Why do you need a large house battery bank?

[Greenheart]

Strangely we used to get by, sailing from buoy to buoy to anchorage with just a bit of motoring at each end of the day, before solar was affordable and without wind generators [just] the standard alternator. And that was before LED bulbs.

:biggrin-new: I believe that. The more kit there is to 'make life better', the more complicated it becomes to incorporate and use it.

I wonder whether it's possible to separate the last 30 years' potential improvements introduced in the form of more efficient electronics and largely frivolous current-consumers available on board, from other very palpable improvements in things like clothing...

...an author in the 'seventies said that comfort afloat was mostly the avoidance of discomfort. I think he had a point. It might be a fine, cheap thing, to rid a yacht of damp and gutless lighting and unreliable heating, without also loading her up with non-essentials which themselves require maintenance, upgraded batteries and rats' nests of wiring.

I'm not thinking I'll persuade anyone, except myself.

There was an article in the September 2008 PBO, on fitting a solar-powered fridge. Although, real ale beats pale frosted gnats' piss.

 

[prv]

I wonder whether it's possible to separate the last 30 years' potential improvements introduced in the form of more efficient electronics and largely frivolous current-consumers available on board, from other very palpable improvements in things like clothing...

I'm not convinced that the improvements in sailing clothing since 1988 have really been all that revolutionary. Given the audience here, it wouldn't surprise me to hear from someone who bought a fancy new set in the late 80s and is still using them now.

The real game-changer in that timeframe was the arrival of GPS in yachts, which completely changed navigation.

non-essentials which themselves require maintenance, upgraded batteries and rats' nests of wiring.

Nothing requires a rat's nest of wiring - it's an unfortunate side-effect of either repeated small upgrades each taking the easiest path, or wholesale re-work by someone without the skills to do a decent job

Pete

 

[johnalison]

I don't think that GPS changed things as much as Decca; it just did it better and quicker. As for clothing, the arrival of breathable wet gear was a major change, as well as wind-proof fleeces. I can't say exactly when they arrived but I bought my first breathables in 2001.

I do though recall with some fondness when the only current-users in regular use were the radio and Decca, and one scarcely gave a thought to the batteries. Modern plotters and such are not really the problem, it's the fridge, stupid. My boat came with 150Ahrs of service batteries, but adding an extra 50% has greatly improved the usable capacity as well as reducing transient voltage drops and extending the batteries' life.

 

[lw395]

....1.

I do though recall with some fondness when the only current-users in regular use were the radio and Decca, and one scarcely gave a thought to the batteries. Modern plotters and such are not really the problem, it's the fridge, stupid. My boat came with 150Ahrs of service batteries, but adding an extra 50% has greatly improved the usable capacity as well as reducing transient voltage drops and extending the batteries' life.

1) Fridge.
2) Eberbasto
3) once you've got heating, your season is extended, so TV/Radio/PC use is increased in the darker evenings. And yours is the boat people come back to using lights etc into the early hours.
4) Radar, windlasses, bow thrusters.
5) Inverters and random domestic appliances. It becomes sensible to uses toasters, kettles, microwaves instead of expensive camping gaz
6) autopilots have gone from low power jobs used now and then to serious bits of kit that eat power, and people use them all the time.

 

[Amulet]

Nope.
You have to put back somewhere between 110 and perhaps 170Ah.
For sure a big bank can take a higher charge rate, e.g. if like us you typically leave harbour under power, so the engine might run for an hour each morning.
Provided that the wiring etc actually gets the full voltage to the batteries. At these currents, it's quite easy to lose a few tens of mV here and there, which can stack up and influence the charge rate disproportionally.

Ach, stop being difficult - it makes no difference to the argument. Anyone with a mind to be constructive would have realised that I meant put 100Ah into the battery bank. If your charging opportunities are brief but you can chuck a lot of amps at it, you may benefit from by using a big bank so that when it's low you can feed it fast. I do understand the physics and chemistry of this task, and I'm not a believer in perpetual motion.

 

[lw395]

Ach, stop being difficult - it makes no difference to the argument. Anyone with a mind to be constructive would have realised that I meant put 100Ah into the battery bank. If your charging opportunities are brief but you can chuck a lot of amps at it, you may benefit from by using a big bank so that when it's low you can feed it fast. I do understand the physics and chemistry of this task, and I'm not a believer in perpetual motion.

But that's just a recipe for short battery life at high expense.

 

[Amulet]

1) Fridge.
2) Eberbasto
3) once you've got heating, your season is extended, so TV/Radio/PC use is increased in the darker evenings. And yours is the boat people come back to using lights etc into the early hours.
4) Radar, windlasses, bow thrusters.
5) Inverters and random domestic appliances. It becomes sensible to uses toasters, kettles, microwaves instead of expensive camping gaz
6) autopilots have gone from low power jobs used now and then to serious bits of kit that eat power, and people use them all the time.

Everyone has to titrate hassle and complexity against functionality gained. It's an entirely personal choice. It depends on your expertise and enthusiasm. Amulet has a large amount of electric functionality for a tiny boat, but I know where every wire runs and what it does. Perplexed crew members say I should spend more time on deck. Perhaps they're right, but I am having fun.

 

[lw395]

Everyone has to titrate hassle and complexity against functionality gained. It's an entirely personal choice. It depends on your expertise and enthusiasm. Amulet has a large amount of electric functionality for a tiny boat, but I know where every wire runs and what it does. Perplexed crew members say I should spend more time on deck. Perhaps they're right, but I am having fun.

One person's hassle and complexity is another person's interesting exercise in electrical DIY.
We balance owning boats for the fun of actually sailing them, against the utility of using them as caravans, a device to spend time in different nice places.

 

[Greenheart]

We balance owning boats for the fun of actually sailing them, against the utility of using them as caravans...

I'm sure that's the truth. I wonder which aspect can be trimmed back the farthest, before we decide we like being on board, less?

I tented joyfully through the '90s with friends. Our earliest trips were amazingly simple - I used the canvas tent my grandfather had made 50 years earlier, and managed with candles, books and a bottle of scotch. My mate kipped on the rear seat of his 7-series.

Within a few years, we were in high-tech tents with 240v hook-ups and every electric benefit. I remember that we were very happy to have upgraded...but I don't have any strong sense of the character of the latter experiences, nor much memory of them.

I wouldn't go back to the canvas tent - it had no groundsheet and I shared with a lot of uninvited insects. But in every other respect, I liked the way the old tent was unlike home. So I'm not sure I'll want TV, microwave or laptop on board my cabin boat.

I was lately persuaded that using oil or paraffin navigation lamps, is too extreme a throwback, when LED equivalents are so reliable and capable. I guess that's an instance of the unarguable benefit of technology - something we always needed, now made effortless...

...but ever more batteries brought aboard, in order to replicate the modern normality of home ashore? That sounds...really boring.

 

[Tranona]

...but ever more batteries brought aboard, in order to replicate the modern normality of home ashore? That sounds...really boring.

If you do delve back into the past - for example by reading Maurice Griffiths you will find that cruising yachtsmen have always spent time and effort trying to bring domestic comforts into their boats, reflecting life at home. So, having a good cooker, stove for heating, electric light, comfortable berths etc were high on the list of priorities. much of his writings were aimed at showing that cruising on small boats was different from racing - which dominated the scene and the press at the time (1920s - 1930s).

No different today except of course the expectations are higher reflecting the advances(?) in technology.

 

[ghostlymoron]

I'm sure that's the truth. I wonder which aspect can be trimmed back the farthest, before we decide we like being on board, less?

I tented joyfully through the '90s with friends. Our earliest trips were amazingly simple - I used the canvas tent my grandfather had made 50 years earlier, and managed with candles, books and a bottle of scotch. My mate kipped on the rear seat of his 7-series.

Within a few years, we were in high-tech tents with 240v hook-ups and every electric benefit. I remember that we were very happy to have upgraded...but I don't have any strong sense of the character of the latter experiences, nor much memory of them.

I wouldn't go back to the canvas tent - it had no groundsheet and I shared with a lot of uninvited insects. But in every other respect, I liked the way the old tent was unlike home. So I'm not sure I'll want TV, microwave or laptop on board my cabin boat.

I was lately persuaded that using oil or paraffin navigation lamps, is too extreme a throwback, when LED equivalents are so reliable and capable. I guess that's an instance of the unarguable benefit of technology - something we always needed, now made effortless...

...but ever more batteries brought aboard, in order to replicate the modern normality of home ashore? That sounds...really boring.

I agree, Dan, if you've got all home comforts, it's just like being at home and is that what we want. To me the whole point is to be unlike home. Mind you I don't live on my boat which is a bit different. I would hazard a guess that most forumites also don't live aboard.
I wouldn't dream of having TV on a boat and neither do we have it in our caravan although we could. We enjoy a break from the intrusive box in the corner and read books, listen to radio and watch the comings and goings in the anchorage.
I think a lot of the experience is lost when it's 'home from home's.

 

[Greenheart]

So, having a good cooker, stove for heating, electric light, comfortable berths etc were high on the list of priorities.

They will be on my boat, too...they're all what I call basic necessities. Improvements in how those basics function, can only be a good thing.

But I doubt that TV/PC screens etc, which I enjoy at home (often, to evoke what it's like to be out sailing) will be 'better than the real thing', on board.

My phone is wholly equal to the business of playing music, films and communicating with everyone, everywhere...and I can charge it with a pocket solar-panel.

I guess it depends how reliant you feel upon electrical appliances at home, and whether you're significantly less comfortable without them, on board.

I know there was a company in the Victorian era that made pianos that could fit into yachts. Perversely, I'd quite like one of those. But as for the rest...

"...radar...sonar...electric toothbrushes..."

 

[Amulet]

But that's just a recipe for short battery life at high expense.

Ach away and bile yer heid. Your more interested in showing how clever you are than helping the poster. OK , we agree you are clever!

You are making your life needlessly difficult if you insist on doing lots of battery charging in the 90% to 100% region. Most boats are only sailing for a small fraction of their life. Even with a big battery bank it will spend most of its time sitting on its berth with its intelligent charger keeping the battery healthy. What's more, you don't need to go anything like down to 50% to get the battery to take charges of, say, C/6. If your cruising gives you only occasional brief charging opportunities you may be able to put a 100 Ah into a big bank that's at 60% without bringing it up to 100%, but have no chance of bringing a 200Ah battery from 50% to 100%. Therefore you gained more in that charging episode than you would have with a smaller bank - and we use batteries that are designed to stand a bit of discharge.

 

[Polly1]

I seem to able to use 10A quite easily, 3 for the fridge (its is on quite a lot in the tropics), LED lights, some home media, gas alarm etc. A 400 W solar set up seems to keep up with this and a bit more in the day. Then 12 h night so 120Ah down worst case minus a bit for night time reduction maybe 60 Ah down by the morning. I need to run the new set up to see the figures over time. If I want to keep the cells above 60 percent then 150Ah would cope with the daily fluctuation.

It has been interesting reading the replies. I see that large banks cope with a generation shortfall for longer but at proportionally more expense. Apart from the ability of a larger bank to absorb current more readily from a low resistance supply when generation capacity is plentiful (ie an alternator) the other advantages seem to be one side of a coin.

"Well, considering that to improve lifespan of the battery one should not discharge more than 60 percent."

OK so set this as a limit, at this point or before (if possible) change what you are doing. The limit will still come up with a large bank just after proportionally more time

"The obvious reason for a large house battery bank is that, no matter how much electricity you can generate during the day from solar or engine/generator running, you cannot put any more power into the batteries once they are full so, from that point onwards, the leccy is just being wasted."

This is true even for a large bank, once it is full it is full

"Another benefit of a larger bank in relation to net usage is that working thee batteries less hard tends to extend their life."

But your purchase and eventual replacement costs due to age or a unintended discharge have gone up proportionaly

"If you are running a standard alternator with set voltage regulator then surely you get a larger current into a battery initially then the current decreases as apparent voltage of the battery increases. Now if you have 2 batteries in parallel you will get that same current into each battery which means twice the AH stashed away for every hour of engine run. Likewise for another battery in parallel up until the alternator becomes current limited by RPM or its size limitation. "

Seems correct from my experience but only true when considering charging from the engine. I imagine solar is limited more by the internal resistance of the cells, maybe true for wind too.

"Charging the 20Ah battery will be something roughly like 90% efficient up to 80% then progressively less efficient.
Charging the 200Ah bank the last 10Ah will be at best 50% efficient."

That makes sense but I cant help thinking in terms of “there is no such thing as a free lunch” that something similar must be going on for the other side ie how efficient the battery is when discharging.

 

[RichardS]

That makes sense but I cant help thinking in terms of “there is no such thing as a free lunch” that something similar must be going on for the other side ie how efficient the battery is when discharging.

I think you are discounting the cruciality of post #5 too quickly. That is really the key issue. Obviously, their is a cost / benefit balance to be undertaken on any setup but the only important technical issue is whether you normally generate more power that your bank can hold and how this relates to your normal daily usage and your typical recharging opportunities. That's all that matters.

Ignore all the "efficiency" stuff as that's all either incorrect and/or irrelevant.

Richard