Solar Power Pack Proj.

Re: Solar Power Pack Proj.

I am sorry, I thought I had already replied to your post... But I guess I did not.

Smoove69 wrote: »

I'm new to all this and I'm trying to build a small solar battery pack, in theory all sounds good but in an attempt not to fry myself or my equipment I figured it would be a good idea to get advise from the experts.

I am in the market for some stuff but let me start by saying I am trying to maintain portability so that I can watch movies, use laptop or allow kids to play ps3 while camping. On top of a few other misc. power uses.

It is really helpful if you have a good measurement of peak power (Watts) and the total power (Watt*Hours) you plan on using. For AC power, a Kill-a-Watt meter is a great too. Also very handy for conservation projects around the home. If you are going to work a lot with DC, a DC Watt*Hour/Amp*Hour meter like one of these is real useful too.

Once you know how much power you will need, then you can plan out the major component requirements (size of solar panel, battery bank, and inverter).

Solar PV power is not cheap, and the equipment is relatively large and heavy. So, you need accurate information to design the right size system for your needs.

I'm considering buying an amstron 12v 80ah sla agm battery and dropping it into a pre-made wooden box, I have a Duracell Powerpack 600 now and this has been a source of inspiration for me, apparently it has a small 12v 28ah sla battery and also has the ability to be connected via included battery/jumper cable to an external battery to increase capacity. This being said, what I would like to do is to mount two battery terminal/posts to one side of my wooden box connected to battery that are externally accessible, enabling me to do 3 things, (a) connect to duracell pack with jumper cable (b) connect to Sunforce 11240 1000-Watt Pure Sine Wave Inverter via ring connectors and (c) charge battery externally using an electrical outlet and jumper cable style connectors on a/c charger.

In general, people over estimate how much power a solar panel can supply and a under estimate their loads.

Typically, that means that they have way too little solar power (and usually too small of battery) and way to large of inverter for their needs (large inverters tend to have more losses when running small loads).

Also, starting out with a large and inexpensive MSW (Modified Square Wave) inverter to run small electronic loads can be a problem too. Small wall mount transformers and many small AC to DC power supplies for computers/DVD players, etc. tend to run hot on MSW inverters and will have a short live (sometimes they will "wear out" in in months/year or so, sometimes in minutes--It is really hard to guess--some will run just fine).

I would also like to use the Brunton 26w foldable solar array with the Brunton 12v solar charge controller/monitor and to connect them via power pole connectors which I intend to mount 2 pairs of on the opposite side of my box also externally accessible allowing me to connect charge controller to battery and I would use the 2nd power pole connector on the box for 12v dc out.

People really do like these solar panels--A neat idea... But you have to decide if they will work well for you. Using generic summer weather, most people will get a least 4 hours of "noontime sun" per day. And the system will be around 50% efficient (from solar panel power rating to 120 VAC power available for running your devices). For example:

• 52 watts * 4 hours of sun per day * 0.50 eff/derating = 104 Watt*Hours per day...

That will run a 30 watt laptop computer:

• 104 WH / 30 Watt = 3.5 hours per day

A 600 Watt inverter running at full power:

• 104 WH per day * 1/600 watts * 60 minutes/hour = 10 minutes per day

A smaller, true or pure sine wave (TSW/PSW) type inverter would be a better solution.

To do that, you will have to leave the panels laid out on a slop facing the sun for at least 6-8 hours per day... That means somebody needs to watch the panels/charger/battery to make sure that the system does not "walk away". And you cannot hike travel from point to point while charging.

If you have an RV or even a vehicle--it might be better (and less expensive) to bolt a fixed panel to the roof and keep the rest of the hardware locked inside during the day.

Then you need to look at the size of the battery bank... At the very least, the battery should be 2x your daily load. Lead Acid is used for solar--but they are very heavy. Perhaps, the new Lithium Iron Phosphate batteries would be of interest:

Lithium Iron Phosphate Batteries; LFP; LiFePO4
Portable Solar Power

My question(s) are as follows....

Does this sound do-able? and what size cable(s) should I use for (a) battery to posts (b) posts to inverter? also viewing the inverter online, I see what appears to be a ground connection on the back, do I need to ground this unit to use it? and assuming I have all the connections right, would it be possible to charge this battery from vehicle via cigarette lighter connected to power pole? if so would I need some kind of charge controller for that as well or is it regulated by vehicle charging system?

For a small battery bank, yes, you probably could charge it OK from the vehicle 12 volt outlet... It would be limited to ~10 amps (will blow the lighter fuse). And will only charge when the engine is running. Fine for driving portion of trips--but tends to be very wasteful of fuel if you idle the vehicle engine to charge the battery bank. Would be much better to use a small Honda eu1000i genset instead (things are getting more complicated and expensive).

One more thing, I assume it would be a good idea to use a fuse or fuses in this setup, what size should I use and where should I use?

Fusing protects the wiring... So, generally, you place the fuse(s) next to the main source of large amounts of current (battery bank in this case). So if you use 12 awg wire, then you need a ~20 amp fuse to protect that length of wiring.

One thing that people don't realize is that 12 volt appliances use a lot of current. At least 10x that of the equivalent in 120 VAC circuits. For example, using your 600 watt inverter as an example:

• 600 watts * 1/10.5 volt cutoff * 1/0.80 inverter eff * 1.25 fuse-wiring derating = 89 Amp Circuit/Fuse/Breaker minimum

So, you would need somewhere around 6 to 2 awg gauge cable to run this inverter from 12 volts (depending on length of wire) and roughly a 175 AH 12 volt battery to run the inverter at full power for any length of time (about 2x the size of a standard car battery).

There is a nice thread here that goes through the entire project from start to finish for another poster that wanted to build a portable emergency power supply. Pretty similar to what you asked about here:

Emergency Power

-Bill

PS: I deleted the duplicate thread--Keep all the replies in one location.

PPS: I see you beat me to it.

Re: Solar Power Pack Proj.

I can't type a long reply right now (playing on my new android phone)... It sounds like you are looking at two different systems (larger vs smaller).

In general you need to conserve power when running from solar and batteries. I would use as small as possible TSW inverter based on your loads. I don't think the 600 watt inverter will work well for what you are asking for--it seems way to large.

Take a look at the morning star sure sine 300 watt TSW inverter for your larger system. It is a very nice 12 volt unit (low power search mode and 12 volt DC inhibit).

-Bill

Re: Solar Power Pack Proj.

If I recall from the Manual--6 awg is what MorningStar recommends for the inverter...

A big issue is how long the cables will be--You have only about 1 volt of drop allowed (~11.5 volt loaded battery to 10.5 inverter cutoff). Keeping the inverter close to the battery bank will be a big help (it also will run ~600 watts for 10 minutes--so if you plan on running heavier loads, you will have to do the voltage drop calculations for those "surges").

The Sure Sine 300 watt inverter has had lots of "love" here from posters (I don't have one--so it is just specifications and other posters' experiences here). One warning--the Sure Sine does not come with any cables or AC receptacles. You have to know enough, or have a friend, to hardware the inverter to your system. Also, note that the inverter is larger/heavier than it appears in the photographs--Check the size/weight if that will be an issue for you.

The Sure Sine has a floating/isolated 120 VAC output (think transformer). There is no neutral / hot orientation.

Generally, floating output is very safe--you can touch one or the other AC output wires and not get a shock (obviously, touching both will give you a surprise).

There are a few appliances that may run better if you ground the neutral to an RV's frame (some tube type florescent lamps, some spark ignitors in stoves/heaters, and possibly some radio/audio gear). I would not ground the AC output unless you are having "issues" with an AC appliance.

Note, many TSW inverters can have a grounded neutral (along with a grounded battery bank). Many MSW inverters will smoke if the battery bank and one leg of the AC line is grounded (aka grounded neutral). Always read the instruction manual for your model of inverter before installing and grounding any inverter.

As for wiring... Use the formula I posted earlier (and recommendations from the manual). For a 600 watt rating:

• 600 watts * 1/10.5 volt cutoff * 1/0.80 inverter eff * 1.25 fuse-wiring derating = 89 Amp Circuit/Fuse/Breaker minimum

That would be 100 amp fuse/breaker/wiring circuit.

Using any old Voltage Drop calculator (this one uses "one way" wire run--AKA 10' run is 20' of round trip wiring). 71 amps peak worst case current and 6 awg wire would give ~1 volt drop:

• 15' of 6 awg wire is ~1 volt drop...

That would be the absolute maximum wire run... Add a fuse or breaker, I would probably keep the wire run to less than 7.5 feet--And only a couple feet if you can swing it. The less wire run / voltage drop, the better your inverter will run (and less power loss due to wire heating):

• 71 amps * 1 volt drop = 71 watts wasted as heat in wire run (for 600 watt load).

So, you can see why everyone uses large gauge, short cables when ever practicable. That run of wire would cost you about 10% extra losses (the inverter is around 80-85% efficient--over all efficiency of 70-75% with long wire run). These losses add up quickly.

-Bill

Re: Solar Power Pack Proj.

The SureSine 300 watt inverter has binding screws (simply strip the 6 awg / 14 awg wires and use a straight slot screw driver to tighten them down).

For larger cables, you can purchase pre-made from our host (NAWS):

Battery Interconnect & Inverter Cables

Or from probably from a local battery distributor.

You can purchase manual crimping tools:

Hammer Crimp Tool for Large Terminal Lugs


The middle of this thread has some links/information about crimping:

Battery Cables

You can search for more information on Crimping by using Google and adding "site:wind-sun.com" for easier searching:

• hydraulic crimp tool site:wind-sun.com

The problem is that many of the inexpensive inverters (typically kWatt rated 12 volt inverters) do come with their own cables... But the cables are way to light weight and frequently use two cables in parallel to carry the current--That is usually a no-no in electrical wiring (one cable fails then the other overheats).

-Bill