Do I need a charge controller?

erniejt · 11-06-2018, 08:37 PM

This might be a dumb question from a newbie, but bear with me.
I am in the planning stages of an electrical system for a skoolie. I plan on using 8 (maybe just 6) 24 volt, 300 watt solar panels. I plan on keeping the system 24v and use a step down for 12 volt operations.
I like the look of the OUTBACK POWER FX2524MT 2500W 24V MOBILE/MARINE INVERTER/CHARGER to charge my group of 24v batteries and to invert to AC for AC operations.
Here is the dumb question. Do I need to add Charge controllers? The way I understand it, the controllers are used for battery charging. Could I just run from the panel combiner to the Inverter/Charger?
Thanks

john61ct · 11-06-2018, 09:56 PM

Yes.

The battery and loads (incl inverter) are in the same circuit with charge sources (incl the SC output.)

erniejt · 11-06-2018, 10:03 PM

Quote:

Originally Posted by john61ct

Yes.

The battery and loads (incl inverter) are in the same circuit with charge sources (incl the SC output.)

Thanks for the reply. I'm a little confused though. Yes I should use controllers? or yes I can run straight? Not sure what you mean by the same circuit

JDOnTheGo · 11-07-2018, 05:36 AM

Yes you need a charge controller.

john61ct · 11-07-2018, 06:55 AM

The only context where no controller is OK:

Storage, start with 100% Full batt
Tiny panel, used only to counteract self-discharge and vampire loads, amps under maybe .05C, compared to batt
Cheap Starter batt you don't care about

oricha1984 · 11-07-2018, 07:40 AM

https://www.altestore.com/store/outback-m46/

erniejt · 11-07-2018, 08:37 AM

Thanks, I think I'm starting to understand. I think I read somewhere on this site that I would need a separate controller for each panel. Is this true or could I get by with one (or two) big one(s)?

john61ct · 11-07-2018, 12:08 PM

Most people buy one big SC for all their panels.

But all the panels on one SC should match each other.

Some try to get best optimization of partial shade handling by using a 1:1 ratio.

Victron MPPT's pricing model allows for that without costing much more, 75/15 model only $125 supports 220-260W. Best to buy higher Voc rated panels to maximize MPPTs advantage, say 40+V

erniejt · 11-07-2018, 01:20 PM

WOW! That's the model I was looking at! The panels I was looking at are the Renogy 300 Watt Monocrystalline Solar Panel which have a VOC of 39.82 Volts, so I guess that would be good enough. I'd be using 8 Trojan J200-RE 12V 200AH (20HR) Premium Line Flooded Batteries, paired in series to effectively create four 24 volt batteries. Could I use one of the previously mention controllers for two panels running to a pair of batteries, or would something beefier be better?
While I'm at it, when running from the inverter/charger (charger side) to the batteries, could that connection be made through a buss bar? Inverter side?
BTW, thank you again for being so informative and patient. I'll try to come up with a diagram for approval.

john61ct · 11-07-2018, 03:34 PM

Quote:

Originally Posted by erniejt

That's the model I was looking at!

Need to go up a step if 12V bank, the 15A max output would cut off IMO too much power at peak times. Fine for a 24V House circuit though, but why?

Yes that panel voltage would let the MPPT algorithm optimize well.

> Trojan J200-RE 12V 200AH (20HR) Premium Line Flooded Batteries, paired in series to effectively create four 24 volt batteries

RE line is pricey, but yes should last longer **if** you coddle them well.

Put all those batts into one big House bank, much better for many reasons, including greater total capacity (Peukert's Law) thus less V drop, shallower cycling and greater longevity.

Then all your charge sources get connected via the same busses.

I like separating Loads from Charge busses, but that's really dictated by my BMS design for LFP usage, not usual for lead banks, unless it makes sense to you for other reasons.

erniejt · 11-07-2018, 10:55 PM

Wow John, you sure give a guy a lot to think about. Your line about why 24 volt got me thinking. I’m not sure why I decided to go that route. So I started “over” going 12 volt. I also found some Crown batteries that are about 1/3 cheaper than the Trojans.
So after my research, this is the component list I have come up with. I would appreciate your input as to whether it will work, and any changes or suggestions you may have.

Renogy 165 Watt 12 Volt Polycrystalline Solar Panel (12)
Magnum Energy PT-100 MPPT Solar Charge Controller (2)
Magnum Energy MS2812 2800W 12V Inverter/Charger (1)
Crown Battery 215AH 12V Flooded Lead Acid Battery (eight)
Midnite Solar MNPV Disconnecting Combiner Box (3)

12 Panels in 3 rows of 4, each row connected in parallel and leading to a Disconnecting Combiner Box. The outputs of the combiners then led to 2 Controllers, then on to charge the batteries (connected as on large bank per your recommendation). The inverter fed by the batteries and charger from shore power. I am also pondering the addition of an automatic switcher and generator for the AC side, but maybe I’m getting ahead of myself.
Anyway, I’d appreciate your expertise and opinion. I am an “ace” with plumbing and mechanical things, but a relative newbie for electrical.

john61ct · 11-08-2018, 05:19 AM

Crown are great, but compare to Trojan' regular lines not RE.

But usually in the US, the best battery value by far is Duracell (actually Deka/East Penn) FLA deep cycle golf cart batteries, 2x6V, around $200 per 200+AH pair from BatteriesPlus or Sam's Club. Deka-labeled same batts also sold at Lowes.

Good call on sticking to 12V absent a compelling reason to go higher.

Magnum makes excellent inverters, but also compare to Victron, especially wrt their PowerAssist feature and Color Control GX for integration / monitoring. Also Victron MPPT SmartSolar series, very flexible and excellent value.

If you do go Magnum, get the BM/shunt/remote so measured endAmps determines 100% Full each cycle, greatly extend bank longevity. On the Victron side I believe can get that from Color Control GX + their BMV.

The shore power transfer functionality should be included in any big inverter / charger.

Go for panels with higher Voc rating to take better advantage of MPPT efficiency.

What is the rationale for the
> Disconnecting Combiner Box
?

If that is a VSR, I'd reco Blue Sea for that. Their 500A ML- series is proven bulletproof, pass it on to the grandkids.

Not I am not saying your list is bad stuff, just not in the mainstream for rough / mobile use over the years.

Heleads · 11-08-2018, 07:05 AM

If you have not already bought your batteries and can afford the initial cost investment, go with lithium batteries rather than lead-acid. You will come out ahead if you plan on using your system more than 5 years and you wont have to be worried about making sure you do not run your batteries down lower than 50%

erniejt · 11-08-2018, 02:58 PM

Quote:

Originally Posted by Heleads

If you have not already bought your batteries and can afford the initial cost investment, go with lithium batteries rather than lead-acid. You will come out ahead if you plan on using your system more than 5 years and you wont have to be worried about making sure you do not run your batteries down lower than 50%

Ideally, I would most certainly go Lithium, but my costs are already sky high. Not saying I have completely discounted the idea, but at least at this stage it's a bit difficult.

JDOnTheGo · 11-09-2018, 06:23 AM

As a lithium user, I can attest that they are mighty awesome! However; I'd encourage a very serious evaluation of your intended lifestyle before committing to them (as well as solar). If you are certain you'll be boondocking/off-grid and living on solar, lithium is very hard to beat. If your requirements are such that you'll need to run a generator every day, the value/benefit of lithium/solar quickly falls off (but rarely falls all the way to zero, IMO). If a person has never lived the lifestyle and just 'hopes' that they will be able to make it happen/enjoy it, then it's probably better to save your money and attempt it with a generator. If it works/you like it, then make the investment. I've seen a number of folks with big plans that get out there and find that it isn't what they thought it would be.

erniejt · 11-09-2018, 07:04 AM

I value your opinion and your points are quite valid. Something I forget to mention is that I am a former charter sailboat skipper an have had several years of experience living aboard a 50ft boat. Granted, a lot of that time is tied to the dock on shore power, but weeks at a time I was "off the grid". My DC needs are rather small, although my AC needs include a computer and TV that would require substantial stored power for inverting.
As I said near the outset, I am merely in the planning stage right now, so I haven't ruled out lithium, it's just an expensive pill to swallow. Other than initial cost, I must admit I have never heard a bad word about lithium.

JDOnTheGo · 11-09-2018, 07:32 AM

You have the experience to which I was referring. Major Kudos to you!!! I have tried to liveaboard twice and failed both times. I finally realized, the second time, that being alone in that environment was too much for my little brain. That surprised me as I routinely spend weeks in total solitude boondocking with the RV. Now looking for a like-minded female that wants to give it a try!!

Given your past, I bet you have experience with wind generators. They are typically not easily possible with a typical RV/bus. However; if I person had a spot on which they spent a large chunk of time (and there is some wind there), I believe installing a semi-permanently mounted marine style wind-gen would be a great power source option (not sole source) which might ease ones electrical storage requirements.

erniejt · 11-09-2018, 07:38 AM

Oh trust me! I have considered EVERY option. If it were safe and practical I might even consider a small nuclear reactor (LOL) Maybe when we finally get our flying cars!

vintageracer · 11-14-2018, 03:42 PM

You might want to watch this video.

The presenter gives a very basic but good explanation of how a solar system works and the components to build one for a van.

This fellow teaches a course on building out vans.

You already may know all this information or not however I am sure there are some on the site that could benefit from watching this video.

I have no association with the presenter.

https://www.alternativehomestoday.co...ezaq7bfjg1ovze

frodo2222 · 11-14-2018, 04:36 PM

Quote:

Originally Posted by erniejt

Thanks for the reply. I'm a little confused though. Yes I should use controllers? or yes I can run straight? Not sure what you mean by the same circuit

yes you do and the very best I found was the Trimetric from Bogart here is the link..I've used many and this allows me to REALLY get all the info I want...Hope it helps.

TriMetric Model Descriptions - Bogart Engineering

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