I do run 13S.
With my new (very expensive) aluminum case and additional 5 parallel groups (20 total now) I haven’t had any issues since.
I think I have set it to 360A or even 380A
Mine unfortunately does not. I wish it would. Screen Recording is a good idea though.
Update, after 8 flights I noticed major cracking in many of the vruzend caps. I got some of the first batches of their v2.1 caps and they found that this was a flaw in them, vruzend since changed the polymer mix now so they are stronger and are sending me replacements which means i’m going to rebuild my pack. This is okay because I want to make some changes.
First change - add 1a active balancer to get full capacity out of my pack.
Second - go up to 4 gauge leads instead of 8 gauge
Third - add extra bus bar on the series connections, currently I have one bus bar for all parallel connections and two for series, if I go to three on the series i’m thinking this should reduce voltage sag.
Fourth - reduce pack size
The reason I want to reduce the size of this pack is weight, it’s very heavy on the frame, the paramotor has hard time balancing when standing on uneven ground due to the weight. I am thinking of going to 13s18p sized pack, this would drop my battery weight by 8-10 lbs. I am using LGHG2 cells which are rated 20amp continuous so with 13s18p pack i’ll still have max continuous draw of 360 amps, I rarely even go to 300 amps even on take offs, usually around 280. Thoughts? @etienne
The 13s are a much better fit… with your 14s you had the noisiest OpenPPG with over 800 km/h tip speed! At level flight you should be at 137A and at climbing at 303 A. At full throttle you will be at 355A!
Appreciate the numbers!
Li-ion cells sag more than lipos do. You can’t change that by adding more bus bars. As long as the bus bars can handle the amps the resistance of the bars would be too small make a noticeable impact to the sag.
If you drop your volts by switching to 13S you will have less available power but 360 amps at 13S is plenty. I use 360 amps with 12S just for a few seconds on takeoff. But, I thought you had problems with heat? If you cut 10 pounds off your battery it will get hotter.
Heat issue is gone after I changes the wiring on the leads to the battery ends. Initially was only taking power off of every second cell, changed it to every cell, now my temps are about 25°c. Vruzend highly recommends I also switch to 4 gauge wire leads instead of 8.
How would I test if two bus bars are enough to draw that much amperage. Only reason I say going to three is because vruzend recommended it for the amount of amperage being drawn at full throttle.
For sure will go down to 13s, add the 4gauge wire and active balancer in addition to the bms. Just debating whether or not I should reduce the parallel groups to 18p
my setup is still at 13S20P
(I changed it to that after 15P was not sufficient) and I am even thinking of topping this up to 25P or even 30 P (even though I don’t know where to add the extra cells yet).
I can confirm that reducing the parallel groups will increase the load on each individual group and increase temp on each cel, but 18P with the LG HG2 should still work though.
What brand of cells did you use? Wow that would be a big pack, i’m finding i’d rather go lighter vs having all that weight, especially after my hard landing when the power cut off. It’s just too heavy.
I also cannot get the pack to charge to full capacity with our bms, one group of cells always hits the 4.2v cut off before the rest, leaving the pack at 58.1v charge usually and it refuses to charge to full 58.8v capacity. Adding this active balancer is a must for our lithium ion packs if we want to use it’s full capacity. I am going to install it in conjunction with the BMS. They can work together separately to balance charge the pack to full capacity. It’s also from what i’ve read much easier on the cells, a bms will balance charge by dissipating the higher voltage cells in the form of heat, where as an active balancer uses the higher voltage cells to charge up the lower voltage cells.
Here’s link to the one I ordered.
My next winter project is to use an active balancer on my Lipo’s! If I understand it correctly this one
will work at discharge with 2A active balancing. It has super capacitors and uses external power…
Do you have a link to that?
I thought about something like this but I don’t know if 2a would be enough to actively balance during our high discharge rates. Even in cruise we are pulling 130-150amps, so I’d be very surprised if it could keep up and balance the cells during discharge. From what I’ve read they are quite slow to balance the cells which is why it’s mainly for charging and not discharging. This would be good for something that has a slow draw of power off a battery pack and would keep the cells balanced.
With 2A it should be able to equalize a 5% difference of one cell within 15 minutes…
They are available with 1, 2, 5 and 10A active balance charging. This is why you need a
external power source. Other active balancer use the power from the highest cell and
can charge maybe max 1.2 A. Since I have 4 x 6 Cell Lipo’s it could work out… With
lipo’s there is a problem that only one cell from 24 discharges quicker and you have
to shut off all power to save the lowest cell.
You can buy them at ebay, AliExpress etc… At least it sounds great and I will get more
info in the next months!
The active balancer won’t do much in flight. It will be too slow to transfer that energy.
I’ve built a few e-bike batteries (30amps, not 300) without BMS, discharging and charging for over 2 years, and the most it’s been out between cells is 14ma. good pack design is important. I think you’re on the right path.
The problem it seems is not even enough current flow. IF you have a wire going to every cell in the last group (on both negative and positive) then you need to beef up your bus bars.
You still might have a few weak cells that is causing this as well. I had a new batch of 200 LG 2ah/10A cells, found 4-5 deadones, and another 4-5 died after I capacity tested and added them to the good pile.
An update. So I got about 4 flights on this pack last year after noticing cracks in a lot of the vruzend plastic caps. Vruzend sent me a new version of the caps saying they changed the polymer to be stronger. So I rebuilt the pack this winter, now noticing the brand new caps to be cracked as well, the battery has not moved off the workbench. So there is obviously something wrong with the vruzend caps. I think I’m going to abandon them and switch to lipo packs since I just don’t have the time to figure out how to build a spot welded pack and I’d rather just get in the air.
So if anyone wants to buy almost brand new lghg2 cells let me know.
I appreciate your posting this followup, as I had wondered how well this worked. I retracted my bare “like” though, after realizing that might sound backwards… best of luck with the new setup.
This was an interesting thread - what did you end up doing, lipo?
Lipo’s yup. But do not like it. Batteries are fine but it’s complex, so many connections to make with four separate batteries.
Post some pics and info if you have time pls- -I am researching the batteries and connections methods, want to way all the pros and cons.
Cheers
Ever try eight?
I’ve bundled my batteries into two packs of four. I make the initial series connections for 12s on the bench when they come off the charger, and into the carrying case. That minimizes setup at the field. I also secure the loose cabling so all have to do at the field is hang the packs, strap them up, and plug them in. It’s still eight plugs through.
This winter I might build lithium battery (not with vruzend caps) as i’m not really happy with the lipo’s. Unless Openppg has plans to come out with lithium battery for the x4? @Pdwhite
Lipos work but they are cumbersome to attach/plug in. Also a pain to charge four separate batteries. I definitely had longer flight times with my 14s20p lithium ion pack vs 4x bonka 7s20ah batteries. Get about 22 min off the bonkas and I had about 35 min with the 14s20p lithium ion. Ideally Openppg would come out with nicely designed lithium ion pack as they did for the single prop version. Perhaps they can slightly modify the pack to work, for the higher amp draw. Have 4 connectors coming off the pack to lessen the load on connectors.
