Cheap 53V panel to 12v bat charger

[Treacle boy]

Hello one and all,

I am currently working building a shed to process Waste Veg oil in (for use in a car in case you had'nt guessed!). It will have a drain back solar thermal system to pre heat the oil and thats about it, I need power to run the 12v coolant pump and solar controller for this panel. I also need power to run a LED lighting system - I have not put any windows in to minimise heat loss in the winter!

I have 2 Antec thin film PV panels, here's the spec for the new ones (I've got the old 36W versions):

http://www.antec-solar.de/antec/cms/upload/pdf/DatenblattATF43.pdf

So that gives me approx 70 watts of charging power, problem is they operate at 53v at their MPP and all my electrical gizmos are 12v.

I don't want to buy an expensive solar controller because it is a tiny system, the only way i have thought of doing it is to connect 4 12v batteries in series and connect them via a schottky diode to the 2 panel array. This should give them some kind of charge. Then to use a voltage controller 48v to 12v to run my equipment. Does this sound workable? Am I going to get massive losses somewhere - if that is possible in a 70Watt system!!!

Any advice appreciated.

cheers,

Jim

[ghurd]

I would really think about other panels.  Could be cheaper. Certainly simpler.

The 4 batteries to replace every few years, an expensive DC/DC converter (and it's losses), maybe a charge controller, etc...

It seems like a lot of money and efforet to use a small PV because it happens to already be there.  Guessing both together only make 1.3A.

The money saved on 3 extra batteries, converter, battery cables, 48V controller (if needed) would go a long way on another panel.  

Plus, the PVs could be sold to someone on the board already using a 48V system. Might get enough to buy a 45W HF kit, when a good coupon is out.

The panel sounds kind of marginal for a 48V system, with 53V at peak power.

That's 13.25V per battery before any voltage drop for wire or a diode.

G-

[kurt]

mite look into a small mppt charge controler if you have the panels already that would take the high volts from the panels and convert it to 12v charging voltege for you. just look at the imput voltege of the one you get make sure it is high enuff for the panels you have. that way you could use a 12v system and be all set.

[Bruce S]

Jim ;

 With the high voltage you could google < 60V voltage regualtor> that will get you close. The invaluable LM317 has a high voltage one , but better to look at the LM29xx series they have much higher handling. Also going with MPPT is a very good way, can be built from plans already here.

On heating the oil, ( I currently do not use solar but have built a small imersion based heater using 12Vdc coffee cup heater, but do charge the batt pack using a PV) make sure you have some type of thermistor so that the oil doesn't go in until the panel has arleady hit ~85F otherwise it will take forever for it to get up to water cooking temps. too long and the oil will try to go rancid <:-(>

Would enjoy seeing your setup.

What vehicle are you fueling? and what type of oils your looking to process.

May small test batches are with KOH and HEET.

I'm a little lazy in that I have a lady making 20 gals and charging me $2.00/gal , I'm using a level of B50 in a 300D.

Cheers

Bruce S

 

[Opera House]

I'm not offering to support you on this.  If these were mine, I would put the panels in series and modify a PC power supply.  Typical power supplies will have the TL494, switching transistor and transformer.  These chips have input for dual control.  Use one to set the power point and the other the max output voltage.  I'm really fond of some of the HP laptop 17-18V power supplies.  These have an opto isolator and a zener to control output voltage.  Change the zener and you have whatever voltage you want.  Two or three of these could run in parallel.

[Ungrounded Lightning Rod]

On heating the oil ... I ... have built a small imersion based heater using 12Vdc coffee cup heater,

Good grief!  The first time that comes on half-covered you'll get an oil fire, or even an explosion.

In your place I'd either use pipe wrap heating elements and insulation around the tank or use the immersion heater to heat water in an external container and circulate the hot water through a pipe in the bottom of the oil tank.

[Bruce S]

ULR;

  Do not worry. This is only to get my feet wet so to speak. I NEVER leave this stuff alone. Should've said that part too, my bad:-<.

Heater is the looped flat type and is connected to a stainless steel bowl were to oil sits inside a different container that has a glass lid to watch for proper heating to remove latent water before ever moving on to the next step, even then the oil has been allowed to cool and such.

I like having all my fingers, toes and limbs right were they belong.

Thanks for pointing out the HUGE misteake by leaving those parts out.

I decided to use DC-volt heaters were I can control things.

Bruce S

[Treacle boy]

Thanks G (and everyone else for that matter),

I think I will just bite the bullet and fork out for a new 50W panel suitable for charging a 12v system.

The panels I wanted to use are part of a 20 panel set that I bought a few months ago; they are the ones which got cracked (one side only) during transport, I don't want to throw them away so I am just looking for a good use to put them to. If you know of anyone who needs them let me know.

thanks for the advice.

Jim

Reading, U.K.

[powerbuoy]

Jim:

Where did you purchase the antecs from and what is the going rate?

Thx in advance,

Powerbuoy

[RCpilot]

Check out a BZ Products MPPT 500 Charge Control. It's $195. I use one. it's Rated at Max 500 watt input, 100 volts max input, 45 amps total input and 12, 24, 48 volt operation. I purchased mine here: http://www.partsonsale.com/bzproducts.html It should work fine for your setup and , if you ever expand it will be ready. It's a bit of overkill for your setup but it's not that expensive like a Xantrex or similar.