Navitron Renewable Energy and Sustainability Forum

Energy/Electricity Storage and Use/Grid Connection => Off-Grid, Batteries & Inverters => Topic started by: AlanM on June 13, 2012, 10:00:01 PM



Title: off-grid dump load query
Post by: AlanM on June 13, 2012, 10:00:01 PM
I have finally got my system together and working. 4kW pv feeding through samil grid tie into house consumer unit. Victron multiplus is providing grid to allow gti to work. House loads take first bite at power and then the victron takes any excess and charges 980ah forklift pack. Normally when the battery is full the victron will frequency shift which knocks out the gti, but that is a bit of a waste of potential power. ( and fits)
Any suggestions to create something clever which can switch on a dump load when the battery is full, and as i am off grid, i dont wish to hear of the waste of electricity to heat water, dont have the option to export.
Have enquired with smartgauge about their battery monitor programmable relay but as of now, they have not brought a 48v version into production although they did suggest it was in the process, but no timescale given.

Alan


Title: Re: off-grid dump load query
Post by: billi on June 14, 2012, 09:11:02 AM
Alan ,

Do  you use  the Victron s relay  already ?  It can be programmed  to turn on  extra AC consumers , when voltage rises  before the GTI  is switched off

The problem i see with the Victron  AC coupling idea is , that a proper  Battery charging  idea  seems not really possible .  But perhaps i am wrong

I guess  the optimal would be to add a Dump load controller like the Morningstar  Tristar    to grant a better charging idea .....  , but still use the Victrons relay to  try to consume nearly all power first on the AC side

Billi


Title: Re: off-grid dump load query
Post by: clivejo on June 14, 2012, 11:23:01 AM
I have finally got my system together and working. 4kW pv feeding through samil grid tie into house consumer unit. Victron multiplus is providing grid to allow gti to work. House loads take first bite at power and then the victron takes any excess and charges 980ah forklift pack.

How does the Victron know what is excess power?  Do you set the charge rate manually? Cant get my head around that at all!

I would assume, as billi suggests, the Victron will have a set of trigger relays which can be set for different battery levels.  I would use these to switch on a series of loads (immersion heaters, an AC unit to keep you cool in the hot summer months!)



Title: Re: off-grid dump load query
Post by: AlanM on June 14, 2012, 11:32:16 AM
How does the victron know? Dunno? Seems like magic! But it works, so best not to question too much!

Yes, the charge rate can be set with VE configure. As far i can tell, it has one programmable relay, but it (the victron) works by taking power in and putting it in the batts when excess, but switch a load on and it immediately supports the load with power from the battery, if needed, and then when load drops out, the excess power than goes into batts.

Thanks billi, will have to figure out how to programme the internal relay to do this, possibly set at just below 100%, that way if the dump fails the victron can still frequency shift to knock out the gti?

Alan


Title: Re: off-grid dump load query
Post by: clivejo on June 14, 2012, 11:50:04 AM
How does the victron know? Dunno? Seems like magic! But it works, so best not to question too much!

LOL My mother tried that answer with me many years ago, it only makes me more determine to find out why!

I'm guessing the Victron monitors and adjusts its 'grid' voltage to keep it within the preset range.  When the voltage is getting low it pulls power from the batteries, when too high it charges them.  Was this by design or happy coincidence?

Seems a bit strange to me, all that swapping DC-AC-DC-AC, must be considerable loses at each 'interface'.  Of course I have no idea of your set-up and distances, but is there no way to 'charge' directly from the PV panels?


Title: Re: off-grid dump load query
Post by: AlanM on June 14, 2012, 12:02:00 PM
 I suppose it senses the load and assists when needed, but dont know if this is done by voltage sensing. My reason for doing it like this is that my meter is on the gti output, rather than on the victron output. Therefore, metering what i generate, before battery losses, or conversion losses. Means having two inverters but there aren't any dc kWhr meters that are certified, so thats why the ac system, rather than dc and charging directly. It did take me a long time to figure out a system that would work and be eligible within the constraints of the fits regime.

Alan


Title: Re: off-grid dump load query
Post by: clivejo on June 14, 2012, 12:48:52 PM
It kind of misses the point of what the Feed In Tariff (FIT) is all about!!  But fair play to you, being free from Electric Companies grip must give a great sense of independence.

How do you fair in the winter months?  Do you have any kind of backup for when there is no sun?


Title: Re: off-grid dump load query
Post by: billi on June 14, 2012, 02:53:53 PM
Quote
Thanks billi, will have to figure out how to programme the internal relay to do this, possibly set at just below 100%, that way if the dump fails the victron can still frequency shift to knock out the gti?

yes  , i would say this will work, but it is  a bit guesstimating    the number under 100%   bike:


My relays  switches on an AC heater   when absorption Voltage is reached , cause until then one can expect that  Sun power is allowed fully into the battery , and  at that voltage set-point   Amps  into the battery will be reduced , while Voltage stays at that level , in a charge-controller setup ,  but in your case  i think the Victron, just switches the GTI off    :-\   and back on  (depending on HZ) and this is not propper charging , so to find that  off switching point  is important, that one   knows   when the relays should kick in ... to start more AC consumers

My AC heater has only 1500 watt  and my 4000 watt PV  normaly manages   to fully charge (charge controller) the battery, while heater is on



In your case   , beside the  FIT ,  i would recommend a  Dump Load controller  ,  to charge the battery right and the GTI stays on full blast , so first the Victron is dumping via AC  and then the dump load controller via DC  ( unfortunately this will be normally an (immersion ) heater



Billi


Title: Re: off-grid dump load query
Post by: clivejo on June 14, 2012, 02:58:51 PM
That's a good point billi makes.  Do your batteries ever get up to a decent equalization voltage?  Most need this every now and again to keep them health and firing on all cylinders!


Title: Re: off-grid dump load query
Post by: jonesy on June 14, 2012, 04:09:57 PM
Alan,
You should make one of EricW's dump controller see http://www.navitron.org.uk/forum/index.php/topic,16451.60.html (I should get a tenner each time I link this)  - but you need the burst control version.  If you put the CT around the Victron, the dump controller will sense any excess and dump it to whatever eg immersion heater, electric space heater etc. Mine is doing a good job of keeping my grid below 245V.


Title: Re: off-grid dump load query
Post by: billi on June 14, 2012, 07:03:33 PM
artful ,

can you explain ? .... to deserve this tenner  whistle

In Alans setup , there will be no excess  , that you can sense , all "excess" goes into the battery or Grid  inverter is shut down !

How do you  manage to sense  here ?


Again   , the off grid inverter  will switch an AC load on and off , depending on PV production,  with its own  relay and in relation to battery conditions ,  and i assume , that a charged battery is more important in an off-grid house  than  watering the garden with hot water  ::)


@Alan   , do you have a  big enough Victron Model, that can  absorb your max 4 kw PV in case you don't consume direct  ?  Is the internal charger big enough ?  You should really look into this !  Cause  , if the system is not balanced, it could cause troubles   sh*tfan:

Best regards Billi


Title: Re: off-grid dump load query
Post by: AlanM on June 14, 2012, 07:35:40 PM
Hi Billi,
the multi is the 5000 with 70amp charger, what sort of dump load controller would you suggest for switching dc loads on? I do wonder how the charging regime works when power is "backfeeding on the "ac-out", rather than on the "ac-in", in terms of absorption, bulk etc

Clivejo, "what is the point of the fits?", i no longer burn diesel for my power, that means less co2, (if you believe all that cr@p anyway), and i don't get any export, I only get the generation part, which is what i'm doing. As for voltages or winter, dont know yet, as system in its first week, but i have a mister Lister in storage to be added in later. 

Artful, thanks will have a look at that link

Alan


Title: Re: off-grid dump load query
Post by: billi on June 14, 2012, 08:39:15 PM
it is a 48 Volt setup ...so 70 A charger   sound good ....  i am not sure about  
Quote
I do wonder how the charging regime works when power is "backfeeding on the "ac-out", rather than on the "ac-in", in terms of absorption, bulk etc

I think , there is no proper  charging  at all  , when  PV is ac coupled to the ac out  of the Victron ( but ring their support to find out )


I personally  did test  the settings  , and tuned the internal charger down to 0  and charging volts low   , the settings are more for the AC Input  like a Generator or the Grid  , but when i attached my Waterturbine   AC coupled on the "ac-out" side , the  battery was charged  fine and the charger settings for the "AC-in"are overruled whistle

sorry picture description is in German  , but you can see on the right side, the internal charger set points  and on the left  you see battery voltage and Amps flowing into the battery   from my AC coupled waterturbine   so 6 A are flowing into the battery ( actually 12 A cause i have 2 Multiplus in parallel )  even the internal charger was set to 0 charging Amps  and Absorbtion voltage limit to 25 Volt , but actual battery voltage  is 29.1 Volt






So this is why, i think there is no absorption charge at all   , only bulk  and then Frequency related  on and off switching of the GTI , that sounds  like horror , but   on the other side  we  want to use every unit we can get , and this is where the dump load controller kicks in  , after the Victrons  internal relay for an AC Dump ....

So i think a Morningstar Tristar 60 A   (48 Volt )   should be sufficient , but you need as well the resistors /immersion elements  whistle  (i guess ca 200 GBP  (for  48 volt DC ones  and 150 for the Morningstar)

And use  the Victrons internal  AC relay first at say  57 Volt  Battery  with 1-2 kw extra AC load  = Grid tie Inverter stays online full blast , then at say 58 Volt the morningstar kicks in   and  takes the rest  = Grid tie Inverter stays online full blast

So  this seems in my eyes  a good solution of battery maintenance and use all in an off grid "AC-couppled" idea
If something fails ( i do not expect this)   the Frequency shift of the Victron  is still there to switch of the GTI

Regards Billi


Title: Re: off-grid dump load query
Post by: AlanM on June 14, 2012, 09:04:50 PM
Hi Billi,

No sign of a pic that you mentioned, was it a link or an attachment ?

I asked my battery supplier for the charging voltage and they said it should be 60v, (traction flat plate in cyclic mode), so can the morningstar trip voltage be set or is it a fixed value?

Your solution seems a sensible solution, thank you!
Will ring Victron and ask about the charging on back-feed

Alan


Title: Re: off-grid dump load query
Post by: billi on June 14, 2012, 09:23:39 PM
oh no pic....  i can see it  ,
anyway   here again

and my last post  edited   to see picture

(http://s7.postimage.org/f9h1b24xj/image.jpg) (http://postimage.org/image/f9h1b24xj/)


Title: Re: off-grid dump load query
Post by: Justme on June 14, 2012, 09:40:15 PM
Billi,

In normal usage I would also change the Victrons battery charge profile from adaptive & manually set the settings.

Adaptive just does not work well.


Title: Re: off-grid dump load query
Post by: AlanM on June 14, 2012, 10:36:21 PM
Hi Justme,
can you elaborate on the changes to the charge settings?

Billi, thanks for sticking the pic up
Alan


Title: Re: off-grid dump load query
Post by: billi on June 14, 2012, 10:50:05 PM
sure Justme  ,   picture is only there to show , that the internal charger configurations   are useless /ignored , when "AC coupling" is done  , with a Victron Multi


Title: Re: off-grid dump load query
Post by: AlanM on June 14, 2012, 11:13:39 PM
Hi billi,
had a look at the tristar, that looks like a good solution, as one of its 3 functions is to act as a dump controller. And max 60 amps at 58v will give me a sizeable dump.  Any suggestions for locating a fair priced one?  And dc immersions?
Seem to recall a thread a few weeks ago about these, will go and do a search on the forum to find out more.

Alan 


Title: Re: off-grid dump load query
Post by: billi on June 15, 2012, 12:18:34 AM
..... make sure you use the Victons AC Dump as well (first) .....   to avoid overload of the Morningstar  DC dump  sh*tfan:

I think  navitron are selling   the Morningstar as well ,    DC Dump elements  perhaps search    "emacandco"  on ebay 


Title: Re: off-grid dump load query
Post by: camillitech on June 15, 2012, 06:34:28 AM
Morning Alan,

I've used these people a few times http://www.tpfay.co.uk/ excellent quality in both AC and DC versions. The Victron will not charge the batteries 'properly' as it is only backfeeding any excess straight into them but I don't really think it's an issue. Certainly doesn't seem to be with me doing the same thing with an SMA and my Trace. It just keeps them at whatever 'float' you set the dumps at. If you want to EQ just set it higher for a few hours.

I believe there is some issue about the 'type' of charge damaging the batteries, some kind of short pulses via the inverter but I'm fecked if I can find the document this morning but it's around here http://currentgeneration.co.nz/site/current/files/Partial%20AC-coupling%20in%20Minigrids.pdf 

Good luck, Paul


Title: Re: off-grid dump load query
Post by: Justme on June 15, 2012, 09:12:37 AM
Hi Justme,
can you elaborate on the changes to the charge settings?

Billi, thanks for sticking the pic up
Alan

The adaptive setting alters the absorb phase relative to the bulk phase.

So a fast bulk = a short absorb when a fast bulk needs a slow absorb.

So put it on the fixed setting & then set the absorb times to match your bank & usage.


Title: Re: off-grid dump load query
Post by: stephendv on June 15, 2012, 01:42:23 PM
I believe there is some issue about the 'type' of charge damaging the batteries, some kind of short pulses via the inverter but I'm fecked if I can find the document this morning but it's around here http://currentgeneration.co.nz/site/current/files/Partial%20AC-coupling%20in%20Minigrids.pdf 

Yes!  Strongly agree with billi's advice to get a DC dump load controller like the morningstar, because the type of AC coupling that Victron offers doesn't do a nice clean absorb charge.  It's a constant on/off cycling which is what that document refers to.  Maybe that would be fine if you were using the Victron in a grid tie setup and it only ever needed to charge via PV once in a while when the grid went down- but it definitely doesn't look like a good solution for permanent off-grid charging.





Title: Re: off-grid dump load query
Post by: Eleanor on June 16, 2012, 12:12:02 PM
I'm sure this is a daft question but I'm going to ask it anyway  :P

What would the Victron do if you plugged the charger into the "grid" side and made the charger into an AC consumer and the "grid" is the generator?  :norfolk
Would it charge the batteries properly or just get totally confused and go off in a sulk  surrender:


Title: Re: off-grid dump load query
Post by: AlanM on June 16, 2012, 12:21:25 PM
Hi Eleanor,
not sure i understand, but there is no separate charger to plug in as a consumer. If the pv was connected to the  "ac in", it would not see grid and then would switch off.

If the generator is switched on, this does go in to the "ac in" and the charger operates in the correct way.

Have just tried to talk to the multi with the laptop, to use VE configure, but it doesn't seem to communicate. Just used the ethernet cable, but do i need something else as well...?
Alan


Title: Re: off-grid dump load query
Post by: billi on June 16, 2012, 12:28:51 PM
Unfortunately you need a Victron VE Interface MK.2B USB   adapter  whistle


Title: Re: off-grid dump load query
Post by: AlanM on June 16, 2012, 12:33:35 PM
Aha, i thought that was an adaptor if you only had a usb port. Just had a look, 55, "they're having a laff". Will see if i can borrow one from Caley marina...
Morningstar and dump immersions to add into system now,
Thanks, Billi,  :)


Title: Re: off-grid dump load query
Post by: Eleanor on June 16, 2012, 12:50:43 PM
Alan, as I said I'm sure it's a daft idea. What I meant is to leave the PV setup as it is with the GTI feeding into the AC output of the Victron. Can you run the generator and the PV at the same time and if so does the Victron do what it would normally do and send the generator output straight to the house and use what's left to charge the batteries? I was thinking that if you just connected the AC output into the AC input instead of the generator the Victron may charge the batteries properly. It just needs a "generator" and wouldn't know that it was connected to itself. Or would it? I don't know how the frequency shifting would be affected. Maybe a step too far  :norfolk

Do you have the interface http://cclcomponents.com/product.asp?ID=1566 (http://cclcomponents.com/product.asp?ID=1566) You may also need a serial to USB converter. Ah, Billi got there first again  :genuflect

From memory the sequence for connecting is to switch the inverter off, plug in connector, start up software, it should ask if you want to automatically detect the port to which I say yes. It should see the Victron and tell you to switch it on. Once, when the laptop was being fixed I spent ages connecting cables from inside to the tin shed so I could use the desktop. Got to the point where I shut down the Victron and realised there was no power for the  PC  wackoold


Title: Re: off-grid dump load query
Post by: AlanM on June 16, 2012, 01:02:34 PM
I see what you mean now, Have no idea if it would work though.
Idea of pv is to avoid generator use as much as possible. Perhaps, as Stephen mentioned not the ideal set up, but have been planning this for years, with wind being the main power source, and victron bought couple of years ago. The PV array is only a recent component as prices dropped and fits made it doable. Hence the large array, and i may not bother with wind, although i have a perfect spot here,  (7.2ms) its windier than some of the windfarms i work on!

Alan


Title: Re: off-grid dump load query
Post by: camillitech on June 16, 2012, 01:13:01 PM
:hysteria :hysteria
. Got to the point where I shut down the Victron and realised there was no power for the  PC  wackoold


 :hysteria  :hysteria in the bad old days of only 6 hours power a day from Mr Lister I would do that regularly, things like set the video before going to the pub, then turn off the genny as I left  ::)

PS, hows the mantis  ;)


Title: Re: off-grid dump load query
Post by: biff on June 16, 2012, 01:49:49 PM
Yo Alan,
       I did send you the email addy and phone number in a pm,did you get it?
                                                      Biff


Title: Re: off-grid dump load query
Post by: Eleanor on June 16, 2012, 05:13:48 PM
I've just been for a walk and had a laugh at my myself over the little Ponzi scheme I suggested - I think it might end up in situation where you could be using the batteries to charge the batteries. It's one of Billi's perptuum mobiles I think  ralph: It wouldn't be so bad if I hadn't had the same idea a few months ago and realised before posting. Must be my age  ::)

Alan, with just one 1kW of PV installed we haven't run the generator for about 3 months and there has only been a handful of days where the battery hasn't been fully charged. We use around 2 kWh/day. If we'd installed the PV earlier I'm not sure we would have bothered with another turbine but having said that the weather has been exceptional here and I'm sure we will be needing it later in the year.

Paul, glad I'm not the only one who does these silly things. I'm ashamed to say that I haven't even started the Mantis. I've been busy in the greenhouse moving things on but next week will be intensive ground preparation so they've got somewhere to go. I shall post some pics of progress  :garden


Title: Re: off-grid dump load query
Post by: AlanM on June 17, 2012, 04:18:18 PM
Hi Biff,
Yes thanks for that. Gave them a call and they can do a 1kw immersion at 48v, either short 11" or long 27". Yours are at a higher voltage  i seem to remember.

At the moment, the pv is giving me more than enough power, but the house is not particulary well staffed with electrical things, so heating water saves me heating it with wood, so should lower wood consumption somewhat.

Alan


Title: Re: off-grid dump load query
Post by: AlanM on June 18, 2012, 12:34:39 PM
Oh well, caley marina dont have one, they just use the dip switches,
Dont suppose any one has one a could borrow for a few days? I dont suppose it is  something that is needed much after the initial set up as long as the system stays the same?
Or is it in use often , to tweak things.
Can anyone enlighten me as to how often they use one, if they have it ?

Alan


Title: Re: off-grid dump load query
Post by: billi on June 18, 2012, 01:25:12 PM
Quote
Oh well, caley marina dont have one, they just use the dip switches,
Dont suppose any one has one a could borrow for a few days? I dont suppose it is  something that is needed much after the initial set up as long as the system stays the same?
Or is it in use often , to tweak things.
Can anyone enlighten me as to how often they use one, if they have it ?

Alan

I probably can post mine  ...... but expect postage costs from Ireland and return   are half the Product costs  whistle.....

And i am sure , at the moment you post it back to me , you will miss it

Buy one  ,   its handy to have .... and i use it quite often

its around 45 GBP  ???     I found one in Germany (Private sale ) for 30 Euro  .....  i can ask if still available ....

Billi

Billi


Title: Re: off-grid dump load query
Post by: AlanM on June 18, 2012, 02:13:11 PM
Had a look online, seems to be about 52GBP from a couple of places,(Kuranda, batt megastore) unless anyone knows somewhere better. Will have to get one then, oh well...

Thanks, billi, you're right about postage! Tell me more about the one in germany?

Alan


Title: Re: off-grid dump load query
Post by: billi on June 18, 2012, 02:37:48 PM
http://kleinanzeigen.ebay.de/anzeigen/s-anzeige/berlin/boote-bootszubehoer/u10638803

an ad   placed  start of may ,   not sure if still around .......    


or here German online shop

http://www.burmeister-elektronik.com/Inverter.html




Title: Re: off-grid dump load query
Post by: Eleanor on June 18, 2012, 03:25:49 PM
Alan, you can borrow ours if you want. If you PM your address I'll get it in the post and you will probably receive it on Weds  :crossed


Title: Re: off-grid dump load query
Post by: AlanM on June 18, 2012, 03:31:29 PM
Hi Eleanor,
Will send PM :) Thanks,
Billi, the shop was at 57, so not much diff from over here. Had a look at first link but my german not up to understanding the text :(

Will prob get one as well at some point though.
Alan


Title: Re: off-grid dump load query
Post by: Eleanor on June 18, 2012, 03:53:20 PM
There will now be a brief interlude while I go to the Post Office  tumble:


Title: Re: off-grid dump load query
Post by: Mike McMillan on June 21, 2012, 06:14:32 AM
Alan, I have one, live off grid in Osborne Bay, but working hull time oh yacht Eleonora this summer. Am around for the next few days before heading back to the med.  phone me 07973877686 and figure out a way to pick it up. Boat is alongside at Trinity wharf for the next 2 days...
Mike


Title: Re: off-grid dump load query
Post by: AlanM on June 21, 2012, 09:14:32 AM
Hi Mike, Thanks for offer, Eleanor has sent me her one so will reprogramme in next couple of days. Wheres Osborne bay btw?

Alan


Title: Re: off-grid dump load query
Post by: Mike McMillan on June 21, 2012, 09:37:24 AM
Are, IOW. Thought you were Alan from the island, to many Alan's!!