Posts: 7,743
Threads: 686
Joined: Jun 2011
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?
Posts: 1,839
Threads: 48
Joined: May 2007
High capacity battery charger
Posts: 3,212
Threads: 109
Joined: Jun 2010
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!
Posts: 7,743
Threads: 686
Joined: Jun 2011
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.
Posts: 7,743
Threads: 686
Joined: Jun 2011
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
Posts: 2,484
Threads: 10
Joined: Feb 2008
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.
Posts: 7,743
Threads: 686
Joined: Jun 2011
"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.
Posts: 2,484
Threads: 10
Joined: Feb 2008
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.
Posts: 7,743
Threads: 686
Joined: Jun 2011
"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.
Posts: 2,484
Threads: 10
Joined: Feb 2008
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.
