Human Instrumentality Project | 6s3p | Single Racerstar 140KV 5065 | Custom Deck | Battery box holder | FVT 120A ESC

Yeah, i thought that the battery holders would cause more problems but until now they work pretty good.

The charging issue thems also to being solved. It was just like @rojitor said

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If you wanted to improve the performance you could try this one?

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Yeah sadly i had already ordered as someone told me about a higher kv with a 6s setup but i’ll think about it again thx m8. This motor has a really great price.

Do you know how voltage sag will accure with a motor with more kv ? Same or worse ?

Sorry I am not sure on this. I think I may get one of these to try and make a board for the kids though.

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Hi guys,

as i already mentioned before voltage sag is kinda a bigger deal on my setup and i want to overcome the problem at least a little. But at first i would like to understand the problem. And have several questions on this topic.

  1. What does voltage sag cause ?

2 .How do i overcome/avoid it ?

3 . Does it damage my cells if the V of my system sags under 3.3V (per cell) under usage but stays at 3.8V in idle ?

My battery usally sags betwen 25% - 40% at full throttle so i can only use until 55% charge at idle

So my plan is now to upgrade my battery to 6s5p. I would really appreciate any help.

You won’t like, but I think most of the sag is because of the battery holder, the contact resistance is high and a lot of power may be lost there

Did you manage to fell if the contacts are hot? If not do some hard accelerations and braking and immediately open the enclosure, remove one cell and see how warm it fells

The 30Q is a very good cell, you have most sag than most because your ESC doesn’t limit the current like a VESC, so you may be drawing more than 100A for a short period

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Yeah i read about that but was hoping to not be a big of a deal but it thems like it is indeed a big deal.

After every ride a had a close look to the temperature of Esc, Battery and motor and the motor was the only thing that got like handwarm, maybe 40-50° celsius.

I´ll test the contacts and see what i got.

This is something i don´t understand why does my Esc draw up to 100A even my motor only draws 36A max ? from what i understand 100A discharge would´nt be that good for my batteries :frowning:

36A is what’s the manufacturer decided to rate the motor, but nothing prevents it from drawing more when a high load is placed, which is the case when starting from slow speed

Yes, this high current is bad for the batteries, that’s why most people here will say that going cheap in the long run will be more expensive, you saved a little bit of money found with an FVT esc, but maybe because you can’t limit the current you will kill the batteries way faster than expected

But for now, you could measure you’re entire pack internal resistance, this way we can see where the problem is

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Wow, thats bad news and yeah some ppl. stated that some parts of my build were not that good but i never understood why. Now i see whats the problem and i’m very thankfull for that advise m8.

So my next step will be finding out how to messure the internal resistance and then hopefully get a not so pricy vesc and spotwelder.

Just get a few ceramic resistors, a 5 ohm one will pul about 4A from the battery at 22v

Knowing the rest voltage, the voltage under the resistor load and the precise resistor resistance, measured with a multimeter we can easily measure the internal resistance, is not the most precise method, but will give some idea if something is really odd, for example if the battery holders have a tô high contact resistance

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So if i have to buy some resisstors anyway which would cost about 5$ at least shouldnt i buy an internal ressistant messure tester if they can do what i think they can? i saw some on amazon for like 10 bucks, also isint my multimeter capable to do this for me it has ?

Sorry for the question im havent worked with electric that much yet.

You may also be drawing more power than needed due to the 140kv motor on 6s. Especially if you are riding at max speed quite often. A higher kv motor on 6s could possibly give you less current draw at speed(but more current draw during acceleration)

how is that motor mount holding up?

On another note: the board looks great dude. I love the enclosure.

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Yeah @Pedrodemio mentioned that already and i will defenitly get a vesc very soonish but at first i want to get rid of this battery holders first by getting a spot welder, its pricy but this wont be my last build thats for sure.

And also i would really like to meassure its internal resistance before i build a new pack so i can compare it and see how good these holders does their job, it could be helpfull for others who also dont have a spot welder.

The motor mount does a pretty good job compared to its cost, had to Tweak it a little but now everything fits tight.

And thx m8 i put a lot of effort into this deck and enclosure, still not happy with it but thats another story :rofl:

So how has your board been. I’m looking at the racerstars as motors for my first build

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Pretty good even if i actually drove it only like 6 times, but it was great fun. Anyway something thems to damage my Battery (possible the Esc and or Battery holder) which is the reason, i stoped riding it for now.

I´m now in the process of upgrading my garage with a Diy Spot welder and upgrade my setup to a Vesc and probably a 10s4p pack. But if you are aksing about the motor, imo it works pretty solid at 6s with a 15 to 36 gear ratio but many ppl. suggested to go for the 200kv version with 6s.

I was looking at 10s2p and was looking at either the 140 or 200

Then i guess its all about which top speeds you want to achieve, from what i see 140 kv should give you at least 20 mph. Which is already pretty fast. Don’t know if u have already checked this calculator out.

yeah I have looked at it with a 16/36 ratio 10s 80mm wheels and a 200kv motor max weighted speed is 24.65 that would be plenty considering that is the speed on most city roads and I will probably never go that fast.

Nice build! I was also thinking about the 5GT motorpulley but I thought it was a different profile as HTD5M. Does the motormount holes fit thr motor holes? It looks like you’ve only used 2 screw or am I wrong?

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No, you are Kinda right. I had to customize my motormount, which was´nt fun because i don´t have prober tools for this kind of work and use now 3 screws but it´s tight and had made no more problems, yet…

25 Mph sounds good imo, but i am from germany where we are only alowed to drive 6kph legaly so take my opinion with caution :smiley: