Batterityper ombord - start vs forbruk vs hybrid, blysyre vsAGM

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"Sunking" på solarpaneltalk.com har jeg håndrappet disse setningene fra:

 

Derek som han heter er en ganske direkte herremann, men ikke helt uten erfaring.

 

WTF Is The Deal With Batteries

 

OK so it is catch title but a question I answer every day and frankly tired of answering. So here is my canned answer.

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In the lead acid family there are 3 primary groups of Starting-Lighting-Ignition (SLI), Hybrid deep cycle (aka Marine, Golf Cart, RV, etc.), and true Deep Cycle............

 

* SLI Batteries are just what they imply. A battery that is designed to crank an engine and get it started. They are constructed with multiple thin spongy plates to provide maximum surface area which lowers the internal resistance as low as possible. Low resistance means it can deliver very high short burst of current with minimum voltage sag or voltage drop. That is great for starting engines, and then recharged very quickly with high amounts of current. It is exactly what your vehicle needs, but sucks for RE applications. If you try to deep cycle them, those thin spongy plates dissolve and end up in the bottom of the battery jar in 100 cycles or less. DO NOT USE SLI batteries for RE applications except in an emergency. Enough said as you should get the point.

 

* True Deep Cycle Batteries are exactly opposite, and generally the best choice for everyday use in RE applications. They are the exact opposite of SLI batteries. They have fewer but very thick heavy smooth plates made to last a long time or up to 4000 cycles if discharge no more than 20 to 30% before being recharged immediately fully. The trade-off is they have limited discharge and recharge current rates. If you discharge then to fast or too high of a rate they will have excessive voltage sag or voltage drop.

 

As a Rule of Thumb you want to limit the maximum charge/ discharge rates of Flooded Lead Acid (FLA) to C/8-Hour rate. Where C = the Amp Hour (AH) specification of the battery at the 20-Hour discharge rate. For example a 100 AH battery C/8 = 100 AH / 8 H = 12.5 amps. So if that battery is 12 volts @ 100 AH it can handle a maximum inverter of roughly 12 volts x 12.5 amps = 150 watts. The minimum charge rate for FLA batteries is C/12-Hours to prevent stratification of the electrolyte. Stratification means the heavier acid well settle to the bottom and float the lighter water on top. A minimum C/12 charge rate will cause rolling of the electrolyte and stir it up.

 

AGM True Deep Cycle Batteries by construction have lower internal resistance and can take higher charge and discharge rates. As a rule of thumb; They can charge/discharge up to a C/4-Hour rate. They really do not have a minimum charge rate like FLA because the electrolyte is not liquid per sey, but for RE purposes C/20 is about as low as you want to go with them. However AGM batteries are expensive, about 100% more than FLA for a given capacity. They also do not last as long as a FLA of only about half the cycle life. So AGM is best used in mobile applications where weight and spillage is a concern, higher charge/discharge is a priority, unusual mounting orientation, small confined air tight space (gas build up or explosion from build-up of hydrogen), or extreme artic cold weather conditions. In other words you had better have a good reason to justify the expense and shorter cycle life.

 

* Hybrid Batteries are useful in RE applications. Like the name implies they are a cross between SLI and True Deep Cycle batteries. They have fewer thicker plates than SLI batteries to obtain some deep cycle capability, and lower internal resistance for decent high current charge/discharge rates. However the plate s are not as thick and heavy as True Deep Cycle batteries. So what you get is trade-offs.

 

They can deliver/take higher discharge/charge currents than True Deep Cycle, but not as much as SLI batteries. On the other hand they do not have the high number of cycles as True Deep Cycle batteries. For the FLA types you still have the lower limit charge rates of C/12 to prevent stratification, but on the charge/discharge side of FLA hybrids you can go as high as C/4, and some cases C/2.

 

AGM hybrids are extremely expensive and resemble SLI batteries more than True Deep Cycle. They are used in UPS systems, Golf Carts, Floor machines, and Electric vehicles where moderate amounts of high current is required with som efair cycle life. Hybrid AGM's have very low resistance and can take a C/1 or higher charge\discharge rates. The downfall of them they only have 300 to 500 cycles in them. Hybrids are best used in systems that are infrequently used with high discharge rates like Emergency power and UPS systems.

 

Be careful with Hybrid marketing because they are often claimed to be Deep Cycle. The way you can tell if it is a Hybrid is in the specifications. If the specs list CCA, MCA, and\or RC, it is a hybrid battery. True Deep Cycle Batteries only have AH specification at various discharge rates.

 

Parallel Battery Arrangements should be avoided to obtain required AH capacity unless necessary. Very rarely is it necessary as battery AH capacity varies from 10 to 4000 AH. Without going into a lot of detail the reason boils down is you will significantly shorten battery cycle life. When you parallel batteries you cannot equalize the the currents. This forces 1 string to do most of the work, leaving the other strings to be under worked. The end result weakens all the batteries and shorten cycle life.

 

Last note is I did not speak of Gel batteries for a very good reason. DO NOT USE THEM. Enough said.

 

 

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