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mlsadler avatar image
mlsadler asked

SmartSolar Charger MPPT 150/80 skips Absorption and goes direct to Float from Bulk

My solar system consists of the following setup

Victron Color Monitor GX firmware V2.42, Multiplus 48/5000/70-100 firmware 413, Battery Monitor BMV-712 smart firmware V4.03 charged voltage 55.4V, smartsolar charger MPPT 150/85 rev2 firmware v1.47 absorption voltage 55.7V float voltage 55.4V, a battery bank of 24 maintenance free batteries each 2V with the following specs Float 2.23-2.25V Boost 2.30-2.32V Current 60 to 120Amps, 18 Solarworld panels each 290W

The challenge am facing is over night the batteries discharge up to 75% and when the sun rises, the batteries charge up to 90% and the charge controller moves from bulk direct to float and skips absorption stage so the batteries don't get fully charged they only charge up to 95% with full 8 sun hours, what could be the problem with my solar solution

MPPT Controllers
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3 Answers
Murray van Graan avatar image
Murray van Graan answered ·

Hi @mlsadler. Are you running ESS? If yes, the CCGX takes control of the charging based on what was programmed into the Multi. Let us know

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mlsadler avatar image mlsadler commented ·

I am not running ESS, but what is funny is that when i switch off the breaker between the MPPT and the batteries and then between the PV combiner box and the MPPT and then turn them back on one at a time starting with the battery breaker, the MPPT immediately moves from bulk to absorption and the batteries get more charge probably to 99%

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Mark avatar image
Mark answered ·

Check the MPPT configuration for 'tail current' under the 'expert mode' settings.

It could be that the charge current is under the tail current threshold when the absorption voltage is reached.

Also check what settings you have in the CCGX in the DVCC menu - Check if DVCC and SCS (shared current sense) is active - in which case the MPPT will reference the BMV measured current against the tail current threshold.

Lastly your Multiplus FW is very old and may have some relation if DVCC is used. It would be good to update to the latest FW.

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mlsadler avatar image mlsadler commented ·

The MPPT tail current is 2A,

Today at the point when the MPPT switches from Bulk to Float these are the readings obtained from VRM

Solar Charger PV current 29.5

Solar Charger PV voltage 110.23

Solar Charger current 0.3

Solar Charger voltage 55.25

SOC 86.4%

Yesterday at the point when the MPPT switches from Bulk to Float these are the readings obtained from VRM

Solar Charger PV current 26.3

Solar Charger PV voltage 93.91

Solar Charger current 41.9

Solar Charger voltage 57.75

SOC 84.7%

In the CCGX settings DVCC is inactive its not configured

Lastly is it possible to update the multiplus FW if i don't have an MK2 USB?


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Mark avatar image Mark ♦♦ mlsadler commented ·

Yes it seems to not be related to the tail current threshold being satisfied, strange indeed.

PS. With the numbers you reported from today, the 0.3A charge current looks to be a typo/incorrect (it should be about 60A at that PV voltage/current) - can you confirm?

Could you please post some screen images of your full MPPT settings with the 'expert mode' option enabled?

Also could you post some screen images of the VRM log for MPPT PV voltage/current, MPPT charge voltage/current and BMV voltage/current - they might offer some more clues.

Regarding update of the Multiplus FW, unfortunately that needs to be done on site with a MK3 to USB interface. But if DVCC is totally disabled then I doubt that's related.


What kind of batteries are you using and do you have a link to the spec sheet?

I ask because your absorption voltage (55.7v) seems very low for a lead acid based battery and it's also very close to the float voltage (55.4v) - which seems a touch high...

Independent to the voltages being a bit odd to me, maybe the fact that they are so close together (only 0.3v delta) is causing the MPPT to play up. Try to increase the delta between the voltage set points and see if it makes a difference.

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Mark avatar image
Mark answered ·

OK - based on the MPPT state plot over 24h, I am now almost certain that I know what the issue is...

For some reason your MPPT is not turning OFF overnight so it's still working on the absorption phase timer from the last day that it completed a proper reset.

For it to turn OFF and reset the PV voltage needs to fall below battery voltage at night and for some unusual reason that this is not happening with your setup.

Please also provide the plot of PV voltage over a recent 48h/2 day period to confirm this.

Also please confirm if your solar panels are somehow receiving light during the night - such as from external overhead lighting.

And out of interest, where is this setup installed - boat? home?


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mlsadler avatar image mlsadler commented ·

Please check this out you have a point

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klim8skeptic avatar image klim8skeptic ♦ mlsadler commented ·

That is interesting.

I built my camper under a street light, and always saw pv voltage just below the battery voltage at night.

The 100-50 never failed to properly sort the days out though, was about v1.39 for about 3 months.

Expand a small overnight portion to see what pv current is available/produced.

Clue?

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mlsadler avatar image mlsadler klim8skeptic ♦ commented ·

I have no light on the panels at night just that am connecting 3 panels in series with 6 strings in parallel, the current over night reads 0 but the PV voltage is higher than the battery voltage

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klim8skeptic avatar image klim8skeptic ♦ mlsadler commented ·

No light at night!

Does the reducing (lower) pv voltage match your battery discharge voltage?

What model panels?

Any special pv earthing requirements?

Cluthing at straws!

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mlsadler avatar image mlsadler klim8skeptic ♦ commented ·

Does the reducing (lower) pv voltage match your battery discharge voltage? I dont seem to get this well

The panel model is solar world 290W each a total of 18 panels

What kind of earthing is required coz I remember we did earthing in the PV combiner box

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mlsadler avatar image mlsadler klim8skeptic ♦ commented ·

These are readings from 02/02/20 20:00 to 03/02/20 07:00

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mlsadler avatar image mlsadler commented ·

Battery voltage

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Mark avatar image Mark ♦♦ mlsadler commented ·

Well that's the reason for your short/no absorption time issue...

But if you have no strong overhead lighting that could be causing the PV array to generate some voltage then you have some kind of issue with your wiring OR your MPPT unit.

Next step I would recommend is to;

1- Measure the PV voltage directly at the MPPT PV terminals at night using a multi-meter to see if it aligns with the MPPT reported PV voltage

2- Physically disconnect the PV array wiring directly at the MPPT PV terminals at night to see if the reported PV voltage drops to ~0V

These quick tests should help to indicate if you have a weird wiring issue or an issue with your MPPT unit.

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mlsadler avatar image mlsadler Mark ♦♦ commented ·

When I Physically disconnect the PV array wiring directly at the MPPT PV terminals at night still the MPPT reads a voltage almost equal the battery terminal voltage yet when I measure the PV voltage direct on its wires it reads 0V, why does the MPPT register a voltage reading even when the PV array terminals are disconnected from it? Remember am using a victron smartsolar charge controller 150/85

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Mark avatar image Mark ♦♦ mlsadler commented ·

Based on your tests and response it seems that your MPPT has a fault, possibly some kind of internal short circuit between the input and output.

Best to contact your Victron dealer/place of purchase or installer, explain the behaviour and get the unit tested/sent for repair.


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mlsadler avatar image mlsadler Mark ♦♦ commented ·

Ok thanks let me make a follow up over that issue



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mlsadler avatar image mlsadler Mark ♦♦ commented ·

Hello was able to acquire a new Victron MPPT 150|100 and it worked well for a week, the charging would go through all the three stages but for days now it charges batteries fully to 100% soc in absorption and stays in absorption all the time it never gets into float and you see the batteries are still taking in much current what now could be the issue?

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JohnC avatar image JohnC ♦ mlsadler commented ·

Good you seem to have sorted your first issue. But this one is different, so probably best to start a new question.

And consider too that "100% SOC" and "taking in much current" are mutually exclusive. Unless they're getting hot, it's not possible. So please try to quantify these things as much as you can.

My first thought is that your SOC calcs are incorrectly set up.

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