Sofirn Q8 group buy (gb closed, but try PM to Sofirn for discount)

Mixing cells is dangerous. Putting four different cells in, especially at different voltages, can easily cause problems. They will equalize their charge as quickly as the cells can manage, with some cells basically charging others at a rate far higher than they are intended to be charged. This can melt the springs or damage the batteries or make it overheat.

Get four identical cells and treat them as a set, like they’re a single unit. Married, basically. They charge together and discharge together and always go in the same light at the same time.

Hi TK... we are up late! They were all at 4.2V when I started but I'll definitely have a matched set, soon. I should be putting in an order with Mountain Electronics soon! Thank you!

She doesn’t mean just the voltage. The cells have different characteristics and resistance so while you run the light the “worst” cell will be over stressed trying to balance out to the rest of them. In the meantime, just run the 2x 35E’s (and leave 2 slots open) and you shouldn’t even notice an output difference.

Actually, running different cells in parallel is pretty safe (if all start at the same voltage). If you run a strong battery like a 30Q and an old laptop pull 2000mah, they will work together. Under load the 30Q will draw more power to compensate for the weaker battery, but their voltages will always be the same. There is no chance of one battery voltage getting too low.

It’s when the batteries are in series that you need a matched and married set.

Still, it is a good idea to run 4 of the same batteries.

+1 …. BROODMASTER…… Great advice from TK & contactcr, I hope you heed it. :+1:

Your ’playing with fire’ doing it how you mentioned you were. :open_mouth:

TLDR: If you want to put in cells in parallel, always check their voltages/SOC.

No, it was fine. They were all fully charged and at 4.2 volt.

People mix all different battery sizes in parallel setups.

It’s in series that you need all them to be identical.

Like with the BLF GT. You can put 4 identical 3500mah in one carrier and 4 identical 2000mah in the other carrier. This will work fine as the carriers are in parallel.

The 4 battaries in each carrier are in series, so those 4 need to be identical and matched up.

When batteries are in series the voltages can vary and the low voltage protection only sees the total voltage. So you could have 3 cells at 3.2v and one at 2.4v and the lvp would see 3v total and think it’s fine, but really one battery has gone much too low. This can ruin that battery and make it dangerous to continue using.

Nope, the strongest cell will be stressed the most, not the weakest.

Ok…… but ’I’ am still not gonna do it. :wink:

I’m with teacher, won’t catch me mixing cells like that.

I got my Sofirn Q8 today from Amazon. Charged up 4 30Q cells with a solder blob on the otherwise flat top, straight away right out of the box it makes 5775.3 lumens.

Do solder blobs perform much better than button tops or is it negligible? 30Q’s and the 10A Panasonic/Sanyo are easy to find in BT but seems like almost nothing else is readily available.

I just charged four new 30Q button tops to 4.1V and they ended up from 4.080 to 4.091V. Is the spread in voltage safe enough to use in parallel in my Q8?

Yes, it’s safe

Is there some type of maximum difference in voltage before batteries should be charged again until they are closer before using in parallel?

That is remarkable, I’m getting 5780 with brass screws and 18awg spring bypass’s VTC5A’s 4,21v off the charger….the bypass’s only netted me 3-400lm more, so the springs are not so bad. The three times I did this all the batteries were drained to the exact same voltage, so I know the raised flat tops are all making full contact.

Stock, out of the box, it made 5775.3 lumens on the 30Qs fresh off the charger.
With brass M3 screws it made 5909.85 lumens on the 30Q’s fresh off the charger. A 134.55 lumens gain.
With Blue’s springs it made 6020.25 lumens on the 30Q’s fresh off the charger. A 110.4 lumens gain.
With 20ga spring bypasses it makes 6330.75 lumens with the 30Q’s, again, fresh off the charger. A 310.5 lumens gain for an overall increase of 555.45 lumens since I took it out of the box just after lunch.

Edit: At this point, I haven’t opend the bezel end nor have I touched the screws holding the driver in.

I already noticed that the XPL-Hi leds performed a bit better that they should in a completely unaltered Q8, so the difference may indeed be better conducting springs.

That’s really close. 11 hundredths thousandths. It’s when you have a bigger gap that you get a bigger transfer of energy. So 1 tenth of a volt will probably transfer a lot of energy really quickly. Your 11 hundredths thousandths only transfers a little energy. Not enough to hurt anything. I’m not really sure how big a difference is okay and what’s not. I’ve heard of battery chargers deviating 4 or 5 hundredths. So 1 hundredth can’t be that bad.

Does anyone have any first hand experience with this? How much is too much difference?

I think DB’s light box might read higher than yours. So it may not be a direct comparison.