Burning smell from a power supply

[Dave424]

This is a 13.8v 20Amp power supply. I was using it to charge a few LiPo batteries for a RC car. I noticed there was a burnt smell coming out of the rear end. The fan was working fine, so I checked that. I did not overload it because this charger will do 4 batteries at 50watts each. So 200watt capability in total. The power supply is rated at 270 watts. At the time of this incident I was charging only 2 batteries.

On a side note, the fan was working at a very low speed. I don't know if this matters.

Turned it off, opened it up and used an infrared temp probe to see what was burning. It turns out the copper coiled up thing showed in the picture was at 250 F. What does that part do, is it supposed to get hot? Capacitors and other parts were around 110F. Any help would be appreciated. Thanks.

 

[JimPghPA]

The coil is the inductor for the switching power supply of the 13.8 V 20 A supply.

Some possible problems:

1)The fan must have a good un-obstructed air flow for both the air in and the air out of the unit. Resting it on a carpet might block air flow if one of those paths are on the bottom of the supply.

2)This is more likely to be the problem, the multi charger quattro 4X6 unit might have one or more switching power supplies in it. When you use the first switching supply (the 13.8 Volt 20 Amp power supply) to run a second switching power supply (the multi charger quattro) the second unit pulls power in very brief but very high currents. This totally over-whelms the ability of the first supply to regulate, and exceeds the 20 Amp ability of the first supply. If this is the problem you are having, it might be solved by connecting a 12 volt 8 ampere-hour or larger battery to the output of the first supply. This would supply the peak current required to the multi charger quattro and the first supply would keep the battery charged.

This is assuming that the first supply is good.

Another fix would be to put a very large capacitor like a 1 FD on the out-put of the 12 Volt 20 Amp supply. These type of capacitors are used for 12 volt vehicles stereos. These very large capacitors are very expensive. Then run the multi charger quattro from that capacitor. This would supply the very brief very large currents required to feed the multi charger quattro. Be very sure to observe polarity, and be very aware that you never want to short out such a large capacitor.

 

[Scienceman]

Why the [censored] did those pics go from left to right insted of up to down?

 

[af0h]

Originally Posted By: JimPghPA
2)This is more likely to be the problem, the multi charger quattro 4X6 unit might have one or more switching power supplies in it. When you use the first switching supply (the 13.8 Volt 20 Amp power supply) to run a second switching power supply (the multi charger quattro) the second unit pulls power in very brief but very high currents. This totally over-whelms the ability of the first supply to regulate, and exceeds the 20 Amp ability of the first supply. If this is the problem you are having, it might be solved by connecting a 12 volt 8 ampere-hour or larger battery to the output of the first supply. This would supply the peak current required to the multi charger quattro and the first supply would keep the battery charged.


Exactly what I was thinking.

Go out and find/purchase a SLA battery (SLA = Sealed Lead Acid) as they are obviously sealed so they won't leak and won't vent hydrogen so they are safe to use inside the house. Use it as a buffer between your supply and the RC pack charger - as explained above. The larger the better, i'd probably go with a 12-aH or larger, but that's up to you.

What would be better would be to do away with the Power Supply completely and run the RC Pack charger off of a 12v battery (larger is better) with an automatic charger hooked to it. No fuss, no mess, no hassle, always ready...

 

[JimPghPA]

It would be a good idea to put the 12 Volt sealed lead acid battery on the charger for several hours to be sure it is mostly charged before you connect the multi charger quattro to the battery. This way the 13.8 Volt 20 Amp supply will not be over-loaded by having to charge a discharged battery the same time it is running the multi charger quattro.

One advantage of getting a sealed lead acid battery is you can charge it from the 13.8 Volt supply and then use it outside of the house to run the multi charger quattro.

A 12 Ampere-hour would be a better battery than a 8 Ampere-hour.

If there is a Batteries-Plus store near you they would be the best place to get one, they sell many batteries and therefore it would be fresh, and not already aged by being on a shelf or a long time.

Sealed lead Acid batteries usually only have a two year life expectancy. If you store the battery in a cool environment (some place cold but not below freezing) you can get three or more years from it. If you do not use it for a while (like a month) put a charge on it. It will last longer if you keep it charged up, but don't leave it on charge all the time. You can damage it by over-charging it.