Using solar controller with charger / genny?

Submitted: Friday, Jan 06, 2006 at 19:24
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Hi all,

I am wondering about the possibility of using a Jaycar 20A solar regulator as a general purpose battery controller - any thoughts?

The controller is the MP-3129, $170:
http://www.jaycar.com.au/productView.asp?ID=MP3129

It strikes me that it probably wouldn't know the difference between solar panels and a charger or DC genny, and that it would probably work just as well regardless of the actual input energy source.

Among its features are 3-stage charging with adjustable voltages, equalization mode, pulse-width modulation, programmable low-volt disconnection and 2-day history display.

Am I mad or is this a fantastic idea?!
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Reply By: wortgames - Friday, Jan 06, 2006 at 19:27

Friday, Jan 06, 2006 at 19:27
I should probably add the intention is to mount it 'on board' a pair of deep-cycle batteries for use as a portable power rig, to be charged from a cheap charger at home and a cheap genny or possibly a solar panel when camping.
AnswerID: 146855

Reply By: Flash - Friday, Jan 06, 2006 at 19:56

Friday, Jan 06, 2006 at 19:56
Not a mad idea, and not a new idea.
I did it with a plasmatronics some years ago for a while, however there was a suggestion that it would destroy my expensive plasmatronics regulator (from the manufacturers) so I gave up on it.
However as I said I did do it for a while, hooked up to a 240v charger for a few weeks.........
AnswerID: 146860

Follow Up By: arofs1 - Friday, Jan 06, 2006 at 20:03

Friday, Jan 06, 2006 at 20:03
I have a Morningstar Prostar 15M and the manual says " Do NOT do it". I had identical thoughts as you until I read the manual.

Brian DJ
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Reply By: wortgames - Friday, Jan 06, 2006 at 21:05

Friday, Jan 06, 2006 at 21:05
Thanks folks. Any idea of the reasons for concern?

I imagine that the pulse-width modulation should pretty much take care of all circumstances but I'm happy to be enlightened.
AnswerID: 146877

Reply By: Member - Geoff M (Newcastle) - Friday, Jan 06, 2006 at 21:05

Friday, Jan 06, 2006 at 21:05
Hello wortgames,
My only concern on this idea would be current regulation.
The regulator you're talking about will pass 20 Amps, its rated load. No problems there.
Solar panels are unlikely to be large enough to exceed that figure of 20 Amps.
My concern would be protection of the regulator if the source, say a car alternator was capable of outputing more than the rated 20Amps. (They all are in the modern world)
Does the Jaycar regulator self regulate the current if the battery will accept more than 20Amps and the source is capable of delivering it?
Or does the regulator let the smoke out at a value greater than 20 Amps?

That'd be what I'd want to know and the Jaycar website didn't discuss that idea.

Geoff.
Geoff,
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AnswerID: 146878

Reply By: MartyB - Friday, Jan 06, 2006 at 21:12

Friday, Jan 06, 2006 at 21:12
Do it.
Specs are
*Battery Voltage: 12V
*Maximum PV panel open circuit voltage: 26V
*Continuous load/charge current: 20A
*Maximum charge/load current (5 mins): 25A
*Operation current (no load and PV): 30mA
*Dimensions: 150(W) x 85(D) x 45(H)mm
*Weight: 470g
*Operating temperature: -10 to +50oC

As long as you keep within these specs it will be fine. So obviously don't try to charge from a car alternator, but it would be fine for a genny. Might be the solution for those 2 stroke gennys that 12v output is all over the place.

By the way, if you have an ABN you can get an account with Electus (Jaycar's wholesaler). Price there is Qty 1+ $108.75 Qty 3+ $100.25 Qty 4+ $91.75
plus GST plus postage.

from Marty.
AnswerID: 146881

Follow Up By: Mike DiD - Friday, Jan 06, 2006 at 23:32

Friday, Jan 06, 2006 at 23:32
The "12 volt" output from small cheap and expensive generators is not DC - it's rectified and unfiltered AC, i.e. pulsating DC.

This may totally confuse any regulator and case overcharging or no charging.

Mike
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FollowupID: 400381

Reply By: wortgames - Friday, Jan 06, 2006 at 21:34

Friday, Jan 06, 2006 at 21:34
Good point re: input amps, might be an idea to put a fuse on the input (I want to make the whole thing idiotproof and fuses aren't exactly expensive).

In reality it's unlikely to ever see that sort of current, I have one of those GMC gennies and a friend has some solar panels, both of which might get used to put a bit back in to the batteries during a longer stay. I suppose they could also get a run in the car once in a while. Their main use will probably be home charged / camp used though.

My main concerns are the permanent charging at home, and the danger of excessive discharge when everyone's forgotten about what's making the sound and lights work :o)
AnswerID: 146887

Follow Up By: Member - Geoff M (Newcastle) - Friday, Jan 06, 2006 at 22:42

Friday, Jan 06, 2006 at 22:42
Re the fuses, at work today we discussed some electronic fuses.

I've not used or seen them. One of the guys I work with swears by them.

Apparently they'll trip at the overcurent level and hold out until you cycle the power. That'll reset them and they're good to go again.

Cost? Apparently about $0.50 each.

Geoff.
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Reply By: Eric Experience. - Friday, Jan 06, 2006 at 22:30

Friday, Jan 06, 2006 at 22:30
Wortgames.
There are 2 basic types of solar regulators, series and parallel, both have good and bad properties. the series reg has a .7volt minimum drop and has to draw current all the time, so you lose a bit both ways. the parallel reg has no voltage drop but efectively shorts out the solar panel so causing panel heating at the very time you dont want it so if you use a series on a genny that is ok but if you use a parallel reg on a genny you will load up the motor and burn a lot of fuel. I dont know which the jaycar unit is but given the low cost of electronic regulators as used in apliances I would fit your charging system with the one of the electronic jobs, they cost about $2 plus a heat sink. Eric.
AnswerID: 146898

Follow Up By: wortgames - Friday, Jan 06, 2006 at 23:00

Friday, Jan 06, 2006 at 23:00
Thanks for the tip re: series and parallel controllers, I assume it is a series controller but I will check before I buy.

What is it that you recommend regulating? The input to the controller? I can't see it ever getting more than 26V?!

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Follow Up By: Eric Experience. - Friday, Jan 06, 2006 at 23:11

Friday, Jan 06, 2006 at 23:11
Wortgames.
What I am recomending is to not buy the controller at all, but to use the electronic regs. as they are cheaper and better, at$2 each you could carry a spare. Eric.
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FollowupID: 400374

Follow Up By: wortgames - Friday, Jan 06, 2006 at 23:22

Friday, Jan 06, 2006 at 23:22
Eric, I don't see how a $2 regulator will do anywhere near what the solar controller will do. Firstly, the solar controller is a fully automatic 3-stage charger with periodic equalization. Secondly it will isolate the load when the voltage drops below a preset level.

The point of this exercise is to be able to fully charge the batteries, keep them in top condition during indefinite storage, and charge them effectively opportunistically - while protecting them from over-discharge when in use.

I don't understand your point.
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Follow Up By: Mainey (WA) - Saturday, Jan 07, 2006 at 00:45

Saturday, Jan 07, 2006 at 00:45
Wortgames, you say; "The point of this exercise is to be able to fully charge the batteries, keep them in top condition during indefinite storage, and charge them effectively opportunistically - while protecting them from over-discharge when in use. "

Why not use a $60 Projecta Automatic battery charger.

I understand a solar regulator should not be used with a generator, Steca Solar regulators definately specify they CAN'T be used with a generator, but it's your money and now you know the risks associated with using a solar regulator with a generator, if not then ask one of the tech's at jaycar for their opinion.

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FollowupID: 400396

Reply By: wortgames - Saturday, Jan 07, 2006 at 00:31

Saturday, Jan 07, 2006 at 00:31
OK, after a bit more research and archive surfing, fuelled by the responses above (thanks everyone), this is what I have come up with. Please feel free to comment.

Aside from the possibility of getting hold of a parallel regulator (not suitable), there are two possible issues which need to be addressed if intending to use a solar (series) regulator with non-solar sources. These are current and voltage.

The current issue is that a totally flat battery could pull more current than the controller is designed to handle, causing smokiness. The simple answer to this is to use one of the following: 1. a source which is not capable of supplying that much current. 2: a fuse or tripswitch. 3: groovy current-limiting circuitry.

The voltage issue is that many sources will not provide a high enough voltage to get a full charge into the battery. The best the controller can do is pass the voltage straight through (minus its own volt drop), and you still need to end up with about 15v to fully charge a battery. The solution here is to make sure you can provide high enough volts for the controller to do it's work.

Some automatic battery chargers will automatically switch to trickle mode (+/-13v)when the volts reach about 15v, which means they will 'fight' with the controller. The solution to this, presumably, is to use a powerful and cheap (non-automatic) charger or power supply which will allow it's voltage to get up into the high teens at low load - just like a solar panel.

My own charger has (I think) an unregulated 12A output as well as a high current 'start' feature. I am hoping that one of these will be suitable, otherwise I will build a hefty unregulated +/-18V DC power supply for full charging and conditioning at home. The GMC genny gives me about 18.5v unladen which is perfect.

There is another potential concern, in that the power from solar panels is nice and smooth, and the power from cheap gennies and chargers isn't, but my feeling is that the pulse-width modulation should be smart enough to look after itself in the face of a bit of wobbly DC.

So have I nailed it or is there anything else to be aware of?
AnswerID: 146921

Reply By: Mainey (WA) - Saturday, Jan 07, 2006 at 00:59

Saturday, Jan 07, 2006 at 00:59
I've looked at the photo and I believe it states on the front & centre of the unit

"only for 12v PV system"

in simple English, that means it's designed ONLY for a Solar Panel
you look at one and see if I'm wrong.
AnswerID: 146924

Reply By: wortgames - Saturday, Jan 07, 2006 at 01:12

Saturday, Jan 07, 2006 at 01:12
God forbid that anyone should ever use something outside of it's intended purpose!

The question, Mainey, is WHY is it only suitable for solar panels?

Is it because the world will end in a puff of black smoke?

Or is it because it is easier for the manufacturer to say that than to have to explain the physics behind using their product in other ways?

Come on, there's more to life than following everyone else's instructions.
AnswerID: 146926

Follow Up By: Wok - Saturday, Jan 07, 2006 at 08:12

Saturday, Jan 07, 2006 at 08:12
Wortgames,

If a manufacturer had the opportunity to increase their market base, don't you think they would have done it?

I am more inclined to think its PV only. There is a similar argument on using switch-mode power supplies with inverters.

eng
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Follow Up By: MartyB - Saturday, Jan 07, 2006 at 08:23

Saturday, Jan 07, 2006 at 08:23
Don't worry about building the unregulated power supply for charging at home. What I do is just sit the solar panel on the roof of my shed & plug it into the solar reg.
I can't see the varying DC of a cheap gen set worrying the reg as it is monitoring the battery voltage not the input voltage.
Another thing I did is mount a 3 way switch in line for the DC distribution in the trailer. Centre position is off, so I know all outputs in the trailer are disconnected when stored at home. Normal position is DC distribution via the Solar Reg to make use of the low voltage cutout feature of the reg. Third position connects the DC dist direct to the battery (via a fuse). I did this so that if the low voltage disconnect trips at 9pm I can get the lights back on instead of sitting in a blackout. ie turn the fridge off, flick the switch so the lights work for long enough to get the missus & kids to bed, then turn the lights off & go to bed.
I charge my batteries in my trailer 3 ways.
Anderson pole on front to charge via alternator (40a resettable cct bkr in circuit).
Solar via the solar reg.
Also have mounted a small arlec battery charger because I sometimes stay at caravan park powered sites. 240v inlet to RCD, RCD to a double power point plus a switch for battery charger. This way I use my 12v lights at powered sites & float the battery. Saves having 2 sets of lights. If I was to use a 2 stroke gen to charge the batteries I could either plug the DC into the solar reg or the AC into the 240v inlet.
Beware though of the 240v output of these cheap gen sets. A friend blew up the 240v side of his Engel with one of these. Luckily it only took out a capacitor & a diode so easy enough to fix.
from Marty.
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FollowupID: 400413

Reply By: wortgames - Saturday, Jan 07, 2006 at 09:34

Saturday, Jan 07, 2006 at 09:34
Folks, thanks for your suggestions, but please don't just tell me what is written on the packet. If the thing is PV only, I want to know why, what the difference is, and what I would need to change/add/remove in order to make it compatible.

Regarding the 'market base' agrument, that is rubbish and I hope most of us know it. 99% of these controllers will be used for solar systems, whcih is why they are sold as such, why it says so on the box and why the guys at Jaycar will tell me that. For the reasons I've pointed out above, if they said these things were compatible with generators they would have no end of dipsticks returning smoked units and wanting refunds after connecting them to over-current under-voltage sources.

No manufacturer in their right mind will accept that risk to 'increase their market base' by the 1% of customers who want to do something different with it. Far better to sell them another more expensive unit that is dipstick-proof.

A good-quality, high-current 3-stage electronic charger costs upwards of $400. A low-volt load cutout is another $20 for a crappy one or probably $100 for a good one. Then, if I do get some panels in the future, I will also need a solar controller.

If I can get this Jaycar unit for around the $100 mark, connect it to equipment that I already have, and cover all of those bases for a fraction of the cost then I'm happy to put a bit of effort into making it work. Box instructions don't help.
AnswerID: 146952

Follow Up By: Mike DiD - Saturday, Jan 07, 2006 at 13:42

Saturday, Jan 07, 2006 at 13:42
You can get a 240volt-in switchmode 3-stage charger for $99.
http://www.jaycar.com.au/productView.asp?ID=MB3612

It will charge up to 12 amps, so it limits the initial current (Stage 1) to 1/4C for batteries larger than 50amphour. It is only advertised as a 2-stage charger because the Stage 1 current-limiting is not variable over a large range.

Mike
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FollowupID: 400438

Follow Up By: hl - Saturday, Jan 07, 2006 at 14:09

Saturday, Jan 07, 2006 at 14:09
Just connect a fair size capacity across the input. The DC from the gennie is not filtered. A couple of 4700MFD/25V should do the trick.

Cheers
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FollowupID: 400443

Reply By: Mike DiD - Saturday, Jan 07, 2006 at 13:38

Saturday, Jan 07, 2006 at 13:38
I don't think you will have much luck connecting any regulator to the 12volt charging output of small Generators - the output is not DC.

"a peak voltage of about 22V with 100Hz return to zero ripple."
http://forums.overlander.com.au/viewtopic.php?p=549272#549272

My 1kVA Kipor with Inverter output for 240v describes the 12volt charging output the same way.

As a minimum, you will need to add LARGE capacitors if you want to connect any electronics to run off the output.

Mike
AnswerID: 146977

Reply By: wortgames - Saturday, Jan 07, 2006 at 15:07

Saturday, Jan 07, 2006 at 15:07
The controller draws its own power from the battery, and pulses energy from the source to the battery depending on battery voltage. A 100Hz ripple on the source really shouldn't make any difference, unless the controller also monitors source voltage in order to calculate its pulse width (which is possible). In this case a bit of capacitance would help to smooth the ripple to a managable level.

I'm not an electronics wiz but hl's suggestion looks fair to me.
AnswerID: 146998

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