solar battery advice needed.

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jimmyhackers   100 W

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solar battery advice needed.

Post by jimmyhackers » May 03 2018 4:38am

Hello. My father currently has a sunnyboy sb 2500 solar inverter teamed with 10x 215watt HV PV panels.

we get paid for the energy we produce whether we use it or not so a battery system seemed like a viable option for when we overproduce to store it up and use it when the panels aren't producing anymore.

he recently was "sold" a battery pack system.....but when the electrician came to fit it he advised us not to bother (as the 5kwh of batteries would never get filled etc)......so we haven't and no money has been spent (it was going to cost an extortionate 4500 pounds :S).

as well as advising us on not to go through with the installation, he said we'd be best off getting a newer inverter to replace the old one and not bothering with the battery system.

after this debacle......my father has once again turned to me to see what i can do instead, and hopefully for a lot cheaper.

can someone point me to a better inverter, or inverter/battery system.

thanks in advance
jim
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flippy   10 kW

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Re: solar battery advice needed.

Post by flippy » May 03 2018 8:44am

is the sunnyboy battery-capable or does it have a off-grid mode?
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Re: solar battery advice needed.

Post by billvon » May 03 2018 11:14am

jimmyhackers wrote:
May 03 2018 4:38am
can someone point me to a better inverter, or inverter/battery system.
You are not going to find a battery system that is cost effective (i.e. saves you more than it costs) unless you live in Hawaii, or unless you are on a real time pricing program (unlikely.)
--bill von

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Re: solar battery advice needed.

Post by jimmyhackers » May 04 2018 11:56am

thanks for the info. looks like i need to provide a little more info

the sunny boy is not battery capable. its only version of off grid mode is to stop feeding power to the grid if the grid is shut off.

we are also not on a real time pricing program. however....as i said we get paid "reimbursed" per kw produced regardless of whether we use it or we dont and it just feeds the grid.

i pretty much use two computers to mine crypto currency 24/7 so the houses constant usage is around 700-900 watts of total power used constantly.

my panels can produce anywhere upto 2kw of power per hour. meaning at these times im getting power im not using. it also means if i could store that energy and use it when its dark or the panels arn't working id save some money.

i have a rather large amount of agm lead acids ive collected (over a kilowatthour of storage) so i was looking to try and use them.

also my current inverters working input voltage range is 211-480v meaning some times (every day) my panels are still at 200volts or less and are not being used.

as far as i can see...i kinda have two options. find a new more efficient better hybrid inverter that works with my batteries and panels with a wider input voltage range.

or i can get a box of tricks battery inverter to add to my current one that will work with my batteries.

i juts cant find the right box of tricks for the right price (under 500 quid)
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Re: solar battery advice needed.

Post by billvon » May 04 2018 12:23pm

jimmyhackers wrote:
May 04 2018 11:56am
thanks for the info. looks like i need to provide a little more info

the sunny boy is not battery capable. its only version of off grid mode is to stop feeding power to the grid if the grid is shut off.

we are also not on a real time pricing program. however....as i said we get paid "reimbursed" per kw produced regardless of whether we use it or we dont and it just feeds the grid.

i pretty much use two computers to mine crypto currency 24/7 so the houses constant usage is around 700-900 watts of total power used constantly.

my panels can produce anywhere upto 2kw of power per hour. meaning at these times im getting power im not using. it also means if i could store that energy and use it when its dark or the panels arn't working id save some money.

i have a rather large amount of agm lead acids ive collected (over a kilowatthour of storage) so i was looking to try and use them.

also my current inverters working input voltage range is 211-480v meaning some times (every day) my panels are still at 200volts or less and are not being used.

as far as i can see...i kinda have two options. find a new more efficient better hybrid inverter that works with my batteries and panels with a wider input voltage range.

or i can get a box of tricks battery inverter to add to my current one that will work with my batteries.

i juts cant find the right box of tricks for the right price (under 500 quid)
OK so some notes:

-The grid tie inverter is going to be your most economical option (i.e. the most energy out, the most payback etc.) If you mess with that you are going to lose money. You will not save money by using the batteries no matter what. But as long as you are OK with that:

-You won't get any energy from the solar array once it goes below 200 volts. At that point there's _maybe_ a few watts available, for a short time (i.e. sunset and sunrise.)

-There are some commercial HV solutions available, but they are all pretty pricey. (The Tristar MPPT 600V, the Schneider XW 80-600)

-If the voltage never goes above about 370 volts you can use one of the many AC to DC supplies that will convert 370VDC to 12/24/48VDC. However these need to be carefully managed to prevent collapse since they are not designed for this, and there's a significant amount of danger when you mess with HVDC.

-You can rewire the array to get the voltage to below about 100 volts. At that point cheaper MPPT controllers will work with it.

-You can build your own array to play with; solar is currently pretty cheap (below 50 cents a watt.) This is what I'd recommend.

-If you want to do "power arbitrage" (i.e. buy low sell high) then consider inverters like the Outback GXFV3648. They will do that.
--bill von

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jimmyhackers   100 W

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Re: solar battery advice needed.

Post by jimmyhackers » May 04 2018 1:15pm

thanks for the help (and bearing with me) i really appreciate it.

i get what you are saying about cost effectiveness not being really viable. everything to make it happen that's "plug n play" promise a ROI of over 2 years, probably closer to 5 or 10.

however i still disagree slightly that if im paying for all the energy i use, and getting reimbursed for the energy i produce wether i use it or not.
that there is still a gain to be had somewhere within it. between 1 - 5kwh per day.

if i can get a bit more heath robinson Im sure i could harness at least some of it for a reasonable price.

NEW IDEA: most of my houses load is focused on my two mining pcs. about 350watts a peice.

what if i heath robinson a computer UPS (i have one going spare) with my battery bank so it could feasibly run it for a lot longer than intended on battery power.

and then figure out the annoyingly complicated side of monitoring/controlling it all.
id need something to notice im overproducing and to turn on a battery charger.
id need something (possibly just a rewire of UPS) to switch between powering a single pc from the mains or through the battery bank UPS depending on whether battery was available..
and probably a lot more :S

ill have a go at adding the bigger battery to the ups soon and see how long.....i can run my pc on it for, see the systems viability.

thanks aging for your help/input
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Re: solar battery advice needed.

Post by Hwy89 » May 04 2018 2:46pm

The main drawback with a grid tied system such as yours is that if the grid goes down you have no power even if the sun is shining.
If I were you and had access to lots of lead acid batteries I would tie them all together and make a large 12V battery bank. Charge the bank with an automotive smart charger plugged into the house when the sun is shining. Purchase an ordinary 12V inverter and run what ever loads through an extension cord. Don't mess with the house wiring or try to modify that SunnyBoy inverter. You won't likely miss the power used to charge the battery bank and will be able to keep some lights on, the ice cream frozen and your computer running while your neighbors are sitting in the dark.

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Re: solar battery advice needed.

Post by billvon » May 04 2018 3:11pm

jimmyhackers wrote:
May 04 2018 1:15pm
i get what you are saying about cost effectiveness not being really viable. everything to make it happen that's "plug n play" promise a ROI of over 2 years, probably closer to 5 or 10.
That's true for solar - ROI is 10-20 years in most places.

It is NOT true for battery storage systems. The constant battery replacements cost more than the energy stored/saved. (As I mentioned, Hawaii is an exception because its power prices are insane.)
NEW IDEA: most of my houses load is focused on my two mining pcs. about 350watts a peice.
what if i heath robinson a computer UPS (i have one going spare) with my battery bank so it could feasibly run it for a lot longer than intended on battery power.
Sure, you can do that. UPS batteries are good for about 100 cycles so you could get about three months out of a system like that. If you are really going to try that, I'd recommend:

1) replacing the computer's AC power supply with a DC supply. Might be easy, might be hard. 12V PC power supplies are available.
2) getting a LiFePO4 12V battery. They are more expensive but last thousands of cycles so they are cheaper in the long run.
3) getting a charger that will charge the system if the batteries get too low - both to prevent crashes and to preserve the batteries.

Option 3) could be as easy as a charger set to a lower than normal voltage, and as complex as a comparator with a relay and timer attached.

(Again, this will cost more than just doing grid tie, but if would be a fun project for you . . . .)
--bill von

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flippy   10 kW

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Re: solar battery advice needed.

Post by flippy » May 04 2018 5:21pm

test setup built with a 48V inverter:

Image

with the proper switching you can have this running a LOT of stuff for a very long time and is pretty cheap considering. i am building a much bigger one for a factory.
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jimmyhackers   100 W

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Re: solar battery advice needed.

Post by jimmyhackers » May 04 2018 10:31pm

i dont really have to worry about grid out situations in my area of the uk..... they happen like once or twice a year and last an hour maximum.

if they are planned they are usually done at night and again don't last very long, so at least im not really gonna miss out much of that solar power.

with my ups idea if that rare event does happen, i could still be pc mining and earning them peas :)

its possible ups batteries may only last 100 cycles due to their size compared to load, meaning the peukert effect takes hold and ruins the battery before its time. a 500watt ups has like a 10ah battery in it.....im pretty sure itll be overdrawing current.

making its bank larger in ah may reduce the wear on the lead acid batteries, making for more cycles.
i do have a rather large amount of lithium 18650 cells still left over from my ebikes so that would be an option if i manage to kill all my lead acids.

the hard part is the smart monitoring/switching of it all.....if i cant do that properly i dont think the idea will have the efficiency required and im finding it hard to figure out how to do it all.

i need something to monitor the power produced by solar and the power used by the house. which then decides its a good idea to switch on a charger and start charging the batteries as excess power is produced. i think this would need as you said, some sort of comparator and relay. it would be nice if the charger could change the wattage of its charge rate dependent on the excess wattage produced, but i think implementing this would be very complicated, and most likely inaccessable to me.

i then need the ups to switch on when the solar input is gone at night and run until the batteries are low and then switch back to mains. then wait until the next days excess power. i somehow need to get the ups to do this.....and disable its inbuilt charging circuit but not its battery cutoff voltage protection. again, this is very complicated to implement.

im racking my brains but only getting brain farts about this atm :P

that box looks very impressive btw flippy, me likey. you must know your stuff, if you fancy tackling this problem i have and draw up a circuit diagram etc for me if you can solve it id be very grateful.

thanks again for all the help
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Re: solar battery advice needed.

Post by Maxim » May 06 2018 12:31pm

McCune Solar Works in Albuquerque NM is producing a LiFePO4 48 volt 10 KWh battery system, and will soon produce an inverter that is both on and off grid. mccunesolarworks.com

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Re: solar battery advice needed.

Post by Hillhater » May 06 2018 5:38pm

flippy wrote:
May 04 2018 5:21pm
test setup built with a 48V inverter:

Image

with the proper switching you can have this running a LOT of stuff for a very long time and is pretty cheap considering. i am building a much bigger one for a factory.
Can you be more specific than.... "running a LOT of stuff for a very long time"....??
kWhs, maybe ?
Costs ? ..components List ?
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flippy   10 kW

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Re: solar battery advice needed.

Post by flippy » May 06 2018 7:03pm

Hillhater wrote:
May 06 2018 5:38pm
Can you be more specific than.... "running a LOT of stuff for a very long time"....??
kWhs, maybe ?
Costs ? ..components List ?
this is just for testing and just messing around. it has been torn down already.
cells are recouped from old worn out e scooter battery packs.
capacity is limited only by size and cost if you were to use proper cells.
its made for 48V nominal. this powers the aliexpress 48V 220V ac inverter. voltage range is basically the same a lead at that point so you can use the entire voltage range of the lipo at 48V without the inverter going apeshit over the voltage range lipo has.
the blue thing is the charger from a scooter. it can deliver about 1.5kW to the battery.
this pack had about 5kWh or so. it were shit cells. with 3400mAh it could be well over 10kWh at this size.
it can run a fryer for about 6~7 hours i think depending on howmany fries you cook.

i am trying to get more jobs with these kinds of setups. mostly more into mobile power. having a big bank to run heavy equipment or even food trucks or whatever and us a separate alternator to charge it while driving to and from locations can save money as municipal power is REALLY expensive and tethers you to specific locations. charging on the move or back at base is cheaper and simpler then messing with local goverments or lugging generators with you.
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jimmyhackers   100 W

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Re: solar battery advice needed.

Post by jimmyhackers » May 07 2018 12:54pm

ive found and half fixed my ups...

its a compaq 1500h. 1500va or 960watts. its old but does pretty good power tbh

it has two 22ah lead acid batteries in it, in series making 24v, and roughly 0.5kwh of storage.

i found out its issue but im a bit stumped as to why its happening.....

for some reason or another it appears to run one battery down far lower than the other (positive terminal battery).
i thought it was just one duff battery out of the original pair.....but after installing two of my new identical batteries to test, the same thing happened again. i re-charged them identically again but swapped the order and the other cell in the same position did it again.

not sure why, although i do remember a lot of times when dismantling dead batteries... that the "positive end cells" were a lot more likely to be the dead cells, while others in the same battery were just fine.

besides from damaging my batteries it wont be harnessing all the potential power in the batteries. i need a 12/24 bms balancer or something
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jimmyhackers   100 W

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Re: solar battery advice needed.

Post by jimmyhackers » May 08 2018 10:36am

https://www.ebay.co.uk/itm/500-600-1000 ... qhYeSnuY4Q

i wish someone would of linked me to something like this earlier.. :P

this is exactly what i need for exactly the sort of price id like to pay.

i can plug one of these into my grid with a timer, so it turns on at night,feeding the house.....and charge the batteries up on a timer, so they charge the batteries fully during daylight/production hours....

here's a crude drawing in paint. red=blue = dc, orange = 240v.

Image

i could eventually replace "timer2" with a light intensity sensing switch "arrangement" instead of a timer to get more efficiency.
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Re: solar battery advice needed.

Post by billvon » May 08 2018 11:03am

jimmyhackers wrote:
May 08 2018 10:36am
https://www.ebay.co.uk/itm/500-600-1000 ... qhYeSnuY4Q
i wish someone would of linked me to something like this earlier.. :P
Tapping the wire coming out of the panel is no different than putting that entire system on a different breaker.

I strongly recommend you do NOT use an inverter like the one above. Several reasons:

1) The battery won't be at a voltage the inverter will like, and those inverters have terrible MPPT tracking algorithms. So you will get 100 watts out of your 500 watt inverter. (I've tried it)

2) The inverter is NOT current protected at its input. So if there is a fault the inverter will catch fire almost immediately.

3) Those inverters are not certified to UL 1741 - so they may not protect utility workers from injury or death when working on power lines.

If you want to do this, get an inverter/charger rated for that use, like the GVFX series from Outback. That is designed to do that - charge a battery and then sell the power back.

Or get on the list to get one of these:

http://orison.energy/products/
--bill von

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jimmyhackers   100 W

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Re: solar battery advice needed.

Post by jimmyhackers » May 08 2018 2:24pm

thanks for your concern.

i was tbh going to wire it into its own breaker....i just didn't do my drawing properly.

what battery voltage and ah size did you connect to yours? i noticed the input voltage range for them is 24-48v. this could of effected its efficiency/power output.

it also says it has islanding protetction....not sure its up to UL 1741 spec though.
the add says "Protection: Islanding; short-circuit; converse connection; low voltage; over voltage; over temperature protection"
but they could be lying.

i was looking into the peukert effect again and running the numbers..... a 1000w inverter will draw 41-42amps from a 24v battery at full power. A 22ah battery will give 22ah at a rate of 1amp every hour for 22 hours.

however if you draw any more than 1ah per hour.....like a 1000w inverter might...you substantially reduce the capacity inside a lead acid battery.

even a 500w inverter will want over 20 amps. id still need way more batteries than i have to reduce this peukert effect. i think i need to start building my lipo bank instead.
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Re: solar battery advice needed.

Post by billvon » May 08 2018 3:39pm

jimmyhackers wrote:
May 08 2018 2:24pm
what battery voltage and ah size did you connect to yours? i noticed the input voltage range for them is 24-48v. this could of effected its efficiency/power output.
It was a 12V inverter (10-30V) running off a 14 volt system. (Very small battery but DC/DC kept it at 14V.)
it also says it has islanding protetction....not sure its up to UL 1741 spec though.
That's the rub. "Meeting UL 1741" means it works and has been tested.
the add says "Protection: Islanding; short-circuit; converse connection; low voltage; over voltage; over temperature protection"
but they could be lying.
That's on the output. The input assumes a solar panel. Solar panels current-limit themselves so there's little risk when used with this inverter.
i was looking into the peukert effect again and running the numbers..... a 1000w inverter will draw 41-42amps from a 24v battery at full power. A 22ah battery will give 22ah at a rate of 1amp every hour for 22 hours.
I think you will see far less power than that.
--bill von

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Re: solar battery advice needed.

Post by flippy » May 09 2018 5:43am

billvon wrote:
May 08 2018 3:39pm
That's on the output. The input assumes a solar panel. Solar panels current-limit themselves so there's little risk when used with this inverter.
you are reading it wrong i think.

the problem with "island" capable inverters like this is that they will keep sending power on the main grid when the grid is off. so line workers will still get shocked when they work on lines because your inverter is still dumping power onto the grid.

what you can do is run a regular MPPT charger for 48V batteries and charge a lipo pack with it. lipo is bascially the same voltage if you use a normal 14S pack you a right on the voltage range of regular lithium.
grab a 48V inverter from aliexpress: https://www.aliexpress.com/store/produc ... 20376vuLwu
only thing you need is a decent MPPT charger rated for 48V and your panel voltage.

with this you can run a entire fuse in your fusebox at full current. when the battery drains you can switch on reguar mains if you add some cheap relays and stuff. but it needs to be built in such a mannter that inverter power cannot enter the main grid.
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jimmyhackers   100 W

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Re: solar battery advice needed.

Post by jimmyhackers » May 09 2018 7:33am

im pretty sure the inverter i posted although worded badly has islanding protection...

meaning it requires a mains input to work. meaning if the grid did go down....it should turn off.

although....im not sure how it would work in conjunction with my existing solar inverters islanding protection....

if both were on and producing power they could trick each other into thinking the grid is still live and keep producing.
technically this shouldn't happen for me as the battery inverter wont/shouldnt be on in daylight hours.

it does make me wonder though if two houses were next to each other with solar panels and grid tie inverters, couldn't a similar thing happen?

im guessing as the grid goes down....there are so many loads on it from so many other houses, any solar system wouldn't cope/power it all and this would trigger the islanding protection also. This could change though when/if a vast majority of people on the same grid adopt solar grid-tie feeds.

i could buy one and run some of my own tests on it....although from the looks of some youtube videos they seem to work fine.

it could be your inverter was running at its lowest power setting as it was close to its lowest dc input power, so it may of run better off of 24v. you also would/could of been losing efficiency and maxmum amps available with you dc-dc converter. 500w at 14v will need 35amps.
that's a lot to ask of a little battery. a 22Ah lead acid battery will give out about 5-10Ah at that kind of rate before its flat.
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Re: solar battery advice needed.

Post by billvon » May 09 2018 11:11am

flippy wrote:
May 09 2018 5:43am
you are reading it wrong i think.

the problem with "island" capable inverters like this is that they will keep sending power on the main grid when the grid is off. so line workers will still get shocked when they work on lines because your inverter is still dumping power onto the grid.
Right, that's what I said.

But the part you quoted speaks to a different issue. Solar panels are current limited. If you short their output, they will not deliver more than their rated short circuit current. So shorting the PV input to protect the inverter is a valid way to do it. (Additionaly, that means that if the most common failure at the input is that devices fail closed, there's no need for separate protection against that - that is not a dangerous condition for a solar panel input.)

A battery does not have a limit to the current it can deliver, and often the line between the inverter and the battery is not fused in simple systems. If the inverter shorts the input, the battery will deliver hundreds to thousands of amps and destroy it - and likely start a fire. (Current depends on type and protection of batteries of course.)
what you can do is run a regular MPPT charger for 48V batteries and charge a lipo pack with it. lipo is bascially the same voltage if you use a normal 14S pack you a right on the voltage range of regular lithium.
Yes, that would be a more direct way to do it. However, most grid tie systems operate between 300 and 600 volts, and the MPPT you will need to work at those voltages will be very pricey indeed. (>$1000)
grab a 48V inverter from aliexpress: https://www.aliexpress.com/store/produc ... 20376vuLwu
only thing you need is a decent MPPT charger rated for 48V and your panel voltage.
OK so now you are looking at supplying all your loads from a lipo pack. That can work - but is going to be expensive and dangerous. (A 10kWhr pack going up will destroy your home in short order.)

Again, if you want to do this, a much smarter approach is to:

1) get an inverter that is designed to do this. The mode you will want is called HBX (high battery transfer.) The inverter handles everything including charging the battery when needed and switching over the AC supply from inverter to grid.

2) get a battery that is safe to use in a home. If you are going to roll your own, LiFePO4 is relatively safe (and cheap.)

3) reconfigure the solar array to provide a voltage (~100V) that cheap MPPT converters can use. Then get a good MPPT converter.
with this you can run a entire fuse in your fusebox at full current. when the battery drains you can switch on reguar mains if you add some cheap relays and stuff. but it needs to be built in such a mannter that inverter power cannot enter the main grid.
If it's going to run your home I would avoid "cheap relays and stuff." If your house catches fire you could lose everything - and your insurance company will be sure to notice your "cheap relays and stuff" during the investigation.

Note that we already have a story here from a guy who lost his garage to a battery fire - and we are talking about a much larger (and harder to move outside) battery.
--bill von

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Re: solar battery advice needed.

Post by billvon » May 09 2018 11:15am

jimmyhackers wrote:
May 09 2018 7:33am
im pretty sure the inverter i posted although worded badly has islanding protection...

meaning it requires a mains input to work. meaning if the grid did go down....it should turn off.

although....im not sure how it would work in conjunction with my existing solar inverters islanding protection....

if both were on and producing power they could trick each other into thinking the grid is still live and keep producing.
technically this shouldn't happen for me as the battery inverter wont/shouldnt be on in daylight hours.

it does make me wonder though if two houses were next to each other with solar panels and grid tie inverters, couldn't a similar thing happen?
This is one of the many ways that several inverters can "island" and run a portion of the grid, putting utility workers at risk. Another risk is that largish motors are running somewhere on the grid nearby; these stabilize the grid and can fool an inverter into thinking that the grid is still there.

Inverters certified to UL 1741 have been tested with the above conditions (and several others) to ensure they will not remain on-line.
it could be your inverter was running at its lowest power setting as it was close to its lowest dc input power, so it may of run better off of 24v. you also would/could of been losing efficiency and maxmum amps available with you dc-dc converter. 500w at 14v will need 35amps.
that's a lot to ask of a little battery. a 22Ah lead acid battery will give out about 5-10Ah at that kind of rate before its flat.
Yep. But it was being fed by a 70 amp DC/DC. The battery was only to provide a lower impedance to the inverter.
--bill von

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jimmyhackers   100 W

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Re: solar battery advice needed.

Post by jimmyhackers » May 25 2018 8:00pm

ive found a more amicable solution :P

im just going to increase my mining power consumption so theres no spare energy.
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Joined: Apr 01 2010 12:23pm
Location: Northeast of Pittsburgh, PA USA

Re: solar battery advice needed.

Post by unklegrumpknee » Aug 12 2018 10:52am

jimmy

brilliant idea about upping mining.
Or diversify on a third computer.

craneplaneguy   10 kW

10 kW
Posts: 779
Joined: Nov 27 2015 9:15am
Location: S.E. Idaho USA

Re: solar battery advice needed.

Post by craneplaneguy » Aug 13 2018 3:18pm

After being off grid for 28 years, and now grid tied for the last 13 (with a credit as of last month with my utility of a bit over 9,000 KWH) you could not GIVE me a set of batteries. IF I was worried about power outages (rare, but they do happen where I'm at, maybe 3-4 hours total annually), I'd run a generator if I happened to be at home and needed power.

Batteries blow, at least giant lead acid home style banks, they wear out, take up room, can be dangerous, and are not all that efficient as per putting a watt out and getting it back. Sealed types are much better but twice the price. I am lucky to have my utility as my battery, stored off site, no maintenance, and of infinite size and it operates at 100% efficiency! All for a basic hookup fee of $5.00 a month!

The batteries in my ebikes now, I love those suckers.....

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