Help- will I benefit from this mppt controller? 500w 30v set up

[Richard_m]

Hi all, New to this group and before I go ahead with a purchase of the following controller, I would like opinions based on my set up and what I require: http://www.ebay.co.uk/itm/12-24V-10A...item8bc7b7bc8b

I have a 500w set up of two 250w panels that produce 30v in parralel... this is currently hooked up to a 30a pwm controller and 510ah of battery power.

now the question is, what kind of benefit would I get investing in the tracer 40a mppt controller as linked above and is this controller known to be good? I am on a budget so any more expensive controllers are out the question.

I assume that as I have 30v coming in from this large panel array the pwm is severely limiting the max input I could generate from such array.

currently on an overcast day with the pwm (as taken now), it is reading 13.3v at 4.9 amps... how would this compare to an mppt on said set up? I assume it will be greater by far.
I look forward to replies amd hopefully a rough calculation on what my benefit would be with such change?

[Wy_White_Wolf]

Yes.

PWM controller amps in equals amps out. So:

500W / 30V = 16.7A to charge the batteries. 16.7A * 12V = 200watts. The charge controller is wasting 60% of your wattage.

MPPT controller watts in equals watts out minus a little for conversion.

500W / 12v = 41.7Amps. A whole lot more charging power.

WWW

[Sunking]

Because right now all you have is 200 watts of panels. Just as well throw 1 panel away.

[SunEagle]

Not only is that PWM CC robbing you of panel wattage, even if it delivered 10 amps each for those two 250 watt panels (~20A) that is not enough to properly charge your 510Ah battery system. 510/20 = C/25.5 charge rate which is too slow.

[PNjunction]

I know you want to go budget, but one thing to consider is just how effective IS the mppt algorithm of the cheaper units? Just painting mppt on the case does not mean it is truly effective as compared to the higher priced quality units. The "sleep and sweep" and other parts of the algorithm have to be effective as well, although weasel-words like "up to" cover their butt.

You need to use one for any panel voltages larger than a single nominal-12v panel just to function at all, so you are covered there, but again how effective is the internal algorithm. Some makers are much better than others in this regard.

One way of dealing with this at the low-power end of solar array (which you aren't - you need to go bigger) like 200 watts and lower is to simply use another panel. With a high-quality pwm controller, you may actually beat a junk mppt controller.

Mppt does best in colder conditions, and at deeper depths of discharge. If you aren't in a cold clime, and are not going beyond 50% DOD regularly, the gains may be minimal. ANY gain however is always a good thing, especially in areas of low solar-insolation, so it would be up to the end user if it would be worth paying for that or not - or if the additional of one additional panel would work out better financially.

Much of it is based on how you do your power / battery budget. Do you only take your system down to 25% DOD? If so, the gains of mppt in a moderate climate may not rule out a simple pwm.

Essentially, we can bench-race specs all day long, but one has to look at it in real-world terms according to your own usage pattern.

If you don't accurately calculate these things, then yes, just throwing mppt on a project works (and is mandatory for high voltage panels), but if you do so, don't shoot yourself in the foot by going CHEAP.

[paulcheung]

Your panels are grid-tie large panels, The least you should get is the Tracer 40 amps MPPT charge controller. it is only little more than $200 US dollars. it will pay for itself in no time. 30 volts to charge 12 volts bank with PWM controller is waste of energy.

[PNjunction]

Paul is totally correct. MPPT is the way to go with your high voltage panels.

The $60 question is - is the Tracer's own mppt algorithm up to snuff compared to higher-tiered products?

[paulcheung]

It is not bad, I used to use it when I only have 2 225 watts panels on my 12 volts system, it charge between 25 to 35 amps to the battery with over 75 feet small wires from panel to controller. The only different are those features like adjustable absorb voltage and manual EQ.

[Neilboat]

Hi, Im a newbe here and havent introduced myself yet, but as I use a Tracer40A I thought I'd throw myself straight in...... You didnt mention what Type of batteries you are using, If they are AGMs you might run into trouble as the module only has settings for GEL, SLA and FLA and the parameters are not user adjustable as far as I'm aware

Regards Neil

[inetdog]

Hi, Im a newbe here and havent introduced myself yet, but as I use a Tracer40A I thought I'd throw myself straight in...... You didnt mention what Type of batteries you are using, If they are AGMs you might run into trouble as the module only has settings for GEL, SLA and FLA and the parameters are not user adjustable as far as I'm aware

Regards Neil

SLA (sealed lead acid) is often used to refer to AGM, especially when GEL (the other type of sealed lead acid) has a separate setting.
The problem is that different chemistries can result in a wider range of recommended values than one setting can cover. The common point of all of them is NO EQUALIZATION, at least in the sense that term is commonly used.

[PNjunction]

To add to that - when only "canned" settings like "sealed" or "flooded" are found and you are using an agm:

Be SURE to look in the manual for what the actual VOLTAGE is for each setting!

One example is the Morningstar line of CC's that only have a "sealed" and "flooded" jumper. What this really means when you look at their actual voltages, is 14.1 vs 14.5v.

If you use an agm which needs 14.4-14.7v in cyclic service set to "sealed" you will severely undercharge the agm. For Morningstar, "sealed" means GEL. Gel's don't want more than 14.0/14.1v, but of course agm's are physically sealed too!

What happens when you rely strictly on canned settings and don't check what their voltage means, is that in this case, your AGM will be severely undercharged by the Morningstar because you didn't check what the voltage actually is in the manual.

Conversely, if you are using a GEL (not recommended anyway for cyclic solar duties), and your CC's "canned" voltage for "sealed" is actually 14.4v, you will prematurely burn up your gel.

Moral - don't go by the silskscreen labels to help the noobs - they may actually harm the battery if you dont' cross-reference what voltage it really is in the manual!


So, for an agm that sees cyclic service, it is actually better to use the "flooded" setting, which matches the voltage needed by the agm! It just so happens to work well with flooded.

[PNjunction]

So, for an agm that sees cyclic service, it is actually better to use the "flooded" setting, which matches the voltage needed by the agm! It just so happens to work well with flooded.

The inability to edit posts forces me to quote myself, and say that this line at the end is out of context. It is not true in all cases, but the inability to edit to put it back in the proper context within the message should be noted.

[SunEagle]

The inability to edit posts forces me to quote myself, and say that this line at the end is out of context. It is not true in all cases, but the inability to edit to put it back in the proper context within the message should be noted.

I share your frustration. I can only edit from my work computer and not this one (my home). --------------- It is a PIA and I hope it gets fixed soon.

[Richard_m]

hi all, thank you to everyone who expressed interest and replied to my post... I read every comment and took everything on board... I decided to invest in the tracer 40a and take my chances and it has paid off! I dis not expect the size of the mppt to be what it was though!

anycase I am now benefiting from 100% more power than I was originally getting from the pwm... right now at 9.17am it has jumped from 5.1a to 11.1 what a difference!

the tracer also has a multitude of options to moniter which I have become slightly addicted with haha.

any case if I knew how to upload photos on here using a phone I would have put a few pics of set up.

with this new unit I hope to maintain power to a 12 fridge and marine 12v freezer and have enough left for phones and minor tech.

[PNjunction]

... anycase I am now benefiting from 100% more power than I was originally getting from the pwm... right now at 9.17am it has jumped from 5.1a to 11.1 what a difference!

Awesome! Just note that has nothing to do with the Tracer brand being able to provide 100% or more than pwm, which in your case was terribly bad. For reference, what pwm CC were you using?

Quick tip for the notebook: "pwm" is actually used by the tracer in the "absorb" stage, like all mppt's do.

Glad it's working for you. If you application becomes critical, consider buying a spare Tracer to have on hand.