Test/Review of GB 8.4V (7.2V) 6800mAh battery pack

4 posts / 0 new
Last post
HKJ
HKJ's picture
Offline
Last seen: 1 hour 6 min ago
Joined: 05/24/2011 - 12:23
Posts: 7451
Location: Copenhagen, Denmark
Test/Review of GB 8.4V (7.2V) 6800mAh battery pack

GB 8.4V (7.2V) 6800mAh battery pack
DSC_2599
Official specifications:


  • Type: Battery
  • Battery Type: Lithium-ion
  • Battery : 18650
  • Rechargeable: Yes
  • Voltage(V): 8.4V
  • Capacity: 6800mAh
  • Charge Time: 5 – 6h
  • Discharge Time: 2h
  • Over Voltage Protection: Yes
  • Over-charging Protection: Yes
  • Over-discharging Protection: Yes
  • Short Circuit Protection: Yes
  • Product weight: 0.196 kg
  • Product size (L x W x H): 8 × 8 × 5 cm / 3.14 × 3.14 × 1.97 inches

GB%208.4V%206800mAh-info
DSC_2597
DSC_2598
DSC_2600
DSC_2601
DSC_2602
DSC_3658
Inside the rubber is some shrink wrap around the cells.
DSC_3659
The protection circuit looks like it checks all cells, but it do not have balancing.
There is no strain relief on the cable.
DSC_3660
Connection cable is slightly above 0.5meter.
pcb1
pcb2
pcb3
The protection circuit, one chip and two dual transistors.
GB%208.4V%206800mAh-Capacity
Capacity varies with load and due to cable/connector resistance (Both pack and my test cable) the over discharge protection kicks in at different voltage (At the battery it will be 6 volt all the time).
I wonder why the 5A trace has as little capacity as it does. The Panasonic NCR18650B cell can handle 5A.
GB%208.4V%206800mAh-CapacityTimeHours
GB%208.4V%206800mAh-CapacityTime
GB%208.4V%206800mAh-Energy
GB%208.4V%206800mAh-PowerLoadTime
GB%208.4V%206800mAh-TripCurrent
GB%208.4V%206800mAh-Charge
Conclusion
I like the rubber packing and the supplied pouch, this makes it fairly easy to mount on a bicycle and gives some protection for bumps.
The pack can deliver the rated current, but not more than that. The missing strain relief is rather bad.
Notes and links
The battery was supplied by Gearbest for review.
How is the test done and how to read the charts

My website with reviews of many chargers and batteries (More than 1000): https://lygte-info.dk/

ledoman
Offline
Last seen: 1 month 4 weeks ago
Joined: 09/25/2010 - 06:27
Posts: 937
Location: Slovenia (EU)

Thanks HKJ, nice to see test of a bicycle pack. I’ve done review of very similar pack over at MTBRhttp://forums.mtbr.com/lights-night-riding/quality-8-4v-6800mah-4-x-ncr1...
Cells are the same, the main difference is protection module having 4× 8205A chips. Don’t have chance to measure high currents, but I’ve got more than 6A out of it.

I’m also wondering what happened at 5A measurement. With 2S2P setup there should be only 2.5A per cell. Peace of cake for the Panny cells. Maybe there is problem in the protection module and/or cabling, see below.

What interests me is what are resistances of cabling and connectors. We are always wondering what can expect from the conector of that type and what voltage drop it cause. Can you somehow measure the resistance of the whole path from battery pack to the “light” (ie. first part of cable, female + male conn. the other part of cable all together up to 1 meter long). OK we know what resistance of 20AWG should be, but we don’t know for the connector.

Edit: I’ve assumed it has 20AWG cable (like Kaidomain sample), but in reality it is 22AWG. Nevertheless, the main point of interest is 5.5×2.1mm connector .

garrybunk
garrybunk's picture
Offline
Last seen: 1 week 5 days ago
Joined: 10/31/2011 - 09:25
Posts: 6099
Location: Johnstown, PA

Thanks HKJ! I too wonder what happened at 5A.

-Garry

My Bike Lights Thread, Optics (TIR) Comparison Beamshots, Diffusion Techniques

, MTBR’s Lights & Night Riding Forum
NOTE: Now hosting my photos from my Google account. Post up if you can’t see them. Older photos hosted on Photobucket or Flickr may disappear (PM me if you want access to them).
HKJ
HKJ's picture
Offline
Last seen: 1 hour 6 min ago
Joined: 05/24/2011 - 12:23
Posts: 7451
Location: Copenhagen, Denmark
ledoman wrote:
What interests me is what are resistances of cabling and connectors. We are always wondering what can expect from the conector of that type and what voltage drop it cause. Can you somehow measure the resistance of the whole path from battery pack to the “light” (ie. first part of cable, female + male conn. the other part of cable all together up to 1 meter long). OK we know what resistance of 20AWG should be, but we don’t know for the connector.

You can fairly easy calculate the resistance. The overdischarge protection will always trip at the same voltage, what I measure includes the resistance of the cable and connectors.
I.e. when current is 0.2A the trippoint is 6 volt, and at 3A it is 5.6 volt, that is about 0.4 volt for a 2.8A change or 0.14 ohm, but I cannot tell if the transistor resistance is included in that value.

My website with reviews of many chargers and batteries (More than 1000): https://lygte-info.dk/