Solar Charging Question.

Jeff

I'll watch this one with interest. Pity you can't afford an 80W panel. But that aside .. a 6W will only give you 500mA, so if your 80/100A alternator isn't up to the job I can't see how a little squirt like that would help. Similarly for the 10W.

But as I say I'll watch with interest as I may be missing something.

Cheers

Jeff M, This is just a short answer because you don’t say why you want to get that last 5% to 10%.
The reason I ask is because if the reason is to get a bit more operating time out of your battery the it would be, providing you have the room, more economical to install another small battery, which would give you about 40 to 50% increase in storage capacity for less than the cost of a 5 watt solar panel.
If you are looking at the solar panel for a different reason then this may not be the answer.
Cheers=

Jeff M, if you specifically want to use a solar panel, for what ever reason, a 5 watt panel would be able to charge your battery but the time it would take depends on a number of things. The size of the battery, it’s condition, state of charge when you connect the panel up and so on.

Those little 100ma trickle panels can maintain most batteries so a 5 watt panel, which is about 250 to 300ma max would give you some benefit.

Also, you would not need to put a regulator on such a small output panel, the voltage difference between the battery and the maximum output current of the panel means that the battery would rarely get much over 14 volts, if at all.
Cheers

Hi again Jeff M, the 5 watt panel would probably do the job, taking into account that the battery will probably be near full charge by the time you get back from each of your trips, depending on how long you drive on the return trip.

Because there is such a short time between your long trips, you would probably get a greater benefit from a 10 watt panel because it can obviously put that little more into the battery in the short time available.

Again, I don’t think you would need to fit a regulator for the same reasons I posted earlier. It would still pay you to keep an eye on the battery’s voltage for the first few weeks to make sure the voltage does not rise to high. Again, the voltage difference between the battery and the solar panels output is pretty well going to guaranty that the output current of the panel is still not going to be able to raise the battery’s voltage to a damaging level.

The 10 watt panel is going to be a bit expensive for what you are using it for but on the other hand, the panel is going to be able to supply top up power for this battery and probably you next 5 or 6 batteries so over all it’s not that expensive.

Cheers and hope this is of some help.

And if anybody has any legitimate cirisisim please jump in.
We can all learn more then.

Jeff,

11 watt solar panel $290 (retail) you can also get smaller size & $$ panels.
http://www.solarpanelxpress.com.au/Products/products_solarpanel_unisolar.htm

As a solar user of 9 years experience, I can only say; whatever you use will be a big improvement.

The link above states a solar regulator is not required on a 11 wt panel when charging a 85 a/h battery.

It depends on what you want (or don't want) to spend.
Check out 2nd hand panels as it's very easy to check if they are working correctly.

I picked up a 10w panel from Jaycar for $129. Use that to charge the wet cell on the trailer for lighting and charging stuff like phones and laptop. We spent 2 weeks away and it still had plenty left in it. Probably only had it connected for about 6 hrs a day for a week.

Michael

Well I'm no expert but would it be simpler to upgrade your alternator or do you already have a big one. OR, I remember seeing an ex-ambulance in a workshop that had twin alternators, which the mechanic told be was standard issue on them.

Just some thoughts.

Cheers,

Mark.

Jeff M, one suggestion, why not get a 4 or 5 watt panel and see if it works. If it does great you have saved some money but if you find that it is not enough to achieve what you want just add a second panel.

Doing it this way, if you do have to add another panel, it will cost a little more than just buying a 10 watt panel in the first place but I personally think you will be OK with a 4 or 5 watt panel BUT this is my opinion not a scientific fact so don’t scream at me if it doesn’t work.
Cheers and I AM sure the smaller panel will do the job.

Oh by the way, the reason for isolating the solar panel is to avoid having the panel damaged by voltage spikes. It is not all that common to happen but for the few dollars to guaranty it won’t, I’ll leave it up to you. Also some of the panels are supplied with literature that gives you more of an idea as to how and why to connect the panels up to a powered source.

Thanks Jimbo and yes I was just ignoring him and don’t get yourself kicked off because of the moron. Cheers.

G'day Jeff

I'm a novice at this stuff but I have a question for you. When you say charging the battery from a charger it keeps the voltage up for about a week or so, what sort of voltage are you talking about? 12.5? or more?

I'll have to catch up with you one of these days and check out that rig of yours, I'm becoming a western australian next month (missus is from over there and has talked me into it) :)

Hi Jeff M, here is a question regarding your original post. Irrespective of what size solar panel you get, as you say, you drive for about 15 to 20 minutes avery day. If this the solar panel manages to charge the second battery up over 14 to 14.2 volts then when your isolator cuts in wouldn’t any additional voltage simply be transferred to the main battery because of battery equalisation. The instant the alternator sensed the higher voltage, it would just back off until the voltage came back down to the required operating level.

This is just a theoretical suggestion and if it is correct then there could be two possible out comes as well.

One, any beneficial boosting of the second battery would be lost when the two batteries equalised.

Two, the flip side is that even if the solar panel was big enough to push up the second battery’s voltage, every time the vehicle was driven, the batteries would equalise and in doing so keep the second battery’s voltage in check and this would mean there is no need for a regulator no matter how big the solar panel is.

One more thing, at the end of each mowing season, I connect my mower battery up to a 100ma solar panel and this has made sure that at the beginning of the next season, after 4 to 7 months of not being used, I have a fully charged battery. I’ve done this for the past 5 years and still have the same battery. Your situation is only slightly different in that you are going to be charging a bigger battery in a much shorter time, but I can’t see why it won’t work without fitting a reg.
Just some thoughts, cheers