Smart MPPT 100/20 BT Charge Controller Stop-Start Charging

Question

question

springgrove asked Dec 31, '22

Smart MPPT 100/20 BT Charge Controller Stop-Start Charging

Hi Community, I am at wits end with this one. The Charge Controllers shut down and restart repeatedly once they reach a steady 58A or if they spike around 62+A for 10-20 seconds, with the 5 solar panels, in ideal conditions there should be around 100A steady.

Any suggestions would be greatly appreciated

Testing,

If I turn off any 2 controllers early morning or 3 controllers later in day, the system works, less than 60A output.

I have bypassed the BMS, no change

I have unplugged the BMV-700, no change

I have 5 x 365W, OCV 48V, SCC 10A, they each have a Smart MPPT 100/20 BT Charge Controller that feed into bus-bars then on to a 250A BMS and into a 800A LiFeP04 battery.

The Smart MPPT 100/20 BT Charge Controllers are set in Battery Preset of Smart Lithium (LiFeP04)

The BMV700

MPPT Controllers MPPT SmartSolar

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Alexandra ♦ commented · Dec 31, 2022 at 05:17 AM

@springgrove

What batteries/bms do you have?

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springgrove Alexandra ♦ commented · Dec 31, 2022 at 06:01 AM

5 x 365W, OCV 48V, SCC 10A, into 5 x Smart MPPT 100/20 BT Charge Controllers.

800A LiFeP04 battery made up of 8 400A CALB cells in 2 x parallel, 4 x series to make 12V.

BMS is a JK

BMS and BVM700 are out of service whilst testing, problem is persisting

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klim8skeptic ♦ springgrove commented · Dec 31, 2022 at 06:53 AM

The Charge Controllers shut down and restart repeatedly once they reach a steady 58A or if they spike around 62+A for 10-20 seconds, with the 5 solar panels, in ideal conditions there should be around 100A steady.

How interesting, the battery current form the mppt drops to zero? How much sun are the panels getting? Is the panel/sun angle good?

Post screenshots for the mppt showing trend graphs for both pv voltage/current, and battery voltage/current, while the problem is occurring.

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springgrove klim8skeptic ♦ commented · Dec 31, 2022 at 07:44 AM

Hi Klim8skeptic, sun angle is starting get a bit low however with all 5 controllers turned on were still getting enough current to cause this problem

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klim8skeptic ♦ springgrove commented · Dec 31, 2022 at 08:18 AM

It looks like the battery is being disconnected, causing a spike in the mppt output voltage.

The BMS has been by-passed?

Could it be a dodgy circuit breaker? Thermal ones are rubbish.

Measure voltage across the breaker when the fault is occurring.

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springgrove klim8skeptic ♦ commented · Dec 31, 2022 at 08:58 AM

Yes BMS is bi-pass,

I have a 300A C/B like this, is it rubbish ???, I can do better,

at 53A there is 150mA across breaker,

unfortunately I have run out of sun to do your last recommended test so will try tomorrow and post result, thanks so much for your assistance

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springgrove springgrove commented · Dec 31, 2022 at 06:48 AM

I should add that this system is on a caravan, off grid all electric system, thanks for any advice in advance

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springgrove commented · Dec 31, 2022 at 08:18 AM

5min Screen shots of BMV700

Plus Device list Charging

and not Charging (failing)

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Modifications Space

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Answer 1 · 2022-12-31T09:31:20Z

klim8skeptic answered · Dec 31, 2022 at 09:31 AM

I have a 300A C/B like this, is it rubbish ???

A red hot smoking turd..

at 53A there is 150mA across breaker,

You need to measure voltage across the breaker.

If you measure current across the breaker the multimeter fuse will fail, or the test leads will catch fire when the breaker goes open.

Repco open Sunday? An appropriate mega fuse will be ideal.

HNY.

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springgrove commented · Dec 31, 2022 at 01:49 PM

You need to measure voltage across the breaker.

*******at 53A there is 150mA across breaker,*******

Oops "at 53A there is 150mV across breaker", now removed.

100A mega fuse and mega fuse box/mount fitted, fuse to be replaced with 125A - 150A.

3.5kW Air Conditioner left running over night to run battery down to 60%

thanks again Klim8skeptic for your advice todate

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springgrove springgrove commented · Jan 01, 2023 at 07:55 AM

Hi Klim8skeptic, you have nailed it, thank you ever so much for your support. Getting a little late and hot in the day however still pumping 85+Amps into system, A/C pulling about 40A

I have two other of those "red hot smoking turd.." in system that I will replace, again thanks for sharing your knowledge base, you have saved my poor old brain from a blown circuit

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