Solar dump.

[Swanky pirate]

As I live off grid instead of running the engine for hot water was thinking about a solar dump has any one fitted one and are they useful.

[Laurie Booth]

What is a solar dump?

 

[rusty69]

Lots of people on the 12V boating group on facebook seem to have sucessfully achieved it. I think there is even a description of how to do it in the files section.

12 minutes ago, Laurie Booth said:

What is a solar dump?

 

Its when you use your elsan out on the towpath on a sunny day Laurie.

Edited July 17, 2023 by rusty69

[1st ade]

26 minutes ago, Laurie Booth said:

What is a solar dump?

 

It's an option which - when Solar is generating more power than your batteries can absorb - you divert the excess electricity into heating the water (Immersion Coil in the calorifier or similar) - even if it doesn't achieve full temperature it saves some energy when the proper heating kicks in.

 

"Dump" as in "I've got more solar energy than I know what to do with, so I'll dump it somewhere..."

[magnetman]

I wondered about using one of these in a beer keg wrapped with insultation. 

 

It would need to be on a suitable timer switch.

https://www.ebay.co.uk/itm/144548953871

[blackrose]

2 hours ago, Swanky pirate said:

As I live off grid instead of running the engine for hot water was thinking about a solar dump has any one fitted one and are they useful.

 

There's another recent thread on this somewhere. Bimble Solar sell 12v 300w solar dump kits and they kindly put me in touch with their supplier as I had a few questions.

 

As it turns out the main issue was the question I hadn't thought of and the supplier was very honest and told me that trying to remove a mains immersion heater from a tank that had been there for some time might not be straightforward and could result in rupturing the tank if you're not very careful. He told me to carefully try to take mine out before ordering the 12v dump load kit from Bimble. 

 

It kinda put me off so I haven't bothered yet...

 

2 hours ago, 1st ade said:

"Dump" as in "I've got more solar energy than I know what to do with, so I'll dump it somewhere..."

 

And "Load" in that it operates directly from the 12v load terminals of your MPPT. 

[ditchcrawler]

38 minutes ago, blackrose said:

 

And "Load" in that it operates directly from the 12v load terminals of your MPPT. 

I don't think you will find that is such a good idea for a few reasons, one being you will be powering the heater circuit from your batteries bypassing your isolator switch. 

[Tony Brooks]

47 minutes ago, ditchcrawler said:

I don't think you will find that is such a good idea for a few reasons, one being you will be powering the heater circuit from your batteries bypassing your isolator switch. 

 

I thought the "load", as opposed to "Batter" terminals on the controller was to prevent that happening. No solar, so no output on Load.

[magnetman]

2 minutes ago, Tony Brooks said:

 

I thought the "load", as opposed to "Batter" terminals on the controller was to prevent that happening. No solar, so no output on Load.

The smaller Victon MPPT (20a variety) have a load bus which can be programmed via the app to come on and off according to battery voltage. 

 

There isn't a load bus on the 30a or 50a type.

 

I think the bigger ones have it but it needs a separate relay to switch the current. 

 

It could be informative to play with a cheap low wattage bucket warmer. 

[DShK]

I was looking to do this a smart way with my lithium batteries, second AC output and programming Victron devices with a raspberry pi. I concluded that there are too many variables to allow a system to potentially drain your batteries without input. I decided to just do it manually - if I see my batteries are basically full and the sun looks to be blazing all day, I turn on my hot water heater (or other heavy user).

 

Perhaps it's easier on a lead acid setup, turning on and off repeatedly based on voltage? I don't think lithium would like being micro cycled at high SoC like this, would LA be okay with this?

Edited July 17, 2023 by DShK

[Tony Brooks]

5 minutes ago, magnetman said:

The smaller Victon MPPT (20a variety) have a load bus which can be programmed via the app to come on and off according to battery voltage. 

 

There isn't a load bus on the 30a or 50a type.

 

I think the bigger ones have it but it needs a separate relay to switch the current. 

 

It could be informative to play with a cheap low wattage bucket warmer. 

 

I don't think the OP is using a Victron, I think he said Epvar or something similar, that may well have load connections.

[blackrose]

1 hour ago, ditchcrawler said:

I don't think you will find that is such a good idea for a few reasons, one being you will be powering the heater circuit from your batteries bypassing your isolator switch. 

 

Why would connecting directly to the MPPT be powering the immersion from your batteries? Surely it's doing the opposite and powering the immersion directly from the panels via the MPPT. I think you may have misunderstood what's being discussed.

 

1 hour ago, Tony Brooks said:

 

I thought the "load", as opposed to "Batter" terminals on the controller was to prevent that happening. No solar, so no output on Load.

 

Yes that's right.

 

57 minutes ago, Tony Brooks said:

 

I don't think the OP is using a Victron, I think he said Epvar or something similar, that may well have load connections.

 

I have load connections on my Epever Tracer, but it's the 60 amp version. I don't know exactly how it works as I've never done it, but my understanding is that it once the batteries are charged the MPPT simply directs any spare capacity that's not being used from the panels to the immersion. I guess in practice it's not quite as simple and some programming of the MPPT is required.

Edited July 17, 2023 by blackrose

[DShK]

13 minutes ago, blackrose said:

 

Why would connecting directly to the MPPT by powering the immersion from your batteries? Surely it's doing the opposite and powering the immersion from the panels via the MPPT?

 

If you're referring to the "load output" on a victron MPPT - they aren't really designed for this application. 15/20amp output limit - not really enough to heat water. Mostly just as an inbuilt "battery protect" feature for small systems is my understanding. Can't speak for other systems though, but can't imagine they are much different.

 

I think the question is - is it possible for an MPPT to "detect" "spare capacity"? After all it's the batteries which "pull" the current, but how can it possibly know it has more available to it beyond that?

Edited July 17, 2023 by DShK

[Swanky pirate]

Thanks for your thoughts guys on the solar dump I will get an electrician to fit it 

[Swanky pirate]

Just find a video on it the canal boat well deck diaries they have fitted solar dump it's very interesting thanks guys 

[GUMPY]

Most load outputs wont power anything like an immersion heater this would mean using a contactor to switch the immersion on. Contactor should be wired on the boat side of the isolator switch so the isolator will have to be a good one. 

If it was me I would just set the load output to switch a contactor controlling a 230v immersion from the inverter.

 

 

[blackrose]

43 minutes ago, DShK said:

 

If you're referring to the "load output" on a victron MPPT - they aren't really designed for this application. 15/20amp output limit - not really enough to heat water. Mostly just as an inbuilt "battery protect" feature for small systems is my understanding. Can't speak for other systems though, but can't imagine they are much different.

 

I think the question is - is it possible for an MPPT to "detect" "spare capacity"? After all it's the batteries which "pull" the current, but how can it possibly know it has more available to it beyond that?

 

No I wasn't referring to a victron MPPT. Mine is a 60 amp Epever. I don't know what the maximum load output is.

 

You ask if an MPPT controller can detect spare panel capacity, and I don't know exactly how it works, but it's the MPPT that effectively shorts or decouples the panel voltage from the battery voltage so it must be communicating with the panels.

 

13 minutes ago, GUMPY said:

 

If it was me I would just set the load output to switch a contactor controlling a 230v immersion from the inverter.

 

What kit would one need to do that?

Edited July 17, 2023 by blackrose

[GUMPY]

13 minutes ago, blackrose said:

What kit would one need to do that?

Just a 16amp Double pole relay/contactor that has a 12v coil.

Finder make them amongst others I think the  part# is  22.22.9.012.4000 

You can get them that fit in a consumer unit but I cant find one at present. Farnell or RS would be the best bet

[ditchcrawler]

51 minutes ago, Swanky pirate said:

Thanks for your thoughts guys on the solar dump I will get an electrician to fit it 

In that case you will probably fall at the first hurdle. First problem finding an electrician who understands boats, secondly one who understands what you are trying to do. This is the sort of thing normally done DIY by geeks using PMW controllers to control the amount of power going to the heater, looking at battery states of charge and switching accordingly. If I was going to do it I would use a 1Kw 230 volt immersion heaater and switch the AC output from my invertor, much easier that switching 50 to 100 amps DC smaller cables etc.

[Swanky pirate]

Thanks ditchcrawler at the moment I run the engine or run My generator also got a ecoflow power bank to run the emerson but using the ecoflow it takes a lot out of it will look at options thanks all.

[magnetman]

6 hours ago, Laurie Booth said:

What is a solar dump?

 

 

A massive landfill site where out of date photovoltaics go on account of nobody being prepared to recycle them. 

 

The size of Wales. 

[Swanky pirate]

I guess your talking about the lfp battery yes it will be a problem it's the way things are going though I try to be as green as I can .

[rusty69]

3 hours ago, DShK said:

I was looking to do this a smart way with my lithium batteries, second AC output and programming Victron devices with a raspberry pi. I concluded that there are too many variables to allow a system to potentially drain your batteries without input. I decided to just do it manually - if I see my batteries are basically full and the sun looks to be blazing all day, I turn on my hot water heater (or other heavy user).

 

Perhaps it's easier on a lead acid setup, turning on and off repeatedly based on voltage? I don't think lithium would like being micro cycled at high SoC like this, would LA be okay with this?

I got. a victron mppt this week and a raspberry pi (actually, I got 11,don't ask). God my head hurts. 

[Swanky pirate]

Lol 11 but about the lfp battery it's a big problem all the electric cars use them and the new narrow boats dont know the answer. 

[TheBiscuits]

33 minutes ago, rusty69 said:

(actually, I got 11,don't ask). God my head hurts. 

 

That normally hurts your ears ... 11 is louder than 10!