The voltage read out from this Li-on battery meter is about 5.99v at 99%, which is different from 7.4v listed on the battery. The battery meter comes with very little instruction.
Also, I thought this is a 2-cell battery. But the meter can only reads it as 1-cell. For those who are familiar with the meter and RC Li-on battery, please explains the discrepancy? Thanks in advance.
Cyberbrick battery specs
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I’m pretty sure this style of LiPo tester expects a 2S LiPo to use a 3 pin connector, with the middle pin connected to the contact between the two cells.
This is how the tester can measure each individual cell, but the CyberBrick batteries probably have an internal management chip that handles the balancing, making the requirements for a charger less elaborate.
5.99 and 99% sort of looks like a max value somewhere in the code of the tester and I have a feeling that the voltage across the terminals of the battery might actually be a little higher.
If you decide to take the pins out of the connector or use test leads to connect + and - with an extra pin in between, be aware that a LiPo/Li-ion battery like this can supply quite a bit of current and will probably melt stuff if shorted, so be careful 
The panel on the Meter shows it’s using a 1S configuration which is incorrect, the battery is a 2S configuration. Your readout is probably saturated. Read the manual and see how to set 2S configuration.
A couple of problems here…
You do not have the connector installed correctly.
I don’t know what “ve” is supposed to be, and I’m too lazy to go look it up (I probably have one of these meters in my box of older radio control related gear). But the black wire on the connector should be aligned with the “-” pin and the red with the “1” pin.
I’m surprised it is reading anything at all. I suspect it may not be reading correctly.
These pins on the battery checker are really intended for a LiPo pack that has a “balance tap” that allows the checker to see the individual cells in the pack. You would actually see two voltages if this pack had a balance tap, one for each of the two cells.
It says 1S Li-Ion but also 99% which is wrong. I think it’s confused. A Li-Ion cell should have a max voltage of 4.1V.
If the plug will fit, try the NiCd input. That’s designed for packs that don’t have balance taps, and odds are it’ll read the pack voltage correctly. Ignore anything it says about %.
Although, it may in fact be reading the voltage correctly. In which case you should charge the pack. The minimum voltage for a LiPo is 3.0V/cell, so 6.0V for the pack. You’re at the minimum.
I’d add that, IMO, on first blush it looks kind of bad that BBL is selling what appears (based on the 7.4V rating and 8.4V charge voltage) to be a 2 cell LiPo battery that doesn’t have a balance tap. Balance taps also connect to LiPo chargers that ensure individual cells never exceed their absolute maximum voltage (4.2V), because doing so can cause them to catch fire. “Unbalanced” LiPo pack charging is a no-no.
But it would arguably be criminally negligent to sell a LiPo that is unprotected and so, could be overcharged. I suspect this pack has “button top” cylindrical LiPo cells (or the pack has something called a Battery Management System, a small circuit that protects otherwise unprotected cells). This type of built-in protection circuit prevents cells from being over-charged or over-discharged (which is a fire risk). And also allows them to be safely charged as a single 8.4V battery with no balance tap.
I suspect built in BMS as it simplifies things and takes care of most risks that could cause harm to novice users. Also looks like “charger” they are selling is outputting only 7.4V so this battery will never be at full capacity.
Edit:
I have ordered few of those as have different use for them and might sacrifice one for the science.
If you cut the heatshrink open, post a picture of what you see inside.
That was the 1st thing I tried, the readout was all zero. So I tried the way in the picture. Now I think of it, maybe BBL shipped the battery without charge in it…I’m charging it now and will try it again after it’s fully charged.
I have no idea what “ve” stands for as it comes with a minimal instruction that doesn’t mention anything about “ve”.
I just measured the voltage no a new battery straight out of the packaging and it read 7.8v, which seems like almost full charge for a 2S pack. The norm for new batteries is to ship with a little below full charge as the shelf life is better at that level of charge (it used to be around 60%, but maybe newer chemistries are happy with closer to 90%)
Don’t do that I already took one apart.
Willing to post some photos/findings? Does it have integrated BMS?
Everyone in the world must be aware of the risks of fire with Lithium batteries. There have been plenty of disasters, from Sony laptops, Samsung Cell Phones, Boeing 767 backup batteries, “hoverboard” things, etc., etc., etc… But there were also more than a few full-size airplane crashes caused by battery fires in the cargo on board.
As a result, the world changed the rules for how these batteries should be transported. One of the rules is “never by air”. By sea or land, only (where they sometimes still catch fire, but don’t cause the loss of life a plane crash would). The other rule is “never fully charged”. Lithium batteries should be shipped at around 50-60% charge level, which is 7.4V to around 7.8V.
Batteries are chemical energy storage systems. The higher the State of Charge (SoC), the more energy they contain and the more damage they can do if they fail. They are also more likely to fail when fully charged. Best practice is to never charge unattended and only charge when you expect to actually use the battery, so it’s not sitting around fully charged should it fail).
So that pack is in its ~50% charge level, which is where it should be if it was just shipped to you. It needs to be charged, after which it will read around 8.4V because each LiPo cell charges to 4.2V.
It has a BMS with balancing and a SMT fuse of unknown rating.
It still reads zero after the battery is fully charged (provided USB charger stops blinking). I don’t know if the meter is defective or not…
What device you used for measuring the battery?
I used a Fluke Multimeter. I actually have a device very similar to the one you have, just a different brand, but I can’t find it ;-).
But I’m pretty sure you will have to connect it as if it’s a 2S battery pack for that checker to work properly. That would be the black contact at (-) and the red on the pin marked 2.
Years ago when I got that checker it had issues with weird connections but the brand I worked with ended up getting a firmware that could read that brands slightly weird balance connectors.
If the Fluke says it’s 0V, the battery is defective. Either it self-discharged all the way to zero, or the BMS has failed open-circuit. Or the fuse has blown.
The problem with BMSs is that the really small ones can’t carry a lot of current (Amps). Probably why the pack has a separate fuse. It’s possible that, if you momentarily shorted the battery leads, you blew the BMS or the fuse. Take it apart and probe the cells directly and/or just ask BBL for a refund for defective product.
The Fluke said 7.8V on the output connector for my new battery, so all looks like to be fine and dandy with that one.
That didn’t work for me, no readout at all.
In that case you will probably have to find another checker tool, as the one you have isn’t suited for batteries like that
