Now you guys got me to pull up my old post. Helios - In addition to what is below, only one motorcycle lithium battery has a built-in management system and without it to match individual cells the Li battery will need to be replaced faster than the less expensive AGM. So it costs more now and more later. btw - external plug-in chargers can not address cell balancing within the battery case, i don't care what their marketing says, they simply charge the cells in series.
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Leaving a Li battery on most maintenance/trickle type chargers will also kill them much faster than a AGM.
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The Li batteries get away with selling you less Ah capacity and it works great in warm weather because the discharge rate is so flat, but in the 30s (F) you will have an under-size battery for starting. The bike better start fairly quick because it won't crank as long.
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Short the terminals of a AGM and you will get a big spark and probably melt the cable. If you inadvertently short the terminals of a lithium battery you don't want to be close!!! You'll explode the pouches, the black goo is really hard to clean off, and the "smoke" is a mix of acids. BTDT
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So with the above adding to copying below from my post on ADV, you can see why I consider lithium not to be an upgrade, it is an alternative.
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ADV already has a 100+ page thread about the different battery types, here, with a unofficial moderator who knows his battery stuff:
http://www.advrider.com/forums/showthread.php?t=757934
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While I wouldn't get rid of a Li battery if the bike already had one installed from a previous owner, I highly recommend not buying one for an adventure bike. The AGM remains the right battery for 95% of the users here.
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We have two basic battery types available; AGM and lithium ion. The AGMs are lead-acid chemistry, very similar to the old cells with the removable caps, but with improvements which inhibit plate warpage and sulfidation. This is why the AGMs last years longer than the old batteries. They also are sealed and have no problem when the bike ends up in unusual positions. AGM is what nearly all bikes now come with stock.
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The positive two aspects of lithium batteries are (1) lowest weight (think cell phones and race bikes) and (2) a flat discharge curve through the range/state of charge. That flat discharge curve mean that your starter motor will have one speed - fast - until the cell is discharged. However, the weight saving is probably less than the weight of mud you will pick up on a ride, so that weight savings really doesn't make much difference for the high price. Further, when you are miles from a road the lithium battery will work and then it won't. You don't get the warning that it is nearly discharged which an AGM will provide.
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While both battery types lose capacity when cold, the capacities are typically specified for room temp. Compare charts which show the loss of capacity when the temperature gets into the 30s and less and the Li-ion loses capacity a LOT faster. Li-ion electrolyte is a very light petroleum that feels similar to a thin baby oil or like a clear version of transmission fluid and suspended in the oil are the lithium ions. The oil thickens as temperatures fall below about freezing, making it harder for the ions to move and the internal resistance of the cell increases almost exponentially, so the efficiency of the cell decreases. Thinking you might be able to warm he cell to get more capacity, you could turn on the headlight, which depletes charge fast, the cells do not evenly heat, so you still aren't getting full capacity, and I've seen tests where about 30% of the energy goes into heat within the cell. Again, for an adventure bike, this is probably not what you want.
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Charging lithium batteries in freezing conditions can reduce their life very fast. They also don't last well when they get hotter than about 160F and a lot of motorcycle batteries are next to an exhaust &/or used in very hot climates. (black paint in the sun can get to 190F)
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Li batteries used as motorcycle batteries do not contain actual lithium metal and if there is a fire, it is the electrolyte oil which burns. They burn hot, because oxygen is in the cell with the flammable electrolyte. Lithium ion cells also are more difficult to control the charge and if damaged can overheat or burn, as opposed to a lead-acid battery, which generally just shorts out internally and becomes unusable.
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For these trade-offs, you might save 8 lbs in a 300+ lb bike which is carried fairly low in the first place. For context 4 gallons of gas is about 24 pounds and for most bikes is carried much higher.
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