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You can probably find a lithium iron oxide battery that will fit in it. If you get one and don't discharge it past 72% it will last 10,000+ recharge cycles; in other words, you wont have to replace it again.
Valence specializes in Lithium Phosphate. It is very safe, relatively speaking and will likely out last you machine.
Tell them what you are using now including dimensions. They may have a replacement for you.
One danger in switching from Lead Acid to Lithium that's possible is thruster burnout.
Lithium discharges much differently than LA and it might be an iussue.
Lithium creates much more heat than LA in discharge also. May or may not be a problem with other components in the Apollo.
One danger in switching from Lead Acid to Lithium that's possible is thruster burnout.
If the voltages are similar a Lithium Battery vs a lead acid battery won't cause the "thruster" or motor to generate more heat.
The motor could produce more heat if the Li_ion battery imposes a higher voltage than the SLA battery.
If the design depends on a duty cycle effectively limited by the capacity of a SLA battery, a much higher capacity Lithium Ion pack, even if well matched for voltage, could cause overheating of the motor simply because of the longer possible run times. This would be problem only if the Li-Ion battery was used in a "continuous" or high duty cycle application.
Scooters with adequate thermal management, and motors not operated at or close to saturation should tolerate higher capacity Li-Ion packs.
Originally Posted by sailcsy44
Lithium creates much more heat than LA in discharge also. May or may not be a problem with other components in the Apollo.
The discharge reaction of both Li-Ion and Lead Acid batteries is exothermic, but it is not the chemical reaction itself that is the primary source of heat in either battery.
The internal resistance of the battery is responsible for most of the heat gain.
SLA batteries do exhibit very low internal resistance, although newer high discharge current Li-Ion cells are much better than some of the earlier Li-Ion cells produced.
If you take two batteries of equal voltage and amphour capacity, one Li-Ion and one SLA and induce the same current flow in each, the Li-Ion pack will produce more heat.
Relying solely on internal Resistance per amphour capacity will provide a distorted view of performance of, and the power dissipated as heat of SLA's vs Li-Ion Batteries.
Li-Ion batteries enjoy a huge advantage in both Specific Energy and Energy Density vs SLA batteries. Li-Ion batteries offer about 5 times the "watthours / lbs" of a typical SLA battery.
For many applications that means the Li-Ion pack can be about 5 times greater capacity than a similar SLA.
For example a 50 amphour Li-Ion battery vs a 10 amphour SLA. For the same current flow which will have the lower total internal resistance? My money is on the Li-Ion.
We have used LA, Silver Zinc and Li Ion extensively and what I saw in discharge was that the Lithium tends to discharge at a constant voltage while silver zinc drops then plateaus for long period. LA starts dropping in voltage as soon as you begin the draw. The drop in LA is slow of course, in our case 2-3 volts over 3 hours but it is a constant drop.
I am far from being an expert but I have monitored the volts/amps during many dives and I felt the thrusters were suffering greatly from the constant power supplied by the Li-Ion.
Extensive modifications were required to finally operate at full power over the life of the battery.
We have used LA, Silver Zinc and Li Ion extensively and what I saw in discharge was that the Lithium tends to discharge at a constant voltage while silver zinc drops then plateaus for long period. LA starts dropping in voltage as soon as you begin the draw. The drop in LA is slow of course, in our case 2-3 volts over 3 hours but it is a constant drop.
I am far from being an expert but I have monitored the volts/amps during many dives and I felt the thrusters were suffering greatly from the constant power supplied by the Li-Ion.
Extensive modifications were required to finally operate at full power over the life of the battery.
Li-Ion batteries operate from about 4.2 volts per cell to about 3 volts, and discharge in a more or less straight line, meaning the voltage is changing constantly.
Nickel batteries will exhibit a much flatter voltage discharge curve, with a pronounced "knee" at the end of discharge.
I suspect that any "thruster" stress you have observed is a result of a higher than expected voltage being imposed on the motor.
Lead acid batteries are nominally 2 volts per cell, which are often combined in series to produce voltages of 12 vdc (6 series cells) or 24 vdc (12 series cells ) etc.
Li_ion batteries have a nominal cell voltage of 3.7 which prevents building batteries with the same nominal voltage as typical lead acid packs. For example a 6 sereis Li_ion pack will be nominally 22.2volts and a 7 series pack will be 25.9 volts.
If the 7 series pack is used the voltage imposed on the motor is higher than what it would see with a SLA battery. In addition if same weight of Li-Ion batteries is used to replace a SLA battery the resulting pack will be 4-5 times greater capacity.
A 5 x times greater capacity combined with higher initial voltage (7 x 4.2 = 29.4 volts), will result in a battery that will due to it's much lower internal resistance, output a voltage, even under load that is much higher than a 6 cell, 24 volt nominal SLA.
It's worthwhile remembering that capacity vs load also impact the apparent slope of any discharge curve.
A 10 amp hour SLA driving a 10 load will have a pretty steep curve. A 50 amp hour SLA driving the same load will have a much flatter curve, in part due to the 5:1 reduction in "C" rate of discharge, and in part due to the increase in the effective capacity of the battery at lower "C" rates.
This phenomena is, I suspect, responsible for "constant" voltage you mistakenly attribute to Li-Ion batteries.
Tobin
Last edited by cool_hardware52; November 21st, 2008 at 12:56 AM.
Reason: spelling
<snip> A 5 x times greater capacity combined with higher initial voltage (7 x 4.2 = 29.4 volts), will result in a battery that will due to it's much lower internal resistance, output a voltage, even under load that is much higher than a 6 cell, 24 volt nominal SLA.
It's worthwhile remembering that capacity vs load also impact the apparent slope of any discharge curve.
A 10 amp hour SLA driving a 10 load will have a pretty steep curve. A 50 amp hour SLA driving the same load will have a much flatter curve, in part due to the 5:1 reduction in "C" rate of discharge, and in part due to the increase in the effective capacity of the battery at lower "C" rates.
<snip>Tobin
Concisely said, and exactly as observed under the experiments we performed at the Tahoe Benchmark. I might add that the Lead Acid results exhibited a pronounced slope that significantly hindered their performance, and belied much of their "common knowledge" reputation.
Concisely said, and exactly as observed under the experiments we performed at the Tahoe Benchmark.
BTW, VERY nice work, both the trial and the written report. I hope that manufacturers find a way to be more supportive, by provding equipment for testing, for future trials.
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Originally Posted by sailcsy44
