Hello all. I was reading through the link to the batteryuniversity which is very informative. One thing they seem to elude to was how many days can you leave a LIPO fully charged? For now I try to use them max within a week. My charger only brings each cell up to 4.15v.

No problem with 4.15 or even 4.12V/cell.
Lower maximum charge voltage actual results in longer cycle life.

Battery stress under maximum voltage (fully charged) is cumulative. The fewer days at full charge the better.
If you fly the packs don't recharge them if they are over 3.7V/cell till you are ready to fly again, or just bring them up to long storage voltage (3.85V)

If I don't plan on using them within 24hrs I discharge them to something under 4V/cell.

thx hoppy...

If I wanted to Run a 9S battery for the Habu 32(1409-2Y) motor TJ 80 Fan.. Could I hook up a 5s battery 18.5v in series with a 4S battery14.8V battery?? Its confusing to me?? Is my voltage output the sum of these two packs??

Packs in series add the voltages together. (mah does not change)
A 3s2000mah pack in series with a 4s2000mah pack = 7s2000mah pack.

Packs in parallel, add the capacity (mah) together.
A 3s2000mah pack parralled with a 3s2000mah pack = 3s4000mah pack.

This is very important.
Packs put in series must have the same mah capacity.
Packs put in parallel must have the same voltage and should have the same capacity.

Good stuff, I love it!
Tks,hoppy@@@

Originally Posted by hoppy

Most common charge current is 1C.

Take the mah capacity of the battery and divide by 1000. This gives you the
1C charge current in amps.

2100mah/1000 = 2.1A charge current (1C)
3200mah/1000 = 3.2A charge current (1C)

If the battery pack allows a 2C charge current multiply the 1C current by 2.
If 1C = 2.1A charge current, 2C would be 4.2A charge current.

Since im plain stupid and paranoid about lipos, im asking this to be 110% sure,
I got a 3s 3300mah pack with discharge on 25C and a charge at 5c, if im correct, i can then charge the pack at max 16,5 amp, right?
3300mah/1000=3.3amp (1c) then 5c should equal 16.5 amp, still right?

1C for a 3300mah pack would be 3.3A
5C would be 3.3 x 5 = 16.5A

You got it.

Problem for some would be finding a 16A charger. Nothing wrong with charging at a lower rate.

Thanks

i have a question about danger of storage. what is the possibility of a lipo blowing up during storage?

The possibility of it blowing up is non existent. LiPo batteries do not blow up.

If over charged, or shorted they can rupture and shoot flames. If punctured they can shoot flames.

If undamaged and stored at about 50% charge in a cool place the possibility of any of this happening is very low.

All that being said, try and store them away from any flammable materials. In the summer I store mine in a wood burning stove. I just received a flame proof LiPo storage bag but I still think that should be backed up with a metal box or a ceramic pot.

Most LiPo fires happen when people are charging and leave the charger unattended. Never leave LiPo batteries on charge unattended. Charge away from flammable materials.

okay thanks. so i shouldn't have any lipos going off on me while they are stored? im going to have them stored in the garage.

I'm a little curious as to why my laptop and phone can easily charge a lithium battery without any real issues... but after reading all of this, it appears like there is a high likelihood that using these batteries from RC suppliers results in the possibility of endangering my family. Does that not seem "backwards" to anyone else? I mean, if you are buying a $25 battery and a $50 charger, you'd expect it to just charge without incinerating your home.

So whats a practical way to charge these things while containing the damage if they DO explode? Should you loop the cord into something metal like a toolbox or something?

Though infrequent, they can catch fire, mostly during charging.

IMO, the safest way to charge is to be in the room with the packs and observe them. Lipo packs will swell quite a bit before igniting so there is a time frame of many minutes (5,10 +) where if the modeler notices the swelling, the charge can be stopped.

Equally safe would be to charge outside in a firesafe area.

Next would be indoors inside a metal box, BBQ grill, LipoSack or similar firesafe container.

The worse scenario is charging on a flammable surface near flammable items indoors and leaving the area. This has resulted in major fire damage to the house.

Other things to consider...
Don't keep damaged lipos. When they start to puff or are physically damaged, they should be discharged and tossed.
Even though a firesafe box can prevent fire damage the smoke can cause a lot of damage which is why the best method is to keep it from happening or do it outside.

Remember, the likelihood of this happening is very small, especially if you keep your packs in good condition....use only 80% of capacity...follow the manufacturers use directions, etc. But like me, you are concerned that it could happen as there are no guarantees with lipos, so take the precautions and enjoy. If possible, baby sit the packs while charging, safest way IMO....if you see anything unusual, stop the charge and check it out. I store, charge and transport my lipos in firesafe containers just in case.

Go up to post #2 and look at "Videos of LiPo Container Tests." It'll give you an idea of what other people have done and what happens during overcharging.

Again, remember that if you use packs in good condition and charge with a balancing charger witnin the C-rate specified by the manufacturer, the chances of an ignition are very low..........but just in case, watch them or box them.

I've got 8 yrs experience with them without an incident as have many many other modelers, but still I don't trust them enough to leave them out of the firesafe boxes, just in case.
Any other questions?

Originally Posted by AgentSmith27

...Should you loop the cord into something metal like a toolbox or something?

Not sure what that would do.

The most important thing you can do is never charge unattended.

Use a quality balance charger designed for LiPo batteries. Check out CellPro.

Charge away from flammable materials. Many use fire proof charging bags for charging and storage. LiPo Safe is one brand.

Arrange a safe storage location or vessel. A covered ceramic pot makes for worry free storage. There are many possibilities. Here is one. Battery Bunker