Outback FM 60 Controller dump load

[Gypsey_Kings]

So is this what's required...

[Gypsey_Kings]

With the AC version - How fast will the SSR be switching the rather heavy load of a 1KW element on & off...and more importantly, can the Sterling inverter handle this?

 

 

That was the question I had. Robbo thinks the unit is built to accommodate this, and Robbo seems to be familiar with the workings of the unit. Doing it with the 240V would certainly simplify things. If it was hooked up that way and didn't work well, the worst that would happen is that it wouldn't work well.

 

 

Sorry...I can't find this ... I see where he says the Outback Controller, SSR and Heater element can handle it, but I find no reference to say the Sterling Inverter can handle it...???

[MyLady]

Julynian has said that he keeps the inverter on 24/7, so that's not an issue.

 

However, if the batteries are full and the controller senses excess PV current then it switches on the aux load. If that load then draws current from the inverter, wouldn't that tell the controller that there is no longer any excess power and then the controller would shut of the aux load?

 

Isn't the idea that the dump load draws from the excess solar, not from the batteries? Those circuit diagrams may say that, but it's too late for me to interpret them reliably. Surely the purpose of a 'dump load' isn't to draw current from the batteries, but from the solar cells? The wiring would surely have to draw the dump-load current direct from the solar PV, not from the battery bank!

 

(It's late and I may well have missed something. If so please accept my apologies...)

 

R

[Paul G2]

So is this what's required...

That seems terribly complicated. Just a simple shunt (bypass) with an on/off switch would do the trick. If the relay happened to turn on at the same time the switch was on, it wouldn't make any difference. You'd just have the same current passing through two wires at that point.

 

Sorry...I can't find this ... I see where he says the Outback Controller, SSR and Heater element can handle it, but I find no reference to say the Sterling Inverter can handle it...???

You're right, he's talking about the controller, not the inverter. I was assuming he was talking about the entire "system". I'm not all that familiar with the "system" (controller + inverter), I was just interpreting the wiring diagram for Julynian.

 

Isn't the idea that the dump load draws from the excess solar, not from the batteries? Those circuit diagrams may say that, but it's too late for me to interpret them reliably. Surely the purpose of a 'dump load' isn't to draw current from the batteries, but from the solar cells? The wiring would surely have to draw the dump-load current direct from the solar PV, not from the battery bank!

 

(It's late and I may well have missed something. If so please accept my apologies...)

 

R

 

I was thinking the same thing as you, but Robbo thinks differently and I have no actual experience with this particular system so I'm not really in a position to debate the issue with him.

 

ETA Go back and look at post #53. That's how this started out and then somehow that morphed into being able to accomplish the same thing using the 240V from the inverter. Per my post #64 it seems like it would constantly switch on and off if wired to the 240V, but I'm truly just taking an educated guess.

Edited July 3, 2014 by Paul G2

[Robbo]

With the AC version - How fast will the SSR be switching the rather heavy load of a 1KW element on & off...and more importantly, can the Sterling inverter handle this?

 

 

The PWM is at 200hz (page 28 of the Outback FM manual). Looking through the OutbackPower Forum I can't see any issues to a inverter handling this type of setup. There's alot of knowledge on that forum so it may be worth a post too see what issues can/could occur with that setup.

[George94]

I have a Tracer, not an Outback, and a smaller PV array - 440 Watts. My plan is to replace the 3kW element with a 1kW, and then supply power to the element through a 3kW inverter. The idea is to use a timer that will supply power for a fixed time (say 5 minutes). The cycle will start again once the batteries are at full capacity.

 

Yes, this solution will take the majority of its power from the batteries, but not for very long. I would need to be able to adjust the time so that the batteries don't go below say 90% SoC. On a good day I would hope that the element would be drawing power about 25% of the time (between say 10:00 and 15:00. Less before and after). With Julynian's PV array,he would probably get power 50% of the time.

 

My problem is, how does the system know when the batteries are fully charged?

[Robbo]

I have a Tracer, not an Outback, and a smaller PV array - 440 Watts. My plan is to replace the 3kW element with a 1kW, and then supply power to the element through a 3kW inverter. The idea is to use a timer that will supply power for a fixed time (say 5 minutes). The cycle will start again once the batteries are at full capacity.

 

Yes, this solution will take the majority of its power from the batteries, but not for very long. I would need to be able to adjust the time so that the batteries don't go below say 90% SoC. On a good day I would hope that the element would be drawing power about 25% of the time (between say 10:00 and 15:00. Less before and after). With Julynian's PV array,he would probably get power 50% of the time.

 

My problem is, how does the system know when the batteries are fully charged?

 

On my research this has been recommended - http://www.morningstarcorp.com/products/relay-driver/

Available from http://www.shop.solar-wind.co.uk/acatalog/morningstar_solar_charge_controllers.html

 

This will do the same as the Outback AUX SSR option (as well as more options).

Edited July 3, 2014 by Robbo

[Robbo]

This element may be good for a DC load, http://www.ebay.co.uk/itm/24V-1000W-Standard-Fitting-2-25-BSP-Immersion-Heater-Dump-Load-/251563079043?pt=UK_ConsumerElectronics_Batteries_SM&hash=item3a9253f583

 

At 12v it's a 250watt load, if my calcs are right.

Edited July 3, 2014 by Robbo

[Ex- Member]

This element may be good for a DC load, http://www.ebay.co.uk/itm/24V-1000W-Standard-Fitting-2-25-BSP-Immersion-Heater-Dump-Load-/251563079043?pt=UK_ConsumerElectronics_Batteries_SM&hash=item3a9253f583

 

At 12v it's a 250watt load, if my calcs are right.

 

Hi Robbo, so will a 12v supply run that 24v element ok but just at a lower wattage?

[Robbo]

Hi Robbo, so will a 12v supply run that 24v element ok but just at a lower wattage?

Yep. Just at 1/4 the rated watts.

[George94]

 

On my research this has been recommended - http://www.morningstarcorp.com/products/relay-driver/

Available from http://www.shop.solar-wind.co.uk/acatalog/morningstar_solar_charge_controllers.html

 

This will do the same as the Outback AUX SSR option (as well as more options).

 

Thanks, Robbo, that's very interesting.

 

However, if I have read it correctly, with a non-Morningstar controller, its only input is battery voltage. So a voltage sensitive relay would presumably do what I need at lower cost.

 

What I don't understand is how battery voltage alone can tell you anything about SoC. A Smartgauge claims to be able to do so by tracking voltage over a period of time, but a VSR isn't doing that. It's just acting on the actual voltage at any moment.

 

Incidentally, my Smartgauge and my Tracer don't seem to get on very well. When I came back to the boat this evening I confidently expected the SG to be reading 100%. Not so. The SG said 86% and the Tracer said 100% (its battery state LED starts flashing when it thinks the battery is full). So it was only giving out around 5A despite the sun still being hot. Tricky. Which do I believe? And if I believe the SG, how do I persuade the Tracer that the batteries need more amps.

 

On a boat, you really only have two problems. Rust and batteries. And rust is so much easier to understand.

[peterboat]

Hi Julyian,

When I tried this with my panels it fried the 12v 300w immersion heater so now have it connected to the 240v 1kw immersion gets the water warm so it sort of works for me

 

Peter

[George94]

Hi Julyian,

When I tried this with my panels it fried the 12v 300w immersion heater so now have it connected to the 240v 1kw immersion gets the water warm so it sort of works for me

 

Peter

 

Did you connect it direct from the panels, or via the MMPT controller (assuming you have one)? And what voltage and watts do your panels put out?

[Grace and Favour]

 

Thanks, Robbo, that's very interesting.

 

However, if I have read it correctly, with a non-Morningstar controller, its only input is battery voltage. So a voltage sensitive relay would presumably do what I need at lower cost.

 

What I don't understand is how battery voltage alone can tell you anything about SoC. A Smartgauge claims to be able to do so by tracking voltage over a period of time, but a VSR isn't doing that. It's just acting on the actual voltage at any moment.

 

Incidentally, my Smartgauge and my Tracer don't seem to get on very well. When I came back to the boat this evening I confidently expected the SG to be reading 100%. Not so. The SG said 86% and the Tracer said 100% (its battery state LED starts flashing when it thinks the battery is full). So it was only giving out around 5A despite the sun still being hot. Tricky. Which do I believe? And if I believe the SG, how do I persuade the Tracer that the batteries need more amps.

 

On a boat, you really only have two problems. Rust and batteries. And rust is so much easier to understand.

On some boats, we can have three problems, rust, batteries, and wives.

 

I'll leave it to others, warlocks, soothsayers and spirits to guess which is the least easy to understand!

 

[Paul's Nulife4-2]

Where will we send the posthumous CWDF medal of 'Brave Posts'

G&F ?.

[Grace and Favour]

Where will we send the posthumous CWDF medal of 'Brave Posts'

G&F ?.

If you'd like me to receive it, may I suggest you arrange to burn it, and scatter the ash on the canals

[matty40s]

Wives are very easy to understand for those rich enough to understand them......

[Grace and Favour]

Ah! - But those rich enough are no longer so, when they have to finally admit they didn't 'really' understand them.

[Ex- Member]

Hi Julyian,

When I tried this with my panels it fried the 12v 300w immersion heater so now have it connected to the 240v 1kw immersion gets the water warm so it sort of works for me

 

Peter

 

Doesn't sound good, so I might go the AC route, maybe 300w was a bit too low.

 

how many watts is your array BTW?

[Paul G2]

 

Doesn't sound good, so I might go the AC route, maybe 300w was a bit too low.

 

how many watts is your array BTW?

 

Peter can correct me if I'm wrong, but it sounds to me like he is saying he hooked the 12V up to the 240V immersion heater.

 

The 24V heater that Robbo linked to should mitigate any worries about frying it as it would be oversized for your application, but not as oversized as the 240V heater.

[Ex- Member]

 

Peter can correct me if I'm wrong, but it sounds to me like he is saying he hooked the 12V up to the 240V immersion heater.

 

The 24V heater that Robbo linked to should mitigate any worries about frying it as it would be oversized for your application, but not as oversized as the 240V heater.

 

I didn't read it like that, i think he tried 12v it went bang and reverted to 240.

 

I do keep swaying to the lower voltage option though. I think I understand the AC version but the involvement of inverter being required does put me off. Reason being if it causes the battery level to drop, surely the time it takes to recover that loss is time the element won't operate.

 

I don't understand electricity unfortunately so it's all voodoo to me LOL

 

Like I don't understand how a 24v element can be run at 12v and quarter the wattage. It's an option I'm liking though.

[Paul G2]

 

I didn't read it like that, i think he tried 12v it went bang and reverted to 240.

 

 

 

Like I don't understand how a 24v element can be run at 12v and quarter the wattage. It's an option I'm liking though.

 

Hopefully Peter will chime back in and clarify.

 

Re. the latter - The element gets hot because of the resistance it poses to the flow of electricity through it. It's kind of like heat build up from friction if you want to think of it that way. The heater element is made of a metal that doesn't conduct electricity as well as normal conductors, so it gets hot as the electricity works to pass through it. What Robbo did was calculate the resistance, which would remain constant regardless of the voltage, and then used the resistance to calculate the wattage at 12V.

[George94]

 

I didn't read it like that, i think he tried 12v it went bang and reverted to 240.

 

I do keep swaying to the lower voltage option though. I think I understand the AC version but the involvement of inverter being required does put me off. Reason being if it causes the battery level to drop, surely the time it takes to recover that loss is time the element won't operate.

 

 

You are right, but it will have been putting more heat into the water while it was running. What matters is overall energy converted into hot water, and whilst the 230V option will be slightly less efficient, it's much easier to do than making another hole in your cylinder and running expensive high amp cable to it.

 

And if it isn't expensive high amp cable you will have voltage drop and cancel out some of the slight efficiency gain over the 230V option.

[Ex- Member]

 

Hopefully Peter will chime back in and clarify.

 

Re. the latter - The element gets hot because of the resistance it poses to the flow of electricity through it. It's kind of like heat build up from friction if you want to think of it that way. The heater element is made of a metal that doesn't conduct electricity as well as normal conductors, so it gets hot as the electricity works to pass through it. What Robbo did was calculate the resistance, which would remain constant regardless of the voltage, and then used the resistance to calculate the wattage at 12V.

 

Ok I see thanks Paul. 250w doesn't seem much although we're not expecting hot water just hopefully enough for a comfortable warm shower would suffice. I recall we have a 15 gal calorifier as well

 

You are right, but it will have been putting more heat into the water while it was running. What matters is overall energy converted into hot water, and whilst the 230V option will be slightly less efficient, it's much easier to do than making another hole in your cylinder and running expensive high amp cable to it.

 

And if it isn't expensive high amp cable you will have voltage drop and cancel out some of the slight efficiency gain over the 230V option.

 

Good point, more to think about LOL My KISS principle is reverting me back to the AC option. This has been giving me a head ache for 3 days now

Edited July 4, 2014 by Julynian

[MyLady]

Like I don't understand how a 24v element can be run at 12v and quarter the wattage. It's an option I'm liking though.

 

12V is half 24V so will only drive half the current through the element.

 

Power is voltage times current, so half times a half is a quarter. Simples!

 

(Actually, resistance goes up with temperature, so running at lower power you'll get slightly more current - but since an immersion heater is water-cooled anyway, the difference is likely to be very small )

 

Luv,

 

Roger