Sofirn SP70 Alone $50, PM for AMZ US CODE(LIMITED)

I now like my Sofirn SP70 more than ever. What happened was I noticed a voltage inequality between the 2 EBL 26650 cells after using to where they needed recharge. I correctly attributed this to the lack of good contact between cells, due to Flat tops. I drove to Home Depot and purchased a pack of Neodymium Disc Magnets (pictured). The foam adhesive removed easily, and the bare magnet fit the Flat top well. Now I can feel both cells are equally drained and the runtime has dramatically and to my great delight increased as one expects and hopes of 2x26650 5000 mAh rechargeable lithium ion batteries. Perfection achieved on a strict budget!

Of course, you do have all the safety and performance issues that comes with using magnets. This is why they are not recommended.

Sofirn, please update the price in the title of this thread.

With code, the SP70 alone is $51.99 on Amazon US… not $50.

Thanks.

Check your tail cap and bezel.

My two were received with dented tail caps and one dent in the bezel. Two separate parcels as well. Seems Sofirn need to add more protection.

Wow big, hefty light. Just what I was looking for - but won’t turn on. DOA it seems. Green Shockli 26650s worked just fine in D4S. Topped them off to 4.2 last night. Connections cleaned, head and tail as tight as I can get them. Bummer.

First light I have gotten where it won’t turn on right out of the box (well, after the cells are in anyhow).

Guess I will be pushing back to Amazon in the morning.

I think the magnet material itself is not a good electrical conductor and most of the current might be passing through the thin plating on the surface of each magnet (probably nickel plating). For flat top batteries I would cut a small round piece of copper (copper plate 2mm thick from Lowes) and solder it on top.

Sorry to hear about the DOA. Did the green LED light up the side switch? I assume the connection between each battery in series is good. If you have a few 18650 button top batteries, maybe you can use the plastic tube adapters and try those batteries?

No green. Tried 18650s - also no luck. :frowning:

So your batteries do make contact from head to tail?

You might try loading the batteries, but leave the tail cap off then run a jumper wire from battery negative to the battery tube. This bypasses the tail switch.

You also might try removing the battery tube from the head and make sure there is no glue on top of the driver. The battery tube has to screw down and press on the drivers outer ring. I had a little glue on mine, but not enough to prevent a connection. If they added a bit too much glue it could harden on the driver ring and prevent the battery tube from screwing all the way down and making good contact.

Also make sure the tail cap retaining ring is tight.

Yep cncyana and Jason your suspicion was warranted. I found a pair of protected button-top 18650’s, adding about 6 mm total length and, BINGO, let there be light. I then remembered I had a faulty Folomov travel charger with the magnets (would charge batteries but didn’t work in reverse to charge a device), so I scavanged one of the magnets as a spacer between the too-short, flat-top, 26650s and things work fine now.

All modes and turbo seem to be working fine. Will now check and make sure batteries discharge evenly. If not, I guess maybe I will solder a blob on them.

Boy I like the light. It is a tank. I have lot’s of lights but not a single “thwacker” until now.

Thanks guys.

Now I know what to do if mine looks DOA. Thanks for the info!

Sofirn 26650 HD 25A review

Official specs

Capacity: 5000mAh (min 4900mAh)
Continuous discharge current: 25A

My tests

Capacity: 4600mAh

They perform as good as a Samsung INR18650-30Q up to 10A.

Below graph is measured with my computerized Battery Analyzer at 5A, 10A, 15A & 20A

Your graph is not showing temperatures at all.

If it completed the 20A test without exceeding it’s max safe temperature (typically 80°C) then doesn’t that mean it’s rated for at least 20A?

I’m still learning when it comes to the max discharge curve. Does it always have to reach 80 degrees to show a max rating?. I’ve seen tests from HKJ that have bad discharge curves which haven’t reached 80 degrees and they’re too high.

I’ve tested 14500 cells and the curves and capacity at that current look terrible without 80 degrees being reached.

EDIT: If I’m wrong them I’ll alter my first comment

I edited my first comment. Everyone can make up their own mind as to whether the 20A is acceptable :slight_smile:

No. Magnets having poor resistance is a myth. The material has poor resistance but large diameter and short length means the total resistance is negligible.

This magnet is a 1.53 mm long AWG –1 (yes, negative) solid NdFeB core wire. Despite poor material this conductor has a resistance of about 32 µΩ. This means that with a light pulling 10A the voltage drop is ~0.00032V.

Note that the number doesn’t include contact resistance which is likely higher than that (I would love someone more knowledgable to chime in).

In this case: the adhesive layer is likely an insulator which breaks connection.

Try using the magnet on a cell in a battery charger that measures the internal resistance. You will see a big increase. I’m not sure if this directly effects the performance on a FET driver, I haven’t tried to measure the amp draw difference, but I assume it would.

That, plus the potential to move around if dropped and cause a short makes me not want to ever use them. I’ll just solder blob a cell or get button tops or solder on a button top.

20A at 64 degrees
25A at 70

Even though it didn’t hit the 80 degrees temp I don’t think it’s handling the 25A current well at all.

Keep in mind that my CBA has a voltage drop of 0.03V at 20A & 0.04V at 25A so it’s not spot on but works well enough to show performance

There is more of this battery conversation here if anyone is interested.

Subbing.