Quick Li-Po Question about Discharge and Voltage

[Mirodasc]

will a 7.4 V 15C Lipo battery function the same, or at least similar to a standard 8.4v NiMH? Does the discharge rate make up for the voltage, or will it starve my AEG?

Thanks Guys!

[ILLusion]

It'll function more like a 9.6v Ni-Cad.

Do NOT discharge lipos!

[Con Murder]

The 7.4 is best in an AEG without markIII mosfet. Make sure you get a battery monitor of some sort cuz as illusion stated a fully drained li-po is a 'never-be-recharged' li-po.

Also invest in a good charger for them, and check the mah to estimate the run time should you wonder.

[Jackarutu]

One can’t help but have a lot of respect for Illusion due to the simple fact of all the help he has dished out here on the forum of very useful information and his experience of working with Airsoft. So when I say I don’t think he meant literally not to discharge your Li-Pol battery pack it’s not that I know him personally and have tons of experience on how to interpret what he says but rather it’s because of my understanding of how Li-Pol tech works.

To say to someone, “here’s your Li-Pol but don’t discharge it” is the same as saying don’t ever use it! To use a battery is to discharge it. What I think Illusion may have meant to say was don’t totally discharge a Li-Pol below a certain limit. And here’s is why.

The voltage of a Li-poly cell varies from about 2.7 V (discharged) to about 4.23 V (fully charged), and Li-poly cells have to be protected from overcharge (thought I would throw in the overcharge danger also) by limiting the applied voltage to no more than 4.235 V per cell used in a series combination. Overcharging a Li-poly battery will likely result in explosion and/or fire.

Next during discharge on load, the load has to be removed as soon as the voltage drops below approximately 3.0 V per cell (used in a series combination), or else the battery will subsequently no longer accept a full charge and may experience problems holding voltage under load.

Now the above information is dated and recent tech has somewhat changed in regards to Li-Pol but the relationship is approximately the same. Starting in about 2007 the early cells required longer charge times and slower maximum discharge rates. But recent improvements offer a much faster rate of charge with some cells taking only about 5 minutes to reach 90% of charge capacity and have increased maximum discharge currents from two times to 15 or even 30 times the cell capacity.

Thus it’s very important to read and be familiar with the details of your particular battery pack. And this topic is also a good argument on using a MOSFET that shakes your gun when the Li-Pol has became dangerously discharged to remind you to change the battery.

And even as I write this tech changes so fast these day this info may be outdated.

[ILLusion]

Sorry, by "don't discharge it", I meant NOT to run it through a charger's discharge cycle.

[ThunderCactus]

It also depends on the thickness of the wires.
I bought 3 types of LiPo's, all the same 7.4v 20C 1600mah LiPo. But all with differing thicknesses of wiring. Each battery outputs the same power, but the thinner wires choke out your amperage.
You'll want 14 gauge wires. It may seem overkill to some people, but if you ever get around to upgrading your wiring harness and switching to a MOSFET switch, it makes a big difference!

[Death March]

You to run a balancer/interface unit with it if you charger does not have one built in to it. I have a Electrfly LiPo Balancer/Interface that runs with my T.C. 1030 charger. The Interface unit will overide the charger to protect the LiPo.

[Whiskey]

Originally Posted by Mirodasc

will a 7.4 V 15C Lipo battery function the same, or at least similar to a standard 8.4v NiMH? Does the discharge rate make up for the voltage, or will it starve my AEG?

Thanks Guys!

7.4v lipo 15c, what is the Mah ?, having the right lipo is very dependent on having the correct capacity (Mah) and "C" value. those are the things that will tell you if that battery has the amperage capacity to satisfy what your AEG is requiring to run @ optimal performance, which could be 2 totally different storys for differing AEG's, example: you are running a large spring (sp120+) in your AEG, opposed to a AEG running somthing a little more saner (m100). That AEG running the big spring will require much more amperage to complete that firing cycle than the one using the m100. Sooo this means understanding how lipos work and what there rating really means. First off take your Mah capacity: (example: 2000Mah) and times ( X ) that by the "C" value (example: 30c) =6000, now take 6000 and devide that by 1000 = 60, that is the total amperage that battery can supply, 60A, now thats alot of head room for amperage than a lipo rated 7.4 15c 2000Mah. Currently my SLR gets her juice from a 7.4v 2000Mah 20C (continuous) 30C(burst), and its perfectly at home in my CQC 552 with a 1J spring in it too, as well it spins either gun quicker than a 9.6v nimh can. hope this helps.