Data Complete Guide to Lithium Polymer Batteries and LiPo Failure Reports

[TIA]

Wonder if this will work with lipos that already have balancing plugs on them?

Are all balancing plugs wired the same?

[Mark Winstanley]

I am not sure I am qualified to answer you. The LiPos I have (Kokam) did not have balancing taps installed. The cannectors I bought at the same time are the ones that fit the Robbe Equalizer. They are easy to attach to the LiPo but you have to remove the heat shrink covering first. The black wire at one end of the plug is soldered to the negative battery terminal (where the Black Battery lead is attached), the red wire at the other end of the plug is soldered to the positive battery terminal (where the red Battery lead is attached) and the other wires are soldered to the positive terminals of all the intermediate cells. You have to have the correct balancing lead for the number of cells in your Lipo. Like for a 3 cell LiPo you need a 4 wire balancing lead. I was lucky my LHS had them in stock. All that is left to do is plug the connector into the equalizer with the black lead adjacent to the arrow on the equalizer (when you get one you will know what I mean). The equalizer than plugs into the battery charger (set for the correct number of cells and maximum charging current as usual) and the battery is plugged into the equalizer. Switch on, stand back and watch the light show as the LEDs show which cells are out of balance.

Best of luck!

Mark.

[two-hill]

I've got a 3S 2100 Twenty pack with a voltage of 8.2V. If I try charging it at a low rate, outdoors for safety, is there any chance it will recover?

I had it connected to a Jeti ESC with an on-off switch. I left it for a couple of days with the switch off and the battery leads connected. I went back and read the instructions again. Now I know what it means when it says the switch doesn't isolate the battery. I guess the power gets used up in the ESC even when it's idling.

Phil

[aeajr]

Originally Posted by two-hill

I've got a 3S 2100 Twenty pack with a voltage of 8.2V. If I try charging it at a low rate, outdoors for safety, is there any chance it will recover?

I had it connected to a Jeti ESC with an on-off switch. I left it for a couple of days with the switch off and the battery leads connected. I went back and read the instructions again. Now I know what it means when it says the switch doesn't isolate the battery. I guess the power gets used up in the ESC even when it's idling.

Phil

8.2V should be OK. My understanding is that 2.5V per cell is the critical number. I would charge it, perhaps at 1/2 C if you are concerned and be sure to keep an eye on it. but I would bet it is fine UNLESS one cell is low. Then you could hvae a problem.

[zackesch]

do ballanced packs have less risk of combusting for an unknown reason? are ballanced packs safer? i was looking at getting greatplanes equanox ballancer with there brand lipo and using a e-flite charger, the slectra. is tht a good combo, the charger has banana plugs that will work with the ballancer.

[aeajr]

Yes, balanced packs should be safer.

The risk with multicell packs is that one of the cells might be much lower than the others. On discharge it might fall below the critical 2.5V, perhaps becoming unuseable. Or a cell might be over charged as the charger tries to bring the rest of hte cells up to full charge.

Balanced packs won't eliminate all problems, but they can address these, the most common problems with multi cell Lithium packs.

[two-hill]

Originally Posted by aeajr

8.2V should be OK. My understanding is that 2.5V per cell is the critical number. I would charge it, perhaps at 1/2 C if you are concerned and be sure to keep an eye on it. but I would bet it is fine UNLESS one cell is low. Then you could hvae a problem.

Thanks for the info. I tried charging at 0.8A using my Triton charger and the PolyQuest balancer. It started charging, but shut down after a few minutes, with a "low battery voltage" warning. I waited a couple of minutes and tried again. Success! It took 2180mAh. The battery was new and had only been used for some servo adjustments, so I was very relieved not to have to cough up another $80.

[neu]

This is a really important topic! Thanks for everybody working with it! I knew that LiPo batteries are dangerous, but after reading these, I'll pay more attention in the future, even though I though I'm cautious enough.

Thank you guys, you're doing a great job!

Greetings, neu
www.carrierbuilders.net

[t00fatt]

Do LiPos like to be stored with a charge or with out?

[hoppy]

1/2 charge at cool temps. 3.85V+/- per cell

[roosevelt]

I must not be using the correct terminology in the search cause I come up empty or w' vague answers to this question so here goes-

What is the most efficient way to connect 2 separate lipo packs in parallel or series?

Obviously I can make a Y connector that connects the 2 cells to the esc but that means alot of connectors and wire. I would like to separate them for individual use or to swap from series to parallel.

Also what is the best way to charge these.?

In series, parallel or separate? I intend to use several 3s and 2s 1650 mah 8c packs. And depending on the application I will be running them separate, in series or in parallel.

Thanks

[rorywquin]

If you connect them in series you are going to double the voltage. If you connect them in parallel, you are going to double the capacity (assuming both packs are the same).

What is your intended application?

[roosevelt]

I just realized that in series the c rating would probably defeat the benefit of added voltage. So for this app. I would be running them in parallel on the wing in the avatar to the left. The c rating stays the same regardles, right?

[roosevelt]

OK, I connected 2 2s 2000mah lipos in parallel. Runs alot cooler and longer. But I've used them twice and no LVC on cc 35 w' 6.0v cutoff.

I checked voltage after flight it was 7.2v both times and the new 2s2p 4000 pack took 4100 and 4198 mah respectively.

Am I over discharging these or what? When the packs were separate I would use 1900- 2000mah and the lvc cutoff at 6v. Afterwards the voltage was 7.2.

I ran the new pack at wot hoping the lvc would kick in but it didn't. How come I'm getting so much out of these and volts are still above 7 volts? All cells are well within .10mah of each other??????

[z-matrix]

Originally Posted by roosevelt

OK, I connected 2 2s 2000mah lipos in parallel. Runs alot cooler and longer. But I've used them twice and no LVC on cc 35 w' 6.0v cutoff.

I checked voltage after flight it was 7.2v both times and the new 2s2p 4000 pack took 4100 and 4198 mah respectively.

Am I over discharging these or what? When the packs were separate I would use 1900- 2000mah and the lvc cutoff at 6v. Afterwards the voltage was 7.2.

I ran the new pack at wot hoping the lvc would kick in but it didn't. How come I'm getting so much out of these and volts are still above 7 volts? All cells are well within .10mah of each other??????

hi,
if your LVC is working perfect then you have nothing to worry about,
you have higher voltage under load because the internal resistance of your pack is half as much.
So, voltage drop is half as much.
You have higher energy efficiency, because of the lower current drawn from each parallel pack,
if your pack has a capacity of 1900mAh @10C and now you use it @ 5C you can get about 2100mAh out using the same LVC.

There is a possibility you can over discharge your pack using a cutoff voltage that was empirically determined for high discharge rates, you can verify this by measuring the no-load voltage after an LVC run, it should be about 3.6V (under no-load).
under 3.3V it is no good.