How many W of solar to fill an AL30 dive tank

[a64pilot]

Please don’t buy a compressor for an air rifle or any other means and intend to breathe the air you get from it. Air rifles don’t care if there is CO or a little oil in the gas or not, you will.

Really Scuba board is probably a better place to discuss this.
I suck a math so someone can throw numbers around all they want to try to prove you can do it off of batteries, but I know from experience you need a 7 KW generator to run a Bauer jr, and your not replacing that with panels and a battery bank of any realistic size

AC, DC Electric, Diesel or Steam, the power required doesn’t vary with the source.

Or another way to look at it is yes you can do it with Solar and a battery, just need several KW of panels and a forklift battery.

[transmitterdan]

I want to echo the advice to only use a compressor designed and certified for breathing air. I have a friend that took about 5 breaths from a tank that had oil contaminated air. She can never dive again and had more than a year of intensive respiratory therapy. Today she is not the same person.

Oil, CO, CO2, H20 and other contaminants are dangerous when introduced to a tank under pressure.

And please consider the current you will need to compress air to 3,000PSI using 12V DC. It will likely be over 100A. Make doubly sure of your connections that they don’t overheat and start a fire. Have a marine certified electrician make sure the installation complies with all ABYC recommendations else you may find your insurance null and void. In fact, I recommend consulting with an ABYC electrician before spending any money to avoid disappointment down the road.

[Dave_S]

Thanks guys, point taken, I'll reconsider.

[hellosailor]

"from 2.2kW."
Even assuming Bauer's number are on the nose, and ignoring losses in the system, that's going to need the full output of a 500W solar array for a full day in good sunlight. And that's optimistic, and also assuming nothing else including your batteries was wanting to share any of that solar power.
So it is *possible*, but given that as a best-case scenario, is it something worth pursuing? Do you have room for a spare 500W solar array, or, enough battery capacity to tuck away that much power?

[john61ct]

500W will input maybe 150-180Ah @12V.

[nwdiver]

Good luck.......let's use know when it doesn't work.....

[wtmf]

has anyone thought of using an exersize bicycle connected the air compresor? tandem bike if more than one person is diving, will a windmill work, how about more solar panels and a way to hook up the batteries TEMPORARYLY as a 48 volt system?

[Dave_S]

Originally Posted by wtmf

has anyone thought of using an exersize bicycle connected the air compresor? tandem bike if more than one person is diving, will a windmill work, how about more solar panels and a way to hook up the batteries TEMPORARYLY as a 48 volt system?

12Vdc is actually quite suitable, its one and as far as I can see, only downfall is the size of cables to run the current required. Now that arguement makes no sense to me when compared to 240Vac through an inverter. If I have an inverter I still have to run the same current to the inverter at 12V (in fact more). So why not just move the 12V motor close to the batteries and not burn up power in inefficiencies.

The 12V motor will cover the extra power needed at start up better than 240 or even a petrol engine and will run straight from the batteries. People are having issues because they are calculating the figures on 1hr use, what seems to be missed is that it will take <20min to fill one of my tanks after normal use and I only need to fill 1 tank per day.

I have room for 1.8kWh of solar panels. 1.8kW for 5 hrs a day = 9,000W and I can have 6,000W available stored in the batteries. 12V motor draws 2200Wh but only run for 1/3rd of an hour = 700Wh lets assume things are a bit tired and inefficiencies are high and this will actually use 1500Wh, that's less than an hours charging on a good day.

Re people power....

America Cup work on 0.4kWh of power per person, you need 2.2kWh. I saw your (?) post from a while back and thought about the bike compressor but unfortunately it looks Like it might be too hard to peddle.

[john61ct]

Originally Posted by wtmf

has anyone thought of using an exersize bicycle connected the air compresor? tandem bike if more than one person is diving, will a windmill work, how about more solar panels

Joking right?

From the beginning of this thread, clear mathematical facts are presented.

It is not rocket science to learn enough about the basics

between the reality of power & energy, limitations and physics

limitations of space and weight

and financial limitations

Yes it **could** be done, with a wealthy crackpot funding a boat designed specifically to accommodate the huge investment in panels and battery tonnage required.

But this whole idea is pie in the sky impractical for normal people on normal boats.

"Gee wouldn't it be nice" "it really **can** be made to work" and "you guys are just being too pessimistic" does not overcome harsh objective reality.

https://www.welovecycling.com/wide/2...ter-can-power/

[john61ct]

Originally Posted by Dave_S

People are having issues because they are calculating the figures on 1hr use, what seems to be missed is that it will take <20min to fill one of my tanks after normal use and I only need to fill 1 tank per day.

OK, yes that is news to me?

Please link to the unit that will recharge your tank in 20min.

Have you bought it yet?

You need to do that as a first step, in order to put an Ah meter (coulomb counter) on it and learn how much power it actually consumes to recharge your tank.

This can be done from shore power, if DC powered from your battery charger.

If you do not own it yet, it may be "possible" to get a dealer or an owner of that specific product to conduct the test for you, but I think unlikely.

Once you have that real-life number, then it will be a piece of cake to decide whether or not you want to invest in the solar + extra bank capacity to handle that load.

The key to your goal is a unit that does this job as efficiently (least watt hours consumed) as possible, whether it takes 20min or three hours is irrelevant, except for the noise factor of course.

I know with watermakers, the faster units (high ph) are the least energy efficient (Wh per gallon).


> I have room for 1.8kWh of solar panels.

That is a theoretical peak, might see it for 90 minutes per month in ideal conditions.

At 12V in good normal conditions, that may be ~600Ah per day available for loads. All your loads, not just this one.

> 1.8kW for 5 hrs a day = 9,000W

Watch your units, Watts can't be stored, only watt hours. That 600Ah I gave you, the usual units, translates to 72000Wh at 12V.

> I can have 6,000W available stored in the batteries.

Not sure what that means, watts cannot be stored. Maybe just stick to Ah?

Assume 12V for now. . .

If power storage using lead ends up being your limitation, then

going to LFP will triple your usable power storage per square footage or per pound.

But it's a **lot** more expensive.

Anyway, get your most energy efficient possible compressor, whether 115Vac or DC powered, capable of filling one tank within a time frame acceptable to you.

Then measure the Ah @12V required to fill that tank.

That really is the practical first step in figuring out how to (if it's practical) to power the process off (mostly) solar power.

If you end up needing a generator after all, even if only on cloudy days, at least you are then minimizing its runtime hours per week.

[john61ct]

Originally Posted by john61ct

> 1.8kW for 5 hrs a day = 9,000W

Watch your units, Watts can't be stored, only watt hours. That 600Ah I gave you, the usual units, translates to 72000Wh at 12V.

> I can have 6,000W available stored in the batteries.

Not sure what that means, watts cannot be stored. Maybe just stick to Ah?

Assume 12V for now. . .

Sorry that is 7,200Wh or 7.2kWh

not 72000

[rapanui 2]

https://fr.aliexpress.com/store/prod...63435998Uhy30O
anybody try to fill a scuba tank with such a machine???

[nwdiver]

Originally Posted by rapanui 2

https://fr.aliexpress.com/store/prod...63435998Uhy30O
anybody try to fill a scuba tank with such a machine???

Go ahead.....when we don't hear from you we will know you won a Darwin Award.......you obviously know nothing thing about diving nor have you read this entire thread.....

[GrowleyMonster]

I wouldn't add solar panels just for the sake of running a compressor. You are gonna need a LOT of solar to completely eliminate need for a genset or a compressor engine. If you want more solar for other reasons then cool.



I am in kind of the same situation. I would very much like to be able to fill my Al80s onboard. Thought about hookah yeah, but I already have a bunch of scuba gear including a full face mask with comms, very handy for working on the boat. The full face rig has integrated second stage, not absolutely sure it will play nicely with a hookah compressor.



I do not have any solar and I dont intend to install a huge array of panels ever, maybe over the cockpit and dinghy davits. Fat boat, but still only looking at probably 600w max. Inlikely that I would even be able to run a hookah rig off the 12v for more than a few hours. Few as in a half day or less. The as yet to be installed genset will be doing the heavy lifting, solar mostly just to keep the batts topped off as much/often as possible without starting any infernal combustion engines and running them for low current float/topoff charging. Bulk charging will be done mostly with the Westerbeast or the genny.



I have given much thought to simply gearing the output of a BLDC or an induction motor way way down, but there are efficiency issues at play. No HP compressor is going to function well at speeds very much below rated speed. Motor efficiency is not the issue, with appropriate reduction. Its the compressor. A hookah compressor running off the batts for an hour or two at a time would probably be a much more doable thing. 600w or 800w of solar would probably keep up with very intermittent use in very sunny weather. Remember rated output of solar panels is not what you will get over the course of a day, just what you COULD get under optimum conditions, which only exist for 2-3 hours of every clear summer day.


I like cheap stuff. It is cheaper. That's a good thing. But a cheap diving air compressor or any cheap Chinese engine is probably going to go North on you in short order. Then also there is the issue of trust in the compressed air output quality. Gasoline engine? Okay, but me, I don't care to have gasoline, propane, etc on my boat. To me it is not worth the hassle or the risk. Maybe you are okay with that, I don't know. Lots of people do it that way and you seldom hear of fire or explosion as a result. Seldom I said, not never. I would ask your insurance about all that gasoline engine business.

[downunder]

Originally Posted by Dave_S

Funny you should say that.

I saw one, it had a 3500W motor and filled tanks in under 20min.

I am guestimating on the high side that it will draw it all on start up, then a half of that on average to run once started. If I empty the tanks before filling and maybe a clutch or capacitor start. It should be able run drawing 1750W. If I only fill to 2000psi as transmittidan suggests, that should halve the power requirements from 3000psi again to 875W.

If it takes 1/3 of an hour to fill that should be 282Wh, that's not too bad at all.

Please feel free to correct me if I have got it wrong.

I will try and find the link but it can be done using solar.

A clever air/con electrician in Cairns who built his own powercat ran his coltri bauer jnr equilivant using a cheap 3000w/6000wpeak chinese inverter

The secret was a 3phase variable speed electric motor which he was able to vary with a controller. Also ran his 240V water maker off solar/batteries.

I think 44C would know where to find the link.