Battery guide for boat, cottage, caravan and off grid.

When you need new batteries for your off grid installation, you needs be aware of if the batteries you choose suits the purpose, the battery quality is high and that you know how they should be maintained. this battery guide helps you make the right decision.
Most batteries today are not being used and cared for as they should and therefore most batteries are replaced much faster than it really is necessary.
We are not here to make a final recommendation to you to make the right choice, as there are many factors that come into consideration, but we will be very close to being able to take your decision with you.

You have to decide several things before you can select your battery:
Start by considering what you need your new batteries for.
In Off grid installations (boat, cottage, allotment, caravan, telecommunications mast, etc. are all off grid installations) has typically a continuous power requirements. So a fairly steady drain on the battery over time. In contrast, with the for example. a starter battery for a motor that need large power in a very short period. That is the reason that in Boats, Campers and similar there is often two batteries (or battery banks). There is a type of battery to start the engine and another to provide power during the day for other services. If you do not have an engine in your installation, so disregard starter batteries in the following.

Once you know what the battery must be able to deliver and the size (see our calculators for solar, wind generator and combined solar and wind setup calculator, we can look at the different types of batteries.
When you select the type of battery there are many things that separate battery types and the economy is also one of them.

Start batteries (wet-cell).

  • Used as it is in the name, to start an engine with. The batteries can not handle deep discharges and are rapidly destroyed by deep discharge cycles. A start battery has a very long, if it is only used to start an engine and are recharged after each time it is used (when the engine sends the power it has used, back in the battery). A battery should not be discharged by more than 5%
  • When you have a starting battery at 100 Ah (ampere hours), you should not need more than 5 Ah. We can quickly determine that this type of batteries just are not good as consumer battery.
  • Start Batteries are not attractive for consumption batteries at any point than price. They are somewhat cheaper than other batteries, but will not work as consumption battery! Do not fall into this trap, because it’s wasted money and batteries that quickly needs to be replaced again.

AGM batteries (Deep cycle).

  • AGM batteries have a dense filling of absorbent glass mat, packed tightly between the battery plates. The matting is saturated with acid electrolyte. This means that oxygen can recombine with the hydrogen and therefore replenish the battery’s water content. That is smart! No maintenance is needed, except some external standard cleaning. Because these batteries are completely sealed and tight, the acid inside is not let out and flammable gases will not be released to the air. AGM batteries can also be installed in many different angles. They are resistant to shock and vibration and has a low self-discharge (about 2-3% per month at 25 degrees Celsius).
  • Compared with GEL batteries AGM is better to handle fluctuating charge and discharges. That is, in an installation where there are a wind generator important, AGM has this advantage which will mean that more of the power flow coming into the battery, will stay in the battery.
  • Disadvantages are cost, greater weight than comparable wet-cell batteries (starter batteries) and the fact water can not be replaced if the battery is accidentally overloaded.

GEL Batteries (Deep Cycle).

  • Gel batteries are filled with liquid electrolyte, wich then is gelled with silicates, before the battery is sealed. Like the AGM batteries, they use a recombining technology that eliminates the need to top up with water. They are totally maintenance-free, tight sealed, low temperature tolerant, resistant to shock and vibration and has a long life cycle. Their most notable advantage is resistance to over-discharge that can damage other battery types. Both GEL and AGM batteries are designed to be discharged with typically around 50%, but GEL doing better to be discharged further.
  • GEL batteries have an internal self-discharge less than 1-2% a month, so they can all be stored for long periods without being recharged. And because they are not likely to develop lifetime shortening plate sulfation when they are charged, they are a good choice for those who often forget to recharge the batteries quickly after use.
  • Gel batteries show their disadvantages when it comes to cost and recharging. They generally cost more than other battery types with the same RC and MCA ratings. Most manufacturers recommend charging them to at least 13.8 volts, but no more than 14.1 volts. Standard marine battery chargers typically routinely reach higher voltages, so chargers must be designed to include gel batteries or those with a GEL setting must be used.
  • In an installation with solar cells is GEL batteries a really good choice, when the size of the battery bank is matched to the solar cells. GEL should be charged with a less amperage than the start and AGM batteries.

    Hybrid batteries.

  • There are hybrid batteries on the market that think they can handle both start currents for the engine and being a good battery for consumption. Such a battery will always logically be a compromise each time. We do not recommend them!
  • If you would like a battery bank for the whole thing, it can maybe be done, for example with an AGM battery bank. AGM batteries will be more willing, than GEL batteries to deliver higher currents for shorter periods and if you have enough batteries put together in your battery bank, they can might also provide the power your starter motor demands. So you should compare your starter motor needs with battery bank’s ability to meet the needs. A single AGM battery probably can not handle the job, but every time you parallel connect a battery more to your battery bank, you are subject to more rapid flow calculation.

Lithium / Ion batteries.

  • We will update this page when the Lithium/Ion batteries are financially within reach for Off Grid use. At this writing time, they are not.

Other Battery Solutions.

  • We keep an eye on the market and when there are good alternatives to the described battery types, we will expand this side and a lot is happening on that front for the time being ….

Generally, you should always check that your generator on the engine/your grid charger can deliver the power required to charge your battery bank, also over a long period of time. This may be a problem with some generators on cars/RVs/marine engines.

Do not mix batteries !! Do not mix different types and sizes of batteries in the same battery banks. They must be charged different, don’t behave the same way and there are differences from brand to brand.
We will even recommend that you always replace your entire battery bank and not just a single battery or two. If your battery bank consists of five identical batteries that are treated equally, purchased at the same time, the probability of the 4 batteries are 100% in order when the 5 fails are not very likely (unless there is an outright fabrication errors in the individual battery). After X years of operation, change them all simultaneously.

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What does Energig recommend?

Our recommendation must be seen as a guide and not necessarily a definitive truth. You can always write/call us and task about your situation.

   Start Battery.
We recommend that you use it to start your engine and other high drain for a short time (eg. a bow thruster), but not for anything else.
AGM Batteries.
If you have a wind generator in your setup AGM a good choice. It is also a good choise if you have both solar and wind generator or a pure solar setup.
They are extremely vibration resistant and therefore they are good for car / boat / camping
GEL Batteries.
They lack a little on the ability to receive and deliver power quickly and therefore they are not quite as good for wind generators as AGM, but they are better at coping with being discharged deeper and if you need that, you should look at GEL. Eg. for a house to run offgrid, with primarily solar cells.

Below you can see the batteries that are Energig tested,is a high quality product and are what we recommend:

  • Haze AGM batteries

    12V Battery AGM deep cycle

    Price 40598 VAT included
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  • Haze GEL Batteries

    12V Battery Gel deep cycle

    Price 31647 VAT included
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  • Mastervolt AGM 12/270 Ah

    MasterVolt Batteries – AGM series

    Price 210798 VAT included
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  • Mastervolt Multi Purpose Contact Output

    MasterVolt Batteries – Lithium Ion Accessories

    Price 142252 VAT included
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  • Mastervolt MLI Ultra 24/5000 – 5

    MasterVolt Batteries – Lithium Ion MLI

    Price 3.2195.664 VAT included
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  • Mastervolt MLS 24/260 (10Ah)

    MasterVolt Batteries – Lithium Ion MLS

    Price 175643 VAT included
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  • Mastervolt MVG 12/200 Ah

    MasterVolt Batteries – MVG series

    Price 167939 VAT included
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  • Mastervolt MVSV 2700 AhBatteries - 2 Volt Gel (Shipping crate required* )

    MasterVolt Batteries – MVSV series

    Price 3202.050 VAT included
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  • Mastervolt D

    MasterVolt Battery terminals

    Price 34 VAT included
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    Mastervolt Cooling plates 2 V batteries (dim. 715x195x10 mm)

    Price 24 VAT included
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