Portable power!

[eddie3000]

I've read many people talk about leisure batteries for powering mounts and stuff in places with no available plugs! I would like to power my mount, camera and laptop, at least. I thought of a small generator, but I think the noise will be quite annoying. Until now, I have used a 12V socket in my car's boot, and after an hour or two, started the engine to avoid complete discharge.

Does anybody run a mount, camera and laptop at once and how? Are leisure batteries the only way?

I've seen that audio freeks :headbang:have an extra battery in the boot to power their high power audio systems, and that it charges as you drive around. Anybody know anything about that? Are they normal car batteries or deep cycle ones?

[eddie3000]

I guess the silence means that leisure batteries are the way to go! Or a noisy generator, or my car engine running....

[Bizibilder]

Leisure batteries are the things to use rather than a "car" battery. To work out what you need the battery is rated as so many Amp-Hours (Ah). 1Ah will run one amp for one hour. My own mount draws 2amps so a 50Ah battery will (theoretically) run it for 50/2 = 25 hours.

BUT you should not run the battery right down ! so best to use, say, 50% of its nominal capacity. Therefore a "2amp" mount could run for 12.5 hours with no problem (ie for a whole night in the winter).

To find the capacity you need add all the bits you will be running from it: Mount 2A, Dew heater say 4A camera say 1A makes a total of 7amps. Therefore a 75Ah battery will give you around 5-6 hours use (which for most of us is a longish session in the winter!).

You will also need a Proper charger - NOT a car charger! - these are designed to charge and maintain a battery. (I'm no electrician so ask the supplier or wait for a more qualified person than myself to get details - there are several threads on the forum).

Hope this helps you decide.

[JamesM]

Leisure battery is the way to go. Funnily enough I have recently been asking the forum about which unit could anyone recommend to convert the domestic supply to the 12v needed to supply the mount. When I considered the cost and realizing that half of my observing isn't at home but out 'in the field', I plumped for a leisure battery which I could also use for both occasions.

Bizibilder is correct in his calculations. I bought a 105AMP (pretty heavy) which is ample for my needs in supplying enough juice for all my toys. The reason for this large size is because I also wanted something I could take with me when camping or attending a star party where you might not be able to access power for a couple of nights. I tend to go camping in more isolated locations to avoid light pollution found at some campsites. The only problem I had was finding the correct 'female' connection to link the mount etc with the battery. I did receive suggestions here about making my own, which is fine if you feel competent to do so but what I wanted was to buy something off the shelf. Maplins will sell you all types of multiple splitters that allow you to connect more than one item but they all have the male positive point connection which assumes that you are going to plug these splitters into a car socket, which is the female connection already wired up. The answer I discovered was found at my local camping shop where they sell the female connector which attaches to the battery via crocodile clips and has a nice red LED light to show that its working, cost £7.00.

I also think that leisure batteries are better value than the astronomy power packs you see everywhere which have all sorts of lights, bells and whistles on them - most of which you don't need or are unlikely to use and which makes them very expensive for the length of charge they give you. Hope this helps.

James

[Psychobilly]

Ring do a nice little 4 way adaptor with one High current and 3 medium current output sockets that has a 3 LED traffic light style battery level indicator....

Peter...

[eddie3000]

So the leisure battery it'll have to be then. My brother in law has a petrol generator I could borrow, but the noise is quite annoying.

What I have in mind, when I have the time, is to build a leisure battery charger that is permanently fitted in my car with the battery, in the boot, safely fitted. Like a permanent sort of thing. The idea would be that the battery is charged as I drive around so that it is ready when I go out in the field. It should also be possible to connect the charger to the main 220Vac if quicker charging should be required. I don't know when I'll get round to doing this project, but I think it might be an interesting idea.

There are a few things I have to consider, maybe you can contribute with your knowledge and/or own ideas.

In Spain it gets very hot, the interior of a car parked in the sun can easily reach 70ºC, and maybe even more. Winters in Zaragoza rarely go down to -10ºC, and normally are around 0ºC.

Also, driving around will not provide a full charge in one go, it would cahrge the battery a bit at a time. The electronics involved I don't think will be a problem.

Do you think that these conditions are tolerable for this type of battery, or is it best to load and unload the battery every time it is used? Is the comfort of having a permanent power supply in the car worth the stress the battery will suffer, thus probably reducing the number of complete charge/discharge cycles?

I guess the most simple idea (loading an d unloading the heavy battery from the car) is the way to go (less potential damage to the battery).

I don't half go on, do I?

[Psychobilly]

here you go Eddie...

Split Charge Circuits - MarcleLeisure.co.uk

Peter...

[oshb5]

I picked up a rechargable camping unit from the car boot the otherday with leads and is fine also just added the aldi 3car cigarlighter and usb sockets to it and now its even better

[danielhenry31]

Free batteries are cheaper than the power package of astronomy to see everywhere, all kinds of lights, bells and whistles of them - most of them probably do not need or use, and makes it very expensive for the charging time will give .

[Bryndalf]

I have put a split charge unit in my VW van. This charges up the leisure battery when I drive and disconnects it from the starting battery when it notices the V drop. I routed some cable into the rear and added a fusebox and then a car cigarette socket. My HEQ5 pro now plugs into this and runs great.

[eddie3000]

Yes, that's more or less what I'm after. A leisure battery in the boot, like in your van Bryndalf. What electrical design/layout did you use? What is the circuit that detects the voltage drop like?

I also like the circuit Psychobilly posted earlier. Very simple, and probably effective too.

What worries me most is the security of having a battery in the boot. Not just the mechanical installation, but the extreme temperatures inside the car in summer. I measured 79ºC the day before yesterday inside the car in the sun. That's my fault for choosing a car that's dark grey, almost black:o. I don't know whether that's dangerous or not for the battery.

I have also read a bit about charging and topping lead-acid batteries, and apparently, to ensure a long battery life, the voltage has to be adjusted depending on the temperature. And given the fact that I get temperatures around zero (and sometimes below) in winter, and such extreme temps in summer, I think that designing a charger that varies the charging voltage depending on the temperature is a good idea. What do you think?

I'll tell you what I do when and if I do something, I'm a wee bit busy lately with other things.

THANKS:icon_salut:

[nibber]

Have you thought about using a caravan type split charge relay,i wired up a twin electrics caravan towbar recently and used one for this it charges the second battery in the caravan and runs the fridge when you are travelling,but cuts off wnen you kill the ignition, the relay senses voltage when you have the engine running (charging) the car battery etc they cost about £12 IN UK,if you google for split charge relay or caravan twin electrics you will get a few circuit diagrams up that will show the split charge circuit/relay wiring.

Regards nibber