Outback controller not fully charging my batteries? - SailNet Community
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post #1 of 16 Old 10-08-2016 Thread Starter
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Outback controller not fully charging my batteries?

I just replaced my cheap Chinese controller with an Outback Smart Harvest PWM 10a controller. The idea was to put something reliable there to keep my batteries charged. I have two 45w panels and a bank of brand new batteries, totalling 210a. There are no loads on the batteries when I'm off the boat except a muffin fan in the composting toilet. Now here's the problem: the battery light on the controller doesn't stop flashing, which indicates the batteries are between 50 and 90% SOC. I find it strange that the 90w of solar panels can't bring the batteries up to 100% SOC after weeks in the sun on my mooring. During the day the voltage rises on the batteries to 13.2v (indicating they are charging), but the light doesn't stop flashing. Are my batteries being charged properly? Anyone here have the same controller? Is it normal it doesn't indicate 100% SOC and stop flashing?

Vindö 50

Last edited by copacabana; 10-09-2016 at 08:11 AM.
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post #2 of 16 Old 10-09-2016 Thread Starter
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Re: Outback controller not fully charging my batteries?

I forgot to mention- the batteries are sealed, flooded batts and I can't check the specific gravity to get the real SOC.

Any other users of the OutBack Smart Harvest PWM controller out there?? I'd love to know if that light stops blinking!

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Re: Outback controller not fully charging my batteries?

I don't have that charger but what is the resting voltage of your batteries?
Unhook the batteries for a couple hours to get the resting voltages.
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Re: Outback controller not fully charging my batteries?

Mike, I'm not on the boat right now to test that. When I left the boat they were at 12.7v (measured at night with only a few LED lights on).

I asked about this over on the Outback forum (in the hopes someone from tech support would chime in) and received this answer:

I do not think you have enough panels for your batteries, Most recommend 5 to 15 % of 20hr capacity as a charge current (10.5 to 31.5 for yours) , you max at 7.5 amps & with your panel voltage so close to battery V, I would be surprised to see that often,
Can you get to shore power ? or get them to a decent charger ? I would charge them properly first & them have another try, But as mentioned, I think you are going to need more panel to even maintain them once they are charged (refer to manual, you should give them a good commissioning charge anyway)


It makes no sense to me though. I can't see why 90w of panels can't maintain a 210a/hr bank of batteries charged. My panels probably put out about 25a/hr a day, which is enough to replace my consumption and keep them charged, assuming the boat has no loads from Monday to Friday. At any rate the boat has been sitting there in the sun for a MONTH now and the damn light keeps blinking indicating a charge of 50 to 90% SOC.

I'm vexed, to put it mildly ...

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Re: Outback controller not fully charging my batteries?

While not enough to bring your batteries back from a deep discharge in a reasonable amount of time, I agree totally that 90w of panels should be more than adequate to top off your batteries. I suspect it's something to do with the setpoint(s) on the controller. Is there a setting for different battery types?

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post #6 of 16 Old 10-10-2016 Thread Starter
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Re: Outback controller not fully charging my batteries?

Thanks Jim. Yes, there is a dipswich setting for VRLA or flooded batts. For some reason I left it with the factory setting for VRLA. The difference in the charge profile is:

Bulk 14.8v (fl) 14.6v (VRLA)
Absorb 14.8v (fl) 14.4v (VRLA)
Float 13.2v (fl) 13.5 (VRLA)

Looking at those numbers now I wonder if the 13.5v float isn't a little high for my batts. Still, it wouldn't explain why the light is blinking- or would it?

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post #7 of 16 Old 10-12-2016 Thread Starter
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Re: Outback controller not fully charging my batteries?

If I was vexed before, I'm even more so now ...

I had this reply on the Outback forum. Basically he says I will never be able to charge a battery with 90w of solar (so why manufacture them if they can't charge a battery?). I find it hard to believe that, over a number of days, the 90w of solar can't replace to 25 a/hrs or so that I might use over the weekend.

He responds to my comment: "yes, 90w doesn't provide a whole lot of power. I would imagine about 5a for about 5 hours a day (I'm in the tropics- lot's of sun). That's still 25a/hr a day."

with this:
you can probably half that,,,, or less, You do not have enough amps to get to your bulk voltage and then do absorb stage, Float is something you will never see with what you have, And unless you leave boat for a reasonable time,maybe not with 300w,,, Please be careful trying to count "numbers" 5 amps out and 5 amps in can be very wrong, There are a lot of variables & you have to take into account losses, 5a out could need 10a back in and as above, trying to describe it in laymans terms, errrmm, like pushing a truck up a hill with a small car, you will get it so far but never over the brow (Bulk to absorb, not enough power)


Also, if anyone electrically inclined could comment on the question about the float charge in the preceeding post, I'd be grateful. I'm not sure the problem isn't related to the controller settings (the controller trying to float the batts at 13.5v and the batts not responding as expected and leading the controller to think they aren't at 100% SOC).

Vindö 50

Last edited by copacabana; 10-12-2016 at 07:27 AM.
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Re: Outback controller not fully charging my batteries?

sounds like you may have a controller problem - not a wattage or voltage shortage. 90 watts is more than sufficient to recharge your system in a reasonable period, and while larger would do the job quicker, 90 will still get the job done.

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Re: Outback controller not fully charging my batteries?

Two 45 Watt panels. OK, let's rashly assume they are working perfectly and really putting out 45 Watts each. And, that you've got them wired up with clean solid cables that aren't cutting out any of that power, so the MPPT controller is getting 90W.

In bright sunlight, maybe that's 90W at 17VDC, but the MPPT should be able to make that into 13-ish volts which would be 6.9A, if there were no losses, at 13 volts. So let's say, maybe 6A with losses and voltage differences?

And yes, solar panels should be able, over the course of a full summer day (12 hours long) to provide the equivalent of 5 hours at full rated power. So your panels and MPPT controller should be able to feed 30Ah into the batteries in a perfect day. An MPPT controller will have a 2-4% power loss for internal functions, and the batteries themselves will require 10-15% more power IN to replace whatever power was taken OUT. So, let's be pessimists and say you'll only get 80% of those 30 Ah, that's still a solid 24Ah that your system should be able to replace in one day.

And you've got a 210Ah bank, so you can put roughly 10% of the capacity (11.4 but who's counting) back in a given day of full sunlight. At that rate...I could see it taking a full week for you to recover from a weekend, but surely by then, the controller should recognize the batteries as being charged?!

Maybe there's something being missed from the picture. Some bit of equipment that's placing a load on the batteries, fooling the MPPT into thinking they aren't charged, or more easily, something is eating power?

It might almost pay to hook up two voltmeters, one at the panels, the other at the batteries, and note the voltage every 1/2 hour all day long, to see what the system is actually doing. And then, since sailing is the only priority in life (G) to come back on successive days and again, track what happens over several days, trying to pin down exactly what is going wrong, at what point in time.

The charging may not be optimal, but it sounds like something is missing from this picture.

Unless I missed it, you still haven't said how far you're cycling them, and if you're sure nothing is drawing power wile you are away. That's important.

On the flooded/vs/VRLA voltage settings? You need the specs for your exact battery, from the maker. Sometimes you just can't get the right numbers from some equipment, sometimes you need to set the switches "wrong" to come closest. And then there's temperature compensation. You're doing all the charging at 20C, right? Or oyu have a battery temperature sensor hooked up to compensate for that?
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Re: Outback controller not fully charging my batteries?

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Originally Posted by hellosailor View Post
Two 45 Watt panels. OK, let's rashly assume they are working perfectly and really putting out 45 Watts each. And, that you've got them wired up with clean solid cables that aren't cutting out any of that power, so the MPPT controller is getting 90W. It's a PWM controller and I checked the connections and they are clean and tight.

In bright sunlight, maybe that's 90W at 17VDC, but the MPPT should be able to make that into 13-ish volts which would be 6.9A, if there were no losses, at 13 volts. So let's say, maybe 6A with losses and voltage differences? OK. I was being even more conservative and saying 5a.

And yes, solar panels should be able, over the course of a full summer day (12 hours long) to provide the equivalent of 5 hours at full rated power. So your panels and MPPT controller should be able to feed 30Ah into the batteries in a perfect day. An MPPT controller will have a 2-4% power loss for internal functions, and the batteries themselves will require 10-15% more power IN to replace whatever power was taken OUT. So, let's be pessimists and say you'll only get 80% of those 30 Ah, that's still a solid 24Ah that your system should be able to replace in one day. OK. I'm happy with 24a/hr per day.

And you've got a 210Ah bank, so you can put roughly 10% of the capacity (11.4 but who's counting) back in a given day of full sunlight. At that rate...I could see it taking a full week for you to recover from a weekend, but surely by then, the controller should recognize the batteries as being charged?! Yes, but that damn light is still blinking ....

Maybe there's something being missed from the picture. Some bit of equipment that's placing a load on the batteries, fooling the MPPT into thinking they aren't charged, or more easily, something is eating power? I turn everything off at the breaker panel. There is a bilge pump that may turn on for a few seconds once a week. I have a muffin fan running 24/7 in the composting toilet (milliamps of power). I haven't checked for stray leaks in about a year, but last time there was no loss of power.

It might almost pay to hook up two voltmeters, one at the panels, the other at the batteries, and note the voltage every 1/2 hour all day long, to see what the system is actually doing. And then, since sailing is the only priority in life (G) to come back on successive days and again, track what happens over several days, trying to pin down exactly what is going wrong, at what point in time. This would be a great way to see what's going on, but I can't do it now. We just had a baby 2 weeks ago and buggering about on the boat is out of the question for a month or more!

The charging may not be optimal, but it sounds like something is missing from this picture. Yes, I agree. I've replaced the batteriesd and controller and tested the panels. Te only thing I haven't done is replace the wiring.

Unless I missed it, you still haven't said how far you're cycling them, and if you're sure nothing is drawing power wile you are away. That's important. I never go below 12.4v and rarely below 12.5v.

On the flooded/vs/VRLA voltage settings? You need the specs for your exact battery, from the maker. Sometimes you just can't get the right numbers from some equipment, sometimes you need to set the switches "wrong" to come closest. And then there's temperature compensation. You're doing all the charging at 20C, right? Or oyu have a battery temperature sensor hooked up to compensate for that?
The battery manufacturer (Bosch) suggests a float charge of 13.2v-13.6v. Both Outback charging profiles (flooded and VRLA) are within the charging specs of the batteries. No temp. compensation on this controller. Charging is at ambient temp (15-35 degrees celcius).

Hellosailor, once again I appreciate your comments. I am not entirely sure the batteries are not charged 100%. What is causing me concern is the blinking light that indicates 50-90% SOC. It hasn't gone off in a month of sitting on the mooring in the sun.

Vindö 50

Last edited by copacabana; 10-12-2016 at 08:53 PM.
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