Cajunwolf
Solar Enthusiast
I'm shopping for a charge controller and wonder if I can't do it with one charge controller, can I put two or more charge controllers charging the same battery without problems? I have a 24-volt 400ah LiFePO4 battery bank.
Charge Controller Question:
- Thread starter Cajunwolf
- Start date
From what I've heard, using multiple charge controllers is a fairly common--even suggested--strategy in some applications. Marine/Sail-boats is one such area that I am aware of.
Not sure if you are asking OP or asking me, but in the example I gave, my understanding is that the primary purposes are (a) maximizing efficiency in frequent partial + unpredictable shade, and (b) redundancy.
Pierre
Somewhere down South
- Joined
- Dec 21, 2019
- Messages
- 1,130
Cajunwolf
Solar Enthusiast
The problem is finding the sweet spot between voltage and amps, parallel and series, that a charge controller can handle while remaining in my working-class income/retirement. I can do a 40a and 60 amp and support 2000 plus watts of panels for a 24-volt system. Yeah, I want to put one or more charge controllers on the same 400ah battery bank. I'm trying to start with 2000 watts and go to 3000 later. Some of this will have to be ground deployed when parked as my RV is only 28-foot. Hence for smaller cable sizes.
Cheapest solution (if you haven't started buying things yet) might be stepping up to 48V. @ 48V, an array of a given size could be served by a controller half the size as would be needed at 24V. But you may have other valid reasons for not wanting to move to 48V.
Pierre
Somewhere down South
- Joined
- Dec 21, 2019
- Messages
- 1,130
I quite understand the cost issue - I am in the same boat , trying to keep costs down. If you are not too worried about bluetooth comms and all that , you can use rather inexpensive charge controllers. I have been using 2x PowrMr 60 amp charge controllers , rated 12 - 48v , successfully without any issues for months. I sourced mine from Alibaba.
Cajunwolf
Solar Enthusiast
Cajunwolf
Solar Enthusiast
Yeah, I overspent on batteries, but at $600 each for 12-volt 200ah with free delivery, I couldn't pass it up. I bought four, so with 2s2p, I have 24-volts at 400ah, not bad. I've looked at those scc's among others. I'm shopping SunTan for used or open-box panels.
Cajunwolf
Solar Enthusiast
You've got me thinking of the unpredictable shade situation, and that's not a bad idea. I've also heard Will talking about using the pros of multiple SCC's as opposed to just one, forget it now, many moons ago. I have limited roof space but need at minimum 2000 watts of solar at 5 to 6 hours to charge my batteries if running the small AC. I will eventually have 3000, but again, there's that budget thing I can't get around. Anything above 1200 to 1500 watts, depending on the size of the panels, will have to be ground deployed, so a 24-volt or higher voltages going to the SCC's is a must for wire size. Good copper wire costs a lot of money, and you're going to get loss without good copper wire. I'm thinking 3-40 amp or 2-60 amp SCCs for now. They have some reasonably priced brands I'm looking over but will post back here what I like to make sure I'm not missing something. This is not my area of expertise.
Cajunwolf
Solar Enthusiast
Which model of PowrMr 60 do you have? All I can find are ones for Lead Acid or Gel.
Edit: I found this one.
https://www.amazon.com/dp/B097ML9HY...lja1JlZGlyZWN0JmRvTm90TG9nQ2xpY2s9dHJ1ZQ&th=1
Last edited:
Pierre
Somewhere down South
- Joined
- Dec 21, 2019
- Messages
- 1,130
Looks like the one you referenced is the new version and replaces my one. No wonder mine was so cheap !
Last edited:
I have two Victron 100/50 Smart MPPT solar charge controllers. One for the 640 watt array on the roof and the other for the 640 watt ground deployed array. They work great! The two solar charge controllers can work together through a networked link. I'm in the process of installing a Cerbo GX with the goal that I can get more historical data from my system so I can better understand what it's doing. I have 560 Ah of LiFePO4 in a 12 volt system.
Cajunwolf
Solar Enthusiast
I'm at 24-volts, so I need about twice the solar. I'm now thinking of three at 40 amps, each with its own array, but this still depends on what I can wrangle in used panels; then, I'll have a better idea of the total voltage(s) I'll be working with on with each array. Two will be ground or otherwise deployed. At this point, I think I should draw a schematic to post where everyone will have a better idea of what my thoughts are.
Watts are watts. The system voltage comes into play with your controller. A 60 amp controller is only going to produce 60 amps, no matter if you're 12 volt or 24 volt. But the number of output watts can certainly be different. If you're not maxing out the controller then system voltage is less of a concern. If you're over paneling then it is a concern.
The most important factor is PV Max Input Volts, which doesn't matter if your system voltage is 12 volt, 24 volt or 48 volt. 100 volts of PV input is 100 volts on any system voltage.
The most important factor is PV Max Input Volts, which doesn't matter if your system voltage is 12 volt, 24 volt or 48 volt. 100 volts of PV input is 100 volts on any system voltage.
Cajunwolf
Solar Enthusiast
I'm going with multiple SCCs to avoid maxing out anything, and that's also my reasoning on the voltage. Watts are watts, but the amperage/current halves from 12 to 24-volts and halves again going to 48-volts. If it weren't for the AC and occasional air compressor and my high-end computer (workstation) with its 1kw power supply, I could get by with 12-volts. Everyone's needs are different.
The 48V recc, was based on saving money on the charge controllers, not on wire lengths/voltage drop. As you correctly note, 24V is totally fine for a large vehicle sized system.
But a 40A SCC...
...@12V = ~500W
...@24V = ~1000W
...@48V = ~2000W
However if you have already begun purchasing things, or have other reasons for preferring 24V (personally I think 24V is often the sweet spot for large vehicle builds) then you might choose to just stick with the plan and use 24V and multiple SCC's (this has its own advantages as discussed)
Assuming your stick to 24V, I might consider:
3x 40A controllers or something similar assuming 3x40 would be similar in cost to 2x60
1 for starboard, 1 for port, and 1 one the ground deployed panels.
This would also allow you to build in stages as money allows.
Cajunwolf
Solar Enthusiast
Most of the SCCs I've been looking at are 12/24/48, and yes, I'm looking at three arrays; one rooftop, one on top of the Jeep, which will be put on the ground once parked, and one considerable ground deploy with three SCCs at 24/40a. That's the plan so far. Your cost in the wire is half that of 12-volt, and at today's copper prices, that's considerable savings right there. But I didn't go to 24-volt for savings; it's for capacity. I want 3000 watts available when I want it, instantly, with no fuss. I've already bought four 12-volt 200ah Chins batteries and a Giandel 24-volt 4000-watt inverter. The batteries are being configured as 2s2p with 400ah. That's okay for my needs, but I want to get two more batteries, just for peace of mind in the near future.
I have a 1988 28-foot RV on the Ford E350 chassis, and there is limited roof space because of A\C and 4-14"x14" vents. Depending on the panel and its dimensions, I can maybe get 1000 watts in panels up there. I'm shopping used. I can fit two on the luggage rack of my Jeep WJ, It's my tow vehicle, and I have a 3-foot porch on the back of my RV for the generator and such, and panels are thin; they stack well. This will allow me to have a large ground deployed array when parked in the middle of nowhere, my favorite spot. All suggestions are appreciated.
