Cheap inverter

junglejoe39

Need to get an inverter. Am looking at Powerjack 3000w pure sine LF 24v input. Any experience or advice

westbranch

read here, not good  http://forum.solar-electric.com/discussion/comment/305302#Comment_305302

junglejoe39

some seem to have good luck with them Plus I intend to stay under 1500w peak ?

zoneblue

There is no such thing as a cheap inverter. Its a contradiction in terms. Those that try, inevitably find that out.
Another inverter myths, bigger is better, "ill only run it at 1500W". Doesnt account for the tare, such inverters can often draw 80W doing nothing. Ouch.. Doesnt account for that they probably designed the 3000W unit as a 2000W unit and added a bigger fan, and some bodges.

Stick around, do some reading here. Your system will be the better for it.

Photowhit

What type of system do you have?

Are you already committed to 24 volt? Could you reconfigure to a 12 volt system? There are some 12v inverter that are less expensive...

junglejoe39

Several people have told me 24v system would be better more efficient ?

bill von novak

junglejoe39 said:

Several people have told me 24v system would be better more efficient ?

At 1500 watts, 24 volts is a good choice.  That's 62 amps, rather than 124 amps at 12 volts.

Photowhit

junglejoe39 said:

Several people have told me 24v system would be better more efficient ?

People are people they'll tell you anything, unless you ask for information, like "What kind of system do you have?"

So let me tell you about your system, that I know nothing about, other than you will stay under 1500watts peak.

Since you can mount the inverter 2 feet from your battery bank, and you have minimal needs of half a KW a day, but you like your popcorn in your fancy microwave. You could purchase a 2000 watt inverter from Xantrex for @$350. A Samlex 24 volt 2000 watt would run nearly 2 times as much and is about as low a priced inverter that I could recommend.

12 volt inverters aren't simple to use if you have a minimal battery bank. but a short connection with thick wire can solve most of the problems.

People do always seem to want a big inverter, I've lived with in the capacity of a 1800 watt inverter (yes, at 24 volts) for the last 10 years or so... Including running a hot water heater, toaster oven, microwave, clothes washer...

So some advice, figure out what you want to do. even 1500 watts peak tells us next to nothing. There is a huge bank of experience here that can help you design a system to fit your needs.

zoneblue

The Prosines seem to go for about 500 on the used market.
http://www.ebay.com/sch/i.html?_nkw=prosine+inverter

Seems like a reasonable choice for a newbie. Again, cheap chinese inverters are a liability, both financially and froma  safety perspective. Beware.

Photowhit

I haven't seen the 1800 watt version going for less than $6-700 too often, though I have purchased a 5 year old unused one for @$400 shipped off eBay several years ago. I don't mind suggesting looking for a used inverter. You might also search for Iris Quiet Power inverter. The 1800 watt version of Prosine is/was sold to the military under those specs. As usual be careful, you could get one full of sand from Iraq or one required to be replaced every so often out of an armory!

Not a recommendation, this one looks to be well used, but this is what the 'Quiet Power' version looks like;

http://www.ebay.com/itm/1800-Watt-24-Volt-Power-Inverter-M998-M1078-Hmmwv-/121885564882?hash=item1c60f21fd2:g:W-EAAOSwXshWs73Q

All Iris Quiet Power inverters will be 24 volt, for military vehicles. Prosine's will need to check specs! They come in 12-24 volt versions, 1000 and 1800watt versions in 120, 230 volt output versions. There are also 2000, 2500 and 3000 watt version that have chagrers built in, I have no experience with these.

junglejoe39

Ok sorry for not giving more info + Im learning as I go. Have 1520 watts panels. 3 arrays of 3 diff. kinds of panels. 4 130w-4 100w- 4 150w .Was running the cheap plug in grid tie inverters that served me very well. Got letter from DTE they are installing smart meter. So now I really cut back. Turned master suite into tiny home. Tellocommunications Charter cable tv + internet + VOIP phone has constant 125w draw 225w when 32 in. led tv is on. Also want to run 850w heat pump when needed or full size fridge when heat pump is not needed. Will stay connected to grid and only use grid power for well pump and maybe microwave or when needed Last night I bought a Cotek 24v to 120v 1500w 3000w peak pure sine inverter. Says mounted never used 160$ + 20$ shipping. Battery bank will start with 2-35ah 12v in series and add 2 a month till I have enuf.

BB.

I would suggest that a bunch of 12 volt 35 AH batteries in series/parallel is not going to serve you well... Will be lots of wiring, cells to check, and not great life or reliability. I would recommend that you hold off on batteries until you get enough money saved to buy a bank of properly sized batteries.

For example, a solar array should provide 5% to 13% rate of charge for your battery bank. 10% or higher rate of charge if you are off grid/trying to use the bank 9+ months a year (full time).

• 1,520 Watt array * 0.77 panel+charger derating * 1/29 volts charging * 1/0.05 rate of of charge = 807 AH @ 29 volt largest bank
• 1,520 Watt array * 0.77 panel+charger derating * 1/29 volts charging * 1/0.10 rate of of charge = 403 AH @ 24 volt nominal bank
  
• 1,520 Watt array * 0.77 panel+charger derating * 1/29 volts charging * 1/0.05 rate of of charge = 310 AH @ 24 volt minimum recommended battery bank
  

As a starting bank--I would suggest you look at 6 volt @ ~200 AH "golf cart" type deep cycle batteries. They are relatively cheap and rugged.

A fixed solar array for Saginaw Mi would give you roughly:

http://solarelectricityhandbook.com/solar-irradiance.html

Saginaw
Average Solar Insolation figures

Measured in kWh/m2/day onto a solar panel set at a 47° angle:
(For best year-round performance)

Jan	Feb	Mar	Apr	May	Jun
2.89	3.56	4.22	4.63	4.87	5.17
Jul	Aug	Sep	Oct	Nov	Dec
5.33	4.91	4.63	3.70	2.61	2.56

Assuming we toss the bottom three months (use generator/grid to back up for bad weather):

• 1,520 Watt array * 0.52 typical off grid system * 3.56 Hours of average Feb sun = 2,814 WH = 2.8 kWH per day = 84 kWH per (30 day) Month
  

Anyway--That is roughly what I would be suggesting for your system and how much power it would produce (February "break even" month). Enough power to run a modern energy star refrigerator plus a few other small loads a day.

You can use a Kill-a-Watt type meter to measure your AC loads and see what you actually consume per average day.

-Bill

junglejoe39

I am aware the larger higher ah batteries work better. I just think Im willing to settle for less performance for way less weight

BB.

More or less, Lead Acid storage capacity (AH*Voltage=Watt*Hours) is based on weight of lead. A 35 AH battery is about 1/10th the weight of a 350 AH battery of the same voltage.

With AGM and GEL batteries, they have higher peak surge current (and automotive starting batteries)--But overall amp*hour of storage is about the same (WH per pound).

Even if the 35 AH batteries are free--It is almost not worth it for the issues of making a clean electrical installation and the maintenance (if not sealed batteries, you are looking at checking electrolyte levels of 120 or more cells each month). Plus cells/batteries fail -- So you have diagnose/find the failures before other bad things happen.

Wiring, normally you would fuse/breaker each parallel string--Especially if massively paralleled (3 or more parallel strings). for safety. Here is a link that explains how to wire up parallel strings:

http://www.smartgauge.co.uk/batt_con.html

-Bill

westbranch

To solve the weight issue a change of storage type is needed, my AGMs weigh 1800 # per battery!
LiFePO4 is the ,current, best option for me to change to if I need to change... because of weight and other charge/discharge parameters...

junglejoe39

Wow thanks for the link just what I needed. My batteries will be sealed. Maybe someone here can answer another ? I have. If I connect the charger and inverter leads to the same points is it possible that when the inverter has a lower draw than the charger is putting out that the power will go directly from charger to inverter without incurring the losses associated with charging the batteries and drawing the power out of the batteries. Also Im seriously thinking about 2 banks smaller one for smaller loads and bigger for bigger loads ? Thanks for all of your help!

zoneblue

junglejoe39 said:

Have 1520 watts panels. 3 arrays of 3 diff. kinds of panels. ... Will stay connected to grid ... Last night I bought a Cotek 24v to 120v 1500w 3000w peak pure sine inverter.... Battery bank will start with 2-35ah 12v in series and add 2 a month till I have enuf.

Sorry but the bad news is that for off grid style of systems (even if you have a grid assist charging), you need a reaonably large battery. As bill showed 400Ah, in your case. The reasons for this are simple.
- you need enough Ah to fully accept teh peak charge current from teh array (0.1C).
- you need enough surge capacity to support the radical power needs of the inverter (0.25C)
- thus it doesnt matter how much backup storage you think you need, it is in essence a side effect of the above two criteria.

Thus 35Ah batterys have no place in a system like this.  As WB said if you are wanting the smallest battery try LFP, they can do much higher charge and discharge rates. But they are more expenisve. Please be careful, whatver you do. Batterys of any size are hazardous.

junglejoe39

Ok may be time for a little more honesty. Im on disability and therefore poor. I started this to save $ and it worked awesome with the grid tie. I was somewhat wasteful b4 with elec.and was on budget plan (pay same every month) 125$ a month. I got tight fisted with everything food smokes booze and elec. and bought all the solar,wires,inverters. Elec. bill went to 85$ and I was still overpaying. Bill would be 71$ this month but got off plan today and they are sending me a check for 361$ and change next bill will be under 70$. Im still being cheap and what I am looking to do is get as much use out of my solar with as little investment as possible. I may even use my grid tie inverters off my battery bank to supplement the dryer at peak input times. Why I asked about the inverter and charger cables being together. Im not really looking for storage just as a buffer to supply as much of my homes consumption as possible and keep my batteries golden. After dark Ill go back to grid power. Im prob. headed into uncharted territory. Thanks for the help

BB.

For heating, if you have the room (on your own property with lots of south facing direct sun available)--Solar heating can be done even in climates with snow on the ground:

interesting project for a solar heated shed
low tech home made heating system.

But for most people, should review conservation possibilities first. Insulation (lots of attic insulation), air leaks, possibly double pane windows, HVAC efficiency, energy star appliances, etc.

It is almost always cheaper to conserve vs generate power/electricity.

You can use a Kill-a-Watt meter to look at the plug in appliances:

http://www.solar-electric.com/kiacpomome.html

And a whole house monitor for hardwired equipment (240 VAC dryer, stove, water heater, HVAC, etc.):

http://theenergydetective.com/

Any "reasonably priced" smaller (say less than $10,000-$20,000) is going to generate closer to $15 worth of electricity vs $70 to $200 power bills... For exmaple, if you pay $0.15 per kWH, and use 3.3 kWH per day (very possible for a highly efficient off grid home with near-normal electrical life):

• 3.3 kWH per day * 30 days per month = 100 kWH per month
• 100 kWH per month * $0.15 per kWH = $15.00 per month (plus $XX utility connection fee per month)

In some cases, the minimum connection fee may be $40 to $96 per month (before any kWH power charges)--But for many of us with $5-$10 per month connection fees, it is hard to beat the cost of utility power.

However, if you have a utility has a good solar power Net Metered power plan, it is possible to generate power at $0.15 per kWH or less. And in my case, I get paid $0.27 per kWH on summer afternoons (I do not use much summer afternoon power, most of it goes to the utility.

GT Solar can save money--But I would still highly suggest extreme conservation measures first.

-Bill

zoneblue

I hate to say it, but looks like teh power co is onto you, and you best be careful. They have algorithims to detect odd usage patterns.

Budget is not really a reason to do anything that is illegal or dangerous.  So called plug in grid GTI inverters are not scantioned by any power company that i know of, and the quality of these devices is by defintion dodgy, because all inverters certified for grid coonection undergo extensive testing. An approved grid tie connection ensures the safety of line workers, neighbours,you and your home and family, as well as your home insurance.

So for anyone else contemplating doing this... its a bad idea. OK, so having said this, thats all im going to say on teh subject, what you do is your business.

A battery inverter is a whole other beast from a GTI. The battery is the lynch pin of the system. On a long term basis its the most expensive part of the system, and its this that unfortunately makes off grid challenging to compete with teh grid on a cost basis. If you think about it this way, whats the cost of batterys in terms of per kWh?

Take for example the following battery:
- 10kWh, with a rated cycle life of 2000 25% cycles.
- that works out to = $2000/(10kWh*0.25*2000)
- or $0.40/kWh

So right there its already more than the cost of grid service. So, tricky proposition. However there are ways to alter the maths, lots and lots of homework, and being in the right place at the right time, landing on say a used forklift battery, and just occasionally people have some success with ex government /telco cells.

> may even use my grid tie inverters off my battery bank to supplement the dryer at peak input times. Why I asked about the inverter and charger cables being together.

To answer your question about the inverter and charger, its a circuit right?, whatever the inverter cant get from other sources itll draw from the battery. Whether a GTI would work at battery voltage, that depends on the product, id say its pretty unlikely.

>Im not really looking for storage just as a buffer to supply as much of my homes consumption as possible and keep my batteries golden. After dark Ill go back to grid power. Im prob. headed into uncharted territory.

That there is a problem. A DC coupled charge controller and a battery based inverter both requires a battery, and one specifically sized as above. As said, the only battery that will work well for this application is a lithium pack. But they are expensive, so your stopped there as well. With some electronics and creativity you might be able to craft an AGM system that allows the solar to power the house during the day, without exceeding the max charge rate fo the bank. (Midnite recently announced that their classic charge controller is getting battery current limiting any day).  That protects your proposed small bank from high charge rates, but teh inverter still needs to be able to draw teh current it needs. The main difficulty is managing the sun. When the sun goes away you have to what hit the transfer switch to avoid teh (realtively big) inverter sagging the (relatively small) battery. Tricky, tricky.

junglejoe39

Hay BB this whole experience woke me up. I built a couple bad ass rocket heaters that blew my mind light the stove 2 minutes later the top is 700 degrees and no smoke and I still went to solar powered heat pump.

junglejoe39

zoneblue you should know what you are talking about. There are companies right now selling solar with a grid tie as an appliance not regulated by the power co.

junglejoe39

Nice touch with the pumpkin heads. Now I am Pissed

Photowhit

junglejoe39 said:

... Last night I bought a Cotek 24v to 120v 1500w 3000w peak pure sine inverter. Says mounted never used 160$ + 20$ shipping. Battery bank will start with 2-35ah 12v in series and add 2 a month till I have enuf.

Sounds like a heck of a deal!

I didn't catch why you need the batteries inside? Bad neighborhood? Mine always live outside. This allows the use of flooded batteries, best bang for the buck in a small system would be golf cart batteries. 4 - 6volt from Sam's club or Costco around $100 a piece without exchange, $80 with(often will take car batteries) could even go with 3 - 8 volt, about the same price.

You asked about use when charging. It will use the power generated  by your array when available. So day time use is very productive. If we haven't lost you I'll go more indepth...

BB.

You can click on the Avitar to upload/change your picture (I have no idea how this new software assigns default avitars).

Regarding Grid Tied inverters... It depends on where you live, and what you buy, and what regulations you have to meet.

In my country (USA), so far, it is impossible to buy a "UL/NRTL Listed" plug in GT inverter. They just do not comply with the National Electric Code. And, in the US, the power company can pull your meter if you install "unapproved" solar power systems. And not all Utilities will allow GT Solar in the US (smaller / rural utilities many times will not). There are a lot of details about what can be done or not.

Plus, the few plug and play "import" GT inverters I have read about here and other places, are not very reliable and a few appear to overheat or worse. You can buy good quality Listed "micro GT inverters" and put your own AC plug on them--Not legal, but better built devices.

-Bill

bill von novak

Im still being cheap and what I am looking to do is get as much use out of my solar with as little investment as possible.

A lot of people want to do that - but going that route is dangerous, and people have gotten burned (literally) by trying to 'go cheap.' There are some things you can't skimp on, like wiring, protection devices and safe inverters.

I may even use my grid tie inverters off my battery bank to supplement the dryer at peak input times.

Don't do that - cheapo Chinese GT inverters will be somewhat unpredictable with a stiff voltage source instead of the more limited source supplied by a PV panel that they are expecting.

Why I asked about the inverter and charger cables being together. Im not really looking for storage just as a buffer to supply as much of my homes consumption as possible and keep my batteries golden.

1) Topology changes on the cabling won't significantly change how much power goes to which source. That is set primarily by voltage sources and impedances within the devices.

2) In general I'd recommend two wires to your battery (one on each post) going to a distribution center. Put an overcurrent device (breaker or fuse) right at the + terminal of the battery. Rate the wire above the rating of the fuse; there are plenty of tables around to figure out what gauge you need for what current. Then fuse or protect each wire coming off the distribution bus per its wire rating.

3) For multiple batteries there are, again, several drawings around showing the best way to wire them. Here's a good explanation: http://rvroadtrip.us/library/12v_system.php

zoneblue you should know what you are talking about. There are companies right now selling solar with a grid tie as an appliance not regulated by the power co.

There sure are. And those companies are quite happy to take your money and deliver you a product you can't legally use.

junglejoe39

Oops sorry little too much whiskey last night. Enjoying a little of my 361$ windfall. OK you guys convinced me. Gonna join sams  and get 4 6v 215ah. How often do I need to check the water and whats the lowest voltage I should draw it down to to be real safe. Prob will get another 4 in 6 months

junglejoe39

Oops little too much whiskey last night lol. Celebrating my 361$ windfall. OK you guys convinced me. The Sams club 6 volts are cheaper per ah

junglejoe39

Got my Cotek inverter today looks brand new

westbranch

there are several models of 1500W inverters that they make, which one did you get?

junglejoe39

Its a model SK1500-124 Id like to test it. Do you think I could do a short test with 2-12v boat batteries in series. Say westbranch are you in west branch michigan