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Old 05-28-2006, 10:44 AM   #1
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Default lipo treatment

I'm curious as to how lipos need to be treated.
How frequently can you run them, typical charge times per 1k of mah @ recomended amps and ect. If there is a need for any sort of maintanance, equalizer and ect.
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Old 05-28-2006, 04:14 PM   #2
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Old 05-28-2006, 05:52 PM   #3
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To the best of my knowledge you can run a LiPo pack as many times in a day as you can charge it. I've noticed that my packs (Orion 4800) heat up to approximately 105F (ambient temp of 95F) while running and will actually cool down during charging.

Typical charge time to put 1000 mAH into a pack will depend on the capacity of the pack. You will generally charge LiPos at 1C (4800 mAH pack at 4.8A for example). Therefore a higher capacity pack will charge faster in terms of mAH per interval of time. As a rule it will take over an hour to fully charge an empty LiPo pack when charging at a 1C rate because there are two charging phases. During the first phase a constant current is applied to the pack until the total voltage equals 4.2V times the number of cells (ie. 2 cell would 8.4V). In the second phase the charge current is slowly stepped down until the pack is full.

Maintenance is limited to using a balancer once in awhile (I've read every 15-20 charge cycles).
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Old 05-28-2006, 06:16 PM   #4
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What kind of charge times do you deal with from about a 35% discharge from the packs you are using. "About the equivalent of 5 minutes of off road mod".
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Old 05-28-2006, 11:40 PM   #5
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It's hard to say, every situation will be different. For example, my T4 with a Novak GTB / Velociti 6.5 geared at 16/87 requires approximately 1000 mAH to complete a 5 minute heat / main - your setup may be drastically different. I will usually run three heats on a fully charged Orion 4800 LiPo pack before I charge it up again. At this point it will take between an hour and ten minutes to an hour and twenty-five minutes to completely charge. The second phase (constant voltage) of the LiPo charge cycle is slower than the first and the pack will usually be 90% full when starting the second charge phase.

In my situation, I'm probably leaving about 1800 mAH in the pack after three heats. To reach 90% charge (~4300 mAH) will require around 2500 mAH. At a 1C charge rate (4.8A in this case) it would take around 32 minutes to put the 2500 mAH into the pack and the second charging phase would begin. I could take the pack off at this point and get most of the capacity from the pack without having to wait for the slower second charge phase to complete.

From what I've read, Orion recommends that their 4800 pack not be used to more than 80% capacity; this translates to 3840 mAH used, or 960 mAH remaining. This means the delta between 90% charged and 80% discharged is 3360 mAH (4320 - 960). I could run three heats without exceeding the 80% discharge or having to wait the entire hour plus for the pack to reach full charge. In summary, given my circumstances I can run three heats with capacity to spare from 38 minutes of charge time. If my explanation isn't 100% clear let me know and I'll try to clarify the best I can.

Keep in mind that different packs from different vendors will have different ratings and recommendations for use. An 8000 mAH pack from Thunder Power or MaxAmps would require only 23 minutes during the constant current charge phase to replenish the 3000 mAH I would use to complete three heats with my existing chassis / motor because of the higher charge rate (1C for 8000 mAH pack is 8A). Pack capacity and the average current requirements of your vehicle will determine how long it would take to replenish the energy used during one heat race.

Next time I race, I'll keep an eye on my charge times aftewards to see if my theoretical calculations work out.
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Old 05-29-2006, 12:06 AM   #6
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Is there anything wrong w/ running it b4 its been fully recharged? If I was to run 5 minute heats w/ a 30 minute interval could I just charge and race w/out any problems if I was running a similar system?
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Old 05-29-2006, 12:11 AM   #7
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To the best of my knowledge there shouldn't be any problem running a pack before it's fully charged. It should provide pretty much the same performance at 90% charged as 100% charged.
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Old 05-29-2006, 03:33 AM   #8
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i got a 800 mah pack....is that any good to use for a RX pack? its a 2 cell....7.4V
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Old 05-29-2006, 05:26 AM   #9
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you need a resistor... just get a 6.0v pack.
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Old 05-29-2006, 09:20 AM   #10
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LiPo packs don't come in a 6V configuration. A single LiPo cell has a nominal voltage of 3.7V. Thus a 2 cell pack would 7.4V, a 3 cell would be 11.1V and so on.
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