Lithium ion battery’s not living up to its Ah

Thread Starter

No one of consequence

Joined Jan 3, 2023
7
We are looking for lithium ion batteries that live up to the ah listed. We have tried many that say around 3400 mah. The load has a draw of .5-.7 amps and only get one hour out of them when we should be getting closer to 5 h. How do I find a quality battery that does what it says? We have found only one that lives up to its rating but it is only 12v we need a 14.8v.
 

Papabravo

Joined Feb 24, 2006
21,313
Besides the capacity there are different charge and discharge rates. Do you know what those rates are? How you do the measurement has a huge effect on the results. this is typical of most if not all nonlinear systems.
 

Thread Starter

No one of consequence

Joined Jan 3, 2023
7
Besides the capacity there are different charge and discharge rates. Do you know what those rates are? How you do the measurement has a huge effect on the results. this is typical of most if not all nonlinear systems.
I don’t see these rates on the batteries or the product details. Maybe because I don’t recognize it or maybe because it does not say. We are getting these batteries from Amazon.
 

LowQCab

Joined Nov 6, 2012
4,302
Not all Batteries are created equal.

Very few manufacturers advertise guaranteed performance numbers.

All Li-Ion Cells loose a small percentage of their capacity with each Charge/Discharge-Cycle.
The loss of capacity per Cycle is determined by how hard You push the limits of the Cell in both
maximum-Charge-Voltage,
permitted minimum Discharge-Voltage,
and permitted maximum-Discharge-Current,
and the amount of time spent in Storage at a Voltage that is substantially below the "Nominal-Voltage".

Sometimes You get what You pay for.
Order from a reputable Commercial-Electronics-Distributor.

This outfit will make You a top-notch Custom Li-Po Battery.
https://maxamps.com/
Made in the USA
.
.
.
 

Thread Starter

No one of consequence

Joined Jan 3, 2023
7
Not all Batteries are created equal.

Very few manufacturers advertise guaranteed performance numbers.

All Li-Ion Cells loose a small percentage of their capacity with each Charge/Discharge-Cycle.
The loss of capacity per Cycle is determined by how hard You push the limits of the Cell in both
maximum-Charge-Voltage,
permitted minimum Discharge-Voltage,
and permitted maximum-Discharge-Current,
and the amount of time spent in Storage at a Voltage that is substantially below the "Nominal-Voltage".

Sometimes You get what You pay for.
Order from a reputable Commercial-Electronics-Distributor.

This outfit will make You a top-notch Custom Li-Po Battery.
https://maxamps.com/
Made in the USA
.
.
.
Thank you. That helps a lot.
 

Audioguru again

Joined Oct 21, 2019
6,783
You said you need a 14.8V Li-Ion battery. Then you are looking for a 4-cells battery that is at its half-discharged storage and selling voltage (3.7V for each cell) but you are testing it at 12V to 13V when it is dead and is not charged. Since it is half discharged or dead then its capacity is very low.
It is 4 x 4.2V= 16.8V when fully charged and has been charging at 16.8V until its charging current has dropped to a low current.
When it has discharged to 12V (3V per cell) or 13V (3.25V per cell) then its load should be disconnected and it should be charged.

Amazon and many online stores know nothing about batteries and sell no-name-brand poor quality ones.
Here is a Li-ion battery from ebay that has not much battery chemicals in it:
 

dl324

Joined Mar 30, 2015
17,142
We have tried many that say around 3400 mah. The load has a draw of .5-.7 amps and only get one hour out of them when we should be getting closer to 5 h. How do I find a quality battery that does what it says?
Where are you buying the batteries from? Are they known, reputable brands? What form factor are the batteries?

I bought some 9V Li-ion batteries in PP3 form factor. They said they were 12800mAh. It was the first time I purchased that type of battery (internal voltage regulator) and it was an impulse buy. After buying them, from AliExpress, I found that the actual capacity was closer to 250-300mAh. If I had engaged my brain before I made that impulse purchase, I would have known that that capacity was not credible (600-1000mAh is more likely). I bought 8 of them and it took me 2-3 weeks to get my money back. The seller was clueless and kept telling me to charge the batteries before using them - which anyone doing a capacity test would do (unless they were an idiot).
We have found only one that lives up to its rating but it is only 12v we need a 14.8v.
What is your voltage tolerance? Are you willing to use something like 18650's in series? A reputable 18650 would give you about 3-4Ah the last time I checked.
 

MrAl

Joined Jun 17, 2014
11,723
Most batteries have published ratings based on a discharge rate of C/20.
That means that a 2000mAhr cell would be tested at a discharge rate of 2000/20=100ma but no higher.

That said, 1hr for a 3500mAhr battery still doesn't sound right, but testing at 175ma would reveal the actual capacity as normally tested.
 
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