Inverter issues

[Tracy D'arth]

Got it ! 

 

The inverter will have a neutral to earth connection internally.

Connecting that at the same time as the ring main to the charger input will cause the RCD on the ring main to trip.

Not installed correctly.

 

Took me while , I am not at my best.

[nicknorman]

12 minutes ago, Robbie G said:

Yes it seems to be fine when unplugged, Just when plugged in even with the socket switch off , 

I think this confirms it is an NE bond issue, since when it is plugged in but switched off, the live is not connected but the neutral and earth are connected. However I suspect the fundamental problem is that it isn’t installed properly, but I’ll refrain from further comment until you are able to let us know what we are dealing with (make and model).

[Robbie G]

Not sure probably my brother as it’s his boat, Unfortunately he his overseas and it’s not that easy to get hold of him, will probably have to get someone out to it 

[WotEver]

49 minutes ago, Jen-in-Wellies said:

Deleted , 'cause it was dumb.

Jen

So? This is CWDF after all ;(

[WotEver]

1 hour ago, Robbie G said:

Just a orange box to me...

I’ll take 10/1 on Sterling...

 

[ditchcrawler]

On 20/08/2020 at 17:46, Robbie G said:

Sorry not on the boat, Will try and locate a  name and model number, Just a orange box to me , Thanks for all your kind replies, Looks like it’s more complicated than I first thought. Oh well onwards and upwards 

Don't give up on it, come back to the problem when you have more information.

I am just wondering with the two sockets the OP seems to be using, if one is only live from the shore supply, like you would have say an immersion heater plugged into and the other is fed by the inverter/charger

 

[vicvdb]

Find this all very interesting as I have a low consumption fridge/freezer (212KWh pa - which works out at about 580 watts a day max, but with 25% duty cycle that probably no more than 150w in real terms) on start it draws around 350 watts and then looks like no consumption (as it's so low).

The inverter is 1,500 w pure sine wave Sterling device and the thing lasts for no more than five hours when powered from a bank of 3 x 150A leisure batteries which seems a bit off.

I know I've over-engineered the inverter and can probably do with something smaller, so here's my (stupid *) questions:

Anyone know what the quiescent state current draw of a Sterling 1,500W inverter might be (think that may be answered in this thread, but belt and braces, so looking for confirmation)?

 

I'm thinking that I can live with something much, much smaller in the inverter size - what size of inverter do people here use with regards to a simple fridge and the odd charging of technology.

Using the same question as above: how long do they get from their batteries?

Thanks (and hope this isn't too obtuse a set or queries,

 

V

* RSM once told me, "The only stupid question is the one you didn't ask!"

 

 

[nicknorman]

The static power consumption of inverters is very dependant not only on the make, but also on the specific model. Some Sterling inverters are renown for drawing about 4A (48w) static, but others are better.

 

Also it would be a mistake to think that static power consumption of an inverter is related to its maximum power rating. Some small inverters are very thirsty, some large ones very economical. Our Mastervolt 2500va inverter uses 9 watts (0.75A) doing nothing, which is why we leave it on all the time.
 

if your fridge freezer really does take 580 watt hours a day, that is around 50Ah, which is a fair bit but obviously well within the capabilities of 450Ah of batteries for a day or two. Most likely problem is that the remaining capacity of the batteries is a lot less than you think it is, and/or they are not being charged properly. Do you have any sort of proper battery monitor?

Edited August 26, 2020 by nicknorman

[Tony Brooks]

38 minutes ago, vicvdb said:

Find this all very interesting as I have a low consumption fridge/freezer (212KWh pa - which works out at about 580 watts a day max, but with 25% duty cycle that probably no more than 150w in real terms) on start it draws around 350 watts and then looks like no consumption (as it's so low).

The inverter is 1,500 w pure sine wave Sterling device and the thing lasts for no more than five hours when powered from a bank of 3 x 150A leisure batteries which seems a bit off.

I know I've over-engineered the inverter and can probably do with something smaller, so here's my (stupid *) questions:

Anyone know what the quiescent state current draw of a Sterling 1,500W inverter might be (think that may be answered in this thread, but belt and braces, so looking for confirmation)?

 

I'm thinking that I can live with something much, much smaller in the inverter size - what size of inverter do people here use with regards to a simple fridge and the odd charging of technology.

Using the same question as above: how long do they get from their batteries?

Thanks (and hope this isn't too obtuse a set or queries,

 

I think your assumption is wrong. A per annum consumption is just that 212kWh per year so the true daily consumption will be the 580 watts. The per annum figure should be the total consumption, the duty cycle does not come into it.

 

Your 450Ah batteries should really only be relied upon to supply 225Ah when new if you want a long life. 580W from an inverter equates to roughly 58Ah from the batteries so there is no way you shoudl only be getting 5 hours before the inverter complains of low voltage. I think that you have probably been consistently under charging the batteries and over discharging them so now they only have a fraction of their original capacity.

 

What battery monitoring equipment do you have and how do you use it?

 

 

 

[nicknorman]

580 watt hours.

[Tony Brooks]

Just now, nicknorman said:

580 watt hours.

so still about 58 Ah from the batteries.

[GUMPY]

1 hour ago, vicvdb said:

I'm thinking that I can live with something much, much smaller in the inverter size - what size of inverter do people here use with regards to a simple fridge and the odd charging of technology.

 

You will be lucky to find an inverter less than 1kw that will deal with the start up current of the fridge.

Even then it will likely have to be an LF inverter (heavy and with a transformer) rather than a HF inverter (light and portable).

About 5 years ago I spent many weeks testing low power inverters to find one that started my fridge, there were none below 1kw.

 

[GUMPY]

2 hours ago, vicvdb said:

Using the same question as above: how long do they get from their batteries?

300Ah and a Victron 1600 I get 1-1.5 days running the fridge etc. That's why I fitted 500w of solar.

[WotEver]

7 minutes ago, Loddon said:

300Ah and a Victron 1600 I get 1-1.5 days running the fridge etc. That's why I fitted 500w of solar.

Plus, presumably, you have effective battery monitoring to check their charge status?

[vicvdb]

Kwh pa = 212

 

212/12 (which gives approx Kw hours per month) = 16.7 Kwh per month

16.7/30 (gives Kw hours per day) = 589 w hr per day (some look at the 25% duty cycle and come to a figure of 147 watts per hour)

 

Now some will  look now divide by 24 to give Kwh per hour = 24.5 

Of course these figures are based on the approximation that 1kw is about 4A in ac world.

Having worked on early inverters (a change from 440 and 150V dc and 33kV) we experiments on waveform design and quiescent currents (which are, as someone said, all about efficiency) and the effect of loading (not a linear game). I was expecting a low stand by current (<2 A at worse case scenario).

I have three brand new 150Ampere hour batteries in parallel and find that they last some five hours when powering the inverter - and Now I'd expects more than this.

 

The batteries are on a discharge/charge cycle and are generally run on an electronic sensed trickle charge during the season (whenever that was this year thanks to Covid).

I am going to take a proper (old-fashioned battery tester with a nice resistive load built in) and check the things but I'm also wondering if the inverter has gone a bit off too.

Just doodling in head and tying to see whether I try one of the few lower wattage inverters I have in a box (meant to give them away and yet they remain!!!)  and see how  long they take to run down batteries on quiescent state, then recharge and run on load  OR run sterling and repay the last process. 

Thanks for comments - all grist to the mill ?

 

Monitoring is pretty much there - have been toying with some of the more Gucci tools for the tech panel, but need to finish the rebuild before extending into that area.

Things are pointing to a duff cell (which I will check) and a poorly inverter (which is another possibility - is there a life to these things in a damp nautical setting???).

Oh what fun ?

Thanks again,

 

V

[GUMPY]

17 minutes ago, WotEver said:

Plus, presumably, you have effective battery monitoring to check their charge status?

If you call a Smartgauge effective then yes.

I want a Balmar SG200 but they dont seem to be generally available in the UK.

 

ETA

I realise the Smartgauge doesn't read properly when solar is on so I only take readings after dark

Edited August 26, 2020 by Loddon

[WotEver]

6 minutes ago, Loddon said:

If you call a Smartgauge effective then yes.

I want a Balmar SG200 but they dont seem to be generally available in the UK.

I do call a Smartgauge effective, yes

 

The Balmar isn’t available in the UK because they’d have their pants sued off them if they tried. Nothing to stop you buying one in the US though

[Alan de Enfield]

13 minutes ago, vicvdb said:

I am going to take a proper (old-fashioned battery tester with a nice resistive load built in) and check the things

Is that the 'thing' with the two 'spikes' you jab onto the battery terminals ?

 

It will show you nothing.

 

You are talking about long, slow discharges from domestic batteries.

 

You need to get the batteries FULLY charged such that the charge rates is about 1% of capacity and has held at 14.4v+ for over an hour.

Connect a known load (old style car headlight 55 watt is good) and time how long it takes to get down to 12.2 volts,

 

you then have a known capacity to ~50%

 

Multiply that x2 and you have the total capacity.

Edited August 26, 2020 by Alan de Enfield

[WotEver]

14 minutes ago, vicvdb said:

Of course these figures are based on the approximation that 1kw is about 4A in ac world.

No they’re not. A kWh is a kWh whatever the voltage happens to be. 

[nicknorman]

14 minutes ago, vicvdb said:

Kwh pa = 212

 

212/12 (which gives approx Kw hours per month) = 16.7 Kwh per month

16.7/30 (gives Kw hours per day) = 589 w hr per day (some look at the 25% duty cycle and come to a figure of 147 watts per hour)

 

Now some will  look now divide by 24 to give Kwh per hour = 24.5 

Of course these figures are based on the approximation that 1kw is about 4A in ac world.

Having worked on early inverters (a change from 440 and 150V dc and 33kV) we experiments on waveform design and quiescent currents (which are, as someone said, all about efficiency) and the effect of loading (not a linear game). I was expecting a low stand by current (<2 A at worse case scenario).

I have three brand new 150Ampere hour batteries in parallel and find that they last some five hours when powering the inverter - and Now I'd expects more than this.

 

The batteries are on a discharge/charge cycle and are generally run on an electronic sensed trickle charge during the season (whenever that was this year thanks to Covid).

I am going to take a proper (old-fashioned battery tester with a nice resistive load built in) and check the things but I'm also wondering if the inverter has gone a bit off too.

Just doodling in head and tying to see whether I try one of the few lower wattage inverters I have in a box (meant to give them away and yet they remain!!!)  and see how  long they take to run down batteries on quiescent state, then recharge and run on load  OR run sterling and repay the last process. 

Thanks for comments - all grist to the mill ?

 

Monitoring is pretty much there - have been toying with some of the more Gucci tools for the tech panel, but need to finish the rebuild before extending into that area.

Things are pointing to a duff cell (which I will check) and a poorly inverter (which is another possibility - is there a life to these things in a damp nautical setting???).

Oh what fun ?

Thanks again,

 

V

Hmmm well bearing in mind you seem to have some electrical knowledge, I’m a bit surprised you don’t understand the difference between power and energy!
 

If 580 watt hours is the daily energy consumption then the average power consumption is 24 watts (around 2A at 12v). If the duty cycle is 25% then the running consumption is 96w which is say 9A. But the peak startup load for the compressor motor will be up to 10 times that, which is why one can’t select an inverter to run a fridge based on steady state running consumption.

 

As we’ve said the fault lies with the supply to the inverter, either resistive wiring/ connections, or low capacity or undercharged batteries.

[Tony Brooks]

I note that you only assert the battery monitoring "is there" but decline to tell us what it is or if you did I must have missed it. The more popular battery monitors lie and encourage boaters to over discharge, undercharge and ruin their batteries so what do you have and how do you use it?

 

You might be right about a duff cell but then you should have other symptoms like local hating  in parts of the battery, excess gassing in individual cells or individual cells a lot dryer than the rest.

 

Are you aware than many/most multi-stage chargers drop to float far too early to get the batteries fully charged. As soon a sit drops into float turn it off for a few minutes and then back on. See how long it stays in absorption, I bet it will be far longer than one would expect if the batteries really were fully charged.

 

[WotEver]

18 minutes ago, vicvdb said:

I have three brand new 150Ampere hour batteries

How new is ‘brand new’?  Obviously, from your post you’ve had them for some days at least.  If you’ve been under-charging them it doesn’t take long for the capacity to drop markedly. 

[vicvdb]

So many things (power and energy - think I do know difference, though various tutors and supervisors might disagree - probably lost in the rushed scribbles as run in and out  sorry, textual skills rather than electrical and physics (which I always thought were the same).

Agree about the over-discharging and under-charging, I've found that to be a major culprit in problems friends have had.

'Brand new' is never the case as many boat yards have them in stock for months - so 'new' is best label and thats three weeks (but will check manufacture),.

Was going to connect toy from traction and heavy-current days which loads and plots on graphical display (I think I know where one still resides) but will go check charging again).

Sorry for dashed off bits but the world is having a day where I am and so this is a pop in, sniff, think, and run back out.

I'm hedging it's batteries but don't have spec' sheets for inverter and wondering whether it's also part of the issue (if not has to be 'fridge as that's all left :-)).

Thanks for the grist - getting me thinking.
V
 

[Tony Brooks]

It seems more than one of us here "hedge" (think) its a charging-over discharging problem and you still have not told us how you are monitoring the bank and what your charging procedure is.

 

Until you decide to start giving up actual monitoring and charging data I can't see anyone can be much more help to you. You may be correct that its a battery problem but it could just as well be a charging/discharging problem and guessing won't help resolve it quickly.

[vicvdb]

Sorry Tony, keep dropping in between manic work life and obviously stepping on the cracks.Wwill leave this thread and stop frustrating you and probably others).

Charging, when not running is a purpose designed digital black box with when checked fully charges. Running, I have a rewound alternator which is seeing batteries @ 14.4 volts (on Sterling and Fluke DMM). Monitoring is bog standard Volt meter (which show's charging).