Senton Lipo Batteries only holding partial charge

[yillbs]

I understand how lipo's work, so there is no confusion. However, I noticed the truck shuts off when the cells his 3.6V. When I charge them back up, I'm only putting in ( according to the charger ) 3500MAh. They are 5200MAh packs. that's a pretty big difference.

They are ovionic batteries. ( link here : https://www.amazon.com/gp/product/B07L69B8V6/ref=ppx_yo_dt_b_asin_title_o07_s01?ie=UTF8&psc=1 ).

I get about 20-30 minutes run time, but that's also on 25% throttle. I have two of them, and they behave identically. Is this a bad brand, or, is there a setting somewhere on the truck I need to modify / change / alter?

Thanks!

 

[3d-rc.myshopify.com]

I wouldn't worry so much about the mah.. as long as voltage is correct. There is still a charge in the to begin with when charging. I have had the same battery charge to a different mah every time. Sometimes even way over its rating.

 

[yillbs]

I wouldn't worry so much about the mah.. as long as voltage is correct. There is still a charge in the to begin with when charging. I have had the same battery charge to a different mah every time. Sometimes even way over its rating.

Why wouldn't I worry about the MAh? This is the capacity of the battery. a 2000MAh battery will last half the time using the car as a 4000MAh battery would. That's why my question is about why the batteries would only hold a portion of what's available to use. Is my logic incorrect?

 

[jondilly1974]

Why wouldn't I worry about the MAh? This is the capacity of the battery. a 2000MAh battery will last half the time using the car as a 4000MAh battery would. That's why my question is about why the batteries would only hold a portion of what's available to use. Is my logic incorrect?

Actually, too small of a MAH rating won’t even run at all in some cases. It is pretty important to have a large enough lipo for the given task.

 

[yillbs]

Actually, too small of a MAH rating won’t even run at all in some cases. It is pretty important to have a large enough lipo for the given task.

That doesn't make much sense either. The MAh rating is nothing more than the capacity of the battery. As long as it has the amperage to push power to the ESC, then it will run, even if just for a few minutes due to a rather low MAh rating. For instance, a 2s 1500Mah 50c battery will still power whatever it's in, as long as it has the amperage to power the ESC. I'm not sure how the capacity of the battery would have a deciding factor in whether something will actually take the power.

Nonetheless, that doesn't really answer my question as to why the batteries would only take a partial charge. I'm thinking the batteries just aren't very good if they're only depleting to 3500MAh.

I guess we could use a samsung phone as an example. The galaxy note 10 has a 4000MAh battery. If it were to only hold a charge of 2500MAh, the battery would be considered bad, and need to be replaced. The same goes for a laptop battery. Their is generally a 10% buffer, but not 1600MAh worth of buffer. Perhaps i'm asking my question incorrectly?

 

[jondilly1974]

That doesn't make much sense either. The MAh rating is nothing more than the capacity of the battery. As long as it has the amperage to push power to the ESC, then it will run, even if just for a few minutes due to a rather low MAh rating. For instance, a 2s 1500Mah 50c battery will still power whatever it's in, as long as it has the amperage to power the ESC. I'm not sure how the capacity of the battery would have a deciding factor in whether something will actually take the power.

Nonetheless, that doesn't really answer my question as to why the batteries would only take a partial charge. I'm thinking the batteries just aren't very good if they're only depleting to 3500MAh.

I guess we could use a samsung phone as an example. The galaxy note 10 has a 4000MAh battery. If it were to only hold a charge of 2500MAh, the battery would be considered bad, and need to be replaced. The same goes for a laptop battery. Their is generally a 10% buffer, but not 1600MAh worth of buffer. Perhaps i'm asking my question incorrectly?

But in reality lipos don’t work that way. As you reduce the capacity of a lipo, the amount of voltage sag increases. So for instance when a pack is rated at 5000mah is fully charged and put to use under a given load, it may output 4.0vdc. Take out 2000mah under that load and now it is only able to deliver 3.5vdc under that same load. Next thing you know LVC kicks in.

Under the same load and circumstances, you start out with a 3000mah pack and you hit that same 3.5vdc off the rip. It will act the same as a discharged 5000mah pack.

So yes, size does matter.

 

[3d-rc.myshopify.com]

And when you are charging a flat battery it isn't at 0% charge. So if you tried to shove 5000mah in a 5000 mah battery that is say 40% charged you are asking for a lipo fire... the mah limit on a charger is more of a secondary back up to shut off the charger incase it doesn't stop charging at the final voltage....

 

[yillbs]

And when you are charging a flat battery it isn't at 0% charge. So if you tried to shove 5000mah in a 5000 mah battery that is say 40% charged you are asking for a lipo fire... the mah limit on a charger is more of a secondary back up to shut off the charger incase it doesn't stop charging at the final voltage....

A LiPo can't hit 0%. That's kind of my point. The charger can't determine what the capacity is, but it can determine what's going into the battery, pretty accurately from my understanding. So if I can accurately say i'm putting in 3500MAh +/- 500MAh or 15% (Which is high) that would mean that the battery still has 1700MAh remaining. This is roughly 33% remaining in the battery. If the battery has 33% remaining when the cells are at 3.6V, wouldn't this indicate the batteries are just junk? I THINK what you're trying to say is the ESC needs to use more power, which dips it below the 3.6V per cell threshold, thus, stopping the motor from running. If that's the case, then don't the cars need more power / bigger batteries, I.E, a 3s car with a 3.6V limiter is vastly inefficient?

 

[razorrc]

Here's the actual answer to your question --

3.7V/cell is what's known as the nominal charge, which is why a 2S battery is stated as 7.4v and not 8.4v. This is the ideal resting voltage when the battery is approximately half charged. Lipos last longest (degrade the least) when they are at their resting voltage (half charged), and degrade most quickly fully drained or fully charged.

Your Lipo cutoff is set to a certain voltage, but most ESCs will immediately cutoff when they hit that voltage. The thing is, batteries temporarily sag under power below their at rest voltage. So you could have your ESC set to 3.5v/cell, but when running your truck it sags under that temporarily (say 3.3v) and the LVC kicks in and your truck shuts off. Then when you walk over to your truck, test the battery it says 3.6v and you're wondering why it cutoff.

So the short answer is you never get the full capacity of the battery unless you run it way low (lower than the LVC), which will damage the battery. You can lower your LVC a little bit if your ESC allows you to do it to help with the temporary voltage sag. As long as it's 3.5v+/cell after LVC has kicked in, I think it's fine. I wouldn't run a battery below 3.5v/cell of their at rest voltage test.

Be aware that motors run exponentially hotter as the voltage drops. I'm not sure why, I think the ESC is drawing more amps to compensate as the voltage goes down. I find all of my motors start climbing in temps pretty rapidly (like 20F degrees hotter than normal) when the voltage of a battery starts dropping below 3.7v/cell. So you can run them longer, but everything is more likely to degrade.

 

[jondilly1974]

Here's the actual answer to your question --

3.7V/cell is what's known as the nominal charge, which is why a 2S battery is stated as 7.4v and not 8.4v. This is the ideal resting voltage when the battery is approximately half charged. Lipos last longest (degrade the least) when they are at their resting voltage (half charged), and degrade most quickly fully drained or fully charged.

Your Lipo cutoff is set to a certain voltage, but most ESCs will immediately cutoff when they hit that voltage. The thing is, batteries temporarily sag under power below their at rest voltage. So you could have your ESC set to 3.5v/cell, but when running your truck it sags under that temporarily (say 3.3v) and the LVC kicks in and your truck shuts off. Then when you walk over to your truck, test the battery it says 3.6v and you're wondering why it cutoff.

So the short answer is you never get the full capacity of the battery unless you run it way low (lower than the LVC), which will damage the battery. You can lower your LVC a little bit if your ESC allows you to do it to help with the temporary voltage sag. As long as it's 3.5v+/cell after LVC has kicked in, I think it's fine. I wouldn't run a battery below 3.5v/cell of their at rest voltage test.

Be aware that motors run exponentially hotter as the voltage drops. I'm not sure why, I think the ESC is drawing more amps to compensate as the voltage goes down. I find all of my motors start climbing in temps pretty rapidly (like 20F degrees hotter than normal) when the voltage of a battery starts dropping below 3.7v/cell. So you can run them longer, but everything is more likely to degrade.

The reason for the higher heat is amps. Your motor draws watts. Watts are amps x volts. Say your motor needs 2000W for a given load. If you’re running 6S and your lipo is able to provide 25vdc, then it is pulling 80a. When you drain the lipo down and it can only provide 22vdc, now it’s pulling 90a. The more amps you draw, the hotter things get. If you can keep voltage high, the amps stay low. That’s why most appliances with a high wattage draw use higher voltages. Most wire is rated up to 600V, but the gauge of wire determines how many amps it can safely handle.

 

[Sensei]

Ok most of the answers are right, but missing the point of when someone pays X amount of money to get a longer run time then that is what you should get. I have over 30 lipos at the moment but I will use one pair for example that I have had a similar issue. I have two Common Sense 2000mah 7.2V batteries. One would discharge down to around 3.3v or 3.4v and would take on average a 1700-1800mah on a charge, the other would discharge to 3.4v or 3.5v and only take about 800-900mah! Tried to cycle on the charger and same results(also I really don't recommend cycling a lipo, but I was curious to see how much was coming out). Then I checked the ohm internal resistance. Finally, the resistance was way to high and it was just a crap pack. Local hobby store replaced it for me and the replacement works perfectly. So yes, you probably have a "not so good" battery pack

 

[Boomer]

Ignoring the technical aspects to your question sightly, I also run the same ovonic batteries and im not impressed. They take less time to charge to get to 4.2v after a run compared to some Voltz 5000mah lipos I also run, and they have less runtime by a good 5+ minutes on full power runs/bashing. It's either that they sag more under load and therefore triggering lvc earlier, or their advertised mah isn't right - or probably a mixture of both.

You could only really test mah category if you fully discharge the battery down to 0%, which as other say, you never do (or would want to if you value your property!).

I don't think the it's necessarily a "bad brand" or even a "bad pack" but they are more of a budget range so generally speaking won't perform as well as others. Obviously that's not always the case as people have good results with Amazon specials (Zeees spring to mind). And the Sprektrum smart batteries are over priced based purely on amount of power/capacity delivered. But I wouldn't buy another ovonic again because performance is noticeably less.

 

[nino]

You could lower the LVC on your ESC (it you have that option), getting more runtime and mAh out of your packs, BUT at the expense of reducing their life.
I'm guessing you could get some 4000mAh out of them by cutting off at 3.2V.
3500 out of 5200 from 4.2V to 3.6V is not particularly good, but not terrible.