Voltage where there shouldn't be any

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Ako
Ako Registered Users Posts: 184 ✭✭
in Solar Beginners Corner #1
Not sure if i should have posted here or on the Advanced section . I have an old Style Victron 150-70 Blue Solar MPPT , the one with a small screen and 4 buttons on the front for Setting up , Monitoring and reading History etc . The unit has been performing perfectly until  About 2 weeks ago when i removed my 16 assorted sizes Poly Solar panels as they were over 15 years old . I replace them with 4 new large Mono ones of around the same total Wattage , looking at history it was some hours after i  had removed the old panels , the first night without any connected ready for the new ones to be fitted the following day that the issue started  .

Yesterday i noticed through Victron VRM that the MPPT had voltage at the internal Panel input terminals . Looking back i can see that there has always been just under 2 volts through the nights but now i have 21 volts but no current , i know its the charge controller and not the panel cables that has the voltage in it as i tested it without any panels connected , 21 volts on the terminals but as i would expect nothing at all on the input cables . VRM shown the voltage increases to 23 volts if i connect the panels . I am really concerned that my new panels are going to be damaged so i disconnect the input cables every night and reconnect in the mornings . The 2 weeks before i had noticed they remained connected with 23 volts which i would imagine travelled through the cables to the panels . The MPPT is showing no sign of being effected in any other way , i have checked the voltages , temperatures , setting points for Bulk and Absorption , Temperature compensation , history , absolutely everything is spot on . Has anyone else experienced this and if so what was the results and what damage did it do .
2240 Watt Array  4 x 460 Watt Mono Panels + 2 x 200 Watt Panels
Victron Smart 150-70 MPPT Charge Controller
24 volt Battery Bank 4 x 6v 400 Amp/Hr Trojan L16 AGM
LiFePO4 Lithium 100 Amp/Hr Battery for Backup
Victron 1600w Multiplus Compact Inverter/Charger
DC to DC Charger ( Non Isolated )
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  • littleharbor2
    littleharbor2 Solar Expert Posts: 2,046 ✭✭✭✭✭
    #2
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    If there's zero current flowing I doubt you have anything to worry about. Do you have a DC clamp meter?

    2.1 Kw Suntech 175 mono, Classic 200, Trace SW 4024 ( 15 years old  but brand new out of sealed factory box Jan. 2015), Bogart Tri-metric,  460 Ah. 24 volt LiFePo4 battery bank. Plenty of Baja Sea of Cortez sunshine.

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  • Ako
    Ako Registered Users Posts: 184 ✭✭
    edited January 2023 #3
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    Unfortunately no i don't , I only have a Multimeter that reads up to 20 amps , i don't know if it helps or identifies anything but i set it to read Amps and the dial to " mA "and there was a tiny spark when i touched the probes to the terminals and the reading was 0.00 , when i changed the setting to " A "on the Multimeter it read 0.002 . When i removed the panel cables from the terminals it made no difference , still a tiny spark each time with same readings on each setting .  This is the screenshot from Victron VRM of the activity at night . .

    2240 Watt Array  4 x 460 Watt Mono Panels + 2 x 200 Watt Panels
    Victron Smart 150-70 MPPT Charge Controller
    24 volt Battery Bank 4 x 6v 400 Amp/Hr Trojan L16 AGM
    LiFePO4 Lithium 100 Amp/Hr Battery for Backup
    Victron 1600w Multiplus Compact Inverter/Charger
    DC to DC Charger ( Non Isolated )
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  • Vic
    Vic Solar Expert Posts: 3,208 ✭✭✭✭
    #4
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    Hi Ako,

    It is normal for MPPT CCs to show input voltage (on the PV terminals,  and on the LCD display),  in total darkness.

    It IS a good sign,  that there is no short, to ground, from the power transistors that are part of the circuitry in the CC (the Buck Converter).

    In systems that do not have too many PVs or PV strings in parallel on that input to the CC,  this voltage is usually, about 2/3 of the battery voltage.

    FWIW,   Vic
    Off Grid - Two systems -- 4 SW+ 5548 Inverters, Surrette 4KS25 1280 AH X2@48V, 11.1 KW STC PV, 4X MidNite Classic 150 w/ WBjrs, Beta KID on S-530s, MX-60s, MN Bkrs/Boxes.  25 KVA Polyphase Kubota diesel,  Honda Eu6500isa,  Eu3000is-es, Eu2000,  Eu1000 gensets.  Thanks Wind-Sun for this great Forum.
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