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Discussion Starter · #1 · (Edited)
Review: New "Solarstorm" 2S2P 8.4V "water resistant" 4 x 18650 battery case for bicyc

Finaly manufacturer of an old 2S2P battery case made a new improved one. The old one has virtualy gone out of stock at any known seller. I've got cases from two sources (Gearbest and Kaidomain) to see if there is any variance in the production. The case is mostly used to power bicycle lights with 4 Li-ion 18650 cells of your choice. Cells are set in a 2S2P configuration which gives double capacity and 8.4V or can be used in 2S1P configuration.

The information about it has been already published in the thread here but I would like to make it in one place since I've done some important measurments.

Pictures of the case:







Electrical description:



There is an arror in description under nr. 6 - it should write: "USB maximum current ...... 2000mA"

The cells has to be inserted differently than with old case. It is marked in the case but I would advise you should mark it also on the cover near the springs so you can check again when you are closing the case. The cover is rectangular so it can't be placed in wrong direction. Cells are placed diagonaly so the cover can be inserted in any of two directions.



In the bottom of the case there are two connectors to connect cells in series.



What I don't like is that the all four are not cross connected like in the old case. That way electricaly looks like we would have two 8.4V cells in parallel. If they would be cross connected we would have like one big cell same as almost all welded 2S2P battery packs. What I'm also missing is the connection from the bottom to the protection circuit in order to check the voltage of each cell in series.

Protection Circuit

Big improvement in this new case is the protection circuit. I've made few measurments on different features.

Overcharging cut off kicks in somewhere at 8.46V in both cases. So if the charger fails to stop charging protection circuit would cut it off. Big and the most important improvement over the old case. Next feature is overdischarge protection. There I've got mixed result depending on the case and the current. It was funny when running at low current ovedischarge protection kicked in quite late, to late for my opinion. I've got 4.60V at virtual no load (0.02A just light connected), but 5.05V at 2.4A load (regulated single XM-L driver). So the cut off would depend on the load and the light you are using. To me this is not that important as I've found 4 different 2 led lights starts dimming much before and you'll notice low voltage anyway. Underdischarge protection restores at 6.0V at both samples if the cells can regenerate to that extend.

There are three status lights which shows the status (ie. voltage) of the pack when you push on the On/Off switch near to them.

Frame sourceGearbestKaidomain
3 status leds8.4V8.4V
2 status leds7.45V7.60V
1 status led6.95V7.10V
1 status led flashing6.45V6.60V

So the difference is constant 0.15V - not that much and probably due to resistors tolerance on the PCB. Showing status leds takes the 0.5mA current out of the batteries.




Standby current

Or in another words self discharging. By description it should be 10 microA. No way near the truth or it is just a mistake in the description: micro instead of mili. I've got 8.6mA with the Gearbest sample and 8.5mA with the Kaidomain sample. This can be of concern if you are leaving the pack uncharged for longer period. If we take the lowest 18650 cells capacity of 2200mAh we would use nowadays (ie. 4400mAh for the pack) it woud get drained in a 4400/8.5 = 518h or 21 days. This is bad news so be aware and take the cells out of the box when not used or recharged for more than 3 weeks or with higher capacities for a month.

Latest test shows this parasitic drain stays active all the time even when the cells drain below overdischarge point. This is dissapointing to me. Yet I can recall the similar issue with Magicshine ALU pack with led display showing the status. They might clone their circuit, though :(

USB Output

Some would find it usable and some not. For the ones who would like to connet GPS/Phone in paralell to the light this would be usable. For the others this might be just unneded appendix. Anyway I've measure output voltage and got it 5.02V. It could charged my phone so it delivers at least 1A.

Pros:

  • protection circuit with overcharge and overdischarge protection
  • showing the stage of the pack
  • smaller and lighter than before
  • wide strap to fasten it to the bicycle frame
  • USB output (for some people only)
  • interchangable battery cells
  • cells can be charged outside of the case - balancing possibilities

Cons:

  • no cross connections in the bottom of the case
  • no connection from the bottom to the PCB
  • only Solarstorm type of connector (compatible somewhat with Magicshine, though)
  • no or bad water resistance (would need bit thicker o-ring)
  • no watter tight cover for USB connector
  • high standby current of 8.5mA




Overall impression


It is nice case and unfortunately the only one of that type I know. This version is more usable than previos one and much more safe to use, just like welded battery packs we are mostly see in the bicycle light sets. To bad it doesn't have cross connections at the bottom and wire to the PCB. In this regard welded battery packs are still better. On the other hand you can charge cells individualy from time to time to get balanced, but you need additional individual (multibay) charger. To bad the case is not very water resistant. Using some silicone grease would help to solve that somewhat. Big issue that I see now is high standby current of 8.5mA. Be aware and take cells out of the case when not used for a longer period ie. more than 3-4 weeks.

To test in the future:
Would need to test also short protection and overcurrent protection. Actualy I would leave short test as a last thing to do and I don't have any high current drain device prepared right now. Would need to think of something....

Max. USB current is also to be tested in the future.




EDIT:

Protection circuit pictures








Any comments and suggestions to enhance the review are welcome.
 

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Good review, thanks for this.
What kind of batteries do you recommend?
With or without protection?
 

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Nice review. Two questions:
Does using a box have an effect on runtimes? In other words given the same cells would output and runtime be similar to that of a welded pack?

Understanding batteries can be charged in the box, would it be better especially long term to use a seperate smart charger, given that a Magicshine charger or Glowworm from Action led is just a few bucks less than a 4 bay smart charger. With Lipo's I'm always cautious
 

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Understanding batteries can be charged in the box, would it be better especially long term to use a seperate smart charger, given that a Magicshine charger or Glowworm from Action led is just a few bucks less than a 4 bay smart charger. With Lipo's I'm always cautious
As pointed out, this battery case doesn't have wiring coming from the middle (bottom contacts), so it is not able to monitor the balance of the cells while they are being charged. This is potentially dangerous, especially with unprotected cells, if one cell of either of the 2S pairs starts off at a lower voltage the other cell could easily get overcharged before the total voltage of the pair hits 8.4v.

In my opinion it is definitely safer to use a good quality 4 bay smart charger (and good quality cells like NCR18650). I'm currently using NiteCore D4 to charge the batteries used in these battery boxes.
 

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Do any of our standard welded packs have that extra connection between the and the bottom of the pack that you list as a negative here? Am I correct in assuming that's for balancing?

I don't know what I'm talking about electrically, but could the cross connection between the two sides of the pack be done via a trace on the PCB? If so, is it?

Is the voltage regulation for the USB port implemented on the board (ie four wires to the board), or is it done at the USB connector? I suppose it could also be implemented at the Y in the cable.

PS: The pictures don't seem to be working. May I suggest uploading them to MTBR, rather than using external links.
 

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What's the function of the on/off switch for?
My light works in both settings!
 

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Discussion Starter · #8 ·
Good review, thanks for this.
What kind of batteries do you recommend?
With or without protection?
I would recommend unprotected but well known brand cells like Panasonic, Sanyo, Samsung, LG, Sony. This would be also partialy answer to the others too.
Let me explain how I would (and will) use that pack. I'm going to use one of the brands above and charge them with 8.4V charger as I usualy do with all other packs. Since I allways check each charger behaviour when I get one I would know it should charge correctly and the protecton circuit in the pack is adding to safety. Mind you the previos version didn't have any overcharging protection leaving you solely on the charger safety. From time to time I'm going to take the cells out and charge them individualy in my 2 bay shargers (I'm using Nitecore i2, Basen, Xtar) so all cells would be charged full and balanced that way. Of course prior that I'll measure the voltage of each cell to see how they differ and mix cells in the best way to achive even discharge.
Probably most of users won't do it the way I do, but this is the most safe way retainig practical usage (not opening the case each time and charge them outside). Since I know the cells very well I'm pretty shure how they would behave. I've measured near 100 cells so far and I know how trusted thos brands can be. Panasonic even when shorted won't blow up. It would heat enormously, though.

Next thing why I would use unprotected is voltage drop. I wrote there over at BLF. "Shure it is additional protection but it adds 2x on the voltage drop too. There is some variance in the protection circuits in the cell so they act each bit differently. Next, undercharge protection would trip in one pair before the other which leads to unevenly discharged cells. Also in this case you have to take the cells out in order to reset the protection. Well it depends whic cell in the series it was. "
 

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Discussion Starter · #9 ·
Nice review. Two questions:
1.Does using a box have an effect on runtimes? In other words given the same cells would output and runtime be similar to that of a welded pack?

2. Understanding batteries can be charged in the box, would it be better especially long term to use a seperate smart charger, given that a Magicshine charger or Glowworm from Action led is just a few bucks less than a 4 bay smart charger. With Lipo's I'm always cautious
1. It will have almost same effect on the run time as the welded packs with the protection circuit. There can be some differencies in the voltage drop since there are other elements in the circuit and mainly because of the spring contacts. Later at some time I might try to measure the differencies and I have some ideas for improvement most people would not do. It is hard to dissasemble the pack to get to the circuit.

2. As I wrote in the previous post, iI would combine both type of chargers for practical and safety reasons. Most of the time I would use 8.4V charger and from time to time separately charge cells individualy.
 

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Discussion Starter · #11 ·
As pointed out, this battery case doesn't have wiring coming from the middle (bottom contacts), so it is not able to monitor the balance of the cells while they are being charged. This is potentially dangerous, especially with unprotected cells, if one cell of either of the 2S pairs starts off at a lower voltage the other cell could easily get overcharged before the total voltage of the pair hits 8.4v.

In my opinion it is definitely safer to use a good quality 4 bay smart charger (and good quality cells like NCR18650). I'm currently using NiteCore D4 to charge the batteries used in these battery boxes.
I've already answered that, I hope, in previos posts. You are right, if it doesn't have middle connection one cell can be overcharged over the other. But as I said with good quality brand cell there is very small chance this would happen to significant extent in a short time (ie. 5 - 10 cycles). I've suggested I would take them out from time to time and charge the cells individualy. Checking voltage of the cells prior individual charge would give you information if the are starting to differ and you will know it then. Charging individualy would balance them again. AFAIK, no welded battery pack of whatsoever type has balancing feature integrated. They have overcharge protection. Having middle connection are better in this regard, but they can't be balanced unless disassembled. So there are Pro and Con.

I also agree charging with 4 bay charger would be the best, but quite impractical. Ok if you use it very seldom, but not when you are doing it on daily basis.

Those problems were actualy described in the review, I think.
 

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Discussion Starter · #12 ·
Do any of our standard welded packs have that extra connection between the and the bottom of the pack that you list as a negative here? Am I correct in assuming that's for balancing?

I don't know what I'm talking about electrically, but could the cross connection between the two sides of the pack be done via a trace on the PCB? If so, is it?

Is the voltage regulation for the USB port implemented on the board (ie four wires to the board), or is it done at the use head? I suppose it could also be implemented at the Y in the cable.

PS: The pictures don't seem to be working. May I suggest uploading them to MTBR, rather than using external links.
Most if not all welded battery pack has milddle conection, but it is used for overcharging purposes only, not balancing. That is the main shortcoming for all of them.

No, the cross connection can only be done at the bottom of the case between all four contacts.

I assume the USB voltage regulation is done on the board. I didn't opened it yet since I have to desloder all four spring in order to get there. This might destroy the usabilty of the pack. I might do it in the future, though

No one complained about the pictures in any of my reviews and I'm using same storage service. Can you explain bit more about the problem?
 

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Discussion Starter · #13 ·
What's the function of the on/off switch for?
My light works in both settings!
The purpose of the switch is solely to show the status of the pack ie. the voltage range. It should be off most of the time unless you want to constantly monitor the status. Be aware it uses some power so it very slowly drains the cells.
I should measure that somehow, though. Will add on to-do list.
 

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Old & New Solarstorm Battery Boxes

Hey!

Thank you for the fine review and all the work for it!

I'm using boxes of both generations and I would not call the later model improved, rather different. I actually find the new box inferior to the old box. While using protected cells charged individually and having no use for a USB output either all the new features are more of a hindrance than a help.

I ran a simple voltage drop comparison test to see how the two different generation boxes perform under around 3.4 ampere load provided with an XM-L2 Solarstorm XT40 light. Both boxes had protected 2600 mAh Sanyo batteries fresh from chargers in them and were used for few moments prior to any recorded values to get past the sharp voltage drop at the beginning. Readings under load were taken after they kept constant for around five seconds.

With the old box voltage dropped from 8.34 volts at rest to 7.13 volts under load and with the new box voltage dropped from 8.36 volts at rest to 7.03 volts under load. I was surprised to see such a major voltage drop under load, but it could be due to my test setting with an extra pair of connectors, and disappointed to see such a voltage difference.

After these measurements I realized that many of my power draw estimations are done with too great voltage values, that these boxes really bite hard on voltage and that I like the old box even better now.

Good rides!

JK
 

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The pix are working now. It must have been a glitch. When I looked yesterday the close ups of the pack were blank/broken links.

Does the thickness of the wire seem to change above and below the Y? If it's thicker below the Y that might indicate four wires, and therefore stepdown done at the board. If they're the same thickness, I'd speculate that the change is done at the USB head.
 

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Hi!

The new box has PCB, so it should read lower...is that why?
Yeah, the protection circuit board for sure takes its toll, and is useless to boot with protected cells, but there could be more to it like worse cables and battery holding springs. Also the step down circuit draws surprisingly much power, as Cat-man-do pointed out in another thread, you can't store batteries in the case for prolonged time if you like them topped up and ready for a ride.

Happy trails!

JK
 

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Can we see inside the cover?

Thanks for the great review! Can we see inside the cover? It looks like just 2 screws to access the board inside. It would be interesting to see the circuitry for the USB charging function and just the general layout and quality of the wiring inside.
 

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Discussion Starter · #19 ·
Thanks for the great review! Can we see inside the cover? It looks like just 2 screws to access the board inside. It would be interesting to see the circuitry for the USB charging function and just the general layout and quality of the wiring inside.
Yes will do that, but there is not much to see unless you unsolder all four springs from the PCB. All elements except the switch and status leds are hidden on the other side.
 

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Discussion Starter · #20 ·
Hey!

Thank you for the fine review and all the work for it!

I'm using boxes of both generations and I would not call the later model improved, rather different. I actually find the new box inferior to the old box. While using protected cells charged individually and having no use for a USB output either all the new features are more of a hindrance than a help.

I ran a simple voltage drop comparison test to see how the two different generation boxes perform under around 3.4 ampere load provided with an XM-L2 Solarstorm XT40 light. Both boxes had protected 2600 mAh Sanyo batteries fresh from chargers in them and were used for few moments prior to any recorded values to get past the sharp voltage drop at the beginning. Readings under load were taken after they kept constant for around five seconds.

With the old box voltage dropped from 8.34 volts at rest to 7.13 volts under load and with the new box voltage dropped from 8.36 volts at rest to 7.03 volts under load. I was surprised to see such a major voltage drop under load, but it could be due to my test setting with an extra pair of connectors, and disappointed to see such a voltage difference.

After these measurements I realized that many of my power draw estimations are done with too great voltage values, that these boxes really bite hard on voltage and that I like the old box even better now.

Good rides!

JK
Thanks JK for your comment. I have to say you are doing unfair comparation. If you use protected cells in both cases and we put asside spring resistance for the moment with old case you are getting resistance of the cells PCB while with newer case you are getting resistance of the cells PCB + resistance of the case PCB. So the voltage drop has to be bigger. There is no way to be different. With your test you can't say which resistance is bigger. In order to know that you should test also with the unprotected cells.
To me the most resistance could be in the springs, cable and connector anyway, but I have yet to prove that.
 
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