Should be arriving in the next few days, ill do a check when I can.
Anybody got good links on how to build a battery pack?
Link to a charger thats suitable for a 51.8V (nominal) 42Ah pack - its a Boston Swing battery combo 14s 1P
Hints and tips on BMS vs. Balance chargers?
Im reading away but all help appreciated
Those Boston swing packs are 1s8p. So if you put 14 in series they’ll be 14s8p.
Current wise that’s a max continuous discharge of 104A.
So Batteries arrived. All seem geniune but havent cycled yet.
Has anyone any tips on battery pack shape? I.e. long and thin vs. square or rectangular? Ive a deep enough board and ive no hatches etc cut yet so just wondering where is best to have the battery pack? Front to balance weight of me towards the rear or a long thin battery down the centre of the board etc. Thoughts?
Center mass of battery I recommend under your front foot, or just forward of that.
Short board, battery farther forward. Long board battery can be a bit farther back.
Many factors to take into account. Along with user preference. If you like to ride at the limit of top speed of your setup you want the battery a bit farther forward. If you want to ride slow and just cruise around the battery can be a bit farther back.
Wondering What would be the maximum height of the pack
Depends on what way you arrange it. Each 1S8P Pack has dimensions of 39x69x186(mm).
These are 8P and claimed 42Ah? Are these 18650 cells or 21700? Each cell must be 5,2Ah. For 18650 impossible.
Toto, these are not standard 18650 Batteries. Boston Swing 5300 is what they are.
Each Cell is 5300mAh - its not even the standard 18650 shape and before you ask is each Boston Cell 2 18650 joined in wrapping - nope - (because its the first thing I did lol) there are vids out there of people opening them up - Boston made their own shape of 18650 Cells.
Note: I’ve no idea if these are any good for efoiling but they were one of the best deals I could find as rightly or wrongly my target is cost.
So size is roughly 2x18650. Interesting cell! Never saw it before. Rating against capacity is a little low, but still ok for EFoil.
Keep us informed please.
Exactly my thoughts, do you think 80a rating is high enough? Looking forward to see how it will perform!
It is rated 13A max. continues. That makes 104A.
Will do. Not sure if any1 here has got them before me!
Will be spring before i water test anything serious but ill pass on bench tests and trial runs as I go.
Its a slow burner so be warned haha
So guys I’ve my battery pack finally quickly assembled just so I can charge it. Ive it all connected up and charging. So ive no BMS and have charger directly connected to battery. How does charger know that my pack is charged? I get that it knows its hit 58.8V cause i bought charger to that voltage but how does it know when its hit 42Ah? Some pics of manual and Charger attached for reference.
Depenyds on the charger, it probably does not know the capacity charged but it stops when it gets to the target voltage for your battery. If the battery is ok it should have charged it to the declared capacity when it‘s charged to that voltage.
So my charger got to 59.2V and stayed there for another hour-ish before the green light came on to say battery is fully charged. So im happy that the charger has fully charged the voltage but how can I tell if its charged the current fully? Should be 42Ah capacity if its fully charged according to the battery stamp
I’m not an expert in battery packs but I’m pretty sure there is a relation between the voltage and the capacity meaning that if your 14s battery pack is at 58.8v it should also be at full capacity (42ah). To be honest, I only rely on voltage to tell if my battery pack is discharged or not. You could test the capacity by discharging it at a constant rate (like 10ah consumption) and calculate the time it takes for the pack to discharge completely to 42v (3v*14s=42v).
Hi.
Interesting batteries. What is the individual cell type? Do you know the specs, and manufacturer of cells?
What is your build plan for this battery? Are you going to run a BMS? You need a method to balance the voltage of each of those 14 groups that are hooked in series.
The cells within each pack are hooked in parallel so they will keep themselves balanced, but the 14 groups hooked in series will not stay balanced.
It is very dangerous to have a battery with cells hooked in series without a BMS if you don’t know what you are doing, and if you are not very careful. You must monitor, and manually insure the cells remain balanced at all times.
You need two things to use a battery without a BMS safely. The first thing is you need to balance charge each cell that is hooked together in series. And the second is you need a method to monitor the voltage of each cell that is hooked in series while battery is being discharged.
The goal for lithium ion cells it to never let the cell voltage go over 4.2v and never go below 2.5v. Depending on the manufacturer recommendations the cell might last longer if cycled between only 3.0v and 4.1v.
There are many reasons why the cells get out of balance during charging and discharging. Cells hooked in series will not self balance amongst each other! The important thing is to make sure to stop charge before any cell gets over 4.2v, and stop discharge before any cell gets below 2.5v. So inorder to get full capacity out of the battery pack you need to keep the voltage of each of the groups hooked in series within 0.01v - 0.02v of each other.
Above 4.2v the cell will be damaged, get hot, and could have a thermal runaway and catch fire. Below 2.5v the cell will be permanent damaged leading to reduced capacity and more susceptibility to thermal runaway.
Anytime I buy battery cells the very first thing I do is test the cell to verify that it meets the manufacturers claims.
The manufacturer will state the amp hour capacity of the cell, and more importantly the maximum rate at which the cell can be continuously discharged and the temperature the cell will reach during this rate of discharge from full charge to full discharge.
The risk is too high to not test your cells. Be safe guys. Only buy cells from a reputable seller, and cells manufactured by a reputable manufacturer.
There is a reason you don’t see the eskate, and power wall community using off brand cells. They all use the same cells. Because they know the risk, and they know it’s worth the price for good cells. I prefer Samsung cells. But the Sony VT6 is also very good.
A 2 kilo watt hour lithium ion battery fire will not only burn your house down, but the whole city block! 
Thanks for the advise! Just seperated all 14 units and checked the voltage across them. Its standard at 4.2 or 4.22V so im happy that all the batteries are charged evenly. Some pics attached. Question now is how can i check the capacity? Can I build an arduino capacity monitor?
It would probably be the best to either use a bms to charge the batteries or build two 7s blocks and then charge them with a balancing charger. As a cheaper alternative you could use two cheap lipo buzzer alarms with display, that would show you the cell voltage of each cell, but no balancing in case they differ too much, only problem indication.
