Starter Batteries and Deep Cycle Leisure Types

For most automobile and marine applications the 'simple' lead/acid battery type is by a massive degree the most popular form. There is, however, much in the way of 'smoke and mirrors' behind the marketing of modern batteries. Prospective purchases of batteries for 'leisure' use are open to advertiser's free use of often misleading information. The truth is that there is no such thing as a starter / leisure battery, nor is it a good idea to buy so-called 'maintanence free' types. If you cannot check the acid level in your battery and top it up if necessary, your battery will fail earlier than it otherwise might. Battery retailers charge more for 'gel' batteries when there is no real benefit to this unless you intend to lay them on their side or knock them over on a regular basis, they are generally more expensive and have a smaller capacity. A lead acid battery that can be topped up when required is always the best way to go.

Starter Batteries - Including most so called starter / leisure types typically don't have a huge amount of capacity, but generally, because of their thin plate design, can produce very high 'Cold Cranking Amperage' in a burst for starting an internal combustion engine. These bursts of power are quickly replaced with the immediate output of the engine's charging system. If all we want these batteries to do is to start the engine then these thin plate batteries are ideal.

Deep Cycle and Semi Traction Batteries will supply cold cranking amps in the way a starter battery will, but they are specifically intended to have high storage capacity that is utilised more slowly. A perfect example of this is the very common use of Trojan batteries in Golf buggies. The batteries spend the night being charged and the day transporting a golfer around a golf course, without the 'benefit' or noise of an internal combustion engine. This kind of usage would kill a starter type battery in no time at all. It's good to remember that while a deep cycle battery will start an engine and survive, a starter battery used for domestics will meet a very premature death.

Let's take a look at my personal choice of leisure batteries, the Trojan range. In common with a majority of boats, my boat has two battery banks. The number 1 bank is a pair of standard12 volt starter batteries used purely to start the engine. Through a '1-2-both-off' switch I can concentrate 100% of my boat's alternator output to the starter bank (Number 1 on the switch). After I'm happy that the starter bank has replenished I turn the switch to number 2. This is my leisure bank and it looks after 'domestic requirements'. The idea here is that when I moor the boat, my starter bank is isolated. This way, even if I deeply discharge my leisure bank there is plenty of power in the starter bank to get the engine going. As the switch description suggests, I can charge either or both banks and if I choose I can also isolate both banks from the charging system.

Trojan battery group

A Small Selection From the Trojan Battery Catalogue

Identified by their unmistakable maroon colour, these are genuine Trojan Deep Cycle Batteries. The model I'm using is the T105 shown bottom left in the picture. I have four of these that provide me with 225AH (amp hours) at 24 volts. The batteries are wired in series to provide 24 volts. If your boat or RV leisure supply is 12 volts, you will only need two batteries. Shown in the picture are the T105 - 6 volt model, the T875 which is 8 volts and the T-1275 that is 12 volts.

Some batteries are called 'T105' but are black in colour. These batteries are not Trojan's. Be sure to buy the genuine article.

Remember to wire in series to increase the voltage and in parallel to increase the capacity. On my own system, I could fit another bank, wired in the same way as the first to provide two X 225AH banks, but by connecting both seperate banks together in parallel I would have a single 450AH bank - A lot of power, though some boats have massively more.

Something very important to remember is that you must match your battery bank capacity to your electrical requirements. If you want to act as if you are at home, using very power hungry kit - immersion heaters, washing machines and electrical showers etc., you will need a very large battery bank, an equally large inverter and at least one, but probably two high output alternators to recharge the banks.


These search results may well return other battery makes as well as the Trojan range. Use due diligence to ensure that you are purchasing the genuine article.

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Here's Something I hope you'll enjoy- An opportunity to see how Trojan build their deep cycle batteries.


Trojan Factory Video

Starter Batteries - As we discussed above, starter batteries are purpose made to provide a high burst of power to provide the amperage to start a petrol or diesel engine. Such a battery has the ability to provide a high level of 'cold cranking amps' or CCA. For maximum service life I would recommend a standard lead / acid battery that can be topped up with distilled water as the internal plates need to be submerged to operate properly. It is also well worth noting that this type of 'thin plate' battery is totally unsuitable for deep cycle use. For this you must refer to the paragraphs above.

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