Batteries for small solar (really small)

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Batteries for small solar (really small)

Postby 11.5 volts » Thu Nov 10, 2011 5:42 am

Hi

I am still looking for a particular solar panel to directly use a 12 volt frypan without batteries.

In the meanwhile, I have been looking at small batteries between (say) 4 AH and 15 AH.

This is for things like camping (though have not been for a while), BBQs and even using at home plus for using if the power goes out (very rarely) with occassional 12 volt appliances.


I currently have a cheap AGM 7.2 AH battery that is not quite enough for me though is about as heavy as I want (to carry anywhere).


I will get larger batteries as well but am really just experimenting I guess.


Anyway, Gordon suggested Nimh or LiPo.
I love Nimh AA batteries but for patent reasons (I think) what I want is not available.....mostly what is available for 12 volt are AA or similar stuck together in heat shrink packs.

I do not think I like the idea of LiPO but I do think LiFePo4 might be what I need.


From what I read, in fact I think most vehicles will be powered by LiFePo4 batteries in a few years and would not surprise if they are not powering ..well....almost anything in a dozen years or so (Unless something even better comes along). They are not quite there yet for most purposes (too expensive and need a mangagement system for anything of size). For my purposes though may be ideal.

Has anyone used LIFePo4 baatteries without a management system for small scale solar?

I am looking at things like small Shorai, Ballistic, K2 energy and maybe Tenergy LiFePo4 variants.

Most are labeled as motorcycle batteries....advantages.... MUCH lighter, supposedly last much longer (IF you follow the rules), charge much faster (I think...this would be a huge plus for me), is "made" for what i want...IE a fairly large constant current draw (comparatively) for a few minutes.

Are the only issues...not overcharging (voltage) and not "killing them" flat?
My 50 watt panel with no name regulator SHOULD be okay to charge without issue? (says voltage to stop charging is 14Volts)....would that still apply for such a different battery?

A Ballistic 12 volt 4 AH (equivalent???) LIFEPo4 battery weighs UNDER 200 grams?? Maybe not quite enough juice without me getting very nervous about killing it but would recharge in very quick time.


I will be buying various LiFePo4 batteries over the coming months but was curiosu if any are used for small solar already and what should I start dabbling with?
Towards the upper end of what I want some have a management system built in I think.
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Re: Batteries for small solar (really small)

Postby Tracker » Sat Nov 19, 2011 7:14 am

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11.5 volts wrote:I am still looking for a particular solar panel to directly use a 12 volt frypan without batteries.

Dream on :!: :!:

The request almost does not warrant a reply, because it's so silly.. SORRY :!:

A "Fry-Pan" uses 1000 to 2000W of power to heat, so nothing "SMALL" can provide that amount of power

It's like saying that you want to fill an olympic-pool and you want a small bucket to do it with..

Were you serious, you would be looking at solar-concentrators to directly heat the pan. It is entirely practical to consider that solar insolation values of 1000W/M2 are readily available, so if you can concentrate that power (ie focus) then you might be "cookin with gas"..
((That 1000 is for the light intensity, not the heat.. I actually don't know what the HEAT content /M2 would be))

My 50 watt panel with no name regulator SHOULD be okay to charge without issue?

You really are fooling yourself.. Run a frypan from a 50W panel?.. IF you had sufficient battery capacity, you would be charging for 400hours to run the pan for about half an hour..(with all the charging losses)
..
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Re: Batteries for small solar (really small)

Postby 11.5 volts » Sun Nov 20, 2011 7:33 am

Sigh!


If you read the other post you would know that I already HAVE a 12 volt frypan.

You would know that a 12 volt frypan uses LESS than 200 watts and cooks quickly.


Works better with the lid on but can use as LITTLE as 20 watt hours to cook a small meal. Better to use small chunks and the pan is only six inches.


I am ALREADY regularly cooking meals with that 12 volt frypan and a 7.2AH agm battery charged from my 50 watt solar panel......and that is with the panel in my window facing west and only getting a few hours sun a day. As it is i can get about 3 uses in two days....if i took the panel into the sun I could use it twice a day most (summer) days...maybe sometimes even 3 times. If I got a human powered generator I could easily charge the battery enough for three meals a day (solar and pedalling/winding depending on the generator).


That 7.2 AH battery is ok but i would like a bit more juice AND like it it be lighter....hence this thread and my interest in LiFePo4 batteries.

As to direct powering a frypan....my problem is NOT that I will never get a panel big enough...it is the voltage is too high from most "12 volt" panels...plenty of panels give enough current.....I just can not get one that gives the current I want at the right voltage (and at my price range). Lots of people will sell me the bits to make one but I just want to buy one.

All I want is a panel that puts out 15 volts (should do so it can still charge a battery) at around 160-180 watts.
THAT will power my 12 volt frypan.

A self regulating panel could be used to supply lots of resistive type loads.....maybe a small heater for a few hours a day (there are 150 watt heaters)...not much but for someone it may mean a huge difference and a directly powered frypan could be great for BBQs and for camping but also for poor people and homeless people. Is quicker (in many cases) than solar ovens plus I can sit in my lving room and cook from the panel in the window.
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Re: Batteries for small solar (really small)

Postby 11.5 volts » Sun Nov 20, 2011 8:22 am

I am using my stove and large frypan right now. I am not using my 12 volt one and battery today because....



The meal I am cooking inlcudes large thick steaks....would take far too long with my 7.2 AH battery (which is really much less with this current drain).

If I had a panel to power it directly this would no longer be an issue.


it is also overcast and wet....that WOULD be a issue still.

for BBQs who has one on a wet day anyway?
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Re: Batteries for small solar (really small)

Postby Tracker » Sun Nov 20, 2011 8:56 am

11.5 volts wrote:I am still looking for a particular solar panel to directly use a 12 volt frypan without batteries.

Sorry, but I am not going to hunt around to other threads to find out basic information for was seems a pretty dumb question.
So, having discovered that we are talking about a 200W frypan (which simply CAN'T work as well/fast as a 240V/1000W pan), then you have answered your own question.
The maths is simple.. a 200W pan needs a 200W panel and then you need to cater for "Lesser Conditions", so probably 400W of panels.

Anyway - whatever rocks-your-boat or butters-your-biscuit - Sounds like your cookin-with gas.
..
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Re: Batteries for small solar (really small)

Postby 11.5 volts » Sun Nov 20, 2011 12:46 pm

Tracker wrote:
11.5 volts wrote:I am still looking for a particular solar panel to directly use a 12 volt frypan without batteries.

]

Thats Ok you would much rather jump in and ridicule someone with what seems an even dumber answer (that has nothing to do with the question asked) instead of actually reading what you bother to reply to. The bit you quoted was a lead in to a thread about batteries with reasons.



I do not know of any 12 volt fry pans that use 2000 watts or any of the figures that you claimed ....most of them are less than 200 watts. Road Pro ones are about 140 watts...mine is between 140 and 180 watts...dunno what it is exactly..If I was talking about a 240 volt fry pan I would have said I am still looking for a panel to directly power my 240 volt fry pan.

So, having discovered (HOW??) that we are NOT talking about a 240 volt frypan (which is not THAT much faster than a 12 volt pan), we would have realised the question WAS answered in the other thread


More "assumptions" and was not a question in THIS thread ..You of course made assumptions that where wrong...plus the question HAD pretty much already been answered about directly frying from a panel...I will be trying a number of ways in the coming months and reply to that thread..with my success and failures.

A 12 volt frypan works very well for frying foods in normal time.
Using small pieces and the lid on and there is not much difference to any other frypan with the limiting factor being the battery capacity....with unlimited capacity there is no difference other than the small size of the pan...still enough for a decent meal for one or ok lunch for two.




And again, that actual question was in another thread...this one was about batteries to use while i find the right panel.
The maths IS simple.. a 200W pan needs a 200W panel OF THE RIGHT VOLTAGE.

I AM contemplating just trying any "12 volt" panel with enough amps but that means a 210, 220 or 240 watt panel or two smaller panels but they are all in the 17 to 18.5 volt and MIGHT fry the frypan....so the panel I WANT is a 15 volt 180 watt(ish) one and they are not made that I can find.

Back to the question of this thread......to anyone who is interested in my dumb questions, Has anyone use a 12 volt motorcycle LiFePo4 battery with solar panels?

Thats enough on this for me.....unless someone wants to give me a heads up on LiFePo4 batteries.
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Re: Batteries for small solar (really small)

Postby Gordon-Loomberah » Sun Nov 20, 2011 1:22 pm

11.5 volts wrote:...so the panel I WANT is a 15 volt 180 watt(ish) one and they are not made that I can find.


True, but Vmp ~30V panels and DCtoDC voltage converters that will halve the voltage are made. In any case, a panel with Vmp ~18V will not deliver 18V into a suitable fixed load. It's related to MPPT vs PWM charging controllers... an MPPT CC will operate the panels at the MPP voltage, but a PWM CC will only operate them at the battery voltage, you just lose ( (Vmp - Vbatt) * current ) watts. I think thats what will happen with a panel directly operating a sufficient load, the voltage will drop below Vmp. (See your other thread for my thoughts on regulating that by adjusting the panel pointing and monitoring with V and A meters.)
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Re: Batteries for small solar (really small)

Postby Tracker » Mon Nov 21, 2011 10:05 am

Gordon-Loomberah wrote:It's related to MPPT vs PWM charging controllers... an MPPT CC will operate the panels at the MPP voltage, but a PWM CC will only operate them at the battery voltage,


Well there you go - I have learnt something - I think --- Thanks Gordon..
I had understood that the MPPT process, maximised the Power from the Panel , and then PWM-CC maximised the the charge to the load.. ie.. in much the same way as a switch-mode supply just manipulates the consumed power for the need (to use simple thoughts). I must be getting OLD... :oops:
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