18650 protection circuit

[divin'dog]

Thanks for the replies. So basically you guys are saying yes.. And no. Hahaha

Protection circuit sounds good for my use and to prevent overcharging.. I can find stuff like this but still not sure if the circuits are all the same:

2 Panasonic NCR18650B Li ion Battery 3400mAh 3 7V 18650 New Protection PCB Japan | eBay

I did a bit of research for 18650 batteries and ended up buying these: LG ICR18650E1 - 18650 - 3200mAh 4.35v

I was going to buy the Panasonic NCR18650B because it was popular but chose the LGs because they stay brighter longer but have a steep curve towards the back end as the battery is discharged. Basically comes down to useful lighting. LGs are also much cheaper. The Panasonics have a gradual sloping curve, so your light will gradually get dimmer and dimmer from the onset whereas the LGs will stay brighter longer but then falls off steeply closer to full discharge. Depends on what you prefer. Talk to the seller who owns the business. Very helpful person. He will tell you the difference so you can make an informed decision.

Protection circuit also prevents discharging beyond a certain point of ruining the battery. I chose unprotected because if I need a light in an emergency situation while diving, I'd rather ruin a battery to be able to see in the dark. They also make protected LGs.

 

[scubastingray]

Those LG batteries look pretty cool. I wonder how they would do when stacked against the 3400mah Panasonics.
Also, you could get them pretty cheap here: $17.35 Panasonic NCR18650B 18650 3.7V 3400mAH Protected Rechargeable Li-ion Batteries (2-Pack) 2-pack - button top at FastTech - Worldwide Free Shipping but they seem to be out of stock. i ordered some about a month ago and am still waiting (slowwww shipping).

 

[lemke]

Have you actually compared the burn time of the LG versus Panasonic with your torch? I'd be interested to know.

 

[divin'dog]

Have you actually compared the burn time of the LG versus Panasonic with your torch? I'd be interested to know.

Here are excerpts from email correspondence from Richard, owner of Mountain Electronics. I had asked about the Panasonic and LG differences... I also asked about chargers and ended up with an Xtar SP1. I'm happy with my choices so far. See the bolded text below. Image is the KP wrapped battery (same as Panasonic) vs the LG. I don't have a Panasonic to compare directly. Made my decision based on the graphs and Richard's advice, which is all I had to go on.

Richard later remarks on a cheap ebay light I bought... I have since bought an Archon V10 that I love.

Hope this helps.

dd

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The Panasonic 3400 is a great cell, probably the most capacity you'll find and excellent quality.


The protected versions have an extra circuit put onto the cell that protects against short circuiting, overcharge, and overdischarge (the cells will be damaged if charged all the way empty.) This might seem great, but in some lights they are too big to fit. Most of the modern lights fit them just fine, but there are a few that will not.

Also, where light is critical, the protection circuit may trip when the cells get low, cutting the light off immediately. Now, in most lights you will see the light getting very dim before this happens, but when it happens it is like a light switch turning off. This is fine for most uses, but if it's life or death you may need that extra 15 minutes of dim light to get you out of a tough situation. Yes, the cell may end up ruined, but $8 is cheap compared to having no light. So for diving, I would consider how crucial the light is. That said, most people do use protected still, but it's something to consider.

All of the Xtar chargers are great, but the Nitecore chargers are also a good value. There are two main advantages by going with the Xtar vs. the Nitecore; (1) they charge twice as fast (3400mAh cells can take a long time on a Nitecore); and (2) they give you a few extra features, such as USB output for charging your phone, etc. from 18650 cells. The VP series also gives you the voltage readout, etc., but those are the main differences. So, if you don't think you need the extra bells and whistles or speed, the Nitecore chargers are a good reliable option.

If you did end up going with the VP2, I would also think about the LG D1 or E1 cells. They are 4.35v cells which require a charger (like the VP2) that can charge them, but they have great capacity and maintain peak brightness longer as the cell discharges due to their higher initial resting voltage. They are not available in protected cells. The VP2 can charge every size and type of lithium cell I've ever seen, so it is very versatile, but it is also a bit more expensive. The VP1 is the same as the VP2 except for the 4.35v option.

Hope that helps,

Richard

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The burn time isn't longer on the LG E1 or LG D1 (vs Panasonic) but the light will stay brighter as the cell begins to drain (less voltage sag.) The burn time will still be the longest on the Panasonic 3400, but it will dim faster as the cell drains. Check out the attached graph of the Panasonic 3400 cell (KP wrapped) vs. the 3000mAh 4.35v LG D1 at 3A.


How low you can go depends a lot on the driver in your light, but most cheap lights like the one you bought (in reference to a cheap ebay light) will get very dim before damage occurs, like 5% of initial brightness before you reach 2.5v. The light will dim very fast during the last 5% or so of capacity (again, see discharge curve.)

I don't carry any diving lights, I don't dive so I'd have no way to truly test their quality and I don't like to sell stuff that I haven't personally tested.

Richard

 

[lemke]

Good to know!

 

[scubastingray]

Why did the LG start at such a higher voltage? It seems like if they started at the same voltage it would lose its edge.

Interesting to know about the chargers. I'm running a nitecore, and will likely get an Xtar for my next. They need one that is meant for 26650s primarily, as charging those in my i4 blocks 2 (you can only charge in 2 of the 4 bays).

edit: actually, 2x is a bit of an exaggeration it's 33% more output current on like the XP4c (500mah) vs the Nitecore i4 (375mah). for 4x output. 1000mah vs 750mah for 2x output. Still faster though, so I'll probably end up with one.

 

[Wolf Peng]

I agree that a lot of batteries from China with low cost are not really good; but this does not mean all batteries from China are no good, it depends if you choose the right one to work with. In China, most are the OEM manufacturer, even Panasonic, they are manufacturing in China for some products; so the big factories always focus on volume and those vendors are doing excellent on quality control; but there are many small companies that they want to survive that they always play tricks to get the cost down and put blusterous capacity information to increase their sales; the quality control is weak.

It does not matter if your battery is circuit protected or not when the light is powered by 1 single cell and the IC has shut off voltage control.Normally, the battery we buy from the market has the PCM protection to avoid over charging/discharging. If you are using multiple cells, it is better to have the matched capacity.

 

[scubastingray]

I agree that a lot of batteries from China with low cost are not really good; but this does not mean all batteries from China are no good,

No one in this thread has suggested that, given that you can't even get 26650s or 18650s from anywhere but china...

 

[miketsp]

I recently got myself a DGX 600 light from dive gear express (https://www.divegearexpress.com/lights/backuplt.shtml)

It came with an 18650 battery and I was looking for a second battery to have on hand. I located one at a local electronics place, but it was shorter and the guy said it was because it didn't have the circuit in it that the original battery has, which I suppose is the protection circuit. i'm kind of new to this so a couple questions:

1) what happens if you run the light without a circuit in the battery?

2) is this protection circuit a standard thing? as in, any battery with a protection circuit will function the same, or is this something that's been specifically tweaked by the light manufacturer to get a certain output from the battery for their light


thanks in advance!

I have some batteries (18650 and 26650) where I removed the protection circuit because I had a couple of very cheap Chinese dive lights that had leakage problems as they were first delivered and the protection circuits turned out to be the most sensitive part of the assembly - with just a few drops of water they'd burn up.
Anyway once I made some o-ring sizing adjustments and completely dismantled and rebuilt the lights with correct lubrification they never again gave me any problems.
I really don't see the removal of the protection circuit as a problem in a dive light. The leds are regulated by the control circuit anyway and I only use a regulated charger, so I actually eliminated one failure point.
In case of a complete flood, the protection circuit won't offer any protection whatsoever.

Stick with Japanese brand batteries (eg. Panasonic). Stay away from China brands or anything with "Fire" in the name.

Funny, I would have said the opposite. The best experiences I've had so far have been with the Chinese TrustFIRE line in terms of capacity and not losing charge while in storage. I've been using various of these for 3-4 years now and they've been excellent.