Charging a 300mAh 3.7V battery

Thread Starter

Kelvin Lee

Joined Oct 22, 2018
110
Dear Sir/Madam,

I have a 300mAh 3.7V battery, I think it is a LiPo battery. I have the charger EV-PEAK E6 ( https://www.ev-peak.com/prodcuts-item/ev-peak-e6/ ), it allows charging the battery from 0.1 to 1.0A, may I know at what charge current I should set is the best practice and good to the battery life? Is there any measurement theory behind?
20191112_212414.jpg
Best regards,

Kelvin
 

Yaakov

Joined Jan 27, 2019
1,604
This is probably the wrong forum for this thread, but LiPo batteries can generally be safely charged a 1C, where C is the AH capacity of the battery. So, in your case, in the absence of a data sheet specifying otherwise, charging at 300mA or less is a safe bet.
 

Thread Starter

Kelvin Lee

Joined Oct 22, 2018
110
This is probably the wrong forum for this thread, but LiPo batteries can generally be safely charged a 1C, where C is the AH capacity of the battery. So, in your case, in the absence of a data sheet specifying otherwise, charging at 300mA or less is a safe bet.
Thanks for your reply. can I say if my battery is 6000mAh, the 1C means 6A?
 

Yaakov

Joined Jan 27, 2019
1,604
In principle, yes. But that is a maximum rate and usually .5C is the recommended standard charge rate. You must also be sure the ratings of the batteries are accurate, since they are often inflated for marketing.

Generally, 1 to 1.5A is safe, but LiPo packs are very dangerous so be careful.
 

Audioguru again

Joined Oct 21, 2019
278
Your charger that has too many setting will probably cause an explosion and a fire.
I charge my Li-PO batteries with chargers that were designed only for them. If I ever buy HV batteries then I will buy a charger only for HV batteries.
 

oz93666

Joined Sep 7, 2010
672
And be careful not to charge a LiPo battery to greater than 4.20 volts. Higher voltages can cause catastrophic battery failure (flames). https://batteryuniversity.com/learn/article/charging_lithium_ion_batteries
Lot's of fear mongering again about Li-po ... these are NOT dangerous unless you bang a nail through a fully charged one ....

The 4.2V upper limit is one suggested by the manufacture ...it's all a compromise between cycle life and energy stored ...Satelights need max cycle life .. they only charge to 3.93 and get 3,000 cycles this way ... but only hold 65% of energy they would if charged to 4.2

charging to 4.2 will only give 400 cycles (before capacity falls to 80% new)

You can safely charge to 4.35V ,and more, but you will only get a life of about 100 cycles ... the cell will hold more energy ( about 112% compared to 4.2) ...
So it's all a trade off , I run a power wall , very rarely charge over 4V per cell to get long life

1573613754678.pngChart from batteryunivercity for Li-po charged to different upper voltages
 
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Audioguru again

Joined Oct 21, 2019
278
Why do they always say to never leave a Lithium battery charging without your attention?
Does the over-voltage increase the chance of having a short circuit inside the battery?
 

oz93666

Joined Sep 7, 2010
672
Why do they always say to never leave a Lithium battery charging without your attention?
Because instructions leaflets are written by lawyers .."Don't put batteries in fire" ...Don't eat batteries" ...they are fanatically safety conscious not wanting a law suit ... and so the myth gets started and everyone repeats it...

Does the over-voltage increase the chance of having a short circuit inside the battery?
I'm not sure there's any research data on that ... Old cells when they finally die do self discharge (short circuit) ... it is more pronounced at higher voltage ... this is not a problem ... My powerwall is made from 18650's salvaged from scrap lap top batteries , occasionally one cell dies and partially shorts ( they are wired in packs of 100 in parallel) if the voltage of one pack is lower than the other packs I feel all the cells in that pack , the cell which is warm is partially shorting and I remove it .
 
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Ylli

Joined Nov 13, 2015
799
LiHV batteries can go to 4.35 volts, but regular Li-ion have an max of 4.30 volts. 4.20 is usually recommended to add a safety margain. Yes, if overcharged they can fail catastrophically.
 

oz93666

Joined Sep 7, 2010
672
LiHV batteries can go to 4.35 volts, but regular Li-ion have an max of 4.30 volts. 4.20 is usually recommended to add a safety margain. Yes, if overcharged they can fail catastrophically.
I pretty much agree with that , although I have taken standard 18650's to over 4.35 and they still work ... extreme overcharging can cause catastrophic failure(death of the cell) , but never with flames .... many people have tried to get flames this way , but always you need a big hammer and nail , and even then you don't get flames every time.

It should be said chargers and charging circuits designed for li-po always automatically stop charging at the right time , so there is never a danger from "leaving them charging without attention " as audiogurue brought up.
 
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Electronic circuits, especially if they are designed and made "over there", fail soon. Then an overcharging lithium battery becomes a spectacle. Many Lithium batteries designed and made "over there" also fail soon.
Here is what is inside an 18650 cell designed and made "over there":
 

oz93666

Joined Sep 7, 2010
672
Here is what is inside an 18650 cell designed and made "over there":
Brilliant !! ... I don't think it was flower inside that cell, it would be very fine sand to make the weight appear right , flower is too light ...
Any bad cells bought from ebay you just leave negative feedback , the seller will contact you quick , tell him you will remove the feedback after you receive a full refund , they never ask for return of item ...
But it's not just eBay these fake cells are sold .. you have to buy Panasonic or Sony to trust the capacity ... If you want to buy large amounts Queen Batteries is a good supplier of non branded cells , someone on YouTube checks the capacity and they seem good.
 
I use Li-PO batteries in my radio controlled model airplanes because Lithium is a very light weight metal, like titanium, magnesium and a few other *iums. Also, the Li-PO batteries do not have the heavy steel case of an 18650 cell.
I guess the Chinese battery had rice flour in it to make it weigh almost the same as a real 18650 battery.
 
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