I’m on the same boat. I’m just starting to buy supplies for an electric wakeboard. I plan on building my spot welder out of a transformer and some copper nails.
As for the 18650 batteries I got 168 of them for $307 on alibaba including shipping.
They are not name brand but have 2600mah at 3c discharge. Putting them in 12s 14p battery. Still haven’t decided on a motor (maybe sss 56104 500kv) or esc (maybe turnegy 200a).
I have had so many issues with BMS in the past. (With rc cars and solar setups). Now I just balance charge but the cheap ($30-50) only go up to 6s. I’ve resulted to just use two 6 s battery packs in series. Does anyone else do this?
Maybe I’m just cheap when it comes to the BMS.
Yes, I do this now, most of us do I think. BMS are not that much money in the grand scheme of things though, they are only $100- 150USD to manage $1000 battery pack that should last a long time, but 6S is simple no doubt.
This is the bms i use for my e-skate. I need it only for charging, since the vesc controls discharge current. For the e-foil however i use a bms for charge and discharge, since the flier esc does not have any battery protections.
I have built a number of battery packs for ebikes. You need to be wary of batteries with no branding as the mah will be exaggerated. Even suppliers who are selling genuine brand names can be dubious make sure you are getting what you pay for. Using a BMS can be expensive for anything over 100 amps but by splitting packs into 2x 6s you can use a hobby charger and battery alarms to monitor batteries. Watch this videoBms vis https://youtu.be/pljSZcEwc8Q
I follow with lot of interest this discussion because this will be next step toward a more mature efoil. @Alexandre, can you share more details about that Arduino based spotwelder? Is that a diy or kit? Looks good!
exactly working on a mature efoil 2019, just order a larger waterproof case, 30x40x10cm, to built the board around it, and i will built the battery pack to fit the case
battery pack will be 4s or 6s x 2 to be charged with the same charger as lipo, no BMS
i will be using nickel plate in H 0.15mm, each hold 5A , i won’t double them and i will use the 18650 at around 5A as well ( will last longer and no overheating the cell), so probably i will need 20P
so 2 x 4s20P
Thank you for the info! KWeld might be more “advanced” but costs 70euros more.
I thought about 2 x 6s14p banks, 168cells.
Would be awesome to source a trusted supplier and cut a nice deal for the forum!
I also bought the same spot welder @Alexandre
I thought about using the 18650PF (as they have a good price/power/energy relation), but then got offered the LG 18650 M36 for a VERY good price, so I will use them in the end I guess.
But at first I need to spend the time and finish my foil and test it with the LiPO I have…
M36 looks good, the same as 30Q: 2,25A to 3,3V (my target) at 5A discharge rate
the 18650 datasheets gives me a headache, at the end i think it is all about the same, efficency cost life span… one expensive pack or two cheap one, cheaper cells but you need more to acheive good reliability= cost the same
now i am at 44 cycles on my lipo ( 2 chargers charging 2x2 in parallel) very good IR with this multistar (0,9 Mohm!)
I’ve done 10K Km on my E-Bike with diy battery, it is 2* 6S5P. I’ve built a special wiring harness that configures the pack as 12S5P when on the Bike (by plugging in I also connect two LiPo Cell Meters). The other cable on the charger makes it a 6S10P Pack so I can charge it with one Charger in one run.
Only benefit in a BMS I see is less exposed wires.
If I can lend some advise here. I’ve ordered 18650 from aliexpress before and i’m sure that alibaba might not be different. They claim that there batteries is 2500mah or 3000mah and with this in mind you plan your battery pack, however when you receive your batteries they are only 1200-1500mah or less. When you buy make sure you only buy panasonic, LG or samsung, nothing else even if they are more expensive. You might want to look at using premade battery packs Usually 10S3-5P are better (lost of power and lasts long with a BMS so you dont have to ever remove the batteries like with LIPO and charge them on a balance charger (what a big pain).
this looks very nice - but since watching this video (https://youtu.be/pljSZcEwc8Q) - thanks to @mp105 who posted it - i’m not sure about the need of an BMS - and least in an very diy-experimental setting
I just use a cell-logger and a fuse …