how to determine what size deep cycle battery i need for camping

How long will my RV battery last?

If yous take a Camper trailer, Caravan or other RV and you lot like to spend time abroad from a 240 volt power source, this commodity will requite you some answers that the sales people avert. It will allow you to estimate the size and number of batteries that will adjust your camping.

As always there is a little explanation required to ensure that nosotros are at the aforementioned starting signal. The aim is not to make it complicated, simply to explain it and then it makes sense.

A blank calculation sheet tin be downloaded from the end of this article, even so nosotros recommend you spend a few minutes reading why and how it works.

Come across besides a related commodity: "Everything you demand to know about installing solar panels."

How will we measure ability?

The corporeality of electricity used to run a device or apparatus may exist defined every bit watts or as amps. If y'all know one you tin calculate the other, provided yous know the voltage.

We want to deal in Amps, as that is how the Deep Cycle batteries are rated. It is widely accepted at this phase that Deep Cycle batteries are the best option for RV use. We recommend the AGM way (Absorbed Glass Mat) as the best for whatever Recreational Vehicle, but you lot tin inquiry this more if you want.

A 100ah battery should provide 1 amp for 100 hours, two amps for 50 hours, three amps for 33 hours etc. It would be nice if this equation held truthful all the mode up to 100 amps for one 60 minutes, but there are some limits to the maximum charge per unit of current draw, and how much of that 100amps you lot can actually use without destroying your battery. Nosotros will go to those later on you lot understand a few more things, just for now we want to know how many amps stuff uses.

Below: A simple instance, but heavy user of power is a 12 volt hair dryer rated at 10 amps. A 100 ah battery should give you (100/10=ten) x hours of usage.

If you use information technology for 5 mins a day, information technology could last 120 days. Happy married woman, happy life.

---

If a device specification does not include amps but does include watts, the formula you need is:

Watts / Volts = Amps per hour

Beneath: An example where nosotros need to summate the amps. A very modest user of power is a 1.two watt LED low-cal running on a 12 volt power source will utilize 1.2W / 12V = 0.1 amps. Therefore a 100ah (amp 60 minutes) battery will final for grand hours.

---

A slightly different example is a 60 watt fridge running on a 12 volt power source uses 60 /12 = v amps, but only while the motor runs.

60 watt fridge ....divided by....12 volt battery....uses 5 amps of electricity (when running)

Merely....the fridge motor does non need to run all the time, in fact this model indicates it but needs to run about fifteen% of the fourth dimension. 5 amps by fifteen% = 0.75ah/h. This fridge can operate over a period of 133 hours, or 5.v days if the guidelines** are meet.

**Guidelines may be exceeded or not reached. For example this chest fridge used at Thredbo in winter may last 300 hours, only in Darwin in summer only 72 hours if you lot keep exchanging the beer!

How many Amp Hours do you actually get from a 100ah battery?

Amp Hours (ah) is the rating used past Deep Cycle battery manufacturers as a way to compare batteries, just nosotros cannot just measure how many Amp Hours are left in a bombardment. Nosotros tin use a voltmeter to go the voltage, and this can exist used to get a good approximation. Yous need to know a few things first.

i) Low voltage cut off

Get-go, yous cannot apply 100% of a battery for anything useful. To understand this, look at the post-obit chart comparison a conventional Wet Cell battery and an AGM bombardment where the voltage reading shows approximate charge left.

Figure 1: Voltage indicating charge left.

If yous accept a 12V battery system, and so 1 of the almost useful items you can have is a Voltmeter. An constructive one we sell is shown below. It plugs into a cigarette lighter socket and shows the voltage of your batteries. If you already have a multimeter it volition also piece of work.

When you have finished charging your battery yous may go a reading well over 13 volts, however this will be a surface charge and volition settle to a existent reading of around 13 volts in an AGM battery or 12.6 volts in a Wet Cell battery. If you have a small load on your bombardment, say a couple of lights, the reading you become from your voltmeter when compared to the table or chart to a higher place, will show approximately the remaining bombardment charge. A moderate or heavy load will give a distorted reading until the batteries have rested and the charge equalises.

Looking at Figure 1 above you will notice that 12.1 volts AGM, or 12.1 volts for Wet Prison cell indicates you have used 50% of the capacity of the battery, you should have fifty% remaining.

However, once you lot go to around 30% remaining the voltage volition not be sufficient for most appliances, y'all may go a light to piece of work but your h2o pump volition non work very well. Using a battery below these levels will besides severely reduce the number of recharge cycles you get from your bombardment.

Battery chargers like the SETEC (at that place are others) command the current describe from the bombardment likewise as charging the batteries. These will preclude y'all cartoon electric current from the batteries one time the voltage drops beneath the ideal minimum level.

Well-nigh battery manufacturers point you will get the longest life from a battery by only discharging to l%. This mayhap the ideal case, but in an RV when you take to purchase an actress battery, discover storage space and pay for vehicle fuel to cart extra batteries that weigh about 30kgs each, I believe it is non unrealistic to allow for discharging to 40% or fifty-fifty 30% on those longer stays or when your other charging options don't piece of work out. Yes, you may need to supersede your battery a year before, but you have made savings along the way. Just one night away from a caravan park volition save $thirty plus actress weight for always kilometre y'all travel.

Again it is of import to note that the voltage shown will but be authentic if in that location is at to the lowest degree some load, but definitely not a load exceeding 5% of the batteries capacity. If the battery has simply been charged or heavily discharged, information technology must be given time to equalise earlier taking a reading.

Using a water example, imagine half dozen tanks of h2o (like 6 cells in a battery) each joined together with a harbinger. If y'all fill one end tank using a garden hose or drain the other terminate using a garden hose it will take some time for all tanks (or cells) to be at equal levels.

The time it takes to equalise is something you volition get used to, you certainly don't panic if your voltage drops down while you utilise the microwave for a couple of minutes (inverters can swallow quite a fleck of power while in employ). A low load that is drawing power no faster than the battery tin equalise volition give a reasonable value for the Charge remaining, by reading the voltage.

Be aware also, that a battery under no load at all may notwithstanding show 12V, but have little or no amp hours left.

In that location are a few avant-garde gauges that will calculate your capacity based on actual contempo usage, only the cost is still across virtually recreational users. They are more like a mini estimator taking and recording sample data and making predictions of capacity remaining and how long it will concluding if yous continue to utilise it at the present rate. Run across Below:

Other more economical voltmeters are shown here:

2) Battery Type

Every bit can be seen in Figure one the battery blazon e.m. Wet Cell, Gel or AGM can requite unlike voltage readings for percentage of charge left. While the volts is indicative of how much power is left, information technology is not similar a fuel gauge. Petrol left in a fuel tank would bear witness up equally a direct line from xiii to zero in the chart above.

The AGM Deep Cycle battery plots closer to straight than the Wet Cell battery. They accept charge easier and faster than moisture cell batteries. They are able to recover better from a lower belch. Aye, they cost more than Moisture Cell batteries, only with correct usage can terminal twice equally long.

Not anybody will benefit from using deep cycle batteries. If your predicted usage is much lower than would be supplied by these larger AGM Deep Cycle batteries, information technology can be a cheaper choice to employ a Moisture Prison cell bombardment. If you get out 240V for but one or ii days at a fourth dimension, and you employ only LED lights and say a water pump, you should manage quite well with a cheaper Wet Prison cell battery.

Caravans Plus does not sell Wet Prison cell batteries as these are harder to ship and are readily available in most locations. Moisture Cell batteries need to be upright and located in a ventilated area that is not in the living area. AGM batteries are completely sealed and can be used at whatsoever angle. They can be placed under your bed without take chances.

3) Excessive Describe Rate

Battery chapters decreases equally the rate of belch increases. Batteries (say 100ah bombardment) accept been tested at a given discharge rate of 20 hours.

That means a constant use of 5 amps an hour for 20 hours (five x 20 =100). The specifications should signal this.

The bad news is that if you exceed that discharge rate quoted you will encounter a meaning drop in capacity. If you lot need more than than 5 amps per hour y'all should consider having two or even more batteries.

The good news is if you lot apply less than the 5 amps per 60 minutes, you tin get more the quoted 100ah.

Figure 2: Battery capacity decreases as the rate of discharge increases.

iv) Getting Less Than A Full Charge

When charging your batteries from a good battery charger over a number of days, you tin can go to 100% charge. Yet a vehicle alternator will merely manage to get to around lxx%. Also if you are charging your battery from your solar panels, you need to ensure your solar regulator is upwardly to the job.

Voltage drop is one of the biggest problems in getting the bombardment in your Caravan or Camper trailer fully charged from your vehicle alternator. Y'all can never accuse the battery more the voltage that reaches information technology through the copper cables. The longer the cable, the more the voltage drops. This tin can be compensated to some extent past increasing the cable 10-section but even this has limits.

With your trusty voltmeter you can cheque what voltage your alternator is producing by starting your vehicle and connecting your voltmeter to the battery terminals. Ensure electric accessories are Non switched on. This should read from thirteen.8V to fourteen.8V.

Figure iii: Less charge due to voltage drop

Side by side test your voltage at the rear of the vehicle with the engine still running. This may exist 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.one of a volt.

Next take a reading where the auxiliary cable goes to the RV bombardment (or battery charger). My caravan has lighter wiring and the voltage loss was another 0.4 volts. The full voltage driblet was 0.5 volts. When you look dorsum at Figure i, you will meet that a reduction 0.5 volts pushing a accuse into your RV battery can severely reduce the total usable amps until yous top it upwards over again.

There are two solutions to this problem. First you tin can increase the size of your copper wires so that the voltage driblet is less. Second you can add a voltage booster that volition step up the voltage to compensate for the loss. This must be placed between the alternator or vehicle bombardment and your RV battery so that electric current coming in will achieve the bombardment at a higher voltage and thus increment the speed of charging and get more than amp hours into that bombardment.

Effigy 4: Increase amp hours stored with a booster

When all the in a higher place is taken into account you volition withal only become about 70% of your battery capacity as usable ability when charging from your alternator.

When combined with manufacturers recommendations to get the almost life out of your bombardment by discharging regularly to around fifty%, then equally a dominion of pollex you will demand twice the amps hours that yous will calculate next. This rule of pollex allows for greater belch on occasions, e.grand. lower solar input or longer stays than normal or greater usage of 12V appliances. If you don't desire this buffer and then lxx% usage will be the maximum you lot can utilise and any backlog volition greatly reduce your battery life and not operate all types of devices.

Calculating Your Amp Hours

Examine the following chart to calculate the number and size of batteries you will need. You can download a bare calculation form and enter your battery size to make up one's mind how long it will last.

Notes explained:

1) The h2o pump has a rating of 5.2amps, I estimate it runs for near 12 total minutes per day. 12 mins is ane/v or 0.ii of an hr.

Three refrigerator options are provided, select one.
ii) The gas fridge has a 12V fan that comes on when needed, estimated half dozen hours per twenty-four hours, selected here.
3) The upright compressor fridge has a quantity of 0 (aught) so it is non used in this calculation. It uses too much power.
4) The chest fridge would be a suitable refrigerator for a camper trailer just unselected for these calculations.
5 & 6) Would be optional when power gets low.
7) We practice non utilise a TV when camping, but some people may. They practise utilize more than than you retrieve.
8, 9 &10) Are all LEDs and are very power conservative. The specifications for the LEDs were provided in watts so they are divided by 12V to gets the amps/h.

21) But having an inverter switched ON uses power. Switch off when not required.
22 to 25) All essential 240V appliances for some softies. The watts need to be divided by 240V to get the amps/h needed for our calculations.

When the amps/h for all devices are added upwards nosotros detect nosotros use around 13.5 amp hours per day.

Annihilation in the amps column that exceeds five amps will crusade your battery to deteriorate very quickly, then I've elected to become for ii batteries.

This gives me ample capacity. Information technology is only the inverter extravagances that have taken me over the limit, and then for many people a single AGM 100 to 120ah battery volition be enough unless you lot have an upright 12V fridge, or need your TV when away from ability.

You can download an Excel sheet or OpenOffice Spread Canvass to fill in your values.

See as well a related article: "Everything you need to know about installing solar panels."

Was this helpful?

alcantaracyricionsien.blogspot.com

Source: https://www.caravansplus.com.au/guides/calculating-how-big-your-battery-needs-to-be-a-44.html

Share this post