Charging LIPO batteries

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  • #1
Lookitsame
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TL;DR Summary
Charging Lipo question
Hey, I just purchased a lipo battery and was wondering if I wanted to charge it would I be able to use a 6v/3amp charger for the following lipo 7.4v/10amp. I'm pretty sure I would be able to.

LIPO BATTERY:
https://www.robotshop.com/ca/en/74v-2000mah-5c-lipo-battery.html

What is the general rule of thumb for charging lipos? Charge at .5c and don't go over the voltage

Thank you so much
 

Answers and Replies

  • #2
Baluncore
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  • #3
Borek
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Actually 7.4 V LiPo requires a charger capable of charging up to 8.4 V. That's the voltage of full 2S battery.
 
  • #4
essenmein
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Another thing to keep in mind is that Li ion batteries are somewhat picky when it comes to overcharging.

If you have little or no experience with this I would strongly recommend acquiring a purpose built 2 cell battery charger, lest you burn your house down or cause injury.

 
  • #5
Lookitsame
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Hey, thanks everyone for your comments, taking everything in I'll get a battery charger meant for a 7.4v lipo (https://www.robotshop.com/ca/en/74v-lipo-battery-charger.html) I would also get a BMS but I was planning to hook up the leads of the battery to a buck convertor that would give me an output of 12V to power a 12v/3a device (https://www.amazon.com/dp/B00PELQA7M/?tag=pfamazon01-20).

Would it be ideal to still use a BMS or can I get away without using one

Also in response to Baluncore I don't have access to the internal connection and from reading the reviews on the battery there are several wires for different connection options also there is no datasheet for this device online so I'm going off the assumption that there is no internal management module.
 
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  • #6
berkeman
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taking everything in I'll get a battery charger meant for a 7.4v lipo
Thank you for that. IMO, batteries (especially advanced chemistry batteries) are just too dangerous to try to do DIY chargers, unless you have a very strong EE background and are willing to do a lot of research into the appropriate recharging technologies.
 
  • #7
Baluncore
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... I don't have access to the internal connection ...
Then you cannot connect a BMS.

... I was planning to hook up the leads of the battery to a buck convertor that would give me an output of 12V to power a 12v/3a device ...
You need a BOOST converter, NOT a buck converter. A buck can only cut = reduce the voltage.
Avoid an LED voltmeter if you can as it wastes battery energy.
 
  • #8
hutchphd
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Summary:: Charging Lipo question

Hey, I just purchased a lipo battery and was wondering if I wanted to charge it would I be able to use a 6v/3amp charger for the following lipo 7.4v/10amp. I'm pretty sure I would be able to.

LIPO BATTERY:
https://www.robotshop.com/ca/en/74v-2000mah-5c-lipo-battery.html

What is the general rule of thumb for charging lipos? Charge at .5c and don't go over the voltage

Thank you so much

The battery you pictured does have a BMS port (the 3 wire one).

Why did you get a 2s battery if you need to supply 12V ? One more cell (3S) gets you above 11 and that will probably do fine...these batteries don't go low until the very end of charge.
I concur that building a charger is a bad idea.
These batteries hate to be completely discharged and seem to store long term best with ~60% charge
 
  • #10
Lookitsame
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You need a BOOST converter, NOT a buck converter. A buck can only cut = reduce the voltage.
Avoid an LED voltmeter if you can as it wastes battery energy.
Thank you for pointing that out, that clears things up now I'll go ahead and get this one (https://www.amazon.com/dp/B00MIJL4OC/?tag=pfamazon01-20).

Why did you get a 2s battery if you need to supply 12V ?
The main reason is this one weighs much less than the 3s battery and since weight is a big issue for my project I decided to get the 2s battery.

EDIT: Thank you, everyone, for your responses I decided I am getting this (https://www.amazon.com/TalentCell-Rechargeable-3000mAh-Lithium-External/dp/B01M7Z9Z1N/ref=sr_1_9?crid=3PCA2G1QMMSZ6&keywords=battery+management+system+12v&qid=1587867792&sprefix=battery+manage,aps,190&sr=8-9) it would be a 100 times easier as it outputs the exact voltage and current and also seems it has a BMS embedded within in. Learned a lot from your responses, great learning experience thanks a lot :)
 
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  • #11
Baluncore
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Thank you for pointing that out, that clears things up now I'll go ahead and get this one
That is a better choice.
When you get it, connect a few hundred ohms to the output and adjust the constant voltage CV to your required regulated output voltage. Then adjust the maximum current limit needed with CC, which will limit short circuit fault current and prevent regulator overheating.
 

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