Must say this: please
use attention when using these batteries. For Li-Ion cells High temperature, over-charging, physical damage and other conditions can be dangerous for you. Please check out the safety indications here in the forum and on the Web
im really out on the deep end here, need help whit a couple of things. i have found a few presumble good cells from some power tools, and now i have to start building something whit them. i have 5 tp4056 chargers from alixpress. they take, and hold charge.
Now i would like to build battery pack for an rc-car,( yes its a 12 volt i know sorry) see file attaced.
Can i build a 4s2p and use a DC-DC step down LM2596 module.?
Your cells are us18650vtc4, start from seeing the specifications on
datasheet https://secondlifestorage.com/index.php?threads/sony-us18650vtc4-cell-specifications.1697/
Each cell is 2000mAh capacity. Consider yours are maybe some years old and may have lost some mAmps.
I would make a 3s2p because each 18650 cell has a maximum voltage of 4.2V, using them in 3s makes 12.6V 4000mAh. I suppose your motor would run on 12.6V without complaining... but don't believe what I say, maybe do a test on a second motor of the same kind
. You could even charge cells up to 4.1V instead of 4.2V to stay on the safe side, but motors do have a bit of tolerance on voltage, and you can avoid voltage step-down.
I dont know how many amps the car draws. Anyone of u have a guess?
I suppose the rc car contains a small motor. You could find the model written on it and search that too, to find out how much it uses. Remember when talking about devices on batteries we speak about milliAmp/hour (mAh).
And how is it aginst the power of lead vs. li-ion. Is a 4s2p ok. if i use us18650vtc4 cells. (no i do not know the capacity the actual battery has)
Oh, you will love performance with Li-Ion and have benefit for the lower weight. Your actual acid-lead battery is 1900mAh, that's what I read from your photo, correct? So with a 3s2p pack you'll have more than double capacity.
Edit: you should check how much the motor uses... if it has a high wattage (or a high mA requirement) you should consider getting some power cells, the ones you have seem energy cells to me. Power cells are made to give a lot more power per time unit (like for drills and stuff like that).
Your battery gives you 2000mAh with a discharge rate of 0.2 that is using 400mAh. If your motor wants a lot more power then, yes, you should switch to power cells, yours maybe won't give you a good performance -but when you'll experiment them on road you'll tell me what happens!
One detail i have left out is the charging. is it ok to take batterys out of car and charge them singly in tp4056, and can i run the batterys as flat as i want whitout hurting them?
You can find 18650 at real good prices (yes, spend 3$ more and get a good brand!). I would keep two or more packs, while charging one pack you use the other.
Yes, charge them singularly with your little boards (why not consider buying your first Li-Ion 4 cell charger: my first charger was a LiitoKala Lii-500 for 15€ -our forumers here will divert you Opus brand, yes, better).
Your battery cut-off is at 2.5V (check datasheet), I think your car will start going real slow under 8V, when that happens just mount the other fully charged pack. Do check voltage every time you remove the discharged battery with a multimeter.
I don't use tp4056 so I really can't say, I suppose is tp4056 have a correct charge curve and doesn't overcharge them over 4.2V it should be ok.
[EDIT: I checked these little tp4056 modules out; some have overvoltage protection and all other good safety stuff; check you model out, they should be ok]
Friendly newbie greetings from Sonnymountain
Keep us updated!
jes
