intersting way of charging

leebuki

leebuki

New Member
Can use a higher voltage battery pack to charge a lower one until the lower is full(carefully monitoring)? Let's say i have a 48v full(54.6v) battery pack and i want to charge a empty(30v) 36v pack. i connect them in parallel and monitor the voltage of the lower one until its almost full(41.0v to be safe). Shouldnt be much an issue unless i fall asleep lol right?

Just how high a voltage can i go to charge a battery? can i use 100v to charge 36v battery pack(monitoring closely of course).
can use 1000v? I already regularly use my 52v charger on my 48v battery for faster charging until near full.
 
hmmm.. i think its totally possible ive been testing it on 1s 1p packs connecting to 3s 2p 11.1v pack in parallel. you can just disconnect it when the smaller pack gets to 4.1vs and its fine
just dont leave it there. im wondering if i can connect a 36v pack to 1s 1p? lol how high can you go?
 
I had written a response based on electrical theory, but decided it was best to be crude. It's just dumb.

batman2.jpg
 
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well i got this from google. so i know it can be done safely..
"A battery can be charged safely at high voltages as long as the battery is not fully charged. These higher voltages allow the battery to be charged faster. But if you want to leave the battery on the charger to keep it topped off, a float voltage of 13.6V to 13.8V is usually used"

Keyword as long as its not fully charged.. My question only remains just how high and fast can you go? should i experiement on smaller scale like with just a single cell. until i see heat build up then stop?
 
Been trying different setups so far 0 heat from the cell being charged.. and it charges incredibly fast like within 3mins. Its really awesome
ive gotten more heat from the cells from running medium loads.. This a hidden secret?
 
Charging a 1S pack from a 3S is one thing. Please don't hook a fully charged 54.6V 13S outpit to a depleted 30V 10S output.

There's nothing to stop a huge influx of current. There's nothing to stop overvoltage either. You're only looking at the total series output of the 10 groups, but say you stopped at 42.0V, some groups could be above 4.2, and others below 4.0. Overcharge and overcurrent wreck your cells.

Connecting your 52V charger to a 48V pack is different too. The charger is putting out constant current, like 2-3 amps. The voltage will not rise past 54V till the very end. You're coming in thru the charger connection. There's an overvoltage circuit in there that keeps the cells from going over 4.2V, and when they get there, the BMS breaks the circuit. So your charger will say 58,6V, but the cells never see it, In fact, I have one 48V charger that is off, putting out 55.10 volts, but it could be used as long as the battery BMS is working,

I suppose you could put a higher voltage pack on the charge port of a battery, but you don't have the constant current charge. You probably will exceed the charge current rating for the cells.

Just trying to keep you from blowing up your batteries. You really can if you do this stuff. That's how they get some of those youtube battery explosions. They put 48V on a 4.2V cell.
 
I think this guy must be a troll. Can anyone believe he is serious. Maybe just unplug your dryer and hook it up to 240 volts, that will really light it up and charge it fast.
 
harryS said:
Charging a 1S pack from a 3S is one thing. Please don't hook a fully charged 54.6V 13S outpit to a depleted 30V 10S output.

There's nothing to stop a huge influx of current. There's nothing to stop overvoltage either. You're only looking at the total series output of the 10 groups, but say you stopped at 42.0V, some groups could be above 4.2, and others below 4.0. Overcharge and overcurrent wreck your cells.

Connecting your 52V charger to a 48V pack is different too. The charger is putting out constant current, like 2-3 amps. The voltage will not rise past 54V till the very end. You're coming in thru the charger connection. There's an overvoltage circuit in there that keeps the cells from going over 4.2V, and when they get there, the BMS breaks the circuit. So your charger will say 58,6V, but the cells never see it, In fact, I have one 48V charger that is off, putting out 55.10 volts, but it could be used as long as the battery BMS is working,

I suppose you could put a higher voltage pack on the charge port of a battery, but you don't have the constant current charge. You probably will exceed the charge current rating for the cells.

Just trying to keep you from blowing up your batteries. You really can if you do this stuff. That's how they get some of those youtube battery explosions. They put 48V on a 4.2V cell.
Click to expand...
i mean i understand what you're saying in theory but its not like lighting flammable gas and boom! There is progression of heat build up. Sure u cant safely connect it then leave. But IF you're there while its connected you can literally feel the battery for heat, If i t starts to get hot due to excessive current unplug and wait etc.. It doesnt take very long its like super fast to get the 36v pack from 0 to like 70%, maybe 3mins or so.. of course if you connected let's say a 72v pack maybe it'd take 2mins etc.. im not sure where the limit is as the the batteries have not risen a single degree so far..
 
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There is no way to limit the current flow when connecting batteries with different voltages. At the very least, you will likely damage the BMS in one or both batteries. If the batteries are fused, they will likely blow as well. If the current rating of the battery contacts is exceeded, heat will be generated and, as others have said, a fire could result.

Bad idea!
 
This is about the same thing. "Jump starting" a battery.

endless-sphere.com

jump starting caveat - Warning!

Jump starting dead 60v lithium ion batteries. Caveat. Please note. I just want to put out a warning for anyone trying to do a 'jump-start' trick to revive a dead lithium ion battery. I just tried out that technique to try on my 60v 4ah Greenworks battery. Although it seemed to be relatively...
endless-sphere.com endless-sphere.com
 
harryS said:
This is about the same thing. "Jump starting" a battery.

endless-sphere.com

jump starting caveat - Warning!

Jump starting dead 60v lithium ion batteries. Caveat. Please note. I just want to put out a warning for anyone trying to do a 'jump-start' trick to revive a dead lithium ion battery. I just tried out that technique to try on my 60v 4ah Greenworks battery. Although it seemed to be relatively...
endless-sphere.com endless-sphere.com
Click to expand...
similiar except using different voltage batteries, and the question remains just how high can you go? But i guess a full 12v battery has a voltage difference when jump starting a dead one. so yea same thing
 
leebuki said:
similiar except using different voltage batteries, and the question remains just how high can you go? But i guess a full 12v battery has a voltage difference when jump starting a dead one. so yea same thing
Click to expand...
Apples to oranges, if you had a voltage reducer you could probably do this, why would you even want to do this? These Li-Ion batteries can dump power so fast, Pb-H2 SO4 batteries are an entirely different beast, check out some of the videos of bike batteries cooking off.
 
6zfshdb said:
There is no way to limit the current flow when connecting batteries with different voltages. At the very least, you will likely damage the BMS in one or both batteries. If the batteries are fused, they will likely blow as well. If the current rating of the battery contacts is exceeded, heat will be generated and, as others have said, a fire could result.

Bad idea!
Click to expand...
PWM Charging???
I realize this is an old thread, but I found it interesting. IF the primary issue is current-induced heating, it's possible you could get around some of the "over-current" problems by using a variable PWM setup. The frequency and duty-cycle of the DC pulse charging voltage would vary depending on a given battery pack's state and of course electrical parms. Some experimentation would have to be used to find the set points where nothing catastrophically heats up, nor does one exceed spec'd voltage limits of devices like MOSFETs in a BMS and so on. Using PWM one could find waveform parameters that while a current limit may be exceeded for a brief time, the short duration of a given pulse will over time not cause any heating. Appropriately short pulses could also prevent fuses (link or solid-state) from triggering or being damaged. As the lower potential battery pack nears a charged state, I'm thinking the duty-cycle of the pulse may need to be significantly reduced even though the voltage of the higher potential pack may remain near its original value.
 
jGecko said:
PWM Charging???
I realize this is an old thread, but I found it interesting. IF the primary issue is current-induced heating, it's possible you could get around some of the "over-current" problems by using a variable PWM setup. The frequency and duty-cycle of the DC pulse charging voltage would vary depending on a given battery pack's state and of course electrical parms. Some experimentation would have to be used to find the set points where nothing catastrophically heats up, nor does one exceed spec'd voltage limits of devices like MOSFETs in a BMS and so on. Using PWM one could find waveform parameters that while a current limit may be exceeded for a brief time, the short duration of a given pulse will over time not cause any heating. Appropriately short pulses could also prevent fuses (link or solid-state) from triggering or being damaged. As the lower potential battery pack nears a charged state, I'm thinking the duty-cycle of the pulse may need to be significantly reduced even though the voltage of the higher potential pack may remain near its original value.
Click to expand...
Or you could use a proper charger and stop trying to reinvent a totally unnecessary third wheel.
 
All chargers charge at higher voltage, measure the output from the charger, it should be around 54 volts for a 48v battery, if you connect it to your discharged battery at say 49 volts, the output will drop to the battery voltage.

Chargers are current limited, but enough amperage hypothetically would bring the battery up straight away, but obviously destroy it in the process.
 
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