Keeping batteries fully charged

[RufusR]

9 hours ago, Tom and Bex said:

But we've got used to only 2hrs a day!

 

Twin alternators that are both A127, but start battery one runs on a smaller pulley. Also only have the one regulator (should have bought 2 before they went commercial!) We were seeing around 100A when starting charging, but have had to dial back the settings to around 70A to avoid killing alternator too quickly!

 

Fully agree! Along with increased water usage, toilet emptying etc! No concept of saving power and water despite our best efforts. 

 

Have solar, and surprised how much better it works with lithium batteries. Trouble is we get nothing October to February, and have shading til midday on our mooring in summer due to trees. 

Then you need more solar , I get enough to charge 550Ah AGM bank which is slot tougher than lithium’s all year around and have same tree shading issue as you , how much have you got ? Most narrowboaters have nowhere near enough hence doesn’t work in darker months , there seems to be a myth that 2 tidller 12volt panels is plenty on a narrowboat . 

[Sea Dog]

46 minutes ago, RufusR said:

there seems to be a myth that 2 tidller 12volt panels is plenty on a narrowboat . 

It's not a myth if you understand what your needs are, what your cruising pattern is and what expectations you have of your solar input.  My 2 X 150w panels match or exceed my expectations and suit me perfectly.

 

[Tony Brooks]

51 minutes ago, Sea Dog said:

It's not a myth if you understand what your needs are, what your cruising pattern is and what expectations you have of your solar input.  My 2 X 150w panels match or exceed my expectations and suit me perfectly.

 

and that leads us back to the start of the topic re the need for a power audit etc. so you do understand your needs. I went for about 7 years with just 65 watts of solar on a PWM controller and it was fine because we cruised every day most of the time and used solar to fully charge the batteries while we were back home.

[Tom and Bex]

14 hours ago, RufusR said:

Then you need more solar , I get enough to charge 550Ah AGM bank which is slot tougher than lithium’s all year around and have same tree shading issue as you , how much have you got ? Most narrowboaters have nowhere near enough hence doesn’t work in darker months , there seems to be a myth that 2 tidller 12volt panels is plenty on a narrowboat . 

Currently have 500w. Panels several years old now so low light performance probably better in some of the modern panels. Any recommendations? Considering some bi-facial panels, but sceptical of the claimed benefits, and quite expensive (although probably similar or cheaper per watt than we paid for existing ones!).

[IanD]

10 hours ago, Tom and Bex said:

Currently have 500w. Panels several years old now so low light performance probably better in some of the modern panels. Any recommendations? Considering some bi-facial panels, but sceptical of the claimed benefits, and quite expensive (although probably similar or cheaper per watt than we paid for existing ones!).

Bifacial panels don't produce any extra power when they're mounted flat on a roof (like on many narrowboats), only if they're on angled mounts so light from the sky can reflect off the mounting surface into the back of the panel.

 

To get the power increase (typically about 15%) claimed by the manufacturers they not only have to be angled but the mounting surface/roof has to be painted white or silver.

Edited November 18, 2020 by IanD

[RufusR]

15 hours ago, Tom and Bex said:

Currently have 500w. Panels several years old now so low light performance probably better in some of the modern panels. Any recommendations? Considering some bi-facial panels, but sceptical of the claimed benefits, and quite expensive (although probably similar or cheaper per watt than we paid for existing ones!).

I have 6 x  Perlight 270Watt compact black PERC panels they are 54 cell so fit lengthways across the boat while staying inside the profile of the boat . They are performing very well . There are alot of options , As said bifacial  need to be tilted on white roof and are quite big , I didnt go for that as wanted to tilt up alot facing forward or back along the boat . It depends on your needs as Seadog rightly said if cruising all the time you wont need as much but if stationary off grid like me and want to use solar in winter you need a fair bit , The old adage that you can never have enough solar in UK is probably true . If you are under trees Bimble have a limited time offer on some thin film low light 165 watt panels currently , that I may have looked at had they been available at the time , they are lower wattage as they are less efficient but in low light and shading they would almost certainly be better than crystalline panels , you will need a high voltage MPPT controller though as they are about 120volt panels so would need parallel connection . Worth a look but you would want to get about 6 on your roof to have a chance of putting 150Ah plus back into your bank in winter , maybe worth a look though .  

[Alan de Enfield]

2 minutes ago, RufusR said:

If you are under trees Bimble have a limited time offer on some thin film low light 165 watt panels currently , that I may have looked at had they been available at the time , they are lower wattage as they are less efficient but in low light and shading they would almost certainly be better than crystalline panels , you will need a high voltage MPPT controller though as they are about 120volt panels so would need parallel connection . Worth a look but you would want to get about 6 on your roof to have a chance of putting 150Ah plus back into your bank in winter , maybe worth a look though .  

A couple or three years ago Bimble had 120v, 170w 'low light panels' I bought one and it works well.

 

Do not be fooled into thinking that it works well in 'low light levels' - it doesn't.

It is designed to work in low light angles of incidence as we have in Northern latitudes (53 degrees North) where the Sun is low in the sky and 'has a long way to come'. Most panels are based, and rated, on their output at the equator with the Sun directly overhead at midday - we would never get the same output here.

 

My output on 18th Feb 3.3 amps at 14.2v (1x 170w panel) It didn't last for long tho'.

 

 

[PineappleGuy]

5 hours ago, Alan de Enfield said:

Most panels are based, and rated, on their output at the equator with the Sun directly overhead at midday - we would never get the same output here.

 

 

My understanding is that solar panels are rated assuming irradiation of 1000 watts/sq metre and a panel temperature of 25 degrees C. As Alan implies, the former is rarely achieved in this country even in the middle of a glorious mid-summer day and when it is, the panel temperature will be a lot higher than 25 degrees resulting in its output being reduced by a few percent. So if anyone obtains the rated output of their panel I will be quite surprised.

[RufusR]

on average in summer 50-60% of rating is the norm on very good days hence good to over panel quite a bit in the UK , Most I saw in August this year was just over 1000watts so about 62% , May have got a little more earlier in summer ( June / July )  but didnt have it completely set up properly then but I suspect 70% of rating would be abs max on bright sunny summers day with panels at optimum angle to the sun as well , having them flat on a sunny day will cut about 30% of output