Never charged a LiPo before. Help me out with a few questions....

mrfurious40k

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Hey all,

I'm back in the RC game after a 10(or more) year break. I bought myself a Nero and some Onyx 3s 5400 50c packs. My chargers for the moment are a pair of Duratrax Li-24s. They are a very basic but well reviewed balance charger and seem like they'll suit my purposes for the time being. They charge at 1, 2 or 3 amps. From what I've read, I should be able to charge my packs at the 3 amp setting with no issues. Is that correct?

Since the chargers don't have a discharge setting, what's the best way to charge or discharge the packs before storage? Is storing them with a full charge dangerous? What do most folks do with them?

I raced with NIMH so this LiPo thing is kind of blowing my mind.

Thanks
 

MSgt

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First read up on Lipos. Here are a couple of good guides.
http://rogershobbycenter.com/lipoguide/
https://www.maxamps.com/lipo-care.php
http://www.thinkrc.com/faq/proper-lipo-battery-care.php

That charger would make me nervous. I really like more info when I'm charging batteries. Check out this thread for battery charger info: https://arrmaforum.com/threads/recommend-me-a-battery-charger.1079/

With what you have, I'd grab something like this: https://www.amazon.com/Tenergy-Inte...r&refinements=p_85:2470955011,p_72:2661618011 to help keep tabs on your batteries.

I'd also advise getting a lipo charging bag ($5-$15) and at least a cheap metal cake pan to set them in while charging to help minimize/contain damage if something does go wrong. They should be stored a little over half charge.
 

mrfurious40k

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Thanks. I have bags for charging and storage. I read up on the chargers quite a bit before my purchase. They aren't perfect but are well reviewed and seem safe. Not much room for user error anyway. I'll be upgrading as soon as I recover from my initial purchases.
 

WoodiE

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@mrfurious40k to answer your question first, LiPo storage voltage is 3.85v per cell. If your charger doesn't balance or discharge then a neat tool to get is the AOK 3in1 Battery Balancer Discharger Voltage Tester. Even if your charger DID balance this tool is nice to have as it will easily check the voltage of your batteries.

Regarding your charger itself, you went out and bought yourself one heck of an RC, decent batteries then totally cheaped out on a charger. Sadly also on one of the most important tools.

You said your batteries are 5400mAh 3s LiPo packs. Most people are going to recommend to charge LiPo batteries are 1C to 2C which to find out how many amps you'd need you simply divide your mAh by 1000. So in order to charge at 1C you'd need a charger that can charge at 5.4amps or 10.8amps for 2C.

In addition, if your charger doesn't have enough watt power it won't charge at the amperage you are hoping. In this case we already know the Duratrax charger can only charge 1-3amps so we already know we're not going to get anywhere near the 5.4 and certainly not even close to 10.8amps. But to find out how many minimal watts you'd need you would multiple the needed amps (5.4) by 11.4V (voltage of 3s LiPo) and get 61.5watts (5.4amps x 11.4V = 61.56 watts).

All this means is this charger is not suited for these batteries... it's going to take forever to charge them, like around 9 hours or more - since you're not even close to 5.4 amps charging means you're not going to be anywhere near 1C charge rate as many recommend.

Without a doubt I'd return it if you can and get yourself a charger that can charge your battery sometime within the same day. ;)

A great charger that will charge are you needed values would be the Dynamite Passport Ultra Touch, for just about $100.
 

Jerry-rigged

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The Venom charger would work. The onyx 245, I would pass on.

One of the big "got'ya's" with chargers is the charging wattage. The Venom is 80W per channel, 140W total. The onyx is 40w per channel, 80w total. When you get into 3s, 4s, and 6s batteries, you need a charger than can handle bigger watts.

For your 3s, 5400 mah batteries, you need a charger than can supply 60w per channel to charge at 1c. With 80W, that venom will be up to the task, however, the 4w Onyx will not.

Personally, this UP120 charger is on my short list. With 120w per channel, I will be able to charge 2x4s 5000mah packs at 1c the same time.
 

mrfurious40k

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Thanks for all the help! There's a lot to this I wasn't really anticipating. I ended up ordering the Venom. It seems to have what I need to get me started and with the Tower coupon it was financially doable after just absorbing the cost of jumping back into RC with a big brushless truck and batteries.

I'll either part out some of the banana plugs that come with the Venom and sell those Li-24s on ebay or keep them as spares in case I have a failure and need something to get me through.

First read up on Lipos. Here are a couple of good guides.
http://rogershobbycenter.com/lipoguide/
https://www.maxamps.com/LiPo-care.php
http://www.thinkrc.com/faq/proper-LiPo-battery-care.php

That charger would make me nervous. I really like more info when I'm charging batteries. Check out this thread for battery charger info: https://arrmaforum.com/threads/recommend-me-a-battery-charger.1079/

With what you have, I'd grab something like this: https://www.amazon.com/Tenergy-Intelligent-Capacity-Discharger-Resistance/dp/B0178P8H9U/ref=sr_1_167?rps=1&ie=UTF8&qid=1470356901&sr=8-167&keywords=LiPo+charger&refinements=p_85:2470955011,p_72:2661618011 to help keep tabs on your batteries.

I'd also advise getting a LiPo charging bag ($5-$15) and at least a cheap metal cake pan to set them in while charging to help minimize/contain damage if something does go wrong. They should be stored a little over half charge.
Thanks for all your help and the links, MSgt. I appreciate you taking the time.
 
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mrfurious40k

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OK, I received my Venom Pro Duo and I'm getting familiar with the charger to get my packs charged up but I'm getting really confused about things the more I read. For charging at 1C I should be setting it a 5.4 amps because they at 5400mah packs. I get that. Balance charging each cell to 3.7 volts for a total of 11.1 volts when the pack is charged. (3.7 x 3 = 11.1). That makes sense. Then I start reading about storage charges and they recommend 3.85 volts per cell. That's 11.55 volts. Which is more than a running charge. What does the charger actually put in the pack in "Storage" mode? If I program my own storage mode what should I be shooting for with 3s 5400mah packs?

Thanks
 

Jerry-rigged

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you are confusing "nominal voltage" with real world values.

Nominally, Lipos are 3.7v per cell. so a 3s is 3 * 3.7 = 11.1

"Fully Charged" lipos should be 4.2v per cell. So a 3s would be 12.6

"Dead" - a lipo should never be below 3.0v* per cell. I try to set my LVC so they end up about 3.5c resting.

"Storage charge" - often quoted as 3.85v per cell, but IMHO, the exact value is not too important. Just not dead, and not fully charged. I think my Hitec X1 was set to 3.8 from the factory, and I have never changed it. Infact, most of the time, I will stop the storage charge somewhere around 3.75 or 3.85 (depending on whether I am charging or discharging) to get the next battery going.

People smarter than me say that below 3.0v, a lipo cell can be permanently damaged. People braver than me say they have taken cells down to below 2.0v and they were ok, so long as they don't stay there long, charge them ASAP. YMMV.
 

mrfurious40k

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Thanks Jerry-Rigged. I just pulled my packs from the box and hooked them to my tester. Each cell is showing greater than 3.7v from the factory. Should I just throw them in and run them to the cutoff and then charge them?

And when I do charge is it best for the packs to keep them at 3.7 per cell? I'm just playing in the yard so safety and longevity is my goal with the packs. I'm not racing and I have 4 so I can run back to back and probably be broken or ready for a rest by the time I've run through two sets of packs.
 

Jerry-rigged

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I run my batteries off of storage charge all the time, when i want a "quick RC fix" :) Run time will be half, but it should not hurt anything. When I am going bashing, though, I will top them off. Herein lies another advantage of storage charge - it cuts charge time in half, as the batteries are already half charged! Woot!

:)
 

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