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Thank you for the great forum, Safe Driving over the weekend. Sincerely Jason
weber

Axpert kettle voltage-sag data request

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We don't use the compensated voltage when checking for overvoltage, but of course a similar problem can occur on undervoltage. If you've set the compensation strength too high, a high load current will make the inverter think the state of charge (based on voltage) is higher than it really is. But in the case of lithiums, the BMS will save you. It doesn't make a lot of difference whether it's the inverter or the BMS that cuts you off.

I've just updated the AussieView manual to become the AussieView and KettleKomp manual. Here are the parts related to KettleKomp. Criticism gratefully received.

KettleKomp Manual extracts.txt

 

Edited by weber

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This shows both true and compensated (with the flashing "k") battery voltage, while boiling the kettle.

BattVk.jpg.7360c274166c9fee842986be1787c89f.jpg

 

This shows how we piggy-backed the setting of compensation strength on the cut-off voltage setting.

Cutk.jpg.59470fbba3ddd29d9018f7b2b7f5332b.jpg

Edited by weber

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On 2018/11/21 at 9:40 AM, weber said:

As Coulomb mentioned, we have been working on a set of firmware patches to address the "kettle cut-off" or "premature source switching" problem. He also mentioned that we had a major setback when we bricked an inverter in the process. But as of today, I am testing the first working non-bricking development version (YF1_73.00e). Hoorah! But there are some aspects of it that I'd like to run past you gentlemen.

First, we can't decide whether to call this feature KettleKomp™ or AussieBrew™? ;)

Second, we're not sure how well it is going to work on all the many and varied Axpert systems out there. The math challenged can skip the fine print below.

We currently calculate:

voltage_threshold_compensation = battery_current * guestimated_internal_resistance

where

guestimated_internal_resistance = k * (absorb_voltage_setting[26] - float_voltage_setting[27]) / max_total_charge_current_setting[2].

where k is a constant. I tried k = 1 and it was too low, at least for my system. I'm now trying k = 2.

When there are parallel or phased machines, battery_current and max_total_charge_current_setting[2] are summed over all machines.

We're trying to avoid having to provide a user interface to allow setting the internal resistance, as this would be very difficult. This formula is based on the idea that at least some part of the difference between absorb and float voltage settings is due to the internal resistance of the battery causing voltage rise at the maximum charging current.

 

We're asking axpert owners to help us by telling us how many volts (including tenths of a volt) your battery sags by, when you turn on your kettle (or other heavy load); what battery current your kettle draws; and what your values are for settings [26], [27] and [2] (the latter summed over all machines).

 

Will this work on the Ifinisolar inverters as well?

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