First battery build questions galore

Batteries, Chargers, and Battery Management Systems.
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destro23   100 mW

100 mW
Posts: 45
Joined: Jul 09 2015 1:28pm
Location: New Jersey

First battery build questions galore

Post by destro23 » Sep 20 2018 6:30pm

OK, so i picked up a small box of dell laptop batteries and they are all sony SF US18650GR G7 https://secondlifestorage.com/t-Sony-US ... ificationsUsing liito-kala 500 charger i've tested every cell and have put any low voltage/dead cells or ones that got to hot to the side and won't be used.

I also just received in the mail a diy spot welder from https://malectrics.eu/ and it's working GREAT so far! the test spot welds that i've done have been very good (considering i don't know what i'm doing lol)

i'd like to build a 48v pack. most of the cells rate from 2000 to 2300 mah. My question is what is the discharge amp rate per cell? Am i missing something in the above link?

i'm going to pair this battery with a magic pie v5 . and i've read everything i could i think i'm just missing something on the math side of pack amp discharge rate and magic pie controller math to make a better paired battery.

also what gauge wire for charger, and what gauge wire for power to motor?
what type of wire do you use?
and what connectors are you using? xt60 for charger and xt90's for power to motor?

i bought 2 cheap 48V 35A 13S BMS off ebay (where do you guys trust 48v bms boards from? )

also i'm going to have about 40 cells in the 1000-1500 range(they weren't high capacity to begin with). is it wrong that i think i'd like to make a 13s2p battery for practice? and also hook up a bms as well for practice on spotwelding and bms ?


thanks for any help suggestions on my first battery build would be great

Thanks!

EbikeAus   100 W

100 W
Posts: 210
Joined: Feb 04 2018 5:58am

Re: First battery build questions galore

Post by EbikeAus » Sep 21 2018 4:50am

I have bought bms from this seller and am happy.

http://s.aliexpress.com/QnMryQvu?fromSns=Copy to Clipboard

I'd say go ahead and make a 13s2p battery but I wouldn't use it on your bike.
Being laptop cells you will need quite a few in parallel as they won't be high drain cells.
I usually don't ask more than 1-2 amp max per laptop cell.
Hope that helps
Choose LiFe 8)

May all your batteries be fully charged and perfectly balanced :P

999zip999   100 GW

100 GW
Posts: 8354
Joined: Jan 10 2010 1:40pm
Location: Dana Point So. Cal

Re: First battery build questions galore

Post by 999zip999 » Sep 21 2018 12:39pm

I agree go make a test 2p battery then buy some cells and make 6p battery with good new cells of ebike quality. This battery is pulling you up a hill and not laying flat on a table top.
Last edited by 999zip999 on Sep 22 2018 2:47pm, edited 1 time in total.

destro23   100 mW

100 mW
Posts: 45
Joined: Jul 09 2015 1:28pm
Location: New Jersey

Re: First battery build questions galore

Post by destro23 » Sep 22 2018 2:09pm

Thanks zip.

any suggestions on wire gauge and type?

999zip999   100 GW

100 GW
Posts: 8354
Joined: Jan 10 2010 1:40pm
Location: Dana Point So. Cal

Re: First battery build questions galore

Post by 999zip999 » Sep 22 2018 2:52pm

I buy the silicon 1,000 strain 10ga from hobby king or 8ga. If needed. I found IMR in Texas has good prices on cells. I have not used them. There has been a lot of research on high-density versus high discharge cells and you should be able to find. One to fit your needs. I go with a higher power cell vs higher-capacity thinking the higher power cell will have less stress and last longer.

999zip999   100 GW

100 GW
Posts: 8354
Joined: Jan 10 2010 1:40pm
Location: Dana Point So. Cal

Re: First battery build questions galore

Post by 999zip999 » Sep 22 2018 2:57pm

I don't use a BMS I just build a good size battery mine is 20 ah with sense wires for checking and balancing. It would be harder to do the smaller the battery gets. I think the magic Pie has a 25 amp to 30 amp controller inside. So build a battery for a 40amp controller as not to stress battery. It does not hurt to have a bms . I did on my first two batteries. But find an extra set of sense for checking with a cellog is quick and ez check of state of charge. Check out Dr angle's threadshttps://endless-sphere.com/forums/viewtopic.php?f=2&t=47924&start=125&hilit=Toolbox+bargains

destro23   100 mW

100 mW
Posts: 45
Joined: Jul 09 2015 1:28pm
Location: New Jersey

Re: First battery build questions galore

Post by destro23 » Sep 22 2018 3:20pm

If the batteries are 5amp continuous do the amps add up on the parallel?

999zip999   100 GW

100 GW
Posts: 8354
Joined: Jan 10 2010 1:40pm
Location: Dana Point So. Cal

Re: First battery build questions galore

Post by 999zip999 » Sep 22 2018 6:35pm

Yes but 5amp cell at 5amp may be warm. Warm ok . Hot no good. Just check with your ambient temperature regulator God given. Your hand. If it's cooking marshmallows it's too hot.

999zip999   100 GW

100 GW
Posts: 8354
Joined: Jan 10 2010 1:40pm
Location: Dana Point So. Cal

Re: First battery build questions galore

Post by 999zip999 » Sep 22 2018 6:39pm

P.S. this ambient temperature regulator can also be used for your controller and Motor if you can't touch it stop doing what you're doing. Hills the two chicks on the back rack or ect. Flavor.
P.S. 2 keep your wire short and fat as opposed to skinny and long.

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