The lowest pressure difference: 1V. Ultra low dropout design is used to achieve low power consumption and higher conversion efficiency,
Ok, so its likely a buck unit? Technically it's not really an mppt unit then?Looking at the specs in that link, it cannot increase the output voltage, only limit it -
Yes that might work. I'm assuming it detects cell voltage?MPPT does not imply boost, only that the load on the solar panels will be adjusted for optimum output.
The input voltage to output voltage range is a separate feature, depending on the system.
You could run one of those MPPT modules in to a fixed boost converter, to get the voltage you need without having a higher voltage solar panel setup?
ps. Be wary of "BMS" modules - they are not charge controllers, only voltage protection and [hopefully] cell balance.
Conventional lithium cells need a charge controller with current and voltage control, plus a total cut-off at full charge if using the cells to full capacity.
One of these may be suitable? 2A out at around 24V, so close to 50W:
It does still need a BMS with balance circuit, to protect the cells in the battery pack.
Is that essentially what placing a constant power supply across the battery does?If you want maximum capacity in the battery, you must use a charge controller that cuts off completely at full charge.
The MPPT one I linked to says it does that, and it combines the boost system to work from a panel like you have.
You can get away with permanent voltage limited charge if you keep it down to around 4V per cell, but that gives a lot lower battery capacity and most balance systems won't cut in at that.
I guess that also depends on how good my BMS is? Either way, I have a 50w panel and have about a half an amp load I want to keep running 24/7, so unless it's a clear summers day, the battery will take most of the day to charge if we only have about 3 amps or so available power to play with, so any period that it's potentially trickle charging is likely limited.With the maximum cell voltage connected, the "trickle" never drops to zero and the cells can be damaged.
With the cells you are using (2 x ~5AH in parallel, so 10AH) the cutoff should probably be when the current drops to something like 200 - 400mA, with full voltage.
Charging can restart when the battery voltage drops by eg. 0.1 - 0.2V per cell.
(You have to consider lithium cells as rather like balloons - any trickle of charge / air beyond the safe rating means they are increasingly likely to burst, creating a serious fire risk).
Yeah, I should be able to get a decent charger for this eventually.OK, with a permanent load it's not going to hold the battery at full charge, so it could work for a while..
I'd try it, and carefully monitor the battery voltage for a few days?
Ok, well i plan to do some real world tests anyway.A lower voltage will extend the cell life, however a normal BMS balance board will never do anything, so you are likely to experience problems unless you set the charge to 4.2V occasionally for the system to re-balance.
Watt-hours are calculated from average cell voltage x amp-hours, so eg. 3.6 or 3.7V per cell.
I'd definitely keep the larger solar panel - from the other thread, the long term average is probably 16% rated output, so 8W.
That's not going to last very long with a 12W ?? load.
I can draw up something later, but I had made a video before it blew up.Please post a connection drawing of all parts of your system, and voltages at each point.
Literally it's input was connected to my lab power supply set to 18v and 3 amps to simulate the power supply from the solar panel and them connected directly across my battery bank with my meter in series.
That's exactly the sort of thing I'm looking for, I was looking for something simple that can be made with off the shelf parts on some veroboard so I can get this unit working, can't wait to get something out of China. I only need 2 amps outputYou can make an MPPT solar controller and power supply motherboard like this by yourself:
MPPT Solar Controller and Power Supply Motherboard - Share Project - PCBWay
This is an MPPT Solar Controller and Power Supply and is part of a project to create a wireless home weather station. I plan to use mine to collect meteorological data and send it via wi-fi to my loca...www.pcbway.com
This is a PCB that accommodates one CN3795 MPPT solar controller module and up to three Mini360 power regulator modules for a wx station.
Turns out my PSU has a constant voltage and current setting. Took me a while to figure out what was happening and how to change it. The interface was not that intuitive.The current limit on the boost regulator should have been set well down, so it could not take excess power - no more than available. With no current limit, it will not protect itself.
It should be in current limit until the correct charge voltage across the battery is reached, then the current start to drop as the battery finishes charging.
Also, there is something seriously wrong with the PSU, if it's capable of 10A but the voltage was dropping way down at relatively low current!
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