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Author Topic: 12v Car battery charger, mains/solar  (Read 2276 times)
Greenbeast
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« on: March 31, 2015, 08:37:04 AM »

I need to charge the battery in my tractor, and we're going to have electric fencing within a month.

Both could do with being kept topped up with a little solar panel but i also need to mains charge.

What sort of things should i be looking at?
Any old mains charger from ebay?
What about solar, i can scrounge a little panel i think but do i need a charge controller?
« Last Edit: March 31, 2015, 09:22:45 AM by Greenbeast » Logged
biff
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« Reply #1 on: March 31, 2015, 09:58:53 AM »

Good morning GB,
               There are small suitcase PV chargers available, (1.5watt+) They come with a range of connectors and a little controller that prevents overcharge. I have one directly connected into my twin 130ah x 12v truck batteries which power the winch that raises and lowers the tower. It does a great job. Leaves the batteries topped up and ready for action all the time.
    Now you could buy a small 10watt  PV panel but if it sits for prolonged summer periods,there is a chance it could boil dry so you would have to buy a controller as well.
   I used a solar pv 185watt panel on my digger batts (24v) for years,especially if it had been sitting up for months, I used to connect up the panel and leave it for an hour and while still connected,birl the starter. It never failed to start. (Terminals disconnected to save alt)
   So you have a choice there. long term small watts,(suitcase charger)with its protective controller and short term decent sized PV panels for an hour or so in decent sunlight, You can always keep an eye on it with the volt meter.
                                                                       Biff
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Greenbeast
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« Reply #2 on: March 31, 2015, 10:49:52 AM »

any recommendations for mains charger?
i feel like i will need one of those anyway
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dhaslam
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« Reply #3 on: March 31, 2015, 10:54:16 AM »

You can use ten watts PV for  a normal car battery without a controller.   I have had ten watts per battery on  my boat for ten about ten years.  They charge the battery when  used but don't do any damage when  the batteries are fully charged.It  is better to use bigger panels and a charge  controller but at the time the  panels cost a total of 160 for 20 watts.
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biff
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« Reply #4 on: March 31, 2015, 03:24:34 PM »

It is difficult to work put the ratios,
                               watts per ah or in my case watts per kg of lead. I have tried various combinations over a period of years. I assumed that a good 800ah x 24v hawker forklift pack would have no trouble coping with a direct 330watt of solar pv vmp36. Indeed as time went by the voltage never seemed to get beyond 29.4 in the pack. However, there was need to top up the cells more frequently because there was that extra bubbling and hissing going on and if left unattended the pack would almost certainly boil dry in a couple of summer months. So the answer lies in a combination of the two methods. Direct pv to the pack when in attendance and through the controller when absent.
Then again,  In the beginning, I thought that the 1.3Watt suitcase charger would be a waste of time but I was pleasantly surprised to discover that the Batteries were in top condition anytime I went to use them. These same 2 x 130ah x 12v batteries which power my winch are over 12yrs old. PV charging never ceases to amaze me.
                                                                               Biff
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chasfromnorfolk
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« Reply #5 on: March 31, 2015, 06:41:26 PM »

I bought a used Halfords 'Automatic' from ebay like this one: 141621935040 on the basis it was one that claimed it could be left connected to maintain a battery, and I wanted to do just that - keep a spare car battery in reserve, fully charged, in case I needed one instantly for the lighting or shower in the holiday unit I have... never regretted the purchase, performs perfectly.

But

I also have a 5w and 10w panels (with built-in overload protection) hooked to batteries on site, and over the past 2 seasons, touch wood, neither battery has needed replacing having got their charge from the panels in pace with the use.

So any or all of that kit would probably do the job for you too. As Biff said elsewhere, car batteries seem to like PV.

Chas
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Scruff
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« Reply #6 on: March 31, 2015, 09:47:17 PM »

What car battery chargers say an do are two completely different things in my experience. I had a Halfords one (not the same) for a while...the float is constant current so while they claimed it could be left connected it really oughtn't. Proper job float charger: charge rate = self discharge rate.
The Victron Blue Power IP65 does this, pricey though, it also load compensates very well.

Are you planing on a solar powered electric fence? That's gonna take a decent enough module. The little 5W modules are ok for engine batteries provided the vehicle isn't putting a constant load on the battery.
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Greenbeast
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« Reply #7 on: March 31, 2015, 09:57:45 PM »

yeah we're looking at this:
http://fearing.co.uk/pig-metal-3-line-solar-kit
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Scruff
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« Reply #8 on: April 01, 2015, 02:53:24 AM »

That module looks much smaller than I was thinking. In hindsight it's high volts, tiny current and intermittent...so not very much power needed at all.
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