Lithium Battery charging
#21
Posted 30 June 2020 - 11:08 AM
Ya it is a pita. My two panels, one on roof 160 and one portable flex 100, are in parallel. Is it as simple as changing the plug on one to the opposite? (Plus minus) ... that is ... using a reverse male to female adapter. Or do I need to do some fancy rewriting?
I only use the flex panel when it is cloudier... so series would make more sense. In series the bolts are then additive say 9v on one and 8 v on the other if end up with 17v?
2016 Duramax 2.8 Diesel long bed Colorado 4WD with 2011 Eagle
#22
Posted 30 June 2020 - 03:56 PM
If you switch over to series, it is my understanding, you will need a second, separate controller if using a secondary, exterior solar outlet. (Rear back wall of Camper) If your flex is indeed wired with your roof panel in series entering the roof outlet, in conjunction, you are OK. I chose parallel for the plug & play option with my rear outlet. Series is intriguing. Would higher outside temp, hot, be any kind of consideration with higher V?
Edited by Stokeme, 02 July 2020 - 02:56 PM.
#23
Posted 01 July 2020 - 04:03 AM
You can do series... but that may have been a red herring I tossed out and not as critical as you might think given your low power production. Sorry.
The beauty of MPPT controllers is that they will massage the incoming power to feed the batteries what they most need... like Kobe beef!
So even if your one roof panel is only producing 80W (50% power) that will be converted to what the batteries need. If the battery is dead (11.5V) the MPPT will try and feed it at least 16.5V (5v more than it is at) 80w/16.5 = 4.8A.
Stokeme, I think your math is a bit wonky. Watts is Amps * Voltage. You mention 100W @24V = 100/24 = 4.167A. 200W at 12V = 16.67A.
Rob has 260W total available to him. Setting aside for a moment the difficulties of mismatched panels, lets say he hooks them up in parallel. Then he would be feeding 260W / 12.7V= 20.47A into the controller. (why 12.7? 12.2 is a discharged AGM battery... and the MPPT will always try to give the battery .5v more so that current can flow into the battery)
If he hooks them up in series, he will have 260W / 25.4V = 10.23A into the controller. (25.4V = 2x12.7v) The ACTUAL voltages and currents produced by hooking up in series and parallel are dependent on the specs of the panels, which we don't know right now.
In both cases, the MPPT will work to create what the batteries need. The series hookup gives the MPPT more room to play with, so is the preferred way to hook up panels to an MPPT controller.
There is a way to use the existing wiring in the camper to create a series connection vs parallel on your portable. I posted it some time ago, but my brain is futzed right now so I can't recall the details. It involved using a dongle....
2012 ATC Puma Shell build - https://www.wanderth...012-puma-build/
Power considerations thread - https://www.wanderth...e-power-scotty/
Building out an electrical system - So, you want to setup a good electrical system in your camper? - Electrical, Charging, Solar, Batteries and Generators - Wander the West
#24
Posted 01 July 2020 - 04:34 AM
Edited by Stokeme, 02 July 2020 - 02:59 PM.
#25
Posted 01 July 2020 - 12:54 PM
The series option is out. I like to keep it as simple as possible. Weather and canoes on top did me in. Sun this afternoon should help.
Vic having s second battery would solve the lack of energy over time. We use mostly the isotherm small fridge and led lights, charge iPhone and iPad. I did revive that LiFePo4 DIY battery and will consider finding a place for it. Just 30 lbs more. Put the two in parallel.
Sounds nuts I know (the truck hood is hot ) but having the flex mounted on the hood would be a great solution to canoe on roof. Maybe a curved mount on canoes hull!!
Light canoes stay on roof when popping up.
IMG_0785.jpg 199.89K 14 downloads
2016 Duramax 2.8 Diesel long bed Colorado 4WD with 2011 Eagle
#26
Posted 01 July 2020 - 06:39 PM
Just thought I’d post controller shot Sun not out yet but trying. I see there is less than 4v difference. The camper main knob is off.
2016 Duramax 2.8 Diesel long bed Colorado 4WD with 2011 Eagle
#27
Posted 01 July 2020 - 07:40 PM
2016 Duramax 2.8 Diesel long bed Colorado 4WD with 2011 Eagle
#28
Posted 01 July 2020 - 09:09 PM
I think there is a little confusion on how solar controllers/chargers work. The controller will try and output the set-point voltage for what ever stage of charge it is in (eg 14.4V in bulk/absorb or 13.4V in float). It won't try and add anything to this. However during the bulk phase of the charging the battery voltage is lower than the controller set-point, so the battery pulls the controller output down to what ever voltage the battery is at, and the controller provides as much current as it can up to the current limit (this is the Constant Current or CC phase). On an AC charger the current is limited by the controller to what ever its rating is (eg 30A on the IOTA). On a solar charger the current is more likely to be limited by the power available from the solar panels. Once the voltage has reached the absorb voltage, then the controller starts regulating the voltage (for example to 14.4V) until either the absorption phase times out or the current decreases to a certain amount (this is the constant voltage phase or CV) The charger then drops back to float and regulates the output voltage to whatever the float voltage set-point is (eg 13.4V).
The 5V difference is likely a miss-reading of the MPPT specs. The MPPT won't start until the solar panel voltage is 5V higher than the battery in order to insure there is enough power available from the solar panel to actually charge the battery. Before the MPPT starts, the panel is producing Voc. If you tried to start charging as soon as the Voc > Vbattery, as soon as you loaded the panel down by turning on the charger, the panel voltage would drop below Vbattery and you would need to shutdown. The 5V buffer prevents this power wasting 'short cycling'. Once the MPPT is charging, it will continue to run until the input voltage is down to ~ V battery + 0.7V, which is the diode drop inside the MPPT buck converter.
Happy Canada Day!
2016 Fleet Flatbed
2016 Toyota Tacoma
#29
Posted 01 July 2020 - 10:16 PM
2016 Duramax 2.8 Diesel long bed Colorado 4WD with 2011 Eagle
#30
Posted 02 July 2020 - 04:47 AM
Vic... I forgot to say... Happy Canada Day!
Thanks! With a nod to the folks who owned this land before we showed up, Happy Turtle Island Day!
2012 ATC Puma Shell build - https://www.wanderth...012-puma-build/
Power considerations thread - https://www.wanderth...e-power-scotty/
Building out an electrical system - So, you want to setup a good electrical system in your camper? - Electrical, Charging, Solar, Batteries and Generators - Wander the West
0 user(s) are reading this topic
0 members, 0 guests, 0 anonymous users