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Technical Comparisons

Technical Comparisons

General Flooded Lead Acid Battery: The Lead Acid Battery works by using lead and lead(IV) plates which are submerged in sulfuric acid. Lead(IV) oxidizes the lead plates and creates an electrical current. All currents are propelled by a Electromotive Force: This force is read in volts. Lead Acid Batteries have 2.1 nominal volts per cell and have 6 cells connected in series. This gives the battery a nominal voltage of 12.6 volts and can be safely charged at 2.4 volts per cell giving a total float voltage of 14.4 volts. The lead acid battery is also the only battery which requires maintenance due to off-gassing: which is not environmentally friendly. This battery is also very heavy(often weighs more than twice as much as a lithium) .   It is the heaviest type of battery of the big 3. The only true advantage of this type is low cost. These batteries also have the lowest expected battery life of 2-5 years depending on if a trickle charger is used.

General   AGM Battery  - The AGM battery is a Sealed Lead Acid Battery with less electrolyte than that of Flooded Lead Acid Style Battery. They have electrolyte solution impregnated in a moistened separator rather than flooded in electrolyte solution like conventional lead acid batteries. AGM batteries allow for faster charging and instant high load current on demand. The individual cells have a fully charged voltage of 2.4 volts and with 6 cells in series have a float voltage of 14.4 nominal volts. These batteries   off-gas at a rate which is less than the flooded lead acid battery described above, but more than lithium iron phosphate(Arc-Angel Batteries) which do not off gas. This off gassing reduces   battery life and potentially damages   the environment. Furthermore, AGM batteries will last around 4 to 7 years if they are taken care of by using a maintenance charger.  

ARC-ANGEL BATTERY(LiFePO4) - Finally the pinnacle of modern technology: Lithium Iron Phosphate Batteries. The batteries work with a positive electrode made with a chemical compound called LiFePO4, and the negative electrode is made from carbon. In between these is an electrolyte solution. When charging the positive electrode gives up some of its lithium ion which attaches   to the carbon or negative side. When discharging i.e. providing power this process is reversed. In both cases electrons flow in the opposite direction to the ions around the outer circuit. However electrons do not flow through the elecrolyte.   Each battery cell   has a nominal voltage of around 3.2 volts, when 4 are connected in series you get 12.8 nominal volts. These can be charged safely at 3.65 volts per cell giving a maximum voltage of 14.6 Volts. Furthermore these batteries never off gas making them environmentally friendly and maintenance free. This style of battery is   also the lightest of the big 3 weighing in at around 50 percent (often less) of   the AGM and Flooded Lead Acid types. Furthermore, these batteries provide even faster charging than AGM and also are equal or better in terms of Cold Cranking Amps, Reserve Capacity, and Capacity. Also it should be noted that LiFePO4 batteries last at around 10+ years assuming a maintenance charger is used.

Capacity Comparison - In general capacity of batteries is reduced when discharge currents are increased this is certainly true of flooded lead acid and AGM batteries, however LiFePO4 batteries are generally not affected by this unless temperatures drop below freezing. This is because LiFePO4 batteries have self-heating properties due to the Nernst equation which predicts battery voltage rise with temperature. Voltage rising from self-heating counteracts the increased resistance and loss in capacity loss due to Peukert's Law (explained below). These properties have been noted in several studies in recent history for more information please see here: Peukert Revisited. However as mentioned above Peukert's Law is highly important when comparing Lead Acid and AGM batteries. This law is essentially used to show how capacity decreases with an increasing discharge current. Higher discharge currents are output by the battery when electrical loads are increased beyond what the manufacturer rated it for which is very common. The aforementioned capacity reduction is more severe when the Peukert's Exponent is higher. If the constant is given by the manufacturer it should be used. However the constant can also be calculated based upon the manufacturers listed specifications. These specifications can be entered into any Peukert's exponent calculator you can find online I like using this one here: Peukert Calculations   The equation is listed below:

I t = C \left(\frac{C}{I H}\right)^{k-1},

H  is the rated discharge time (in hours),

C  is the rated capacity at that discharge rate (in ampere hours),

I   is the actual discharge current (in amperes),

k   is the Peukert constant (dimensionless),

t   is the actual time to discharge the battery (in hours).

So for an example lets take a group 35 battery from a leading manufacturer whom rates their battery at 44Ah with a C-Rate at 20 hours or C20. So based on this we can assume the manufacturers rated capacity was 44/20 = 2.2A. This is way too low for a car when all electrical loads are turned on. Now peukerts law comes in to play, lets assume the reserve capacity for this battery is 90 minutes and the discharge current to get this time was 25A. If we put this into the calculator mentioned above we get a Peukert's exponent of 1.07. Now lets assume a 50A discharge rate and punch in the numbers to the above equation. We get an effective capacity of 35Ah. So what this means in practical terms is that the batteries you see in stores don't really have the capacity that it might appear when you consider real world applications. In my example a leading AGM rated at 44 Ah ended up at 35Ah while a Group 35 from Arc-Angel doesn't get affected by this as much and stays at approximately 40Ah.

Charging Information - On a final note Lithium Iron Phosphate Batteries will work fine with a vehicles alternator as they generally output around 14.4V-14.6V which is in the acceptable range for charging,. However when wanting a top off charge when the car is not in use for simplicities sake we recommend a charger built for LiFePO4 batteries with a constant voltage/constant current algorithm. A lead acid charger can also be used, but there are some things to watch for please see our FAQs section for more information.

However that's just the overly technical engineer in me but most important to note is this. These batteries tend to run at the back of the pack in terms of Cold Cranking Amps (CCA), Reserve Capacity (RC), and Capacity (Ah).  

When comparing batteries Lithium is clearly the superior technology.   Arc-Angel LiFePO4 Batteries stand tall above the rest on performance, what more could ask for in a battery! For racing applications the choice is clear the Arc-Angel Lithium Battery!

As a quick side note it is a universal fact for all battery chemistries that a maintenance charger will help to extend life. If one of our batteries is purchased we recommend getting one made for LiFePO4 batteries to fully maximize battery life. However other charger types can be used please see our FAQs section for more information. It should also be noted that if you live in cold climates where temperatures can go below freezing for long periods of time the life can be reduced. Using a battery blanket heater can help combat this and extend battery life.

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