TOPIC:

My son's Porsche has a problem. After a few minutes of uses starts with hiccups.
The battery indicates having 7.4V so I think it is charged. ESC fail?

Too hot. That's the warm safety. You maybe have a too big motor pinion, or too long run or in high grass

I'll check, but it seems to me that it was too fast for overheating.

Have you got a custom motor? I has the same matter with a trinity 12x2 after 3min of a soft run, I burnt it. A factory fail.

What sort of battery is it? A fully charged 2S Lipo (nominally 7.4v) should be 8.4v, 7.2v Ni-Cd or NiMH around 9.3v fresh off a charger ...

If your battery is not fully charged for some reason (poor quality or failing battery, ditto the charger, or charging technique), as soon as current is drawn by the motor the voltage drops & your ESC cuts out, as it cuts out the current draw also cut off and the voltage rises, and so the cycle repeats a few times, by which time there's enough momentum that the initial draw is low enough that the voltage doesn't drop below the critical point & so you get continous motor power.

It's all original Tamiya equipment. The battery is 7.2v Ni-Cd ... 7.4v just charged, it's the battery. Thank you stingray-63 and Jonny Retro. (I do not understand much about batteries. When I was a kid, I used gasoline and nitromethane.)

7.4V sounds very much like one of the cells has failed: 7.4 / 5 = 1.48, very close to the 1.5V per cell I'd expect to see, fully charged.

I wouldn't bother with dismantling the pack & trying to replace it - not least because to get a matching cell you'd have to buy another Tamiya pack of the same vintage and capacity, chances are that will have been sitting in a cupboard somewhere for the last 30 years & also have problems. Plus, getting enough heat in to properly solder the joints without damaging cells is a bit of a problem.

Time to replace or upgrade I think - if you were in the UK I would recommend Vapextech (www.vapextech.c...4-8v-7-2v/ - best value would probably be a pair of the 3300mAH 7.2v stick packs), I would assume they supply overseas but the shipping, even to near EU will probably be prohibitive :(

That's an NiMH (Nickel Metal Hydride) battery though - I don't know what you have by way of charging equipment but older Ni-Cd chargers will not be suitable, especially for fast charging. I would recommend an IMAX B6 or similar other "4 button" charger (they might have different cases, but all have 4 buttons, a 2 line matrix display & very similar internal hardware & software. They charge a lot of different types of battery at verious rates & methods - fiddly to start with but you'll get the hang of it. You'll also need a 12v power supply.

I dopn't know if I'd recommend Lipo batteries for you at this point, they give and apparent power/speed increase around 30%, but do need much more careful handling, storage & charging. For RC use you really must use packs with a hard case - and even the "stick" packs that are supposed to be the same size are just different enough in terms of girth or length to cause problems with the close fit encountered in Tamiya chassis. The other issue is permanent damage if you run them below a certain voltage - Tamiya ESCs don't support voltage cutoff at a Lipo safe level, so at the very least you'll need plug in alarms.


LiFe (Lithium Ion) packs I wouldn't bother with - Tamiya adopted these AFTER Lipo was very obviously becoming the new gold standard - they may be safer, but are lower capacity & lower voltage, hence lower performance.

Jonny Retro UK shipping is not cheap but the price depends a lot on the seller. Vapextech does not have shipping prices for Portugal. Either way I will try a local seller.

My charger is a Turnigy Accucell 6. It does not have an automatic charging option for NI-Cd batteries so I messed up the setup configuration. I discharged the battery and charged with a normal 300mAh charger for 8 hours. The pack arrived at 8.12V and the car is driving normally.

Meantime a friend will lend me a more sophisticated charger, with an automatic charge / discharged option to test the pack.

For the use I give the cars the Lipo are not justified. I'm going to buy some NiMH packs. It seems to me to be the safest because most of the time it is my 10 years old son who drives the cars.

VCR wrote:

Jonny Retro UK shipping is not cheap but the price depends a lot on the seller. Vapextech does not have shipping prices for Portugal. Either way I will try a local seller.

My charger is a Turnigy Accucell 6. It does not have an automatic charging option for NI-Cd batteries so I messed up the setup configuration. I discharged the battery and charged with a normal 300mAh charger for 8 hours. The pack arrived at 8.12V and the car is driving normally.

Meantime a friend will lend me a more sophisticated charger, with an automatic charge / discharged option to test the pack.

For the use I give the cars the Lipo are not justified. I'm going to buy some NiMH packs. It seems to me to be the safest because most of the time it is my 10 years old son who drives the cars.

Your charger looks to be almost identical in function to the IMAX B6, that has a NiCd delta peak setting (automatic, shuts off as voltage drops just after full charge is achieved), so unless it's been emasculated for some reason, you should be able to access as follows:

BATT TYPE button until PROGRAM SELECT NiCd BATT shows, then press START
DEC or INC button until NiCd CHARGE Aut shows, then press START
DEC or INC to change charge rate from 0.1A to 5.0A, press & hold START until BATTERY CHECK WAIT ... shows

re charge rate, "1C" is generally considered to be a good balance between speed and battery life - charge at the battery capacity so a 1200mAH pack charges at 1.2A, 2500mAH at 2.5A & so on.

I took some time to study the batteries and charger and I think I already understood what happened.

I put the battery to charge the 100mAh, I think is 0.1C, which should give a minimum charge of 15 hours. But the charging stopped a few hours later and I thought the battery was charged. In fact it was not. The charger has a safety option that automatically disconnects after about 3 hours. So didnt have time to load. After disabling this option the load already takes the hours that it should and the battery fully charges.

Meanwhile a neighbor gave me 6 old packs of NI-MH batteries that I'm testing. Apparently only one is dead. It's good to have great neighbors.