What types of batteries suitable for campers, vans or trucks are on the market? Three: AGM, GEL and Lithium.
Let’s begin to understand the substantial difference between GEL and AGM, which are based on the same technology but differ in the substance that covers the electrolytes. We are interested in knowing that both can be installed in any position, do not risk losing liquids and can be used in poorly ventilated environments. AGM vs standard battery , AGM batteries perform slightly better in terms of faster discharges, while GEL is recommended for slow discharge uses and where there are solar panel installations. GEL batteries also work a little better at higher temperatures.
While adapting very well to the slow discharge characteristic, these three technologies have different features from each other (and even by a lot). What mainly differentiates them? Apart from the price, which we will see, these batteries differ from each other in their ability to be fully discharged (sincerely), the number of life cycles, the speed of recharging to which they can be subjected, their specific weight and the price. We don’t want to complicate the situation, and we try to explain these concepts better:
Deep discharge: basically, it’s how much we can afford to empty our fuel tank. We will see how AGM and GEL batteries force us always to keep a lot of fuel in the tank. In short, it’s like filling up every time but needing help to use it all—an excellent bummer.
Life cycles: Even more straightforward, how often can we go to the dispenser after emptying our reserve? In practice, this parameter indicates longevity in terms of the life of your investment in batteries. Note that often in the battery datasheets, a duration value in years is displayed, but this is valid when the batteries are not used.
Charging speed: exciting data because it indicates how long our batteries can still be used. In practice, we will see how lithium batteries support very fast recharges, optimizing above all any fuel costs of the generators, or optimizing the energy supplied by the solar panels.
The data with which the recharging capacity is indicated is the number of times the power of the batteries. If a 400Ah battery bank is charged at 1C, it is supplied 400Ah per hour during the recharging phase. In the diagram below, we see that, for example, lithium batteries can withstand charges at 0.5C without problems, i.e. in the example shown above, 200Ah. At the same time, the equivalent AGM or GEL would only support 400*0.2 (0.2C)=80 Ah. This data is also essential for choosing your charger.
Weight: Trivially, lithium batteries weigh, on average, three times less than the others for the same Ampere supplied.
Price: There is little to be said and done. Lithium batteries currently cost a lot. But remembering that these can be downloaded more significantly, additional calculations will have to be made to understand the actual cost/benefit ratio. Let’s start by saying that, for example, a good quality 12V 220Ah battery can cost around 400 Euros, while buying a 12 Volt 200Ah Lithium battery will take approximately 2800 Euros.
Batteries, the sizing of your service counter
Given what was described in the previous paragraph, are we faced with a fundamental choice, Lithium or AGM/GEL?
Let’s take up all the data obtained and give two examples to evaluate our needs. N.B. In our calculations, we will consider the use that does not expect to fall below the maximum expected discharge values to obtain the complete life cycles. For ease of understanding, we will use a 12 Volt battery bank in the example.
Assuming that we need 1230 Watts of the reserve, we get the following:
Regarding GEL/AGM batteries: 1230 Watt / 12 (Voltage of our bank) = 102.5 Ampere. However, our bench must have a capacity such that the 102.5 Ampere are at most 30% of the total capacity. So we obtain that our bank must be made up of: 102.5 (Ampere) * 100 / 30 (Percentage of maximum use) = 341 Ampere. These are, therefore, equivalent to a total of 341 Ampere * 12 Volt = 4100 Watt.
As far as lithium RV batteries are concerned: 1230 Watt / 12 (Voltage of our bank) = 102.5 Ampere. However, our bench must have a capacity such that the 102.5 Ampere are at most 80% of the total capacity. So we obtain that our bank must be composed of 102.5 (Ampere) * 100 / 80 (Percentage of maximum use) = 128 Ampere. These are, therefore, equivalent to a total of 128 Ampere * 12 Volt = 1538 Watt.
To this must be added the duration in terms of cycles, which therefore leads to considerable differences in management costs of our plant. In practice, we obtain a period roughly double for the latter by evaluating an AGM bank with a time of approximately 1200 cycles compared to 2500 of the lithium battery bank. Let’s see specifically:
GEL/AGM battery bank: Two 12 Volt 220 Ah batteries in parallel will be needed to obtain a 12 Volt 440 Ah bank for a total of 5200 Watts, sufficient to cover the calculated requirement of 4100 Watts. The average cost of this bench is around 800 Euros. This bench will need to be replaced indicatively once (remember the double duration previously calculated) to arrive at the same Lithium bench’s course, bringing the management cost to 1600 Euros.
Lithium battery bank: A 12 Volt 160 Ah battery will be needed to obtain a power of 1920 Watts sufficient to cover the requirement of 1538 Watts that we have calculated. The average cost of this bench is around 2300 Euros.
However, we also want to draw attention to the comparison in terms of weight, given that, as we said, it is decidedly in favour of lithium batteries by a factor of 1 to 3. In the example shown above, the GEL/AGM battery bank would weigh about 130 Kg against approximately 40 of the lithium equivalent, which also has a better ratio in terms of size.
As we said before, describing the different types of batteries in detail, what matters during your system’s review or installation phase is to understand your needs in terms of energy reserve. After that, the choice is up to your wallet.
We can give an indication of the choice we made on our Valentino truck, where we installed a bank made up of 8 Renogy GEL batteries for a total capacity of 880 Ampere at 24 Volts or about 21 kW of power. This entailed the preparation of adequate space, which was divided into two distinct compartments, one under the garage and one in the rear garage.
Although driven by our interest in new technologies, where it is clear that lithium batteries will be the investment for the future, we have evaluated the decision to invest a lot of money too prematurely. Our choice was also made considering that lithium batteries 12v, 24v or 48v indeed need fewer elements, but if these were to fail, the total capacity would also be affected. In the example shown above, for example, it is evident how the breakage of the 160 Ampere lithium battery creates the total absence of energy, as well as real economic damage equal to 2300 Euros. Any damage to one of the two AGM batteries, on the other hand, would lead to a financial loss of 400 Euros and limit the system’s use by 50%.
