Blacktip DPV Battery

[Addison Snyder]

I'm building a custom battery pack (inspired by this) for my Blacktip Tec, equivalent to 2x20Ah (in series) dewalt batteries in its vanilla configuration. So output nominal voltage should be somewhere around 40v. For anyone familiar with the Blacktip, do you know what the 3rd blue line is for and how I would adapt my soon-to-be single big battery to use it? My assumption was that it was the in-between to detect battery imbalances between both dewalts, but the numbers I'm reading disprove that. When I've got two regular batteries in, the positive/negative voltage is 40.5v, and the positive/tertiary voltage is... 39.0v, not the ~20v I was expecting! The tertiary line connects to a chip that says VSENSE, and that line is consistently 1.35v even when there is only a single battery hooked up. It also still outputs, even if the fuse is removed. So I guess I'm wondering how I should proceed. Does anyone know what the use is for this line?

 

[Addison Snyder]

Tiny update, if the blue isn't connected into the DPV, it still runs. It also doesn't _seem_ to detect that it's out of water because it will go to full speed. Normally it will realize there is no physical resistance to the blade and will be locked to a slow speed. Not sure if that's correlated, but just thought I'd share that finding.
Other theories about the line include:

• Some form of temperature sensor?
• Super basic way to test if the fuse broke?
• Low voltage for the DPV computer only (though everything seems functional without it)?

 

[macado]

You can disable the blue wire in the firmware if you want. If I recall all it does is measure the balance between the two batteries. It does nothing else. The default value here is 14
Set $x to 0 in VESC Tools. If you don't connect blue wire and then set ($x) imbalance to zero then you'll always get full 4 bars on the display

See guide here: https://dive-xtras.zendesk.com/hc/e...310802094996/BlackTip_Pocket_Guide_v1.19F.pdf

Depending on what VESC controller you have I guess the newer ones dont come with a USB adapter so you'll need to connect your own micro-USB adapter to the VESC controller in the tail section. The older controllers had this included.

The scooter will run completely fine without it as mine as been turned off over a year. If you dont do this you'll get a imbalance error when the voltage eventually gets lower.

This is not my drawing (it was done by a friend of mine that built one of my batteries) but this is how you can setup the blue wire if you want the battery display to work otherwise you need to disable it in the firmware.

 

[Addison Snyder]

Thanks, you're a hero! I'll probably disable it like you said because I'm dealing with a single battery unit (well, 5Sx2S, each with a BMS). I'm lucky and have an older model with the USB still there. I guess I don't understand how the blue line indicates a battery imbalance on a conceptual level because of what I've observed. Does 1.35v indicate there _is_ an imbalance? What kind of voltage does that range from? It's super strange to me that I get 1.35v with or without the second battery in place (so a ~20v difference).

 

[Addison Snyder]

You can disable the blue wire in the firmware if you want. If I recall all it does is measure the balance between the two batteries. It does nothing else. The default value here is 14
Set $x to 0 in VESC Tools. If you don't connect blue wire and then set ($x) imbalance to zero then you'll always get full 4 bars on the display

Found out that my firmware won't accept 0. Says that it's out of range, and states that the range is 10-20 or something like that.

 

[Addison Snyder]

Running a little simulation. I guess the blue line just cranks down the voltage on the first pack and the DPV infers the 1st pack true voltage from there, before comparing to the total voltage of both packs. Seems kinda strange to me in how it's designed but writing it out helped me figure it out conceptually. I'm not exactly great at this.. seeing schematics makes better sense to me. Note: the resistor values were changed in the simulation, I'm comparing the values to that of what I have currently and maaaayybe my DPV has 3x47k resistors, because the numbers are pretty spot-on to either battery I put in. If I stay with 22-47-22 I get something like 2v coming out of blue.

 

[macado]

Found out that my firmware won't accept 0. Says that it's out of range, and states that the range is 10-20 or something like that.

Hmm I can double check my firmware settings in a bit but maybe they changed what values it will except. I'm pretty sure I set $x to 0.

What version firmware is your scooter running?

You could also try loading the third barty firmware
GitHub - bwoodill/BT_VESC: VESC firmware for Blacktip DPV with added features. This firmware allows current levels to be set higher than recommended by the manufacturer which could result in damage to the motor. Please be careful if increasing limits

 

[Addison Snyder]

Looking at it connected to VESC shows that it is 4.1 firmware with '410' hardware.
Update: fiddled around with it for a bit, loaded (vanilla) firmware 1.18 (sadly I lost what version was preloaded on it) and can now successfully set $x to 0. I did so and confirmed that the battery mismatch symbol no longer appears when the blue line is disconnected. So I can now just make a battery that connects directly without having to work around the DPV trying to micromanage it! Once again thank you for your assistance!

 

[Scubasteve1984]

Looking at it connected to VESC shows that it is 4.1 firmware with '410' hardware.
Update: fiddled around with it for a bit, loaded (vanilla) firmware 1.18 (sadly I lost what version was preloaded on it) and can now successfully set $x to 0. I did so and confirmed that the battery mismatch symbol no longer appears when the blue line is disconnected. So I can now just make a battery that connects directly without having to work around the DPV trying to micromanage it! Once again thank you for your assistance!

Were you able to see the battery level on the display after this?

 

[Addison Snyder]

Were you able to see the battery level on the display after this?

Good question.. I don't think so, then again I haven't really ran the DPV down below 68% (according to the BMS), and I try to store it at ~70%. Running stock firmware, with only the battery balancing setting tweaked. I'm going to start changing stuff out with time. I can tell you that I went to Ginnie Springs' Henkel (roughly 3200ft penetration) and back using like 20% or something pretty low, and that the battery is doing well so far.