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tiago asked

Mppt 100 /50 low voltage output in bulk


My MPPT 100/50 has been in use since a year. The voltage output in bulk - measured at the terminal on the charger - is constantly low. During the day the voltage rises slowly from, say, 12,4 to 13.6V while it should be a constant 14.3V or Thereabouts while in bulk. The panels deliver anywhere between 70-95 Volts. It seldom reaches absorption, let alone float.

Q: should the voltage in bulk be a constant ~14,3? Can unit be defective? (Manual says 14.3V in bulk...?)

Q: how can I adjust the settings so the output goes up to ~14.3 instead of <~13.5V

Kind regards


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1 Answer
wkirby avatar image
wkirby answered ·


The 14.3V setting is a target for the charger to reach. The battery Voltage has to rise as the battery charges. Once 14.3V is reached then the charger will go into Absorb phase. In absorb, the charger will try to maintain 14.3V for the set period of time. Try, because maybe there will not be enough sunshine or something like that.

It would be bad if the terminal Voltage was to rise up to the 14.3V very soon because this would mean that the ESR of the battery is getting high due to battery age or damage.

1) Battery Voltage rises slowly in the Bulk stage. The more charge power the quicker this will happen. It should be constant (within reason) in the Absorb stage.

2) No need to adjust any settings, it's working well. If you want faster charge then you need to add more charge power, more PV and if necessary another MPPT.

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tiago avatar image tiago commented ·

Thank you very much for your answer. If that’s the case, then why does an alternator on an inboard diesel put out a pretty much constant ~14.3V and an MPPT rises slowly depending on SOC?

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