Batteries and living aboard

[boathunter]

There's a table in this Mastervolt gel battery manual, page 9-ish, that gives you the info you need.

 

http://images.mastervolt.nl/files/ManualGEL12V141203ALL.pdf

 

Usefully, it also gives you the instantaneous voltage at various discharge currents that you don't want to go below.

Thank you again, I didn't find that. Did you notice the SOC accuracy for the figures they quote? +/- 20%. And I wonder if they mean a % of a %, or literally 20% ie 50% could be 30-70%?

Either way, not terribly accurate.

[nicknorman]

Thank you again, I didn't find that. Did you notice the SOC accuracy for the figures they quote? +/- 20%. And I wonder if they mean a % of a %, or literally 20% ie 50% could be 30-70%?

Either way, not terribly accurate.

No not brilliant but I guess there is some temperature effect. Not to sure about the +-20% - clearly if the voltage suggests 100% SoC it couldn't actually be 120%! Perhaps if you get a good figure for the fully charged voltage, you could work out the error / difference and apply that to the lower voltages?

 

Anyway the more you discharge it the more accurate your assessment will be so why not take it down to the final voltages mentioned - not particularly good for batteries to go that low but I doubt it will hurt as a 1-off.

Edited August 4, 2016 by nicknorman

[boathunter]

I will do some more experimenting. There is a temp sensor on the batteries. I've lost the numbers, but I did previously let the 100ah per day fridge use 100ah and worked out from other gel battery soc voltage figures I'd found that my 400ah was down to 277ah. 20% either side of that takes them from pretty good to ready to replace.

[WotEver]

20% either side of that takes them from pretty good to ready to replace.

Indeed. If you care enough you could always invest in a SmartGauge. That plus your Ah counter can tell you the capacity of your bank accurately to within a couple of percent.

 

Tony

[boathunter]

Indeed. If you care enough you could always invest in a SmartGauge. That plus your Ah counter can tell you the capacity of your bank accurately to within a couple of percent.

 

Tony

Grr, I only want to know once, there must be another way!

[WotEver]

Grr, I only want to know once, there must be another way!

Run 'em flat just the once and note the Ah reading?

[MtB]

Mike, Ian at Tipos marine will be getting some secondhand whispergens in the same as I use on my boat, they also run the central heating as well [5kilo watts output heat] these will be 24 volt units at a cost of aprox £1500 it might seem expensive but it will heat the boat/hot water and charge the batteries at the same time. Mine is on a timer so I wake up to hot rads and come home to a warm boat. Its just a thought and as a plumber the rads part would be easy for you. The positives of this are charged batteries everyday which will last longer and no need to light stove except at weekends, plus the whispergen is fairly fuel efficient

Peter

 

That sounds a very intriguing idea, thanks Peter!

 

I know very little about the whispergen other than that you hold it in high regard. What fuel does it run on? Presumably it runs quietly enough to run at night, yes? Or at least I can leave it running in the daytime while I'm off out working?

[peterboat]

 

That sounds a very intriguing idea, thanks Peter!

 

I know very little about the whispergen other than that you hold it in high regard. What fuel does it run on? Presumably it runs quietly enough to run at night, yes? Or at least I can leave it running in the daytime while I'm off out working?

It runs on kero or diesel and in reality in the winter mine runs for one and a half hours in the morning and the same in the evening. These three hours make up the missing amps from the solar panels. They are very quiet so yes running it in the evening is no problem and of course it provides a warm boat as well.

I am considering buying a sea going boat and if I do a whispergen is high on the list of things to buy for it

[cuthound]

The Whispergen is a Stirling engine driving a small generator. Stirling engines are woefully inefficient as a prime mover, hence why they were never used to haul trains, pump mines etc.

 

However if you use its inherent inefficiency to heat water and it's meagre output to drive a small generator, it becomes a very effective combined heat and power plant.

 

Unlike the large ones that the company I last worked for tried to utilise to heat,cool ano power supermarkets the Whispergen is reliable.