Replacing current 30A with MPPT controller - make sense?

[obiwancanoli]

Some of you have followed other posts of mine re: solar, and satellite, so hope this additional inquiry elicits similarly helpful info...

If I knew then what I suspect now, I'd have had the Dealer install an MPPT controller instead of then apparently standard 30A controller, despite my limited research and knowledge. Nevertheless, it would seem updrading to the MPPT would be a more efficient use of the additional panels I recently added.

I don't plan to add further panels, though if I do, it will be limited to a 4th 160W, 8.7A panel. Seems like I have enough to accomplish my likely dry camping goals. And yet, I want to make the best use of my charging system, in order to squeeze out the most amps in the shortest time, at minimal loss, and maximum efficiency.

Prices seem to be all over the map, and unfamiliar as I am, don't know what brands, features, or price ranges I should be considering, nor if it would, in fact, be worth the cost.

Thanks for your input!

[3_tons]

BFL13 wrote:
I didn't do nothing, and besides--nobody saw me! time2roll will now take any questions 🙂

Ha!! ....take note that I put his name in my Rolodex - lol

3 tons

[BFL13]

I didn't do nothing, and besides--nobody saw me! time2roll will now take any questions 🙂

[3_tons]

No problem, as I’d implied, my main focus was ‘for the uninitiated’, and only to relate my own hands-on experiences...I’m quite sure others may have had different experiences as well - nor would I wish to conflate workbench battery chargers with parallel PV controllers - this is just a minor nuance in personal experiences, neither of which should be dismissed....There’s no doubt about it, BF13 is a valuable resource here (along with many others!), and in soooo many regards, I’m smart enough to defer to his sage wisdom...

Let there be no confusion!!

3 tons

[pianotuna]

3 tons it was intended as a compliment.

[BFL13]

It was all time2roll's fault anyway! about 14 years back, he said I should try my new Vector 35 amper along with my then Vector 20 amper and i should get 55 amps. I did! So, if some is good more is better.

Here is a sequence of photos I posted about 10 years ago showing how it all works. Note that the 20 and 35s are 14.6 volts and the 40 is 14.8 volts, so it stayed on longest.

Amps tapered on the lower voltage chargers until they dropped out while the higher was still at full amps (40.4) then it started to taper as the bank continued to charge up.

I confirmed the total of the amps on each charger was showing on the Trimetric.

It works the same with solar controllers or whatever. You can't get exact same voltages by setting them due to wiring differences, but close enough to get the job done.

You can have alternator charging ( or 7-pin version) , solar charging, and even generator/converter charging all at the same time and it will work the same way. The alternator's voltage drops once you get going, so it could end up as the lowest voltage charger, not doing anything once the house batts reach its voltage while the other chargers do the work.

[BFL13]

https://www.rv.net/forum/index.cfm/fuseaction/thread/tid/29173556

Not sure what the argument is about. In the above, I did say something not quite right, but not sure that is what is the issue here.

In fact, the lower voltage charger does keep adding amps, but they taper as the battery's voltage gets closer to the lower charger's voltage. Once the battery voltage is the same as the lower charger's voltage it does no more amps and the remaining chargers with higher voltages than the battery is at (and rising) keep adding amps.

Some smart chargers won't start if you start them in the wrong order, but that is a different topic? You start the lower voltage smart charger first and it gets going , then you start the higher voltage charger. Now they both run and add their amps.

[3_tons]

pianotuna wrote:
Trust BFL13 to have "the goods"! So it is not just multiple battery chargers * grin *

Well, I must say that I’m a bit confused - blame it on a previous thread??:

https://www.rv.net/forum/index.cfm/fuseaction/thread/tid/29173556

Per BF13:

“They will add their amps ok at first in the morning but then it gets complicated. The ViewStar has that fixed EPSolar charging profile where it gets the battery to Absorb voltage (for AGM as set by you) then holds that for two hours then drops to 13.x (AGM setting) Float.

The Bogart controller is different ISTR you can set voltages? So set that one as close to the ViewStar charging profile as possible for the longest period in the day where they both have the same charging voltage.

Any time one has a higher charging voltage than the other, the lower voltage one will not put out any amps at all to the battery and you are on just the one.

EDIT-When I did that a few years ago, I was using two LandStars on the one battery set, so the two controllers were identical. Worked great. Maybe get a second ViewStar instead of the Bogart?

* This post was edited 01/31/17 10:43am by BFL13 * “.....



This IS closely similar to what had happened to me (until I found a workaround...), and note that this is why I cared to mention it to the WIDER Audience...A few imprudent keyboard clicks won’t erase what was this ‘real-world’ (non-theoretical) experience.

3 tons

[pianotuna]

Trust BFL13 to have "the goods"! So it is not just multiple battery chargers * grin *

[3_tons]

BFL13 wrote:

3 tons wrote:
“Controllers don't compete.”

A single stage controller mixed with a multi-stage controller can cause the multi-stage controller to prematurely switch to float mode, effectively cutting out that controllers harvest - Sometimes referred to as “dueling controllers”...For clarity, not a theoretical matter, this how it can happen...

3 tons

``````````````````````

Nope!

Say the multi-stage will drop to 13.6 two hours after reaching 14.6 (typical EP Solar fixed profile). Now start off with your single stage set at 14.6 in parallel.

"Prematurely" is only because it gets to 14.6 sooner with both on the job. It is not premature wrt to battery SOC.

Two hours after the batts reach 14.6, the multi will drop to 13.6 but the single stays at 14.6.

Whether this is good or bad "depends"

Got it, I’ll take that as “it’s a settled science”!

3 tons

[BFL13]

3 tons wrote:

obiwancanoli wrote:
Let me be clear here. My original post was entitled "REPLACING current 30 A with MPPT"... there was never any desire, plan, or curiosity about having BOTH controllers functional in tandem...

Great information from this exchange, thank you all... I'm all ears... or rather, eyes...

Obi, Thanks for clarifying...

3 tons

My set-up in the Class C ,has been

One 20a Tracer MPPT with a 255 panel
One 20a Eco-Worthy MPPT with a 275w panel, and
One 30a Solar30 PWM panel with three 100s in parallel.

They all add their amps just fine when I set their voltages the same.

I have now put the 255w and the Tracer in the Truck Camper we got, so i still have the PWM and MPPT in parallel for 575w and they add their amps just fine.

Too much bogus info flying around!!!! Do it for yourself and see what is true and what is not.

You do need a Trimetric or equivalent to see what is going on, when the individual controller displays say 10 amps each output, and the Trimetric says 28 amps to the battery (which means 2 amps are going to loads)

[3_tons]

obiwancanoli wrote:
Let me be clear here. My original post was entitled "REPLACING current 30 A with MPPT"... there was never any desire, plan, or curiosity about having BOTH controllers functional in tandem...

Great information from this exchange, thank you all... I'm all ears... or rather, eyes...

Obi, Thanks for clarifying...

3 tons

[BFL13]

3 tons wrote:
“Controllers don't compete.”

A single stage controller mixed with a multi-stage controller can cause the multi-stage controller to prematurely switch to float mode, effectively cutting out that controllers harvest - Sometimes referred to as “dueling controllers”...For clarity, not a theoretical matter, this how it can happen...

3 tons

``````````````````````

Nope!

Say the multi-stage will drop to 13.6 two hours after reaching 14.6 (typical EP Solar fixed profile). Now start off with your single stage set at 14.6 in parallel.

"Prematurely" is only because it gets to 14.6 sooner with both on the job. It is not premature wrt to battery SOC.

Two hours after the batts reach 14.6, the multi will drop to 13.6 but the single stays at 14.6.

Whether this is good or bad "depends"

It is bad if it happens when the battery bank acceptance rate at 14.6 is higher than the rated amps of the single and it is not charged up yet and there is daylight left to go.

It is ok if the single can do it all from then on that day.\

It is even possible that you get it all done with the single at 14.6 in the afternoon, and want to go to float , but the single won't. If you can't crank it down to 13.6, then you have to disconnect it and let the other one carry on at its 13.6 till dark.

[obiwancanoli]

Let me be clear here. My original post was entitled "REPLACING current 30 A with MPPT"... there was never any desire, plan, or curiosity about having BOTH controllers functional in tandem...

Great information from this exchange, thank you all... I'm all ears... or rather, eyes...

[3_tons]

“Controllers don't compete.”

A single stage controller mixed with a multi-stage controller can cause the multi-stage controller to prematurely switch to float mode, effectively cutting out that controller’s panel harvest - Sometimes referred to as “dueling controllers”...For clarity, not a theoretical matter, this how it can happen...

3 tons