Hi, I have a toy like the Overmax X-Monster 3.0 RC car with an attached USB charger and two 850mAh 7.4V packages. After 2 or 3 charges, the batteries stopped charging. After connecting the package, the charger pulls between 1-2A and after about 2 minutes disconnects the current. I measured the...

Measure the voltage between pins 2 and 3. It should be the same as between 1 and 2 or very similar. 1-2 is the first cell, 2-3 the second, 1-3 full package voltage. Although, based on these measurements, it can be seen that one cell has dropped in each package. So, dispose of both packages and buy new ones. By the way, think about buying a new charger. The Chinese ones that are added to toy sets are just hopeless and can destroy packages sometimes. The question is still for you, did you not use the packets for too long until the voltage dropped below 2.5 V per cell? In this case, the package is also destroyed.

There is 0V between pins 2 and 3. Generally I didn't measure while playing, just the car didn't go any further. Is it possible to check the charger somehow if it is somehow screwed up and destroys the batteries? Maybe for an attempt to disassemble these two and put together good goals and check? edit: In package B between 2 and 3, however, there is 3.28V.

So it's all clear. Both packages are scrap. Don't use them any more. Take them to a collection point for accumulators and batteries and buy new ones. You can check the charger only by measuring the output voltages, but only the measurement while charging a working package will be correct.

I converted two packages into one and it works. We'll see how long.

Not really. The cells in the package should be selected in terms of the closest possible internal resistance and capacity. Connecting cells from two different packages with varying degrees of wear and unknown internal resistance is one of the worst ideas.

as I wrote at the beginning, both packages were the same and had the same production date. The packages were identical because they were delivered with the toy.

It does not matter. Even packages from the same production line may differ. That is why the selection of cells is carried out, or at least should (as in the case of better brands), selection of cells. Budget companies not only often skip this process, which translates into shorter package life, but it also happens that they buy cells rejected from production by other producers. The selected packages are compatible with each other - for one package. They have similar startup parameters and life cycle. The two different packages may already be significantly different. You can see from the measurements you have taken that each cell is different. Such a package does not come for long and will not be as efficient as the new package. It can also pose a risk of damaging one of the cells and destroying the packet - either during use or while charging.

Hi! Did you check this charger? I am not able to load it with brand new packages from the set. I can see that OVERMAX and WLtoy-e etc. use chargers with 5V input (USB) is probably a weak link of this system ... Have you tried charging these packages with a power supply with a balancer? You write that you connected to a balancer to measure voltages. I am tempted to charge it with the iMAX but, although the package seems to be typical (current connector and balancer plug) ... however, the operating philosophy is slightly different because the package is loaded through the ... balancer connector and the current connector - loads - is left free hence the fear that the pin layout is standard and will not damage the iMAX

Yes, I also checked the original charger. Unfortunately, it cannot be dismantled. It is able to charge, but there is a problem with it, specifically with the USB port. Something does not touch it, only when the entire charger is connected, it starts to work properly. If the charger socket and USB plug are perfectly aligned, it does not work properly. The charger has a charging balancer and that's the only way I charged. I do not understand what you want to do, charge via the current connector?

Thanks for the answer! However, I will give up this original charger. Even if it has a balancer, it cannot handle packets where one cell is clearly weaker She's not the only one with the rest, the same is true of a simple lipo7.4 charger / balancer from another toy. Fortunately, I have an imax and it will be safer / healthier to use it. In fact, I expressed myself imprecisely, with the current connector I named the plug, which I connect the package to the model (two-pin) When charging with imax, this is the main charging connector and the three-pin plug then goes to the balancer socket. We'll see if the packages get up, if not, I wonder if I can advertise them. The warranty conditions are at least conservative from the seller's point of view ...

Overmax X-Monster 3.0 RC Car - Packet Loading Issues, USB Charger & 850mAh 7.4V Batteries

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#1 17535283 03 Nov 2018 13:17

chab chab

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Post #1
17535283 03 Nov 2018 13:17

Hi,
I have a toy like the Overmax X-Monster 3.0 RC car with an attached USB charger and two 850mAh 7.4V packages.

After 2 or 3 charges, the batteries stopped charging. After connecting the package, the charger pulls between 1-2A and after about 2 minutes disconnects the current.
I measured the tensions on the balancer and the entire package:

There is no voltage anywhere close to 7.4V. Could two packages hit the trail?
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#2 17535422 03 Nov 2018 14:35

Madrik Madrik

VIP Meritorious for electroda.pl

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Post #2
17535422 03 Nov 2018 14:35

Measure the voltage between pins 2 and 3. It should be the same as between 1 and 2 or very similar. 1-2 is the first cell, 2-3 the second, 1-3 full package voltage.

Although, based on these measurements, it can be seen that one cell has dropped in each package.
So, dispose of both packages and buy new ones. By the way, think about buying a new charger. The Chinese ones that are added to toy sets are just hopeless and can destroy packages sometimes.

The question is still for you, did you not use the packets for too long until the voltage dropped below 2.5 V per cell? In this case, the package is also destroyed.
#3 17535711 03 Nov 2018 16:58

chab chab

Level 11

» | Topic author Helpful post? (0)

Post #3
17535711 03 Nov 2018 16:58

There is 0V between pins 2 and 3. Generally I didn't measure while playing, just the car didn't go any further.
Is it possible to check the charger somehow if it is somehow screwed up and destroys the batteries?
Maybe for an attempt to disassemble these two and put together good goals and check?

edit: In package "B" between 2 and 3, however, there is 3.28V.
#4 17536502 03 Nov 2018 23:05

Madrik Madrik

VIP Meritorious for electroda.pl

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Post #4
17536502 03 Nov 2018 23:05

So it's all clear. Both packages are scrap.
Don't use them any more. Take them to a collection point for accumulators and batteries and buy new ones.
You can check the charger only by measuring the output voltages, but only the measurement while charging a working package will be correct.
#5 17585380 25 Nov 2018 20:23

chab chab

Level 11

» | Topic author Helpful post? (+2)

Post #5
17585380 25 Nov 2018 20:23

I converted two packages into one and it works. We'll see how long.
#6 17585758 25 Nov 2018 22:27

Madrik Madrik

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Post #6
17585758 25 Nov 2018 22:27

Not really. The cells in the package should be selected in terms of the closest possible internal resistance and capacity.

Connecting cells from two different packages with varying degrees of wear and unknown internal resistance is one of the worst ideas.
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#7 17603289 03 Dec 2018 21:15

chab chab

Level 11

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Post #7
17603289 03 Dec 2018 21:15

as I wrote at the beginning, both packages were the same and had the same production date. The packages were identical because they were delivered with the toy.
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#8 17603636 03 Dec 2018 23:40

Madrik Madrik

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Post #8
17603636 03 Dec 2018 23:40

chab wrote:
as I wrote at the beginning, both packages were the same and had the same production date. The packages were identical because they were delivered with the toy.

It does not matter.
Even packages from the same production line may differ.
That is why the selection of cells is carried out, or at least should (as in the case of better brands), selection of cells. "Budget" companies not only often skip this process, which translates into shorter package life, but it also happens that they buy cells rejected from production by other producers.

The selected packages are compatible with each other - for one package. They have similar startup parameters and life cycle.
The two different packages may already be significantly different.

You can see from the measurements you have taken that each cell is different.
Such a package does not come for long and will not be as efficient as the new package.
It can also pose a risk of damaging one of the cells and destroying the packet - either during use or while charging.
#9 17665270 31 Dec 2018 09:27

marekcherubin marekcherubin

Level 12

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Post #9
17665270 31 Dec 2018 09:27

chab wrote:
RC Overmax X-Monster 3.0 car with included USB charger and two 850mAh 7.4V packages.

After 2 or 3 charges, the batteries stopped charging. After connecting the package, the charger pulls between 1-2A and after about 2 minutes disconnects the current.

Hi!
Did you check this "charger"?
I am not able to load it with "brand new" packages from the set.
I can see that OVERMAX and WLtoy-e etc. use chargers with 5V input (USB) is probably a "weak link" of this system ...

Have you tried charging these packages with a power supply with a balancer? You write that you connected to a balancer to measure voltages.
I am tempted to charge it with the iMAX
but, although the package seems to be typical ("current" connector and balancer plug) ...
however, the operating philosophy is slightly different because the package is loaded through the ... balancer connector and the current connector - loads - is left free
hence the fear that the pin layout is standard and will not damage the iMAX
#10 17665952 31 Dec 2018 14:01

chab chab

Level 11

» | Topic author Helpful post? (+1)

Post #10
17665952 31 Dec 2018 14:01

Yes, I also checked the original charger. Unfortunately, it cannot be dismantled.
It is able to charge, but there is a problem with it, specifically with the USB port. Something does not touch it, only when the entire charger is connected, it starts to work properly. If the charger socket and USB plug are perfectly aligned, it does not work properly.
The charger has a charging balancer and that's the only way I charged. I do not understand what you want to do, charge via the current connector?
#11 17666533 31 Dec 2018 17:40

marekcherubin marekcherubin

Level 12

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Post #11
17666533 31 Dec 2018 17:40

Thanks for the answer!
However, I will give up this "original" charger.
Even if it has a balancer, it cannot handle packets where one cell is clearly weaker
She's not the only one with the rest, the same is true of a simple lipo7.4 charger / balancer from another toy.
Fortunately, I have an imax and it will be safer / healthier to use it.

In fact, I expressed myself imprecisely,
with the "current" connector I named the plug, which I connect the package to the model (two-pin)
When charging with imax, this is the main charging connector and the three-pin plug then goes to the balancer socket.

We'll see if the packages "get up", if not, I wonder if I can advertise them.
The warranty conditions are at least "conservative" from the seller's point of view ...
#12 17680946 06 Jan 2019 19:11

Madrik Madrik

VIP Meritorious for electroda.pl

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Post #12
17680946 06 Jan 2019 19:11

They won't get up.

Lithium packets discharged below 2.5V per cell are essentially killed.
The seller will not accept the complaint. Charging the battery is the responsibility of the user and is the responsibility of the user. 95% of such complaints are rejected. If you want, try it.

Generally, you have to buy new packages and use only a good charger.
#13 18728977 30 May 2020 23:35

marek1185 marek1185

Level 9

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Post #13
18728977 30 May 2020 23:35

I had the same case and the batteries died very quickly. Maybe you know where to buy new or some cool replacements?
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#14 18729295 31 May 2020 10:01

1 PAWEL 1 PAWEL

Level 42

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Post #14
18729295 31 May 2020 10:01

Recommended for batteries - Buzzer Voltage Meter Alarm Lipo 1s - 8s.
#15 18735235 02 Jun 2020 22:09

marek1185 marek1185

Level 9

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Post #15
18735235 02 Jun 2020 22:09

Ok, I will keep in mind, however, where can I get such batteries for this car?
The official website is a swamp of zero response to an email
#16 18735586 03 Jun 2020 06:32

1 PAWEL 1 PAWEL

Level 42

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Post #16
18735586 03 Jun 2020 06:32

Link

https://rc.susco.pl/p/23/22358/850mah-7-4v-25c-2s-lipo-do-rodeo-110-z-21-akumulatory.html

https://pl.aliexpress.com/item/32722719958.ht...7_shopb766=887_shop_google=887_shop=google=88 743612850714 & crea = pl32722719958 & netw = u & device = c & albpg = 743612850714 & albpd = pl32722719958 & gclid = EAIaIQobChMI1fbNvObk6QIVwoayCh1DDAS7EAQYASABEgwcLed = awdcl_s

Enter the dimensions of the packages.
#17 18871739 15 Aug 2020 16:30

marek1185 marek1185

Level 9

» | Helpful post? (+1)

Post #17
18871739 15 Aug 2020 16:30

The price definitely suits me better with alli and I am finally starting to buy it because my son is asking when I will start it. Does it make sense to take two at once or is it better to try first? The size I think will be ok because the ori are 3cm x 5.5cm. Ori charger that could be for this link?
#18 19455303 28 May 2021 18:46

bolotrusz bolotrusz

Level 1

» | Helpful post? (0)

Post #18
19455303 28 May 2021 18:46

Hi!

Has anyone tried to use larger substitutes for this?
Exactly I mean BATTERY BATTERY WLTOYS 7.4V 2100mAh TAMIYA PLUG or BATTERY BATTERY WLTOYS 7.4V 2600mAh Mini TAMIYA.
Is it safe?
The car works for a short time on the original sets and I wonder if it makes sense to buy larger batteries.
I will be grateful for your response ;)

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Topic summary

✨ The discussion revolves around issues with the Overmax X-Monster 3.0 RC car's battery charging system, specifically concerning the 850mAh 7.4V lithium polymer (LiPo) batteries and the USB charger. Users report that after a few charges, the batteries fail to charge, with voltage measurements indicating significant cell degradation. Recommendations include disposing of the faulty batteries and acquiring new ones, as well as considering a more reliable charger, as the original charger is deemed inadequate. Some users attempted to combine cells from different packages, which raised concerns about compatibility and safety. Suggestions for replacement batteries and chargers were also provided, along with links to purchase options.
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FAQ

TL;DR: If a 2S Li‑Po drops below 2.5 V per cell, it's effectively dead—"Lithium packets discharged below 2.5V per cell are essentially killed." Replace the packs, test with a known‑good charger, and add a low‑voltage alarm. [Elektroda, Madrik, post #17680946]

Why it matters: This FAQ helps Overmax X‑Monster 3.0 owners fix no‑charge issues, avoid charger damage, and pick safe replacements.

Quick facts:

Original packs reported around 30×55 mm; verify tray clearance before buying substitutes. [Elektroda, marek1185, post #18871739]
Below 2.5 V per cell = scrap; do not attempt revival; recycle responsibly. [Elektroda, Madrik, post #17680946]
Typical Li‑Po charge rate is 0.5–1C; for 850 mAh set ~0.4–0.85 A. [Battery University, 2024]
Add a 1S–8S LiPo buzzer alarm to prevent over‑discharge during runs. [Elektroda, 1 PAWEL, post #18729295]
Do not mix cells from different packs; IR/capacity mismatches raise failure risk. [Elektroda, Madrik, post #17603636]

Quick Facts

Original packs reported around 30×55 mm; verify tray clearance before buying substitutes. [Elektroda, marek1185, post #18871739]
Below 2.5 V per cell = scrap; do not attempt revival; recycle responsibly. [Elektroda, Madrik, post #17680946]
Typical Li‑Po charge rate is 0.5–1C; for 850 mAh set ~0.4–0.85 A. [Battery University, 2024]
Add a 1S–8S LiPo buzzer alarm to prevent over‑discharge during runs. [Elektroda, 1 PAWEL, post #18729295]
Do not mix cells from different packs; IR/capacity mismatches raise failure risk. [Elektroda, Madrik, post #17603636]

How do I check a 2S Overmax pack through the balance plug?

Use a multimeter on the 3‑pin balance lead. 1–2 is cell one, 2–3 is cell two, 1–3 is full pack. Cell voltages 1–2 and 2–3 should be similar. How‑To: 1) Set meter to DC volts. 2) Probe 1–2, then 2–3, then 1–3. 3) If one cell reads far lower than the other, the pack is bad. [Elektroda, Madrik, post #17535422]

My USB charger pulls 1–2 A then stops after ~2 minutes—what’s happening?

That behavior points to a failed or imbalanced pack. The charger cuts off when it detects an unhealthy battery. Replace the packs and test the charger only with a known‑good battery while measuring output. "You can check the charger only by measuring output while charging a working package." [Elektroda, Madrik, post #17536502]

What does 0 V between pins 2 and 3 indicate?

It indicates the second cell has collapsed or disconnected. The pack is scrap and unsafe to use. Do not attempt to recharge it. Take dead packs to a proper battery collection point for disposal. [Elektroda, Madrik, post #17536502]

Can the stock USB charger damage Li‑Po batteries?

Yes. "The Chinese ones that are added to toy sets are just hopeless and can destroy packages sometimes." Consider upgrading to a quality balance charger to protect your packs. [Elektroda, Madrik, post #17535422]

How can I verify if my charger is faulty?

Measure its output while charging a known‑good battery. Voltage should be stable and appropriate for a 2S Li‑Po in balance mode. If it fluctuates or drops out with a good pack, replace the charger. [Elektroda, Madrik, post #17536502]

Is rebuilding one good pack from two bad packs safe?

No. "Connecting cells from two different packages with varying degrees of wear and unknown internal resistance is one of the worst ideas." Mismatched cells imbalance quickly and can fail under load or during charging. [Elektroda, Madrik, post #17585758]

How should I charge these with an iMAX B6 or similar?

Use the main two‑pin pack connector as the charging connection. Plug the 3‑pin balance lead into the charger’s balance socket. Charge in Li‑Po balance mode for a 2S pack, following the charger’s instructions. [Elektroda, marekcherubin, post #17666533]

What charge current should I set for the 850 mAh pack?

Use 0.5–1C on a balance charger. For 850 mAh that’s about 0.4–0.85 A. Lower currents are gentler on aging packs. Balance charging helps keep cells matched over time. [Battery University, 2024]

Where can I buy compatible replacement batteries?

Check RC retailers and marketplaces; examples were shared for 850 mAh 2S replacements. Match voltage, size, and connector. Always confirm dimensions before ordering. [Elektroda, 1 PAWEL, post #18735586]

What are the original battery dimensions for fitment?

Users reported original packs around 3 cm × 5.5 cm. Measure your battery bay and leave space for wires and padding. Avoid thickness increases that stress the shell. [Elektroda, marek1185, post #18871739]

Which plug type do I need—Tamiya or Mini Tamiya?

Some substitutes use Tamiya or Mini Tamiya connectors. Match whatever your car uses or employ a safe adapter with correct polarity. Inspect the stock plug before ordering. [Elektroda, bolotrusz, post #19455303]

Is upgrading to 2100–2600 mAh packs safe for this car?

Yes, if voltage (2S, 7.4 V) and connector match, and the pack fits. Higher capacity increases weight, affecting handling and stress. Use an appropriate balance charger, not the toy USB unit. "Same S‑count, matching connectors, and fit come first." [Oscar Liang, 2023]

Should I use a low‑voltage alarm to protect the packs?

Yes. A 1S–8S Li‑Po buzzer on the balance lead warns before over‑discharge. Stop driving when it alerts to preserve cell health and runtime. [Elektroda, 1 PAWEL, post #18729295]

Will warranty cover packs that discharged too low?

Unlikely. The expert notes "95% of such complaints are rejected." Charging and care are considered user responsibilities. Replace the packs and improve your charging routine. [Elektroda, Madrik, post #17680946]

How do I dispose of dead Li‑Po batteries safely?

Do not trash them. Take damaged or exhausted packs to a battery collection or recycling point. Keep terminals insulated during transport to prevent short circuits. [Elektroda, Madrik, post #17536502]

My charger’s USB socket works only when held just right—what should I do?

That indicates a mechanical or contact fault in the charger. Replace the charger rather than risk poor charging and further pack damage. Use a quality balance charger instead. [Elektroda, chab, post #17665952]

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