quick Lipo question
01-13-2012 | 02:32 AM
#1
quick Lipo question
I have a quick question.
When running 2 lipos together in series do they both have to be them same? I found 2 batteries on Ebay being sold together. They are both the same brand, both are 2s, both are 5000mah but one is rated at 40c and the other is rated at 50c. would it be safe to run these two batteries together in series? Why or why not?
Thanks
When running 2 lipos together in series do they both have to be them same? I found 2 batteries on Ebay being sold together. They are both the same brand, both are 2s, both are 5000mah but one is rated at 40c and the other is rated at 50c. would it be safe to run these two batteries together in series? Why or why not?
Thanks
01-13-2012 | 04:15 AM
#2
Senior Member
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RE: quick Lipo question
Ultimately there's only 1 supreme rule and that is never to allow any 1 cell get overcharged or undercharged , so the only realistic rule is that all cells must be the same CAPACITY.
Many users also recommend that the specs be the same too , in addition to the number of uses, health, brand, age ect. This is an attempt to satisfy the realistic and the supreme rule.
They do not have to contain the same number of cells or be the same voltage.
Many users also recommend that the specs be the same too , in addition to the number of uses, health, brand, age ect. This is an attempt to satisfy the realistic and the supreme rule.
They do not have to contain the same number of cells or be the same voltage.
01-17-2012 | 04:49 AM
#3
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From: Goode,
VA
RE: quick Lipo question
The short answer is no, it would not be safe.
The long answer is yes, it would be safe under some circumstances.
As guver said, the reason the "supreme rule" exists is to make it easier for the average user to not over or under charge a LiPo cell.
By running a pair of batteries that are the same age, C rating, capacity, etc. it is pretty simple to maintain and use them. Balance charge, check cell voltage, store at 3.85v per cell, use as desired, and typically you won't have any issues.
You can run the two batteries you describe, just understand that because the 2nd battery is capable of discharging at a higher rate, it does have the potential to get to LVC faster. You will want to get a small $5 LVA device from ebay and use it to check cell voltages the first few times you use it, to see how much faster or slower it is discharging than the first one. Check it every 5-10 minutes during the runs and monitor the cell voltage. Once you've run it a few times and checked it out, you'll know how to manage the two batteries.
It's not that it is impossible or causes cancer in lab animals. It just means you need to do more hands on monitoring to keep your batteries happy.
If you would rather plug in and go, then get matching batteries.
The long answer is yes, it would be safe under some circumstances.
As guver said, the reason the "supreme rule" exists is to make it easier for the average user to not over or under charge a LiPo cell.
By running a pair of batteries that are the same age, C rating, capacity, etc. it is pretty simple to maintain and use them. Balance charge, check cell voltage, store at 3.85v per cell, use as desired, and typically you won't have any issues.
You can run the two batteries you describe, just understand that because the 2nd battery is capable of discharging at a higher rate, it does have the potential to get to LVC faster. You will want to get a small $5 LVA device from ebay and use it to check cell voltages the first few times you use it, to see how much faster or slower it is discharging than the first one. Check it every 5-10 minutes during the runs and monitor the cell voltage. Once you've run it a few times and checked it out, you'll know how to manage the two batteries.
It's not that it is impossible or causes cancer in lab animals. It just means you need to do more hands on monitoring to keep your batteries happy.
If you would rather plug in and go, then get matching batteries.
01-17-2012 | 08:07 AM
#4
Senior Member
RE: quick Lipo question
I would not run a high C and a low C battery in series.
The reason being that the higher C battery can flow more current than the low C one. The circuit they are in does not care about the batteries ratings, it only wants to draw the current it needs. If the need is higher than one battery can safely provide but the other can flow the higher current then the higher C battery will still flow the higher current - through the lower C battery. And that will damage the lower C battery.
Runnig them in parallel would be fine, series, I would not.
The reason being that the higher C battery can flow more current than the low C one. The circuit they are in does not care about the batteries ratings, it only wants to draw the current it needs. If the need is higher than one battery can safely provide but the other can flow the higher current then the higher C battery will still flow the higher current - through the lower C battery. And that will damage the lower C battery.
Runnig them in parallel would be fine, series, I would not.
