thanar
Member
- Joined
- Feb 12, 2018
- Messages
- 155
I am currently using an MPT-7210A MPPT solar charge controller / boost converter to charge my 36V 2s10pe-bike battery from a Lead acid 12V battery, which I keep under float voltage through the grid, since my solar setup is a bit off right now. I have set the Vmp (input) on the MPT unit at 11V to protect the 12V battery (the MPT unit wouldn't work with an input below 10V anyway)and the output voltage at 41V.These units are actually boost converters, however I have not been able to find a way you can "switch" it from solar charge controller mode to boost converter mode and back.
I've been having issues with this unit, even when it was connected to my solar panels, with its output voltage reading. Hare is my setup:
As we can see on the image, the battery voltage reading on the MPT unit is way above the one reported by the voltmeter I have connected to the brass bars. The (disconnected)battery voltage is 35.8V. That's also the reading the MPT unit gives before it starts ramping up the current. It stopped to 1.7A because the 12V battery dropped to 11V.There is no voltage drop on the cables leading from the MPT to the brass bars, since measuring the output of the MPT unit is reading the exact same 36.2V as everywhere else.
Here's where things gets a lot more interesting:
I need to run the charging port outside the shed to be able to charge the e-bike battery without removing it, soI am switching the charge cable with a longer1.5m 2.5mmpair. As soon as the MPT unit ramps up the current, the battery voltage reading on the unit raises extremely fast and reports charging as complete. Voltage readings everywhere is 35.8V -the currentbattery resting voltage- even on the MPT unit's output. What's even more strange, moving the cables around changes the reading on the MPT unit, while keeping the pair tightly together does allow for some current to go through. I have tried a different pair of chargecables of similar length with same results.
What do you people think is happening here? Could it be that I am running the unit on such a low input voltage and it fails on a reference voltage for the output? I am suspecting high frequencies boost converters use to convert DC to DC is the culprit here. Any other ideas? Do you know if Mike fromMikes DIY Tesla Powerwallhas an account on this here forums? Seems like he's done some research on these units.
Any help would be appreciated.
I've been having issues with this unit, even when it was connected to my solar panels, with its output voltage reading. Hare is my setup:
As we can see on the image, the battery voltage reading on the MPT unit is way above the one reported by the voltmeter I have connected to the brass bars. The (disconnected)battery voltage is 35.8V. That's also the reading the MPT unit gives before it starts ramping up the current. It stopped to 1.7A because the 12V battery dropped to 11V.There is no voltage drop on the cables leading from the MPT to the brass bars, since measuring the output of the MPT unit is reading the exact same 36.2V as everywhere else.
Here's where things gets a lot more interesting:
I need to run the charging port outside the shed to be able to charge the e-bike battery without removing it, soI am switching the charge cable with a longer1.5m 2.5mmpair. As soon as the MPT unit ramps up the current, the battery voltage reading on the unit raises extremely fast and reports charging as complete. Voltage readings everywhere is 35.8V -the currentbattery resting voltage- even on the MPT unit's output. What's even more strange, moving the cables around changes the reading on the MPT unit, while keeping the pair tightly together does allow for some current to go through. I have tried a different pair of chargecables of similar length with same results.
What do you people think is happening here? Could it be that I am running the unit on such a low input voltage and it fails on a reference voltage for the output? I am suspecting high frequencies boost converters use to convert DC to DC is the culprit here. Any other ideas? Do you know if Mike fromMikes DIY Tesla Powerwallhas an account on this here forums? Seems like he's done some research on these units.
Any help would be appreciated.