Author Topic: Li-Ion battery help  (Read 3501 times)
xelareverse
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Li-Ion battery help « on: February 14, 2016, 12:55:53 PM » Author: xelareverse
So my hoverboard charger broke. It says 42 volts but only lets out 30. The battery is 36v and I think I should use a 42v charger. Aren't Li-ion batteries supposed to to charge at a slightly higher voltage than their own?
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wattMaster
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Re: Li-Ion battery help « Reply #1 on: February 14, 2016, 02:24:43 PM » Author: wattMaster
So my hoverboard charger broke. It says 42 volts but only lets out 30. The battery is 36v and I think I should use a 42v charger. Aren't Li-ion batteries supposed to to charge at a slightly higher voltage than their own?
Yes, they are supposed to. Possibly a faulty charger or your volt meter?
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xelareverse
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Re: Li-Ion battery help « Reply #2 on: February 14, 2016, 05:40:52 PM » Author: xelareverse
So my hoverboard charger broke. It says 42 volts but only lets out 30. The battery is 36v and I think I should use a 42v charger. Aren't Li-ion batteries supposed to to charge at a slightly higher voltage than their own?
Yes, they are supposed to. Possibly a faulty charger or your volt meter?

I tried different volt meters and they all said the same. So a 42v carger will be perfect for the battery?
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Re: Li-Ion battery help « Reply #3 on: February 14, 2016, 05:59:07 PM » Author: Ash
For one, any "charger" is actually 2 circuits :

 - Power supply, that puts out some approximate voltage, higher than the battery full charge voltage

 - Charge control, that really controls what goes in the battery, how fast, and when to stop

Li Ion batteries DEFINITELY need a charge control - Connecting them directly to a power supply, with output voltage high enough to overcharge them, will lead to overcharge and that often ends in an exploding battery. (NiMH, NiCd and Lead Acid are nowhere near as volatile on overcharging - they heat up and degrade but thats about it)

The "charger" may be only the power supply (so the charge control is actually in the hoverboard itself), or it may be the power supply and charge control (so in the hoverboard the connector goes straight to the battery). If you want to think of replacement, make sure what you got there

The fault is likely something small like a bad capacitor (esp the SMPS chip's supply voltage one) or bad soldering joing, give a try to repair it before you replace
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Re: Li-Ion battery help « Reply #4 on: February 14, 2016, 07:18:59 PM » Author: xelareverse
For one, any "charger" is actually 2 circuits :

 - Power supply, that puts out some approximate voltage, higher than the battery full charge voltage

 - Charge control, that really controls what goes in the battery, how fast, and when to stop

Li Ion batteries DEFINITELY need a charge control - Connecting them directly to a power supply, with output voltage high enough to overcharge them, will lead to overcharge and that often ends in an exploding battery. (NiMH, NiCd and Lead Acid are nowhere near as volatile on overcharging - they heat up and degrade but thats about it)

The "charger" may be only the power supply (so the charge control is actually in the hoverboard itself), or it may be the power supply and charge control (so in the hoverboard the connector goes straight to the battery). If you want to think of replacement, make sure what you got there

The fault is likely something small like a bad capacitor (esp the SMPS chip's supply voltage one) or bad soldering joing, give a try to repair it before you replace

 It has overcharge protection. So should I use a 42v charger?
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Re: Li-Ion battery help « Reply #5 on: February 14, 2016, 09:16:56 PM » Author: RCM442
Don't quote me on this, but I don't think the hoverboard batteries have charge protection, so please be careful!
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Re: Li-Ion battery help « Reply #6 on: February 14, 2016, 10:35:14 PM » Author: xelareverse
Don't quote me on this, but I don't think the hoverboard batteries have charge protection, so please be careful!
The do, I took a dead one apart.
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Re: Li-Ion battery help « Reply #7 on: February 14, 2016, 11:29:16 PM » Author: Ash
Batteries do not have overcharge protection. The protection is either in the outside "charger" (if the port on the board goes straight to batery terminals) or in the hoverboard

What i mean is, if you think the protection is in the hoverboard, then you connect from outside a 42v power supply, and comes out the protection had to be actually in it, you have connected it to charge without any protection - Bang

Besides, "42v" charger might well be actually a 3x12V Lead Acid charger, as used in some e-bikes. You definitelty cannot control a Li Ion charge with that. At most use it as a substitute power supply to feed the proper Li Ion charger off it, if the voltage is ok

Try to figure out whats goingon with your existing charger. Very likely a bad capacitor or something that you can repair
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Re: Li-Ion battery help « Reply #8 on: February 15, 2016, 12:44:24 AM » Author: xelareverse
Batteries do not have overcharge protection. The protection is either in the outside "charger" (if the port on the board goes straight to batery terminals) or in the hoverboard

What i mean is, if you think the protection is in the hoverboard, then you connect from outside a 42v power supply, and comes out the protection had to be actually in it, you have connected it to charge without any protection - Bang

Besides, "42v" charger might well be actually a 3x12V Lead Acid charger, as used in some e-bikes. You definitelty cannot control a Li Ion charge with that. At most use it as a substitute power supply to feed the proper Li Ion charger off it, if the voltage is ok

Try to figure out whats goingon with your existing charger. Very likely a bad capacitor or something that you can repair
I took the old regulator apart. It looks lie this
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Re: Li-Ion battery help « Reply #9 on: February 15, 2016, 12:45:57 AM » Author: xelareverse
It has protection I'll order one tommorow
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Re: Li-Ion battery help « Reply #10 on: February 15, 2016, 09:24:28 AM » Author: wattMaster
It has protection I'll order one tommorow
Maybe you are not letting your battery charge enough. Could you connect your ammeter to the charger and battery?(Don't stick it directly across the battery.)
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Re: Li-Ion battery help « Reply #11 on: February 15, 2016, 12:08:50 PM » Author: xelareverse
It has protection I'll order one tommorow
Maybe you are not letting your battery charge enough. Could you connect your ammeter to the charger and battery?(Don't stick it directly across the battery.)
It didnt charge after 8 hours. Avg time is 2 hours
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Re: Li-Ion battery help « Reply #12 on: February 15, 2016, 02:27:44 PM » Author: Medved
Because of the LiIon volatility when overcharged, the LiIon system actually needs at least two stage control: Charger controller AND an overcharge protection device, each should be completely independent on each other.
With batteries large than about 10Wh even 3'rd level (so 2'nd protection) is used, in a form of fuse with separate trigger wire (such fuse does not respiond only to overcurrent, but it blows even when the 3'rd wire is energized).
With batteries consiting of multiple sells in series the protection should monitor voltage across each cell separately and disconnect the battery, when even one single cell leaves the allowed range (2.5 till 4.3V for the Cobalt based LiIon cells).

Normally it should be just the main charger, what is controlling the charging. The protections are there to prevent the violent failure in case the charger fails. The protection circuits are definitely not supposed and should never ever intentionally be used to control the charging. At least their cut off voltage is too high, causing very fast cell degradation. And mainly there won't be anything left to prevent the dangerous overcharge when the protection fails.


For the charger: The LiIon cells need very precise voltage control when approaching end of charge. Although the charging sequence is practically the same as for lead acid (a current till reaching the "full charge" voltage, maintain that voltage till the current drops to an EndOfCharge level and then switch the regulated voltage down to the maintenance charge level), the required accuracy is about 4x stringent than e.g. lead acid of any type. So even when the nominal voltages could be about the same (for a 10cell Cobalt based LiIon vs 18cell lead acid), the tolerance of the Lead Acid charger (allowed voltage tolerances +/-5%) is insufficient for the LiIons (allowed less than +/-1%).

And for the defect:
Many chargers use just some "test" current/voltage to first check the presence of the battery and only when they detect it, they turn ON the charging. So to see just 36V when there is no (or deffective) battery connected could well be normal.
What may have happened is just the cells in the series pack becoming unevenly charged (one cell ends up with lower charge level than others). Normally the nonideal charge efficiency (they exhibit larger leakage when they are at higher voltage state) tends to maintain the charge level balanced among the cells, but when the cells start to degrade, this effect may become insufficient and when the imbalance exceeds some limit, one cell may prevent further charging and other further discharging (triggering the over/under-charge protection).
So in your case it could be just one of the cells in the battery reaches end of life.
Some chargers contain balancer circuit - a special circuit artificially discharging a cell, if it's voltage is higher than others, so slowing down it's charging. Such circuit helps to prevent the imbalance and may effectively increase the effective battery life, but with quality cells such life benefit becomes noticeable only when high charge/discharge currents are involved.

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Re: Li-Ion battery help « Reply #13 on: February 16, 2016, 10:23:51 PM » Author: themaritimegirl
So my hoverboard charger broke.

Wait, you still have that thing? Oh god.
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Re: Li-Ion battery help « Reply #14 on: February 17, 2016, 12:03:44 AM » Author: xelareverse
So my hoverboard charger broke.

Wait, you still have that thing? Oh god.

Yup
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