Solar Charging Question.

Submitted: Wednesday, Feb 09, 2005 at 16:47
ThreadID: 20281 Views:2672 Replies:11 FollowUps:50
This Thread has been Archived
Ok, there's been a quite a bit of discussion about batteries, charging and solar latley but I've had an idea and want to know if it's worth bothering with.

SO TO ALL BATTERY EXPERTS:

BACKGROUND
My Auxillary battery (which runs all accessories, internal lights, cooler etc) is an 85amp//hr Wet Cell. It obviously doesn't get a full charge of the vehicle's alternator but get's pretty close.

About once a month or before a trip I give it a good charge with an 8amp 240v charger which seems to bring it voltage up nicley for about a week, then it drops again obviously struggling with the alternators charge.

QUESTION
If I were to permantally install a solar panel on the roof connected via a solar 3 stage regulator, what would be the minimum size panel I would need to fully charge the battery. I'm not interested in trying to charge the battery only via sola, I'm not interested in trying to stop the battery going flat under load.
All I want is the solar to be able to finish the job the alternator has started but can't complete fully. That is give the battery the extra 5% or 10% charge it's not getting from the alternator.

And no I can't afford an 80w pannel.

I was thinking of a 6w or 10w style panel, would it have the guts to charge it?
The car is currently parked outside even at home so it would get plenty of sunlight.
Back Expand Un-Read 0 Moderator

Reply By: Rosco - Bris. - Wednesday, Feb 09, 2005 at 16:56

Wednesday, Feb 09, 2005 at 16:56
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
AnswerID: 97490

Follow Up By: Member - Jeff M (WA) - Wednesday, Feb 09, 2005 at 17:00

Wednesday, Feb 09, 2005 at 17:00
More to do with the voltage not the amperage is where I'm comming from.
Solar Pannels typically give out 17-18v DC regardless of how much sun/amps they are receiving supplying. The Regulator can then drop that down to say 14.1 or 14.5 or whatever the bat needs to get a full charge. The Alternator with all the gear running can really only hold 13.8v DC If I turn the headlights off (which I don't do normally) it goes up to about 13.9VDC 14VDC. Still not really enough to give it that last 5% - 10%.
0
FollowupID: 356069

Follow Up By: Rosco - Bris. - Wednesday, Feb 09, 2005 at 17:08

Wednesday, Feb 09, 2005 at 17:08
True, but don't you need amps to charge the batt? I've got one of those little Dick Smith ticklers for the CT batt and it puts out up to 20V but very very little milliamps. It will never charge the battery, merely give it something to think about. Wouldn't the same apply??
0
FollowupID: 356071

Follow Up By: Member - Jeff M (WA) - Wednesday, Feb 09, 2005 at 17:29

Wednesday, Feb 09, 2005 at 17:29
Well that's basically what I'm asking. 500ma might be enought to trickle charge the deep cycle to full capacity if it's almost their already, I really don't know the answer to that one. I mean obviously it will charge the battery EVENTUALLY but I want to know it 6w or 10w will charge it within the kind of 6-7 hours it's going to have daylight or weather it's just a wase of time.

Those trickle charger dash things look like a total wank to me, I dont reckon they'd charge my walkman. A 10w panel is still bleep weak in the grand scheme of things but at least it's kinda looking the part.
0
FollowupID: 356074

Follow Up By: Rosco - Bris. - Wednesday, Feb 09, 2005 at 17:54

Wednesday, Feb 09, 2005 at 17:54
That's why I'm watching with interest mate. Seems to be there won't be enough sunlight .... or the beer will go flat/hot waiting.

Cheers
0
FollowupID: 356075

Reply By: drivesafe - Wednesday, Feb 09, 2005 at 18:21

Wednesday, Feb 09, 2005 at 18:21
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=
AnswerID: 97508

Follow Up By: Member - Jeff M (WA) - Wednesday, Feb 09, 2005 at 18:50

Wednesday, Feb 09, 2005 at 18:50
No antoher battery would put even MORE strain on my alternator and charging system as well as the obvious problem of space. THERE IS NO MORE SPACE in the surf. :-)
I want to keep the deep cycle in tip top condition and keep it fully charged. A three stage charger is supposadly the best way to do this. So having a 3 stage solar setup permantally attached would be great for this. As well as removing the need to use external chargers before I go away etc etc. I don't really care that much about 5-10% however it would be nice to know the bat's chockas full before I head off.
0
FollowupID: 356083

Follow Up By: drivesafe - Wednesday, Feb 09, 2005 at 19:15

Wednesday, Feb 09, 2005 at 19:15
Jeff M, how do you use your vehicle. IE. do you drive it as the regular mode of transport or is it sitting around for a week or so at a time.
Just after an idea as to what sort of charge you will have when you hit the road.
Cheers
0
FollowupID: 356086

Reply By: drivesafe - Wednesday, Feb 09, 2005 at 19:01

Wednesday, Feb 09, 2005 at 19:01
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
AnswerID: 97518

Follow Up By: Member - Jeff M (WA) - Wednesday, Feb 09, 2005 at 19:12

Wednesday, Feb 09, 2005 at 19:12
Drivesafe thankyou, however I did provide these details in the origional post. Here they are in point form:

Battery: 85amp/h Wet Cell Deep Cycle
State of Charge: would be probally about 90% (charged from vehicle)
Time to Charge: 1 day or 5-7 hours Sun light.
0
FollowupID: 356085

Follow Up By: Member - Jeff M (WA) - Wednesday, Feb 09, 2005 at 19:21

Wednesday, Feb 09, 2005 at 19:21
Well at this point it is being driven every day but only for about 15-20 minutes. The deep cycle however is operating off a smart relay so does not take any load when the vehicle is started. All it is operating normally is the interior lights and the car stereo. All the other accessories are normally switched off around town.
0
FollowupID: 356089

Reply By: drivesafe - Wednesday, Feb 09, 2005 at 20:23

Wednesday, Feb 09, 2005 at 20:23
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.
AnswerID: 97532

Follow Up By: drivesafe - Wednesday, Feb 09, 2005 at 21:04

Wednesday, Feb 09, 2005 at 21:04
I’m surprised, dave actually had some helpful info.
I forgot to mention, with caravans, boats and the likes, fitted with a solar panels usually have to fit a switch to isolate the solar panel while the motor is running.
A cheap, quick and simple way to avoid the switch and automate isolating the solar panel is to fit a small SPDT relay that is powered by the ignition circuit of your vehicle.
Because of the small amount of current it will be handling, you don’t need an automotive type relay, just a small relay from Dick Smiths or Jaycar and should only cost a couple of dollars.
Cheers.
0
FollowupID: 356105

Reply By: Mainey... - Wednesday, Feb 09, 2005 at 21:05

Wednesday, Feb 09, 2005 at 21:05
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.
AnswerID: 97547

Follow Up By: Member - Jeff M (WA) - Wednesday, Feb 09, 2005 at 21:30

Wednesday, Feb 09, 2005 at 21:30
$290 seems a bit rich, I was looking at some (TRADE) for about $90 inc GST. But yeah I'm keen. See how it goes.
0
FollowupID: 356108

Reply By: michael42 - Wednesday, Feb 09, 2005 at 21:24

Wednesday, Feb 09, 2005 at 21:24
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
AnswerID: 97548

Follow Up By: Member - Jeff M (WA) - Wednesday, Feb 09, 2005 at 21:31

Wednesday, Feb 09, 2005 at 21:31
Yeah I looked at those ones I think that the way I'm going to go, I can get that particular one a little cheaper trade so might give it a go.
0
FollowupID: 356109

Follow Up By: drivesafe - Thursday, Feb 10, 2005 at 10:54

Thursday, Feb 10, 2005 at 10:54
Amazing, on another site Jimbo posted some info relating to the use of a solar panel for use in short term camping situations.
While I didn’t agree with his reasons for using a set up like his in this situation, no one got into an argument or started to sling off at anyone else and Jimbo’s post also related a very informative experiment that he had carried out and this in turn start a lot of people doing their own tests and then relating their experiences to others on the site.
Mainey has also made similar postings. Yet neither Mainey or Jimbo are out to make one single cent from their posting, they are just content to try and be of assistance to other net users.
And then there’s dave, Well what could anybody say in daves favour, not much and he’s try to win customers over. OR could this be why you are sticking it up Jimbo, because he was smart enough to buy his gear elsewhere?
0
FollowupID: 356190

Reply By: Markymark - Wednesday, Feb 09, 2005 at 22:14

Wednesday, Feb 09, 2005 at 22:14
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.
AnswerID: 97568

Follow Up By: Member - Jeff M (WA) - Thursday, Feb 10, 2005 at 12:38

Thursday, Feb 10, 2005 at 12:38
You know that was one of my other ideas (depending on how the replies to this post went).
The alternator in the Surf is a 70amp unit but I'm sure with all the mud and water in ingested and the fact that's 7 years old it's probally not really handling that kind of load anymore. The solar idea was good in that even when the car is not being used much the the deep cycle would still be at full charge and even though it would make bugger all difference it would also be helping a TINY bit in the fight with the battery and fridge while camping.
But even when the alternator is not under load the regulator on it is obviously set to about 14v which is still not really enough, so I would need to get that adjusted/replaced and I'm not sure how to go about that...
0
FollowupID: 356200

Follow Up By: Mainey... - Sunday, Feb 13, 2005 at 19:19

Sunday, Feb 13, 2005 at 19:19
jeff,
You could replace your regulator, as I have, and you will see the difference. I believe it may be a sealed unit under the dash on the bulkhead in some Surf's.
Put is a higher rated non heat sensitive version from an Auto electric shop....
0
FollowupID: 356671

Reply By: drivesafe - Wednesday, Feb 09, 2005 at 22:30

Wednesday, Feb 09, 2005 at 22:30
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.
AnswerID: 97572

Reply By: Member - Spook (SA) - Thursday, Feb 10, 2005 at 09:40

Thursday, Feb 10, 2005 at 09:40
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) :)
AnswerID: 97621

Follow Up By: Member - Jeff M (WA) - Thursday, Feb 10, 2005 at 12:11

Thursday, Feb 10, 2005 at 12:11
Spook you WON'T regret it, WA is an awsome place to live!
Mate as long as you don't mind the od drink or two I think you'll fit it no problems with the WA crew! ;-)

We'll have to take the yota's out for a spin and show you some sights hey!

The battery after being charged on the 240v charger will give me 12.7v at rest. It'll also charge at about 14 - 14.1v. After a month or so the charge will drop down to about 13.8v even lower if it's usage is a little heavier.
0
FollowupID: 356197

Follow Up By: Member - Spook (SA) - Thursday, Feb 10, 2005 at 14:23

Thursday, Feb 10, 2005 at 14:23
Thanks for that...
My aux battery (Exide Extreme N50) charges at about 13.9v when I'm not running anything, as soon as I flick on all my spotties it drops back to about 13.5v or 13.6v, I think I might start giving it a boost with the charger before I head out.

It would be great to see some of the sights as I know nothing about 4wd spots around perth.

Cheers
Brad
0
FollowupID: 356215

Follow Up By: Member - Jeff M (WA) - Thursday, Feb 10, 2005 at 14:32

Thursday, Feb 10, 2005 at 14:32
Yeah the spotties hurt my charging capabilities, especially if I'm running the Waeco at the same time, ouch!
Drop us a line when your over here and settled in! We'll have a drink!
0
FollowupID: 356216

Reply By: drivesafe - Thursday, Feb 10, 2005 at 14:04

Thursday, Feb 10, 2005 at 14:04
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
AnswerID: 97643

Follow Up By: Member - Jeff M (WA) - Thursday, Feb 10, 2005 at 14:34

Thursday, Feb 10, 2005 at 14:34
drivesafe, that and extremly valid point! Hmmm, the redarc voltage sensing relay would probally have solved that, then the deep cycle would not cut in unless it needed somthing from the alternator. I might still try it as the starter is a 17 plate jobby and doesn't seem to take too long to "recover" from the start, I spose it'll make sure the both batteries are topped up. Might need the bigger pannel. I had a look around I can get those good "blue" coloured 10 year warrant 12w pannels for about $140 locally. Might go that way...
0
FollowupID: 356218

Follow Up By: drivesafe - Thursday, Feb 10, 2005 at 14:38

Thursday, Feb 10, 2005 at 14:38
Jeff M, Keep us all informed, be interesting to see how you go and what the results are.
Cheers
0
FollowupID: 356219

Follow Up By: Member - Jeff M (WA) - Thursday, Feb 10, 2005 at 14:49

Thursday, Feb 10, 2005 at 14:49
No worries, you know me, I'll go to the "nth" degree with my experiments! LOL My missus just shakes her head when I'm continually out the garage with my stopwatch and thermotres, pressure guages, volt metres, etc etc.
Oh well, you gotta have somthing to keep your mind occupied!
0
FollowupID: 356220

Sponsored Links

Popular Products (14)