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Nick D

Another Battery Question

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17 minutes ago, Dr Bob said:

Yea, but Smelly said his were at 12.6 with a very light load. IF that was my system it says he would be at 90% SoC ish so has used only  45Ahr ish since yesterday evening. That seems a bit light. With TV's. fridges etc we use 100Ahr+ overnight. So on 440Ahrs capacity, you would be down to 12.4-12.5 ish.

 

But those voltages cannot be relied upon, Shirley?

 

Received wisdom says the batt needs to have been at rest for an hour or two before relying on terminal voltage to determine SoC.

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3 minutes ago, Mike the Boilerman said:

 

But those voltages cannot be relied upon, Shirley?

 

Received wisdom says the batt needs to have been at rest for an hour or two before relying on terminal voltage to determine SoC.

If the current draw is constant (ish) and low (ish) then you can estimate the delta between that state and true resting voltage as long as you have the data to make your assumption. It's not really rocket science. I used to work on the estimation that a draw of 1.7A (typical first thing in the morning winter draw ....with no fridge compressor running) would give a 0.1V lower reading (ish). Smellys 0.3A is therefore not going to be a big delta to a true resting voltage.

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1 hour ago, Dr Bob said:

Yea, but Smelly said his were at 12.6 with a very light load. IF that was my system it says he would be at 90% SoC ish so has used only  45Ahr ish since yesterday evening. That seems a bit light. With TV's. fridges etc we use 100Ahr+ overnight. So on 440Ahrs capacity, you would be down to 12.4-12.5 ish.

That makes me feel a lot better as our usage is around the 100ah mark from finishing cruising to next morning, but earlier in this thread some folks were suggesting this was unusually high.  The difference is that we are around 12.2v in the morning so I still think I need new batteries!

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1 minute ago, Nick D said:

That makes me feel a lot better as our usage is around the 100ah mark from finishing cruising to next morning, but earlier in this thread some folks were suggesting this was unusually high.  The difference is that we are around 12.2v in the morning so I still think I need new batteries!

They are still doing what you need from them, everything runs until you start cruising the next day, so no panic to change them unless you want to change your cruising pattern.

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1 hour ago, Dr Bob said:

Yea, but Smelly said his were at 12.6 with a very light load. IF that was my system it says he would be at 90% SoC ish so has used only  45Ahr ish since yesterday evening. That seems a bit light. With TV's. fridges etc we use 100Ahr+ overnight. So on 440Ahrs capacity, you would be down to 12.4-12.5 ish.

I didnt look at how many ampy things its used. You must remember though, I have vastly superior built mains fridges that dont run very often unlike guzzling 12 volt expensive to buy fridges. I sold them both a couple of years ago. It seems to me that the combined wisdom from peeps still using 12 volt fridges havnt bought and used the latest mains kit yet so still think 12 volt uses less leccy?? They dont, point blank. Anyone who wishes can come and see my leccy set up and monitor for them selves how little the set up uses.

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3 hours ago, mrsmelly said:

I didnt look at how many ampy things its used. You must remember though, I have vastly superior built mains fridges that dont run very often unlike guzzling 12 volt expensive to buy fridges. I sold them both a couple of years ago. It seems to me that the combined wisdom from peeps still using 12 volt fridges havnt bought and used the latest mains kit yet so still think 12 volt uses less leccy?? They dont, point blank. Anyone who wishes can come and see my leccy set up and monitor for them selves how little the set up uses.

It’s not just about power consumption, it’s also about resilience. How much sobbing are you going to do when your inverter packs up and you have to revert to blocks of ice being towed down from the Arctic?

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So I have looke one minute ago at my cheapo over two year old battery bank. Switched engine off at 630 last evening, telly on ( mains ) till 11pm and usual bits of fone and pc charging. Both fridge and seperate freezer ( mains ) on all night and just looked at monitor at 12.6 with a discharge of 5.6 aps at present. Just sayin that sealed cheapos do an admirable job if the rest of the kit is fit for purpose. The silly graph bit down the right side of foto is never looked at or reset or owt so its not relevant  to actual state of charge ever.

IMG_20190711_082045.jpg

Edited by mrsmelly

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13 minutes ago, mrsmelly said:

So I have looke one minute ago at my cheapo over two year old battery bank. Switched engine off at 630 last evening, telly on ( mains ) till 11pm and usual bits of fone and pc charging. Both fridge and seperate freezer ( mains ) on all night and just looked at monitor at 12.6 with a discharge of 5.6 aps at present. Just sayin that sealed cheapos do an admirable job if the rest of the kit is fit for purpose. The silly graph bit down the right side of foto is never looked at or reset or owt so its not relevant  to actual state of charge ever.

IMG_20190711_082045.jpg

The voltage is only one place of decimals!!!

 

No, I agree. My cheapo's were still 90%+ capacity after 2 years. 50% of time off line. Always charged at least every 2 days....but never below 75% SoC and mainly not below 80%.

Follow these rules and they should last. Peeps are doing bad things to their batteries!

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10 minutes ago, Dr Bob said:

The voltage is only one place of decimals!!!

 

No, I agree. My cheapo's were still 90%+ capacity after 2 years. 50% of time off line. Always charged at least every 2 days....but never below 75% SoC and mainly not below 80%.

Follow these rules and they should last. Peeps are doing bad things to their batteries!

Well no, I disagree. Our boat was more than 1/2 the year on shore power, rest of the time we cruise for 6-8 hours a day every day with a good modern alternator set to 14.5v or so. Never got anywhere near 50% DoD (until much capacity was lost). Both sets of cheapos lost capacity significantly after 6 months.

 

Perhaps it is luck of the draw and/or the exact nature or the brand.

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1 minute ago, nicknorman said:

Well no, I disagree. Our boat was more than 1/2 the year on shore power, rest of the time we cruise for 6-8 hours a day every day with a good modern alternator set to 14.5v or so. Never got anywhere near 50% DoD (until much capacity was lost). Both sets of cheapos lost capacity significantly after 6 months.

 

Perhaps it is luck of the draw and/or the exact nature or the brand.

I am beginning to think along these lines Nick. My cheapos at about 100 quid from Britmarine for the last two sets may well be better than many of the cheapos on offer at 60 ish quids??

I am deffo never going back to 12volt fridges and stuff though.

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3 minutes ago, nicknorman said:

Well no, I disagree. Our boat was more than 1/2 the year on shore power, rest of the time we cruise for 6-8 hours a day every day with a good modern alternator set to 14.5v or so. Never got anywhere near 50% DoD (until much capacity was lost). Both sets of cheapos lost capacity significantly after 6 months.

 

Perhaps it is luck of the draw and/or the exact nature or the brand.

That comes into it!
My last set, full time livaboard, no shorepower whatsoever, mains fridge freezer like yourself (inverter with standby function) and batteries Donald Ducked after 15 months. Still some life in them of course, but insufficient for our needs. They will be demoted to outside lighting at the winter mooring, and currently being used as much needed ballast.
I have really mollycoddled them too. There is one sat on the back deck and I kick it whenever I walk past.

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We have a 12v fridge that is on all the time, batteries (6*110 numax) that we don't leave on charge all the time. When we are out we tend to cruise for 6-8hrs a day and have the inverter and a digital radio on for around 6hrs when we stop. Our monitor is usually on 12.6 or 12.7 in the morning. The fridge if running takes about 3.3amps.

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12 hours ago, nicknorman said:

It’s not just about power consumption, it’s also about resilience. How much sobbing are you going to do when your inverter packs up and you have to revert to blocks of ice being towed down from the Arctic?

The same amount of sobbing as when a 12V fridge pops its clogs?

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2 hours ago, Iain_S said:

The same amount of sobbing as when a 12V fridge pops its clogs?

Yes but with 2 things to go wrong (inverter or mains fridge) as opposed to one (12v fridge) the chances of drowning in tears is increased.

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19 minutes ago, nicknorman said:

Yes but with 2 things to go wrong (inverter or mains fridge) as opposed to one (12v fridge) the chances of drowning in tears is increased.

Virtual Greenie I have had this happen to me twice! with my crap Vetus inverters, now I have a shoreline fridge freezer running at 24 volts which uses less power than the 240 volt jobbie it replaced

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13 hours ago, peterboat said:

Virtual Greenie I have had this happen to me twice! with my crap Vetus inverters, now I have a shoreline fridge freezer running at 24 volts which uses less power than the 240 volt jobbie it replaced

Another example of them vetus jobbies going wrong! ... I have always stuck with sterling equipment and never had a problem with it and heard of very few that have, as for 12volt fridges , I have a 12 volt fridge and seperate 12 volt freezer and if i pick the right time, like first thing in the morning when both have been closed all night i get very similar figures to Tim. 

 

Rick

 

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5 hours ago, dccruiser said:

Another example of them vetus jobbies going wrong! ... I have always stuck with sterling equipment and never had a problem with it and heard of very few that have, as for 12volt fridges , I have a 12 volt fridge and seperate 12 volt freezer and if i pick the right time, like first thing in the morning when both have been closed all night i get very similar figures to Tim. 

 

Rick

 

Thats a good point Rick. the ones that make me giggle are the ones that turn the fridge off overnight to save battery capacity. In reality when closed up all night they very rarely kick in but far rather the odd bit of battery useage during the night than switching back on in the morning so they run for ages to get back to the proper temperature, let alone yo yo food temperatures which is as bad as it gets!!

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Turning off the fridge overnite - when I've had to do this, I usually run the engine first thing, so the extra consumption for an hour or two as the fridge works to get back down to temp is covered by the engine - that or the solar which kicks in after being "off" over nite. So, it does make some sense - even though not ideal and I try to live properly and keep the fridge on - a bastion of civilisation. 

Actually, whenever I wake in the night, the fridge is normally running so I don't think it somehow doesn't use much over nite!

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3 hours ago, Johny London said:

Turning off the fridge overnite - when I've had to do this, I usually run the engine first thing, so the extra consumption for an hour or two as the fridge works to get back down to temp is covered by the engine - that or the solar which kicks in after being "off" over nite. So, it does make some sense - even though not ideal and I try to live properly and keep the fridge on - a bastion of civilisation. 

Actually, whenever I wake in the night, the fridge is normally running so I don't think it somehow doesn't use much over nite!

Yes we were doing this a couple of weeks ago as the batteries were losing the will to live.
During this current weather which is very warm in the cabin, I have found that our 12V desk fan pointed down the side of the fridge/freezer makes it cut in less often. It is as if the fridge can't dissipate the heat into the cabin and is running far longer.  (A winter task is to get some cooling going from the bilges using computer case fans.) The desk fan is very low power so uses minimal battery.

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