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12V and 5v(USB) battery pack build. help.

Pexy

Feb 21, 2016
142
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Feb 21, 2016
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142
Greetings!
My brother asked me if I could build him a battery pack with 18650 cells that he got from work.
He wants a 12V output and a 5V usb output. There are 8 cells in total.
I was thinking of doing something in these lines:
1) Connect 2 batteries in parallel and then 4 pairs in series.
2) Get a 4S BMS for charging.
-something like this: https://www.ebay.com/itm/3-4S-BMS-P...7QbTzAPwEeS2zlA6ZarHvIYWIaxgtcFvGB5SzJxzp1l4c
or this: https://www.ebay.com/itm/3S-4S-5S-3...818b:m:mU0FwbeSu6Qs1LoApTvfXxA&frcectupt=true
3) Use a 12V and a 5V regulators on the output of the BMS to have a regulated 12V and 5V USB outputs.
- something like this for the 5V:
https://www.ebay.com/itm/4-USB-Buck...m=333205758397&_trksid=p2047675.c100005.m1851
- something like one of these for 12V:
https://www.ebay.com/itm/XL4016-DC-...7a50:m:mKFxXwzaQeLUQA8Maz0fJpQ&frcectupt=true

Am I going in the right direction and would something like this work?
Do you have any recomendations. What would you change and why?
All suggestions are welcome.

Thanks,
Sven
 

Audioguru

Sep 24, 2016
3,640
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Sep 24, 2016
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3,640
The very cheap No-Name-Brand Lithium battery charger and protection board from China is listed at 40A!
Does it work? Will it cause an explosion and fire?
 

Pexy

Feb 21, 2016
142
Joined
Feb 21, 2016
Messages
142
The very cheap No-Name-Brand Lithium battery charger and protection board from China is listed at 40A!
Does it work? Will it cause an explosion and fire?
Yes i don't trust it to handle 40A but I do trust it to handle around 5Amax that will be some what limited by the output regulator.
 

Audioguru

Sep 24, 2016
3,640
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Sep 24, 2016
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3,640
A protection board is supposed to protect against high load current. This one doesn't.
What about the extremely high charging current? A mother disaster.
Why doesn't ebay say the manufacturer's name?
A car is also dangerous. Would you buy a cheap Chinese no-name-brand car??
 

Pexy

Feb 21, 2016
142
Joined
Feb 21, 2016
Messages
142
Ok can you then recomend me a different board?
As for the charging I was thinking of using adjustable balanced rc toys battery charger (IMAX clone).
 

Audioguru

Sep 24, 2016
3,640
Joined
Sep 24, 2016
Messages
3,640
I buy Name-Brand American Li-PO battery chargers from my local hobby shop. They are made for radio-controlled models and do not cost too much.
 

hevans1944

Hop - AC8NS
Jun 21, 2012
4,727
Joined
Jun 21, 2012
Messages
4,727
Would you buy a cheap Chinese no-name-brand car??
Gee, are those available now here in the USA? Can I get one with an autopilot so I can snooze while it moovze? I would rather have a Kia Turbo Sport, but mebbe Chinee be all better, huh?
 
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