Batteries!

[Cardo]

The prettier half and I have recently bought a Southerly 105 that we intend to live aboard for a couple of years (Mostly Med/Caribbean).
As with many liveaboards, the plan is to live on the hook when not on the move.

I will be sticking a couple of 80W solar panels on her to help with keeping the batteries topped up.

She currently has two service batteries (which I understand are pretty old and need replacing) and a smaller, car sized starter battery.

Taking into account the solar panels we're intending to install, what would be your advice in relation to purchasing new batteries? What Ah ratings should we aim for? Will two service batteries be sufficient or should we consider adding more?

Our electric use will mostly be lights/fridge/occasional laptop and charging iPhones/other small devices. However, on longer passages we will likely need to keep the autopilot going (this may require supplementing the solar panels with the engine once in a while).

Anyhow, I would appreciate your thoughts.

 

[multihullsailor6]

In my view you will have to considerably upgrade your electrical system if you want to be kind of self-sufficient:
1) At least 440 a/h house batteries
2) LED lights / bulbs everywhere (house, navigation)
3) 300W solar panels with a MPPT charge contolller
4) Wind generator (my personal choice would be a Silentwind, Air Breeze with the silent wind blades or the D400)
5) Fridge with keel cooler, if not the keel cooler at least a fridge designed / built for tropical temperatures.
If you plan on using your engine for battery charging go for a clever charging system and an uprated alternator.

 

[Cardo]

In my view you will have to considerably upgrade your electrical system if you want to be kind of self-sufficient:
1) At least 440 a/h house batteries

How many batteries would this normally be, and what type of battery would be recommended? My shore power battery charger (Mastervolt Mass 12/30) supports two banks of batteries. Would this be ok hooked up to, say, 4 house batteries plus the starter battery?

2) LED lights / bulbs everywhere (house, navigation)

Already working on this!

3) 300W solar panels with a MPPT charge contolller

300W! Hmm, not sure where I'd put quite so many panels. The two 80W panels are already going to take some quite imaginative mounting. I guess I could also put a panel on the hatch cover, though it'll still leave us somewhat short. I'll have to have a good think.

4) Wind generator (my personal choice would be a Silentwind, Air Breeze with the silent wind blades or the D400)

Is a wind generator worth it? I got the impression most people thought they were a waste of space/money?

5) Fridge with keel cooler, if not the keel cooler at least a fridge designed / built for tropical temperatures.

We have a lifting keel, so keel cooler probably not viable. I'll look into fridges designed for tropical temperatures. Our current fridge can run off gas if needed. Would this be advisable, or should we aim for a 12V fridge that works well in the heat?

If you plan on using your engine for battery charging go for a clever charging system and an uprated alternator.

This may be a little over what we're aiming for. I think I'll have to try and work out how to survive without the engine...

Thanks for the suggestions!

 

[TQA]

Flooded wet cell golf cart batteries work well if you can get them at a reasonable price.

Consider fitting an arch which allows the panels to be tilted. I have 400w on my 44 ft. and can use the arch to lift the dink.

Get a MPPT controller to make best use of the power generated.

IMHO you will need someting like 300w minimum and you need to be very energy efficient.

 

[multihullsailor6]

Hi Cardo!

To answer some of your points from my perspective:

1) I have 4 x 110 a/h lead acid batteries in tandem on my boat, linked to the solar panels, the wind generator and shore power charger, plus a 90 a/h starter battery. Don't underestimate your battery consumption as a liveaboard! Especially on longer trips you will be using a lot of power for lights, VHF/HF radio, AIS, autopilot (an electrical one pulls out a LOT of amps!), radar, chartplotter, GPS, navtex / weatherman, water pressure pump, water maker etc... Are you into watching TV / videos / CD Rom on 12V?

2) Solar panels: Put them on an arch, you should be able to put 3 or 4 abreast and, if you need to for space reasons on the arch, have them folding out from the aft pulpit.

3) Wind generator: would not want to be without a high-performing and fairly quite one!

4) Keel cooler: actually a misname - you normally attach it to the hull as low as possible.

Another point: think about heating, it gets cold in the Med in winter!

 

[Cardo]

There sure is a lot to think about here! Battery wise, I think we'll be ok once we get some new batteries.
Are we better off with 4x 110Ah or would 2x 225Ah be suitable? We only have a dinky boat, so space is an issue!

We'll have to look into how we're going to mount solar panels & wind genny. May have to splash out on an arch (ouch!).

So you find the wind generator does contribute? How interesting, the lot over in the other bit of the forum really don't like them!

Just looked up keel coolers. Yes, I see. Not cheap! We'd probably need a new fridge, too. Ouch. Have any of you spoken with someone that has a fridge that can run off gas? Any thoughts on these?

Heating wise, we have an Eberspacher. Please tell me this is ok!

 

[Mistroma]

You are getting good generic advice but it sounds as if you are surprised at the battery & panel sizes. Apologies if you know most of the following but it might help explain things.

If it gets overly complex, the basic message is that everything conspires against you to push up battery size & charging requirements. So try to just make a high level summary of what you need for each area.


This can get pretty complex and the thread may go in all sorts of directions because there are lots of variables. The following might help to work out what you need. I assume that you don't have unlimited funds and so you will want to prioritise expenditure. That's the real trick, getting the best bang per buck. There are tools to help with this (mostly XLS files) but it always seems to become more complex the deeper you delve into it.

If you consider three areas:
1) Power usage
2) Battery type & capacity
3) Power generation

1)Power usage
First thing is to do an energy audit i.e. Work through your estimated daily power usage. It's worth looking at high usage items and working out how to reduce them.

The fridge will be the single largest user and if you are making a guess of usage then 40 Ahr/day might be a reasonable starting point. However, installation, insulation and external temperature will probably as more important than increasing battery size. I installed the unit on our old Southerly 95 and managed to fit in a lot of insulation. I might be able to advise if Southerly 105 galley is similar and the fridge is a conversion on the original cool-box (that's what I did).


2) Battery type & capacity
If you have a good system for ventilating the battery compartment and have easy access then good quality wet lead acid batteries are a good bet. Otherwise you are looking are more expensive battery types (not always more expensive in long term).

Capacity required will depend on daily usage and how much charge you expect each day. Figures you are getting here sound sensible (assuming that you don't go mad with electrical devices).

N.B.
It isn't as simple as saying "I use 80Ahr per day and want to charge every 2nd day so need 2x80 = 160Ahr batteries".

Don't expect to get 100Ahr from a 100Ahr battery. Different types have different performance but as a general rule you will mostly charge to 80% and run down to 50% before recharging. So suddenly, a 100 Ahr batery is only giving 30Ahr useable capacity.


3) Power generation
Now look at how much power you need to generate each day and work out how much you want to put back. There are inefficiencies in battery charging that mean you have to put more back than you take out. Take 85% as a reasonable guess at efficiency.

e.g. If daily usage is 80 Ah then you need to put back 80*100/85 = 94 Ah at some point in order to replace it.

Commonest sources are engine alternator, solar panels, generator and wind gen. Looking at solar, you need to allow for the fact that panels won't deliver 100% of their rated capacity (shadows, angle to sun, hours daylight).

I don't have figures for solar in the areas you will be cruising but am guessing 160W panels might only produce 30-35 Ah/day
I know that my own Rutland 913 only produces an average in summer of 10 Ah per day and that's in Scotland where it is windy. However, my mounting point should be sl. higher and I tend to anchor out of the wind.
Your engine might only have an 80Ah alternator and poor regulation so that will probably only give a fraction of charge rate you expect.


Apologies for the long note but I'm afraid that you can try to analyse the detail or take general advice and hope it is close enough match your lifestyle. I can only scratch the surface in this note so lots of simplifications and items left out.

BTW I had a D3L Eber heater for around 20 years on my old Southerly 95 and found it reliable and adequate even in Scotland. Always laid up in winter but I ran it when working on board and it seemed to cope with temperatures much lower than med. in winter. Power use in winter would be a problem but I imagine you will be in a marina or yard at that time.

 

[Mistroma]

I had added that I'm not a full time liveaboard but it was chopped from bottom of the previous post. I'm nice and comfortable at home just now and won't be living on board again until early spring.

Full time liveaboards will be the best source of advice. However, my own priorities would be:

1) Engine alternator, regulator & spilt-charging system
2) Batteries
3) Solar panels
4) Suitcase generator (contentious one, but it is a useful backup)
5) Wind gen

I've found my Wind gen gives least return for outlay. However, I opted for a Rutland 913 as it was quiet (fitted just above aft cabin). At that time I only wanted batteries charged up on mooring. Spending >6 months afloat changes everthing so bigger (noisier) one probably more suitable. My own daily charge in summer has been carefully logged for a couple of years at 10-12 Ah per day and I'd really want at least twice that amount.

Regarding batteries:
110 Ah are lighter, easier to move. If one fails you still have 75% capacity left and you can get away with replacing one if they are all pretty new when it happens.

Only reason to go for 225 Ah would be if they were a better fit in the compartment or cheaper for some reason. Perhaps I've missed something so will see if others agree.

I'm currently replacing my own 110 Ah units and wanted to use 6V batteries but they are 2mm too wide so I'll either rebuild the box or re-think my plans before spring.

 

[TQA]

If considering a wind gen AND solar make sure you don't shadow the solar with the wind gen, kills the solar output.

Only way I can see that working for you is if you hang the wind gen in the foretraingle.

 

[multihullsailor6]

So you find the wind generator does contribute? How interesting, the lot over in the other bit of the forum really don't like them!

I've been in enough situations where it has either
- been very cloudy / pelting down with rain but with wind
- been sunny and windy but shadows fall over the solar panels
so that I was happy to have a windgenerator. And of course a windgenerator keeps on working on windy nights!

 

[Cardo]

You are getting good generic advice but it sounds as if you are surprised at the battery & panel sizes.

Replying to all replies above but just wanted to quote this bit above. Yes, I am somewhat surprised, but mostly because I've read some other posts where people seemed to get by with less (I wonder how they manage it?). However, when breaking down the numbers, it certainly makes sense. Unfortunately, a smaller boat doesn't really use less electric, although it has a lot less space!

I had been contemplating installing a couple of 80W panels as "wings" like in this photo -

However, it would appear that would still leave us pretty short in the electric generating department. I can't really think of any other way to get more panels on there other than installing an arch. The other half isn't a fan of arches as she feels they spoil the lines of the boat, however I can't see a way around it at the moment!

The other consideration is the cost of an arch. I've had a quick search however because of the bespoke nature of arches, there is no indication of cost. I don't suppose anyone might be able to give an inkling as to what these cost to have installed?

The benefits of an arch would be that a number of items can be placed out of the way, and it would also provide shade, in addition to being able to mount a number of larger solar panels. This will require some research!

In relation to batteries, the compartment isn't particularly large. It currently holds two domestic batteries plus the smaller starter battery. A third battery could potentially be squeezed in, though they would be packed in tight. However, I don't see why I wouldn't be able to have two batteries in the current compartment and fit a further two batteries under the starboard seating, just forward of the current compartment?
AGM batteries seem to cost around 2x the price of standard batteries. Are they worth it?

I see how a wind genny would be handy, especially as it would provide at least some charge on rainy/cloudy days. If going with the arch idea, I guess it could also live on that. Though then it brings the problems with shadows...

There's certainly a lot to think about here. Any further advice or suggestions is certainly welcome!

 

[charles_reed]

I'd agree broadly with Multihull Sailor - though you don't state the AH capacity you have, it's probably inadequate.
I on a smaller boat have a lot more PV (320w) capacity, on an MPPT controller, and would, if I could find room and burthen have more than the 350 AH I currently have in battery capacity.

I had wind generation, but when the generator packed up, worked out the adjusted capital cost per AH supplied was £18 for PV panels and £33 for the wind generator - so the prime investment has been in PV panels not wind generation. This ROC will be heavily influenced by the sailing area (mine is E Med). I also rejected LED lighting (my fluorescent and halogen lighting only represents 6% of total electric budget).
It's worth considering using your dedicated engine start battery to amplify total capacity.
Computer and fridge are the greatest users of power - a CULV CPU running Linux rather than Microsoft OS and at least 100mm insulation on the fridge reduces these by about 40%.
Engine recharging is an essential - your current proposals are unrealistic - I have a smart controller on a 120amp alternator instead of the normal 35amp one fitted as standard and a 40 amp switch-mode charger.
I'm liveaboard about 6/12, mostly anchored, cruise about 3000nm pa.

 

[Cardo]

Further to my post - our current fridge is similar to this one -

It can run off 12/240/gas. What are the thoughts on this? There is also the cool box as has been mentioned previously, but that doesn't currently have any cooling elements to it.

 

[charles_reed]

Further to my post - our current fridge is similar to this one -

It can run off 12/240/gas. What are the thoughts on this? There is also the cool box as has been mentioned previously, but that doesn't currently have any cooling elements to it.

Suspect it's a Peltier effect fridge - about the most power-guzzling form on the market and totally inefficent.
Junk it and get a ASU-Isotherm or Waeco unit or (if awash with cash) one from Penguin Refridgeration.

 

[jordanbasset]

We have a keel cooled fridge and LED lighting throughout, this helps a lot. The first season we had just one 60w solar panel with 560AH domestic battery bank. It meant every 4-5 days we needed to run the engine, not a real problem as we would normally be on the move in this time and the wind was not always reliable.
Now have 2 x 100w solar panels, only had them for 4 weeks prior to laying the boat up. We are in the med but this was October, did not need to run the engine. It does depend on where you are but do not think you will be far off with 200w of solar panel, especially if you also reduce the demand by using energy saving measures. Also have an adverc which does maximise charging of the battery when we are underway.
As others have said an energy audit is a good place to start and allow for extras, as there will probably be some

 

[TQA]

I know that fridge and I have a good news bad news scenario for you.

If you are serious about being self sufficient AND running that fridge you will need to run the fridge on gas. The good news is that it is at it's most efficient on gas and will at least keep your beer cool if not cold while at anchor in warmer climes. Also by running the fridge on gas your electricity consumption will be much reduced so your current solar package will do [I think]. But you will use about a standard small calor gas bottle a week.

The bad news is that fridge will only work if level and it is real pernickerty about this. So forget about using it on passage.

A more efficient fridge setup is to have a top opening fridge with a minimum of 6" of insulation and a modern compressor cooling unit. I have an Adler Barbour super cold machine and in the tropics make two trays of ice a day plus keeping a large but well insulated top opening box really cold at <50 ah per day.

 

[ccscott49]

Suspect it's a Peltier effect fridge - about the most power-guzzling form on the market and totally inefficent.
Junk it and get a ASU-Isotherm or Waeco unit or (if awash with cash) one from Penguin Refridgeration.

Gas/240/12v fridges are absorbsion fridges, small flame, I wouldnt thave one near a boat and as you say they are inefficient, but not as bad as a peltier.

 

[Mistroma]

Fridge Design

Your current fridge design does look as if it won't be very efficient. It is front opening (convenient but loses heat easily) and the door insulation will be virtually non-existant.

If I remember correctly, the 105 galley & saloon area is very similar to my old 95. I converted the cool-box on that model by installing a plate and compressor without too much problem.

1) Compressor fitted in the saloon locker on port side just in front of the galley.
This gives a very short pipe run into the cool-box. I built a shelf in the locker and had fan assisted cooling ducts to circulate air (worked well in Scotland). However, you will be better off with water cooling.

2) Extra insulation added to cool-box
I seem to remember that there's quite a lot of space around the outside of the cool-box. I think that I removed the panel under the sink and inserted some trunking to take pipework to the compressor. Then I foamed in the surrounding space (can't remember the spec. of foam).

It wasn't ideal but I think that I managed around 4"-6" in most places but only 2"-3" in some spots. It was the best I could manage with the space available without use of exotic insulation material. Worked well enough on hottest days (though air temp only 25-28 C max.).

Oh, just remembered that I made a foam plug for bottom section around the cool-box drain valve. This allowed access if required.

If I remember the Southerly design correctly this was really the only suitable place to mount the fridge. You could build something into a saloon locker or put it in the cavernous bilges but access would be really poor for daily use. My wife hated the top access to the cool-box but the benefits over a front opener were so great that she got used to it.

 

[sailinglegend420]

......AGM batteries seem to cost around 2x the price of standard batteries. Are they worth it?

Boats never have enough charging capacity or battery capacity. Make the available space work better for you. 30 Ah from a 100 Ah battery demonstrates the problem.

Throw out the starter battery and get a very small Red Flash or Odyssey AGM battery that can be mounted anywhere, even on its side under the floor or the bed. Because they don't gas and don't leak they don't need a ventilated compartment. Use ANY other spaces on the boat to fit as many AGM service batteries as you can. 220 Ahs may have a smaller footprint than 2 x 110Ahs - but are very heavy to move - but hopefully that will only happen every 6 years or so! AGMs are worth the extra cost over "marine" batteries because they have one other main advantage - they charge about 30% faster than other batteries because their charge efficient is 98%, as opposed to the 85% of other batteries. They can also take a higher inrush charge current without damage, so you will need to up your shorepower and alternator/regulator to get the best out of them.

One other way to increase the capacity is to mix and match the size of the batteries. This goes against all advice from most battery manufacturers, but this site have done extensive tests that conclude that as long as the batteries are the same age and type they will be fine.

I suggest you search through the archives as your question is asked repeatedly, with all these points covered in great - if somewhat heated - discussions.

 

[lennartl]

AGMs are worth the extra cost over "marine" batteries because they have one other main advantage - they charge about 30% faster than other batteries because their charge efficient is 98%, as opposed to the 85% of other batteries. They can also take a higher inrush charge current without damage, so you will need to up your shorepower and alternator/regulator to get the best out of them.

I will upgrad to AGM before liveabord in MED, but it´s expencive, and also difficult to make a choice of a new charging/splitter systems. Witch system/brand realy get this 30%faster and 98% efficentsy?