Solar power help

[Cactus Sailing]

i must be of that age... i can't get my head around it.

i just want a semi flexible panel to fit on my coachroof and a solar power regulator to charge my batteries, its not to live off the power while on board so i dont need nothing big, just to maintain charge on the batteries without setting anything on fire or overcharging etc.

Specs; i have 120ah of leisure battery on board in 2x60ah if that makes a difference, again im just looking for something to top up the batteries, nothing is left running while not on board so i was thinking a 10w panel?

i do sail alot (as posed to motoring) so use power for instruments - i only tend to use the fridge on shore power or while on engine, other than that i switch it off and treat it like a cool box, i often charge up on shore power / motoring back in which has been adequate throughout summer, winter months my batteries are not at optimum charge so it will shorten their life i expect, i suspect its because im only motoring and sailing and not stopping on the boat overnight plugged in and using more than re-charging? unless my batteries are just on their way out.

i'd rather steer clear of eBay and the raft of cheap tat so any recommended "kits" from reputable places would be welcome

alternatively could i just put a small panel under a hatch? is that a thing, will it charge through a window?

thanks

 

[gregcope]

10w wont do much apart from charge a bit.

I would suggest allot more if you want to keep ip with instruments. You could work out your amps per day usage, charge rates and therefore panel suggestions. i think you will find it allot more that 10w.

Re regulators. Most will recommend a MPPT one as they are more efficient. However if you go that small the extra expense is hardly worth it and a PWM type would be fine. I prefer Victron regulators. Well made, good support.

Also think about cable runs and cable sizes. Reduce length and thick cables to reduce voltage drop and maximise charging.

Nothing wrong with ebay panels. Often a bargain to be had.

 

[CAPTAIN FANTASTIC]

The 10 watt is too small; you will need a 30 watt as a minimum with a small regulator; both can be purchased on ebay very cheap.

 

[William_H]

It sounds like you don't NEED a solar panel but your batteries might benefit from a panel if you leave the boat unattended for long periods. I think the approach would be to decide where and how you are going to mount a panel. This will then dictate the size you can reasonably fit. You may not need a semi flexible type. I am a fan of the solid types very cheap from China via Ebay. olewill

 

[peteK]

A 10w panel is too small to keep the batteries charged all year round,I have 2x10w which keep 2x85 amp batteries well topped up even during the winter.I would be looking for the biggest panel you can fit in the space available,but only fit a semiflexible if for some reason you cant fit a rigid one.Also fit a regulater as it will tell you when its charging and when full,dont dismiss ebay some good buys.

 

[GHA]

General rule of thumb is for 12v system is current out = watts / 20 plus a little bit. So top wack perfect conditions 20W will give you just over an amp .
Not going to help much day to day onboard but will help a lot by keeping the batteries at full charge when you're not using the boat.

 

[Pete7]

Kenneth, I have used these folks twice now and seen other recommendations on here for them:

https://www.photonicuniverse.com/en/catalog/list/page/2/category/flex-panels

Suggest you choose something about 30w and mount it as you suggested, on the coach roof. Under the spray hood won't do anything useful.

 

[Cactus Sailing]

Kenneth, I have used these folks twice now and seen other recommendations on here for them:

https://www.photonicuniverse.com/en/catalog/list/page/2/category/flex-panels

Suggest you choose something about 30w and mount it as you suggested, on the coach roof. Under the spray hood won't do anything useful.

Thanks for that, just what I’m looking for,

Quick question- if the batteries are indeed fully charged what does the regulator do with the excess power? Does the panel just get hot?

 

[VicS]

A basic controller will just disconnect when the volts reaches the set value and reconnect again when it has fallen to a lower value ( the specs will tell you the actual voltages)


A "pulse width modulated" (PWM) controller will reduce the charging by breaking the current into a series of decreasing pulses as the battery reaches full charge.

 

[Little Dorrit]

Thanks for that, just what I’m looking for,

Quick question- if the batteries are indeed fully charged what does the regulator do with the excess power? Does the panel just get hot?

Probaly less than 30W per hour so I suspect the regulator switches off sending and the additional energy is disspated by fins.

 

[noelex]

Quick question- if the batteries are indeed fully charged what does the regulator do with the excess power? Does the panel just get hot?

The panel needs a completed circuit to produce power. The regulator just disconnects the panel, so no power is produced.

In simple terms, PWM rapidly connects and disconnects the circuit to reduce the power produced.

The disconnected panel does produce any power or heat. The regulator also does not have to dissipate the power from the panel as no power is produced when the panel is disconnected. However, the circuitry and the switching process, does generate some waste heat. So regulators need reasonably large heatsinks and/or fans, but this waste heat is much less than the power of the panel.

 

[Cactus Sailing]

Thanks all - I ended up getting a 40w panel fits perfectly between the lines, what I’m thinking of now is best way to get cables into the cabin my initial thoughts were to take it in under the spray hood and get a gland of some description , any thoughts appreciated

 

[VicS]

Thanks all - I ended up getting a 40w panel fits perfectly between the lines, what I’m thinking of now is best way to get cables into the cabin my initial thoughts were to take it in under the spray hood and get a gland of some description , any thoughts appreciated

To keep things neat look at the side entry glands from Index Marine and Scanstrut.
There are several sizes available from the usual sources eg Force 4 https://www.force4.co.uk/department/electrical/plugs-sockets-deck-glands/deck-glands.html?limit=all

 

[temptress]

General rule of thumb is for 12v system is current out = watts / 20 plus a little bit. So top wack perfect conditions 20W will give you just over an amp .
Not going to help much day to day onboard but will help a lot by keeping the batteries at full charge when you're not using the boat.

Well thats a new one. Watts = Volts x Amps is the basic formula to use in DC calculations. there are other considerations but for you purpose you can ignore them.

then th question is how efficient is the setup, ancle of the sun, shading etc.
i would vet a 50w panel withan mppt controller and the forget about it. mppt controllers are so cheap these days why use anything else.

 

[Contest1]

The 10 watt is too small; you will need a 30 watt as a minimum with a small regulator; both can be purchased on ebay very cheap.

+1.

 

[GHA]

Well thats a new one. Watts = Volts x Amps is the basic formula to use in DC calculations. .

It actually works quite well for quick mental arithmetic. 100w panel on a good day, divide by 20 and add a bit, up towards 6A. Want more get the data sheet out. No way will you get watts/volts.

 

[Cactus Sailing]

To keep things neat look at the side entry glands from Index Marine and Scanstrut.
There are several sizes available from the usual sources eg Force 4 https://www.force4.co.uk/department/electrical/plugs-sockets-deck-glands/deck-glands.html?limit=all

Many thanks scanstrut ones look pretty neat - just need to work out how to get in around the inside of the cabin out of sight now!

On the securing screws for the gland is it best to seal these too for piece of mind?

 

[temptress]

It actually works quite well for quick mental arithmetic. 100w panel on a good day, divide by 20 and add a bit, up towards 6A. Want more get the data sheet out. No way will you get watts/volts.

You might be right. Stuck onboard in the tropics just now.. Will take a look at the monitor tomorrow swe if this works. Best I have seen from my 200w pannels is 15amps..9 is more usual.

 

[GHA]

You might be right. Stuck onboard in the tropics just now.. Will take a look at the monitor tomorrow swe if this works. Best I have seen from my 200w pannels is 15amps..9 is more usual.

Wow - 15A is some going!! I made a mistake getting a 10a victron mppt regulator instead of a 15A recently for 2 x 100W panels but not really a problem, they won't get up that high many times in their life .