Looking for charge controller suggestions

[bschwartz]

It looks like I'll be buying a remote property/vacation spot about 4 hours from my home.
It has a 29 foot travel trailer connected to a ceptic system, and grid power.
I'd like to keep a freezer with food, but we may not get the chance to get to this location for weeks/months at a time.
The grid power is known for going out for hours to days at a time due to it's remote location.

I have (but may not use all) 10 Evergreen 210 watt panels, and an Outback GVFX3648 inverter.  I will not be using the grid tie for backfeeding the grid, only for sensing when the grid goes down, and provide backup power to fridge/freezer.

I plan on just using 4 car/golfcart batteries, as I think they would be enough to keep a freezer alive for a few days during an unsupervised outage.

The only part I still need is a charge controller.  Efficiency isn't really an issue, I just need something that will play with the Outback (if it even matters) and will work with 48v.  Cheap and reliable is the name of the game, power losses are a non issue, as 99% of the time the batteries will simply stay charged with no real use.

OK gang...... throw me your suggestions.

[Mad_Labs]

I have a Classic 150, been using it for 6 months now and I love it. It milks more juice out of the panels than my last controller

If you are going 48V, you will need more than 4 golf cart batteries. Are you going to run 24V for now? Also, 4 batts sounds a little small for unattended freezer back-up. Take a look at freezers and get a kWh/day on them. I would want to plan on at least 3-4 days with little solar input, food is expensive.

One thing to make sure of with all MPPT controllers is that your panel voltage is higher than your bank voltage by a decent margin. With out this overhead the MPPT won't work as well as possible. The Classic 150's sweet spot on the power curve is with the panel voltage around 90VDC.

Jonathan

[mike90045]

I was going to say the Midnight Classic, but someone beat me to it.

[bschwartz]

Yes, 4 golf cart batteries wouldn't work.  I meant to say 4 car batteries, or 8 golf cart batteries.
The Midnight 150 is a very nice charge controller, but $650!!!!!

I'm looking for an inexpensive sturdy unit.  It doesn't need to be fancy, efficient, MMPT, etc. 
The size freezer I'm looking at is listed at 277 KWH per year (about 750 watts per day)
The freezer will be in a non heated area, probably in a shed, so snow covered panels won't matter in the winter (heck the freezer will use less power anyway).
In the summer, we get 99% sunny cloudless days in central New Mexico.

Has anyone used the Morningstar TS45 Pulse Width Modulated units or similar?  They cost about $150 (4 for the price of one Midnight unit!!)
No, they aren't near as nice a unit, and if I were powering my house, I'd go for the better, higher efficiency unit like a Midnight.
Really the decision is based on three factors
1.  48V
2.  reliable
3.  Cost

Thanks again for the input.

[deeiche]

It looks like I'll be buying a remote property/vacation spot about 4 hours from my home.
It has a 29 foot travel trailer connected to a ceptic system, and grid power.
SNIP

congrats, land in NuMex or outside?
I need to start working on the land outside of Cuba .

[Mad_Labs]

The Classic is expensive. You can get the "lit" version for $500, but I suspect that is still more than you want to spend. And I get cost, I only managed to cough up the money for a classic after 4 years living off-grid.

One last little plug for it though...

Very flexible, can charge any voltage bank and can accept high voltage input, which allows you to save on wiring. Will allow you to upsize your system for when you are there and hogging down on power yuorself.. Milking every little bit of power will come in handy sometimes and will make your battery bank last longer, which is alwaysthe biggest expense in an off grid system. Very reliable. Food is expensive and what a nasty mess to clean up if something goes wrong. Midnite also makes the best lightning protector available. I've seen some fierce lightning in NM.

Don't use car batteries. Waste of time and money. Use golf cart batts. I make sure the date codes are the same when I buy new batts for a bank.

I'm planning on gettting a chest freezer myself this year. The midnite has an output that goes high when the batts are floating. I'm going to hack the freezer thermostat and set it to pump the freezer to a lower than usual temp when the batts are on float. So during the day when there is surplus power I will spend it pumping the freezer. When off float go back to the normal temp setting. This will reduce the power used at night. And the depth of every discharge counts for battery life, again the biggest expense and PITA.

Jonathan

[mobile_bob]

you might want to look into companies like www.rparts.com

they have all the info, books, and parts to build freezers and refer units of all sizes
at least in the range we are likely to need.

in my opinion it is entirely possible to build up a chest freezer that could be driven nearly 100% off of solar, especially if you limit access to the contents to daylight hours only.

for the project i would probably not go with an mppt type controller as it is probably not needed. the cost difference between a mppt and a pwm controller likely could buy enough panels to run the freezer on their own.

i think with a little effort a moderate size chest freezer can be either bought or certainly built to operate on less than 2 kw/hrs per day, maybe much less. unless you live in a very cloudy or shady area it wouldn't take many panels to do the job, thus leaving the batteries to do nothing more than provide a layer of backup.

if i were to go about this project i would get something that would work on maybe a kw/hr per day, power it with a ups that is around a 1.5-2kva unit with a 24volt dc battery bank... replace the batteries with two agm batteries of maybe group 31 size and use the grid to maintain them primarily and also feed the batteries with the solar panels via the pwm controller.   i would use a 1.8kva made by APC table top model, as they are pure sine wave and are very robust, being able to start a refer/freezer no problem.

this is the system we set up for my younger brother for his freezer which he keeps loaded with beef and venison and it works very well indeed.

the advantage of the agm batteries is they can be deeply cycled and left flat for much longer periods than flooded cells and then recovered to a much better capacity. this would be a concern of mine on a system where i would be absent for long periods of time. agm's also won't freeze or be damaged if subjected to freezing temperatures if they go dead.  the advantages of the agm for this type of use in my mind offset the price difference.

using the ups system, all the switch gear from utility to battery backup is all included and works without a glitch, just plug and play.

bottom line, i think you can build a very useful and successful solution to the problem without breaking the bank.  it sounds like you have ample amount of panels to use, so maybe the difference between the cost of an mppt vs pwm controller could be used to offset the difference in two agm batteries and two flooded batteries to power the APC 1.8kva ups.  pwm controllers are about rock simple and robust which might be something to consider too.

a couple years back we bought a mid size chest freezer from sears, i put a killawatt meter on it and tested it over several days, it averages about 1.5kw/hrs per day in useage and uses something like 150watts iirc to run... that doesn't take too many panels to cover that, the batteries and inverter can supply the surge for startup so maybe 200 watts of panels is more than enough to cover its needs?

i got enough panels, ups systems, an extra set of agm batteries, hmmm all i need is a pwm controller so maybe i too will give this a whirl!

bob g

[bschwartz]

Deeiche, here in NM (Catron).

Mad_Labs, OH, if I were offgrid it would be a whole different story.  This property just had grid power brought in (cost about $23,000).  This system will ONLY be used for emergency backup for freezer if the grid should fail.  I just can't justify a $500 charge controller (the other stuff I already have, or I wouldn't even bother with this project) for a small chest freezer that may hold $300 worth of food while we are away.
I'd go the UPS route if I didn't already have the panels, and grid-tie inverter with pass through capabilities.

I respect your suggestion and would go that route if my situation were different.

[deeiche]

Deeiche, here in NM (Catron).
SNIP

cool, I used to own land near Aragon

[Dualfuel]

We have three Xantrex C60 pulse width modulated charge controllers here...they charge three different golf cart banks...they cost ~$100. One kept the UP camp bank charged for 7 months last winter unattended. I would vouch for them...we also have an electric fridge that we keep cold with one of the Xantrexes in the system. They can be configured 12, 24, or 48 volt

The only cheaper one was for 7 amps from northern tool.
I would be interested in finding a small charge controller my self...something around $30. (Dream on!)
BPJ

[Mad_Labs]

Oh, I didn't realize it was just a backup and that you have grid there. Gotcha. I guess when you said cabin I assumed, and we all know what that makes me! :-)

So, as Glida Radner said: "Never mind".

Jonathan

[d34]

Why not just keep your solar panels at home where they are safe and use the Outback inverter as a UPS?  It can charge the batts when the grid is restored.  I would hate to "advertise" what you have by having panels. 

[BruceM]

Solar panels on not-lived-in homes here disappear quickly, but not all areas are the same.  You would at least want to roof mount them to make them less accessible.

I've used the $15 on/off type controllers for 12/24V from ebay, us sellers, in my engine room and pumphouse/battery bank buidling 12V systems. No problems, well heat sinked internally.  16A max, though.  The set voltage must be seasonally adjusted as they have no temperature sensor. 

Don't know what's out there for 48V in cheap PWM controllers but I'm sure there's something.

[bschwartz]

Ding-Ding-Ding........ We have a winner!!!!

D34, What a simple elegant solution!!!!

I read your suggestion, and slapped myself in the forehead.

No charge controller needed, and I can try to sell my extra 2000w of panels.
All I need to buy are some batteries, cables etc.
This is why I'm so glad to be part of this forum.  Briliant minds around the world coming together to solve problems.

Thanks for everyones suggestions.

D34, where do I send the beer?

[d34]

Well I just opened a liquor store 5 months ago.  I think I have plenty of beer.  I could use a few thousand watts of solar panels tho.   


Glad I could help.