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Old Sep 27, 2015, 06:16 PM
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Any Experience with Lithium Manganese Batteries?

Guys,

I was browsing eBay last night and I came upon some new types of batteries. They are made by the IMREN battery company of china and are billed as LiMn, which I assume is Lithium Manganese. Some of their cells are the same size as an A123 2500 ma cell but they have a capacity as high as 5500 mah. They also seem to have high surge discharge rates - as high as 60 amps although the continuous current is less. They also are rated at 3.7 volts, rather than the 3.3 volts of an A123 LiFe cell. I asked the seller if the manufacturer has a product data sheet and here is what he sent to me:

Place of Origin: Guangdong, China (Mainland)
Brand Name: IMREN
Model Number: 26650
Type: Li-Mn,
Nominal Voltage: 3.7v
Size: 18*65mm
Nominal Capacity: 4200mAh
model: 26650
Weight: 100g
Length:: 65.79mm
Nominal Capacity:: 4200mAh
Voltage:: 3.7v
Diameter: 26.20mm
Discharge rate: 60a

The seller told me that this is all the information that the manufacturer provides. I looked at the products on the IMREN web site and did not see the 4200 and 5500 cells. None of the other cells had any more information than what is given above. So there's no info on charging - i.e., whether they should be charged with the charger set to LiPo, or what the maximum charge rate should be. Also, they said that you shouldn't "knock" the battery, which I assume means not to subject it to impact. I looked on this forum and did not find any references to IMREN or LiMn. Has anyone had any experience with this type of battery?
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Old Sep 27, 2015, 06:53 PM
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Buy a dozen and review them for us.
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Old Sep 27, 2015, 09:46 PM
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http://batteryuniversity.com/learn/a...of_lithium_ion or maybe this type of battery:
https://www.google.com/search?q=LiNi...utf-8&oe=utf-8

These batteries?
https://www.imrbatteries.com/imren-i...t-top-battery/
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Old Sep 28, 2015, 12:36 AM
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I thought standard lipos are Lithium Manganese type?
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Old Sep 28, 2015, 09:21 AM
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They are LiCobalt
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Old Sep 28, 2015, 09:28 AM
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characters welcome!
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The ones I have for AEDs are primary type therefore not rechargeable. Do they make rechargeable LiMn?

mw
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Old Sep 28, 2015, 12:27 PM
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Rechargeable - The vapo's love them it seems.
https://www.imrbatteries.com/search....ganese&Search=
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Old Dec 18, 2015, 06:26 AM
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Bought and tested some LG 3000mAh 20A.
Disappointing... don't hold even 10Amps for more than one minute, voltage drop is too big to be useful, any of our voltage monitors will beep or trigger autolanding on low batt.
The cell internal resistance is somewhere around 24mO, and this should tell that at 4A draw the voltage drop by 0.1V, but is more.
At 1C draw, i.e. 3A I was able to draw 2500mAh until the cell voltage reach 3V, indeed, they are more tolerant with low voltage, like the LiFePO4's.
But at 6A, i.e. 2C, and 3.5V alarm voltage, they deliver only 1000mAh. You should go even more down with discharge, to 2.5V, to reach the critical limit. and draw everything from them.

A more complete, technical review of the cells I tested can be found here, but the reality is not that shinning... in the review maximum current used was 2.5 Amps... not our game.

Not the last, they charge slow... about 2-4 hours.
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Old Dec 18, 2015, 08:15 AM
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Quote:
Originally Posted by renatoa View Post
Bought and tested some LG 3000mAh 20A.
Disappointing... don't hold even 10Amps for more than one minute, voltage drop is too big to be useful, any of our voltage monitors will beep or trigger autolanding on low batt.
The cell internal resistance is somewhere around 24mO, and this should tell that at 4A draw the voltage drop by 0.1V, but is more.
At 1C draw, i.e. 3A I was able to draw 2500mAh until the cell voltage reach 3V, indeed, they are more tolerant with low voltage, like the LiFePO4's.
But at 6A, i.e. 2C, and 3.5V alarm voltage, they deliver only 1000mAh. You should go even more down with discharge, to 2.5V, to reach the critical limit. and draw everything from them.

A more complete, technical review of the cells I tested can be found here, but the reality is not that shinning... in the review maximum current used was 2.5 Amps... not our game.

Not the last, they charge slow... about 2-4 hours.
As you have noticed, you have to go to a lower voltage to use these cells properly. Triggering voltage monitors and failsafes is not the cell's fault, it's the user's fault for not properly configuring his equipment for use with a particular battery.

There are 18650 cells that will do 10A with pretty high capacity, and some even 20A, but with less capacity. See this site for lots of actual discharge curves of many quality cells.
http://lygte-info.dk/review/batterie...comparator.php
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Old Dec 18, 2015, 09:11 AM
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With such high internal resistance, the voltage swing is too high to compensate this big voltage drop.
And definitely 20Amps is not a discharge rate to use these cells in real life, but is actually rather a short circuit current for these cells... if you draw 20Amps from a fresh charged cell, the voltage drops at 2.5V in some seconds, how deep should go with discharge further ?
Thus, the claimed 14C rating is a joke, discharging at 14C means a sustained discharge at nominal voltage for about 4 minutes, far from these cells capabilities.
I am curious to hear what could be someone positive experience with these cells, other than TxRx packs.
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Old Dec 19, 2015, 11:25 AM
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Quote:
Originally Posted by renatoa View Post
With such high internal resistance, the voltage swing is too high to compensate this big voltage drop.
And definitely 20Amps is not a discharge rate to use these cells in real life, but is actually rather a short circuit current for these cells... if you draw 20Amps from a fresh charged cell, the voltage drops at 2.5V in some seconds, how deep should go with discharge further ?
Thus, the claimed 14C rating is a joke, discharging at 14C means a sustained discharge at nominal voltage for about 4 minutes, far from these cells capabilities.
I am curious to hear what could be someone positive experience with these cells, other than TxRx packs.
Here are some high current discharge tests of the HG2 cell. It seems to hold an acceptable voltage at 10A, but its capacity is ~2800mAh. From the tests in this link, the energy density is ~211Wh/kg at 10A, and ~218Wh/kg at 5A. Maybe your cell was old.
https://www.e-cigarette-forum.com/fo...esults.680796/
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Old Dec 19, 2015, 01:51 PM
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Old cell, when they are on market since this spring ?

Even accepting these tests, 2800 mAh @ 10A is only for discharging down to 2.8V, which actually make a 4s pack behave as a Lipo 3s pack, when you count the power delivered.
And we know that the power make things not drop from the sky, actually... not the mAh.
So if you do the math again for the Wh effective delivered for the weight, you end close to a 10C Lipo.
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Old Dec 19, 2015, 02:43 PM
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Originally Posted by renatoa View Post
Old cell, when they are on market since this spring ?

Even accepting these tests, 2800 mAh @ 10A is only for discharging down to 2.8V, which actually make a 4s pack behave as a Lipo 3s pack, when you count the power delivered.
And we know that the power make things not drop from the sky, actually... not the mAh.
So if you do the math again for the Wh effective delivered for the weight, you end close to a 10C Lipo.
The energy density is the important value. What is "wh effective"?
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Old Dec 19, 2015, 05:30 PM
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Originally Posted by renatoa View Post
Old cell, when they are on market since this spring ?

Even accepting these tests, 2800 mAh @ 10A is only for discharging down to 2.8V, which actually make a 4s pack behave as a Lipo 3s pack, when you count the power delivered.
And we know that the power make things not drop from the sky, actually... not the mAh.
So if you do the math again for the Wh effective delivered for the weight, you end close to a 10C Lipo.
The energy density I estimated takes the voltage drop into account. I multiplied the capacity by the average voltage during the discharge, estimated from the discharge curve.
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