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Battery Comparison for Deep Cycle Batteries

Sources used: WindSun.com

A comparison of the various types and brands of deep cycle batteries
Zen and the Art of Choosing a Deep Cycle Battery

There is more to comparing batteries than just cost or amp-hour ratings. For example, based only on cost, the AGM's do not look so good. On the other hand, you probably would not want to store a flooded battery in your computer room. There is no one best battery for all applications. If the batteries are in a remote communications site, low maintenance might be the most important feature. For the off-grid full time home, capacity, life, and long term cost would probably be the most important.

We stock batteries from these companies. We do not stock all sizes from all companies, but can obtain most standard sizes within a few days.

• Sealed AGM - Leoch, TopPower, Haze, Bae
• Gelled (OPzV and OGiV)- Leoch, TopPower, Haze, Bae
• Flooded - OPzS series - Leoch, Haze, Bae

The "Best" battery for a particular system is not always the most expensive, but it is seldom the cheapest either. There are many things to consider.

System storage requirements

How much storage, in amp-hours, do you need? This will vary with the application and what part of the country you are in. As a rough rule for home solar systems, the total battery capacity (in amp-hours) should be three to five times your daily usage. 3 days is usually sufficient in most of the Southern regions and some regions of Far East, 4 in most of the East Siberia and Yakutia, and in the West and North, 4 to 5 days is better. If you are in a good wind area and have a wind generator, you can probably cut this down a day. It also means you will rarely get caught out again being low on battery and having to call colleagues' o2 mobile phones to get them to come and help you. So as you can see there is a wide range of benefits using a deep cycle battery.

For backup power systems (UPS), the total capacity should be enough to cover about twice the longest anticipated outage. To figure how many amp-hours storage you need, take your average daily usage in watts and divide by the battery voltage. For example, if you use 5 kWh (kilowatt-hours) per day, and have a 48 volt system, then dividing 5000 by 48 gives you 105 AH. Since you do not want to discharge the battery more than 50% in most cases, you would need 210 AH. If you want to keep running for 4 days of bad weather with no sun, multiply that times 4, which gives you about 850 AH total capacity. UPS and backup power systems are the same, except that the times are often in hours instead of days.

How many Watts in a battery?: Watts are pretty simple - it is just battery voltage times amp-hours. A 12 volt 105 AH battery can supply (under perfect conditions and to 100% discharge) 12 x 105, or 1260 Watts.

Upfront (initial) costs

This is what most people look at. Batteries are the component that are most often skimped on, but can make or break a system. There is a lot of hype about batteries, especially those being sold outside the solar industry - that Sears "deep cycle" marine battery on sale for $39 might seem like a good deal - until you find out that it will probably only last about 2 years.

In general battery types run (from cheapest to most expensive):

1. generic golf car,
2. "regular" deep cycle, such as the Trojan's,
3. heavy duty or premium deep cycle, such as the Rolls-Surrette,
4. and then the sealed AGM and
5. the industrial batteries, such as the Crown forklift batteries.

Price is a fair indicator of the overall expected life when used in a particular application. A note here on "free" batteries - they are usually worth about what you pay for them. There are exceptions, such as occasionally stumbling over a pile of 4-year old telephone batteries, but they are few and far between. In fact, we usually do not recommend ANY used batteries - regardless of the price.

Lifetime costs

This is what really determines the long term cost, but sometimes the up-front costs can be higher than what was expected. There is more to the lifetime cost of a battery system than just the battery costs up front - you have the interconnects, shipping costs, maybe Hydrocaps or Water Miser caps, maintenance, and eventually disposal.

Maintenance may not cost money, but it can certainly cost time - if you have an underachieving set of batteries that you have to keep watering constantly, that can get old real fast.

As a general rule, the more expensive the battery, the longer it will last. Generic golf car batteries can be expected to last 3 to 5 years, Trojan and similar types around 4 to 6 years, Surrette (depending on type) 8 to 20 years, and industrial 15 to 25 years. AGM's will generally go for 5 to 8 years. There are pro's and con's to both sides - if you are only going to use the system for 5 years, there is not much point to buying 20 year batteries.

Size and weight

The best and/or cheapest battery in the world is not much good if it so heavy that you cannot move it. While the industrial batteries, such as the Crown are the heaviest duty batteries, they are also the heaviest - some can weigh as much as 2,000 pounds for a 12-volt pack. On the other hand you don't want to end up with 50 or 60 small batteries that are a nightmare to wire up and keep maintained.

A good rule is to try and keep the total number of batteries between no more than 8 to 12. If you need more capacity, get bigger batteries, not more small ones. If you use Hydrocaps, they cost around $9 each - whether you need 48 for a pile of small batteries, or 12 for a few larger batteries.

Flooded or sealed

Sealed batteries make sense in some applications - but not all. Sealed (AGM) batteries are generally 2 to 3 times as expensive as flooded, and the cycle lifetime is usually similar.

• In areas with no or poor ventilation
• In areas or applications where maintenance is a problem, or is poorly done
• Any place that a flooded battery might spill or break and cause damage
• Where the batteries are in a spot where it is difficult or time consuming to check water levels
• In situations where the batteries must be mounted on their sides to fit

Flooded batteries are perfectly fine for most applications. They are usually much cheaper OR have a much longer life (for the industrial and premium batteries, such as Rolls-Surrette). They do require some maintenance and watering. They are the best choice where:

• You have adequate ventilation for the batteries
• You do not have to worry about tipping, spillage, or breakage
• The batteries are in an area where maintenance can be performed without too much hassle.

Disposal costs

This is usually only an issue where some of the "exotic" batteries, such as NiCad, are concerned. We have had people tell us that those "free" NiCad railroad batteries were not such a good deal as it cost hundreds of dollars to get someone to take them - and there are some severe penalties for disposing of them in the wrong way.

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