When looking at the vast number of batteries available in the marketplace today, we are confronted by an array of numbers (Battery Specifications) which should make selecting a battery for your task so much easier, but…
Battery technology has come a long way over recent years from when there were only Lead Acid batteries and capacity was based on number of plates e.g. 7 plates for a small car and up to 11 if you had a larger car. This has all changed.
Batteries are designed for a variety of purposes and construction types, but basically, for the car, caravan, boat, or camp there are essentially 3 classes of battery.
Lead Acid Class which can be any of: –
This is the traditional engine start, tractor and deep cycle-style battery. The liquid electrolyte is free to move in the cell compartment. The user has access to the individual cells and can add distilled water as the battery dries out.
Sealed Lead Acid
This term can refer to a few different constructions, including only a slight modification to the flooded style. In that case, even though the user does not have access to the cell compartments, the internal structure is still basically the same as a flooded battery.
The construction allows the electrolyte to be suspended in close proximity with the plates active material. In theory, this enhances both discharge and recharge efficiency. The AGM batteries are a variant of Sealed VRLA batteries, just a more advanced design. Popular usage includes high-performance engine starting, power sports, deep cycle, solar, and storage batteries.
Gel is similar to the AGM battery style because the electrolyte is suspended, but different because technically the AGM battery is still considered to be a wet cell. The electrolyte in a gel cell battery has a silica additive that causes it to set up or stiffen.
The unique Lead Crystal® battery consists of several special features including: a micro porous high absorbent mat (AGM), thick plates cast from high purity lead calcium selenium alloy (which ensures an extended life), and a SiO2 based electrolyte solution.
And as battery technology improves, we now see the more common use of Lithium Batteries, the most common in the marketplace for Vehicle use is LiFePO4 – Lithium Iron Phosphate and there are a variety of construction types including Cylindrical, button, Pouch and Prismatic cell types.
There are numerous advantages that lithium batteries have over lead-acid batteries with respect to recreational vehicles such as caravans, motorhomes, and camper trailers. These can be summarised as:
- Weight – lithium batteries are at least half the weight as lead acid equivalents which is important in an RV. A 100Ah lead acid battery weighs around 32kg, whereas our 100Ah lithium battery is ~12kg.
- Depth of discharge (DOD) – lithium batteries can be safely discharged to 80% DOD compared to typically 50% DOD for lead acid batteries. This means for a 100Ah battery you have 80Ah available to use with a lithium battery and only 50Ah with a lead acid.
- Constant voltage – lithium batteries discharge at more or less a constant voltage until they reach around 80% DOD, after which the voltage begins to drop off. Compare this to a lead acid battery where voltage begins to drop as soon as power is drawn. This means that with a lithium battery, low voltage disconnects to protect appliances are not activated before the battery is empty like they are with a lead acid battery.
- Cycles – lithium batteries last a lot longer than lead acid batteries, in that you can cycle them more times before they need to be replaced. Our lithium batteries are rated at 2,000 cycles times at 80% DOD compared to a lead acid battery at 500 cycles.
- Power output – our high power (HP) lithium batteries can discharge at up to 200A continuous which is made possible by the BMS. Being able to discharge at 200A allows the RV owner to run high power appliances such as microwaves, kettles, coffee machines etc.
Regardless of the battery type the numbers still mean the same thing and you will need to select a type for the purpose i.e., Cranking battery or storage Battery (Deep Cycle). Cranking batteries will deliver a high current for a short period where deep cycle will deliver lower current for long periods (i.e. – to run the fridge in your camper)
CCA – Cold Cranking Amps – This is the rating used to define a battery’s ability to start an engine in cold temperatures. Generally, it is much easier to start an engine in warm conditions. The rating refers to current – Number of Amps a 12-volt battery can supply at 0 degrees C for 30 seconds while of how much
Generally, Batteries with a CCA rating are designed to be cranking (Starting) batteries.
AH – Ampere Hours – This is usual rating on Deep Cycle Batteries. And can roughly be considered as the number of hours a battery can deliver one amp. Standard testing however is based on a 20-hour test period. – a 100 AH battery can deliver 5 amps for 20 hours until 100% DOD (Depth of Discharge)
When comparing battery AH rating you need to consider the recommended depth of discharge of the battery. Many Lead Acid class Deep Cycle batteries can only have 50% Depth of Discharge so in a 100 AH Battery you may only have 50 usable Amp Hours.
In most Lithium Batteries you can have up to 80% depth of discharge so usable power is 80% of total.
What this means is – as an approximation, a 75 ah Lithium Battery will have similar usable power to a 110AH AGM or Gel battery – ALWAYS Verify with Manufacturers specifications for the battery Type.
Flow Rate: – This is generally set by the battery management system and is particularly pertinent if you are running an inverter or similar powered device.
For a 1200-Watt inverter, your battery system will need to be able to flow or provide 100 amps continuously for the maximum load to be achieved. In a 100 Ah Lead Acid class battery this means your battery will be flat in about 30 minutes.
SO when selecting the battery you need to consider what you wish to power, how long you need to power it for, how and when you will charge the battery and how the battery will be stored.
If you would like further information or advice on changing to Lithium Batteries, contact us today!