Any experience with TrustFire Rechargeable 3.7V "5000mAh" 26650 Li-ion Batteries ???

[sMirko]

Any experience with TrustFire Rechargeable 3.7V "5000mAh" 26650 Li-ion Batteries ???

I want to put together a P7 led direct driven with TrustFire Rechargeable 3.7V "5000mAh" 26650 Li-ion Batteries, is it good idea?

Links removed.

 

[seven11]

Re: Any experience with TrustFire Rechargeable 3.7V "5000mAh" 26650 Li-ion Batteries

I've never used the "Trustfire" brand of 26650, but I have used the 4sevens brand with 4000mAh. The 5000mAh claim in a 26650 battery is likely inflated. The P7's forward voltage would work with a single 26650, but the datasheet specifies 2.8A to the LED. Running it direct drive at 4 or 5 amps might be too much for the LED without a driver. However, there are 26650 cells out there with 3400mAh which would work in your desired setup.

 

[sMirko]

Re: Any experience with TrustFire Rechargeable 3.7V "5000mAh" 26650 Li-ion Batteries

Seven11 Thank you for answer!

I alredy own lamp with 18650 battery and P7 led without driver. Battery is xxxxxFIRE and current is 2,5 A.
I need lamp for sperfishing, not at night and not with scuba diving, just exploring kaves, in fact I need just half minute full power light.

 

[hellokitty[hk]]

Re: Any experience with TrustFire Rechargeable 3.7V "5000mAh" 26650 Li-ion Batteries

However, there are 26650 cells out there with 3400mAh which would work in your desired setup.

How does using a lower capacity battery help...?

IMO just use an AMC 7135 and a quality 26650.

 

[seven11]

Re: Any experience with TrustFire Rechargeable 3.7V "5000mAh" 26650 Li-ion Batteries

In the OP's case he was wanting a direct drive setup, so a battery with a capacity nearer 2.5A would keep the LED from frying as quickly.

 

[hellokitty[hk]]

Re: Any experience with TrustFire Rechargeable 3.7V "5000mAh" 26650 Li-ion Batteries

In the OP's case he was wanting a direct drive setup, so a battery with a capacity nearer 2.5A would keep the LED from frying as quickly.

How does lowering the capacity lower the current draw? More voltage sag?

 

[sMirko]

Re: Any experience with TrustFire Rechargeable 3.7V "5000mAh" 26650 Li-ion Batteries

Current in the circuit is limited by internal resistence of battery plus resistence of led, 18650 batteries can have capacity of 1600mA/h and can give maximal current of 10A. Another teorethical situation is that capacity can be 3000mA/h and maximal current of 1A. What battery is better? Dipend of real needs in the particular situation.

 

[simplec6]

Re: Any experience with TrustFire Rechargeable 3.7V "5000mAh" 26650 Li-ion Batteries

In the OP's case he was wanting a direct drive setup, so a battery with a capacity nearer 2.5A would keep the LED from frying as quickly.

Capacity near 2.5A? Do you mean 2500maH (2.5aH) capacity?

Does capacity actually have a direct effect on the amount of current that will be discharged in a Direct Drive application?

 

[hellokitty[hk]]

Re: Any experience with TrustFire Rechargeable 3.7V "5000mAh" 26650 Li-ion Batteries

Capacity near 2.5A? Do you mean 2500maH (2.5aH) capacity?

Does capacity actually have a direct effect on the amount of current that will be discharged in a Direct Drive application?

No don't think so, though given the same current, different capacity will change how much you're pulling in terms of the capacity (C).

 

[seven11]

Re: Any experience with TrustFire Rechargeable 3.7V "5000mAh" 26650 Li-ion Batteries

Capacity near 2.5A? Do you mean 2500maH (2.5aH) capacity?

Does capacity actually have a direct effect on the amount of current that will be discharged in a Direct Drive application?

2500mAh (milliamps) is the same as 2.5A (amps). You are correct to question the current in this DD application. For some reason in my second post I must've thought he was overdriving the LED which isn't indicated.😳 Although, if you fully charge a 26650 it will read 4.2 volts off the charger. If the LED was being substantially overdriven, then it could potentially draw more than 2.8A (though unlikely from a single cell) and fry the LED, but in this case the LED is only being overdriven at most by .6 volts.

 

[Epsilon]

Re: Any experience with TrustFire Rechargeable 3.7V "5000mAh" 26650 Li-ion Batteries

2500mAh (milliamps) is the same as 2.5A (amps). You are correct to question the current in this DD application. For some reason in my second post I must've thought he was overdriving the LED which isn't indicated.😳 Although, if you fully charge a 26650 it will read 4.2 volts off the charger. If the LED was being substantially overdriven, then it could potentially draw more than 2.8A (though unlikely from a single cell) and fry the LED, but in this case the LED is only being overdriven at most by .6 volts.

No it's not the same. 2.5A = 2500mA, which are the units for current. 2.5Ah = 2500mAh, which is three unit for capacity. Please keep these two clear from each other 🙂.

Overdriving by '0.6 v' doesn't say anything, because leds are current driven. 0.6v on 2v will not result in a high current. On 3.3v however, 0.6v will kill the led due to exponential growth of the current. A single IMR cell can easily kill an XM-L in direct drive, due to the low voltage drop.

 

[simplec6]

How do we figure out how much an LED will pull current wise on different battery configurations? For example, running an XML direct drive on one 18650 or one 26650 or one 32650 is ok right? But then if we do an IMR chemistry battery of any size the current will be too high for an XML to handle right? Because of the lower internal resistance?

So how do we calculate what would happen if we direct drive an XML in a 2 serial setup such as two 18650s in series for a voltage of 8.4V?

I'm guessing it's different for each type of LED depending on what the forward voltage of the particular LED is right?

 

[Epsilon]

Re: Any experience with TrustFire Rechargeable 3.7V "5000mAh" 26650 Li-ion Batteries

You are correct sir 🙂.

Basically, what you need are these things:

- How hard would you like to run your XM-L? I'm guessing around 3.0A
- What is the Vf of the XM-L at that current? (different for each led!)
- What is the V of the battery at that current?

Vf of the XM-L will be around 3.5v
Now, allmost every battery large enough can easily deliver 3.0A @ 3.5v, so the voltage will be higher and thus the delivered current, which will result in one of these two outcomes:
- It will settle at an equilibrium, with the Vf of the led is the same as the battery.
- It will kill the LED, due to excessive current and thermal runaway (the led's Vf drops when they get warmer!).

The most fail-safe way of powering an XM-L, is using a 7135 based driver (8x for 2.8A). This will limit the current. You can use a 4.2v battery on a 3.3v led without any problem.

 

[hellokitty[hk]]

Re: Any experience with TrustFire Rechargeable 3.7V "5000mAh" 26650 Li-ion Batteries

The most fail-safe way of powering an XM-L, is using a 7135 based driver (8x for 2.8A). This will limit the current. You can use a 4.2v battery on a 3.3v led without any problem.

Right IMO a 7135 based driver is what you'd want to use in this application (along with good cells).

2500mAh (milliamps) is the same as 2.5A (amps).

And no that is not true.