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Old 03-25-2012, 11:48 AM   #1
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Default rookie LiPo question

I have recently gotten back into the hobby after a 20 year hiatus.

I am going to be running LiPo batteries, in fact I have already purchased 3 of them.

I have done a lot of reading on the web to try and understand this new to me technology and I think I get the basics and I understand how important it is to be safe with these, that is why I am posting here.

The batteries that I have purchased are GENS ACE 4000mah 2S1P 7.4V 30C Hard Case Lipo Battery ROAR Approved.

The charger I have is the Thunder AC6.

I have used it once for 1 charge after reading the instructions and watching some vids as well and there are a few things Im confused about.

After setting it for a 2s battery and charging it at 4.0 amps the charger recognizes it as a 2s battery.

but it charges it to 4.2v per cell with an end voltage of 8.4v and it has a capacity cutoff of 5000mah even though I set it at 4000mah.

Im not sure if all this is wrong or not.

Since this is the GENS ACE 4000mah 2S1P 7.4V 30C is it overcharging since it it charging it to 4.2v per cell for a total of 8.4v?

It just charged for 60mins and it says its full at 8.4v with 03051 being put into the battery.

The battery is not even the slightest bit warm.

Am I doing this all correct?

Thanks in advance.
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Old 03-25-2012, 12:06 PM   #2
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You are doing it right. Lipo cells charge to 4.20 volts per cell.
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Old 03-26-2012, 01:00 AM   #3
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7.2 is a middle voltage for the pack, and what you'll see 2S LiPo packs listed as.

Fully charged is 4.2 per cell.
Used, they go down to 3 per cell, but generally you don't want to go below 3.2 per cell to maintain the life of the battery.
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Old 03-26-2012, 11:13 AM   #4
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You may be used to nimh or nicd from the past but lipo batteries do not get warm when charged like the others do. So you are putting just over 3000mah into a 4000mah battery, sounds good.
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Old 03-26-2012, 12:35 PM   #5
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If the Lipo gets warm that's when you have a problem. I have 1 of those chargers and they work pretty good for the money. You have done everything correct.
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Old 03-26-2012, 01:21 PM   #6
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everything looks good....as everyone has said rules of thumb

3.7v normally calculated cell voltage....
1s=3.7v
2s=7.4v
3s=11.1v..etc..

4.2 fully charged cell

3.2 cell voltage cutoff

I think the gen ace batteries can be charged at a higher C rating....
which mean... If it is a 4000Mah pack.... a 1C rating would be 4.0(4000x1) charging amps.... a 2C rating would be (4000x2)=8.0amps....and so on....
but the higher the C rating you charge at.... you dont get as good of a charge....but will charge faster just keep temp in check
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Old 03-27-2012, 03:47 PM   #7
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Sounds like you are doing everything right should be no problem.
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Old 03-28-2012, 12:53 AM   #8
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Quote:
Originally Posted by elmer84 View Post
everything looks good....as everyone has said rules of thumb

3.7v normally calculated cell voltage....
1s=3.7v
2s=7.4v
3s=11.1v..etc..

4.2 fully charged cell

3.2 cell voltage cutoff

I think the gen ace batteries can be charged at a higher C rating....
which mean... If it is a 4000Mah pack.... a 1C rating would be 4.0(4000x1) charging amps.... a 2C rating would be (4000x2)=8.0amps....and so on....
but the higher the C rating you charge at.... you dont get as good of a charge....but will charge faster just keep temp in check
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Old 03-28-2012, 06:50 AM   #9
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lol sorry.... just rambling off the top my head
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Old 03-28-2012, 02:46 PM   #10
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Many of the guys who do a lot of testing believe that is the case, higher charge rates donít result in quite the same amount of capacity. But itís typically a very small difference with lipos, unlike most other battery types.
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Old 03-28-2012, 07:57 PM   #11
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Default Fully charged Lipo's

I believe the general consensus is that a one cell Lipo not used should be stored at its nominal voltage of about 3.8 volts. But if a one cell Lipo is fully charged to its 4.2 volts and left that way for, say, a month, what happens to the battery? Does it slowly loose voltage over time? Lost how? By heat?

Can the fully enclosed hard shell start to weaken and maybe expand and even erupt into possible flames? Once is swells, is that a sight that it could fail sooner than a non-swollen battery?

Several guys at the track today say they store their Lipo's fully charged.

Personally, I store all my Lipo's in a metal ammo can at the storage voltage of 3.8 volts per cell. But if I charge up 5 batteries fully in the morning and only use 2 that night, should I take the remaining three and run the store mode on the charger to reduce them to 3.8 volts from 4.2 volts? Seems like extra work but am I helping the battery last longer?

Is there a problem charging and then discharging to storage voltage frequently? How many times can I charge, use, recharge, etc a Lipo?
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Last edited by TakeAim; 03-28-2012 at 08:18 PM. Reason: adding more text
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Old 03-29-2012, 12:15 AM   #12
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LiPo batteries loose part of their lifespan every moment they are fully charged...be it for the 25 seconds from charger to your car running or be it over a month in storage. If they are stored that month, they just shorten the lifespan that much more.

A swollen battery also decreases the lifespan of the battery, as the swelling is basically a sign that damage has been done (sometimes by too rapid discharge, sometimes by over charge, sometimes from sitting fully charged on the shelf and not having any other place to send the energy).

A general rule that will give you the longest lifespan should be roughly "if it is going to sit for more than part of a day or overnight, don't leave it fully charged, pull it down to storage voltage". Like any battery, charge/discharge cycles reduce the life of a LiPo, but this is generally really really minimal on a LiPo unless it is done at a fast rate (such as using that burst C rating), so it is better to put half a cycle on the battery than to leave it for a day charged fully. Best is to just not charge it until you want to use it.
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Old 03-29-2012, 04:56 PM   #13
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Leaving them fully charged also increases the internal resistance, which reduces voltage under load, punch/power, and the discharge capability (basically lowers C).
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Old 03-30-2012, 05:39 AM   #14
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Suppose I fully charge up 2 Lipo batteries. I go to the track and run just one. When returning home, should I take the unused one and discharge it to storage voltage because I won't be back at the track for, say, one week?

I also have the used battery with how much voltage I don't know. Should I put it into storage mode too, which might actually add a little voltage to bring it up to the 3.8/volt nominal?
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Old 03-30-2012, 09:22 AM   #15
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Quote:
Originally Posted by TakeAim View Post
Suppose I fully charge up 2 Lipo batteries. I go to the track and run just one. When returning home, should I take the unused one and discharge it to storage voltage because I won't be back at the track for, say, one week?


^^^^I would

I also have the used battery with how much voltage I don't know. Should I put it into storage mode too, which might actually add a little voltage to bring it up to the 3.8/volt nominal?
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I store all my packs at 7.4v (2s) have done so since day one. Nice part for me is that's what they come off the track at.
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