mixing 18650 brands in a single charger

js-lots

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I am new to this forums and learning alot about led flashlights. I love them. I have a couple questions. Is it ok to mix different brand 18650's in the same charger. For example tenergy and surefire in an ultrafire wf-139 charger? Is it safe to take those same two batteries and use them in a flashlight designed for 2x18650 or should I use the same brand batteries? Anyone's help would be wonderful. :)

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mte ssc-p7/ streamlight stinger/ tiablo a9/ aurora mc-e/
 
I am new to this forums and learning alot about led flashlights. I love them. I have a couple questions. Is it ok to mix different brand 18650's in the same charger. For example tenergy and surefire in an ultrafire wf-139 charger? Is it safe to take those same two batteries and use them in a flashlight designed for 2x18650 or should I use the same brand batteries? Anyone's help would be wonderful. :)

Thanks for your questions, and welcome to CPF! There are several concerns in your post.
1) If a charger has separate independently terminating charging bay slots, and you use protected cells then it should be fine to use different types of Li-Ion in charging. If you are using unprotected cells, take the time to learn the pro's and con's about them.

2) I would never recommend using different cell types or states of charge in the same light. This is more of a danger with primary Lithium cells, than secondary (rechargeable) Li-Ions. It's best if they are within 0.05V of each other...i.e. 4.12V & 4.17V for Li-Ions.

3) I don't believe Surefire makes a rechargeable or 18650 size Lithium cell. Their 123a primary cells should never be recharged.

(This is yet another reason there should be a sticky in this section about Lithium cells)
 
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Thanks for your questions, and welcome to CPF! There are several concerns in your post.
1) If a charger has separate independently terminating charging bay slots, and you use protected cells then it should be fine to use different types of Li-Ion in charging. If you are using unprotected cells, take the time to learn the pro's and con's about them.

2) I would never recommend using different cell types or states of charge in the same light. This is more of a danger with primary Lithium cells, than secondary (rechargeable0 Li-Ions. It's best if they are within 0.05V of each other...i.e. 4.12V & 4.17V for Li-Ions.

3) I don't believe Surefire makes a rechargeable or 18650 size Lithium cell. Their 123a primary cells should never be recharged.

(This is yet another reason there should be a sticky in this section about Lithium cells)

thankyou for your response. as far as the 18650's I meant trustfire. sorry about the confusion. On the charger, I am able to charge one battery at a time. Based on your response you would recommend having two freshly charged 18650's placed in a 2x 18650 flashlight? I will also be sure to use the same brand batteries as this seems the safest. I have read about all the dangers of 18650's and I never leave them unattended while charging. Additionally they are stored in a seperate container. I will be sure the batteries have near the same volt reading. All my 18650 cells are protected tenergy and trustfire. Thanks for your help
 
thankyou for your response. as far as the 18650's I meant trustfire. sorry about the confusion. On the charger, I am able to charge one battery at a time. Based on your response you would recommend having two freshly charged 18650's placed in a 2x 18650 flashlight? I will also be sure to use the same brand batteries as this seems the safest. I have read about all the dangers of 18650's and I never leave them unattended while charging. Additionally they are stored in a seperate container. I will be sure the batteries have near the same volt reading. All my 18650 cells are protected tenergy and trustfire. Thanks for your help

It sounds like you have a pretty good understanding of the proper use of Li-Ion's. Using two freshly charged cells in a 2x18650 light is sort of a "poor man's" version of a more expensive "balance charger" setup...the idea being that the full charge gives both cells a similar maximum voltage that in effect has them be balanced.

If you can get an inexpensive DMM, you can use other same brand cells that are not fully charged. For example a 4.02V with 3.98V should pose no problems. Most of the concerns with Li-Ions are during charging...and in particular with unprotected cells being charged in a charger that does not terminate charging current when the cells are full. A protected cell has high & low voltage circuit interruption, so there is very little concern with them.

I took these images to show what the protection "PCB" board actually looks like as a battery add-on (for new CPF members).
 
I recently purchased an inexpensive battery tester at home depot. (sperry bt500) The dial has settings to test lithium 3v and all the other norms. Can I get a somewhat accurate reading from this to check my 18650's or should I try something else. I don't own a volt meter or anything of the like. Price is somewhat of an issue, but then again I cant stop buying flashlights. Thanks
 
There are very cheap (under $10) DMM's like at Radio Shack/Sears. IMHO, if you are going to use Li-Ion's you really should have a DMM that gives volt readings accurate to 0.00 V level.
 
lux, you are right, I will pick one up tommorrow. I'm probably insane for not owning a dmm. I just shopped around online and saw some decent ones for 20 give or take. Thanks
 
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