Allotment Gardening Advice Help Chat

Chatting => Design and Construction => Topic started by: SnooziSuzi on October 10, 2022, 14:49

Title: Solar panels to trickle charge a car battery... what do I need?
Post by: SnooziSuzi on October 10, 2022, 14:49
Hello all,  It's been a long long time since I posted anywhere on this forum, but I know you guys know your stuff so I'm turning to you again.

Hello to everyone that may remember me  :tongue2:

When I get my shed built I would like to include a small solar panel to trickle charge a car battery so that I have power to charge my phone, or run a light (LED) or maybe even charge up some cordless power tools if and when I get some.

I have searched, and there are old threads relating to solar power but none really answered my basic question:  What do I need to get?

The power would only be drawn on a weekend normally, so the panel has all week to charge the battery, so I don't think I need a particularly heavy duty panel; 100w should do it, I think.  My thinking behind this is that on normal days we should get from 8 hours of daylight in the UK (I'm in Durham, so 54 degrees North) so that could be up to 800w daily, over 5 days (power would be used at the weekend, so I didn't count those days) so up to 4kw a week potentially, although I don't need that much power and the reality is that in winter there may not be that much usable daylight anyway.

Should the inverter be the same as the panel wattage?  If the inverter was rated at 500w, what would the effect be?

What do I need to look out for for the battery? i.e. is a car battery better than a truck one, etc?  What about lead acid vs lithium ion? 

Thank you in advance for looking at this and I hope to be chatting with you soon  :wub:
Title: Re: Solar panels to trickle charge a car battery... what do I need?
Post by: Aunt Sally on October 10, 2022, 16:30
Our Mr G (Growster) will probably have the answer for you.  He’s our Mr Fixit here.
Title: Re: Solar panels to trickle charge a car battery... what do I need?
Post by: SnooziSuzi on October 10, 2022, 16:42
I knew someone would know  ;)
Title: Re: Solar panels to trickle charge a car battery... what do I need?
Post by: Aunt Sally on October 10, 2022, 18:53
Ohhh.. seems I was wrong (a very rare occurrence), Mr G tells me that after a very unpleasant experience with an electric cooker he is banned from sparks and only allowed to play with mechanical projects.   :ohmy: ::) :nowink:
Title: Re: Solar panels to trickle charge a car battery... what do I need?
Post by: Growster... on October 11, 2022, 06:17
Phew, thank you Aunty!

The memory of that incident still causes a huge shudder, and you may remember that some time ago, our garden muncher suddenly stopped, and I went to see what the problem was WIThOUT TURNING OFF THE POWER...

I was suitably chided by everyone here, so that's another reason why sparks are left to someone who actually knows what they're doing - sorry Suzi...:0(
Title: Re: Solar panels to trickle charge a car battery... what do I need?
Post by: SnooziSuzi on October 11, 2022, 09:02
Oh dear!   :lol:

I can imagine that would definitely curb your enthusiasm for playing with electricity, haha. 

Nevermind, hopefully someone else might spot the thread and chip in when they can.  I do have a friend who is an electrician and have tried to get him to explain it to me, but he isn't qualified to do solar projects (you need a special qualification for that  ::)) and he went off on a tangent about things that went way over my head and despite my pleas for "keep it simple" just confused me more, haha.

I've also been watching a few YouTube videos (what did we do before YouTube, eh?) and I think I'm a bit better informed now, but first hand experience is definitely better.
Title: Re: Solar panels to trickle charge a car battery... what do I need?
Post by: Lardman on October 11, 2022, 09:14
https://footprinthero.com/diy-solar-shed-lights

Probably has all the information you need. The safety consideration being the peak amps outputted from the panel.
Title: Re: Solar panels to trickle charge a car battery... what do I need?
Post by: SnooziSuzi on October 11, 2022, 09:18
Brilliant! Thank you Lardman, this is exactly what I needed; an idiots guide to it!

I shall study it in more depth after work  :D

Suzi
Title: Re: Solar panels to trickle charge a car battery... what do I need?
Post by: lettice on October 13, 2022, 09:07
There are plenty of kits these days that cheaply provide all you need.
A good one that fits your need in link below and the site has a lot of useful information is;

https://www.photonicuniverse.com/en/catalog/full/41-100W-12V-solar-charging-kit-with-10A-controller-and-cable-German-solar-cells-for-campervan-caravan-boat-off-grid.html?gclid=EAIaIQobChMIiNad5dzc-gIVjq3tCh21Pw0CEAAYAiAAEgLgPfD_BwE

A few I know in some beach huts near me have used kits from this company very similar to this one and do exactly as you are asking.
Title: Re: Solar panels to trickle charge a car battery... what do I need?
Post by: SnooziSuzi on October 13, 2022, 09:44
Thanks lettice,  yes, there are kits, but they don't provide everything and it's the bits they don't provide which I need to get right!  I want to store the energy in a battery to charge power tool batteries, which range from 14v to 40v, so clearly a 12v system won't do, and I need to be sure that whatever inverter I get is the right one. 

The last thing I want to do is burn down my shed from having the wrong pieces attached to my system!

After looking at the link provided by Lardman, and also finding Will Prowse's YouTube channel on solar sytems I'm beginning to understand a lot more about it now than when I started this thread  8)
Title: Re: Solar panels to trickle charge a car battery... what do I need?
Post by: Dantheman on October 13, 2022, 12:27
HI,
Not sure of your budget?  Here's a few bits I would suggest.

Panel: - https://uk.renogy.com/renogy-100-watt-12-volt-monocrystalline-solar-panel-compact-design/?gclid=CjwKCAjw7p6aBhBiEiwA83fGupVRVUo4Irf9yvGX5l2rmM8frobJ0Eg1CYPSkTB_-9XBctIF2sleahoCefcQAvD_BwE
or https://uk.renogy.com/200-watt-12-volt-monocrystalline-solar-panel/?gclid=CjwKCAjw7p6aBhBiEiwA83fGupom-sNbOrttPcs52pxW-cmhWt6SmPmgc_2XD7MJaduqu5i8WMqXjxoC7zEQAvD_BwE

Charge controller: - https://www.ebay.co.uk/itm/254740080338?var=554529864401&mkevt=1&mkcid=1&mkrid=710-53481-19255-0&campid=5338365712&toolid=20006&customid=EB71545101&

If budget allows:- https://www.ebay.co.uk/itm/234053857079?epid=17019840363&hash=item367eb26f37:g:SnIAAOSwspVixCBm&amdata=enc%3AAQAHAAAAsH4bU2XMk2uikmGcuTnp86Mxk4Fhy%2BvypJhbbZAzPJS6BrNZFUAUeoMhIRcCchEqJcWmwfBNBbJetYrD3AxeX180telImPdp8zmpIlIVKsVoSnY5WQjdyvepLugDWUW9zLdeB1USYBBVFXzNg%2FFuHYvbYHLKhMAVo16wYitJO8lEyGE4pGFG3FE04VI2K7B3o%2FfLTzxnaT5D0LtUoUZ7iZEXmHeDz%2Fsev8YhmVBmJfdK%7Ctkp%3ABk9SR8CM75D6YA

Fuses: - https://www.ebay.co.uk/itm/143330671249?hash=item215f2c7a91:g:gqcAAOSwCzJdLekS&amdata=enc%3AAQAHAAAAoJb1%2BW4nNh4AURDffNZQ7Ecg8WCxV1g7t5xY3KCBvNzb8Rbw%2Fah8Bdm3XRPJ30sYGP%2BRLFbTquvJX4XTRfBIreZkjnutJPTyc9gYhu%2FwzJlP1LDXl9lWKvT2KfaaSxfxRYpT5FyeJjz7ozIXGWUpTRgiDov1HLZRRMVW2rs7x%2Fh1mf1gokZJg67oY7DBUtIG2Xqlwizqjy86IJHn9dmCepI%3D%7Ctkp%3ABk9SR_jlvJD6YA

Depending on what power tools you want to charge.

Invertor: - https://www.ebay.co.uk/itm/304612056186?hash=item46ec4b1c7a:g:8W0AAOSwYmhjDC6B

If your budget allows:- https://www.amazon.co.uk/Victron-Energy-Phoenix-Inverter-VE-Direct/dp/B07W947JW6/ref=asc_df_B07W947JW6/?tag=googshopuk-21&linkCode=df0&hvadid=375433475241&hvpos=&hvnetw=g&hvrand=7626610442859670764&hvpone=&hvptwo=&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=9045159&hvtargid=pla-829700537491&psc=1&tag=&ref=&adgrpid=79769156594&hvpone=&hvptwo=&hvadid=375433475241&hvpos=&hvnetw=g&hvrand=7626610442859670764&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=9045159&hvtargid=pla-829700537491
better on power consumption.

Battery:- https://www.amazon.co.uk/SuperBatt-Leisure-Marine-Battery-Replace/dp/B01DT679GY/ref=asc_df_B01DT679GY/?tag=googshopuk-21&linkCode=df0&hvadid=310315668927&hvpos=&hvnetw=g&hvrand=17227445044743642985&hvpone=&hvptwo=&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=9045159&hvtargid=pla-709504368363&psc=1
The more AH (amp hour) the better.

If your budget allows:- 12v lithium ion battery as these allow for more of the energy (AH) to be used but they are a lot more expensive but last 3 times as long.

Get the correct wire size too.

Hope this helps.

Thanks Dan

Title: Re: Solar panels to trickle charge a car battery... what do I need?
Post by: SnooziSuzi on October 13, 2022, 12:38
Thanks Dan!   So (and please forgive my ignorance on this; maths and physics aren't my forte) if I wanted to charge, say, a 20v cordless power tool, because of the inverter changing the power from 12v to 200-240v as with the one you have suggested, it doesn't matter that the battery is 12v.  Is that correct?

I'm only just getting my head around what is needed and everywhere I see tells me that it should be easy, but everything I read just confuses me more  :wacko:

You have taken a lot of time to put all of that together and I really appreciate it.  I'll keep this thread updated (or I'll start a new one) with my progress.... now I just need to write a letter to santa  :tongue2: