Is a 5W solar panel too big???

Don't even contemplate using the panel without a regulator. Most regulators also prevent your battery/s from discharging back through your panel after the Sun goes down. You can use diodes to do this but the regulator offers other advantages too.

If your battery charger is going into float mode, why not just leave it connected instead? If the regulation within the charger is any good, you won't overcharge your battery/s anyway!

Turn the headlites and stereo off before you go away! (Sorry just a smarta..e comment)
What are you running on there, that makes it impossible to go 9 days without a run?? Perhaps you may just need a new battery?
I too work fly in/ fly out, but 5 weeks on/5 weeks off and my diesel hilux (1992) starts no worries at all.
Try disconnecting the battery when you go away, if it starts when you get back then something is draining it. If it doesnt then the battery is knackered.

bottom line though, you shouldnt need to charge a car for a 9 day layup, watch that you arent just fixing a symptom rather than the problem itself.

Either what he said, or go to Bunnings and get a timer to turn the charger on for 10 mins a day.

CHEAP CHEAP

Ask an old auto electrician let me give you my thoughts...

If you have a 3 stage charger.. just leave it connected all the time. It won't hurt. My CT has a 3 stage charger connected permanently for months at a time. They really are good for your battery.

However, even without the charger, your battery shouldn't have any problems normally for the period you're away. We have a BMW Z4 (for when the Disco just isn't fast enough) and it often sits for up to 6 weeks and always starts first go when we want to drive it. The battery in the BMW is now some 2 years old and gives no problems. If you are having problems without the charger, I would suggest you either have an electrical leak or else your battery is simply stuffed. Modern car radios draw small amounts of power all the time to memorise station settings etc but this should not worry your battery. In fact back in the 60s when I was working with VDO they produced a volt meter that was designed to stay connected directly to the battery all the time. The small current draw actually stopped the battery from sulphating and gave longer duration to the battery's life when not in use.

Hope all this ramble helps.

Cheers

Mark Taylor

Hi Steven

I have a boat with 2 big deep cycle battery's and I have a solar panel and was recommended to fit a Megapulse unit to the battery's .

I have had no problem's at all.I have no 240 avalible to me.

Scoof

I do the same for my boat battery BUT I use a 5A regulator from Jaycar (german made even) was only about $28 - the panel was a gift from a bloke who had no further use for it - 10W (17V - .7A) - hell - I had to use it somewhere ! See [ Site Link ] for a pic - the first two would be ok for your application it seems - I emailed Kemo re diodes to stop back flow of energy after sundown - the 5W does have a diode not sure on the smaller one (but probably does).
As mentioned above, the smarty pants 240V multi-stage chargers do claim to be designed to connect and forget, until the next use .... whatever.

Thanks Guys for all your input.

I reckon I may give it a go with an el-cheapo regulator as Darian has suggested.

I too had thought of leaving the 3 stage charger connected; but it's a big fella and I'd have to leave the bonnet open for those 9 days. Also, (just due to the layout of our carport) my missus would go off at me "with all those cords everywhere getting in the way". For those reasons I won't leave the 3 stage connected.

As others suggested, I may simply be treating symptoms rather than problems,; so I'll probably look at renewing the batteries sooner rather than later. Mind you, I'd still embarfk on this exercise even if I had new batteries as I believe in keeping them "topped up" as a way of extending their useful life.

Thanks to all who have taken time to reply with varying ways off looking at my situation - much appreciated.

Cheers
Stephen J

Hi Stephen, a 5 watt panel does not put out enough to justify putting on a regulator for one battery, you could put a 10 watt panel ( available for around the same price ) on the cranking battery and still not need a regulator.

Between the low current output of a 10 watt panel, less than an amp at it’s best and the internal resistance of even a fully charged battery, the voltage would be naturally regulated.

Now the one question that no one has asked and is probably more important than all the rest, just how long do you actually drive the vehicle for, when you are home.

The amount of time you have the motor running will have the greatest effect on the ability for the batteries to be charged and hold a charge.

Cheers.