Building an 18650 pack!

atatistcheff

Solar Enthusiast
I'm looking for some advice for building a 12V battery with 18650 cells. I see that batteryhookup has some crazy cheap LG modem cells. So far I've built a battery using Sinopoly prismatic cells and Headway cells. However, 18650s just seem to be so hard to find for a good price and decent quality that I've shied away from them. Still, I'd like to try building one.

So this post is to get some advice on how to go about that. I don't have a spot welder but I can solder although I don't know if that's really a good idea for these cells. One thing I'm wondering is how many cells should be in series for a typical 12V battery? I'm thinking of something around 60Ah so if we are using 3s it would mean a 3s24p pack with 2500mA cells. With LiFePO4 we do 4s batteries but apparently with the lithium 18650s we do 3s?

Any thoughts on methods to hook these together would be appreciated. If it helps, the modem batteries I'm looking at are here https://batteryhookup.com/collectio...-lgabb41865-cells-lithium-ion-modem-batteries.

The specs are here http://www.batteryspace.com/prod-specs/5457_B4.pdf

Thanks in advance!
 

Picasso

Solar Addict
Just go with larger format LiFePO4. For 18650 you will want a spot welder and not mucking about overheating cells getting solder to stick. Playing with used cells you need a few other tools to cycle test them.That said some cheap 36v building blocks https://www.techdirectclub.com/18650/
 

gnubie

Photon Sorcerer
Soldering onto the end caps of cells isn't a good idea but sometimes you have no choice. The problem is heat soak. The heat will quickly damage seals. If you do go down this path you want to have a decent soldering iron, 80 watts. You need to reduce the time it takes to attach the wire. Have a damp cloth / towel on the table, you'll use this to cool the end cap quickly. Use 60/40 solder not a modern lead free solder.

Tin the wire
Put flux on the endcap
Position the wire so that it is in its final connection place
Apply a little solder directly to the iron to get a small blob on the tip

Put that in contact with the endcap, and add a bit more solder so that the joint flows and the wire / endcap are wetted properly
Remove the iron and let the joint cool just enough that it is mechanically stable
Push the hot end of the battery into the wet cloth / towel and leave it there for 30 seconds.

The last 3 steps should take no more than 5 seconds.

I think the Mr Carlson's Lab youtube channel did a guide on how to solder batteries.
 

Supervstech

Administrator
Staff member
Moderator
I'm looking for some advice for building a 12V battery with 18650 cells. I see that batteryhookup has some crazy cheap LG modem cells. So far I've built a battery using Sinopoly prismatic cells and Headway cells. However, 18650s just seem to be so hard to find for a good price and decent quality that I've shied away from them. Still, I'd like to try building one.

So this post is to get some advice on how to go about that. I don't have a spot welder but I can solder although I don't know if that's really a good idea for these cells. One thing I'm wondering is how many cells should be in series for a typical 12V battery? I'm thinking of something around 60Ah so if we are using 3s it would mean a 3s24p pack with 2500mA cells. With LiFePO4 we do 4s batteries but apparently with the lithium 18650s we do 3s?

Any thoughts on methods to hook these together would be appreciated. If it helps, the modem batteries I'm looking at are here https://batteryhookup.com/collectio...-lgabb41865-cells-lithium-ion-modem-batteries.

The specs are here http://www.batteryspace.com/prod-specs/5457_B4.pdf

Thanks in advance!

Lithium ion cells are not ideal for 12v battery builds.

LiFePO4 is far superior in many ways. 3s 4.2v cells yield a MAXIMUM charge of 12.6v most 12v appliances need 13.8v operating voltage, so a battery with 12v appliance output needs a boost converter rated at the amps of the appliance demand.

A 4s LiFePO4 bank yields 14.4 (3.6x4) max volts... much better for 12v loads.
 

atatistcheff

Solar Enthusiast
Lithium ion cells are not ideal for 12v battery builds.

Thanks, that's just the kind of info I am looking for. I think trying to build a 12V battery from these regular lithium (not LiFePO4) 18650s is probably a non-starter. I ordered some cheap ones to experiment with but will probably just use them for running my ESP8266 projects or maybe a small UPS battery.

On the subject of volts if creating a 12V battery do you think it would be better to use 3s and a boost converter or 4s/5s and a regulator to arrive at the 13.8V?
 

morth

Solar Enthusiast
Building 12v batteries with Li Ion is sort of a pain due to the cell voltage. 4s puts you at 16 volts, which may be too much for the application. 3s is at 12, but only fully charged and it quickly drops to the 10-11 range, which also may cause problems with something that really needs 12-13 volts. LiFePO4 is much easier to deal with when voltage is more important. Powering things like lights or fans, the voltage difference may not be a big deal, but some 12 volt appliances are not very tolerant of voltage differences.
 

Supervstech

Administrator
Staff member
Moderator
Thanks, that's just the kind of info I am looking for. I think trying to build a 12V battery from these regular lithium (not LiFePO4) 18650s is probably a non-starter. I ordered some cheap ones to experiment with but will probably just use them for running my ESP8266 projects or maybe a small UPS battery.

On the subject of volts if creating a 12V battery do you think it would be better to use 3s and a boost converter or 4s/5s and a regulator to arrive at the 13.8V?

All the portable power units use boost converters for regulated power access... likely that is the best plan, but neither is ideal...
 

BoloMKXXVIII

Fully Charged
I really like how flat the voltage curve is with LiFePo4. In many applications you do not need to regulate the voltage as it only really dips when the battery gets near depletion.
Another advantage of LiFePo4 is they don't explode if something goes horribly wrong.
 
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