I’ve been working on an iot project and wanted to power it with the sunny buddy and a pair of sm451k12l solar panels in series. I’ve been trying to characterise it’s performance with an ina219 based current monitor https://thingspeak.com/channels/1273554/ and have run into some problems.
I’m on my second sunny buddy and both are presenting the same problem. For the first day they work fine then as the sun sets and overnight they draw very little power however when the sun rises in the morning they enter a mode whereby they start drawing 8ma from the battery rather than charging it. There is no load connected so it must be the lt3562 doing this.
The ~chg pin is at 0.6v and the ~fault is at 3.5 so it’s not in a fault state. This obviously makes the circuit completely unusable so I’d appreciate any help. I’ve tried a new sunny buddy, reconnecting everything and adjusting the mppt voltage and nothing has worked
That might be an unwanted “feature” of the LT3652. How long does it take for the 8mA draw to go away? if it’s not very long, you might be able to compensate by using a slightly larger battery.
Never. Draw continues until sundown. Tried resetting it by covering the solar panel and uncovering it. Nothing fixes it. Would pulsing the shutdown pin in the morning fix it?
Would pulsing the shutdown pin in the morning fix it?
I don’t know, you’d have to give that a try and see. We’ve carried the Sunny Buddy for years and this is the first time we’ve ever heard of this issue.
A blocking diode hasn’t changed it unfortunately between the hours of 8am and 11am it was still consuming 5-10mA then the sun properly came out and it started working properly
When there’s a really bright day it can kick it out of this mode. Right now it’s been consuming 10ma for the last 4 hours. If the sun is not abnormally bright for January it doesn’t stop consuming current
Under the current conditions, your solar panels are clearly inadequate to the task.
Not the fault of the Sunny Buddy, although the required blocking diode should have been built in from the start. I’m surprised no one seems to have noticed this obvious design error before. It is a general rule of thumb that the manufacturer’s recommended application circuit is NOT to be ignored.
Here is the typical application circuit from the LT3652 data sheet, for future reference:
I’m not sure that’s the case as if i desolder and resolder the solar panel and battery and then put it outside it starts working again until sundown and then as soon as the sun comes out the next day it’s back to business as usual
![https://www.analog.com/-/media/analog/en/products/image/typical-application-diagrams/ltc/lt3652-8419.png?h=270[/img]](https://www.analog.com/-/media/analog/en/products/image/typical-application-diagrams/ltc/lt3652-8419.png?h=270%5B/img%5D){kind=link}