The last discussion was way above me, but I have always understood that one controller is better.
Is it possible to add another input plug into your 30A controller so you can plug into that on a longer lead.

A PWM and a DC to DC controller will work together without much problem. The DC to DC does have sort of an MPPT controller, but more a boost unit than a buck control. In other words, more designed to increase the input voltage rather than reduce the input voltage and increase the amps coming out. For this reason the DC to DC units are not very efficient as a solar regulator, but I guess something is better than nothing. They do function well as a voltage booster from the start battery/alternator to bring the voltage up high enough to get a good charging current into the hose battery. The efficiency is not near as critical for this function because the alternator can generally produce more than the DC to DC charger requires, so an additional 10% loss through the unit is acceptable.
As far as the solar side of the DC to DC charger, that 10% is really noticeable because the solar output is limited to start with so any additional losses show up.

T1 Terry

Terryt wrote:

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[1]I read the post just below a number of times but it ended up way above my ability to comprehend. I often have two controllers working at the same time. A morningstar 30a PWM looking after my roof mounted panels (400w) and a DC DC charger with solar input that I connect a 140 watt portable panel to.

[2]I keep reading that one panel may get confused because it reads the voltage the other panel is producing and thinks battery is charged so it shuts off. What confuses me is the controllers are both connected to the same battery (ies) so I would expect they would be reading the same voltage. What makes only one of them shut up shop? 

[3]What I am wondering is am I getting any value out of carting my portable panel around (apart from being able to have it away from a shady spot)?

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 Hi Terry t

Yes, it can end up being confusing. Especially when someone attempts to make it so 

But why are you connecting the portable panel to the DC /DC charger input?? unless things have changed ,the Dc /DC charger only accepts one source at any time

if the panel has it's own regulator, .you gain  nothing by putting it's output through the DC /DC charger 

[1]  If both panels or the panel & dc charger are connected to the battery ,the simple explanation is both sense the battery voltage. They cannot & are not really interested in the input voltage except,that it must be high enough [above the battery voltage ] for the regs to turn "on",

 [2]Of course they will both read the same voltage,if both have the same voltage drop between them  under load at the battery or have battery voltage "sense cables," 

However , while they will work happily together while in bulk mode ,they may be become a little confused when in float mode   simply because it would be very unlikely that they have exactly the same set points

But as the battery is fully charged /or near fully charged ,that is very unlikely to ever be a real problem

[4]If your portable panel has still has the regulator on the panel ,it will indicate the battery is charged before it actually is ,shutting the panel down . Best to either remove the reg from the panel , if possible , & refit it as close as possible to the battery 

-- Edited by oldtrack123 on Friday 1st of February 2019 02:15:26 PM

Hewy54 wrote:

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The last discussion was way above me, but I have always understood that one controller is better.
Is it possible to add another input plug into your 30A controller so you can plug into that on a longer lead.

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 A longer lead ,with the regulator still on the panel  actually is not a good idea.

It means the Battery voltage will not be correctly sensed ,possibly being never fully charged

That is why it is best to have the regulator as close as possible to the battery[ unless the regulator has a separate voltage sense lead for direct connection to the battery

For LA batterreries , it is generally recommended that ,without a sense lead , the cable voltage drop, between battery & regulator, should be less than 0.25V 

Hewy54 wrote:

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Sorry I did not make it clearer for you oldrack.
I was suggesting that a longer lead WITHOUT THE CONTROLLER straight to the common regulator maybe better.
In your vast knowledge, could you please tell me where i am wrong, as I have used this system for many years with no problems.

Sorry ,it seems I did Misunderstand your  post

Nothing wrong with the above

-- Edited by oldtrack123 on Sunday 3rd of February 2019 01:18:53 PM

JURDO wrote:

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Wow was that stuff intense.

I thought I might have known a little about this subject but obviously I haven't got a clue.

I have a campervan with 200 watts in panels on the roof which is wired directly into the battery through a regulator in the living area of the camper for my day to day information and this indicates that I am pumping around 13.7 volts on a good day out in the sun while driving around.

when I stop for a while I have 250 watts in portable panels which I place outside in the sun and these panels have their own regulator on the back. These panels have their own plug on the outside of the camper and are wired directly onto the pos and neg battery terminals.

there is a seperate input plug for 240 volt power on the outside of the camper.

my question after reading the host of comments previously is, do I need a regulator on the portable panels or not?

See I said I haven't got a clue but I found it all very interesting and I am learning more the more I read on the subject.

Thanks for any help you can provide

Regards

Bob

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 Hi Bob

Provided the combined output of the panels does not exceed the current rating of the controller on the fixed panels,  it would be Ok to just remove the portable one  & use the fixed one, with the proviso that the panels all have the same MPP voltage & you have good heavy leads on the portables that limit the amount of voltage drop in the cables[ Size will depend on length]

 Having the controller on the portable panels is not the best way, as it is not sensing true battery voltage.If you can carefully remove it would be better in the van & as near as practical to the batteries.

 

PS I hope you have fused that circuit for the portable panels as close as possible to the battery bank, Fuse rating no higher than the cable current rating Size

-- Edited by oldtrack123 on Wednesday 3rd of April 2019 05:05:39 PM

Wrote on another thread that our Roadtrek has two different voltage solar panels due to the real estate of roof. One is a 100 W 12 V nominal and the other is 315 W so the voltages were not compatible. Son just used two controllers to go to a 12 V nominal LFP battery suite.

Reed and Elaine (watching it snowing again)

Peter_n_Margaret wrote:

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Julian is successfully using 4 separate (identical MPPT) controllers with his 12 @ 135W panels (10 fixed plus 2 portable). He is not using any special configurations to do that, despite what has been suggested.
I intend to have 880W via a PWM controller plus 440W via an MPPT controller. I will let you know how that goes.
Cheers,
Peter

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Ummm...... Julian actually demonstrated to me how the master control worked to control all the MPPT controllers the last time we were at Taggerty

 

T1 Terry