Electrical charging conundrum

[jac]

Hoping that the combined wisdom of the panel may be able to assist with this.

One of the jobs over the winter is to bring our electrical system up to spec.

At present we have 85 ah engine start plus 2x85ah in a domestic bank. Charging via 60a alternator and 20a battery charger.
Our domestic demands are approx 50-60ah per day. Sailing is about another 15 to 25ah. Realistically we don't expect to sail much at night (young children) so happy to use the engine more to cover any shortfall from night sailing.

As we will usually motor in and out of harbour I'm working on the assumption that motoring in and out will cover most of the sailing demand.

Whilst we do use Marinas my preference is to avoid them .

I would like to be able to be self sufficient for at least 3-4 days but would obviously love more if we can get it.

My thought process so far is that we need to increas the battery bank substantially. Assuming that we can only use about 1/3 of the stated battery capacity we need 180 ah of battery to provide 1 day of domestic or about 240 of total requirement so substantial increase in battery requirements is probably top of the priority list.

We then need to generate more power. It's a choice of solar or wind for me. Wind will be no real problem for a mounting location, solar is more of a challenge. I don't want to put a stern gantry on with panels on there. That leaves me with the deck. Due to all lines being run aft plus hatches and baby stay I don't have a large open space. We can fit in a panel 60cmx70cm on the starboard side of the mast, 40cmx40cm to port but will be by the mast so in the shadow of the mast etc some of the time. We can fit in a wide but narrow panel forward of the baby stay 100cm by 15cm or aft, either side of the dinghy a panel approx 50cm by 34 cm. however these may be shaded by stowed dinghy / cockpit tent, back stay, boom.

Final priority is better management / measurement of battery state. Without digging out multimeter we only have voltage available so was thinking of smart gauge monitor and smart bank split charger to do this.

So what is the opinion of the panel. Priorities about right?
What impact does the likely shade have on the panels output?
Shade / size suggests that panels will not produce enough on there own so will really depend on a wind genny for the bulk of the input?

 

[westhinder]

I'm very interested in the replies as I am doing a similar exercice. Have you considered a flexible panel on the sprayhood?
What is your cruising area? If UK, wind may be more productive and reliable than solar. If further south, things may be different.

 

[Playtime]

Your first priority, as you rightly suggest, will be to increase the battery bank. A single 85Ah for start battery should be OK (assuming you haven't got a motor bigger than 60hp) but I would suggest the minimum for the service bank should be 2 x 140Ah. It is OK to run the batteries down to 50% (if they are recharged shortly after) so that should give you a usable capacity of 140Ah.

Given your constraints, my second priority would be to uprate the alternator and fit a smart alternator controller or a Sterling Alternator to Battery charger so you can get the maximum benefit from your engine use. With a 90A alternator you could push maybe 60Ah into the batteries in one hour with the right controller.

A battery monitor that reads amps as well as volts would also be well worthwhile (rather than a SmartCharge which only gives volts and an approximation of % charge) so you can see the amps and amp hours in and out.

I have no experience with either wind or solar but would make the following comments. Unless you get one of the latest high power wind generators, small ones are (apparently) useless for anything but trickle charging. Further the bigger they are the more noisy they become.

Solar is very popular now but, as you recognise, you do need a few square feet of clear unshaded deck. A rule of thumb I have seen quoted is to divide the stated watts of the panels by 4 to give an approximation of the amp hours provided on a good sunny day e.g. 100W of panel can produce 25Ah on a sunny day - much less if partly shaded or cloudy.

 

[BabaYaga]

A rule of thumb I have seen quoted is to divide the stated watts of the panels by 4 to give an approximation of the amp hours provided on a good sunny day e.g. 100W of panel can produce 25Ah on a sunny day - much less if partly shaded or cloudy.

I seem to remember that rule of thumb comes from landbased solar installations and that the 25 "percent" figure is actually a monthly average (so includes both sunny and cloudy days), further that it is valid only for four summer months and at middle or north european latitudes.
With these limitations in mind I still think the "25 Ah for every 100W" is a realistic way to figure out what to expect from a solar installation on a boat.

 

[jac]

Thanks all so far.

Couple of answers to questions posed so far. Sailing area is UK south coast and English Channel. Likely to be 2-3 weeks use in a cruise.

Re Amp hours counters, I have seen several sources saying they are not accurate - good explanation here http://www.smartgauge.co.uk/sgvahrs.html (appreciate it may be biased)

I'm erring towards a Rutland 914i - seem to have a good reputation as a company and quite efficient. Several on boats moored nearby and can't really hear anything, although if going with wind will certainly use rubber gaskets to insulate the genny vibrations and prevent resonating into the hull

 

[pvb]

Re Amp hours counters, I have seen several sources saying they are not accurate - good explanation here http://www.smartgauge.co.uk/sgvahrs.html (appreciate it may be biased)

Very biased. Decent battery monitors are far more accurate than he suggests, and fully compensate for Peukert effects, charging efficiency, temperature, etc, etc. I use a Xantrex Link 10 (now obselete) but the latest version is the LinkPRO and is about the same price as a Smartgauge. As Playtime mentioned, it's good to be able to see the actual current going into or out of your battery bank, rather than just some vague approximation of capacity.

I'm erring towards a Rutland 914i - seem to have a good reputation as a company and quite efficient. Several on boats moored nearby and can't really hear anything, although if going with wind will certainly use rubber gaskets to insulate the genny vibrations and prevent resonating into the hull

The ones I've seen in marinas have been impressively quiet.

 

[Ian_Edwards]

I'm just going through the same exercise for the 4th time.

So far I've decided to go for a Sterling A to B 130amp controller and install it over the winter. Currently the alternator doesn't contribute at tick-over.

I've fitted 200watts of solar panel, but the are on the coach-roof and a shaded by the boom, I'm unsure how much I get out of them but they certainly helps.

I've changed all my domestic and Navigation lights to LEDs.

I intend to improve to insulation on the fridge and freeze over the winter.

I've installed a Smart Gauge and already have a MasterVolt volts/amps/state of charge system. Interestingly, the Smart Guage and MasterVolt systems don't agree on the state of charge, with the master volt system being obviously wrong (perhaps because I have set it up since fitting a new 500 amp hr domestic battery bank). But being able to see the amps pile in, is very reassuring.

So I'd recommend looking at minimising energy consumption, eg fitting LED lighting, if you haven't already done that and making the best of your alternator, I'd fit a smart charge controller before upgrading the alternator, you may find you can get enough charge out out of your existing unit.

Hope this helps

 

[ianj99]

Fit a smaller pulley to the alternator. No matter how much you spend on fancy regulators, the output is still very rpm dependent.

I use a Sterling digital regulator but even so, the output at low engine revs is nothing special although a lot more than with the alternators own regulator and better than it was in both cases when the pulley was changed to the smallest one I could find.

If I had your requirements, I'd think about spending the money on the biggest alternator I could fit, preferably a 12pole one and just stick with the cheaper digital regulator. I'm done putting all my eggs into one basket with Sterling's more expensive products after a £279 30a triple output charger failed after barely 3 years. I now use two cheaper (not Sterling) chargers so if one should fail, I have a backup.

Or I'd fit a second alternator and regulator: more work to fit but better in the event one alternator or regulator fails.

 

[GrahamM376]

As already said, a battery monitor with ability to show volts + amps in or out is a good thing. I have used 2 x nASA BM1s (one on each domestic bank) for several years and found them good value for money.

Mounting flexible solar on the spray hood will give disappointing results because flexible aren't much good and they will also spend much of the time in the shade. Mounting rigid panels on the guard wires will give better results as they can be tilted when sun is sideways on. For liveaboard use in warm temps., you need to be looking at 200W upwards.

If your main aim is power for a 2-3 week cruise on anchor, consider a suitcase genny and decent output battery charger.

 

[TomC]

Hi Jac,

Have you looked at fuel cells as a possibility?

Tom

 

[pvb]

Hi Jac,

Have you looked at fuel cells as a possibility?

Tom

Is it April 1 already?

 

[Heckler]

Hoping that the combined wisdom of the panel may be able to assist with this.

One of the jobs over the winter is to bring our electrical system up to spec.

At present we have 85 ah engine start plus 2x85ah in a domestic bank. Charging via 60a alternator and 20a battery charger.
Our domestic demands are approx 50-60ah per day. Sailing is about another 15 to 25ah. Realistically we don't expect to sail much at night (young children) so happy to use the engine more to cover any shortfall from night sailing.

As we will usually motor in and out of harbour I'm working on the assumption that motoring in and out will cover most of the sailing demand.

Whilst we do use Marinas my preference is to avoid them .

I would like to be able to be self sufficient for at least 3-4 days but would obviously love more if we can get it.

My thought process so far is that we need to increas the battery bank substantially. Assuming that we can only use about 1/3 of the stated battery capacity we need 180 ah of battery to provide 1 day of domestic or about 240 of total requirement so substantial increase in battery requirements is probably top of the priority list.

We then need to generate more power. It's a choice of solar or wind for me. Wind will be no real problem for a mounting location, solar is more of a challenge. I don't want to put a stern gantry on with panels on there. That leaves me with the deck. Due to all lines being run aft plus hatches and baby stay I don't have a large open space. We can fit in a panel 60cmx70cm on the starboard side of the mast, 40cmx40cm to port but will be by the mast so in the shadow of the mast etc some of the time. We can fit in a wide but narrow panel forward of the baby stay 100cm by 15cm or aft, either side of the dinghy a panel approx 50cm by 34 cm. however these may be shaded by stowed dinghy / cockpit tent, back stay, boom.

Final priority is better management / measurement of battery state. Without digging out multimeter we only have voltage available so was thinking of smart gauge monitor and smart bank split charger to do this.

So what is the opinion of the panel. Priorities about right?
What impact does the likely shade have on the panels output?
Shade / size suggests that panels will not produce enough on there own so will really depend on a wind genny for the bulk of the input?

Bene 381, 4 by 110amphr domestic, 1 by 85 amphr starter. 1 by 56 watt solar panel. Sterling alternator booster
Fridge on when we go on board, it takes about 5 amps, off when we lock up at the end of the trip. Aten leds in the saloon.
We went on a 5 week trip, the longest we were off mains was in the Scillies for 6 days. The domestics lasted ok BUT were getting down, we kept the starter one out of circuit until needed. I reckon another day and we would have needed to start the engine for a recharge. So 220 amps useable, divided by 6 equals 37 amps per day plus the solar. I reckon if I put another 100 watter on then I would just about be self sufficient.
Stu

 

[sailinglegend420]

Very biased. Decent battery monitors are far more accurate than he suggests, and fully compensate for Peukert effects, charging efficiency, temperature, etc, etc. I use a Xantrex Link 10 (now obselete) but the latest version is the LinkPRO and is about the same price as a Smartgauge. As Playtime mentioned, it's good to be able to see the actual current going into or out of your battery bank, rather than just some vague approximation of capacity......

I have a SmartGuage monitor and a BEP battery monitor. The SmartGuage is more than just "some vague approximation of capacity" - it actually gets more and more accurate as the batteries age whereas any battery monitor gets more and more inaccurate as the batteries age.

Even with a correctly installed Battery Monitor and shunt all the original settings like Ah capacity, Charge efficiency, and Peukerts constant change with age, as does self-discharge which isn't adjusted for by most BMs as far as I know. So a Battery Monitor is always going to get more inaccurate, but a SmartGuage is always getting more accurate because it learns what your batteries are doing and adjusts its algorithm by reading the battery voltage over one thousand times a second.

I've seen so many wrongly installed shunts or installations - often caused by extra equipment that has been added by "engineers" that don't know or can't see a shunt is installed, so it is not surprising that Battery Monitors are not always accurate. A SmartGuage just uses two small wires to monitor the battery voltage and needs no shunt.

When SmartGuage first came out people said it couldn't work - including the man at Merlin who finally bought the company. His clients in the UK Military were demanding a more accurate BM and are now very happy with the SmartGuage. Recent tests done by Odyssey batteries showed it had an inaccuracy of 0.1% - too good for most of us. 50 times that, or 5%, would be OK for me.

I agree an ammeter is essential to be able to count Ah usage, so my recommendation is always that a digital one should be bought along with a SmartGuage. This will give you the best and cheapest Battery Monitor setup.

 

[pvb]

When SmartGuage first came out people said it couldn't work - including the man at Merlin who finally bought the company. His clients in the UK Military were demanding a more accurate BM and are now very happy with the SmartGuage. Recent tests done by Odyssey batteries showed it had an inaccuracy of 0.1% - too good for most of us. 50 times that, or 5%, would be OK for me.

I'm bemused by your post. Just the other day you posted about the Smartgauge on another thread, saying "It's one failing is mine tends to read 100% charged too early. As soon as the charge stops it will re-calculate and eventually give you an accurate reading." Seems to me it's either accurate or not.

 

[GrahamM376]

I agree an ammeter is essential to be able to count Ah usage, so my recommendation is always that a digital one should be bought along with a SmartGuage.This will give you the best and cheapest Battery Monitor setup

How can approx 100% dearer than a NASA (which displays volts, amps and capacity remaining) be the cheapest option?

 

[sailinglegend420]

I'm bemused by your post. Just the other day you posted about the Smartgauge on another thread, saying "It's one failing is mine tends to read 100% charged too early. As soon as the charge stops it will re-calculate and eventually give you an accurate reading." Seems to me it's either accurate or not.

My Smartguage showed 100% and an hour later when off charge showed 96% - that's 4% inaccurate when charging - not bad in my view.

 

[dslittle]

My Smartguage showed 100% and an hour later when off charge showed 96% - that's 4% inaccurate when charging - not bad in my view.

My Smartgauge also drops off initially after the shore power is disconnected. I spoke to Merlin about this at SIBS on Saturday and the consensus was that the Smartgauge has 'learnt' that 100% is 13.4v - the float charge - so that when the battery 'drops' to 12.7v it is not at 100%. Once away from shore power for any length of time (or I leave the battery charger off to see what happens) the discharge rate evens out as I would expect. As it goes, I can see the Amps going in through the MPPT Regulator and the Amps going out on my panel as well so I can VERY ROUGHLY work out the plus and minus.

Horses for courses and all that but the Smartgauge keeps me very happy...

 

[pvb]

My Smartguage showed 100% and an hour later when off charge showed 96% - that's 4% inaccurate when charging - not bad in my view.

Probably about as accurate as my Xantrex battery monitor then.

 

[sailinglegend420]

How can approx 100% dearer than a NASA (which displays volts, amps and capacity remaining) be the cheapest option?

Sorry for a slight overstatement - but I did say BEST battery monitor set up.

Nasa £105 - other brands twice the price.
Smartguage and a separate shunt from another manufacturer less than £200.

But the Nasa can only measure up to 100 amps and 650 Ah battery capacity.

You do get what you pay for.

 

[halcyon]

that 100% is 13.4v - the float charge - so that when the battery 'drops' to 12.7v it is not at 100%.

As a passing point, a year old battery can have a settled charged voltage of 13.0 / 13.1 volt, this can be the voltage after charging with a standard fixed voltage OE alternator regulator. Over time this voltage will fall to around 12.8 / 12.7 but remember this is temperature related as well as a number of other things.

Brian