Anotherpower.com Forum
Renewable Energy Questions/Discussion => Automation, Controls, Inverters, MPPT, etc => Topic started by: ChrisOlson on March 19, 2012, 09:50:54 pm
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Well, when I came in for supper the master inverter was flashing an error for "Gen Failed to Start". The reason is because it hasn't run for one month. The inverter tried to start it and the battery in it was dead. Generac recommends exercising the generator once every 7 days to keep the battery charged up because the electronics in the generator draw a small amount of power from the battery all the time.
Well, I don't want to exercise my generator once a week. I got the inverter programmed to exercise it every 30 days.
There was two wires in the control cable from the GSM to the generator that weren't being used. Those two wires would be for pre-heat on a diesel. So I hooked those to the gen battery. I didn't want to hook the other end to a battery in my battery bank because the bank gets down below 24 volts sometimes and this would discharge the gen battery and not be good for it.
So I re-installed the Morningstar RD-1 that I had just taken out when I installed my Classic 150 on the solar array and hooked it up to one of the batteries in the bank (12 volt). I programmed it to monitor the voltage of that battery and when it's above 13.0 volts the RD-1 turns on a little ice cube relay that connects the gen battery to the big battery in the bank to keep the gen battery charged.
I suppose I could do the same thing with a little diode - if I had one laying around - but I don't.
I haven't found an end to dreaming up what one of them RD-1's can be used for yet.
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Chris
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I suppose I could do the same thing with a little diode - if I had one laying around - but I don't.
I haven't found an end to dreaming up what one of them RD-1's can be used for yet.
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Chris
Chris;
I have a handful of diodes I will swap you for it!
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Was about to make the same offer Chris, but then I remembered that picture Tom posted. :o
So respectfully not making the offer. ;D
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Well, I want to try this for a few days and see if it works OK. I got to thinking this morning that sometimes my bank, with the low-specific gravity Surrette's, goes up to 30.8 volts during absorb if the batteries are nice and cool. That's not good for the genset battery either because it would take it up over 15 volts.
So I reprogrammed the RD-1 for a high and low limit of 14.4 and 12.8 so the genset battery is only connected to the bank battery if the voltage is within those limits. The battery in that genset is just a little Yuasu unit about the size of a motorcycle battery. Maybe 10 amp-hours or so. I don't want to cook the little thing.
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Chris
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The battery in that genset is just a little Yuasu unit about the size of a motorcycle battery. Maybe 10 amp-hours or so. I don't want to cook the little thing.
VW solar panel?
The self regulated type are, well, self regulated.
The other type can be regulated for $5.
Or, more economically done, it could be maintained from the house battery bank.
Depending on the situation, $2(?), but it would not require a separate solar panel be purchased and installed.
G-
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Or, more economically done, it could be maintained from the house battery bank.
That's pretty much what I'm doing with the RD-1. I checked it today and the system spent a lot of time in bulk charging because of no sun and only light winds about 12-14 mph. It held the little battery in the generator at too high of voltage too long for it, and it was gassing pretty good at 14+ volts after several hours.
So now I programmed a one hour timer in the RD-1 so it only charges the little battery for one hour a day off the RE system to keep it maintained, and I lowered the high voltage level to 13.5 volts. So it starts charging when the house bank gets to 25.6 volts, stops charging when the house bank goes over 27.0 volts, and only charges for a max of one hour.
The poor little thing would've been boiled dry in about two weeks the way I had it set.
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Chris
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That sounds like a pretty complicated way to keep a generator battery charged. I put a 5 watt amorphous panel on a teeny 3.2 Ahr SLA battery that powers the solar tracker for my well pump. The amorphous panel tracks with the main array and we get over 260 sunny days a year here. It's been out there a long time, I'm sure over a year without me fooling with it. I have no charge controller on it and I thought I'd boil the battery dry in three months but it keeps on going.
Maybe I'm just lucky that the power to run the linear actuator approximates the power of the solar panel every day. Maybe a 5W panel would boil a generator battery dry with no daily loads for a month. Still it seems so much easier to use a small solar panel for this type of task than fiddling with settings on a logic module.
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Chris;
Speaking of VW Solar Panels..
I might work a swap for a VW solar panel I have for that RD and some coin? Was needed for the Bug when it sat winters unused. We got rid of that albatross when we got the Fiesta. A convertible was nice occasionally but 38+ MPG is nice every day!
Anyway I have one that is not being used.
Tom
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Well, being that I got it wired into the GSM I'd like to try it for a month and see how it works.
[attachimg=1]
I wired up two channels on the RD-1 because I think I might be able to use it in the winter too. I got the second channel programmed as an input channel and it's wired to RY11 in the Generator Start Module. If the gen fails to start after three tries in really cold weather, it's got three tries left before the inverter locks the gen out with a Fail To Start error. I can have the inverter activate RY11 (which is an alarm channel) after try #3. When the RD-1 senses the alarm input on channel 2 it will activate the relay, hooking the genset battery to the big bank for extra "boost" for cold weather starting.
LOL! Like I said, I really haven't come to an end of dreaming up what one of these RD-1's can be used for. But now that I got it back in use I'd like to try all this stuff.
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Chris
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Well, as it turns out this didn't work all that great in the end. The RD-1 basically draws a few milliamps of idle power and that's negligible. But what happens is that when it engages the relay the 1/4 amp draw from the relay coil, plus the draw from the genset battery, causes the voltage to run low by up to a 1/2 volt on the battery that it's hooked to on the bank. This causes the other battery that's in series to run high on voltage by up to a half volt and it gets the living snot boiled out of it while the "maintainer battery" doesn't.
A little solar panel that puts out a couple watts or so, just to cover the draw from the electronics in the gen, will work better. It's what I should have done in the first place. But I didn't have one. TomW had one, and he needs an RD-1. So we got a "deal" worked out that will work better for both of us :)
This was a nice experiment. But it's really hard to put any sort of a load on part of a series battery bank and keep the bank perfectly balanced. Keeping those batteries perfectly balanced is pretty much key to long life and proper charging. So in the end I had to scrap this idea and go to "plan B".
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Chris
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For Plan A, the little battery's charging current should have been pulled from the house banks series strings, and not a single battery in the string.
G-
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For Plan A, the little battery's charging current should have been pulled from the house banks series strings, and not a single battery in the string.
Well, the problem is that I got Rolls-Surrette T12-250's and those are six cell 12 volt batteries. My system is 24 volt and the genset battery is 12 volt. There's no place I could hook to in the bank that would not cause an imbalance.
I could have had the RD-1 turn on a little 120 volt battery maintainer that runs off the inverters for a couple hours a day. That would work fine. But at that point it was like, well ....... one of them little 3 or 4 watt solar panels makes more sense :)
In the winter I don't need the genset battery maintainer. But in the summer we get lots of solar and our loads are lower so the genset turns into yard art and it's not used. Things in the winter that take a lot of power, such as my wife's electric clothes dryer that will cause the gen to start in Peak Power Management Mode, don't even get used because the clothesline works in the summer without freezing the clothes into solid ice.
I put my digital ammeter on the genset to see what it draws. The idle power consumption of the electronics in it is 40 milliamps, which is about 1 amp-hour a day. In two weeks, if it doesn't run to recharge the battery, the battery is low enough that it won't start. That little VW solar panel, if it can replace 1 amp-hour per day, on average, will work perfect.
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Chris
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For Plan A, the little battery's charging current should have been pulled from the house banks series strings, and not a single battery in the string.
Well, the problem is that I got Rolls-Surrette T12-250's and those are six cell 12 volt batteries. My system is 24 volt and the genset battery is 12 volt. There's no place I could hook to in the bank that would not cause an imbalance.
That little VW solar panel, if it can replace 1 amp-hour per day, on average, will work perfect.
I understood what you thought the main problem was.
Solution, quickie style?
[attachimg=1]
The VW PV will work great, has no conversion losses, and it will not have a gazzillion feet of wire to run.
And if I am not mistaken, that particular VW PV has a built in controller.
G-
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Oh, OK. I don't have the electronics knowledge to make something like. Or I could make it now that I've seen it, but I don't know how to go about designing something like that.
The little solar panel came from Tom today in the Universal Package Smasher truck. I wired in a cig socket to the genset battery and mounted the little solar panel on the top of the gen housing. I ran the cord thru the access panel and plugged it in (it has a cigarette lighter plug on the panel).
The battery was at 12.44 volts when I plugged it in. It took about 30 minutes and it had already come up to 12.92 but it wouldn't go over that. I checked the open voltage of the little panel and, cripes, it was 18 volts.
After the sun went down a few hours ago, now the battery is at 12.52 volts. So it didn't put a lot of juice into it and it's not fully charged. But it was only on there for maybe 4 hours today.
I think it's going to work fine.
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Chris
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How's it doing now?
I expect it'll take a couple/few days to get the battery up to a decent voltage, then it will keep it there just fine.
If the panel will be out side, probably want to open the frame, add some non-acid silicone (Dap 3.0?) to the wires on the back so keep them from corroding, and seal the frame a bit to keep water from collecting where it can freeze in the frame.
They were not designed to be outside.
G-
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After a couple days it's got the battery at full charge now. I checked the battery at noon with the panel unplugged and the voltage of it was 12.83 volts after I let it set about 30 minutes with the panel unplugged.
It must have some sort of regulator in that cigarette lighter plug. It had the battery up to 13.25 volts before I unplugged it. I would think that with the battery fully charged now that it would drive the voltage higher than that if it didn't have some sort of regulator in there. It was in bright sunshine too, and not very hot here today, so the panel was putting out full power.
I didn't take the plug apart. But Tom told me there's a little circuit board inside that plug. I assume that circuit board does the regulating when it's plugged into a 12 volt power source.
I took those suction cups off it when I got it, Then I took the four screws out and sealed the wires. I made an aluminum bracket to mount it to the genset housing and then I put some clear silicon in the holes where the suction cups were.
It's not sealed between the plastic housing and the glass. So to be safe I drill two 5/32" drain holes in the bottom of the plastic housing so the water can drain out if some gets in there. I think I got it pretty well weather-proofed. In the winter I'll unplug it and bring it inside because it's not needed then.
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Chris
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"It must have some sort of regulator in that cigarette lighter plug"
Not many VW PVs have the regulator built in, but that one does for sure.
They tend to regulate to about 13.7V or so, and have a pretty large hysteresis (0.3V?), but perfect for maintaining a FLA or SLA.
I think there are 2 types of regulators I have seen. They function the same.
But like I said, most VW PVs do not have them.
Inside the plug, it looks something like this...
[attachimg=1]
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That looks like the unit I got. That's pretty cool how they stuck that little circuit board in there. :)
We have a very heavy overcast today. So heavy that 2.7 kW of installed solar capacity on MPPT is only putting out 320 watts. So the little genset battery maintainer is not putting out much power. The genset battery has "sagged" to 12.55 volts. Which is not discharged by any means. But the little solar panel will not make the one amp-hour today that is required to offset the usage of the electronics in the generator.
But it has proven that it can "catch up" on the next sunny day.
I'm pretty sure the battery in the generator is 12 amp-hours. So I would assume that if it gets 6 amp-hours pulled out of it that it's down below 12 volts. The generator will still start with the battery discharged that low, but it's not good for the battery.
Generac recommends exercising the generator every seven days. The only reason to exercise it at that 7 day interval is to maintain the battery. It's got a brushless generator in it so it depends on residual magnetism in the core to excite the field. It could sit all summer without running and the field would still excite without having to flash it. Exercising a generator once a week JUST to maintain the starting battery is bad design, to my way of thinking. And Generac does this on both their off-grid, and grid-standby units.
It would seem to me that Generac, claiming to build the "ultimate" off-grid standby generator, would think of putting a solar battery maintainer on the thing - built right into it. VW could've hired somebody to run around and start all the cars up once a week but they came up with this very simple solution that worked.
I'd tell Generac Customer Service about this, but talking to anybody at Generac is about as fruitful as talking to a dead stump in the middle of the woods. And you'd probably get better understanding from the dead stump. Generac has an excellent dealer network, and if you carefully select your dealer you can get good service on your generator installation. Their factory customer service sucks real bad.
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Chris
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Inside the plug, it looks something like this...
(Attachment Link)
Whatever it is that little circuit board does in there, it works really well. That VW solar panel floats the genset starting battery all day at 13.25 volts - it never goes over that. I have checked it now and then to make sure this is going to work long-term. I now have no doubts it is working fine, and will not harm the battery by over-charging it or anything.
It is unlikely from this point on that the generator will be run at all thru the summer months, except for its monthly exercise for 30 minutes. It's pretty amazing that the generator electronics draw about the same amount of power as the little panel is rated at for output, but it still puts out enough "extra" to keep the battery right up to 100% SOC.
What's kind of funny is that my wife didn't notice the solar panel on the generator until three days ago. She went out to our camper to get a cast iron skillet out of it. As she was walking back to the house she suddenly stopped staring at the generator.
I was working around there and after a few seconds she says matter-of-factly, "We got a solar panel on the generator."
"Yep"
I don't think she knew what to ask but finally she asked the question that was obviously plaguing her: "So........what does it do?"
"It keeps the battery in the generator charged up."
<a few seconds while she absorbs this tidbit of information> "Oh. It's cute. We have solar panels on the house and the shop and the generator." And she disappeared into the house.
LOL!
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Chris
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Inside the plug, it looks something like this...
(Attachment Link)
Whatever it is that little circuit board does in there, it works really well. That VW solar panel floats the genset starting battery all day at 13.25 volts - it never goes over that. I have checked it now and then to make sure this is going to work long-term. I now have no doubts it is working fine, and will not harm the battery by over-charging it or anything.
It is unlikely from this point on that the generator will be run at all thru the summer months, except for its monthly exercise for 30 minutes. It's pretty amazing that the generator electronics draw about the same amount of power as the little panel is rated at for output, but it still puts out enough "extra" to keep the battery right up to 100% SOC.
The circuit in the VW PVs (the ones that have the circuit in there) usually regulate to about 13.7V average, maybe 13.5 to 13.9V.
The hysteresis is about 0.3V to 0.4V, with serious slop from one to the next.
Meaning (in good sun) it can cycle on a full charged 7AH 12V SLA (in decent condition) maybe 3 to 20 times a minute? Cycling also depends on the actual SoC of the battery, not just the terminal voltage.
What you are seeing now is very similar to what you saw earlier.....
The battery was at 12.44 volts when I plugged it in. It took about 30 minutes and it had already come up to 12.92 but it wouldn't go over that.
Now, the power it is putting into the battery is basically balancing out to keep the battery at 13.25V.
Earlier, it was balancing out at 12.92V.
Later, mid summer, it will be higher, and may even start to show the hysteresis if it cycles from 13.8 to 13.5 to 13.8 to 13.5....
If the battery or drain is too large, it may never make it up to the point of shutting off.
The controller in it is not overly fancy, and the PV is small enough to hve a low risk of overcharging a car battery with any drain at all.
VW must have figured that out at some point, or some of their PV maufactures did, and thats why most do not have the built-in controller.
Most VW PVs only have a blocking diode.
All that pertains to the old crystaline PVs. I don't know about the newer amorphous type, or the newer newer amorphous type with the computer OBD plug end.
G-
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Later, mid summer, it will be higher, and may even start to show the hysteresis if it cycles from 13.8 to 13.5 to 13.8 to 13.5....
I'm happy to report that this little 3 watt solar panel is doing an exceptional job of keeping the battery up in our genset. I checked it 2 or 3 days ago and it had the battery up to 14.0 in the beautiful sunshine.
I looked at the inverter and it says 3 days to gen exercise.
[attachimg=1]
If the generator fails to make its appointment at the gym this time, it won't be because of a dead battery ;D
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Chris