But as I said two weeks ago. They switch into ECO far too early and it is a software issue and not a hardware issue. I think because they try to reduce service claims or want to extend the range by that so that they come closer to the range they advertise. And they don’t have the VESCs feature to reduce the power only when necessary by voltage cutoff start and end.
What I meant is 3.4V is not 20% left if you discharge to 2.8V. You can sag from 4.1V down to 3.4 V if you go up to 20A/cell. Or from 3.8V if you do 10A/cell. What is the empty voltage?? I think they are leaving too much energy on the table but that still doesn’t mean is not a battery issue.
@Ackmaniac, whether they relax the limits or not. Voltage drop is instantaneous and that can only be fixed by a better cell. Look at the curves… its all right there.
What I mean is when they switch to eco when the cell is below 3.4V under load then they do it too early. When the cell is at 3.4V without load then I guess they show already 0%.
Huge thanks to jpark13b from the Evolve forums because he made a graph showing how the curve works for the Evolve board. This should help us a lot:
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3.4V no load would show the SAME percentage as 3.4V under load. They’re going by the voltage. They dont care whether its under load or not. That is why voltage sag is an issue
What I mean is that when they reach 3.4V under a lets say 15A a cell load then the remote thinks that it is at below 20% without load because it’s not smart enough. So in a load moment they detect that the voltage is low and think they have no load. So they switch the mode.
No. When they are at 3.4V their controller simply thinks it’s at 3.4V, it does not care about no load voltage and neither should you.
Unless you know discharge curves for every load condition, you cannot make a controller that is “smart enough”. You cannot say ignore the voltage while we’re drawing XX amps because that is literally how you would damage them.
Their curve could be pulled lower by about .2V/cell but that would still not fix the problem just delay it slightly further.
This is literally part of my job description. To come up with battery discharge models that are accurate whether you draw no load or 20A/cell so that we can have an accurate battery indicator during all flight conditions for military UAVs
Trust me, it is not a trivial task.
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Then would someone know how much it would cost to build a pack out of VTC6 cells that effectively eliminate voltage sag and have the necessary connectors to connect with the existing BMS+ESC combo?
$400 if you DIY. Someone else will probably charge up to $600 based on the markups on 25Rs. $300 for the cells alone at Liionwholesale + 100ish bucks in wiring and stuff.
I don’t have the materials nor experience to work with batteries so someone else would have to do it. Would that be $600 to make a battery that’s plug and play? I’d like it to be as easy as following this video:
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It is possible because the vesc is doing that. When you adjust the cutoff start to 3.0V and the cutoff end to 2.8V then it starts to reduce the power output when it reaches 3.0V and doesn’t go below 2.8V.
So if the Battery can output 3.0V at 15A and we only draw 15A then there is no reduction. When we try to draw 20A then the we would go below 3.0V so it starts to reduce the power so that we end up somewhere between 3.0V and 2.8V which would result in something between 15A and 20A. It doesn’t switch the mode. It only takes care that you stay in that range.
Mellow is doing that with their BMS: “It’s not all about protecting and preserving: bad battery management impacts fun riding as well. Two huge issues affect almost every e-skate on the market today, even the pricier models: “false low capacity shutdown” after hill climbing due to voltage sag and “brake shutdown” due to inability to use regen brakes on a full battery.Mellow is unique in having eliminated both. The BMS uses triple fuel gauge measurements (voltage, Coulomb counting, Impedance TrackTM) to accurately read battery level and eliminate false readings.”
Mellow is actually really interesting. They seem to have the best tech out of any eSk8 available right now. Something that interested me about their system was the “Endless Ride: Acceleration 10% (pushing with cruise control)”. I wonder if this means whatever speed you kick the board to, the board will keep its speed, or if the board has a max speed you kick up to.
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Guys I just made a thread. I feel like you guys would know best as a lot of you seem to be extremely knowledgeable in the topic. I’d love your opinions, thanks!
hey ! I was about to put replace the battery with 18650 to double the range in AT of my friends GT Bamboo. any recommendations? Are these BMS with switch / UART plug available somewhere ? I could still try to keep the BMS and just plug into a big 18650 pack.
You have to take the BMS from the original battery and use that. Otherwise it won’t work. Evolve also doesn’t sell the BMS separately. But after you take the BMS, you can just make a normal 10s pack and it should work fine.
board has bad range… I have one and it gets me 20miles tops in fast and eco the rest of the remaining 3-5
gts are lipo pouch cells not 18650s. i dont think you have opened your board at all have you mate? they are 10 x 10Ah batterys in series.
LiPo pouches are the same tech as li-ion. People just use li-ion to describe cylinder cell batteries, so saying they’re pouches but are li-ion, while technically correct, is not common nomenclature