Solar Battery Charger and charging a spare car battery?

khampson

Hi, I have Lucas premium 3 car battery which has a rating of 370 cracking amps and 43AH capacity, how long would it take to charge using one of these?

http://www.amazon.co.uk/Solar-Battery-Charger-ideal-Caravans/dp/B000R0UBT8/ref=sr_1_5?ie=UTF8&qid=1334046043&sr=8-5

alternative is a 12v cigerette charger that only works with the engine running, I only use the battery for additional 12v lighting in the back of my van, however I was tempted to buy a 12v kettle to run on it which will proberbly zap power, but if the solar panels recharge it enough to keep it usable if I boil the kettle a couple of times a day?, or can I use both 12v + solar to recharge it at the same time?

If that battery does go flat I can use the car battery with the engine running if I get desperate.

Someone suggested ideally to me I need a relay charger but the problem is its a works van and I can not modify it in anyway.

I can also recharge the battery at home using the standard 240v charger.

What are my options and best way forward.

Thank you.

Strider590

Don't bother......... It's not a "charger", it's job is to trickle charge AND it's barely suitable for that.

There's another one on Amazon, it's around £20, it's a briefcase type thing outputting around 5 watts.

I use one of these in my garden to keep a small electric fence battery (keeps slugs/snails off my veg patch) charged up, it's barely managing to keep that up to charge. In fact the battery now reads (after a weekend of cloud) 12.2volts, when a 12v battery should be reading 13.8v when fully charged.... And this is just a 7.5aH battery.
The constant battery drain is less than 30mA, the charger is rated at 330mA.

Also don't forget that even if a solar charger outputs around 300mA @ 14v (on a very sunny day), you have to remember that the potential difference between the battery and the charger is NOT 14v, it's only going to be around 2v (VC-VBAT), which means you won't be able to achieve anything close to the rated 300mA charge.

The average car draws 200mA (but no more than) with the ignition off..... A disconnected car battery has a self discharge rate of 3-20% per month, that's at least 50mA constantly with nothing connected.

PLUS solar panels don't like heat, in fact on a hot day once the panel starts to heat up, it's efficiency could drop by upto 80%.

patman99

I bought a 12watt unit from Maplins 6 years ago. It charged my van battery from flat to full in 8 hours on a sunny day.

forgotmyname

12watt panel = 1amp hour. So your battery was 8amps?

The panel in the OP is probably 1.5watts max.

So about 9 hours of full sun for 1amp

387 hours of fairly strong sun to charge that battery from flat.

I use several of those to keep my caravan battery charged, But it has no current drain from any external source.

I still charge it with a proper CTEK charger though to keep teh battery in good condition.

khampson

Just had a thought, I have an 150w inverter, could I use this and a standard car battery charger, soI havea inverter with a car cigarette socket,I havea charger that I use in my garage, if i plug this in to the inverter and then connect it to my spare battery, assuming the car charger is no more than 150w it should charge pretty fast right?

Just another thought, is it safe to charge the spare battery with me in the vehical? I read somewhere that they can give off gas?

Keith

molerat

http://www.ebay.co.uk/sch/i.html?_from=R40&_trksid=p3984.m570.l1313&_nkw=split+charge+relay&_sacat=See-All-Categories is what you need, keeps battery charged all the time without any risk of draining the main battery.

Strider590

khampson wrote: »

Just had a thought, I have an 150w inverter, could I use this and a standard car battery charger, soI havea inverter with a car cigarette socket,I havea charger that I use in my garage, if i plug this in to the inverter and then connect it to my spare battery, assuming the car charger is no more than 150w it should charge pretty fast right?

Forgetting the fact that your suggesting infinite energy (akin to perpetual motion).......

Inverters are horribly inefficient, it would drain far more from the battery than it would output.

khampson wrote: »

Just another thought, is it safe to charge the spare battery with me in the vehical? I read somewhere that they can give off gas?

Only if over-charged, but as this is hard to detect I would recommend ventilation.



I really think your only option here is to keep the engine running whilst using your water heating device.... A simple drop in element in a mug of water isn't going to take very long to heat at all.

khampson

molerat wrote: »

http://www.ebay.co.uk/sch/i.html?_from=R40&_trksid=p3984.m570.l1313&_nkw=split+charge+relay&_sacat=See-All-Categories is what you need, keeps battery charged all the time without any risk of draining the main battery.

These do look a good option but I am useless at wiring and mechanical stuff, are these easy to fit and will it invalidate the warranty? But yes if I can get one fitted no problem, but do these have a cut out when second battery if full, someone's suggested gases can be released if over charged, I have no ventilation in my van other than windows and doors.

khampson

Will this charge my spare up?

http://www.ebay.co.uk/itm/EASY-START-ENGINE-STARTER-12V-SOCKET-NO-JUMP-LEADS-/230566075880?pt=UK_Recovery_Tools&hash=item35aecf1de8

used with these:

http://www.ebay.co.uk/itm/Car-12v-power-socket-cig-c-w-battery-crocodile-clips-/140509915242?pt=LH_DefaultDomain_3&hash=item20b70b286a

Strider590

khampson wrote: »

Will this charge my spare up?

http://www.ebay.co.uk/itm/EASY-START-ENGINE-STARTER-12V-SOCKET-NO-JUMP-LEADS-/230566075880?pt=UK_Recovery_Tools&hash=item35aecf1de8

used with these:

http://www.ebay.co.uk/itm/Car-12v-power-socket-cig-c-w-battery-crocodile-clips-/140509915242?pt=LH_DefaultDomain_3&hash=item20b70b286a

First of all, Item 1....... Jeeeeeeeeeeeeeeesus, I cannot believe they're selling that!!!!!!! it'd at least blow a fuse if not fry your wiring loom trying to "jump start" with that lead!!


Item 2, pretty standard stuff.

What your proposing is to connect the 2nd battery in parallel with the main battery, there's nothing essentially wrong with that as long as the alternator can handle this and as long as both batteries remain at almost the same level of charge, if they differ, then a higher than normal current will flow from one battery to the other and once this reaches around 20amps, will blow the lighter socket fuse.

Say for example your main battery is 65aH and the secondary is 45ah, your total capacity is now 110aH, your effectively increasing the charge capacity across the 2 batteries.....

It would work if you inserted a 2 ohm power resistor (at least 50watts) on the positive lead to the lighter socket, this would limit the current flow between batteries and prevent it blowing the fuse.

You could then charge the battery, disconnect it for use and then reconnect it to charge again afterwards.

espresso

khampson wrote: »

These do look a good option but I am useless at wiring and mechanical stuff, are these easy to fit and will it invalidate the warranty? But yes if I can get one fitted no problem, but do these have a cut out when second battery if full, someone's suggested gases can be released if over charged, I have no ventilation in my van other than windows and doors.

The only sensible advice posted in this thread has been by molerat!

If you can't follow the simple instructions provided yourself then pay someone who can!

This here is an intelligent self switching split charge relay kit.