Home/Guides/Battery guide for boats, caravan, cottage and off grid
Battery guide for boats, caravan, cottage and off gridStoffer2021-03-02T14:57:31+01:00
Batteries on the boat, in the cabin, caravan and general off grid.
When you need new/replaced batteries in your installation, be aware that the batteries you choose will fit the purpose, that the quality is high and that you and your gear knows how to maintain them. Most batteries today are not used and looked after the way they should, and therefore the batteries need to be replaced significantly faster than what is really necessary. We can not give you a final recommendation for what you should choose exactly, as there are many factors to consider, but we can help you, making your own decision. We do not want to say that any type of battery is best as it depends on what you need them for, but … Lithium batteries will often be the right professional choice, with just a few exceptions. On the other hand, Lithium requires a relatively large initial investment (which, however, returns over time)
You need to find out several things before you can choose your battery: Start considering what you need to use your new batteries for. In Off grid installations (boat, cabin, caravan, tele-mast, etc. are all off grid installations), you typically have a continuous flow of power. Like a fairly even pull on the battery for a long time. Conversely, for example, a starter battery for a motor that needs a lot of power for a very short period of time. That’s why you’re in boats, camper vans and the like, often have two batteries (or battery banks). Then there is a battery type to start the engine and another type to supply power over the day for other usage. If you do not have a motor in your installation, please ignore the starter batteries below.
When you know what the battery should be able to deliver, we can look at the different battery types. When choosing a battery type, there are many things that differentiate the battery types and economics is also one of them:
Start batteries (Wet cell). Used, as it is in the name, to start a engine with. The battery type can not handle deep discharges and is quickly destroyed by deep discharges. A starting battery will last very long if it is used to start an engine and is recharged after each time it is used (the engine will send the power it has used back into the battery). A starter battery should not be discharged by more than approx. 10% So if you have a 100 Ah (Ampere hours) starter battery, you may not need more than 5-10 Ah, to start your engine. We can quickly determine that this type of battery does not work as a service battery. Start-up batteries are not useable for service batteries. They are somewhat cheaper than other batteries in purchases, but do not work as a service battery! … Do not fall into this trap, because it is a waste of money and the batteries have to be replaced soon.
AGM batteries (Deep cycle). AGM batteries have a tight filling of acid in an absorbent glass mat packed closely between the battery plates. The matt are saturated with acid electrolyte. This means that the oxygen can recombine with the hydrogen gas, thus rebuilding the water content of the battery without loss to the surrounding environment. Maintenance is not necessary, except for a small amount of external cleaning. And because these batteries are completely sealed, the acid inside will not be spilled and flammable gases can not be released during normal use. AGM batteries can also be installed in many angles. They are resistant to shock and vibration and have a low self-discharge (Approx. 3% per month at 25 degrees Celsius). Compared with the GEL batteries, AGM is better at handling fluctuating fast and up-charges. eg. in an installation where there is a wind turbine, the AGM has an advantage which will mean that more of the power will pass into the battery and be stored. Although the AGM is a deep cycle battery, it can deliver a lot of power quickly and thus, for example a super good choice for the bowtruster or as a mover battery. AGM is the cheapest of the deep cycle batteries, but they do not last as long as GEL and not nearly as long as the Lithium batteries do. It is also not so resistant to deep discharges (over 50%), such as GEL and litium. AGM is the battery that is the least tolerant to high temperatures. We usually recommend GEL rather than AGM.
GEL Batteries (Deep cycle). Gel batteries are filled with liquid electrolyte, then gelatinized with silicates before the battery is sealed. Like AGM batteries, it uses a recombination technology that eliminates the need to fill with demineralized water. They are completely maintenance-free, sealed, relatively low temperature tolerant, resistant to shock and vibration and have a long cycle life. Their most notable advantage is the resistance to over discharging that could damage other battery types. Both GEL and AGM batteries are built to be discharged by typically about 50%, but GEL manages better to be further discharged if it slips a day (and it does …). GEL Batteries have an internal self-discharge at approx. 1 percent per month, so they can be stored for long periods without being recharged. And because they are not so inclined to develop lifetime shortening plate sulphation when charged, they are a good choice for those who sometimes forget to recharge the batteries quickly after use (but you must constantly recharge them soon after use as a rule !). Gel batteries show their weakness when it comes to price and recharge. Generally, they cost a little more than other lead/acid 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 battery chargers typically routinely reach higher voltages, so the charger should be designed to include GEL batteries and must be configured for your precise battery data. In an installation with solar cells, GEL batteries are a great choice when the size of the battery bank is tuned to the solar size. GEL has to be charged with a smaller and more even current than start and AGM batteries, but is usually the lead/acid battery we recommend for offgrid installations.
Hybrid batteries. There are hybrid batteries on the market that believe that they can handle both the starting job of the engine and being the service battery. Such a battery will at all times logically be a compromise. We do not recommend them. If you want a battery bank for it all, it might be done with, for example. an AGM battery bank. AGM batteries rather than GEL will deliver larger currents for shorter periods and if you have enough battery packs in your battery bank, they may also deliver the power your starter engine requires. So you have to compare the needs of your starter’s engine with the capacity of the battery bank to meet that need. A single AGM battery may not be able to do the job, but each time you connect a battery more in parallel to your battery bank, you get more quick power for the calculation.
Lithium / Ion batteries. This is the big new battery on the market. Lithium batteries are really interesting for almost all Ongrid and Offgrid installations. The technology is lead/acid batteries superior at all points …. with the exception of the initial price, but even that will be paid back in time and better service. – Lifetime is approx. 3 times as long as AGM / GEL batteries. with up to 5000 cycles of charge and discharge at 80% discharge (Mastervolt MLI-E). – size and weight is 1/3 of lead/acid solutions for the same available capacity. – Can be discharged by 80% without damaging. Lifetime is extended by discharge with less % – Between -10 ° C and + 25 ° C, there is virtually no capacity loss. – Fast charging with even very high ampere numbers. – Efficiency of approx. 98%, opposite GEL (85-90%) and AGM (80-85%). Understood as for every 100 Ah you use from an AGM battery, you need 115 – 120 Ah to charge it to the same status. . Charging Lithium We have chosen to use Mastervolt’s lithium battery solution, among many options on the market. There are several reasons for that. First of all, the lithium batteries and the equipment to recharge them (battery chargers, solar regulators, wind turbine regulators, etc.) should not only be suitable for lithium batteries but for the exact lithium batteries they need to charge. Lithium batteries are very sensitive to be charged properly and therefore an installation with lithium batteries must be seen as a whole and not as a charger and battery that you simply put together. Lithium is different from lead/acid batteries in a lot of ways. eg. lithium battery must be charged in another way and it is therefore necessary that all equipment that charges on the lithium battery is fully integrated! On the Mastervolts MLI-Ultra and MLI-E batteries, there are electronics on the battery to monitor the state of the battery, distribution of charge to the cells, charging status, etc. This electronics is connected to the Masterbus (communication network between mastervolt devices) and can exchange data with the battery charger, solar controller, monitor displays, inverters and anything else connected to the Masterbus. (Data from the master bus can also be bridged to Nmea2000, Canbus and many other platforms). If you connect a traditional battery charger to a lithium battery, the lithium battery will continue to receive power as long as it is available from the charger. A GEL/AGM battery will stop receiving power when it’s full. Therefore, the lithium battery in the short term will suffer irreparable damage and …RIP, due to overcharging. . Security There always must be a latching relay that shuts off before to deep discharge occur. This relay is controlled by the electronics in the battery. If the battery does not have this function, find another battery. There are about 19 different types of lithium batteries. We (and Mastervolt) have chosen to use lithium iron phosphate (lifepo4), as it’s the most durable over time and it’s the safest battery. A lithium iron phosphate (lifepo4) battery can not burn, like most other types can, by wrong handeling and there are many more bad handeling than you would like to think … Most lithium batteries develop themselves oxygen under fire and can thus not be extinguish with water or other available methods. This is avoided with lithium iron phosphate (lifepo4), which even in short circuit does not burn. Lithium iron phosphate (lifepo4) also has the longest lifetime of all lithium types and can handle the most cycles. We still do not know how long a properly processed lithium iron phosphate (lifepo4) battery lasts, because technology is not so old yet, but more than 10 years and most likely a nice bit more. Lithium is technically superior in all areas. The only reason that everyone has not switched to lithium yet, has to be the high initial price, because it’s not the cheapest to buy upfront, but with all the benefits and the fact that the batteries last approx. 3 times as long, lithium is not more expensive than an AGM/GEL solution. Most often they will be cheaper and you will get better service from a lithium battery.So you can afford to pay that extra upfront, do yourself the favor of choosing lithium. Almost the only thing you do not have to choose lithium for is to starting engines, it’s cheaper with std. starter batteries.
Other Battery Solutions. We keep an eye on the market and when there are good alternatives to the battery types described here, we will expand this page and much will happen on this area in the coming years.
Charger size In general, always check that your generator on the engine and charger euquipment can supply the power needed to charge your battery bank, also for a long time. This could be a problem with some generators on cars / camper / boat engines. You must have capacity for at least 10% of your Ah capacity count. ideally 25%, but not much more. Keep in mind that your charger not only charges the battery but also supplies what you consume at the same time. Therefore, 25% is a nice rule of thumb. But read more about battery charging in our Battery Charger Guide.
Do not mix batteries !! Do not mix different types, manufacturer and sizes of batteries in the same battery banks. They need to be charged differently, do not even and there are differences from brand to brand. Do not! We will recommend that you always replace your entire battery bank and not just a single battery. If your battery bank is made up of 4 identical batteries that have been treated alike, bought at the same time, then the likelihood of the 3 batteries is 100% in order when it’s 4 are not, is not very likely (unless it is a definite manufacturing defect in the individual battery). After X years of operation, change them all at once. A chain is not stronger than the weakest joint.
Quality All batteries, regardless of type, fluctuate in quality. A GEL battery is not just a GEL battery and the same applies to AGM / Lithium. Generally you get what you pay for and the more expensive, products last longer, are not damaged so easily and especially for lithium it is important that the built-in electronics are of high quality that it communicates with the charging euquipment, understands the maintenance and protection of the batteries. Your batteries are the most expensive part of the power installation. It’s also the most vulnerable part and therefore the quality needs to be as good as possible and the equipment that service the batteries must also be of a good quality.
What does Energig recommend?
Our recommendation should be seen as a guide and not necessarily a definite truth. You can always write / call us and talk about your situation.
Start Battery We recommend using it to start your engine and anything that requires a lot of power for a very short time, but not for so much else. AGM Batteries AGM is for you who want a deep cycle battery but can not find the last few dollars for a GEL/lithium battery. It’s 90% of the times better with a GEL or even better, a lithium battery They are very vibration resistant and therefore they are good in cars/boats/campers GEL Batteries They sometimes lack the ability to receive power quickly and therefore they are not quite as good at wind turbines as AGM/Lithium, but they are better at coping with deeper discharges and if you need it, you should look at GEL. Eg. to a Offgrid house. We normally recommend GEL rather than AGM. Lithium iron phosphate (lifepo4) batteries The battery can do it all. Very deep discharges, very long life, it’s fast for both up and down charging. Can be charged with very high current and thus in a short period of time. Overall, it’s just the best battery in the market today.
Below you can see the batteries that Energig has tested and which is of high quality and that we stand for: