Battery Condition

[Karizma]

Loving this thread as I'm just about to invest my 'hard earned' into some 'Victron goodies' as I love data and knowing what's happening to my batteries (especially the house bank).

So I'm:

• replacing the PWM solar controller to an MPPT so I can get more out of my panel, and check the data on my phone via bluetooth.
• installing 2 x 30 amp DC to DC chargers to control the charging profile on a bank of new AGM house batteries from my 2 x standard alternators.
• installing a battery monitor so I can see the 'state' of my batteries, how much I'm consuming on a daily basis and ensuring I dont drain them too far prior to recharging.
• introducing a bank of Mega and Midi fuses to make sure all wires are protected (which they aren't at the moment !!!).

The only thing left to do is pluck up enough courage to rip everything out and install all the new stuff !!!!! 

[Bluebell]

Wow, just wow…😎

[LondonRascal]

One thing about Solar is not to get hung up on wattage when you using them for charging batteries, which are DC. It is all about the Amps. So the 50w panel linked to earlier, has a peak, best condition output of 2.7Amps. Some might just show a short circuit peak amperage (in that panels case this is 3Amps). You will get some losses with resistance, and the sun is not always going to be shining super bright, and if laid flat on a roof this will effect its performance too. The point I am drawing attention to, is these are perfect if you have a boat left in the open without shore power to run a mains charger as they would maintain your batteries charge but don't expect them to 'charge a big battery bank' and some people spend a lot of money on having panels installed and see little return. 

If you have the room for larger panels, or several all the better - on Broad Ambition we have a pair of 100w panels which combined push out around 9Amps after losses, and in the summer easily run our 240v fridge, the losses running that using an Inverter brings and have a little bit left over to trickle charge into or domestic batteries too. But just the shadow of our Mast suddenly will take away a couple of Amps at times and it is interesting seeing the read out on our charge controller's panel as these things occur.

[MauriceMynah]

I am looking to have 4 panels, each being 1 metre by 2 metres ( very approximately )

I have no idea what watts/amps that could deliver

[grendel]

the low energy supermarket 100W flexible monocrystaline panels are 1200 x 540mm and around £100 each (https://lowenergysupermarket.com/product/flexible-100w-white-solar-panel-only/) so you could work out how many would fit your area for an approximation. (other brands and sizes are available- eg this 130W panel sized 960x640-https://uk.eco-worthy.com/products/130w-12v-flexible-mono-solar-panel?currency=GBP&variant=40700112994453&utm_medium=cpc&utm_source=google&utm_campaign=Google Shopping&gclid=EAIaIQobChMIqLau89a_gAMVD4dQBh20RwdZEAYYAiABEgIew_D_BwE

I see renology do a 175W panel sized 670x960 (currently out of stock) but the different options are there

[Meantime]

9 hours ago, LondonRascal said:

One thing about Solar is not to get hung up on wattage when you using them for charging batteries, which are DC. It is all about the Amps. So the 50w panel linked to earlier, has a peak, best condition output of 2.7Amps.

Sorry Robin, but the two are directly proportional and both give a good guide of potential charging output.

P (watts) = V (Volts) x I (Amps) The panel has a maximum rated output of 50w 18v 2.77A which if you multiply 18x2.77 gives you 49.86 or near enough 50w. The point being that as the sky clouds over and the current output drops, then so does the wattage in direct proportion. So if the current halved to say 1.385A then 18x1.385=24.93 or near enough 25w

The important thing with solar panels is the quality of the charge controller. In reality as the sky clouds over both the voltage output and the current drop at the same time. In order to recharge a battery, the charge voltage has to be higher than the battery voltage otherwise it won't charge. So lets assume the cloudy sky has reduced the voltage output to 9v at 1A or 9x1=9w, this will not recharge e battery, however a good charge controller will introduce a resistance which has the effect of raising the voltage, but lowering the current thus you might end up with 18v at 0.5A or 18x0.5=9w going into the battery.

In many ways watts is the more useful guide since most people will understand that all appliances are normally rated in watts, not amps. If the TV onboard your boat is 150w then a 50w solar panel is going to require more than 3 hours of perfect sunlight to power the TV for one hour. The wattage of a TV or other appliance is going to be easier to find than the current it draws, even though one can very easily be worked out from the other.

[MauriceMynah]

Is it possible/realistic  to have a thin flexible solar panel tailored to the dimensions I want, and if so what company does this? 

As it seems the controller is the really important thing,  are there any recommendations?

[annv]

Hi Photo electronics' are as good as any, dont know of a solar panel constructor. Get a larger controller than you need, you can then increase your size later. also get a three outlet one for same reason. You could get a suitcase solar panel to increase your power when you are on board. I have a 100w panel fixed to the roof this keeps all my battery's fully charged when not there , then when on board i have a 150w fold up panel for extra power when wild moored. John

[grendel]

those 50W panels I linked to even running on a cheap PWM charge controller, do manage to have enough output voltage to start charging at 5.30 on a grey wet morning, I would expect 10% of full output (or less) under those conditions, so maybe 5W, they also state they have diodes to help prevent the issue with shade and shadows.

[Meantime]

2 hours ago, MauriceMynah said:

Is it possible/realistic  to have a thin flexible solar panel tailored to the dimensions I want, and if so what company does this? 

As it seems the controller is the really important thing,  are there any recommendations?

Is it possible, yes, is it realistic, no due to cost.

Solar panels are actually made up of a number of cells arranged in series to give the required output. A cell normally gives in the range of 0.46v to 0.6v, so typically 32 cells are arranged in series to give upwards of 15v.

The size of the individual cell dictates the maximum amount of current the cell can produce. A typical 3 inch square cell will produce 1.7 amps. A 4 inch square panel will produce 3 amps.

So for instance you could use 32 x 3 inch square cells to produce approx 15v at 1.7 amps. Which would be about approx 12 inches by 24 inches. If you used 64 cells you could end up with a panel twice the size at either 12 inches by 48 inches, or 24 inches by 24 inches and depending on how it was constructed it would either give 15v at 3.4 amps or 30v at 1.7 amps. 

Basically anything is possible when designing bespoke panels, but at a bespoke cost!!

There is enough choice of off the shelf panels that you should be able to find something that will be close enough to the size you want to fill.