Will small panels keep batteries charged?

[riff42]

I posted awhile back, on the possibility of getting a 20-30$ charger/maintainer solar panels, will infact keep a battery system (one panel per battery) fresh, when the battery system is only used for LED lighting at night?

Or, are those small solar panels only good for maintaining a battery when it's not really being used (or might take 2 days to charge a empty battery?)

I never really did get an answer.

[wdyasq]

"I never really did get an answer."

What size tires does my car need? BTW, my brother drives a van..........

Well, to get an answer, one really needs to give a bit of information. My information on tire size is about 10 times more than you gave us.... but still as disconnected.

Ron

[wooferhound]

You need to tell us . . .

How many watts of solar do you have or plan

What kind of battery do you have amphours

Exactly how much power will you be using and for how long

Without that information it will be hard for anyone to give you an answer.

But it's all about Watts In & Watts out. If you are charging at 3 amps for 6 hours on a 12 volt system then you will have made 216 watthours or 18 amphours of electricity. There will be some losses from getting the power in & out of the battery. But you should be able to use most of that same 3 amps for 6 hours powering your lighting after dark.

As for charging the battery, Batteries have a Self Discharge rate of less than 1% per day. so if you are charging the battery at less than 1% of it's capacity then you are only maintaining the charge voltage in the battery, but not charging it.

[JamesJackson]

As already discussed, more information is needed.

But there is more. You mentioned that you are going to use the battery to power LED lighting. How much will you be discharging the battery? Are you going to use a Low Voltage Detector (LVD) to disconnect the load (LEDs) if the battery voltage drops below (or to) a specified level? You will need to do this, if you are using a Sealed Lead-Acid (SLA) type battery (or other lead-acid type battery), or else you could damage the battery.

If you are using Ni-CADs or NiMH batteries, you may get away with discharging them to lower voltages (and not having to use a LVD).

So... more details, please.

As for what I am doing... I have a 21-Watt solar panel, a PWM charge controller, and a 12-volt 17Ah battery hooked together. The battery has been keeping up pretty well for over a year now.

I have three 5-watt Hi-Power LEDs hooked up as the 'load' for lighting my living room at night. My LVD board is something that I designed and built, and it works very well.

So - yes. It is possible to design a small-scale lighting system.

This sort of lighting also comes in handy for power outages. You will have lighting - when very few others in the neighborhood have anything to see with.

Regards,

James

[richhagen]

My analogy would be something like:

I have a small gas can, do I have enough gas to drive to my cousins house?

Batteries self discharge.  You will need a charging source big enough to compensate for that and all of the loads that you pull out of it.  Actually a bit larger of a source as you will want an equalizing charge for some battery types.  Generally, the bigger the battery,the more energy is lost to self discharge.  The battery type also affects this.   Rich

[richhagen]

As an example, in Fiji, BThumble has rigged up a few systems with 70 Amp Hour flooded deep cycle batteries, a 10 Watt Panel, a simple controller and an 8 Watt or so fluorescent tube with a 12VDC driver.  They work fairly well if the light is only used for an hour or two per night.  They are of course in the tropics and probably get 6 sun hours or more per day though.  A one or three watt maintainer panel would probably not provide any power in a system like that though as it would be too small and most of the power would be lost to the self discharge in the battery, leaving little to no extra to pull out for lighting.  Rich