solar dillemma

Submitted: Thursday, Jun 13, 2013 at 21:04
ThreadID: 102755 Views:1917 Replies:3 FollowUps:8
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hoping somebody can help with this. Recently purchased a boat and soon realised the batteries were on there way out, it had been hooked up to shore power but only using 2 stage charger so the probably never charged fully as well as the solar regulator was only 2 stage. the panels were pretty old so the first thing was the purchase of a new panel, 200w. Here is where the drama begins..I was informed today from the guy that sold it to us that it is a 24v. ( very annoyed with him ). so we have three gel batteries, I think they are 100ah each, ok so my regulator is a steca 15 amp 12/24v pwm, it seems to be working and every thing but this shouldnt be the case should it because the batteries are in parallel. what sort of damage is this doing??
we were going to get 2 new batteries any way, thinking of 2 x 150ah agm's, ok second problem. Recent purchase of a 40amp 12v xantrex true charge 2 battery charger, is this charger going to be suitable if we have to hook the new batteries in series?. thanks, any ones help would be appreciated because I am ready to tell this guy that we want our money back for the solar panel and I don't want to, he didn't tell us it was a 24v
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Reply By: Member - Frank P (NSW) - Thursday, Jun 13, 2013 at 23:15

Thursday, Jun 13, 2013 at 23:15
G'day Adell s,

There are quite a number of solar regulators that will allow a nominal 24V panel to charge a 12V system. Your Steca could be one of them. Get the model number, go to the instructions, the Steca site or google, check the specs and see if that's the case. Or post the model number here and someone may be able to help. The fact that everything seems to be working suggests you may be ok, but it would pay to check.

When you replace batteries that are connected as a pack, you should replace all of them, so you should get three new ones if you're going to stay with a three-pack. Two would be ok if you're going for a two-pack. Reason being that an old weaker one amongst new ones will pull the new good ones down to its level. There's more to it than that, but that will do for now. On re-reading your post, it looks like you're going to replace 3 x 100Ah with 2 x 150Ah, so no problem.

If you have 3 batteries and you hook them in series you'll have 36 volts. If you go for two batteries and hook them in series you'll have 24V. Nothing in your 12V system will work and you'll bust something, blow lights and fuses, burn motors, ruin electronics, etc. Might burn your boat. Your boat has been set up as 12V, so you have to stay with that unless you add a voltage reducer. Why bother? Two, three, four or ten batteries in parallel will still give you the 12V that your system is designed for, so stay with parallel.

The Xantrex is a fine charger, one of the best, but being 12V will only handle 12V a battery pack, so again, you have to remain with a parallelled, 12V battery set-up.

If you can confirm that your Steca regulator can accept 24V panels to charge a 12V system and if you keep your new batteries in parallel so your system remains at 12V, you should be ok with your 24V panel.

Also, considering the system is old, make sure the cabling is big enough to do the job and that all terminals and connections are clean, bright and in excellent order.

Cheers







FrankP

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Reply By: adell s - Friday, Jun 14, 2013 at 09:30

Friday, Jun 14, 2013 at 09:30
thanks Frank, yes the regulator is a pr 1515 which is suited to 12/24v it is pwm, I am reading about other regulators that are mmpt that suit the system better, but I believe mine is fine. What I can't comprehend is that everything seems to be working fine with the three batteries are in parallel. I'm thinking that one of the batteries is completely stuffed and is somehow handleing the system because there is quite a significant voltage drop overnight with no power being used. As I explained the old owner was using a two stage charger so the batteries only ever got to 80% s.o.c. and even if he had his panels connected during the day his regulator was only 2 stage as well. Either it is a massive fluke if this is the case or the panel is 12v and this bloke is a goose, one last thing is, my new xantrex battery charger has the ability to charge three batteries, does this mean they can be charged independently while hooked up either in series or parallel? cheers.
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Follow Up By: Member - Frank P (NSW) - Friday, Jun 14, 2013 at 12:09

Friday, Jun 14, 2013 at 12:09
G'day again, adell s

I've looked at the data sheet and operating instructions for your solar reg. It's old, but in my opinion it is good and well engineered for what it is, an earlier, superseded solar controller.

From what you say, I agree with the possibility that one of the three batteries is stuffed and is pulling the system down overnight. It is possible that they are all below par to varying degrees, with the same result. The best way to test them is to remove them, take them to a battery place and have them individually load-tested.

It is possible for the batteries to have little capacity (ie, be worn out through age or abuse) but still appear to be taking a charge normally when hooked to a charger (mains or solar). So it is quite possible that everything will look hunky-dory with the solar working, but as soon as you put a decent load on the batteries they go flat quickly, or rapidly self-discharge.

The Steca has a Gel setting and a Flooded setting. You have gel batteries. Is the Steca set to Gel? If not, that will have overcharged your Gel batteries and contributed to their poor performance. Also, the Steca will apply a periodic Equalisation charge if set to Flooded. That is a definite no-no for sealed batteries and if it happened would further contribute to their present state.

Also, Steca's data says that your gel batteries will be held at 13.9V by the solar charger. That is a float charge and is higher than a fully charged battery's resting voltage, so it is natural for the voltage to come down to 12.6 or so with no sun and no load. Even a good battery will do that. (I'm not sure of the resting voltage of a fully charged gel battery, but the principle is valid).

A good quality three stage PWM charger would theoretically be better than your 2-stage Steca, and a 3 stage MPPT better again, but I'm not sure it's worth the expense to change just yet until we know more of your requirements, such as useage, loads, how long you want solar to support your batteries without access to mains - eg long boat trips - etc. I suspect your Steca will be adequate in combination with good batteries and a good multi-stage mains charger. But if you have a big wallet, I would tend towards a new, up-to-date MPPT multi-stage solar regulator.

In the Xantrex, the reference to charging three batteries means it can look after three different battery sets, or banks. If you connect two or three batteries in parallel, the Xantrex will see them as one battery bank. You would connect that bank to one of the three outputs on the charger. You could connect an engine battery to another of the outputs, and a third, auxiliary battery or set of batteries, to the third pair of outputs. The Xantrex has the ability to look after all three sets of batteries as if it were three separate chargers. (You would have to check the instructions on that, as there may be restrictions, like maybe they all have to be the same type - gel, flooded, AGM, etc. I know the principle, not the details.)

So your batteries must be hooked up in parallel to keep the overall voltage to 12V and that set of parallel batteries connected to one of the outputs of the Xantrex. The Xantrex will then see them as one battery and charge them simultaneously.

DO NOT hook them up in series. Series will add the voltages of the batteries - 2 will give 24V, 3 will give 36, etc. It's a 12 volt charger, it cannot charge 24 or 36 volts battery banks and could be damaged if connected to higher than 12V.

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Follow Up By: Nomadic Navara - Friday, Jun 14, 2013 at 12:18

Friday, Jun 14, 2013 at 12:18
The Steca PR 15-15 is considered to be a 3 stage regulator. When the panels start to supply power to the regulator the regulator will handle what the panel will give it. If the current available for charging is more than 15 A the regulator will limit the charge current to 15 A. This is the first or bulk stage of charging.

Whilst the bulk charging is taking place the battery terminal voltage will rise, the more the battery is discharged the longer this rise time will be. When the set voltage of the regulator is reached the regulator will hold the charge voltage constant and the charge current will start to fall. When this takes place the regulator is considered to have entered the second or absorption stage. this will happen at 70 - 80% charge. During the absorption stage the current will continue fall as the charge level of the battery rises.

The absorption stage will continue until the charge current falls to a few percent of the maximum current of the regulator. The regulator will then switch to a lower charge voltage. At this point the charger enters the third or float charge stage The float voltage is selected so that battery will not accept a charge current that will wreck it over a long period of time and so you can leave the charger connected.

I suspect that your mains charger may work the same way. The solar chargers/regulators do not actually do any switching between the bulk and absorption stage. Their internal regulators work in conjunction with each other and the voltage regulation takes over from the current regulation seamlessly as the battery terminal voltage rises without any switching taking place. There is two stages of charging action considered to take place even though the logic circuitry does no switching. When you first switch a charger on and the batteries are nearly fully charged you may not see the charger go through the bulk stage but it will have done so.

Your solar regulator may be a 12/24 V model but what you have to realise is that when you connect it to the battery it will set itself up to the voltage of the battery and will become either a 12 or a 24 V regulator depending on what you hook it to. You seem to be getting away with operating a higher voltage panel through it than it was designed to operate from when acting as a 12 V regulator. Your biggest problem is that you are wasting half the potential power output of your panel. A 200 W, 12 V panel will supply around 12 A under ideal conditions. Your 24 V panel is only capable of supplying 6 A under the same conditions. You could more than double the potential output of your panel by by changing your regulator to an MPPT model.

If the installation was mine I would not rewire the batteries in series. To do this, everything that operates from the batteries would have to be changed for 24 V models. Alternately you could get a 24 to 12 V converter to power your system from the 24 V battery bank. There is no simple way of running 12 V appliances from 2 12 V batteries charged in series.

Quote "one last thing is, my new xantrex battery charger has the ability to charge three batteries, does this mean they can be charged independently while hooked up either in series or parallel?"

The 3 outputs of your new charge are designed to charge 3 separate battery banks. If you are going to connect several batteries to work in series or parallel combination then they should be charged in the same configuration. To do otherwise can easily end up in tears. I would suggest you keep your batteries in one 12 V bank, remember the KISS principle.

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Follow Up By: Nomadic Navara - Friday, Jun 14, 2013 at 12:23

Friday, Jun 14, 2013 at 12:23
Looks like Frank and I were typing together, We seem to be in concert.

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Follow Up By: adell s - Friday, Jun 14, 2013 at 16:21

Friday, Jun 14, 2013 at 16:21
thanks peeps, look I have bit the bullet and purchased 2x 150ah a.g.m batteries, for a good price too, offering 5 year warranty and up to 1600 cycles $319 each, and a 180w monocrystaline panel for $200 ,yes the steca was set to gel setting and yes it is quite a good 3 stage controller, 2yrs old. We are mainly moored at a marina and rarely go out for more than a few days so I think this set up will be fine now, as for the old batteries, I will have them tested but I think they will end up making good sinkers. I don't think it's necessary to invest in a mmpt regulator.
As for the guy that sold us the panel, looks like he is the proud new owner of it and I think I have the right to ask for my money back. cheers and thanks, Adell. ps what would really make me happy is if any one know a reputable auto electrician in the Tweed area.
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Follow Up By: Member - Frank P (NSW) - Friday, Jun 14, 2013 at 16:32

Friday, Jun 14, 2013 at 16:32
PeterD wrote:
"You seem to be getting away with operating a higher voltage panel through it than it was designed to operate from when acting as a 12 V regulator. Your biggest problem is that you are wasting half the potential power output of your panel. A 200 W, 12 V panel will supply around 12 A under ideal conditions. Your 24 V panel is only capable of supplying 6 A under the same conditions. You could more than double the potential output of your panel by by changing your regulator to an MPPT model."

G'day Peter, and thanks, I overlooked that. Is it always the case? There are a number of PWM controllers on the market that accept 24V panels to charge a 12V system. Do they all waste half the potential power, or is that something confined to earlier designs?

Anyway, I was thinking that his battery capacity (300Ah) is pretty large for just a 200 watt panel. Being on a boat, he maybe doesn't have room for more solar, so it would be in his interests to maximise the output from whatever solar system he has, so an upgrade to a suitable MPPT reg (relatively expensive, but a better all-round solution, IMO. Better output, and with 24V panels, lower current in panel-to-reg cables), or take the zero-cost option and take his panel back to swap it for a 200W, 12V version instead and stay with the Steca.

Also, I have to correct myself. I said the reg was an older, superseded model. I don't believe that is correct. I said it because the Steca website had links to archived instructions which suggested to me the reg was an early model. It was only early versions of the instructions that were archived, to be replaced with newer versions better translated from German!!

Cheers

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Follow Up By: adell s - Friday, Jun 14, 2013 at 19:19

Friday, Jun 14, 2013 at 19:19
hi guys, thanks for your input, I just thought it was a better option to bite the bullet and get a 12v panel, as I explained the gel batteries were fairly old and never charged correctly, I was lucky enough to get the xantrex truecharge 2. 40amp last week on ebay for $237, it was 2nd hand but only used a couple of times in a camper that the guy decided to go with a larger system.it is 12v I only found out yesterday of the guy that sold us the panel that it was 24 v, it has been hooked up now for a couple of mths and i'm guessing that the batteries were that bad that it has been able to handle this in parallel and thank god my regulator was 12/24. the reason i'm going with 300ah is because the old batteries I believe might be 300 ah, 3x100ah wasn't sure weather this was too much, but better to have too much than not enough, my plan B. for long stays without shore power and not much sun is a 3.4 kva sinewave generator, cheap chinese one but served us well travelling the country, it says sinewave (not pure sinewave) I am wondering if this is going to be compatable with the xantrex??, I think I have got this sorted and I believe in buying good stuff I shall see how it all pans out and keep you posted. P.S not a guy, cheers Adell a female
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Follow Up By: Member - Frank P (NSW) - Friday, Jun 14, 2013 at 21:53

Friday, Jun 14, 2013 at 21:53
Sorry for the inappropriate he, his and him, adell s.

You could check with Xantrex's Australian distributor/service agent about powering your charger with modified sine wave (as distinct from pure sine wave):

Enerdrive
Unit 11, 1029 Manly Road
Tingalpa, Brisbane 4173
Email: sales@enerdrive.com.au
Ph. 07-3390-6900

Cheers
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Reply By: tonysmc - Saturday, Jun 15, 2013 at 10:52

Saturday, Jun 15, 2013 at 10:52
I don’t know about the Xantrex, however I do know you can get 12 volt chargers that will charge 24 and 36 volt systems.
I just not sure why, if you have a 12 volt system now, you would want to change it to 24 or 36 volt as I would assume everything on the boat is 12 volt.
Are you adding something that only runs at the higher voltage?

cheers

Tony
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Follow Up By: adell s - Saturday, Jun 15, 2013 at 11:19

Saturday, Jun 15, 2013 at 11:19
hi Tony, my dilemma started when this goose sold me a 24v panel, we whacked it on believing it was 12v, 3 batteries in parallel, my regulator 12/24v, luckily handled the load because the batteries pretty old. Like I explained I acquired the dux guts 12v charger on ebay last week, It just was a cheaper option to buy another 12v panel in the end, I never wanted a 24v system.
we were going to get new batteries any way, I'm just very lucky this guy came clean and told us it was 24v panel before we hooked up new batteries an charger. cheers adell
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