Lead length for LIPOs in series

[Phill Tadman]

Hi all,

I understand that battery to ESC lead lengths should be kept short (less than 20cm).

If you connect LIPOs in series (eg to make an 8S pack from 2 * 4S) does this need to be taken into consideration for the total lead length?

Phill

[simon_t]

No, it shouldn’t be significant if the wire/connectors are appropriate for the maximum current. If you know the gauge of wire you can check volt drops at maximum current, and if concerned go another size up in wire. A decent ESC should have good reservoir capacitors and filtering on the input - cheap ones might be more sensitive to pickup on long wires.

Simon

[Trevor]

My recollection is that the concern over length of battery wires was less to do with voltage drop and more about the magnitude of induced voltage spikes that could damage the capacitor on the input to the ESC - hence why some recommended the use of decoupling capacitors at intervals along a long lead.

That said, I haven't heard any reports of damage from over-long battery leads for ten years or more so it's maybe not as big a problem nowadays with modern ESCs.

[Phill Tadman]

Thanks guys,

Yes, I’m more concerned about voltage spikes and induction that fry the ESC capacitors.

I’ve got a spare Jet Addcap so I’ll add that to be on the safe side.

Phill

[Peter Balcombe]

Phil,
The potential issue is the inductive impact of the extra wire length on the ESC battery input, which can cause the ESC to fail.
The rule of thumb seems to be to add low 470uF (low ESR capacitors) as close as possible to the ESC for every extra 100mm length of added wire.
See this link for info: https://www.radiocontrolinfo.com/how-to ... correctly/

You may be able to get away without any capacitors depending on the particular ESC, but you may not!
Peter

[Elliot Howells]

I've never had issue with battery wire length until now, fitted an EDF in the fuz of a glider with the batteries/ ballast up front, I've used an additional capacitor board from YGE because the ESC is mounted underneath the EDF to cool it in airflow.

I questioned the size of the caps on the new frsky neuron ESC's, they appear to be very small, no issues reported however, so go figure.

Ell.