Small craft Solar/battery kits

[steve yates]

I have an 18ft trailer sailer.
I have 2 120hr leisure agm batteries, £90 from ebay. A 50w semi flexible solarpanel, £60 from ebay, and a small dual battery mppt controller from someone like bimble solar for around £40. That set up keeps me cruising for a week before having to charge up in a marina.

You would probably only need one battery, so around £250 would see you sorted.

Should say that small dual battery controller is pmw, not mppt, an mppt one can be had for about £70.

I now have a sprayhood and will add a second panel, hopefully about 120w on top of the sprayhood, and will swap that 10a pmw comtroller for a 20a mppt one.

 

[Fantasie 19]

Unfortunately, if it only has a USB output, it is not really feasible.

Can we expand on that one as to why not feasible??? My understanding is USB is just a fancy electronic power socket so if you had a female USB to plug the panel in to, exposed/extended the wires, identified positive and negative, you could probably rig a connection to a battery???

 

[PaulRainbow]

Can we expand on that one as to why not feasible??? My understanding is USB is just a fancy electronic power socket so if you had a female USB to plug the panel in to, exposed/extended the wires, identified positive and negative, you could probably rig a connection to a battery???

But USB is 5V, connecting that to a 12V battery won't end well

 

[[70521]]

Battery capacity is defined by Parkinson's Law

No matter the size of your battery bank your usage will grow, you will find more uses for the stored energy, until your usage (or the usage by your crew) is greater than the capacity.

I am delighted to report that I have been reversing Parkinson's Law on my boat by working to reduce my power usage, but I love stepping aboard and leaving the crazy land world behind.

 

[noelex]

Can we expand on that one as to why not feasible??? My understanding is USB is just a fancy electronic power socket so if you had a female USB to plug the panel in to, exposed/extended the wires, identified positive and negative, you could probably rig a connection to a battery???

As Paul has indicated, the voltage is not suitable. There are several types of USB sockets, and some are capable of putting out up to 20V, but the socket "negotiates" with the device it is plugged into. To extract this output, suitable electronics would have to be installed (at least some resistors acting as a voltage divider on the other pins) between the socket and battery so that the socket outputs this higher voltage. This is assuming that the solar panel is fitted with one of the more advanced USB sockets capable of delivering above 12V, which is unlikely.

The other option would be to hack into the solar panel and tap into the solar panel output before it connects to the USB socket. However, if it is only fitted with one of the lower-powered USB sockets, the voltage of the solar panel is likely to be below 12V. This means you need a boost converter, and these are expensive.

So not quite impossible, but it is not a practical option.

 

[Fantasie 19]

But USB is 5V, connecting that to a 12V battery won't end well

There you go.. knew you'd know, and obvious if I'd thought long enough about it.. cheers, Paul

 

[toothless]

On my old swift 23 I had a single 18w flexible panel attached to a pwm controller feeding a 110ah battery. It ran the lights /vhf /autopilot plenty well for day sailing or weekend hops without any engine charging.I'm sure the panel wasn't keeping up with use but it had a week to fill the battery between trips so all was well. Total cost of the solar & controller was about 20 quid on amazon. The battery was from a scrappy.


My current catamaran has 1kw of solar feeding a 300ah 24v lithium system. The difference is I now have two kids and a wife that wants home comforts and I'm considering electric propulsion. Horses for courses.