Author Topic: Finding a 120v DC Power source for my MPPT Controller  (Read 11310 times)

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BradKW

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Finding a 120v DC Power source for my MPPT Controller
« on: November 21, 2016, 04:49:14 PM »
Hello! By way of introduction, I am a carpenter who is currently building out a box truck into an off-grid camper...and what little electronics understanding I have has been hard won over the past year by reading mostly online forums. That is to say, the wiring aspect of this project is challenging for me. None of this is operational yet, but:

I have 840 watts of solar on the roof, running to a Morningstar TriStar 60 MPPT controller, which will charge my bank of Trojan L16 batteries... four 6v 435AH, set up as a 24v bank.

I already have an inverter, so buying a inverter/charger combo isn't an option...but I do want a charger as part of the system. After some email exchanges with Morningstar's Tech Support, they say it is fine to run a constant DC source into the CC so long as it does not exceed the unit's rating. This has a number of advantages, mostly more granular control over charging, and addresses the issue of virtually zero mobile "smart charger" options can be found that satisfy Trojan's specs for L16's.

I would really appreciate help choosing a DC converter that will fit my needs...and will understand how to operate. I say that because I've come across some interesting options, but they are not geared towards the average end user. For example, the Meanwell RSP-1500-48 ( http://www.mouser.com/ProductDetail/Mean-Well/RSP-1500-48/?qs=%2fha2pyFaduh13piwcvKl2%2fAFGPMw7GaUgJprFTsg%252bElrOwemtRHVJA%3d%3d )

I look at the spec sheet on that and feel I don't have the ability to control a device like that...

My TS-60 controller will accept up to 1500 watts for a 24v bank, so I'd like to come close to maximizing that. If I could get it to pump out 31v @ 60amps with a DC converter, that would be wonderful.

Thanks for reading   :)

joestue

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Re: Finding a 120v DC Power source for my MPPT Controller
« Reply #1 on: November 22, 2016, 12:05:04 AM »
the morningstar is probably a buck converter, so the lower the voltage you give it, the more efficient it will be. (but the less efficient the power supply will be... hmmm)

if that's the case than an efficient, off the shelf 48 volt supply is probably what you want. you might be able to give it as low as 36 volts

4 of these in parallel? http://www.ebay.com/itm/110V-to-DC-48V-8-3A-400W-Volt-Transformer-Power-Supply-for-Led-Light-US-S9T2-/131729317201
(that's a joke btw. and they do not have power factor correction so you will need at least a 20 amp circuit breaker in order to get 1500 watts of power off a 120vac source)

here's a serious suggestion:
 http://www.ebay.com/itm/Eltek-Flatpack2-241115-001-48V-Tested-/261660199965

i don't believe you need to do anything but apply 100-250vac and it will turn on. there are cheaper rectifiers on ebay so you may want to read the user manual for each of them.


anyhow concerning the meanwell power supply you mentioned, there is no controlling it. you can turn it on and off, and adjust the output voltage, but if you're intending to drive the morningstar charge controller as you imply, then the morningstar is what is going to determine how much power flows from the power supply into the batteries. and if they are close to fully charged then it should not be pushing 60 amps into them.

far as i know as long as the voltage into the morninstar is higher than about say, 35 volts, then it will charge the battery with up to its limit for output current. (there is voltage drop through its internal switches, so it needs more volts in than volts out)

another more difficult but cheaper (potentially) solution is to hack these things
http://www.ebay.com/itm/Lot-of-2-HP-DPS-600PB-B-575W-Switching-Power-Supplies-321632-001-/370867234589

you need to snip a wire internally and remove a screw, their output is then isolated. you can then buy 4 of them and run them in series to get ~48 volts.
instructions on that are here https://www.rcgroups.com/forums/showthread.php?t=1581061
« Last Edit: November 22, 2016, 12:20:44 AM by joestue »

BradKW

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Re: Finding a 120v DC Power source for my MPPT Controller
« Reply #2 on: November 22, 2016, 05:02:21 AM »
Thanks joestue, "rectifier" is a new word for me and has opened up a whole new category of search options. I think you're right, that 48v seems to be a common standard that fits...that Eltek you linked is close to what I want, just a little low on amps. Google shows they have a model that puts out 60 amps, but my eyes crossed trying to source it stateside.

The Morningstar CC shouldn't really see a significant loss of efficiency going higher voltage though, according to my understanding anyway. But maxing amps seems to be an important metric for bulk charging batteries up to 80% or so.

I've seen a few people use Meanwell switching power supplies to make DIY chargers, and some have encountered issues with the more powerful models not outputting proper current and/or not functioning with a DIY potentiometer attached. Conclusion was basically that the unit required properly set up with wiring harness and an understanding slightly higher than jumpering two pins with a rheostat in between. Who knows what the real story was, but given my level of understanding, it has me shying away from things that aren't obviously plug-n-play if you know what I mean.

OperaHouse

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Re: Finding a 120v DC Power source for my MPPT Controller
« Reply #3 on: November 22, 2016, 05:37:39 AM »
Where are you located?  I have a new telco 48V supply I would love to get rid of.  Heavy old school ferro resonant non adjustable about a KW.  If that CC is MPPT, think there are two versions.

oztules

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Re: Finding a 120v DC Power source for my MPPT Controller
« Reply #4 on: November 22, 2016, 12:51:32 PM »
I bought 4 of the meanwell chargers Joe alluded to.

They blew up in about 30 seconds... all four of them.... Fixed em up, and found the current limiter did not work in them... rewired the sensing stage, and modded the voltage, and now work perfectly well.... but did not work as a charger out of the box as they should have. They were trying to push out 25 amps each as the current limiter didn't kick in... should have been around the 7 mark. Work well at 10 even, but not 25amps ::)

Only the 2625 trannies failed in each of them.


..........oztules
Flinders Island Australia

BradKW

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Re: Finding a 120v DC Power source for my MPPT Controller
« Reply #5 on: November 22, 2016, 02:57:36 PM »
Where are you located?  I have a new telco 48V supply I would love to get rid of.  Heavy old school ferro resonant non adjustable about a KW.  If that CC is MPPT, think there are two versions.

Located in Key West...not that anybody is ever "near" here, but if you were coming on vacation anyway...   ;D

Mary B

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Re: Finding a 120v DC Power source for my MPPT Controller
« Reply #6 on: November 22, 2016, 03:38:23 PM »
Opera house, I might be interested in that power supply to power a ham radio amplifier...

welshman

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Re: Finding a 120v DC Power source for my MPPT Controller
« Reply #7 on: November 23, 2016, 01:05:36 PM »
the solution to your situation is a simple one.

you have a nice charge controller. you dont need a dc power supply.

what you need is a bridge rectifier on your 120v mains supply to turn the ac into dc and then feed the 120v straight into the tristar as if the mains is another solar panel. the tristar can accept up to 600vdc input and has a max 15a.

to stop the mains going back into your solar panels and possibly damaging them you will need to make sure they are already fitted with diodes that are capable of carrying the current.

here is a picture of the solution, you will need to add a fuse after the plug if you dont use plugs with fuses in. the rating of the fuse will need to be around 12.5 amps.

http://www.ebay.co.uk/itm/85A-1000V-BLOCKING-DIODE-WIND-GENERATOR-SOLAR-PANEL-85-AMP-PANELS-TURBINE-STUD-A-/121863653473?hash=item1c5fa3c861:g:y5QAAOxyA4ZROJo6

http://www.ebay.co.uk/itm/KBPC5010-1000-Volt-Bridge-Rectifier-50-Amp-50A-Metal-Case-1000V-Diode-Bridge-UR-/400990374500?hash=item5d5ce38a64:g:dwkAAOSwu4BV6sZx


sean_ork

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Re: Finding a 120v DC Power source for my MPPT Controller
« Reply #8 on: November 23, 2016, 01:57:47 PM »
Just the one minor issue with your nicely illustrated solution ......

It isn't CC

OperaHouse

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Re: Finding a 120v DC Power source for my MPPT Controller
« Reply #9 on: November 23, 2016, 02:18:34 PM »
Even I'm not that cavalier to make a trailer frame HOT, not to mention it would likely short out to ground.  But it does bring up an option of using a transformer with it.  I'm not sure how fast a charge you would actually need.  A 3KW or more 480 to 120 would work feeding the bridge if lower voltage transformers were not available. Rated winding current remains the same. Those are pretty cheap used.

I'll post a picture of that 48V supply after the holidays when I get up to storage.
« Last Edit: November 23, 2016, 02:23:26 PM by OperaHouse »

welshman

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Re: Finding a 120v DC Power source for my MPPT Controller
« Reply #10 on: November 23, 2016, 04:05:34 PM »
Just the one minor issue with your nicely illustrated solution ......

It isn't CC

insert inductor to take out ripple current and add a cap to the circuit to keep the peak voltage? what else is needed ? or are you saying that it can't be done like this? if the cap was added the voltage would be 170dc so a 8 amp fuse would be needed to keep it under 1500w.

Mary B

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Re: Finding a 120v DC Power source for my MPPT Controller
« Reply #11 on: November 23, 2016, 04:40:39 PM »
Absolutely use an isolation transformer if you use mains for a source! I bought an Iota DLS series charger that direct connects to the batteries if I need to boost them in winter.

joestue

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Re: Finding a 120v DC Power source for my MPPT Controller
« Reply #12 on: November 23, 2016, 07:13:17 PM »
I thought OP had a morningstar and it looks like it will accept up to 150 volts.

A capacitor or not, a rectifier will supply 120v*1.41 (peak, which is what matters in this case), and you have no surge protection either. --not to mention the isolation problem.
« Last Edit: November 23, 2016, 07:50:04 PM by joestue »

sean_ork

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Re: Finding a 120v DC Power source for my MPPT Controller
« Reply #13 on: November 23, 2016, 09:34:34 PM »
Just the one minor issue with your nicely illustrated solution ......

It isn't CC

insert inductor to take out ripple current and add a cap to the circuit to keep the peak voltage? what else is needed ? or are you saying that it can't be done like this? if the cap was added the voltage would be 170dc so a 8 amp fuse would be needed to keep it under 1500w.

Slightly improving the quality of the waveform, and adding a fuse still doesn't make it a CC source


oztules

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Re: Finding a 120v DC Power source for my MPPT Controller
« Reply #14 on: November 23, 2016, 11:39:53 PM »
Actually a capacitor, rectifier and inductor will make it a perfectly good replacement for the solar panels.
I use this combo to drive grid tie inverters for testing..... works perfectly. 50 uf will yield about 350 watts for a 240v system@50hz. ( 340vdc)... enough to get the mppt working.

For 110v system, then, 1.414x110= 155v open circuit... that could be the problem.


..........oztules
Flinders Island Australia

sean_ork

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Re: Finding a 120v DC Power source for my MPPT Controller
« Reply #15 on: November 24, 2016, 01:33:29 AM »
I suspect Welshman was suggesting parallel capacitance on the DC side - it might be worth someone illustrating a safer schematic.

OperaHouse

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Re: Finding a 120v DC Power source for my MPPT Controller
« Reply #16 on: November 24, 2016, 04:56:23 AM »
Just the one minor issue with your nicely illustrated solution ......

It isn't CC

Just what does CC mean to you.  On some boards it refers to constant current, others it means charge controller.  In either case I don't see how it applies here.

sean_ork

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Re: Finding a 120v DC Power source for my MPPT Controller
« Reply #17 on: November 24, 2016, 09:05:56 AM »
Constant current

What's keeping the current drawn by the charge controller below its maximum rating (in that illustration) ?

joestue

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Re: Finding a 120v DC Power source for my MPPT Controller
« Reply #18 on: November 24, 2016, 11:38:18 AM »
Constant current

What's keeping the current drawn by the charge controller below its maximum rating (in that illustration) ?

the charge controller is what determines how much current is safe to push into the batteries.

welshman

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Re: Finding a 120v DC Power source for my MPPT Controller
« Reply #19 on: November 24, 2016, 11:50:49 AM »
I thought OP had a morningstar and it looks like it will accept up to 150 volts.

A capacitor or not, a rectifier will supply 120v*1.41 (peak, which is what matters in this case), and you have no surge protection either. --not to mention the isolation problem.

the specs i looked at said 600v max input, not 150..

edit - after further investigation, some units only take 150v input, so the exact model will need to be clarified.
« Last Edit: November 24, 2016, 11:56:03 AM by welshman »

sean_ork

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Re: Finding a 120v DC Power source for my MPPT Controller
« Reply #20 on: November 24, 2016, 12:19:04 PM »
Constant current

What's keeping the current drawn by the charge controller below its maximum rating (in that illustration) ?

the charge controller is what determines how much current is safe to push into the batteries.

That's the answer to a different question - my question relates to the control of the input current to the charger, not the output.

sean_ork

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Re: Finding a 120v DC Power source for my MPPT Controller
« Reply #21 on: November 24, 2016, 12:29:14 PM »
After some email exchanges with Morningstar's Tech Support, they say it is fine to run a constant "current" DC source into the CC so long as it does not exceed the unit's rating.

The above quote relates - I've added what I beleive to be the missing word.

welshman

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Re: Finding a 120v DC Power source for my MPPT Controller
« Reply #22 on: November 24, 2016, 01:38:34 PM »
After some email exchanges with Morningstar's Tech Support, they say it is fine to run a constant "current" DC source into the CC so long as it does not exceed the unit's rating.

The above quote relates - I've added what I beleive to be the missing word.

If the array power exceeds the rating of the controller, the tristar limits battery current to the maximum rating and it can taper back the current to 0 amps if needed. This device will take raw fluctuating power in and charge a battery

edit - btw the tristar can only do its 60 amp output IF the input voltage is over 200V anyway.. so any voltage under 200 is going to be current limited by the controller..
« Last Edit: November 24, 2016, 01:43:10 PM by welshman »

sean_ork

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Re: Finding a 120v DC Power source for my MPPT Controller
« Reply #23 on: November 24, 2016, 01:41:15 PM »
After some email exchanges with Morningstar's Tech Support, they say it is fine to run a constant "current" DC source into the CC so long as it does not exceed the unit's rating.

The above quote relates - I've added what I beleive to be the missing word.

If the array power exceeds the rating of the controller, the tristar limits battery current to the maximum rating and it can taper back the current to 0 amps if needed. This device will take raw fluctuating power in and charge a battery

Is that a quote from the manual ?

welshman

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Re: Finding a 120v DC Power source for my MPPT Controller
« Reply #24 on: November 24, 2016, 01:46:46 PM »
After some email exchanges with Morningstar's Tech Support, they say it is fine to run a constant "current" DC source into the CC so long as it does not exceed the unit's rating.

The above quote relates - I've added what I beleive to be the missing word.

If the array power exceeds the rating of the controller, the tristar limits battery current to the maximum rating and it can taper back the current to 0 amps if needed. This device will take raw fluctuating power in and charge a battery

Is that a quote from the manual ?

a paraquote

btw the tristar can only do its 60 amp output IF the input voltage is over 200V anyway.. so any voltage under 200 is going to be current limited by the controller..

but that's assuming he's got a 600v unit.

have a look at Output Power vs. Array Input Voltage Figure 10-3 you might find it interesting as i did.
 
http://www.morningstarcorp.com/wp-content/uploads/2014/02/600V-TS-MPPT-Operators-Manual.pdf

welshman

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Re: Finding a 120v DC Power source for my MPPT Controller
« Reply #25 on: November 24, 2016, 01:54:44 PM »
since this thing is most efficient between 150 and 300 volts it might end up being more efficient with a step up transformer from the mains not step down..

and for the 150v version the input voltage needs to be between 110 and 140 volts to get the full 60 amp charge output.

sean_ork

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Re: Finding a 120v DC Power source for my MPPT Controller
« Reply #26 on: November 24, 2016, 02:06:32 PM »
Your paraphrase appears to relate to the pwm version - which allows a x1.3 input overload, then ramps down - then disconnects as a fault condition.

The MPPT version appears to restart after 10 seconds post solar input overload (assuming the condition is clear) - but a rectifier fed from the mains isnt  current limited, leaving scope for a problem - if it could be simply current limited ......

Page 54 relates.