question

samso avatar image
samso asked

System seems to be charging slower than it should from MPPT

This question may be basic or just not needed, I'm not totally sure. It feels like my solar system is charging the battery at a much slower rate than it should. In the last 2 hours I've brought in between 200-300w consistently and my battery SOC has rose by about .6% in total with only a 20w load during that period.

My system is as follows:

3x 150w panels in parallel

Victron 100/50 MPPT

2x 12v 100ah Battleborn Lithium Batteries

Victron BMW 712

I'll add a few screenshots from the victron app for the MPPT and the BMV. Hoping someone can either tell me everything is fine, or there is a problem somewhere.

The only thing I can notice is odd is the MPPT claims there has only been 1 charge cycle to date.(system has been in for 3 months) however it is in bulk mode just fine. It just seems like not enough power is making it to the battery, I may be wrong, I'm not an expert at all on this.

Thanks ahead of time for the help, I can supply more pics of settings etc if needed.

mppt charging
screenshot-20200324-135318.jpg (297.1 KiB)
screenshot-20200324-135331.jpg (281.0 KiB)
screenshot-20200324-135345.jpg (355.2 KiB)
screenshot-20200324-135331.jpg (281.0 KiB)
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samso avatar image samso commented ·


Heres another screen shot from the BMV

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screenshot-20200324-140903.jpg (422.7 KiB)
2 Answers
Guy Stewart (Victron Community Manager) avatar image
Guy Stewart (Victron Community Manager) answered ·

Hi @Samso,

There is an issue with your system wiring. The PV array is connected in parallel. This means the PV array voltage is only 2V above the battery voltage.

This is not enough PV Voltage for an efficient charge from an MPPT.

Making any changes can lead to damage to your system including destruction of your MPPT, so please be careful.

I would not advise making the changes to the PV wiring without first understanding the maximum open circuit PV voltage of your array at the lowest possible temperature in your area, and the maximum PV input voltage limit of your MPPT.

Once you understand these, or find a suitably qualified installer to help you, then your system should be able to be reconfigured to improve performance.

A good next step would be to read the solar panels section of Victron's Wiring Unlimited - https://www.victronenergy.com/upload/documents/Wiring-Unlimited-EN.pdf

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samso avatar image
samso answered ·

Thank you for your help, that makes a lot of sense. That pdf is very helpful as well. So correct me if my thinking is wrong here, but reconnecting my panels in series instead of parallel would solve the problem? That would create a much higher pv voltage and lower amps. The MPPT can handle the max open circuit voltage of the array fine in series. The wire to the controller should also be fine to handle it.

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