Noob project build mkII

Size12

100 µW
Joined
Oct 5, 2018
Messages
8
Hi everyone i have lurked around the forum for a bit while building my ebike and it’s always been a good source of knowledge and know how.
Just wanted to share my build with others and hope to become a useful member of the forum.

I decided to build my ebike to mainly commute to work as most of the way is cycle path with only a couple of miles of road section and fairly flat going.
I already had the bike a voodoo bizango 29er with disk brakes so used that as the doner bike, I went with a BBSHD 1000w mid drive as the thought of higher torque from the geared motor would come in handy off road and I’m a big guy at 210lbs ish.
I built my own 52v 14s6p battery using the vruzend battery system, from recycled laptop battery’s to start with but soon changed to some new Sanyo 18650GA cells in theory I should have 21ah in my pack I think?
I usually get about 15 miles of pas before the power cuts out not sure if it’s bms or the bbs controller that is cutting power maybe due to voltage sag? that’s on power mode 2 averaging 500w pas on display read out and averaging 25mph with a good peddle effort does that sound about right?

Thanks
Jon
 
With 21Ah of new Sanyo GA cells it seems you should be able to travel much (double?) further on a full charge. As you use Vruzent cell holder system do you also have a BMS hooked up to your cells? And have you allowed the pack to charge long enough for all cells to balance?
 
I do have a bms attached to the pack and have 2 chargers one 2amp and a 4amp but the pack gets to about 57.7v even with charger on overnight.
The charger does cut in and out after a few hours like the bms is working!
 
The highest I think it has ever got is 58v I guessed .8 of a volt was neither here nor there.
The first bms I tried did exactly the same I have also changed the battery’s to matched GA cells is it the vruzend caps maybe?
 
It could be that some cells are unbalanced. Have you tried charging the pack fully and measure the cell groups separately with a good volt meter? That's what I would want to know: if all cell groups are at least equally charged.
 
Thanks for your help slowco

My output voltages acorfing to my multi meter is as follows
Charger 58.6v
Battery load terminals 56.7v
Cell groups
1, 4.07
2, 4.04
3,4.16
4, 4.04
5 4.07
6,4.04
7,4.11
8,4.05
9,4.04
10,4.07
11,4.04
12, 4.14
13,4.17
14,3.67! Bad cell in the group?
 
That is a very unbalanced pack!
That lowest cell group probably pulls down the whole pack and causes the voltage sag that prevends the use of the whole capacity.

Check the connections of the Vruzend caps at the lowest group. Of that lowest group I would remove the cells and check them individually as there might be a bad cell that needs to be exchanged. If they are all okay (dis)charge all cells to 4V and reassemble the pack. Then charge the pack until the BMS starts balancing. It might take a long time for all cells to be balanced. After that measure all cell groups again. They should be within 0.01V to 0.02V from each other. Then the pack would be 14S x 4.2V = 58.8V.
 
Hi slowco,

I removed the last cell group and charged them as you suggested. All the cells seemed to check out ok so may have been a loose connection to the caps?
Charged all cells in that group to 4.05v and built them back up, I then left the whole battery on charge over night and all day today to hopefully balance the whole pack
I came back to 57v exactly on the discharge port :cry:
.03v between charge connectors is it yet another bms that’s faulty?
I am concidering running without one as they usually seem the route of troubles....
 
Might it be a problem with the voltage output of your charger? Have you tried both chargers and are they indeed for a 14S Li-Ion (58.8V) battery pack? What is the behavior of your charger when the pack is "full"? What is the output voltage at the charger then?
 
Yeah they are both 14s chargers when the battery gets to almost full charge the chargers cuts in and out like it should be balancing the pack.

I figured I had best ride my bike to work today to drain the battery, I am just recharging now so will report back soon.
Thanks Again.
 
Charger cuts in and out? Not the behavior I'm used to with a CC-CV charger. It should just switch from a constant current to a constant voltage state. And that constant voltage state should be 58.8V. Like this (just an example): http://www.pro-greenergy.com/product-detail/50v-14s-58-8v-2a-lithium-ion-battery-charger/

If your battery pack is charged fully check the voltage of the cell groups again to see if they are balanced now and at what voltage. If not to at least 4.15V per group and within 0.03V (less is better) put the charger back on and let it charge a night longer. And then check again.
 
Hey slowco
Here is the charger I bought https://s.click.aliexpress.com/e/cssAO1J2

I left it charging and “balancing” over night here are the reading this morning. Fully charged!
Output terminals
57.4v
Cell groups still unbalanced 3.98v to 4.17v this thing is driving me crazy.
 
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