dan avatar image
dan asked

Firmware update V1.42 causing different charging times

Since the last update V1.42 the charging seem wrong in particular bulk and absorption, the system is in standby mode in my truck. Previously I had bulk charging for quite a few hours and today I have absorption far to long. I dont know how to fix this.

Attached picks taken at 1.30pm.

MPPT Controllersbattery chargingfirmware update
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2 Answers
Mark avatar image
Mark answered ·

Its hard to tell whats going on without a proper data log.

As a first step could you please check your MPPT charge settings to ensure that adaptive absorption is active and the maximum absorption duration is set correctly?

But this is what I suspect is happening;

- With adaptive absorption active, each morning the MPPT will determine the correct amount of absorption required based on the battery voltage at the time of MPPT 'wake up' (as a portion of the maximum time specified, either 1/6th, 1/3rd, 2/3rd or the full maximum).

- However there has been an improvement/change in v1.42 where the 'intent' is to truly charge the batteries at the specified absorption voltage and for the specified duration REGARDLESS of solar or load conditions on the particular day.

- So for example, if your absorption voltage is set to 14.4v and your battery gets to this in the morning the MPPT will 'switch' to absorption phase. But if a little later there is not enough solar power to hold the battery voltage at exactly 14.4v and it drops to 14.0v for example - then the absorption timer with STOP COUNTING.

- When/if solar/load conditions improve later in the day and the absorption voltage is achieved again, then the timer will start counting down further until the FULL time duration is satisfied AT the correct absorption voltage. At which time the MPPT will then switch for FLOAT phase.

- It was decided that rather than the MPPT indicating that it has moved back into BULK phase when the absorption voltage can't be maintained (which could appear a bit crazy with the MPPT potentially toggling many times between absorption and bulk on some systems/days), the MPPT still indicates that it is in ABSORPTION phase (since that's the target) and the TOTAL time in absorption phase (both time at the absorption voltage and time below it) is reported in the daily history

- Accordingly the daily history of time in absorption can potentially be far greater than the absorption time specified. But this is only because the battery was NOT receiving the target absorption voltage during the additional time.

So maybe monitor the battery voltage on the next charge cycle to see if this is the cause behind the behavior that you have seen. And if it is then the real/best fix is to get some more solar power to ensure that the absorption voltage can be consistently maintained.

1568693081408.png (15.4 KiB)
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dan avatar image dan commented ·

I have a 110w panel fixed to the truck to keep the batterys charged, when I go camping the panel is combined with a folding panel connected in series about 56volts 8amps and 200w peak, I have plenty of solar then. Today is cloudy and what you say is more than likely correct, if I have weeks of cloud I will be in absorption for a long time.

Short of replacing my fixed panel for a bigger one or rather for two smaller in series I noticed that the specs on the battery absorbtion voltage is 14.2 - 14.4v I was thinking that while I'm at home and the batterys are in standby mode I could set the absorption to 14.2v which should help achieve float. Would this be okay to do try.

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dan avatar image dan commented ·

Also while I'm in standby mode could I reduce the maximum absorption time from 6hrs to 4hrs would this then give me 1/6 of 4hrs instead of 6hrs ie 40minutes absorption time or do we need to charge this hard everyday even in standby.

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Mark avatar image Mark ♦♦ dan commented ·

Your suggestions going forward all sound reasonable to me, but it's obviously up to yourself and/or your installer to determine what the best settings are for your setup and usage.

Also maybe consider using the new 'tail current' feature to end absorption phase 'early' based on the charge current dropping below the set tail current threshold. Typically this should be set to ~1% of your battery C20 capacity.

You can find this under the 'expert mode' settings;

But I would recommend to still try to have a full absorption duration about once a week, even if just operating in float state with no usage.

You could potentially even automate this by using the automatic equalization feature, but lowering the equalisation voltage to the absorption voltage, increasing the current limit to 100% and setting the occurrence frequency as desired...

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dan avatar image dan Mark ♦♦ commented ·

I was thinking the same thing with the equalization feature. Can the user defined (standby settings discussed) be saved so you can toggle between other presets, without re entering the values.

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dan avatar image dan dan commented ·

Scenario test

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Mark avatar image Mark ♦♦ dan commented ·

I see that your onto it now... :-)

Just be careful with those settings, only use if the battery is truly not being used / in standby and after a full charge cycle.

Yes you can save presets and easily switch between them;

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dan avatar image dan Mark ♦♦ commented ·

Thats great, I've always worried about charging everyday without using the batterys.

Thank you for your time.

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bigal avatar image bigal commented ·

Also, if the SC is being used with GEL batteries shouldn't equalisation be disabled?

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Mark avatar image Mark ♦♦ bigal commented ·

By SC, I assume that you mean 'solar controller'?

What Dan had just setup is not 'really' equalization - he is just using the feature to program in an absorption charge cycle once a week while the batteries are not being used / in standby.

The equalisation voltage has been lowered to the recommend absorption voltage.

The battery doesn't know or care what a charge phase is 'called', but it does care about the charge voltage, current and duration.

In saying that - yes, the equalization feature must always be used with caution and only if you fully understand the implications of the configuration.

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bigal avatar image
bigal answered ·

With 1.42 does the SC get any information from a BMV712 about what current is really going into the batteries?

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Mark avatar image Mark ♦♦ commented ·

No FW v1.42 only uses its own output/charge current as the tail current reference.

But using the BMV current as the reference for tail current is under development and currently being tested...

That way any charge current going directly to loads will be accounted for when deciding when to end the absorption phase based on tail current.

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