One Year Review - 48v RV Solar Power system - What I Got Wrong
ฝัง
- เผยแพร่เมื่อ 12 มิ.ย. 2024
- *Shock hazard prevention for All-In-One systems*: • All-in-One Solar Syste...
SanTan Solar Used Solar Panels: www.santansolar.com/?ref=DiyS...
Signature Solar: shorturl.at/fPW27 ($50 Discount Code: RAY)
Current Connected: shorturl.at/pLNR1
*Full install video*: • 12v to 48v RV conversi...
Chapters
0:00 Intro
0:25 RV Solar Power System Summary
0:50 RV Air Conditioner run time
1:24 AC Soft Start
2:09 RV Fridge
2:50 Powering Multiple RV's
3:41 Easier to install solar panels
4:28 Wire Nuts
5:10 48v to 12v Step Down Buck Converter
5:35 Removing 12v Battery & Converter Box
8:30 Portable Power Stations Are More Simple
9:00 Grounding - GN bond.
13:10 Goose Neck Hitch
14:14 12v VS 48v
15:06 Give-a-way
___ THE ORIGINAL KIT ___
-Growatt 3000 48P inverter(recommended for RV's): signaturesolar.com/growatt-48...
-Growatt 3000TL LVM-ES : signaturesolar.com/growatt-48...
-48V Battery: signaturesolar.com/eg4-ll-lit...
-Combiner box: amzn.to/3OVpxdi
-48v to 12v step-down converter: amzn.to/3OV6FuV
-Extended Communication Cable: signaturesolar.com/3ft-rs485-...
-Extended Battery Cables: signaturesolar.com/72in-2-awg...
-Solar panels Cable wire: amzn.to/3KDgwmA
-MC4 connectors: (I ordered 6): signaturesolar.com/staubli-mc...
-MC4 connector crimpers: amzn.to/3QHpuTN
-New Solar Panels: signaturesolar.com/shop-all/s...
-Used Solar Panels(discount code:"DiySolarFun5"): www.santansolar.com/product/u...
-Solar panel mounting brackets: amzn.to/3qy4c0o
-Double Sided 3M VHB Tape for mounting brackets: amzn.to/3OT8o47
-Solar Panel wire management clips: signaturesolar.com/pv-2-wire-...
-Insulated screwdriver: amzn.to/3QAGpHx
-Roof sealant tape: amzn.to/47vZVeo
-Solar Cable Entry Gland: amzn.to/3QElhAh
-Victron Energy SmartShunt 500 amp Battery Monitor: amzn.to/3DTqvk2
Recommended Solar Stores (Using these links will help support the channel)
Current Connected........ currentconnected.com/?ref=diy...
Signature Solar.............. signaturesolar.com/?ref=DiySo... ($50 Discount Code: RAY)
SanTan Solar................. www.santansolar.com/?ref=DiyS... (%5 Discount Code: RAY)
ShopSolarKits................ shopsolarkits.com/1302 ($100 Discount Code: RAY)
Ruixu Batteries.............. www.ruixubattery.com/?ref=fOK... (Discount Code: RAY)
PowerQueen Batteries.. ipowerqueen.com/?ref=DiySolar... (Discount Code: RAY)
Contact info
If you want to get a hold you me you can email me at: diysolarpowerfunRay@gmail.com
I am not available for personal consulting. Please reach out to me in the video comments where I and others can provide feedback to you
Disclaimer
I am not a licensed electrician. Working with electricity is dangerous and can lead to injury or death, even when following documentation and instructions. I can not be held liable for such damage or injury. I am not giving or seeking to give advice on how to work with electricity. You should consult with a licensed professional whenever possible and get all work reviewed by an inspector and follow any local regulations in your area. I'm documenting my projects for informational purposes only. Electricity can kill you! BE CAREFUL! - วิทยาศาสตร์และเทคโนโลยี
Hey Ray! I really appreciate your nextdoor neighbor help. It's refreshing to not watch a know it all person with big production. Just trial and error with knowledge! I love it. As a 30 year Advanced Auto tech and small business owner in the California Bay area I have knowledge for electrical systems. But your easy 48v system and then just plugging in the shore power connector from the trailer was MIND BLOWING!!!! LOL. you rock! Keep it up. And if you're ever out this way, don't ever hesitate to give me a call. Thanks so much!. San Ramon Auto Repair. Dan C
Thanks! We'll do. Looks like you have a great shop down there! :) 4.8 stars! Nice!👊
Good job, Ray. The only thing I disagree with is removing your 12v battery, if you have a 24 or 48v system, especially if you have high amp 12v loads. For instance, my 5,500w generator requires over 300 amps to start. My hydraulic jacks and slide also are high amp draw items that need a high current source. We use both a 12 and 48v system to power our motorhome. It's good insurance to have a redundant system in case one goes down.
We're old, retired FTers who designed and built our system ourselves, on a tight budget. It took us 5 years to gather the resources to complete it, doing all the work ourselves, but it was well worth it. We started by building a 620-watt liftable solar array on the side of our motorhome. It makes a nice bedroom window awning too, practically lifting itself with a couple gas struts, and it's easy to clean, standing safely on the ground. Next, we built a 12v, 560ah LiFePo-4 battery with 8, 280ah prismatic cells. We use a Heltec 330amp BMS (1,200a surge) with a 5a active balancer. It cost us less than $1,500 to build this 7.1 kwh battery, including the high amp BMS. We chose these cells rather than a pre-built battery because they fit perfectly under the steps of our MH where our old pair of golf cart batteries used to reside. We insulated the battery compartment, cut a small hole in our step risers and installed a tiny computer CPU fan to keep this space at close to room temperature, so we don't have to worry about the BMS shutting down charging due to low temperature - or their life reduced from getting too hot. Our 12v system uses an 80A Progressive Dynamics LFP converter/charger, a 1,000w Renogy inverter, a 50a Epever MPPT charge controller and a Lnex battery monitor. The only time we plug our converter/charger in is when we are on shore power, which is a rare event now that our 48v phase is complete. We built this entire 12v phase of our system for under $3,500.
By mounting the solar array on the side of our coach, we left the roof free to rack 8, 550w solar panels (4,400 watts) down the length of our 35ft Class A, 15" off our roof, above our AC, vents, etc. We built the rack out of 2" aluminum angle with the front 2 panels of ours sloping down at a shallower 9.5-degrees to meet the roof, gently easing airflow over the array. It covers our entire roof, providing some nice shade with plenty of cooling air underneath, increasing solar output and reducing the heat load on the air conditioners too, though our overall height is still just under 12 ft. We mounted our Sungold Power all-in-one 48V, 5,000W Inverter/100A charge controller/battery charger, breakers and a Lnex battery monitor on the wall in our bedroom, saving us space as well as money. We chose the Sungold Power unit for several reasons. First, it supports up to 500 volts from our 400 voc solar array, and unlike a Growatt can work without batteries hooked up. It also has a power saver mode that only uses 20-25 watts when idling. It's selling for $764 now - not bad for a 5,000-watt PSW inverter (with the same 95% efficiency as a high-end Victron unit) and 100amps of combined 48v battery charger/charge controller capacity. Our 48v battery uses 16, 320ah prismatic cells and a 200amp Heltec BMS to keep it safe. Together with our 560ah 12v bank, we have a total of 23.5 kwh of batteries onboard - kept charged by 5,020 watts of solar. We removed the rooftop A/C we had in the bedroom and replaced it with an EG4 28.5 seer-2, 12k btu mini-split heat pump on the upper rear of our motorhome. It's super quiet and cools as well as our 14.5k btu soft start equipped Furrion we installed up front. This second phase provides 24/7 off-grid air conditioning and heat from the heat pump. We can run both A/Cs, microwave and charge our batteries from solar at the same time, even in winter. We have a total of 6,000 watts of 120v inverted ac power, giving us off-grid electrical self-sufficiency for a total budget of around $11,500, including the $1,500 high-efficiency heat pump.
Take care, we hope to see you down the road one day.
If your only regret on the inverter is the solar input, you could add a separate solar charge controller (ignore the one in the inverter). I like victron smart solar (has bluetooth). The 100/20 has a 48v capable version and a pretty good price, but you would need to rewire your solar panels and as 20amp at 48v is only about 1000 watts you might need two. A higher voltage input, higher amp controller costs more but probably is well worth it in your case for a more simple swap.
That's actually a good idea. I think I'll do that! That way I'll also have the larger voltage MPPT if I ever need it in the future. Thanks
4:25 The stick-on flexable solar panels can get HOT! Isaw one youtuber who almost burned a hole in his roof with them.
Wow, that's nuts!
best videos I've seen on coverage of RV inverter topic... the original 48v install vid and this one. Even got the bonus here on gooseneck extension risk (lesson in torque). You can get adapters from gooseneck balls to kingpin depending on your tow vehicle arrangement needs (they seem lighter than standard fifth wheel hitches but the ones I've seen do require some torquing of bolts when installing the adapter and may not be faster to remove the fifth wheel frame to clear up bed than a normal set up, just easier to carry and store)
It is really nice when someone shares their "lessons learned".
Fantastic research! Looking forward to your next video powering your home with rv to save on utility bill!
Coming soon!
Note on wire nuts, even in a stationary house, you're supposed to tape the wire nut in the same direction you twist the nut to keep it from untwisting. Wagos are nice, but wire nuts are fine in an rv if done correctly.
Thank you! I think I'll do that instead
Hey Ray, enjoyed your video. I have a Class B rv that I replaced the A/C with the Coleman Mach something. It is a 13.5 BTU and watching the Hughes power watchdog app on my phone if I go straight to a/c low, the amperage jumps up to over 16 amps. Iif I start on low fan and than high fan and than low cool up to high cool, the amperage manages to stay around 12 amps before leveling off. I used my EcoFlow Delta Max 2000 to see if I could run the a/c and it was able to run it, as long as my amperage did not exceed 15 amps. At 15 amps my Ecoflow would shut down. Once the a/c was on high and had settled the amps leveled off to between 6 to 8 amps, that is using my fridge and lights too. Appreciate your honesty and sharing your mistakes with us so that we do not repeat them.
Thanks for the info. I just liked and Subscribed! :)
You only want ground and neutral bonded when you’re not connected to shore power. The inverter should have a screw inside of it that can be inserted to bond the ground and neutral. It should unbonded whenever it senses shore power.
Thank you. I totally forgot that functionality was available. I want to say that this wouldn't work on my previous inverter, but I actually haven't tested it on this one now that you mentioned it. That would definitely be the better way to go.
for panels just do unistrut rails on the roof, then they are up off the decking panels run cooler and you can cable manage/change out panels at any time, take the panels with you to a new trailer.
Very good content thank you and great information . One thing though on the stick on solar panels you were talking about be careful with the lifetime of the panel as they can deteriorate quickly in a hot sun environment.
Good feedback.
This is awesome! I just watched your install video yesterday and today the - year update! Great content, would you still recommend your selections? I already ordered the EG4 LL S 48V using your discount code 👍👍
Yes, I do. However there have been a lot of people that mention the stick down panels aren't very good. So I would probably go with the traditional type of panel that I currently have. Just make sure you order the correct inverter for how many panels you can put on top of your RV. I mentioned a few different inverters in this video.
Rey, bonding neutral to ground is done at the source, not at a sub-panel. Your RV is a subpanel to the shore power pedestal. Bonding is supposed to happen at the shore power pedestal. With an inverter, take Victron as an example, when seperated from shore power, an internal relay closes to create neutral to ground bonding since your inverter is now the source of AC power.
Learning from your experiences is sometimes painful and expensive, but they are lessons you'll likely never forget. I wouldn't go 48v on an RV, personally, unless I was going to do a ton of boon-docking.
i have installed those Victron multiplus2 that 2400w rating is very conservative i bet it would run your ac and microwave at the same time for a few minutes it would say its overloaded but they will hold it for a bit.
Quick fix for your wire nuts... I took a couple of wraps around the nut & wire with electrical tape, Not had one come loose in over 5 years.
That's a great idea. Someone else mention that also.!
Flexible solar panels are notorious for catching on fire. I would avoid. They also don't last nearly as long as glass/fraimed panels.
I would have left the 12 volt battery in the system if for only to absorb the initial inrush of any loads on the 12 volt system. This would make life a lot easier for the 48 to 12 volt DC to DC converter. just a thought. Great video
I have a question. Why not just stay with 12v instead of going to 48v? Would it have been much easier to stay with 12v or not much different?
This has been extremely helpful. I am working on setting up a 48V RV system this spring summer. I am running with a EG4 6000xp for split phase and then using a chargverter for a 120V separate input. I am now very mindful of the solar now. I have 5 panels as well with a VOC 45V. I may want to see if i can get another panel or two in series now due to shading.
That will be a nice setup I think. Let me know how it goes. Do you have any 240 volt appliances?
@@diySolarPowerFunWithRay I don't currently have any. One of the reasons I picked this AIO is it seems to have lower idle current consumption than a lot of the others. Since the RV has a native 240V split phase feed I was trying to keep it that way and the fact that I do have two ACs. By keeping it split phase it gives me the option to install mini splits in the future as well.
@robertrapp5953 very nice. I think you'll like it. If you don't end up liking the solar charge controller that requires all your solar panels to be in series, you could always get a separate charge controller that accepts a lower voltage so you can connect some solar panels in parallel to help with shading. And then you can 6000 XP mppt for any large solar arrays you want to attach... which would be good for ground arrays in case you need a lot of power in an emergency...powering your house items, etc..
Good point on using it as backup house power. Never really thought of it like that but you have an excellent point. I should have a minimum of about 10V higher than you had per panel with 5 in series.
Good stuff Ray! There aren't many videos on 48V system installs for 5th wheels yet, prob due to the lack of specific equipment. I'm sure this is the way the industry is going.
I tried using a 48V Sungold all in one, which is great at what it's designed for (off grid apps) and gets high marks for simplicity but won't seamlessly accept the line to generator shift. As far as running the AC longer, its a matter of money. You have enough room to add at least 2 more batteries to achieve that goal!
In the end I opted for a Victron 48V/5K inverter, 20Kwh battery array with 4 24V in a 2S/2P set up. I can run one AC for 9+ hours, plus the converter (not efficient, I know) and all the small loads with no problems. Battery at 70% after test run. Also 2Kw of solar installed, but never seem to get more than 1200w. Still fiddling with that, but that's the fun part too. And yes, I've installed soft starts too. Downsize is weight on the front end and a single phase input. My thinking is we will just be careful with loading until we know the capacity.
Wow!! That's awesome! Do you find that having the single base output limits you at all? Aren't all of your appliances 120 volts?
@@diySolarPowerFunWithRay We are about two months into traveling, no issues so far, but its early spring so no big A/C loading yet. Yes, this config only allows 1 leg (50A) but the Victron splits it to feed both sides. The way it works is to shut down one side when running on the batteries, which is fine because it disconnects the water heater, refer, main air loads. Also the DC converter, but I just moved the plug to a different outlet to maintain and run the refer and heater on LP.
Checking the single 50a wire, it is warm , but not excessively. Something to keep an eye on thru the summer tho. So far so good, my biggest concern is still weight on the front end....
Try to use a micro wind turbine in conjunction with solar. Best of two worlds.
Nice, I'd love to try one of those out. Any you suggest?
We measured the output of a wind gen during some winds, and the results were disappointing. 9 amps at peak wind gust. They don't come close to their stated ratings. You need at least 4 if you have any hopes of making a charge contribution to a bank of LFP batteries...
Hey quick question is it better to get a -shunt or battery monitor to access the life of battery and all that info??
I like the victron battery monitor shunt. I think I have it linked in the kit in the description. Works awesome!
use eletrical tape on the wire nuts, keeps them in place
That's a good idea. Thank you!
Great video - I'm weighing going to 48v.
I tried to get in on the giveaway on a battery - in order to get an order number from BangGood for the 12.8v 100ah 1280Wh LifePO4 battery, I have to actually purchase one. I don't want 2.
I would love to have that equipment u have given Away. What's it going to take
Look at 15:05
Hi, I love the videos that you did on the solar system, but how can I figured out how much solar panels needed for my rv? I have a 2001 Four Winds Motorhome.
That really depends on what you want to run. Some people have a generator and use that whenever they run their microwave or air conditioner or hot water heater. If that's the case you probably don't need too much solar just something to keep the battery topped off from the smaller running appliances like lights, etc.
If you want to run your air conditioner I would put as many solar panels as you can fit
Please don't use one of those ground-neutral bond plugs. In your AC breaker space, this is where ground and neutral should be bonded. You can also get a 'ground' for your RV! There are rubber 'tails' you can hang off of the bottom of your RV that touch the ground when you are stationary.
What about when I pull up to a RV Park and they already have a G/N Bond in their main panel? I like the simplicity of using a bonding plug for that reason. Do you have a link to the rubber grounding "tail"? That's interesting.
That may not hold up in a lighting strike, but it might make your RV a smaller target for lighting due to keeping your RV at the same potential as the Earth. The key is a good connection...
@s.mendez7160 thanks. I would think my rubber tires on the ground would have the same effect. Maybe that product is just a scam?
@@diySolarPowerFunWithRay Your rubber tires insulate the vehicle from the ground. Rubber is not conductive.
The 12 volt battery is needed for breakaway on travel trailers, right?
You need 12 volts, yes. I'm supplying that with my step down converter. Typically trailer brakes will use 3 amps of current per break if the Breakaway switch is pulled. Since I have four tires it will use a total of 12 amps.
Have you considered just adding a second 48V battery to increase your battery life. Simple change and you have the space to do it.
Yes, I added it for a 21 day trip into mexico. It worked awesome
How many 48v batteries have you been using? Are you planning on adding more?
Thanks for the video!
Normally only one. But I connected a 2nd battery for the long off grid mexico trip.
@@diySolarPowerFunWithRay thanks for the reply. I’m working on a similar system up here in Idaho Falls.
I think the all in one 48v systems are so much simpler and your setup is a great example of that. I have a 50 amp Rv so I’m going with the EG4 6000xp.
Fingers crossed.
cool
I want those items 👀
I want to give them to you :). 15:05
WAGOs are a good option, but note that when vibration is an issue you still need to provide a bit of restraint with the WAGO to prevent the wire from twisting in the connector... it is possible for it to twist loose (though it takes an effort). You also don't want the levers to get pushed up accidentally. A little electrical tape does the job nicely.
Here is the solution I use for running legacy 12V gear from a 48V or 24V home battery. It's ultra simple and very robust. Basically it's just a Victron 75/15 charge controller and a small 12.8V LiFePO4 battery. That's it. Oh, and a fuse. You wire it: 48V -> (10x38 solar fuse 10A) -> "Solar input of" Victron 75/15 "BAT output to" -> 12.8V LiFePO4 battery. That's it. Works great.
10x38 Solar (ceramic) fuse 10A ($20 for 5 pcs)
10x38 fuse holder (Baomain solar pv fuse holder) ($9)
Victron SmartSolar 75/15 charge controller ($67)
30Ah 12.8V LiFePO4 battery ($90)
Total: $186 before taxes. And these are all fanless devices.
This example assumes trickle-charging at 15A (roughly 190W) is sufficient to keep the 12V battery in good shape. The battery itself can handle larger loads and surges, size to what you need. E.g. A 30Ah battery can discharge continuously at 30A = 383W and typically handle surges in excess of 500W. The charger part of the circuit doesn't need to deal with the loads, it just needs to keep up with average consumption across a few hours to keep the 12V battery in good shape.
That's the huge advantage of having a 12.8V LiFePO4 battery in the mix... no worries about loads or surges.
If 15A isn't sufficient then the Victron 100/20 smartsolar charge controller ($90) works well too... 255W charging capability. If that isn't enough, a Victron 150/35 smartsolar ($185) for up to 35A charging.
Always buy the "smartsolar" version of the Victron because the bluetooth interface and Victron Connect app makes setting the thing up and monitoring it trivial.
WARNING! The fuse on the 48V battery side is mandatory because Victron charge controllers have a fail-safe on output over-voltage that shorts the "solar" input. Normally it would never hit this fail-safe, but obviously you need a fuse on the 48V side just in case it does. The charge controller already has an auto-fuse on the output side.
One can also use a 48-to-12V dc-to-dc charger instead of a charge controller, but those tend to be more expensive. The charge controllers work really well for down-buffering a higher voltage home battery to a lower voltage satellite battery.
--
Those Amazon 48-to-12V buck converters do work but there are two problems. Actually more than two problems but two main ones. The first problem is that a failure condition can end up feeding 48V straight through to the 12V output. The second problem is that these devices are typically NOT current limited (even when they say they are), and they can overheat.
-Matt
Like that idea of using a solar charger as a step down for the 12v stuff! Will probably end up doing that with a 50ah battery!
@@nismor3490 Yup. I use the concept all over the place. As long as the "solar" input is reasonably fused when sourced from a battery instead of from panels, I consider it safe and effective.
I think that would work as well. I wonder what the efficiency is. If you have a failure on your charge controller, wouldn't it also have the possibility of sending 48 volts to your 12 volt system.
My Buck converter has a current limiter on it. I tried pushing it over 30 amps, and it turns off. That's definitely to test though
@@diySolarPowerFunWithRay It will likely blow the fuse if the FET fails and feeds the input voltage to the output, due to the battery on both sides.
The efficiency for a well-designed buck charge controller is 98% or higher. It is very, very good. The reason is primarily because charge controllers are current-regulated devices and have poor output voltage regulation (it will bounce around a lot)... but they don't care because there is a battery connected to the output.
Efficiencies for buck DC-DC "power supplies" tend to be a bit lower. 95% is more typical. This is because power supplies are voltage regulated devices and must output a stable voltage... tighter regulation, which eats into the efficiency a bit.
This is also why grid-tie inverters can operate with very high efficiencies. Grid-tie string inverters can hit 99% due to the very high DC voltage and 240VAC output, all current-regulated instead of voltage-regulated.
(however, junk grid-tie inverters such as the cheap 120VAC grid-tie inverters on Amazon tend to run 80-85% due to the cheap design and the lower input DC and low output AC voltages involved).
But regular power supplies, AC or DC, are typically more in the 80-95% range depending on the quality and voltages. The best AC-to-DC power supplies typically run 92%-95% efficiency while the junk one buys off of Amazon is more in the 85-90% range.
An example of a high-end power supply would be something like a Mean Well HLG series unit. Those can hit 94% converting 120VAC to 48-60VDC, for example, with a 0.95 power factor or better at max load.
AC chargers (AC->DC/BAT) are more around 90%-95% depending on the quality. Most chargers typically hover around 90% when charging 24V or 48V, and a bit lower when charging 12V. This is because the power has to go through two conversions instead of one. The AC has to be rectified, often also isolated, and then bucked-down. And a power-factor-correction circuit is required for the rectification to be even remotely efficient.
So cheap chargers without the PFC circuit will be more like 85%-88% while more expensive quality chargers will be 90%-95%.
-Matt
Another thing you got wrong was using a high frequency non-UL458 listed inverter. You're lucky that you haven't electrocuted yourself by not using a UL-458 listed inverter charger. You would have been far better off using a UL-listed low frequency transformer based inverter charger designed specifically for mobile applications.
fyi: "just stick them down" solar panels, you mean the flex ones. yeah i've got those. except not with the sticky tape. bad idea, they can fly off when you drive, and then that'll damage them and possibly other stuff. they make the grommet ones, which i have, much safer / better, i still have the option to stick them down with my own solution (whatever that is, def not 2-sided tape!!!)
There are definitely some cheap ones out there... I hear the ones from boozeRV are good but I haven't tried them myself.
Hey man love the video gona keep in mind everything learned do u think it’s smarter to have a 48v system rather than 12v if wanting to run multiple things? im trying to put together a system now but can’t afford a battery at this time so far I got a small 2000 watt inverter 4000 max output and the wiring and a fuse but nothing to put it in yet. Do u know if maybe I can contact a company to get a freebie
48 volt all the way!! :)
Sounds like you're still going to be making mistakes the BougeRV panels are only around 30 voc. That's just not enough to overcome cloudy days and shade. Also you definitely need a decent Victron solar controller to make the most mppt from the solar.
My current panels are also around 30voc.
These I know it all comments on youtube are annoying sometimes.
@@meilyn22I don't bother commenting much I usually just watch people waste their time and money. But as this guy has had a few attempts already and still isn't going to get the best results I couldn't help myself. I should know it all I've been in it for over 30 years. 🤷
wagos and wirenuts burn just under 100 amps
My solar panels produce about 6 amps so that should be definitely under the 100 amp rating
one wire popping off in a cupboard wont start a fire FYI. Not how electricity works
It depends on how many volts are on The Wire when it comes disconnected.
Those bouge rv panels aren't what they claim. I wouldn't waist you money on those. They don't handle the heat or produce as advertised. Also your cabling is probably the main issue as well as the flat mounted panels. I learned that the hard way.
Thanks for the feedback on the Bouge panels. I had adjustable panels on my previous RV... after 3 years I didn't tilt them once.
Try some rigorous investigation before you dive in.