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Forum Index : Solar : Protection of solar controller in case of loss battery supply
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herbnz Senior Member  Joined: 18/02/2007 Location: New ZealandPosts: 258 |
As we all know the controllers don't like solar connected when there is no battery. I have always been conscious of this and try to minimize the risk of a battery trip taking out the solar feed. What I am thinking of trying is a relay energized by the battery the contacts dropping off the solar if battery fails. Not sure if it would be quick enough to prevent damage but for a small power loss may save the cost of a new controller. Has anyone have any thoughts on this. I'm thinking of the accidental tripping . |
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| davef Guru  Joined: 14/05/2006 Location: New ZealandPosts: 499 |
Good point. I will have to check with the designer of my SolarBMS (electrodacus.com) to see if he handles that case! I already have an analogue-based HVD(high voltage disconnect) which I could also drive with an analogue-based LVD so if the battery voltage dipped below a set value it would turn off the PV. Most of the circuit would be a copy of this. My current HVD uses Hi-side MOSFETs, same as the link, although SolarMike suggested a lo-side MOSFET switching solution further down the article. Edited 2019-08-24 20:42 by davef |
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| Solar Mike Guru Joined: 08/02/2015 Location: New ZealandPosts: 1138 |
PWM type controllers should be able to handle a battery disconnect (breaker or fuse blowing) as the now open circuit PV voltage wont be much higher than the battery. Its the mppt type that will self destruct due to the very high voltage spikes generated when the load (battery) is suddenly removed, currents flowing in the buck inductor have nowhere to go, so the voltages rapidly peak to destructive levels, a high power transorb or TVS diode on the output may save the day, or may not most likely. My solution to this is have a fast acting independent of the cpu, over voltage solid state trip that shorts the output with a 100w 5 ohm resistor, and also signals the cpu of a fault, thus allowing it to shut down the input. I think a relay will be too slow, by the time it activates a smoke ring is floating in the air. Cheers Mike |
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