Hi Chris and welcome to the forum.

Not such a silly question. As Colin says. However you can get low voltage bleepers from various on line sources, but the voltage on a Nimh battery does tail off rather quickly. Experience is necessary really, sail your boat, notice when it starts to get sluggish, bring it in.

​Ashley

if you have a 'smart' charger – say, the IMax – you can set it to discharge at a specified rate as well as charging. That will then tell you how long your battery will last with a specified drain.

You can also get a cheap Watt Meter, such as this: **LINK** which will tell you how much power your motor is using while it is on the water. Armed with those tools you should have a pretty clear idea of how long your batteries will run for.

The web is also full of simple little low battery warning circuits – eg – **LINK**

The item linked to (from the link) claims to –

Battery balancer

Battery discharger

Battery capacity checker

ESC / Servo PPM tester

Battery internal resistance tester

All out of the water, so not on-board. Still a useful device if used. When looking at Amazon links, it can be illuminating to scroll down the page to the Q&A section and the reviews.

https://hobbyking.com/en_us/hobbykingtm-lipoly-low-voltage-alarm-2s-4s.html?___store=en_us – is an on board audible alarm, useful while the boat is within earshot. but probably not needed if the ESC gives its own warning.

To extend DM's comments a little more – this is a 'ready-to-run' racing boat, so it probably won't be pottering around the lake at all. Battery time calculations are never going to be precise to the minute, so the shop's estimate of 1/4 hour or 1/2 hour are, I think, well estimated with 12 minutes and 26 minutes to when you first feel loss of power.

You have already found out that if you leave a battery for a while it will recover slightly. Running at less than full power, as DM points out, will increase run time – sometimes quite substantially.

Racing boat clubs tend to have a 'rescue boat' ready to recover stranded boats – either a rowboat with a person in or a small model with a 'scoop' at the front.. You will also find that it is beneficial to run on the leeward side of the lake (with the wind blowing towards you) so that any time required to drift in is lowered.

A major use of power meters is to determine efficiency of the motor/prop combination you have in your boat. Since you have an RTR boat, all this will have been optimised by the manufacturer, so you don't really need to do it yourself. You would only really need a power meter if you were going to re-engine or re-prop the boat.

This is a good example of what I was saying earlier – the club people at the lakeside are the first people you should be getting advice from. They would see instantly that you had an RTR boat – we have been giving advice based on general hobby boats you build yourself…

This appears to be the manual for your boat. Is it? **LINK**

It contains the following paras:

"The included ESC features a ‘soft’ low voltage cutoff ( LVC ) that smoothly reduces power to the motor (regardless of the power level you have set with the throttle stick) to let you know the voltage of the battery is close to the 6.0V minimum.

However, even before this reduction in power , if you find that more than the typical amount of throttle/ power is required to cruise or climb you should land the model and disconnect the battery immediately to prevent over-discharge. And while it is possible to continue running the model after the soft LVC occurs, this is NOT recommended. Continued discharging can result in reaching the 5.0V ‘hard’ LVC which may cause permanent damage to the LiPo battery resulting in reduced power and flight duration during subsequent fights ( or failure of the battery entirely which is not covered under warranty). Also, it is not recommended that you run to the soft LVC every time you run. Instead you should be aware of the power level of the battery through out, and if at any time the boat begins to require more throttle/ power than typical to maintain speed you should let the boat run back and disconnect the LiPo battery immediately. Constantly discharging the battery to the soft LVC can still cause permanent damage to the battery so it’s best to use a timer or stop-watch to time the duration of your running and to stop flying at a reasonable time before the soft LVC is reached."

Blimey! Who'd have thought? And not written in Chinglish either! It's a good job DG read them or we'd all still be in the dark.

Mind you, I do remember a customer once ringing me up with a question which was clearly covered in the instructions. When I pointed this out he said that he was calling "just to make sure they're correct"…

DM

In that case I hope the link I provided will be of use. It may not be for your precise model – I did not look too hard on the web for it, and I guess that there are manual downloads or help pages somewhere on the manufacturers web site – **LINK** but it's a manual for a similar boat in their range, so a lot of the advice – perhaps all of it – is going to be of value.

I might direct your attention specifically to the Safety and Maintenance pages, which should always be read and understood before operating a machine….

It looks as if you have a broken propshaft. Did you read the maintenance directions regarding lubrication, and use of loctight on the grub screws?

Edited By Dodgy Geezer on 21/08/2017 21:19:36