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SPD3303X-E Imbalanced current draw between channels in parallel mode



I'm trying to troubleshoot an issue with my SPD3303X-E (hacked to SPD3303X) power supply when running in parallel mode. In parallel mode the current draw from channels 1 and 2 are imbalanced. The unit will draw most current from CH1 up until CH1 hits the 3.2 A limit. Then further current draw will be supplied from CH2.

I'm unable to get a full 6.4 A out of the unit (i.e. 3.2 A per channel) in this mode. The voltage collapses around 6.2 A total draw. Individually I can get a full 3.2 A on each channel in regular mode.

If I manually wire channels 1 & 2 in parallel and operate them independently I see similar current imbalance.

I can get up to 6.4 A total current though.

I found a video on YT where someone with the same unit sees equal distribution of current between the channels. Is the current imbalance between channels normal or an issue with my unit perhaps?

My unit is hardware version V3.0 and software which seems to be the latest for this hw rev. I've been testing connected to a DC electronic load.

My SPD3303X has similar behavior. In "parallel mode", I "help" with such jumpers:

Maybe the relay has problems with increased contact resistance and needs to be replaced, worth checking.

My guess is, that internally both channels still run independent, just a relay birding them.
So if one channel is set a few millivolts higher ...


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