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.
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:
Cons:
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.
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 source | Gearbest | Kaidomain |
3 status leds | 8.4V | 8.4V |
2 status leds | 7.45V | 7.60V |
1 status led | 6.95V | 7.10V |
1 status led flashing | 6.45V | 6.60V |
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.