Think an automotive bulb or a few chained in series could bleed off the power relatively quickly if you have 4 bulbs that each can handle 12V normally operating then can handle 48V in total if chained in series since the voltage is divided I think… Is that wrong? If not would get like 80W of dissipated power as heat and light and for 480Wh battery could drain it in 6hrs or go to half voltage in 3hrs.
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Sorry can you clarify this for me? Are you saying i can discharge my battery by leaving it on with Metr Pro?? I’ve been wondering what I’m going to do to store my battery for the winter and this sounds like it may be the solution i need - got any more specifics on how this works?
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That’s what I use, works great.
1156 bulbs are dirt cheap, around 100 watts of drain out of 4 of them.
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Takes a couple days to kill batteries but it does the job. Used it on a couple puffy 4s lipos to safely dispose of.
Haven’t actually chucked 'em yet. They’re sitting at 0 volts so I still need to “short” the leads together and recycle them.
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Yes you can. Check the quoted thread for more info, there is a video link showing how it works. The discharger function is in the expert tab.
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My discharger.
- 4x 8ohm 100w resistor
- Therma glue
- Copper wire
- Big heatsink
- 2 fans at bottom
- 4x countersunk m5 screws as a “stand”
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I use one of the AliExpress 150 w programmable dischargers which have an endpoint voltage cut off
The caveat , they need a separate 12-volt input
So I grab an 80 volt 12 volt buck,. And wire that into the 12 volt input,. That way I only have one barrel plug going to the charge port on my skateboard
that way if I accidentally charge to 100%, and decide not to take that board, I can set the discharge to 42 volts and walk away
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You already have huge resistor in your skateboard – motor(s)!
Example of safely discharging in metr app with 14A motor current (which results in 0.52A battery current)
Keeping eye on the temps won’t do harm, but Metr Pro will stop discharging automatically if it gets too hot. Or when battery gets to desired level.
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hello,
howto discharge battery using foc_openloop under vesc tool ?
I mean which settings use ?
a screenshot would be helpfull 
Go to the terminal in the vesc tool.
Version 3.00 and below it’s on the left under “VESC Terminal”
Version 3.01 and above it’s on the left under “VESC Dev Tools”
Click the heartbeat and RT buttons on the right
Type foc_openloop 15 1000 to start with.
That’s 15 motor amps at 1,000 erpms (140 rpms actual).
Watch the temps on the real-time tab or stop and check the motor by hand if it doesn’t have temp sensors every minute or two. Raise / lower current as needed.
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awesome, working great.
can I up motor amps with same erpms safely ? always checking temp
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That command is often used for a load test to find how quickly the ESC will hit the thermal limits. RPMs have little effect on that test so usually they stay low while current is adjusted.
If you are trying to draw down the battery, you could increase RPMs which should ultimately increase the amps pulled from the battery. You can safely test just about any value. It will still follow all the eRPM and current limits you have set on the ESC. Play around with the values and check the realtime tab to see what combination draws down the battery the fastest while keeping temperatures in check. Share what you find so others looking to do the same have a good starting point!
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with my 12s4p p42a (16,8Ah) at ~ 49v, and flipsy 6384 (190Kv 4000W)
on only one motor only because my dual vesc has one channel dead.
Began with “foc_openloop 15 1000” to test,
then going up to 50amp (step by step) and drop rpm to 0
at foc_openloop 60 0 motor begin to hit 70°C in few minutes.
staying back a 50 amps with cycle of ~20minutes.
last cycle of ~45minutes - 1hour: here is screenshot:
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Interesting that 50A was the point that temps were stable. Looks like thats a true continous rating for that esc/motor combo.
Sooo, sorry for reviving this dead thing.
These are my voltages atm:
Not great, not terrible…
Would you guys say it’s reason enough to fully charge the pack and let the charger balance the groups (I believe my charger only balances at 100%) and then try this foc open loop thingy til 60-70% for winter storage?
I’m honestly a super noob when it comes to vesc tool and never dared to try it, I’ve been blessed with a functional non-blood unity from way back and have only been using the app.