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Multiple charge controllers vs. one high current unit?

oldryder1973

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Rookie here. In the planning stages. Initial estimates indicate I'll need a charge controller rated for 100+ amps. Looking for a reason NOT to go instead with a split system and 2 smaller (60amp) controllers with independent but identical battery banks. cheaper and has redundancy. I can't really see a down side so maybe I'm missing something.

thx to anyone taking the time to offer advice to a rookie.

mark in MN
 
It is convienient to have a single controller. Not redundant. If you have your "2" batteries paralleled, you could shuck one if it limps and re-use at lower voltage or switch it with a selector and keep a single point output to source to a load such as an inverter...... unless you want two inverters also, then you can sync them to stack if they have the stuff. Then if one dies you just have half watts.
 
Larger controllers can often handle higher voltage like 150v. Smaller controllers may be limited to only 100 volts. If you plan to increase the size of your array the additional voltage overhead could be a benefit of a larger controller. That plus two small ones may cost more than one large one. And while I'm thinking larger units often times have more features or software. Guess it depends on the brand.
 
thx for replies. Controllers I've been looking at are Renogy mppt 60a. for $320 vs. $700 for a similar (same features) 100a. unit so (2) 60's are less than one 100a. The double system will be somewhat more wiring but to me that's worth it to have a redundant system.
 
Controllers I've been looking at are Renogy mppt 60a. for $320 vs. $700 for a similar (same features) 100a. unit so (2) 60's are less than one 100a.
If you are only looking at the charging amps while shopping for an SCC you might consider the PV voltage from your array as well. In fact, the SCC should be the third item you purchase, after your batteries and panels - its the critical piece that must match both those items.
 
thx for replies. Controllers I've been looking at are Renogy mppt 60a. for $320 vs. $700 for a similar (same features) 100a. unit so (2) 60's are less than one 100a. The double system will be somewhat more wiring but to me that's worth it to have a redundant system.

Check out EPEver on Amazon. Will's reviews of them are positive and they are quite a bit less money for the same thing. Specifically the EPEver have larger wire ports that take up to 6ga wire (vs like 8-10 for Renology IIRC). Exactly what I needed for my project at a lower price? ??

Edit, here's a link. https://www.amazon.com/dp/B07J2GJJK4/ref=cm_sw_r_apa_i_mjGWEbM5S0MZC

And the video.
 
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First off, Renogy is Value - Bargain Basement junk to put it simply. There are tons of bad reviews and horror stories, be aware of that.
Having a single SCC that is capable of 100A output is a tough find and not usually in the lower end of the scope of gear. Believe it or not the average of max output is around 75-80A for an SCC simply because of what is involved in higher capacity equipment.

Using multiple SCC's which are Smart Linked Together meaning that they are interconnected and working cooperatively together is typically the way that charging capacity is handled. Each SCC would draw from it's own solar array and charge the same battery bank, hence why it is important that they work in tandem cooperatively.

Various manufacturers accomplish this using different methods. For example Midnite Solar Classic SCC's which are interlinked with direct communications wiring between the SCC's where one become the master control for one or more SCC's. MIdnite, Outback, Victron, Tristar, EP-Ever and more have such capabilities with various add-ons etc (depends n brand).

Alternatively, Will's reviews of the MPP Solar equipment shows that several of their All-In-One systems can also be linked together, so you can have multiples working together. https://usa-mpp-solar.com/store-buy-now
 
What is your application (stationary, vehicle, boat) and system (battery) voltage?
 
Application is stationary. I expect batt voltage at 24. Estimating 1000 - 1200w. solar total. At this point it's all open to change. Feedback has already been helpful.
 
You should be fine with a single 45 to 60 amp controller if your system is 24V (1200W / 24 = 50A).

As far as single vs multiple MPPT, single has the advantage of simplicity and centralization, whereas multiple is theoretically more efficient in some situations and offers some redundancy.

Others have noted smaller controllers will have a lower input voltage rating, but in my opinion this is a non issue in most circumstances. Sure a smaller controller might have lower max input voltage, buy you'll have two controllers, together their input voltages will match or exceed that of most single large controllers, right?
 
It has already been said but just to reiterate, it's fine to use two MPPT controllers connected to the same battery bank, you just can't connect two MPPT controller to same PV array. Whilst I do agree with @Steve_S in that having your SCCs communicate is preferable, don't sweat it too much - two independent SCCs will still work fine so long as you use identical settings. The idea that they 'fight for control' is an urban myth. You just have to be careful not to exceed the charging rate specification of your battery.

One thing to consider: what batteries are you using? You mention the need for a "100+ Amp" controller, you obviously have a sizeable array. Don't forget that lead-acid batteries shouldn't regularly be charged at more than C/10 Amps e.g. 10A for a 100AH battery, so to safely accept a 100A charge you'd need a 1,000AH battery bank. Very different case for Lithium-ion, which can be safely charged at up to around 1C Amps.
 
It has already been said but just to reiterate, it's fine to use two MPPT controllers connected to the same battery bank, you just can't connect two MPPT controller to same PV array. Whilst I do agree with @Steve_S in that having your SCCs communicate is preferable, don't sweat it too much - two independent SCCs will still work fine so long as you use identical settings. The idea that they 'fight for control' is an urban myth. You just have to be careful not to exceed the charging rate specification of your battery.

One thing to consider: what batteries are you using? You mention the need for a "100+ Amp" controller, you obviously have a sizeable array. Don't forget that lead-acid batteries shouldn't regularly be charged at more than C/10 Amps e.g. 10A for a 100AH battery, so to safely accept a 100A charge you'd need a 1,000AH battery bank. Very different case for Lithium-ion, which can be safely charged at up to around 1C Amps.
Well yes & no. All depends on the cells used as to how many amps they can take for charging. Lithium Based Batteries unlike Lead handle amps very differently in general. If you have a 280AH Pack that can accept 1C Charge rate, it will do it just fine but get warmed up too and quite quickly while at 0.5C it would barely even notice it and not warm up noticeably.

My own Midnite Classic 200 pushed 79A (it's max) to the battery bank and I am adding another in parallel to provide 158A capacity for a 910Ah Battery Bank. Even then it's short for max charge capacity BUT I am using two 280AH packs + two 175AH packs, of which both types of cells can comfortable take 1C Charge rate BUT I would not want to exceed the "Lowest Common Denominator" which in my case is the 175AH cells which would max at 175A.

The combined SCC's need to match up on their settings obviously. So if you have a "Full Disconnect" set to a certain voltage & amperage (all depends on your particular SCC) they should behave as one for the most part and must be Voltage Calibrated so they see & correct / compensate for any voltage variances within the equipment. The SCC's cannot compete, they have to work cooperatively and harmoniously for the best end result.
 
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