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solarman3000 asked

High voltage, low amps from panels? High Amp pull on battery while charging?

I have a Mppt 100/50 and my charging amps have dropped down to a maximum of 7 or 8 amps when it used to get between 25-30 amps for 600watts of solar. I still get high voltage. My BMV is showing a current draw on the battery while the battery is being charged of up to 27 amps. No load is attached to the battery. This just started happening...before I was getting close to 30amps an hour charge from my panels.


My battery still charges to 100% but slower than before. After it is charged the current output on the battery slowly falls back to 0amps with no load connected. 816805fa-2404-43cd-9ca3-f9d2846ce89d.png

battery charging
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4 Answers
Ulrich avatar image
Ulrich answered ·

Every battery has a charging curve. First, the charging voltage must be higher than the battery voltage for current to flow into the battery. How much current flows depends in particular on the cable cross-section. If it is too low, the cable will get hot and not enough current will flow. When the voltage reaches a certain value, the current flow drops to zero when the battery is full.

This behavior is normal and can be easily viewed in the VRM portal. If you approve your installation, then I can take a look at it.

I hope I understood what you mean and my answer could help you a little.

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solarman3000 avatar image solarman3000 commented ·

I understand that the current will drop when the battery is at its fully charged voltage but what seems to be happening is the AMPs are going though the battery to the output without going in to the battery. The picture above shows charging from the solar with no load on the system.

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solarman3000 avatar image
solarman3000 answered ·

I understand that the current will drop when the battery is at its fully charged voltage but what seems to be happening is the AMPs are going though the battery to the output without going in to the battery. The picture above shows charging from the solar with no load on the system.

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marekp avatar image
marekp answered ·

At the moment of that screenshot your Smart Solar is getting 243W from panels (58.15V*4.2A=244.23W).

At the same time battery i being charged BULK with 17.3A, so your battery is taking 13.73V*17.30A=237.53W of energy.

The efficiency of this process is quite good at 97.26%.

Where do you see a problem?


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allswell avatar image allswell commented ·
Hey Marekp,


Thanks for those equations, could you please tell me how you worked out the efficiency equation? I'm looking to understand efficiency much better than I do now.

Thank you,

Kate

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marekp avatar image marekp allswell commented ·
@Allswell

Power-out / Power-in = efficiency

237.53 / 244.23 = 0.9726 = 97.26%

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allswell avatar image allswell marekp commented ·
Awesome, thank you.
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Ulrich avatar image
Ulrich answered ·

MPPT Solar Charge Controller:

1617044086689.pngBattery (SmartShunt):
1617044275269.png


This is my evaluation from today:

The battery was not full and was charged with everything the MPPT solar charge controller delivered until 12 noon. (You could see there were some clouds.) (Bulk)

The battery had its maximum voltage between 12 p.m. and 3 p.m. and was still charged with 1.4A. (Absorption)

From 3 p.m. the current flow decreased to 0.6A and the voltage was 13.5V. (Float)

At 6 p.m. the sun went down, the MPPT solar charge controller could no longer deliver electricity, since then the voltage has been falling again continuously.

You can find all data here: https://www.zoomsoft.de/grafana

I created this overview so that I can learn how it all works and what the effects are.

greetings



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