Selecting The Right Cable Size For Your Battery Bank
Are you putting together a battery bank for an alternative energy system? Or just wondering what gauge wire to connect 12 volt batteries?
Maybe youre trying to determine the correct size of interconnecting cables between the batteries themselves and the charger / inverter.
How big should the cables be? What size? More accurately, what gauge ?
Read on or go straight to the chart at bottom of page.
I recommend getting yourself a clamp meter that measures DC current! This will help verify whats actually going through your cables! The most popular and reasonably priced clamp meter is this one
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Choose The Right Charge Controller Size
Your charge controller should be compatible with the amperage and watts going through the system. If you have a 20A 240 watt system, your charge controller must be able to match that. If you are running a 240 watt solar panel, you need at least a 300W capable charge controller.
There are two types of charge controllers, PWM and MPPT. PWM is the standard and works fine for most solar panels and batteries. MPPT charge controllers are more accurate and can handle greater power. But they are also more expensive. For charging a 100ah battery however, a 30A PWM controller the should be fine. Our choice is the EEEKit Solar Charge Controller as it does the job without any fuss.
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Difference Between Regular Car Battery And Deep
Lead-acid batteries can be classified as deep-cycle, also known as leisure or marine batteries, and car batteries.
The internal structure is designed so that they deliver current in different ways. Deep-cycle batteries can supply low-to-medium, steady currents for some hours, while car batteries can supply hundreds of amps for less than a minute.
They also differ in the amount they they can be discharged. Deep-cycle batteries can be discharged regularly up to 50% and now and again as far as 80% of their capacity without damage.
Car batteries shouldnt be discharged much more than 15% lets say 20% maximum.
How Do Solar Panels Work
Solar panels work step by step. A solar panelarray made by photovoltaic cell which have a crystalline structure held together in an ordered by N-Type and P-Type silicon.Step 1: solar panel start its work when Sunlight hits a Photovoltaic solar cellStep 2: : An electron of solar cell move from N-Type silicon to P-Type Silicon, which causes generate DC ElectricityStep 3: The electricity flows into an inverter or stored into direct Battery for next use.
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How Long To Charge 12v Battery With Solar Panel
How Long To Charge Battery? In most cases, a solar panel 12v battery charger that produces 1 amp of current takes 5-8 hours or more depending on the Sun hour. To get the most effective charging by a solar panel, you have to maximize the amount of current by keeping the board pointed directly to the sun.
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Deep Cycle Battery Faq
The links below are on this page – you can also just scroll down if you want to read them all.
This entire page is copyright 1998-2014 by Northern Arizona Wind & Sun. Please do not use without prior permission.
- Gel Cells
- AGM Batteries
- Charge Controllers
- Mini Factoids – Some small facts about batteries
The subject of batteries could take up many pages. All we have room for here is a basic overview of batteries commonly used in photovoltaic power systems. These are nearly all various variations of Lead-Acid batteries. For a very brief discussion on the advantages and disadvantages of these and other types of batteries, such as NiCad, NiFe , etc. go to our Batteries for Deep Cycle Applications page. These are sometimes referred to as “deep discharge” or “deep cell” batteries. The correct term is deep cycle.
A printable version of this page will be available in Adobe PDF format when we finish updating this page for downloading and printing: Most of the charts have small images for faster downloading. To see the full size picture, just click on the small one.
What is a Battery?
Part – or most – of the loss in charging and discharging batteries is due to internal resistance. This is converted to heat, which is why batteries get warm when being charged up. The lower the internal resistance, the better. There is a good explanation and demonstration of Internal Resistance here.
Types of Batteries
- Starting: 3-12 months
- NiCad: 1-20 years
How To Calculate Which Size Solar Blanket You Need
We have uncovered some things you may not have known about solar, the ‘4C’s of solar’, and the benefits of choosing solar over a generator. So now you have all that knowlegde in your arsenal, you’re probably thinking ‘this is all very well and good, but what solar blanket do I need?’.
In order to answer this, we need to take a step back and I mean go way back – back to when you decided ‘yes I’d love to go on a camping travel adventure and take all the home comforts as well’.
Numero uno: Decide which electronic items you are going to take with you. If you’re all about the simple life, this could be a 12v portable fridge and maybe an LED light. Record how many amps each of these appliances/gadgets draws over a 24 hours period. Tally them all and presto, you have the total amp hours you will likely use over any given day.
Numero dos: Determine the battery size bank you will take with you. This is determined by the appliances/gadgets you will take with you. A fridge and LED light for example, may only require a 120Ah deep cycle battery – but your mileage may vary. Go speak to a battery specialist to see what’s best for you.
And here’s a quick tip: We don’t recommend to discharge your battery anymore than 50% a day. This ensures best battery life. So that 120Ah battery you have, esentially cut the useable amount by half.
But seriously who has time for that?
We laid it all out for you in this video, so you dont have to.
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Does It Matter What Kind Of Battery You Use
There are three main types of deep cycle batteries used in RV solar systems, as discussed above. Each type of battery varies compared to cost, battery rating, output voltage, and life span.
These factors determine the amount of energy stored, how efficiently it can be used, and how many times a battery can be charged before losing its efficiency. So yes, it is crucial to make the correct choice of battery.
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By combining Rockpals 80 watt solar system 12v with battery based generator, You can have a Awesome small home power system.
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Measure Your Power Usage
It consists of taking the wattage of your devices and adding them all together, considering their approximate daily usage. This exercise will provide you a baseline about the amount of power youll need daily.
The Solar Calculator by Renogy is a great tool dont hesitate to try it to understand your consumption better.
You can find your different devices power consumption in their manual or directly on their label .
Batteries are rated in Amps. We recommend Lithium-Ion batteries as the best for any Recreational Vehicle, but you can research this more if you want.
A 100ah battery is calculated as providing 1 amp for 100 hours, 2 amps for 50 hours, 3 amps for 33 hours, etc.
But in the perfect world, this equation of 100 amps for 1 hour has its limitations.
How Much Solar Power Do You Need
So you want to set your rig up for Solar but you are not sure what size of set up you need? This blog is designed to give you the tools needed to be able to work out exactly what are you are drawing from your rig’s batteries and what type of solar set up you need. Knowledge is key when setting up your rig for solar so the more information you have on each and every one of those home comforts devices you plan to take away with you the better. If anyone has a question pop it in the comment section below. I will try my best to answer everyone.
How to work out Watts, Amps and Volts
A larger solar panel will collect more energy in less time, but just how big does the solar panel need to be?
The power consumption of appliances is usually given in Watts. To calculate the energy you will use over time, just multiply the power consumption by the hours of use. For example:
10 watt device used over 3 hours equals 10 x 3 = 30 Watt
How to convert Amps to Watts
The energy in Watts is equal to the electric charge in Amps times the voltage in volts:
Watts = Amps × Volts
If your device doesnt have the Watts labelled on it, then it should at least have the input Volts i.e. 240V and the Amps AC it draws such as 240V 1.5A. You can then use the equation Watts Volts x Amps so 240v x 1.5amps = 360 Watts.
How to convert Watts to Amps
The electric charge in Amps is equal to the energy in Watts divided by the voltage in volts :
Amps = Watts / Volts
Do I need a battery?
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Questions Chat With Us
Wil has been a part of the solar industry for over 20 years as an electrician, solar installer, support technician, and more. He’s also been living off-grid since 1996. Wil and the rest of the Unbound Solar team are here to answer any questions you have about designing a system that will fit your needs.
How Do You Calculate A Battery For A Solar Panel
There is a simple formula for deducing what panel size you need for your battery, but this depends on how many hours of sunlight youre getting per day, which, for most cases, we can average out at around six. This simple formula is:
Battery amp hours multiplied by voltage and then divided by daylight hours.
For example, a 100ah, 12v battery would be 100×12=1,200. This divided by 6 hours equals 200. So, if you want to charge a 100ah battery from flat to full in a day, a 200-watt panel in ideal conditions would do it.
Now that weve got a better idea of what to consider when matching a solar panel and batteries, lets take a look at the best panel size for particular battery setups.
Ideally, youll want slightly more power coming from your panel than you need from your batteries, as this will reduce the chance of running out of power and help during overcast days.
Remember, these are rough estimates, like your location and your energy needs will also play a part in the battery and panel size you need. Here are the best panel sizes in general for most common battery specifications.
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Do You Need To Buy A Charge Controller
In theory, you dont need a charge controller. In reality, you should not be without one.
A charge controller will help to ensure that the battery is receiving the right amount of power. It will also help to ensure that the battery is not overcharged by the solar panel.
Basically, the charge controller will help to preserve the lifespan of your battery.
The charge controller is also going to be playing a huge role in diverting power to the battery. Anything that is not being directly consumed by the appliances in your RV will be sent straight to the battery.
Therefore, you will almost certainly need one if you are expecting your solar panel set-up to cover both battery and genera RV usage.
What Does 100ah Mean
It can be confusing if you are new to solar systems.
100ah means that a battery can deliver 1 amp of current at the rated voltage for 100 hours.
AH stands for amp hours, Thus, you get this:
2 amps for 50 hours using a 12 V system.
4 amps for 25 hours using a 12V system.
100 amps for 1 hour when using a 12V system.
To get the wattage for this type of battery,A 100ah battery will provide 1 amp X 12 Volts = 12 Watts for 100 hours.
100 amps X 12V = 1200 Watts for one hour.
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How Long Will It Take For A 24v Battery To Be Charged With 100w Panel
Its now easier to charge your 24-volt battery, and you can do so with only one solar panel. To fully charge a 100-watt solar panel, will require 3.7 hours of direct sunshine.
Using two 100 watt solar panels, on the other hand, it will only take 1.7 hours to charge. The more solar panels you have, the more electricity youll have.
Its important to remember that the type of charge controller you use has an impact on charging time. PMW and MPPT charge controllers will have varied durations. You can choose the finest one for your requirements.
What Is A Solar Charge Controller
Solar charge controller limits and regulates the voltage across the battery terminal to avoid any damage to the battery from the high peak voltages of solar panels. There are other functions of the solar charge controller too, like protecting the battery from overcharging and over-discharging.
Now, there are two types of solar charge controllers available, is PWM based and MPPT based.
MPPT based solar charge controller is far mush advance and efficient than PWM based solar charger, due to which PWM based are not popular.
The efficiency of PWM based Solar Charge controller: 68 to 73%
The efficiency of MPPT based Solar Charge controller: 95 to 98%
I highly recommend only use MPPT based solar charge controller to charge your batteries from solar panels.By using PWM based solar charge controller, you require a solar panel rating will be increased by 30%.
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Getting Less Than A Full Charge
When charging your batteries from a good battery charger over a number of days, you can get to 100% charge. However a vehicle alternator will only manage to get to around 70%. Also if you are charging your battery from your solar panels, you need to ensure your solar regulator is up to the job.
Voltage drop is one of the biggest problems in getting the battery in your Caravan or Camper trailer fully charged from your vehicle alternator. You can never charge the battery more than the voltage that reaches it through the copper cables. The longer the cable, the more the voltage drops. This can be compensated to some extent by increasing the cable x-section but even this has limits.
With your trusty voltmeter you can check what voltage your alternator is producing by starting your vehicle and connecting your voltmeter to the battery terminals. Ensure electrical accessories are NOT switched on. This should read from 13.8V to 14.8V.
Figure 3: Less charge due to voltage drop
Next test your voltage at the rear of the vehicle with the engine still running. This may be at an Anderson plug or the auxiliary wire in the trailer connector. Record this voltage and note any voltage drop. My vehicle has heavy duty cables and only dropped 0.1 of a volt.
Figure 4: Increase amp hours stored with a booster
When all the above is taken into account you will still only get about 70% of your battery capacity as usable power when charging from your alternator.