't intend on that reply to sound as if you guys might, ok?

 

[gregb49]

It's also worth reading the Batteries and Charging Thread

 

[MJW]

Morning Greg, yes I've read and made a few replies on that thread,

Seems I'm turning towards the dark side if you will, as you can see from the general theme of my replies, I was all about using just the stock charger and be satisfied with that,,,,,,,

My batteries didn't get even warm during charging, now I've gone from 3 hour, to two hour, to just around one hour charge times as long as I'm not doing damage to the pack or risking a fire.

The manufacturer is well aware of the risk and damage that can happen so they make sure that their charger's are not at fault should something happen but they don't supply any type of damage prevention such as a charge bag.

I've gotten Lipo charge bags and a Horizon 2 amp charger, going to take it to work and charge a battery, I can monitor it there, I have an infrared temp tool there so I can accurately take readings during the charge time and a safe area to do it in that if something were to happen the only thing damaged would be the battery.

Would a good rule of thumb for max charge temp be no more than the temp of the pack after a hard flight?

 

[wafflejock]

Nice write up on battery performance in low and high temps and during charging according to this blog from tattu above 45C is too hot some other places advise below 140F is still safe. Higher current increases losses as heat in any resistor as a square of the current so if you double the current you quadruple the energy dissipated as heat so make sure charge wires and everything can handle whatever current you use and/or just monitor things more closely if pushing it at all and just keep things in lipo safe bag or on fireproof surface with nothing flammable around it and don't need to worry as much.

How lipo battery's performance affected by temperature?

The Li-po battery is common and a variety of factors will affect the performance of the lipo battery. So what factors affect the performance and why?

www.genstattu.com

 

[MJW]

Morning, well I did as I said I would yesterday at work, all went fine.
The battery only increased in temperature by 15° and ended in a still slightly higher matched voltage, and then when I got home I checked and none of the voltage had dropped away,

Charge time was just over 45min.

Flight conditions here are still not conducive for a full flight to see if they have a slightly longer flight time, it should be a bit longer.

Average flight time per pack on Sunday was 13min.

And all of the local parks have rules against model aircraft flying, don't blame them but I've been told that I might get away with it as long as I don't get careless.

 

[MJW]

Good Morning all, snow in the next few days, so it's time for some more research on Lipo batteries.

As stated above, I got a new charger, 2 amps into an 1800 mAh pack, I did that on Monday morning, tried each day for some flight time to discharge the pack and last night finally clear & calm so I grabbed the drone and that charged pack, checked it before flight, 3.8v per cell, when I charged it it was clear up to 4.2 & 4.3v on Monday.
Three days after charging it I plugged it in and got about 5 min of flight time before the "Low Battery" lights started to go,
Set it down and checked the pack, 3.7 per cell,,,,,,,

Not surprised at the short flight time due to the charge in the battery just before flight of 3.8v but compared to what I got the first time I charged and stored the packs for a couple of days, 4.1v average per cell.

When I first got the drone and then charged the battery with the stock charger, 5hr. charge time, 4.2v per cell, it flew the drone for almost 14min.
I also got the two Blomiky 1800 mAh batteries and their supplied charger that took about 2.5hrs to charge a pack to 4.2v and both of those packs flew the drone for 13 to 14min.

My question is this, with the 3 packs charged at the lower amp's and extended charge times held their charge for almost three days before flying.
The pack first mentioned took less than an hour to charge and didn't hold a that good charge for two days,

Is this to be expected of faster charging?
Shorter charge held time?

 

[RENOV8R]

I can't really tell what you're asking, your post is a little confusing. But if you're asking why you get a short flight time when starting at 3.8 volts, well that's basically storage voltage. A fully charged battery is 4.2 volts, not 3.8

 

[MJW]

Sorry for the long delay in reply time, can't access the site at work, anyway I guess the bottom line of what I' asking is,

Can I expect a battery that has been "fast" charged as to speak, going to shed the charge in storage faster than a battery that has been "Slow" charged.?

 

[wafflejock]

No so long as the cells aren't damaged from having too high IR and being charged too quickly they shouldn't really show much difference in capacity from fast charging vs slow charging in terms of one cycle. They will drain much more quickly if accelerating around or speeding up and slowing down a lot or changing altitude more quickly (if more "load" from the motors and props because of higher throttle and or more changing direction) will all equate to motors drawing more amps from the battery over time and therefore draining it quicker. Voltage out of the lipo cells is roughly fixed in the range between 3.6 and 4.2V usually hovering around 3.8V for most of the discharge but the faster the motors are changing speed the more amps are drawn and therefore more Watts used, watts x time in hours = Wh.

Say you have a 4S 1800mAh battery.

3.7 V × 1.8 Ah × 4 cells = 26.64Wh

So if you draw 25W per motor it's 100W total then you can draw that 100W for 26.64/100 = .2664 hrs or .2664 x 60 = 15min if you double the draw from motors cause higher pitch prop or just flying more hovering less then you can draw more watts.

 

[wafflejock]

Look up "lipo discharge chart" on Google image search to see some comparisons of different discharge rates can see less area under the graph before being empty because of higher current discharge means you lose some capacity from just extra heat when drawing more power.