Hi 

I think the problem here is the definition of "working" IMHO. Of course if you put a small propeller or similar on your car or caravan it will spin around !! The kids hang out with those cheap plastic party things and they spin    The problem arises when you think that you can generate useful power from doing this. If you look at the theory of wind power(google ?) it quickly becomes evident that the area of the turbine is important and the speed of the wind through it. The efficiency of the system also has a VERY large effect too.

The sum of all this is, the chance of getting any real power is very  low. But if you wish to expand your knowledge of ways that do not work go for it !!! As for feeding the power back to make you move foward, sorry perpetual motion machines have been around since forever trying to get punters to back them. Never work and the theory says they never will !!

Some years back I was offered a small Jaycar wind turbine with the comment it was free to anyone who though they could get it to generate any useful power.  He would have gladly swapped it for another solar panel.

Cheers jaahn       

PS If I had a boat on a mooring and wanted to keep the batteries on float a small wind turbine would be OK. No trees or buildings out there. 

 

-- Edited by Jaahn on Thursday 16th of August 2018 11:37:43 AM

Peter_n_Margaret wrote:

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The vehicle has a very effective alternator fitted already which can develop lots of electricityif you want it and will be MUCH more efficient than hanging a fan out in the wind.
To take an extra kW (about 70A of battery charging) out of the alternator will cost about 250ml of diesel per hour extra.

Cheers,
Peter

---

 Good relevant points guys. There is a case for trying but when it gets to reinventing the wheel its a lost cause.

As an inventor/tinkerer I used to build my own model airplanes. My designs were radical and often crashed on their maiden flight. My then wife complained bitterly about the cost until I reminded her that her cigarettes cost 5 times more. Reinventing airfoils and flight principles doesnt work.

 

Hence Peter you are correct, the alternator is the common sense way to charge our batteries.  Now I'll concentrate on trickling wind power for static camping. Lightweight telescopic poles, most efficient and quiet vane designs and ease of connectivity . With solar already roof mounted its a no brainer really to pursue it even though power input is likely to remain low. 

 

The inspiration will come when on a cloudy windy day I look at the agm volts and its full...cartwheels . :) an alternative is a treadmill with my good wife or mini foxy ...

We had to get to the (not well camouflaged) advertisement....
Our 460Ah of AGMs will accept 70A from the alternator (plus 30A from the solar at the same time) when over 50% full, but that is not the point......
Whatever the battery type and whatever the charge rate, the alternator is a very viable source of power, even if paying for the extra diesel, because you only pay for the extra used and if that is only 20A then the extra diesel is minimal because many of the inefficiencies are already taken care of.

I suggest that running a diesel vehicle while stationary just to charge the batteries is probably still more efficient than running most generators (even powering a battery charger).
This is particularly true if you then leave the generator (and its dangerous fuel) at home.
We don't carry a generator in the OKA (and never have). We have run the engine just to charge the batteries enough to get to the next day's sun once or twice in 13 years. Even on bad sun days, the solar will give you something.

Cheers,
Peter

Regenerative braking is beyond me, not the concept but the set up. And I don't mind as the OP, that the topic goes off somewhat as "charging while you drive has many concepts not just wind as I originally suggested. "Charging while we drive" in any form could be beneficial for this thread.

Terry asked "are you suggesting this size battery is the norm for all RV owners..."  This is relevant as the diversity of battery systems out there are enormous. I'd be on the lower end, 1x 100amp AGM, 120W solar on the roof, 90W portable.  18 litre chest fridge, cpap and TV. Anything extra is too much weight for our 450kg tare 748 kg ATM(genny, extra panels although prior to the solenoid I considered a 1KVA Yamahe but expensive but lightweight at 12kg+fuel)..... Hence the need to fire up our V6 JBA to charge depleted battery but we haven't been away since the solenoid has been installed. Certainly that back up method will take the worry out of caravanning. So, unlike Peter's set up, my needs are to find lightweight methods of keeping my single battery charged as high as I can. Perhaps when this battery carks it a 120-130 amp battery would be more suitable with the extra weight tolerable but as I previously mentioned lithium is out of our price range.

 

-- Edited by Eaglemax on Thursday 16th of August 2018 05:25:26 PM

Perhaps some generalities regarding battery charge (acceptance) rates might be useful?

When batteries are charged or discharged, there is a chemical reaction going on. The rate that the chemical reaction takes place profoundly influences the rate that the battery can be charged or discharged. Several factors will affect the rate of the chemical reaction.

Yes, chemistry does make a difference. Lithium has a high charge acceptance rate compared with lead acid generally and maintains it to higher states of charge, but it needs to be managed to avoid overcharging and to avoid cooking the alternator.

There are also differences in the acceptance rates of lead acid batteries, depending on their construction. For instance, LA battery designed for cranking has more, thinner plates than a LA battery designed for long life cycling, so it will also charge and discharge faster (due to having the electrolyte in closer contact with the plates), but not last as long.
Even AGMs come in fast and slow recombination types. Those used for RVs are typically slow recombination styles to give maximum life (and therefore lower cost per kWh (or Ah) delivered).

Other factors influencing charge rate include the voltage offered by the charge source. Increase the voltage and the charge rate will increase. Increase it too far and you risk damaging the battery.
Alternators are typically configured so that they will not over charge a crank battery that is left connected continuously. Mine is probably typical at 14.3V. Much better charge rates would be had if the voltage was 14.8, but that is a bit too high for long time periods for not only the battery, but the alternator too. And if the cable run is long, you won't even get the (say) 14.3V to the house battery.
For a motorhome, it is likely that useful charging performance can be had from the alternator directly, but caravans will typically suffer from voltage drop to what was already a minimal voltage to start with.
Hence the value of DC-DC chargers which can boost the voltage until the battery is fully charged and then cut it back to protect the battery.
The same principles apply to any battery charger of course and is why solar controllers should be close to the battery, not on a panel a long way away.

Battery temperature is important. Lower temperature, lower charge rates. Good chargers have temperature compensation and adjust the voltage offered to the battery according to the battery temperature.

For Eaglemax who is looking to maintain minimum weight, but on a tight budget, my thoughts would be...
1. Leave the generator at home.
2. Maximise the solar capacity (preferably with light weight panels).
3. Keep the battery capacity modest. More charge ability is better (and lighter) than more battery capacity.
4. Utalise a DC-DC charger as a charging facility generally while driving and as an emergency facility if the sun does not shine and you don't want to go for a drive.
5. Choose your appliances VERY carefully and ensure that electrical appliances are as efficient as possible. [I reckon an efficient compressor fridge is probably lighter (including counting the solar panels & batteries compared with the weight of gas and their bottles - that might be an interesting further discussion? :) )]
6. Forget about wind generation :) .

Cheers,
Peter

Peter_n_Margaret wrote:

---

Battery temperature is important. Lower temperature, lower charge rates. Good chargers have temperature compensation and adjust the voltage offered to the battery according to the battery temperature.

---

Is that true for all chemistries? 

Is there an ideal temperature for each chemistry?

Jim

-- Edited by Grandad5 on Friday 17th of August 2018 09:35:05 AM

Having invested in the inverter and solonoid I'll stick with that until my new van. Then I'll seek out a dc-dc. When looking at dc-dc, what are the recommendations Peter? I dont want to buy twice.

-- Edited by Eaglemax on Friday 17th of August 2018 12:20:50 PM

I have been very happy with the Redarc dc-dc (BCDC1225LV) that I have been using in my ute for the past 5 years
Recently purchased a BCDC1240D for my caravan (yet to install it as the van is undergoing a comprehensive renovation), this model has built in green power priority www.autoelec.com.au/redarc-bcdc1240d-dual-battery-isolator-system-dc-t
I have purchased a lot of gear from Bairnsdale Auto Electric via their Ebay store and highly recommend them, they are also authorised Redarc dealer so warranty won't be affected by online purchase

Grandad5 wrote:

---

Peter_n_Margaret wrote:

---

Battery temperature is important. Lower temperature, lower charge rates. Good chargers have temperature compensation and adjust the voltage offered to the battery according to the battery temperature.

---

Is that true for all chemistries?   Is there an ideal temperature for each chemistry?

Jim

 

           _______________________________________________________________________________________ 

Hi Jim 

Perhaps you could look here for more information 

https://batteryuniversity.com/index.php/learn/article/charging_at_high_and_low_temperatures

Jaahn

Eaglemax, If you can utilize wind power on your van while in motion, without creating excessive drag, you will have invented perpetual motion, you will be rich beyond your wildest dreams. But alas it is not so. I would suggest that you put some of you brain power into building a caravan that has reduced drag, the resulting saving can be put towards fuel and a engine driven battery charging system, via a DC/DC charger - Lithium is the new word.

Drag increases at the square of the speed, so reducing drag can achieve quite a lot, as you can see a flat plate will give you near 100% drag, while a streamlined shape, drag is much reduced.

Parasite drag, in our case TV aerials, vents gas bottles, in fact any protrusion into the airflow contribute.

 

 

A point that people don't grasp, is that it is the rear of a vehicle that's more important to stream line than the front, there is plenty on the net to read about this.

Hi Ian,

I owned a T@B large teardrop van 10 years ago (see pic of the same). T@B brought out a limited number with door on the left side. At only 500kg tare it was a good van but not good for long holidays with no shower/toilet and raised dining table type beds. The fastest caravan on earth when towed by a Porsche Cayenne V10. 230kph.  https://www.youtube.com/watch?v=BLfrEq5-mnc

Such a shape is ideal but internal space utilization isn't good. I could stand up in it but only in the middle without hitting my head. No room for shower and toilet etc. Doesn't suit. However I've designed my next caravan with some streamlining in it. See LINK below.  Like my JBA which is a kitcar built in 2001 the van will resemble, in some design ways, the period of vintage but with the benefit of modern front design and internal comforts. The front is sloped well but not too far as it will have a window, the rear is slightly sloped to allow a gutter to catch rain water from the roof and add some shape. If I extend the van into a teardrop rear end it wont look good and length is weight. Teardrop caravans are great when small but are less attractive and practical as they get larger (see pic)At all times I must keep in mind the tare weight at 600-650kg. ATM 850kg which is all my JBA car can tow.

Based on my current 450kg tare van I have made I know that 650kg is achievable with weight loss on some materials that I didn't use in my current van. Some use of balsa, polystyrene on the walls with epoxy paint, lightweight ply, PVC boards for ensuite walls, space saving size spare wheel on the rear with wire spokes and so on. One of the main issues I had building my current van was that you don't know the tare weight until you put it over the scales. Things like welding rods, bolts, solar panels and battery all add up. A 13" wheel and tyre weighs 17kg but the 10" wheel and tyre on my current van weighs 8kg multiplied by 3 = 27kg savings using the 10 inch wheels. The new van must have 13" wheels though as it has to have brakes and is too large for 10" wheels. So, in conclusion, yes you are right, shape is important, (even my fairly streamlined front has a good pitch but flat rear wall) but I'm handcuffed to a point.

I've given up on the wind power as previously advised on this thread. The inverter/smart charger will do for that for the time being and a DC-DC charger down the track.

 

-- Edited by Eaglemax on Saturday 18th of August 2018 11:02:44 AM

-- Edited by Eaglemax on Saturday 18th of August 2018 11:03:22 AM

Quote Peter_n_Margaret:

When batteries are charged or discharged, there is a chemical reaction going on. The rate that the chemical reaction takes place profoundly influences the rate that the battery can be charged or discharged. Several factors will affect the rate of the chemical reaction.

Yes, chemistry does make a difference. Lithium has a high charge acceptance rate compared with lead acid generally and maintains it to higher states of charge, but it needs to be managed to avoid overcharging and to avoid cooking the alternator.

There are also differences in the acceptance rates of lead acid batteries, depending on their construction. For instance, LA battery designed for cranking has more, thinner plates than a LA battery designed for long life cycling, so it will also charge and discharge faster (due to having the electrolyte in closer contact with the plates), but not last as long.
Even AGMs come in fast and slow recombination types. Those used for RVs are typically slow recombination styles to give maximum life (and therefore lower cost per kWh (or Ah) delivered).

Ummm....... In an attempt to correct quite a bit of mis-imformation I'll try to explain the way the different types of battery actually work

A lead acid battery requires a chemical reaction to create a voltage differential and that required energy and in the case of a lead acid battery that energy is in the form of electrical, heat energy is a by product along with electrolysis and these all waste some of the generated electrical energy. Lithium does not use the chemical reaction method but rather the lithium ion transfer method. The chemical state of the anode and electrode remain the same but the lithium plate becomes lithium ion depleted, but not lithium ion stripped, while the graphite plate has lithium ions attached onto its outer structure, but they never become part of the graphite so no actual chemical change occurs.

This is the reason for the difference in acceptance rate and release rate in lead acid batteries compared to lead acid batteries, lithium batteries do not require the slow chemical reaction to accept or release electrical energy, they simply move lithium ions into the electrolyte from one plate surface contact and out into the other plate surface so there isn't even the travel time through the electrolyte ...... think of that swinging ball thing where a ball strikes one end of the row and a ball swings out the other end, same sort of thing.

 

 

As far as the thick and thin plates, lithium batteries have this effect as well. Nothing to do with the electrolyte being a closer contact with the plate but everything to do with the thickness of the material the chemical reaction needs to penetrate in the case of a lead acid battery and the distance the electron needs to pass through in a lithium battery. Because a faster discharge rate and charge rate can occur in a thin plate lead acid battery it is not suitable for the AGM type of electrolyte retention but generally requires the flooded cell method so it can have its water loss through electrolytic action replaced on a regular basis. 

Lithium batteries also come in the very fast discharge type just like lead acid batteries and this rate can be up to 30 x the Ah capacity, 30 amps from a 1 Ah battery, great for model planes etc but useless for an RV so just like lead acid batteries it's a case of horses for courses. Neither lithium or lead acid batteries with thin plates last as long as those with thicker plates, the fact a chemical reaction needs to occur in a lead acid battery means the material is eaten away till there is none left and the heat generated in a thin film high discharge lithium battery destroys the electrolyte and it coats the plate surfaces and reduces the discharge and acceptance rate.

This is the reason why lithium batteries no longer suitable for electric vehicle use still function quite well as house batteries, the charge rate and discharge rate are not as critical nor is the pack size as critical or the voltage requirement, so reconfiguring a 144v 48 cell battery to build a 24v or 12v battery means far less current per cell from each unit makes up required total amps.

 

As for recombining being fast or slow in AGM batteries, this is to do with the units fitted into the top of each cell that recombine the hydrogen and oxygen back into water. This is because of the electrolytic action that occurs in a lead acid battery when charged or discharged, we have all seen the bubble in a flooded cell battery and this occurs in every lead acid battery, AGM batteries just recombine it so they loose less electrolyte compared to flooded cell batteries like the average starter battery.  This process does produce heat as does higher voltage charging, so a slower recombination unit and lower recommended charging rates are used where heat is problem like in Australia. Where it rarely gets warm by Australia standards heat is not a problem so they can use faster recombination units and higher charge rates and the cell temp becomes a critical factor.

 

As far as temp affecting charge rates, certainly in lead acid batteries but unless the temp drops below -20*C or over 60*C the charge/discharge rates in LYP chemistry lithium batteries is not affect when it comes to house battery use.   

T1 Terry

  

-- Edited by T1 Terry on Saturday 18th of August 2018 02:51:30 PM

Actually Peter it was 14.1 at the battery side of the Solonoid in the engine bay and 14.0 Volts at the house battery mounted on the drawbar. not much drop. Powerful enough to charge the 12 amp smart 3 phase charger I assume (leaving Monday for first test)

 https://www.ebay.com.au/p/Oz-Charge-12v-12-Volt-12-Amp-12a-9-stage-Battery-Charger-REDARC-Projecta-AGM/865911178?iid=271970942506&chn=ps  

  I was surprised it didn't have much voltage drop but cables are fat

Pete . I just left it up to the regulator . It worked hell fine for the 5 years I had it . Assume it was 3 or 4 years old batteries when I bought it Why worry if it works ? They work in our cars etc I donât go debating them ? Only issue if your relying on alternator ONLY you need to start or travel for a few hours each day . Some are happy with that ? Canât beet a couple of good solar panels !!