Battery does not retain charge, help please!

[triplesilk]

Hi, I wonder if someone can help me. I have a hooverboard (from China) and it's always worked perfectly, though we've not used it much. However, I have encountered a problem.....

• the battery does not retain a charge,
• the first thing I noticed was that after charging the battery only lasted a very short time (now I think that there was no charge applied and the battery was just depleting more each time);
• if I plug in the charger, I get the correct flashing amber light (at least I think it's correct);
• but no charge is retained;
• now, if I unplug the charger the hoverboard won't turn on (so that the battery is pretty much empty).

I have tried a new charger (which I didn't mind buying as the charger I had didn't have a fused plug), but this has the same effect. There is only one way to plug in the charging cable, so I don't think that is the issue. I have taken the two plastic covers off and nothing obvious is wrong (no cables are loose and all connectors look OK). 

It seems to be that either the battery has just broken, or that there is something wrong with the charging mechanism (does the charging light mean anything here?). Anyway, some pointers as to what I should check for would be appreciated. 

[Keith]

We get around a post a week just like this and it sits here with no replies for the simple reason that if you don't have the slightest idea what board you have got or what the correct charging conditions are then neither do we. They are all different, mine has a red charging light that goes green on completion for example.

I assume that you have some idea what voltage it is or you couldn't have purchased another charger? Or, in fact could the charger be incorrect?

If one assumes that at least one charger is OK (a big if) then it is very very unusual for batteries to fail to take charge suddenly. Most likely scenario would be that the charge connector has become disconnected within the wheel.

Assuming (a very big assumption!) that your board is quoted as 36 or 37 volts and uses 18650 lithium Ion cells then fully charged voltage would be 42 volts and it will stop working at between 30 and 34 volts. Two of the pins on the charging socket should, therefore, measure, with a voltmeter somewhere between 30 and 42 volts, any other pins are probably disconnected. If they don't read anything then the lead has become disconnected. YOU NEED TO BE VERY VERY CAREFUL IF YOU ATTEMPT TO MEAUSURE THE VOLTAGE if you accidentally short the positive and negative together arc welding levels of current will flow and do considerable damage possibly to you as well as the meter and board.

Edited March 13, 2016 by Keith

[triplesilk]

Thanks....I was fairly sure that the charger was OK but I could be wrong. Both the old and new chargers state that the output is 42 volts (it's a 3A plug so should be plenty).

I've had a good look inside and all connectors look OK but I may be missing something :-(

In terms of lights, green = good, red = battery low, orange = charging. But, the manual was pretty useless and in Chinese. As far as lights go, nothing is out of line, it's just that the battery can't get charged. It's fairly easy to get the battery out, so I was wondering if I could try to charge some other way (just as a test) but I'm guessing that's probably quite tricky?

 

 

[esaj]

3 minutes ago, triplesilk said:

It's fairly easy to get the battery out, so I was wondering if I could try to charge some other way (just as a test) but I'm guessing that's probably quite tricky?

Yes, it's a bit tricky (you need to control the voltage & current), and can be downright dangerous if you don't know what you're doing. Remember all the house fires caused by hoverboards? Usually it's been either one or a combination of broken/faulty charger, broken/faulty BMS (Battery Management System, it's a circuit board inside the battery pack) and/or low quality battery cells...

Edited March 13, 2016 by esaj

[Vivianjiangster]

Have you tried to replace the battery and test it again? I think it is probably the problem of battery. In our experience, most of no charge are caused by the motherboard. It is very rare that the battery is broken. But your problem seems different, it can be turned on at the beginning. 

You can call our engineer to consult your problem. We repair a lot of hoverboards from different Chinese factories. 

https://www.landbirdboard.com/pages/hoverboard-repair-center 

Hoverboard Repair Service Center:

3731 B San Gabriel River Pkwy
Pico Rivera, CA 90660

Hot line: 1-818-3578677

 

 

Edited March 14, 2016 by Vivianjiangster

[Vivianjiangster]

You can check this article about how to change the hoverboard battery. 

https://www.landbirdboard.com/blogs/news/83394502-how-to-change-your-hoverboard-battery

[triplesilk]

Thanks, the thing is I'm in the UK and the delivery costs + repair costs would barely make it worth it. I'm just wondering whether it's worth buying a new battery. I've already taken my one out and put it back, and it's very simple to do. 

Another option may be to buy something that allows me to test the battery? I don't mind spending a few quid on something that I may be able to use for other things over the years. 

[triplesilk]

Just looking at Google, digital multimeters are pretty cheap and look like useful tools. I was thinking that I can get one, take the hoverboard battery out, and stick the two probes of the multimeter in the two battery connector slots (of the yellow connector) and I should get some kind of measurement. Can anyone let me know if this should work and give useful info about the battery?

[dmethvin]

Yes, that should give you some useful data. An inexpensive multimeter is probably about $10 and will give you the voltage reading. It really sounds like the charger voltage isn't making it to the battery, but I am not familiar with those chargers and don't know what a flashing amber light means.

[esaj]

54 minutes ago, triplesilk said:

Just looking at Google, digital multimeters are pretty cheap and look like useful tools. I was thinking that I can get one, take the hoverboard battery out, and stick the two probes of the multimeter in the two battery connector slots (of the yellow connector) and I should get some kind of measurement. Can anyone let me know if this should work and give useful info about the battery?

Yes, you can measure the voltage of the pack, but make sure to set the probes right (ie. not in the current-measuring holes!), otherwise you'll end up short circuiting the pack over the meter, and can get pretty nice fireworks (I did ):

Luckily I just ended up with a molten probe-tip (and a destroyed battery connector).

 

Someone else did the same mistake:

[triplesilk]

Oh blimey, that looks like a scary moment there!

I may be being dumb here, but you have two probes and two holes in the battery connector. Was that issue the probes being in the incorrect way around, or the settings of the multimeter not being correct?

I have a fair suspicion that the battery has nothing in it, but you never know. Even if it is dead I guess I won't know whether it's just a faulty battery or whether there is something wrong with the charging part. All I can really see is that the wires and connectors look fine. 

[triplesilk]

1 hour ago, dmethvin said:

Yes, that should give you some useful data. An inexpensive multimeter is probably about $10 and will give you the voltage reading. It really sounds like the charger voltage isn't making it to the battery, but I am not familiar with those chargers and don't know what a flashing amber light means.

Honestly, all I have is battery info and all sorts of import stuff about that. No manual or anything, but I'm pretty sure that flashing amber or orange is normal for charging when the thing is on for this model. It does sound like the charge is not getting through as you say, and I'm at a loss as to what to do about it ;-(

[esaj]

40 minutes ago, triplesilk said:

Oh blimey, that looks like a scary moment there!

Yeah, I did jump up a bit on my chair when I heard the "ZZZZT!" and saw sparks flying...   Funny now, but not then.

 

Quote

I may be being dumb here, but you have two probes and two holes in the battery connector. Was that issue the probes being in the incorrect way around, or the settings of the multimeter not being correct?

The probes were incorrectly set in the multimeter, as I had earlier been measuring currents (amperes), and was meant to measure the voltage of the battery pack. I did flick the rotary switch of the meter to the voltage-area, but hadn't changed the probe connections:

 

See the four holes in bottom of the meter (in some there might only be three). COM is common ground, that's where the lead of the black probe is always plugged (actually, you could just as well use the red lead there, but it's easier to remember the polarities by always keeping the black in the COM-hole and just switching the red lead to other holes). When measuring voltages, you use the COM and the one on right that's marked as V (and an ohm-sign, meaning it's also used to measure resistance). The markings may be a bit different, depending what the meter can measure (at least V as in Volts should be there). The other two on the left are for two different amperage measuring ranges, A = "full" amps, up to usually 10-20A, the other one mA/µA is micro amps and usually can withstand about 400-500mA. When measuring voltages, make sure to plug the red lead into the correct hole before poking anywhere with the probes

 

Quote

I have a fair suspicion that the battery has nothing in it, but you never know. Even if it is dead I guess I won't know whether it's just a faulty battery or whether there is something wrong with the charging part. All I can really see is that the wires and connectors look fine. 

After making sure you got the probes set up correctly and have selected a large enough setting for the DC (Direct Current) voltage (200V typically). If there's no text "DC" in the voltage-settings, the "squiggly" line is AC (Alternating Current) and the one with a straight line and dotted line below it is DC. Then you put the probes into the battery connector (do not let the metal parts of the probes touch each other while they're connected to the battery!) and read the voltage value.

As your pack says 4.4Ah / 40V (that's usually the nominal voltage), I'm suspecting that it is 11S2P pack (11 cells in series, 2 in parallel). It could also be rounded value, and it could be a 10S (10 in series) pack. Any way, depending how full/empty the pack is, the voltage should be roughly between about minimum of 30...34V to 42..46V for it to be within the normal range.

Another thing you should check is how much voltage your charger is putting out. If the pack is 10S, you should get a voltage reading of 42.0V (might be slightly higher, if there's a reverse protection diode in the battery pack BMS, and they want to cancel the voltage drop caused by it, 42.6V or so?). If it's 11S, you should get about 46.2V (again, if there's that diode, it could be something like 46.8V or so). If the voltage is clearly below either of these (well, if it's between 42.6 and 46.2V, then there's more guessing to do about the amount of cells in your pack), your charger isn't putting out enough voltage and cannot fully charge the packs.

Hope I didn't forgot anything important...

EDIT: Oh right, if you see negative values when measuring voltage, it just means that the connector holes you've plugged the probes into are the other way around (you have your ground-probe in the positive terminal, and positive probe in the negative terminal). There's nothing dangerous in that, it just shows a negative voltage then.

Edited March 14, 2016 by esaj

[triplesilk]

Wow, thanks for all the help. I'll have to get one of those meters, do some reading (sort of general self-improvement), and then re-read that and hopefully it will make perfect sense to me ;-)

I did just come back to post a mini brain wave I just had, but I think you are suggesting the same thing - ie test the other end of the charging cable (the other side of the yellow connector) as well. I'd be a bit nervous to test anything with the socket on, but if I'm confident by then of how the things work and I wear goggles and gloves then it should be fairly unlikely that something awful would happen?

I just wish I did more of this stuff in school, or if it was covered I wish I concentrated more!

[esaj]

5 minutes ago, triplesilk said:

Wow, thanks for all the help. I'll have to get one of those meters, do some reading (sort of general self-improvement), and then re-read that and hopefully it will make perfect sense to me ;-)

I did just come back to post a mini brain wave I just had, but I think you are suggesting the same thing - ie test the other end of the charging cable (the other side of the yellow connector) as well. I'd be a bit nervous to test anything with the socket on, but if I'm confident by then of how the things work and I wear goggles and gloves then it should be fairly unlikely that something awful would happen?

I just wish I did more of this stuff in school, or if it was covered I wish I concentrated more!

As long as you don't let the metal tips of the probes touch each other while they're touching the metal inside the battery connectors, you should be fine. Also don't put your fingers on the exposed metal parts (hold the probes from the plastic-part), so you don't make yourself a part of the circuit . When the probes are set up for voltage measurement, there's a very large resistance inside the multimeter, so it won't allow large current to flow.

On the other hand, when the probes are set for measuring currents, there's a very LOW resistance inside the meter (so it wouldn't affect the measurement, at least much), and that's when the meter acts like a short circuit.

You can find tons of articles and videos with Google about using a multimeter simply by searching for something like "using multimeter", "multimeter tutorial", "multimeter measurement" etc.

[triplesilk]

Right, I've had a go - I wonder if anyone can help me make sense of this lot.

I took the battery out and tested using a multimeter. I assume this is DC - it gives a reading of 17.6V (which seems very low). The AC reading is 23.9V but I assume that this is meaningless? I've attached the 17.6V reading pic, and also a page from the stuff that came with the hoverboard that has battery info.

In terms of the input, I didn't plug in some of the connectors that I had to take out to remove the battery when testing this. A picture is attached that shows how I tested the readings from the yellow connector that attaches to the battery. 

For a DC reading I seem to get 41.8V, no matter whether the power is on and the charged plugged in.

For AC, I get 91.8V when the power is on. With the power off it drops slowly (I think it gets down to about 78V or thereabouts eventually).

If anyone can make sense of this lot it would be great! 

Edited March 16, 2016 by triplesilk

[dmethvin]

1 hour ago, triplesilk said:

I took the battery out and tested using a multimeter. I assume this is DC - it gives a reading of 17.6V (which seems very low). I've attached the 17.6V reading pic, and also a page from the stuff that came with the hoverboard that has battery info.

For a DC reading [from the charger] I seem to get 41.8V, no matter whether the power is on and the charged plugged in.

Definitely use the DC voltages. From the fact that the charger seems to be putting out 41.8v it sounds like the charger is probably okay.

The 17v reading for the battery does not sound good, however. If that is a 10-cell pack then the max voltage should be about 42v (which the charger is providing) and the minimum should be about 28v at absolute minimum. Something has most likely failed in the battery pack or the BMS. The next step might be to remove the shrink and test the individual cells to see if perhaps one is dead and could be replaced?

[triplesilk]

Thanks, that might be a good idea. One thing that I thought was odd was that the battery didn't just stop - I got a low battery flashing light, so charged and the battery ran for a few seconds, then I charged again and eventually the hoverboard won't turn on. This seems just like the battery running down as it should, without any charge getting in when I tried to charge. Does that fit in with what you are saying?

[esaj]

I'm just a hobbyist/amateur, so don't take the following as an expert opinion   But here goes...

Nevermind the AC-readings, you're dealing with DC here. It sounds like the AC-mode could be assuming the value is an RMS-value, and multiplying it by 1 / sqrt(2) (as 17.6V * 1/sqrt(2) = 24.89V). Although it doesn't explain the 91V value from the charger(?), maybe there's some higher voltage transients it's picking up or something..?

Anyway, the battery papers show that it's a 10S pack (10 cells in series, 36V nominal voltage), and unfortunately, also very crappy cells used, if the 2200mA = 2.2A max discharge current is correct (typically at least with electric unicycles, you should something like 10A cells to be on the safe side, preferably multiple packs in parallel). Likely even a hoverboard can pull very large currents from the pack during riding, so that could be also the reason why the pack has gone bad, but I'm only guessing. Under "Use" it lists only "digital products", which is very different (low amperage) usage than driving motors with heavy load to move around.

The cut-off voltage is listed as 3.0V (per cell), so the cells are probably already toast (the voltage of the pack should not go below 10 * 3.0V = 30V except for brief periods), and apparently it's already at around 1.76V per cell. Can't tell whether there's a BMS or not, which could be preventing it from taking charge. The fact that it doesn't accept charge, is actually a good thing here: It is said that metal shunts start to form inside the cells if they've left lingering below something like 2.0V (if I recall correctly) for longer periods, and the cells can then get internally short-circuited, possibly causing a fire if charging is attempted. I don't know if this is common, but personally wouldn't take the risk, and instead take the pack into recycling & get a new one (preferably with much higher quality cells).

The charger voltage sounds okay, it's near enough the full 4.2V / cell -value (which would be exactly 42V for 10S-pack).

If you choose to dismantle the pack, be careful, as the cells still aren't completely dead (ie. don't short circuit them etc). Lithium-fire is very hard to distinguish (apparently the reaction itself keeps releasing oxygen, so you cannot suffocate it), and the smoke can be toxic.

[triplesilk]

Thanks a lot Esaj, new batteries are expensive but if that's what it takes then there is no other option, I just didn't want to buy one and have the same problem once it needed charging. Given the battery seems to be dead, I may cut the plastic off and just test what I can as dmethvin suggests given that I'm keen to play around with the multi-meter ;-)

Two things confuse me a bit, but both are probably me being dumb .. but:

• given that the power source is AC I wasn't sure what would be feeding into the battery. I think you are saying that it gets converted by the time it gets there to DC?
• I kind of thought I'd have no voltage reading from the input to the battery with the charger not plugged in. I guess this is the result of some energy stored in a capacitor or something like that?

 

[triplesilk]

Actually, when I take off the layers of plastic and paper it looks like below. Not sure where to stick what to be honest so the next issue is what replacement battery to get!

[esaj]

27 minutes ago, triplesilk said:

Thanks a lot Esaj, new batteries are expensive but if that's what it takes then there is no other option, I just didn't want to buy one and have the same problem once it needed charging. Given the battery seems to be dead, I may cut the plastic off and just test what I can as dmethvin suggests given that I'm keen to play around with the multi-meter ;-)

Sure, just be careful. The most common mistake is probably accidentally shorting the cells... As there's still voltage in those cells (although below the minimum recommended voltages for normal usage), they can likely still give out some high currents, at least for a little while.

Quote

Two things confuse me a bit, but both are probably me being dumb .. but:

• given that the power source is AC I wasn't sure what would be feeding into the battery. I think you are saying that it gets converted by the time it gets there to DC?

The charger itself is an AC/DC-transformer (among other things, likely it's some form of switching power supply with constant current / constant voltage -modes, but that goes beyond my understanding of electronics), you should never connect a battery pack to an AC-voltage.

 

Quote

• I kind of thought I'd have no voltage reading from the input to the battery with the charger not plugged in. I guess this is the result of some energy stored in a capacitor or something like that?

Was the charger still connected to the charging port (but removed from wall outlet)? At least the charger should contain (fairly large) filtering capacitors, so that would explain it. In electric unicycles, the charge port usually connects directly to the battery pack-charging side. But your pack looks like there's no separate charging/discharging wires (ie. there aren't two sets of red and black wires), so it could be that the charging runs through some other board that can also contain capacitors that have still voltage.

 

8 minutes ago, triplesilk said:

Actually, when I take off the layers of plastic and paper it looks like below. Not sure where to stick what to be honest so the next issue is what replacement battery to get!

If you want to measure the voltage of a single cell, you should (try) to get your probes at both ends of a single cell (those green metal cylinders). That's also exactly the point where you could accidentally cause an unintended short-circuit, if you can't inspect how the cells are connected to each other...

That's a 10S2P (10 in series, 2 in parallel) -pack, so there are two sets of 10 cells each, which are paralleled (probably as pairs of cells for balancing). The "thick" metallic looking plate is likely the heatsink for the BMS (hard to say from the picture), and the BMS board itself sits below it. The thinner white wires are for balancing the cells (so it charges each cell to same voltage) and should run into the BMS.

Edited March 16, 2016 by esaj

[Chriull]

1 hour ago, esaj said:

Nevermind the AC-readings, you're dealing with DC here. It sounds like the AC-mode could be assuming the value is an RMS-value, and multiplying it by 1 / sqrt(2) (as 17.6V * 1/sqrt(2) = 24.89V). Although it doesn't explain the 91V value from the charger(?), maybe there's some higher voltage transients it's picking up or something..?

The RMS should be 1/sqrt(2) from the peak value - so if the multimeter "rectifies" the DC Voltage and beliefs that this is the peak voltage it should be 17,6/1,4=.... as result.

Could have been that the strange reading comes from an inverse polarity diode (which is blocking while measuring) so one get an "undefined" Voltage divider while measuring... So depending in the different inner resistance of the volt meter in DC and AC mode one gets different results.

On the other side the measurement of the charger is still more way off, so the above idea does not work at all there.... ;(

But in both cases the motherboard was (could have been) attached - so maybe this makes something very very strange...?

 

32 minutes ago, triplesilk said:

Actually, when I take off the layers of plastic and paper it looks like below. Not sure where to stick what to be honest so the next issue is what replacement battery to get!

But since you have your battery already open and disconnected from the motherboard and the charging "line" you could measure again the voltage - are there still only 17,6V and the strange AC readings?

Do you have "input" and "output" lines from the BMS/battery. The "output" lines should be two thicker red/black cables to the controlboard, the input lines are red/black too (could be a bit thinner) and should go to the charger plug (maybe via the controll board, too). If you have just one red/black connection (a combined BMS) my theory with the inverse polarity diode is definitely obsolete and the batteries are dead.

To measure the voltage of the different cells one by one you can also follow the thinner white cables - maybe you find a nice and safe spot for measurement where the white cables come to the BMS? (they are exactly for the measurement of the single cells by the BMS itself, so it can(could/should) shutoff in case of low voltage...)

 

[esaj]

3 minutes ago, Chriull said:

The RMS should be 1/sqrt(2) from the peak value - so if the multimeter "rectifies" the DC Voltage and beliefs that this is the peak voltage it should be 17,6/1,4=.... as result.

Could have been that the strange reading comes from an inverse polarity diode (which is blocking while measuring) so one get an "undefined" Voltage divider while measuring... So depending in the different inner resistance of the volt meter in DC and AC mode one gets different results.

On the other side the measurement of the charger is still more way off, so the above idea does not work at all there.... ;(

But in both cases the motherboard was (could have been) attached - so maybe this makes something very very strange...?

I was thinking more along the lines that the meter "sees" the RMS-value and tries to display the peak-value. But I'm not sure, never needed to do AC-measurements really    Well, maybe a long, long time ago in school. 

 

3 minutes ago, Chriull said:

But since you have your battery already open and disconnected from the motherboard and the charging "line" you could measure again the voltage - are there still only 17,6V and the strange AC readings?

Do you have "input" and "output" lines from the BMS/battery. The "output" lines should be two thicker red/black cables to the controlboard, the input lines are red/black too (could be a bit thinner) and should go to the charger plug (maybe via the controll board, too). If you have just one red/black connection (a combined BMS) my theory with the inverse polarity diode is definitely obsolete and the batteries are dead.

To measure the voltage of the different cells one by one you can also follow the thinner white cables - maybe you find a nice and safe spot for measurement where the white cables come to the BMS? (they are exactly for the measurement of the single cells by the BMS itself, so it can(could/should) shutoff in case of low voltage...)

Good idea on using the balance cables for measuring. I think (based on the earlier images) that the pack only has single set of wires, so apparently charge and discharge occur over the same wires?

[triplesilk]

Wow, I did spend a bit of timing learning about this stuff but this is way above my head ;-) I need to get more up to speed on this stuff.

Just to confirm, there is only one connection to and from the battery - a yellow connector with thick red and black cables either side. The charging cable going into the motherboard (or whatever it's supposed to be called) and not straight into the battery.

Just checked the battery again using the red and black cables again and I get 17.5V DC and 23.9 AC.

I just tried to test a block of 4 cells - these sort of flop out so I can get to it. Using the metal bits by the white cables I get 3.4V. I guess that is about 20% of the overall reading for 20% of the cells.