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troubleshoot solar battery system with renogy inverter charger

marcusdenning39

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Apr 27, 2021
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Hi guys.
I would really appreciate any help or advice. I have a solar system running power for a shipping container. Theres 1.5kw of panels (6x250wp) and 3x20amp solar controllers (2 panels per solar controller). Two of the solar controllers are the renogy rover 20amp and the other is a different brand. I have 4x100amp lithium lifepo4 voltax batteries in parallel as a 12 volt system. Each battery has its own internal BMS. I also have a Victron battery management system connected. So everything was going great then last week I purchased the 3000w inverter charger (75amp) from renogy. This is great because it automatically switches from shore power to the batteries and is way better in terms of the inverter to my previous one and charges the battery now at the full 75amps rather than my old 30amp agm charger. So, after a day of the renogy inverter charger running I noticed that the 3 x solar controllers were going to 0 input amps for 30 seconds then re-starting, running for 30 seoncds and then stopping and restarting again. Oddly, I have a couple of ebay camping solar batteries also connected to the batteries with their own PWM controller and they were still puttting in current despite the 3MPPT controllers all stopping at exactly the same time. So I disconnected the renogy inverter charger from the batteries and then the solar controllers went back to working full time. Then I reconnected the inverter charger and everything was still working fine. But once I turned the switch back to on for the inverter charger the solar controllers went back to on for 30 seconds then off for 30 seconds. This problem would remain even when I turned the inverter charger off again. The only way to correct the problem entirely is to again disconnect the inverter charger from the battery. When I was experimenting, I put one of the solar controller LCD screens to volts and the other to amps. At precisely the time the solar controllers went to 0 amps output the voltage spiked from the 14 volts input current to like 15-17 volts. So I cannot workout whats going on. Everything was fine before the introduction of the renogy inverter charger.

One point to add. the 3 solar controllers output cable to the battery is via Anderson plug. I have connected them together using a Y 3-way Anderson plug connector so all the current is going down one line to the batteries which is fused with an inline 60 amp fuse that never trips. I know this cant be a problem because it was working for months before the inverter charger was installed but as a general question is it ok to have this occur rather than having say 3 lines of cable running to the battery bank via a busbar or similar setup?
 
How is the Renogy Inverter/Charger wired to the system? Directly to the battery banks? May be show us the wiring diagram?
 
How is the Renogy Inverter/Charger wired to the system? Directly to the battery banks? May be show us the wiring diagram?
Hi. So the renegy inverter charger is connected to the negative of one battery at one end of the bank via a 180amp cable and then the positive of the 4th battery at the other end of the battery bank. I took 3 videos of the problem but I cant post them here. Its so incredibly frustrating. The location is 200km from home so its really annoying to be in the middle of nowhere without understanding how to fix the problem.
 
I will offer a couple of SWAGs for your situation. Your first post is a bit hard to read, and this key sentence confuses me:
At precisely the time the solar controllers went to 0 amps output the voltage spiked from the 14 volts input current to like 15-17 volts.
Can you please restate output versus input, current versus volts?

But anyway - your SCC Battery charging Voltage should probably be in the range of 13-6V-13.8V (float mode), and 14.2-14.5V (Boost/Bulk mode). The should never, ever be offering 15-17V on the output side. Maybe the Renogy monitor is measuring at the wrong place (within the controller)? It should be offering a measurement of the battery bus voltage. OR, your inverter charger is grossly defective in charging mode, if it is genuinely inflicting such voltage on your batteries. BMS over-volt protection will be disabling battery charging in that situation protectng the batteries. And it will also be appropriate for your SCCs to basically disconnect and send zero current, because they're past the over-voltage limits on the batteries.

With 20 Amps rated output, your SCCs can theoretically accept about 320 Watts of power on the input side. Your "over-paneled" ratio of 1.56 shouldn't be a significant issue, even under the best of sunlight conditions.
- - - -
I'd return the Renogy "Inverter/Charger" unit, and switch to separate charger+inverter+trasnfer switch.
 
Hi. Sorry for the confusion. The 3 solar controllers are next to each other. so in a test, i had the LCD screen on one showing the voltage. The second solar controller LCD was displaying the amps being sent to the battery. I noticed when the solar controllers went to 0 the voltage on the display went from like 14 volts to 17-18v. The renogy solar controller was connected to the battery bank but it was doing nothing other than acting as an inverter at 240v powering a fridge in the shipping container. The shore power wasnt operating so that's not interfering. But even if the inverter controller is switched off. So long as its connected to the batteries. this 20 second on 30 seconds off routine continues. was going to seperately connect each solar controller to a negative and positive busbar in the battery bank. It means I can add a separate array in the future without exceeding the max amps through the single cable which runs to the battery bank which is connected to the three different solar controllers. But this cant be an issue now because that wiring setup has worked for months before i connected the inverter charger last week. Thank you for yout time on this post.
 
It sounds like your SCCs are confusing each other as they each search for their own MPPT.
And perhaps the voltage spike at disconnect (amps going to 0) is just an unfortunate measurement of the panel Voc when the load is removed.
I could see how introducing a large 75a SCCs into the mix of much smaller SCCs could change their behavior.

Just a thought.
 
It sounds like your SCCs are confusing each other as they each search for their own MPPT.
And perhaps the voltage spike at disconnect (amps going to 0) is just an unfortunate measurement of the panel Voc when the load is removed.
I could see how introducing a large 75a SCCs into the mix of much smaller SCCs could change their behavior.

Just a thought.
Hmm yes except that the 75 amp charger aspect only runs should i run my generator which acts as the AC shore power. I never do that in the day and in any case its rare when I do and late at night if the battery charger of the unit went was activated. Renogy told me the SCC will go to zero if the battery charger starts pumping in 75 amp charging current so as to protect the batteries. Except im not doing that. The only part working is the inverter in the day time. its so weird.
 
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