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Here is the review of the Storm2 Liquid as requested (after owning for an hour or so). Not much to review really other than to make the following points.
This is a 93.5Wh portable emergency battle I just received one of the first copies of as an early kickstarter backer. It uses 8x 18650 internal Li-ion batteries.
The screen is loaded with tons of information in a very sexy high resolution display with an impressive color range. The info reported on the main screen and info screen are: Internal battery voltage and current, time running, input/output/combined current/voltage/wattage (so for example it shows what voltage the USB-c I/O are negotiated at), battery and CPU temp separately, it even tells you the internal battery voltage of each of the 4 parallel cells separately in addition to the combined battery voltage.
Not just the screen is sexy but the whole case really and you can see the 8 li-ion cells inside.
Comes with USB-C and DC-jack input ports that can also be switched to output ports. Has an additional USB-C output port and USB-A output port as well.
The DC jack acting as an output port means you can use it to charge non-USB devices and even comes with some alligator clip outputs for the DC-jack and you can easily buy standard output jack adapters to connect to any format dc jack imaginable.
Obviously the output DC jack setting lets you configure the voltage in 0.1V increments up to 25.2V, I think it handles either 3A or 5A output, need to check spec. However irf the DC-jack output is on as you adjust the voltage it updates the current out of that port in real-time which is useful.
Overall so far I cant find a single thing to complain about, this thing has all the data and features id expect and want and done as stylish as they could have hoped to do. IT is also about as small as you can get since 90% of the space is the batteries.
@zpartacoos #kickstarter #electronics #Storm2Liquid #storm2 #storm @Electronics
@freemo @zpartacoos @Electronics
> portable emergency battle
:D
> it even tells you the internal battery voltage of each of the 4 parallel cells separately
What do you mean by parallel here?
I actually had it backwards it is 4 in series and 2 in parallel. Parallel is matching positive to positive and negative to negative. It will increase the current output but the voltage will be unchanged. Series is end to end - paired to positive and will increase the voltage while keeping current the same.
So here we have 4 in series which is 3.7 * 4 voltage, and 2 of those in parallel giving it double the capacity it otherwise would at that voltage.
@freemo @zpartacoos @Electronics
Do you know why a parallel connection of series connected cells might be preferred over a series connection of parallel connected cells?
A series connection of parallel cells would be prefered over a parallel connection of series cells. The reason being that the control circuitry on a balancing battery management system is much simpler. The downside is that if a battery goes int he form of a short (which is how these things die a lot of times) it will take its parallel buddy with it. So simplicity has its draw backs too but int he end simplicity ultimately wins out.
@freemo @zpartacoos @Electronics Wouldn't a short of a cell cause the string that's now one short to start being charged by the still-complete string at some very high current?
Well, I guess it's strictly better than the other arrangement, where some cells would be simply shorted.
If in parallel yes, the short would be the same as shorting out its parallel cell. In series however no, the short would be the same as just removing that cell from the series as if you had connected the negative and positive terminals of the adjacent batteries with a wire.
@freemo @zpartacoos @Electronics
> as if you had connected the negative and positive terminals of the adjacent batteries with a wire.
Yes. Which means that we now have strings with different cell counts connected in parallel, right?
Yes but the battery management system will handle it and save your ass by taking the damaged cell out of the circuit. In the case of the opposite configuration it wouldnt be possible to electrically take it out of the circuit without a great deal more complexity in the battery management system, thus my comment about complexity.
Depends largely on what BMS we are talking about and what sorts of protections are in place. Attached is an example of a very simple 2 cell series BMS that provides short protection as well as voltage balancing.
Notice that the cells being in series as they are, and that the power output does **not** come directly off leads of the battery to the load but go through the BMS board itself. So if one battery is replaced with a short here you wont short out the other battery, and thus its safer as it wont explode. Now if you take this and stick two of them in parallel with the power outputs being in parallel rather than the batteries being in parallel directly then you have the same protections since the BMS would have something like a diode or similar in place to prevent any sort of backfeeding should there be a short and voltage drops. In fact, should a short be detected it can take the whole thing out of circuit.
@freemo @zpartacoos @Electronics What control does BMS have? I thought the parallel connection of series strings setup had the parallel connection made just with a wire. Did you envision something different?