Author Topic: My first real array  (Read 5072 times)

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Offline MadScientist267

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Re: My first real array
« Reply #15 on: May 06, 2013, 06:48:40 AM »
Figured a few might be curious as to what this thing all looks like on paper... There's nothing really super special about it really... Just the as it sits version I began working up to help me keep track of what is and what isn't.

 I'm pretty happy with the functionality of it all, so far it has withstood the test of time... Today makes about the 3.5 week mark, 12.7V first thing in the morning with no real useful sun in a couple days. Provided I pay attention to the clouds to come, it's certainly doable.

As soon as I finalize the console layout, I'll put up some pics of the cluster and wiring... Still deciding on whether or not the MPPT ammeter provides any real useful information - it's regularly in conflict with the "net" ammeter on the cluster due to a gain issue I really don't see much point in hunting down.

There are a few other little quirks about the layout, but nothing serious. I've pretty much got the information I'm after all in one place now, so it won't be long before I get tired of looking at the mockup props holding it all in place and finalize this thing. ;)

ila_rendered
 Click it for higher resolution...

Yes, I'm aware the file is a bit "pricey" for what it is... It's tricky to get a hand drawn schematic tweaked up and dialed in while keeping the resolution up and file size down. Blame the joint picture expert group for that. :)

Until next time...

Steve
Wanted: Schrödinger's cat, dead and alive.

Offline MadScientist267

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Re: My first real array
« Reply #16 on: May 31, 2013, 11:23:51 PM »
 Little update...

Still going... In fact almost TOO much...

Heat is becoming a problem now with the batteries, regularly hitting 100F core temp by the end of every day. Day time air ambient is hitting only low to mid 80s, and if this summer is anything like the last, I'll be working with lead soup that just happens to have sulfuric acid mixed in with it before August is up.

I have a master plan to deal with it, but only some of the parts at hand at the moment, and so after first reducing charge current yesterday and  micromanaging the charge process today with only a "gain" of 2F down to 98 or so and less than full charge at the end of the day, I implemented the parts I *do* have on hand to get the ball rolling.

ila_rendered

Next will come heatsinks along the "water lines" of the batteries to aid in heat extraction at night when it can pull it down easier. If its effective enough, I'll make another differential thermostat that shuts the fan down when it either wouldn't do any good (or worse, warm them more), or gets down to about 80F or so to save power. This fan is hungry, pulling about 7W by itself at full throttle (measured), but isn't afraid to move air either.

Its also a noisy little device, and the foam only amplifies it.

The cool air is sucked in at the bottom of the batteries through a 1" or so slot (currently implemented with cardboard as a test, the final will be the same 2" foam as everything else), and flows evenly across the entire front wall of both batteries, up over the top, and out. The gap between the batteries where the temp probes are has been taped over to prevent the cooler air from providing false readings/charge adjustments.

I'll put a better pic up when I put the heatsinks on, but for tonight, I just wanted it working, and this is all that's really visible.

Steve
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Offline MadScientist267

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Re: My first real array
« Reply #17 on: July 12, 2013, 02:21:53 PM »
Little update...

The heat issue got out of control to the point that I had to go as far as reconnecting the grid to keep the batteries at float rather than let them add to the problem by generating more heat internally.

The heatsink solution hasn't come to fruition yet due to a lack of supplies, namely the heat spreader plate that will go between the heatsinks and the battery casings.

However, having the heatsinks in the cab waiting for the plate has illustrated that thermal mass needs to be removed strategically from the cab, and that shielding is a viable workaround.

 Cab ventilation is also going to be key but I don't quite have that implemented yet either, at least in the form I intend to use. A forced air exhaust is going to be critical before summer is over and done with, but for now, with shielding, there has been a marked improvement, and for the first time since late spring, I've managed to get the core temp down to ~78F, and it looks like I will be able to get it a bit lower than that over the next couple of days, as the weather has provided a break for the time being.

I also found that by removing the heatsinks before starting the fan, and placing them back in the cab before sunrise, that it helps significantly in keeping the ambient temp in the cab under control. Latest experimentation shows that about 14 hours in (12am to 2 pm or so) provides a decent level of passive cooling with minimal effort. For the remaining 10 hours, they are  outside and in the shade, releasing their heat to the atmosphere.

 The shielding is helping significantly and allows the heatsinks to absorb only ambient heat, rather than becoming hot due to incident sunlight. At certain points of the day, it is now more beneficial to have the doors closed rather than letting ambient temp breeze blow through.

I will still be putting the heatsinks on the batteries as soon as I locate a suitable spreader plate, but there for a while it was looking like there wouldn't be much point. Not anymore... ;)

Time will tell how well the concepts of shielding, "absorbing/displacing", forced ventilation, and sinking the batteries will work.

For the last couple of days, I've been allowing the solar to do a sort of faux absorption charge phase,  with the grid charger set to only allow a shallow discharge at night, to see if the temps stay under control. So far so good. Once I'm convinced the system in play will be effective, I'll drop the grid and go back to normal cycling with a watchful eye.

In the mean time, I've gotta find me a suitable chunk of aluminum... The quest continues. :)

Steve
Wanted: Schrödinger's cat, dead and alive.

Offline bj

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Re: My first real array
« Reply #18 on: July 13, 2013, 07:27:39 AM »
   So, the question would be " how big a chunk"?  I might have, or be able to find what you need.
   Shipping might be cheaper than paying retail where you are?
   Just a thought.
"Even a blind squirrel will find an acorn once in a while"
bj

Offline MadScientist267

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Re: My first real array
« Reply #19 on: July 14, 2013, 09:27:29 PM »
 Well, still tossing around some ideas... But I might have found a very viable solution...  Time will tell. I appreciate the offer for sure ;)

Got a rudimentary forced air vent put in, passenger side window... Tomorrow it will get a good trial, and if all goes as planned and I see decent numbers, I'll be returning to normal cycling of the batteries.

A couple of pics:

ila_rendered
Inside


ila_rendered
Outside

Moves some decent air, nothing extreme, but is fairly quiet unlike its little brother pumping out the battery box. If this works as envisioned, it will eventually be replaced with a squirrel cage blower feeding a vent that will go in the roof.

Stay tuned, more as it comes.

Steve
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Offline rossw

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Re: My first real array
« Reply #20 on: July 14, 2013, 11:38:36 PM »
Moves some decent air, nothing extreme, but is fairly quiet unlike its little brother pumping out the battery box.

I used to put fairly large 24V fans in my old 4RU server cases, and ran them on 12V.
Such large diameter fans, at half voltage were almost silent yet still moved a lot of air.

Offline MadScientist267

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Re: My first real array
« Reply #21 on: July 24, 2013, 06:36:10 PM »
 Yep. Useful trick... There seems to be a growing trend amongst manufacturers doing that very thing. I do the 12V fan on 5V on many of my projects, and have seen it done many times in commercial equipment. The beauty of it is that they're quiet, have a longer life, and can potentially be throttled up if conditions warrant it.

Conditions have improved, the shielding and cab ventilation have brought the temps back into a normal range and things are back on track and running on solar.

In the next couple of days, I'll be putting the new heatsinks on the batteries (thanks DaveW!) and optimizing the battery box. I'll also be preparing it for use with a differential thermostat based on a 08M2 PICAXE, my first real experiment with a PIC from the ground up. Should be interesting.

More to come... ;)

Steve
Wanted: Schrödinger's cat, dead and alive.

Offline MadScientist267

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Re: My first real array
« Reply #22 on: July 27, 2013, 03:43:53 AM »
 Had a decent post scratched up, phone managed to lose it for me... Grrrr

Anyway, the heatsinks are on, albeit without goop for the moment. Turns out this may have been a useful trial even before any performance is known. Installing these things in-situ is much more difficult than it would appear because of the tight fit they have in such close quarters. The lesson learned is that I should probably remove the batteries to do the final install, unless making a serious mess is part of my goal.

Even without the elusive goo, performance is decent. Without logging it has been difficult to tell exactly what conditions lead to which results, but the average drop with no heatsinks at all, 7F difference between ambient and core, and fan at full throttle, is about 1F/hour.  With the heatsinks installed, I'm seeing approximately 1.5F drop, all else equal. They may be performing better than this however, as the core is falling faster than the ambient, and as of last check, the difference was only 5F, yet they are still dropping at about the same rate. Time will tell, but it appears to be working well so far.

Adding goop of some form will only improve efficiency, resulting in less power needed to achieve the target temperature. With between 5 and 10% SoC being spent on cooling each night, every bit counts. I hope to reduce this to somewhere between 3 and 5% before this is over with. The differential thermostat will certainly play a big role in this as well.

ila_rendered
A shot from the top down. Not a common sight from what I can tell. At least not on lead acid. ;)


ila_rendered
Another view from the side. Each sink is 10" x 6.5" x 1 3/8" (3/8" substrate + 1" fins). Pretty good size chunk of aluminum.

That's all for now... They will likely run like this for a bit until I get the thermostat parts in and put together, as well as find a suitable heatsink grease that fits the bill. Might just end up going with plain old non-drying classic white stick-to-everything goo, even though the allure of finding a dirt cheap DIY solution is being sought out. Either way, I can't complain, this is essentially the final piece of the puzzle.

Till next time...

Steve
Wanted: Schrödinger's cat, dead and alive.

Offline bj

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Re: My first real array
« Reply #23 on: July 27, 2013, 08:01:18 AM »
   Those are seriously nice heat sinks.  Got to help.
"Even a blind squirrel will find an acorn once in a while"
bj

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Re: My first real array
« Reply #24 on: July 27, 2013, 08:54:03 AM »
    Steve I'm glad to see them in use.  Still thinking on how to make a good heat sink paste on a budget that won't attack the batteries.

Offline MadScientist267

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Re: My first real array
« Reply #25 on: July 27, 2013, 09:52:43 PM »
Quote from: bj
Those are seriously nice heat sinks.  Got to help.

No fear, I'm sure the time will come. There are puzzles all over the place with this, and as I've mentioned before, you guys have all played a vital role in it becoming what it has. I'm certain the challenges will not end here. ;)

Dave, I've almost given up on the idea that its going to be all that cost/time effective to go the DIY route with the goop. Being a "gotta hold it in my hand to buy it" type, even a 2 oz tub of goop won't be all that bad, coming in at a touch over 20 bucks at the semi-local electrical supply joint. I could get it for 10 or so online, but... LOL

Last night the temps tracked fairly close, and the core bottomed out at about 72, intake temp for the sinks getting down to about 69. Tonight I'm running the fans at about 1/3 power input (total) to get a feel for how they perform with minimal flow. From what I can tell even already, things look promising.

The sinks didn't add much if at all to todays rise. I gained 12F,  bringing them to 84, which is a little elevated, but charge currents were also higher and ran for longer thanks to a deeper than usual discharge from running the laptop, stereo, etc while I was working on the heatsinks and batteries.

Tonight appears to be heading for similar temps as last night, so we will see. Anything less than 75 in the morning and I'll be ecstatic ;)

Till next time...

Steve


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Offline MadScientist267

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Re: My first real array
« Reply #26 on: July 28, 2013, 05:17:01 PM »
Performance wasn't as good as expected, but I believe it was due to elevated cab temp.  With the vent fan throttled back, it the temperature didn't drop in there as far as they could have. To complete this, aside from the thermostat, a more powerful vent and/or a cool air intake down low in the cab will be necessary. This is also supported by the fact that the vent is much more effective if the driver door is cracked open to allow air to flow along the floor on its way to the batteries.

Since the thermostat will be set up to handle both heating and cooling, I am strongly considering a vent pipe of some sort that will be routed directly to the outside. Dryer flex vent comes to mind.

All of that said, the cooling at the minimal fan speeds was approximately double from what I have seen on average, bottoming out at 77.5F last night. Tonight I will be running the throttle for the cab vent at max power and the box vent fan at the same throttle as last night. Similar temps expected, so we'll see.

Steve
Wanted: Schrödinger's cat, dead and alive.

Offline MadScientist267

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Re: My first real array
« Reply #27 on: August 03, 2013, 11:44:30 PM »
Update time...

The outside temps here are fluctuating a bit, making it a little more difficult to keep track of what's what. Regardless, I have managed to keep the core temp in the comfortable range, not going above 86F, and typically bringing them down to between 74 and 80 depending on outside. So the heatsinks are definitely helping. I've caught on to a fairly stable constant - whatever the forecast low is for any given night, I seem to be able to get the core down to within about 4 degrees of it. Can only get better with the addition of the goop.

Which, is here. A whole pound of it. Sheesh. I should run out of solder before I ever use this tub of goo up.  ::)

Corner braces for the zip ties also cut. A plan for additional insulation to reduce heat influx from ambient temps in the cab, and an idea for directly taking in the outside air without breaching the firewall or floorboard is also on the table. I'm looking into cutting a vent into the passenger door with a screened louver on it to stop rain/bugs/etc. The cab has too much thermal mass, and is proving to steal precious cooling time away because currently it must be brought below core temp before actual cooling can begin. Should shave between 2 and 4 hours off the wait time by implementing this, depending on actual outside conditions.

Interfacing it with the door will be fun, as I don't want to have the vent hose directly attached, although it may come down to that for simplicity's sake. Currently (if I didn't accidentally throw it out on the last trip to the storage unit), I have a length of aluminum dryer flex vent that would be more than sufficient in terms of capacity, but probably wouldn't handle much repeated flexing. Opening the door is a fairly regular thing, as I also use that space as sort of an "attic", in addition to just checking on things and such. Maybe flex duct will be better at some point. Certainly, the added benefit of it being insulated can only be a plus as well.

As a stop-gap, I am also going to repurpose my existing differential thermostat to deal with the battery box fan. My whack sleep schedule isn't helping keep things cool. I currently go out each night, read a couple thermometers, flip a switch when it's time, and walk away until the morning comes. If I'm still up when the sun comes up, or if I wake up early enough, I kill it before the cab temp exceeds the core. When this doesn't happen, it continues to circulate air, undoing the progress made the previous night. I fully intend to have the thermostat controlled by a PICAXE chip before this is all said and done, but in the mean time, since there's still a few questions to be answered before I dig into designing it, the immediate issue of reheating needs to be addressed. The fans it currently controls are cooling a much less critical system and will tolerate being modulated by hand much more than the batteries can. They need all the help they can get!  :-\

The dryer vent interface will also be set up so as to minimize natural convection currents that might tend to flow, and will also make the changeover to the heating collectors that will lay over top of the batteries in the winter a snap. Keeping them warm was a challenge last winter, and even though I know I can do some of it with controlled overcharging, the energy might not always be available to do so, and is certainly not the ideal way to heat them as excessive overcharge can lead to positive grid corrosion, excessive water loss, and the like. So, I will have a more direct approach in place as the primary warming system. More to come on that as it comes to be.

With any luck, the weather will be useful and tomorrow evening I can put some of this into play. I plan to permanently mount the heatsinks with the goop, and put the differential thermostat in place, possibly cutting the additional insulation panels to add to the existing structure, bringing the total R value to 20 around the entire cab side. On the living space side, I will have to get creative to add the second layer - there's quite a bit of equipment crammed into the space immediately behind the batteries, although that space is itself insulated, forming somewhat of a double barrier. If only the components inside didn't generate their own heat... Having to run the aforementioned fans to keep that stuff cool kinda kills off the idea of it being "double insulated". Sue me, it wasn't really there as insulation to start with... it's just really easy stuff to work with and doesn't make a half bad surface to mount the instrumentation to.  ::)

Until next time...

Steve
Wanted: Schrödinger's cat, dead and alive.

Offline MadScientist267

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Re: My first real array
« Reply #28 on: August 07, 2013, 01:30:03 AM »
Success!

Then failure...

... and finally, success!  :o ::)

Everything went very well, considering. Pictures are worth a thousand words, right?

ila_rendered
That's a quarter of a pound of your everyday silicone/zinc oxide heatsink compound. A layer on the battery, and a layer on the heatsink. The stucco appearance is from separating them after repeated mating checks to make sure there were no gaps. I figured 2 oz would cover both batteries... But that one pound tub sits right at about a half tank with all said and done, and there was very little oozing; maybe a half ounce total if I had to guess.  ???



ila_rendered
Anybody that's attempted to remove a heatsink from a CPU with a spreader plate on the die knows that the stuff gets a grip. It holds true in batteries as well apparently.



ila_rendered
Eventually, it would give way to fatigue and come off, or slide off to one side and become detached. Couldn't have this happening, so back on with the zip ties.



ila_rendered
On the back side, I used aluminum angle to spread out the pressure that would have been on the case of the battery itself. They are cinched down much tighter than they were for the dry test, and I didn't want to risk damaging the casing. Everything is much better off if the acid stays inside the cells.



ila_rendered
There has been a bit of debate as to the ideal location of temp sensors. Some argue that the sensors are best placed on one of the posts, the idea being that the lead conducts the heat of the core back to the post and provides a more accurate reading than if the sensor were placed on the side of the battery. For a battery/cell that is open on all sides for ambient temperature air flow, I'd agree. However, due to the way these two batteries are housed and insulated, the side of the case actually provides a more accurate reading than the posts would. Being forced air cooling, the posts would see a lower temp by the air flowing across the top of the batteries. In the pic above, there are 3 sensors, all within about 2 inches of each other in a V. A gasket 2" wide and 3/4" thick, sealed both on the inner and outer perimeters by tape provides an airtight seal and a chamber that completely blocks out errors caused by the cooling air. The original layout before heatsinks were ever a consideration involved only a tape seal around the outer edges of the batteries, and this did cause the measured temp to have some notable "play" in it when the fan was turned on or off. With this, it is now rock solid.



ila_rendered
Here is a shot of the heatsink <-> seal interface. This was very difficult to pull off, as it took forever to get the grease completely removed from the faces that needed to be taped. As you can see, it involved getting creative and using the most accessible faces of the heatsinks in combination with the structure of the tape itself, and the unbroken seal on the inner perimeter. The result is a good solid seal. At the very bottom in the center is the intake temp sensor for the differential thermostat.



ila_rendered
The much improved passage for the temp sensor wiring.



Everything worked exactly as planned once it was all put together. I stayed up with it to tweak the thermostat so it would cut off at the appropriate time, and checked on it from time to time throughout the day to find out the point at which it would bring it back to life.

Along about the late afternoon hours, I noticed the LED that indicates the power for the fan was on. At first, I only thought of it as a little early for it to engage, but a quick peek at the thermometers revealed that it was in fact on it's mark. The day began with heavy rain, and remained cool for almost the entire day. I had some extra insulation on the batteries and had actually lit off the SMPS charger to fill them back up as well as artificially raise the temperature when I realized the sun wasn't going to do it naturally.

But then I noticed that the LED was cycling, and had an odd flicker in it right before it would cut off. This definitely wasn't normal. A quick check of the fan revealed that not only was it not turning, but it's motor had become very hot for some reason. I have my suspicions, but I don't know for sure. Either way, it was dead at that point. One high performance 4" brushless fan, junk.

To get things back going again, I had no choice, I had to use the fan that had been venting the cab to pull air through the battery box. It's a very similar fan, slightly larger and has a thermister in it that I bypassed to make the motor run at full throttle all the time. It's knee isn't in the right spot, so it would slow down way before I needed it to.

To protect the fan, I ran it through a current limiting buck converter (it needed to be slowed down anyway, so this worked out). The batteries are now once again cooling and with 5 hours or so before even twilight, there's little left for it to do. It's drawing a fraction of the power that the other scheme was as well.

Both last night and tonight so far have demonstrated that the core temp can be brought within about 2F of the intake temperature, which (up until the fan failure) could generally be brought to within a couple degrees of ambient outside.

All in all, I'm pretty satisfied with how this has gone. Much thanks once again to DaveW for the heatsinks. ;)

Now on to reinventing the cab vent  :-\

Till then...

Steve
Wanted: Schrödinger's cat, dead and alive.

Offline MadScientist267

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Re: My first real array
« Reply #29 on: October 30, 2013, 06:15:36 PM »
 Well, its that time of the year again...

The cooling system has been working flawlessly in keeping the batteries cool.  Before I go into the next chapter, a little catch up is in order...

Not long after implementing the thermostat, I had the insight to make it reversible, and then put the controls for it on the instrument cluster. It now has the ability to run in reverse, so as to heat the batteries in the winter if necessary. There are two switches, one for off/on/auto, the other for heat/cool. In this particular instance, I didn't use any direct power control for any of the functions, instead, I manipulated the signal that the control chip sees. For forced on/off, the signal is biased high/low respectively, well outside the operating range of the thermistors, and auto of course is unbiased. Winter/summer mode is done by flipping the sensors electrically, so that instead of a warmer core pulling the signal toward high, it tends to pull it low. All in all, works well.

So, that led to the next piece of the puzzle. There's a significant difference between the roofline and floorboard temperatures in the cab, as much as 30F, and while the original cooling behavior was set up to pull air from as low as possible in the cab up across the heatsinks and through the fan, this wouldn't work for heat mode, as it would be rather inefficient. To deal with this, I've built an intake box out of cardboard and dryer vent line, to pull the warmer air from as high in the cab as practical. I also have moved the ambient temp sensor to the suction side of the vent (intake) tube.

Of course, its all held together with duct tape, but this is what I've come up with...

ila_rendered
I did have to peel the second layer of insulation foam off of the containment to pull this off. An Astro just isn't set up to  hold all of the things that need to be present to support all of this, but I made it fit.



ila_rendered
After installing the new intake (which as you can see required an in-place "hack"), there was barely enough room to get it past the doghouse. Most of the space issues were at the bottom, and having realized this after making the modification, it was clear that there was only one way to make it properly fit, and that was to remove the rear insulation and slide the batteries back about 2 inches. The entire box then needed to be trimmed by a similar amount. At this point, being low on materials, I noticed a significant gap at the top of the doghouse as a result. To keep the air gaps as small as possible where the batteries meet the  electronics container, I needed to put pressure on the box to help hold it shut. That's the job of the two wedges in the pic.



ila_rendered
A shot of the intake side, showing the roughly 3 inch gap between the tube and the headliner, along with the two sensors (the visible one controls the thermostat, the thermometer sensor is just inside the tube).



ila_rendered
A shot showing the routing of the whole thing.

Time will tell if this is viable, but in theory it works, as I've been watching the temps for a few weeks now. During full sun, the area where the intake is sees a full 40F rise above outside, so there should be no risk of freezing, unless I go to one of those horrificly cold places and beg for punishment ;)

Till next time,

Steve
Wanted: Schrödinger's cat, dead and alive.