LIE POOZ
09-18-2008, 07:15 PM
#1
LIE POOZ
Hey all,
Im sure its been answered somewhere on this forum, but i ran a search and couldnt pin-point anything.
I recently made the switch from nimh to lipos, i got two new ip3800 packs from trinity. There not really that main-stream in the us yet. Anyway, im new to lipo so i was wondering whats the point in the balancer? Do i have to use it everytime i charge, or does it only help balance the pack when your discharging? Also, i was told that lipos dont drain their voltage? I charged up a pack last night, around 11pm, and i checked it today around 8pm and the voltage was around 8.25, i have the team checkpoint tc1030, also i noticed theres no-repeak option? is it not possible to re-peak lipos or do i just re-charge them? when i did recharge them the voltage stopped at 8.50? seems low? I was also told that i should charge at whatever the pack rating is, ex 3800 charge at 3.8 however trinity said i could charge at up to 5amps? Just looking to get some real answers? and perhaps save my house from burning down.
thanks for the time,
tenpins77
Im sure its been answered somewhere on this forum, but i ran a search and couldnt pin-point anything.
I recently made the switch from nimh to lipos, i got two new ip3800 packs from trinity. There not really that main-stream in the us yet. Anyway, im new to lipo so i was wondering whats the point in the balancer? Do i have to use it everytime i charge, or does it only help balance the pack when your discharging? Also, i was told that lipos dont drain their voltage? I charged up a pack last night, around 11pm, and i checked it today around 8pm and the voltage was around 8.25, i have the team checkpoint tc1030, also i noticed theres no-repeak option? is it not possible to re-peak lipos or do i just re-charge them? when i did recharge them the voltage stopped at 8.50? seems low? I was also told that i should charge at whatever the pack rating is, ex 3800 charge at 3.8 however trinity said i could charge at up to 5amps? Just looking to get some real answers? and perhaps save my house from burning down.
thanks for the time,
tenpins77
09-18-2008, 08:41 PM
#3
Lipo has both a max and min voltage. Charging with a lipo type charger uses a CC/CV charge sequence. The lipo is charged at constant current until the cell max voiltage of 4.2v is reached. then switches to constant voltage holding at 4.2v/cell (2S would show 8.4v) until batt has taken as much as its condition will allow.
Min voltage is considered 3.0v/cell but some say 2.7-2.8v/cell. Overdischarging below the min voltage can possibly led to a swollen or puffed cell which is a potentially dangerous situation - usually recommended a lipo with puffed cell be discarded.
Balancer evens voltage between cells so they start at the same voltage. This lessens the chance for overdischarging an individual cell. Do you need to do it every time? No, not really. Balancing on good quality cells (especially 2S) is not that critical. I used to see recommendations to balance them every 15-20 charges or so. Its best to balance while charging or after charging - you're trying to protect cells from overdischarging. Lipo's self discharge rate is very very low. Good quality cells may lose only a few percent sitting for months. There is no repeak for lipo - if its at 95%, I'd just run it and recharge it normally.
Charge rate is generally recommended as 1C, some of the newer lipos can be charged at 2C. Jury is still out on whether that affects lipo life (cycles)?? If you've got a good dvm, check cell voltages and see how balanced they are staying. My best (most expensive - NeuEnergy) stay within .002 - .003v. Experience is advising not to run them down all the way to low voltage cutoff - seems to hbe harder on them. Def need to be using some kind of lvc - some esc have it built-in others do not - need separate lvc in that case to protect batts. Other way is to set lvc at a higher value - I set mine at 6.2-6.4v for a little safety margin.
Min voltage is considered 3.0v/cell but some say 2.7-2.8v/cell. Overdischarging below the min voltage can possibly led to a swollen or puffed cell which is a potentially dangerous situation - usually recommended a lipo with puffed cell be discarded.
Balancer evens voltage between cells so they start at the same voltage. This lessens the chance for overdischarging an individual cell. Do you need to do it every time? No, not really. Balancing on good quality cells (especially 2S) is not that critical. I used to see recommendations to balance them every 15-20 charges or so. Its best to balance while charging or after charging - you're trying to protect cells from overdischarging. Lipo's self discharge rate is very very low. Good quality cells may lose only a few percent sitting for months. There is no repeak for lipo - if its at 95%, I'd just run it and recharge it normally.
Charge rate is generally recommended as 1C, some of the newer lipos can be charged at 2C. Jury is still out on whether that affects lipo life (cycles)?? If you've got a good dvm, check cell voltages and see how balanced they are staying. My best (most expensive - NeuEnergy) stay within .002 - .003v. Experience is advising not to run them down all the way to low voltage cutoff - seems to hbe harder on them. Def need to be using some kind of lvc - some esc have it built-in others do not - need separate lvc in that case to protect batts. Other way is to set lvc at a higher value - I set mine at 6.2-6.4v for a little safety margin.
09-21-2008, 09:39 AM
#4
Awesome answer.
09-25-2008, 11:47 AM
#5
+1 on the voltage cut off info and the min. settings for discharge!
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