Thanks for your reply Chris F. I am thinking of NiMH batteries for my boat which is a kind of catamaran. I based it on the boat featured in the film RED with Bruce Willis, a Daytona Eliminator (a bit ambitious for a first model) and I must post a photo soon. It weighs about 2.5kg and is powered by (but not at the moment!) a Torpedo 500 motor. Spence.

You're welcome, Spence. I'm glad that what I wrote was useful to you.
When doing modeling (especially RC) you can make mistakes and cause small or large damage, you have to take this into account.
But a minimum of planning and precautions are necessary, just like you did.

I agree with you a lead acid battery would be too heavy for your boat.
The weight of this type of battery would have too much of an impact on the 2.5 kg total weight. Sorry, I didn't know this information.

All the more reason why ChrisF's advice is valid.

Thanks Alessandro for all the information you sent me. My ESC is a Mtronics Viper Marine 15a not 25 as I previously posted and is the plug 'n' play version. This model supports 12v apparently, after looking at the spec. sheet. I've just tried a 12v AA pack(all I have at the moment as well as 6v) and the motor briefly fired up then nothing (servo has always worked). I am thinking of a NiMH pack as I don't think the boat will handle the weight with Lead Acid( boat only weighs 2.5kg all told). Thanks for you continued interest, I appreciate it. Regards Spence.

Thanks so much Len and Chris.
I couldn't give a correct interpretation to this information. I'm always left wondering about the exact translation.
Thanks to you I have now understood the reason and meaning of this limitation on Lipo and I agree with you.

Regarding NiMh batteries I agree that they can be another good solution. In fact, the voltage adapts very well and, certainly, they weigh less.
In my latest model I thought about lead batteries because that weight was already calculated but I already had plan B ready. In case I had to recover some weight I had planned to replace the lead batteries with NiMh batteries.
Let me explain better if I had needed more ballast for greater stability or if I had needed to raise the freeboard, the only way was to act on the batteries, because I had already made all the savings possible on the rest.
Since the weights remained within the limits I had set myself by design, I didn't need to buy NiMh batteries and I saved some money.

I think they do not recommend LiPos if there is no low voltage shut off is the fact that if you run a LiPo below a certain voltage level non-reversable damage can be caused to the battery. Len

They don't list LiPos as that ESC doesn't have a low-voltage cut-off. Volts are volts at the end of the day so I don't see why they wouldn't work but for safety use another device for warning of low voltage.

But I wouldn't do that anyway as they do one for use with LiPos that has low-voltage protection built in.

What boat is this set up for as NiMh batteries might be suitable rather than heavy lead acid?

Oh okay, Spence. I searched on the internet.
Maybe I found the data I was asking for.

They are the ones in the link below:

Apparently the voltage is right (at the limit but okay).
Lead acid batteries are fine.
They seem to discourage or even ban Lipo batteries.
I'm a little worried about the amperage, only 15 Ampere, it's not a lot but I hope it's enough for your electric motor.
Without impediments this electric motor should not absorb so much.
To be safe I recommend you put a fuse.

I would have opted for a 6 volt lead acid battery.

Attention, I am not discarding the idea of ​​a 12 volt battery (because we have seen that it should be fine for the characteristics of the ESC and the motor), but also consider these solutions if you feel like it:

You could buy two 6 volt 4.5 Ah AGM type lead acid batteries.

This way you can do as many tests as you want.
Try a single 6 volt battery, if the boost doesn't satisfy you, put the batteries in series and try 12 volts.
If you don't have overheating problems (maybe check the currents) you can leave the 12 volts.
If you like driving more with 6 volts, which is the nominal voltage of the electric motor (or at least that's what it says on the characteristics I found on the internet) you haven't wasted the extra battery.
1. If you only want to insert one into the hull, you will keep the other as a reserve.
2. If you put them in parallel you will have greater autonomy than just one and you will not have to change configuration. You will use the ESC's BEC.
3. You can use one battery for ESC and motor and the other for receiver and servo (with isolated BEC positive).

3 is the one I prefer.

https://www.mtroniks.net/prod/Boat-Speed-Controls/Viper-Marine-15-pnp.htm

Hi Spence. She waits a moment.
Be careful using a 12 volt battery.
12 volts is fine for that motor which has a range (at least according to the photo you showed) of 4.5 - 15 volts, but are you sure that the ESC supports this voltage?
Furthermore, it cannot be ruled out with certainty whether or not the ESC also has problems.
Can you give me some features of this ESC?

Thanks guys for your informative replies. I have a similar 12v battery pack that I'll try but I think I'll go get a Lead acid one as Allessandro SPQR suggested. I checked all the connections with a mutimeter and they tested good but the motor was only receiving 0.5 - 0.7v at full throttle so you are all spot on with your information. I can't thank you all enough because I was considering swapping out the ESC for another one. Spence.

Hi Spence I think the other modelers have given you enough guidance to solve the problem.

In general, when there is an electrical problem, I can advise you to try to isolate it.
So we start from one end and go to the other, for example from the electric motor (end user) to the battery.
You will have to check the integrity of the wires, the connections (checking the various types of connectors and switches), the voltages on each element and the currents circulating in the circuit.
Checking that the right voltage reaches the motor may not be sufficient, because there may not be enough power to start it (therefore there may not be enough current, P=V x I).
It seems to me that we had already addressed this problem in another topic but it is better to repeat it.
Providing a brushed electric motor with the right rated voltage does not mean being sure that it will start if the current is limited.
I think I also made some demonstration videos about it. If you want I'll send them to you.

What I told you concerns a very general discussion which is always valid, but in your case I can tell you that I would never use alkaline batteries to drive a motor through an ESC, much less the AA type.
If you don't have weight problems, you can use lead batteries from the VRLA (Valve Regulated Lead Acid) family of the AGM (Absorbed Glass Mat) type. This is the precise wording, but it is the simple lead batteries that differ from the lead batteries in cars (in which there is liquid and cannot be turned or upside down) and from the gel ones.
They are cheap and, regardless of your problem, you will have great autonomy. For example, I use 6 volt 4.5 Ah batteries.

It goes beyond the question you asked but I want to tell you that it is better not to reduce the section of the cables.
By using the headphone connector you have switched to a significantly smaller wire gauge than the ESC. This is definitely not the cause of your problem but it is not a good procedure; should be avoided.
Furthermore, I prefer to differentiate the power supply of the receiver and servos (with a dedicated six volt battery without BEC) from that dedicated to the ESC and the motor (isolating the positive of the BEC).