Battery bank size & solar

[Thedreamoneday]

Apologies, I appreciate this has been kind of done to death and I appreciate it depends on what draw you have on the system but I'd like to find out from current/ past/ future lives boards on what you have, could I ask for a short reply about:

1) What size of battery bank you have ie 400ah
2) What size of solar panels ie 150w
3) Do you wish to have more or is that ample?

The reason for the question is I've negotiated a new bank with my new boat purchase, it did have 440ah and I'm being told only 400ah will fit the holes. (The boat is in Ionain so I can't check, I've asked for measurements)

I think I want the biggest ah I can squeeze in, for the reason 'you can't have too much' but I'd like to put my mind at rest that 400ah will be enough. I have 150w solar and the boat is being kept in Greece for live aboard from next year.

Thanks in advance.

 

[sailaboutvic]

We have 400 ah plus engine battery ,
In all 190 w solar panel , plenty in the summer , could do with a bit more for the winter , but we are heave uses .
We also have an 913 wind gem , not that's any thing to talk about , but it does help on windy night
We all wish we had more but you have to be realistic .

 

[vyv_cox]

1) 330Ah
2) 125 w
3) Perfectly good for summer months. In September more engine running needed. In winter nowhere near enough solar, if remaining at anchor consider alternative power generation methods.

 

[macd]

450Ah domestic batteries
340w rigid panels
No other passive charging.
More than enough in summer (charge peaks around 25A), and copes pretty well into November.
Life's too short to tilt panels, but luckily we have enough to compensate.

P.S. It's self-evident, but worth stressing, that sunlight is, as it were, assymetric with the sailing season. Sun height and duration on 21 April is identical to that on 21 August. But on 21 November, it's the same as on 21 Jan...i.e., not a lot. Late season sailing makes big demands on one's battery budget; in spring, it makes relatively few (plus the water's cooler in spring, so fridges get an easier time).

 

[blampied]

1) 340ah house, 75ah engine start, 75ah winch/thruster
2) 4x100w semi flexible solar through MPPT controller, the panels are flat, not tilt able (at any one time 1 will be in shade)
3) the solar panels provide far more power than can be used during the day, spring, summer and autumn (not yet been on the boat during winter, so unknown).
Power output can reach 25a during the day (if running heavy loads like air conditioning through inverter), but starts to fall off quickly two hours before sun set.
Bigger battery capacity would be an advantage.
A way to tilt the panels to keep producing power end of day would also help.

 

[GrahamM376]

480ah house (Trojan T125), 200w tilting solar + aerogen4. Fridge is the killer, can manage OK in summer but winter a bit iffy so some more solar would be good.

 

[RAI]

440 Ah (albeit 12 years old) with 180 Wp worth of panels, cheapo MPPT controller. This seems to manage a well insulated fridge plus live-aboard lights etc.
However the Smartguage settles at about 80/85% charge. I guess that way more charge can be accepted when the panels are at their best.

 

[affinite]

550Ah House bank
220Ahr Bow thruster bank
110Ahr Start
200W solar
std 50A alternator - no charge controller

"Killer" fridge
All LED lighting
Solar keeps up in summer but we dont liveaboard out of season so cant really comment on winter.

BTW - I think it is a mistake to go for the biggest bank possible.
Apart from the weight of all that lead, conventional wisdom has it that if one battery in the bank fails, then you should replace all the batteries in the bank.
The bigger the bank the bigger the bill !

I'd recommend you concentrate on reducing consumption before adding to your bank.
As previously mentioned , the fridge is the biggest culprit. Oh and dont be one of those d*cks who leave the chartplotter and all the mast instruments switched on when in harbour in order to show off.
(sorry must have fallen out of the wrong side of the bed today)

 

[macd]

...the fridge is the biggest culprit.

Typically, yes, but laptops can come a close second if used a lot. I had one that drew 8A when running and charging, yet it was incapable of keeping even one beer cold

 

[Thedreamoneday]

Thanks for the replies so far, it seems I'll be in the ball park for what most have apart from affinite who seems to have the capacity to have floodlights ��

The main drain seems the fridge which we have keel cooled so I'd imagine will help, I have tilt able panels and plan to have a marina berth for the winter months looking ok over all.

Thanks again for all replies.

 

[geem]

800 amp hr
420w solar
Duogen
Fridge freezer, two large plotters, power hungry autopilot.
We like the large bank as over night we barely drop 10% of capacity. No discharging should mean long and healthy battery life. Panels can tilt but don't bother much as wee are usually charged by 1030 here in Caribbean

 

[NornaBiron]

435amphr at 24 volt
200 watts of solar panels
Airbreeze wind gen
We live on the hook year round and very, very rarely have to use the deisel generator to charge. We run fridge, laptop, tv, charging of e-books/tablets/phone etc, all led lighting. Watermaker is used when the wind is blowing, we'd like a bit more solar power to be able to run it more frequently but where to put more panels is the problem.

 

[geem]

435amphr at 24 volt
200 watts of solar panels
Airbreeze wind gen
We live on the hook year round and very, very rarely have to use the deisel generator to charge. We run fridge, laptop, tv, charging of e-books/tablets/phone etc, all led lighting. Watermaker is used when the wind is blowing, we'd like a bit more solar power to be able to run it more frequently but where to put more panels is the problem.

We have 300w of solar on the guardwires. 4 x 75w panels that can be adjusted. Works very well. We have had panels like this for 11years with no mishaps

 

[vyv_cox]

The main drain seems the fridge which we have keel cooled so I'd imagine will help, I have tilt able panels and plan to have a marina berth for the winter months looking ok over all.

My fridge is 65 litres capacity, Danfoss 35F compressor, seawater cooled using a PAR Max1 pump. Consumption is 4 amps just after its cycle starts, falling to just over 3 amps at end, both including the pump which draws less than 0.5 amps. The cycle is roughly 20 minutes in the hour, rather more at the height of summer, especially in ports where the water is warmer.

 

[Thedreamoneday]

480ah house (Trojan T125), 200w tilting solar + aerogen4. Fridge is the killer, can manage OK in summer but winter a bit iffy so some more solar would be good.

Did you have to modify the battery compartment in anyway to accommodate the 120ah batteries?

 

[sailinglegend420]

.....However the Smartguage settles at about 80/85% charge.....

I fear this sums up MOST peoples situation! You will never get your batteries to 100% without about 600 watts of panels, or other charging sources.

This needs a book to fully explain what is happening, but have you noticed most people say their batteries are "full by lunchtime" - usually because a little green light tells them, or because they have dropped down to FLOAT mode. In Float the charging voltage is about 1 volt lower than Absorption, and at this voltage there are not enough sun hours left in the day to get enough Ahs back into the battery.

Why is getting to 100% so important - that's another book!

 

[GrahamM376]

Did you have to modify the battery compartment in anyway to accommodate the 120ah batteries?

No, I thought I was going to have to but found the Trojans to be a few mm smaller than their quoted size so they just fitted width wise in our boxes which had contained 110ah leisures. Shorter in length so had to add blocks to take up the space left. They're 240ah 6v by the way, not 120ah.

 

[noelex]

400 AHr and 330w.

It should be remembered that batteries are just storage devices that will average out a load they do not generate any power.

In summer we have loads of power. In winter I would prefer more power, but a larger battery bank just averages out the good and bad days. It does not give you more power.

if you are using using a generator a large battery bank is important to ensure a suitable acceptance rate during the (hopefully) short generator run time. If using solar the output is a over a much longer duration a smaller battery bank sizes are sensible. Wind is a bit in between.

The most cost effective battery bank size (in terms of cost per year) is to aim for about a 40-50% discharge rate. Some people have a battery bank size where 10% discharge is a normal cycle. Batteries will die of old age no matter what you do.

A bank of half the size (with a 20% average discharge) would be half the cost, half the weight (and lugging batteries is not my favourite boat task) and last about 85-90% of the larger bank.

The aim is not for the longest lasting battery bank, rather a combination of the least inconvenience (buying new batteries is difficult in out of the way places and they are bloody heavy), together with lowest cost per year. The size of the battery bank is strongly influenced by the day to day variations in output and consumption.

If your average discharge is in the 20-40% level, and greater than 50% is rare, you are close to sweet spot of battery size for solar.

In the Ionian over summer solar output is very consistent, but with 150w of solar you will need to be reasonably frugal. 150w over summer will generate perhaps 80Ahrs a day.

Enlarging the battery bank from 400 AHrs to 600 AHrs, only gives any extra 100Ahrs @ 50% discharge. If it is 4-5 days between plugging into shore power this is only an extra 20-25 AHrs per day. (In my case I only plug into shore power every couple of years so the battery bank will only average the solar panel output) You could get the same useful AHrs with an extra 40-50w of solar. Solar panels have a much longer life than batteries so if you can do this it is better alternative.

In short, I would try an add more solar if this is possible rather than worry about small differences in battery bank size.

 

[NornaBiron]

We have 300w of solar on the guardwires. 4 x 75w panels that can be adjusted. Works very well. We have had panels like this for 11years with no mishaps

We already have one 100 watt panel on each aft quarter guard rail, no room for any more unfortunately, and we really don't want a gantry. Windy days work well for us with the watermaker.

 

[TQA]

675 ah battery bank [ 6 x Trojan T 105 golf cart batteries ]

400 watts tiltable solar.

Fully charged by mid day on a good day.

The size of my bank lets me go 2 + days before I need to think about running the engine in heavy overcast conditions.