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 Supplementing solar /charge controller question
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terracore
Punatic

5098 Posts

Posted - 04/05/2018 :  17:11:47  Show Profile  Reply with Quote
What are some good ideas for supplementing a solar array with grid power on those cloudy days that requires the least amount of intervention? Grid power is available, but no two-direction grid tie to Helco is desired?

There are some grid-enabled inverter boost systems like this:

https://www.amazon.com/Victron-Energy-Multiplus-Inverter-Charger/dp/B01AD2MJSK/ref=as_li_ss_tl?ie=UTF8&qid=1465093938&sr=8-9&keywords=victron&linkCode=ll1&tag=pw016-20&linkId=7d6d68e9118e270b03a3cb13e2ccff29

But seem expensive and overly complicated.

What are some good products or ideas?


Edited by - terracore on 04/12/2018 17:42:03

DanielP
Punatic

1983 Posts

Posted - 04/05/2018 :  17:17:57  Show Profile  Reply with Quote
High capacity battery charger
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randomq
Punatic

USA
1233 Posts

Posted - 04/05/2018 :  18:02:35  Show Profile  Reply with Quote
For a fast and vigorous charge you want a charger that can put out between C/10 and C/6 Amps, where C = the Amp hours of your battery bank.

ex: 400 Ah battery bank => 40-60 Amp charger

Aside from high amperage chargers and charge-inverters, some people also use cheap DC arc welders!

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terracore
Punatic

5098 Posts

Posted - 04/05/2018 :  18:33:05  Show Profile  Reply with Quote
Thanks for the suggestions.

I've been looking for programmable chargers- for example one that kicks on at 11 volts (or whatever) and cuts out at a programmable setting. I don't want to waste electricity knowing the clouds will pass. I haven't found such a charger yet.
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terracore
Punatic

5098 Posts

Posted - 04/07/2018 :  16:06:53  Show Profile  Reply with Quote
I called Samlex and spoke to one of their engineers, this is the product they say I really need. It has an "offline" mode that prioritizes PV power over grid power (sort of the opposite of what most similar products do).

But... the price... ouch:

https://www.amazon.com/Samlex-America-EVO-3012-Evolution-Inverter/dp/B00VIVMIKA/ref=as_li_ss_tl?ie=UTF8&qid=1523153098&sr=8-1&keywords=samlex+inverter+charger&linkCode=ll1&tag=pw016-20&linkId=74b87cd8ad509cfdf5b2c92620f431c6
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MarkP
Punatic

2062 Posts

Posted - 04/07/2018 :  17:31:35  Show Profile  Reply with Quote
Is this for an existing system? I of course use an off grid system 24/7, supplementing as needed with a generator. My brother is putting in what will be essentially a whole-house UPS although having spent money on the infrastructure he will naturally attempt to displace grid power whenever possible. What is your goal? A 3,000 watt inverter would tend to be paired with a bank of several golf cart batteries or L16s. Whenever possible it is desirable to connect them in series. That means 24, 36, or 48 volts.

I payed $1,600 for my 3,800 watt 48 volt inverter/charger.
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terracore
Punatic

5098 Posts

Posted - 04/08/2018 :  06:56:12  Show Profile  Reply with Quote
"having spent money on the infrastructure he will naturally attempt to displace grid power whenever possible"

That's basically what I'm doing. I have all the constant draws in the house running off solar for about 8 hours per day (deep freeze, solar hot water pump, UV sterilization unit, internet router, CCTV, etc, about ~400 watts. The deep freeze and solar pump only runs during those hours) while the sun is out, then a transfer switch on a timer automatically switches it back to grid. I don't really "store" any power, I just use it as it's produced. I do need to buy some real batteries and will when the budget allows. My old marine battery has exceeded it's lifespan. The "problem" is that under full sun, I have enough power to run the entire house, and sometimes I do, but it requires manually switching the power over to the other circuits not not just the constant draws currently configured, something I could avoid doing if there was something supplementing the power when the clouds come. Really its more a matter of convenience but it would also reduce my power bill.
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MarkP
Punatic

2062 Posts

Posted - 04/08/2018 :  11:06:31  Show Profile  Reply with Quote
My inverter has a/c in terminals. When it sees power on these terminals it feeds the power through plus siphons some off to charge batteries. If you were to copy my set-up you could get one of those water heater timers to turn the a/c in on at night. Use the cheap golf cart batteries since you will be recharging both day and night. On cloudy days your batteries will be more seriously depleted and you will draw more grid power at night. In SHTF situations you will already be in off-grid mode and can either conserve power to make do with solar PV recharging or you can plug into a generator.

Not saying it would be cheap to install the system I describe. You need to value having a whole-house UPS/off-grid capability to make it worthwhile.
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terracore
Punatic

5098 Posts

Posted - 04/08/2018 :  11:41:57  Show Profile  Reply with Quote
"Not saying it would be cheap to install the system I describe. You need to value having a whole-house UPS/off-grid capability to make it worthwhile."

I do, and this project started as just a way to run the deep freeze 100% on solar but turned into a hobby that can now run the entire house at times. Because I've done the whole thing piecemeal using components mostly bought on sale or discount using only my labor the payback on what I've done so far will be about 2.3 years. Maybe less if Helco increases rates. Adding a battery bank will add to that but on the other hand I might get a few more hours of partial grid freedom each day too so maybe it won't add a lot. And being ready for a SHTF scenario is priceless.
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MarkP
Punatic

2062 Posts

Posted - 04/08/2018 :  13:20:01  Show Profile  Reply with Quote
It always surprises me when someone who has built an underground bunker and stocked it with thousands of rounds of ammunition for the coming zombie apocalypse balks at an arbitrary cost issue. The appeal of most of these projects often can not be quantified purely in dollars. OTOH it is easy to lose track of costs so basic reality checks should always be done. I could have bought a lot of electricity for what I have spent on my solar system. OTOH no amount of money would buy electricity in the aftermath of a hurricane if HELCO is down.
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terracore
Punatic

5098 Posts

Posted - 04/08/2018 :  13:55:18  Show Profile  Reply with Quote
"no amount of money would buy electricity in the aftermath of a hurricane if HELCO is down"

You hit the nail on the head. The reason why I wanted off-grid refrigeration- it was the only reason I was spending ~$30/day on gas to keep the generator running after Iselle. Unless my panels blow off, if there is another incident like that I can probably get by on very little generator usage. The power went out for several hours about a week ago and we barely even noticed because all our primary electronics were running off the solar. As luck would have it, grid power was restored just as evening came. I'm typing this now on a computer juiced by solar.
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terracore
Punatic

5098 Posts

Posted - 04/12/2018 :  17:42:44  Show Profile  Reply with Quote
My system has two charge controllers. Lots of info out there about that. But what about 3 (identical) charge controllers from 3 arrays feeding one battery bank?
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kalakoa
Motormouth

11110 Posts

Posted - 04/15/2018 :  14:46:31  Show Profile  Reply with Quote
what about 3 (identical) charge controllers

Charge controllers "back off" as the batteries reach float voltage; this remains true even when there are 2 or 3 or more charge controllers "ganged together", it just works.

For "elegance", maybe adjust the float threshold so that the controllers back off gracefully, leaving one of them as the "last charger standing".

The other thing you're looking for is a "voltage controlled switch", Solar Converters has gone out of business but there are plenty of cheap Chinese versions on eBay. Get a few; use one to drive an automatic transfer switch (smarter than a timer), one to trigger the battery charger, and maybe one turned up to near float voltage so the "extra" power does something silly (fountain, ice maker, silly decorative lights, etc) when the batteries are full.

(Giving post 10K back to the community, because reasons.)
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Kapoho Joe
Punatic

USA
1934 Posts

Posted - 04/15/2018 :  19:17:52  Show Profile  Reply with Quote
Helpful & classy - way to go! Congratulations on the milestone.
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terracore
Punatic

5098 Posts

Posted - 04/16/2018 :  17:09:26  Show Profile  Reply with Quote
"(Giving post 10K back to the community, because reasons.)"

Much appreciation.
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