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tudordewolf

Shortening battery wires as an upgrade/precaution?

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This forum post has a ton of researched information and links about the interaction between a battery, ESC, and motor, particularly the role of the power-filter capacitors. The takeaway is that shortening the battery wires will always be better for the longevity of the electronics, as well as potentially improving performance.

 

I may be wrong about this next part, but I also think that most EUC's would benefit from larger power capacitors (in the range of 4700-10,000uF; as opposed to the ~2,000uF found in most) I expect it would be better for the batteries to experience less "stutter" between charging and discharging while the unicycle starts and stops, and that the added buffer of power could actually help it handle bumps better, by providing an extra 10-15 amps in parallel with the battery pack. It'd also be important to pick capacitors with a low ESR or they won't be able to make use of their capacity. I'm considering adding a couple more on to my msuper v2, just on top of the ones already installed. Fortunately the roomy electronics compartments lends itself to this, compared to more "packed" unicycles.

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On 10/1/2017 at 3:51 PM, tudordewolf said:

This forum post has a ton of researched information and links about the interaction between a battery, ESC, and motor, particularly the role of the power-filter capacitors. The takeaway is that shortening the battery wires will always be better for the longevity of the electronics, as well as potentially improving performance.

 

I may be wrong about this next part, but I also think that most EUC's would benefit from larger power capacitors (in the range of 4700-10,000uF; as opposed to the ~2,000uF found in most) I expect it would be better for the batteries to experience less "stutter" between charging and discharging while the unicycle starts and stops, and that the added buffer of power could actually help it handle bumps better, by providing an extra 10-15 amps in parallel with the battery pack. It'd also be important to pick capacitors with a low ESR or they won't be able to make use of their capacity. I'm considering adding a couple more on to my msuper v2, just on top of the ones already installed. Fortunately the roomy electronics compartments lends itself to this, compared to more "packed" unicycles.

Late to the party... the idea of adding more bypass capacitance seems like a sound idea to me (but I'm just a hobbyist in electronics). However, 4700-10000uF capacitors with the voltage rating required for the EUCs (>=100V to account for the possible voltage spikes, and I think the next "standard" value after 63V is 100V anyway) might be hard to fit inside the compartments or on the board. If space allows, adding more but smaller capacitors in parallel might work, also the total ESR will then be lower as it's paralleled resistances of all the capacitors. Another issue is that the inrush current will be higher/longer lasting the more capacitance and/or less ESR you have when the caps are discharged and you connect the battery, so anti-spark connectors should also be considered. 

Edited by esaj

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6 hours ago, esaj said:

Late to the party... the idea of adding more bypass capacitance seems like a sound idea to me (but I'm just a hobbyist in electronics). However, 4700-10000uF capacitors with the voltage rating required for the EUCs (>=100V to account for the possible voltage spikes, and I think the next "standard" value after 63V is 100V anyway) might be hard to fit inside the compartments or on the board. If space allows, adding more but smaller capacitors in parallel might work, also the total ESR will then be lower as it's paralleled resistances of all the capacitors. Another issue is that the inrush current will be higher/longer lasting the more capacitance and/or less ESR you have when the caps are discharged and you connect the battery, so anti-spark connectors should also be considered. 

I did have trouble fitting just the 2x 1000uf caps for a KS-14C. The Msuper V2 has a compartment large enough for a 16-cell battery dedicated to the circuit board, which leaves plenty of room. For the record, they were 80V caps which I felt comfortable using on a 67V system (the originals were rated for 80V) and cost a little under $20 for 10 of them shipped from mouser electronics.

Though its a risky trade-off, the more capacitance you have, the less you'll have to worry about voltage spikes and therefore not need as high-rated capacitors.

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