Making Sense of Battery Ratings
Let's start by getting familiar with the technical terms and what they mean and how you use them to determine what battery you may want to use in RVs, Camping, Utility and other trailers. We'll refer to them collectively as RVs or Trailers.
Generally, there are two types of batteries to consider: Lead Acid
and Lithium Ion. Lead Acid batteries have been around forever (e.g.
batteries to start your vehicle) and Lithium Ion batteries that are
newer and more advanced in its technology. Each have variations to their
chemical makeup, specifications, currents, voltage, amps, watts and…
well, you get the picture and already know some of the jargon. But do
you what the jargon means and which are most important to know?
In simplest terms, batteries store energy and output power. How much energy and power and at what rates are key things to understand. That means you've got to know some key terms, what they mean, and how to calculate the energy and power flow so you know what you need as you compare batteries.
The basic terms to understand energy and power are:
Volts – the amount of potential energy flow, the amount of electromotive force or potential difference
Amps – the rate of energy flow or current sometimes called a discharge rate
Watts – the power, which is generated or consumed
There are a few other terms like Amp Hour (Ah) and Watt Hour (Wh) that we'll discuss later.
To help understand these terms, let's use something we're all familiar with – water. Have you ever looked at a river or stream? The water flows along at a certain speed and has a certain amount of water in it. How fast it flows depends on a few things like volume, incline, and the capacity of the water source. For example, you can use the water current and volume over time to determine the flow rate in gallons. The current flow rate can be seen if you have water wheel in the river, you can see the effects of the river flow as the wheel turns while water passes through it.
This water flow is like the current and power of a battery. The speed of the river is like the electrical current flow rate or Amps. The water depth or area is like Volts. The river flow in gallons is like Watts. Now, if you measure the current and area of the river for a period of time you'll know how many gallons of water have passed, similar to Wh. How long can this flow be sustained?
Think of a lake at the beginning of the river that stores and feeds
the water into the river. The flow can continue as long as the source
feeding it continues. If you empty the lake by letting out a small
amount of water at a time, it will last much longer than if you open the
gates and let is out rapidly. Similarly, how long the energy flow last
depends on how fast you draw it or use it.
The core thing most people want to know is how much power is available to output (measured in terms of Watts) and how much energy is stored (measured in turn Wh) so they can determine what they can power and for how long.
Let's put this into mathematical formulas to calculate the energy power and storage a battery has is:
Watts = Amps x Volts
Watt Hours = Volts x Amp Hours (Ah)
SPECS ConfusionMost batteries have ratings that give you one or more of these data points. For example, if you have a 12V 90Ah battery, you can multiply those to get Wh (12 x 90 = 1,080 Wh). An Ah is a measurement of the charge that can be delivered by the battery.
But here's where some confusion occurs – Volts often operate within a range. So what is called a 12V battery may be that or more likely will range between nearly 10V to just over 14V. This range effects the Wh. And of course, if you adjust the Amp rate or draw on a battery that will also affect the results. For the "average Joe", 12V is a term used as a general or common term that is familiar and used in search engines and elsewhere. If you're more of a "tech Joe" you want to know what the "nominal voltage" which is used to do the technical calculations for installations and such. For example, in general the Safari UT is called 12V lithium battery that has an actual nominal voltage of 12.8V. When you use the nominal voltage in the above formula you get a different result (12.8 x 90 = 1,152 Wh). In like fashion, Ah can vary too.
This is one reason why batteries that are referred to as 12V batteries may have a different Wh number – it depends on if the common 12V or the nominal 12.8V voltage is being used. It might be better to call it a 12V system, thus allowing for the range of Volts that work within that system. Another reason you may get different results is because there is not a single "standard" way of representing the rating. Batteries can be tested different ways and under different conditions to get the end rating. Let's use another analogy – automobiles.
How many miles can you drive in your vehicle on a tank of gas? Well, that mainly depends on a few things like city miles vs hwy miles, mph, tire inflation, size of vehicle, etc. For our purposes, we'll just use how fast you are driving. If you're driving on the freeway at 55 mph you'll get better fuel efficiency and therefore drive more miles on a tank of gas than if you're driving 80 mph. This is because it takes more gas to power the vehicle at 80 mph than at 55 mph. In a battery, the more Amps that are being use means you'll have a shorter amount of time and less energy (Ah) available for you to use.
So how can you compare one battery against another based on V, A, Ah or Wh? Here are a few "more common" ways testing and ratings are done. Each manufacturer determines which one(s) they use for their battery rating.
With Lead Acid batteries one testing method is based on a 20 hour
test. It basically uses an even draw rate over a 20 hours period to
determine the Ah. So if they rate it as a 90Ah battery it is being run
at an even Amp draw of 4.5A for 20 hours (4.5Amps x 20hrs = 90Ah). One
of the keys to keep in mind is the "even draw" rate. When actually using
the battery, the draw or discharge rate is not even because you are
using it for different things ie. RV or Trailer slide outs draw more
power than lights and lights draw less power than a microwave, etc. So
how long you can use that battery will vary depending on what you are
using it for.
Another test to determine ratings is called a Reserve Capacity test. It basically counts the number of minutes a fully charge battery will discharge at a 25A draw before the battery is "dead." Oh, and improperly draining a lead acid battery to dead usually damages the battery enough that you'll need to replace it. Lithium Ion batteries can be recharged to full after it is drained when a properly programmed BMS (more on BMS below) is used. Reserve capacity test also use an indicator called "C" which is the capacity of the battery and draw rates (Amps) as a proportion of the Ah rating. You can do the tests at various C i.e. 3C, 1.5C, 1C, .5C and so on.
These are just a couple tests a manufacturer can use to determine ratings and there are some additional variables within just these two tests. We haven't even mentioned rounding numbers when providing rating. It's sort of like comparing apples to apples verses comparing apples to oranges. Everybody can see the difference between an apple and an orange but may not be able to tell one apple from another: Fuji's apples are different than Granny apples which are different that Red Delicious apples and so on. They are "apples" but not exactly the same apple. You've got to go beyond just the eye test.
Lithium Ion battery testing involves even more variable that include application use. Since most people are more familiar with lead acid batteries, let's apply the two tests above to a lithium battery, the Safari UT. The Safari UT works with 12V systems.
We ran several tests on the Safari UT. One of the tests used measures the capacity of the battery in Ah. Basically, you apply a set discharge rate (Amps) to determine how long it takes to discharge at that rate. For example, if the Ah rating is 90 then when you discharge it at 90A, it should take one hour to discharge or 1C (capacity). The graph below shows the results of the different C tests.
Remember that tests are also dependent on the composition of the battery cells and are usually run in controlled conditions in the lab or facilities. The data is then extrapolated to "real world" use. Most RVer use an average of 4-8 Amp daily after initial camp setup. Setup requires a heavy load or Amp usage around 25A for a shorter period of time. Remember our vehicles and mph analogy? Heavy load usage is like driving 80 mph, it takes more out of your battery.
What's the Truth
At Lion Energy, we are going to give you the data so you can see what
is going on. We use testing to provide you ratings that are accurate so
you can draw your own conclusion. Remember that some data points have
ranges due to variables mentioned above.
So what is the rating of the Safari UT?
The Safari UT is 12.8V, 90Ah, 1152 Wh rated battery (refer to the chart above).
It also has a built-in smart battery management system (BMS) that protects and extends the life of the battery, giving you years of performance.
|We've designed it to get the most out of common usage and often more performance than the competition. For example, because it can handle a high spike of power draw and has a higher continuous discharge rate (150A) it can power heavy use requirements that other lithium batteries in this class can't.|
Limited Lifetime WarrantyWe're so confident in the Safari UT that we stand behind it with a limited lifetime guarantee – the battery cells, even under extreme use of maximum charge and discharge rates, will last at least 3,500 cycles (charging and discharging and charging again). That means it will have at least 80% of its cell capacity after all that heavy use and still have capacity to continue on. And most people won't work it that hard. If you used it as most do, we would expect to have it last at least 5,000 cycles. We're not limiting the warranty to "time" but rather the use and capacity of the cells in the battery. So if you ever have a question or a problem with the Safari UT because it's not performing as above, let us know and we'll take care of it.
BTW, here's a fun thought: if you used the Safari every day, using all the energy in it and recharging it back to full, it would take nearly 10 years to reach 3,500 cycles. And how many days a year are you going to use it? Instead of every day complete use, how about every other day (that would be 20 years to reach 3,500 cycles) or every three days… well, you get the point, it's an awesome performance battery!