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Old 01-05-2011, 11:47 PM   #1
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Default First time LiPo user

Hi.

I have Acorn 3800mah 36c hardcase Lipo.
Charged it for the first time using a Lipo charger (balance charging),
peaked at 2200mah. Used it in racing and recharged it again...
peaked again at 2000mah+. Why is it not peaking at 3800mah?
I set my charger to 3.8amps, or should I lower the current to 3.5
or something?

Sorry for this newbie inquiry...
Im kinda late converting to these new batts.
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Old 01-06-2011, 12:12 AM   #2
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i think what you see is the current that was topped up into the battery, maybe. if you charge at 1C, which is 3800 mAh, then the charger should peak (as most chargers would charge on constant amps first before moving to constant volts) at 3800 mAh and it would slowly go down as you charge until it reads zero or close to zero amps, whereas you will see the voltage of the cells go up with time. hope this is clear.
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Old 01-06-2011, 12:22 AM   #3
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Quote:
Originally Posted by rshair View Post
i think what you see is the current that was topped up into the battery, maybe. if you charge at 1C, which is 3800 mAh, then the charger should peak (as most chargers would charge on constant amps first before moving to constant volts) at 3800 mAh and it would slowly go down as you charge until it reads zero or close to zero amps, whereas you will see the voltage of the cells go up with time. hope this is clear.
Ok, so you mean to say is it still has some 1500mah+ left in it before I
charged it again? The volts stopped at 8.4v and the current went down slowly
(.9, .8, - .2 amps) then the charger beeped (batt full). I charge at 1C.
So is this normal? I came from ancient NiHM, and when I charge my 4600mah,
it usually peaks at 9v+ and 4700mah+, charging at 4.7amps.
So is this acceptable?
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Old 01-06-2011, 12:42 AM   #4
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you can put back to the battery only what you used. So if after race you put 2200mAh into the battery it means you still have 1600mAh left . thats normal.

I use 5200mAh battery and charge back only about 1500mAh after each run

you would have to run your car till the lipo cut off kicks it (I hope you have it set on your ESC) than you would charge back those 3800mAh (however it depends on the quality of the Lipo as some ESCs have the LVC - Low Voltage Cutoff - set higher than 3V per cell and depending how well the battery holds Voltage under Load the battery can get bellow the LVC limit without being fully discharged.

But this is not that bad as LiPos should not be fully discharged as it shortens their life.

For example you can do 100 full charge - discharge cycles or 300 charge - discharge to 50% cycles.

Hope it's clear.
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Old 01-06-2011, 12:46 AM   #5
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nimh/nicad, those were the days, i still have my charger & discharger from then. dont use them anymore so its a little piece of history for me

for the lipo, yes its fine. you should not run your lipo to lower than 3.0V per cell anyway, i myself try to stop playing when each cell is around 3.6V, wait till it cools down and then re-charge again. you should invest in one of those lipo checkers or if you have an ESC with a programmable lipo cut, you should use it. always store your lipo at around 3.7 or 3.8 V per cell, it helps. i think there is a section on lipos here, do a search, there are many valuable posts in this forum.
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Old 01-06-2011, 01:18 AM   #6
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I use Novak XBR BL system with Lipo cutoff activated.
When the cut off kicks in, the throttle momentarily cuts out and
in again. Then I know I have to stop. Then I recharge it again
while cleaning the car. It always peaked at 2200mah+ and not 3800mah.
I didnt research about Lipo thread/posts here since itll cover the old and
new knowledge about Lipos. Just wanted to know if I have a bad issue
with my new batt and charger.

Last night I bashed on the streets till I reached the cut off and just left
it since Ill be playing again tomorrow, is this practice ok? I mean not
recharging it again? So like leaving it 48 hours uncharged? But I use
storage charging program (feature in my charger) if I know I wont be using
it for 3 days or more. Or should I charge it at once after using it?

Thanks guys for sharing.
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Old 01-06-2011, 01:36 AM   #7
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I'm a racer only kind of guy but this is how my batteries are handled each and every week.

I charge both batteries before racing, using 1 to practice with before racing. Charge it again before racing starts. I don't wait for it to cool down because they only get the slightest bit warm when you run the pack down to 6.6 volts roughly. I'll run 1 pack for 2 heats of 6 minute runs, remove from the chassis and put it away for the night. Install the next fresh pack and run the 6 min main. Once racing is done for the night I unplug the battery from the esc and leave them alone until next week and redo the whole process.

You should be okay with your lipo with how you are going. As for the only getting to 2200mah peak charge, make sure your charging your battery in the correct battery mode, sounds like you might be charging in the 1s battery mode instead of the 2s mode. When I charge my 2s 35c 3800mah pack I usually only see a 2000-2500mah charge input unless I drained it way low, then I'll see a peak charge of 4000-4300mah input. On my 5000mah packs I only see a recharge mah of whatever was taken out of the pack from the previous day of racing.
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Old 01-06-2011, 01:40 AM   #8
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Also, I only put my packs to storage charge when I know I will not be using a battery for over 3+ months. Once you do that all you need to do is check the voltage every 3-4 weeks, leave them in a cool place, and they will be good to go.
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Old 01-06-2011, 01:57 AM   #9
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Check the charger setting - my charger has a 50%, 95%, and competition car mode. When I set my charger to 100% mode, it comes close to expected capacity. Maybe your charger is similar and might not be set to 100%
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Old 01-06-2011, 01:57 AM   #10
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Ok, thanks for sharing, bro.

Im charging at 2S mode, 1C. Me thinks my esc cuts out really early
like 6.8v thats why it still has plenty of mAH left. It's an old BL esc
anyway (Novak XBR with Lipo Cutoff).

So Ill just leave it alone after every use if Im using it thrice a week?
And just rely on my ESC's cutoff or should I monitor them every non-race
days?
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Old 01-06-2011, 01:59 AM   #11
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Quote:
Originally Posted by macavant View Post
Check the charger setting - my charger has a 50%, 90%, and race-charge mode. When I set my charger to 100% mode, it comes close to expected capacity. Maybe your charger is similar and might not be set to 100%
Hey thanks, Ill check it out if it has this feature. This is what Im using...
http://os.3racing.hk/products.php?products_key=3803
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Old 01-06-2011, 03:09 AM   #12
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i used to have a HOT power lipo charger from 3 years ago, it would only charge up to 5 amps max. it would only tell you how much mah is put in from the charging start point, not the total in the battery, hence iw ould be getting mah figures like you, a 3200 shows 2000mah at full charge.
i recently changed to a dualsky n61e charger that will charge up to 10 amps, its definitely a more advancved charger, no matter how much mah is still left in a pack, you will know immediately when you start charging, hence my 4200s always show a reading of 419X to 42XX when fully charged.
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Old 01-06-2011, 05:57 PM   #13
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Ill try to get better lipo charger that has over 5 amps charge.

Any suggestions?
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Old 01-06-2011, 09:48 PM   #14
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there are a few out there and really depends on what your LHS stocks. i personally like my icharger 206B, it is small, is capable of charging up to 300W or 20Amps. good enough for me to bring to my local track.
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Old 01-07-2011, 12:35 AM   #15
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Guys you need to do some reading and get a full understanding of the basics of batteries and charging them.....

To start with the charger should be smart enough to tell you if your charging a 2s in 1s mode as you need a balance wire to charge a 2s.

Now when you are trying to get your charger to tell you the full capacity of your battery u need to discharge the battery at 5amps down to 6volts and then fully charge the battery to 8.4volts at 1c. 1c = 1 times capacity of the battery. EG 5000mah = 5amps. but they dont like being discharged down that low all the time but every ten times u charge them it doesnt hurt just to do it as it will help with the internal resistance and keeping it low. The lower the internal resistance and the closer the resistance is between the cells will be a better pack as it will give up its power alot better than a pack with high resistance.

now you can charge higher but that is only if your battery manufacturer allows this to happen.
Once the battery is fully charged your mah reading will be the capacity of your battery. Usally it goes over the capacity. Cheaper cells and batteries will be all over the place so dont expect to much from them.

Some advice tho dont spend a heap of money on great batteries but a 20 dollar charger as that is just stupid. The charger makes all the difference by looking after your batteries.

Lipo is a great technology but dont abuse it as it will come back to bite you.
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Last edited by jjfo80; 01-07-2011 at 01:01 AM.
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