Hi DodgyGeezer,
That sounds interesting.

Martin.

Gotcha Colin!
Neat trailer 👍 Chapeau!

Sounds interesting Dodgy, looking forward to that👍

8 degrees c here and still raining. Might try sailing in the street.
Cheers Colin. 🤔

"....Hi Dodgy, welcome back👍
I see you've been tickling the grey cells. Brainstorming👍
"The web is full of low-battery detection circuits ... "..."

Yes - I've been thinking about reversing Taycols. The diode rectifier method is very simple, but does drop a volt or two, and I was wondering about a more elegant solution - which I think I have now. Unfortunately no one else has ever wanted to do this, so there are no prior examples on the web that I can find. Apart from this one now...

I will put something up on another thread, because it's only peripherally connected with battery back-up....

Now a nice 13 deg C, 21.54 hrs, sea fog's gone, moons out, mud's in, and all's well but too cold for fiber-glassing !

On a slightly more relevant note!
DHL advised me they'd loaded my bits n pieces on the truck this morning😊
So Experiments continue at the weekend.
Cheers, Doug 😎
PS now 19.5° in the shade and climbing.
Sky gone from duck egg blue to haze grey. The USN gets everywhere!😉

We appear to have run out of battery stuff anyhow, hijacked is for trucks and planes, don't you mean we're being mutinous ?

Only 18c here today in SA - sun shining with no cloud although winter is our rainy season in the Cape - minimum never lower than 10c at night and when "Berg Winds" blow - anything up to 24c midwinter during the day. Weather a bit better than I recall in Bournemouth.

Once again we all seem to have hijacked a thread !

You just had to be .6 deg higher, show off, but wait till the sun comes out and we'll see what happens (it's raining at the moment) I'll be cooking schnitzengruben on the roof !

09:51 CET Munich: 18.6°C, light breeze and not a cloud in the sky - YET!
Scattered thunder showers expected this afternoon ⚡🌩️

Doug has some spare rain that he could send your way LOL!

Martin.

19.46 hrs and a balmy 18deg C here in Auckland chaps, (just sayin) And it's winter!

BTW; When / If UK does leave the EU we'll start sending it back! 😁

Your welcome.

Martin.

Most generous of you, such altruism! 🙄

You only got a share we have to consider other countries as well.LOL!

Martin.

"Leftovers!?"😮
Please consume a bit more yourselves next time! 😉
The last lot you sent was a bit hefty 🌧️🌧️🌩️🌩️
Doug 😎

Hi Doug,
"English weather " your only getting our leftovers LOL!

Martin.

I use the countdown timer on the 9XR and 9x as well as the alarms as I don't have the telemetry RXs, ( the ESCs I use can be programmed to either cut at the min V set or reduce power at same,- if set to cut, you get a safety get-home by chopping the throttle then applying throttle again, but the 6x was an El Cheapo 6ch from HK (Fli Sky I think,-no display) which they don't sell any more (and now almost impossible to get RXs for). Batt level display was just a try out to see if it was worth gluing one to the front of the TX (see pic- or you could stick one on the plane or boat). TX also has a flashing LED to let you know if Batt is getting low. Converted it to twin throttles for boats, - not enough range for planes (about 300m max - 9XR with JR module has about 3 miles)

Hi Peter,
Thanks for your concern 👍😊
Nope, I was lucky, most of the damage was in the west / south west of Munich and I live on the east side. No hail in our part of Munich. Car was garaged until the evening anyway.
Torrential rain and gale force wind did delay my driving over to the GF for dinner though. Small price to pay compared with others!
No sailing for a couple of weeks now, due to unpredictable weather. Sudden thunderstorms in spring and summer are common in this neck of the woods.
I often looked out of my office window here and remarked to the crew 'Hmm, I don't ever want to hear any more crap from you lot about lousy English weather! Alles klar?'
cheers, Doug 😎

Nothing to do with batteries, but,where you near the hail storm that attacked Munich yesterday, car windshield being broken, def no sailing.⚡

peter😐

Hey! Thought you hitting the sack? What happened? Sack hit back? 🤕😉
Yep, on the LiPo versions (like mine) you can set the threshold for 2.7V upwards.
Didn't know there were also NiMh versions. But then - I haven't looked!

The primary function of these cheap little gadgets is a quick rough indication of the battery voltage, and the individual cell voltages. It's only a rough guide - Go / No Go for another run so to speak. My comparative measurements using a mains Lab voltmeter showed considerable discrepancy so I'm not sure I'd rely on it as an alarm.
OTOH; if it works for your aircraft - Why not?

I agree, LiPo conversion is the way. I've tried my best here but some folks are still afraid of LiPos. I have tried to explain that if you buy quality not cheapest you can find and follow the rules there shouldn't be any problem.
I admit I still have some NiMh which I use together with ESCs which are not 'LiPo safe'; i.e. they do not have the built in cut off function (or throttle limiter on some hi end versions) designed for use with LiPos. So far I have ONLY seen this function for LiPos.

Coming up to midnight up here so it's my turn to 'hit the sack',
G'night all. Doug 😎 💤💤
PS I get RX Low battery warning on the TX display! 😉

Think they only go from 2.6/8 v/cell to 3.8v Doug. Have some which are for REC bat voltage warning but they are only for 4,8v/6v low amp. I plugged one into my TGY 6x TX (runs on 4.8/6v) which I am using NiMh batteries in,(for a boat TX) and it worked ok on that as a display There must be others for higher output somewhere, I'll have a search around. Evening all, (or morning here in my case) John B

P.S we'll have to convert them to LiPos Doug!

No worries JB👍
I also have a couple of these for quick LiPo battery / cell voltage checks.
They are specifically intended for LiPos though, i.e. ca 3.0V or so per cell.
I've noticed many members use NiMh drive batteries. They would need a warning at 1.1V per cell or a little above. Can yours be set to that? Mine can't!
Cheers, Doug 😎
Nice wings BTW 👍

Probably mentioned these before, but if you are wanting to know if your battery is getting low, these twin horn alarms are great. You can set the minimum battery voltage you require with a small button on the unit, to a level which will allow you a good safety margin. You can hear these at around 200m which is plenty far enough for any boat, and they are very cheap (a few dollars on Ali Express, Banggood etc.
I have them in my aircraft (eg pic of one mounted on the outside, - this one has clocked 101mph and you can still hear the alarm over the noise) also they have a continuous led cell V readout . They just plug into the battery balance lead and you can use an extension lead to place them anywhere.
Doug, these are for non electronically inclined people who don't want a challenge or a brain hemorrhage.

Hi Dodgy, welcome back👍
I see you've been tickling the grey cells. Brainstorming👍
"The web is full of low-battery detection circuits ... "
Agreed Dodgy,
Believe I did mention that approach below.
On the other hand it's more fun to DIY! 😉

"An alternative approach might be to detect, .... the actual failure of the R/C signal at the servo due to low voltage." .... "A latchable missing pulse detector coupled to a switch ...."
Agree again.
But loss of signal can have many other (mostly temporary) causes as well, maybe more likely than RX low voltage, a problem which can be practically eliminated by using a separate RX battery anyway. Another reason I prefer not to use the BEC for the RX supply.
All but the very cheapest No Name ESCs also seem to have 'Low voltage cut off' ccts anyway.

Missing pulse detector - OK. A well known 555 cct. But missing pulses can be caused by a temporary signal fade 'brown out' or interference and if your switch latches ...? False Alarm! Fiddling with the detector timing may help there I guess.
Adding a good cell to a low battery is also bad electrical practice anyway. Which will probably end up with the battery and the extra cell being ruined. I believe that is why Martin was thinking about switching to a completely different battery. You'd still need the high current capable switch anyway if you are switching in the drive battery wiring.
As you say you'd probably drive the main battery down below safe limits, where the irreversible chemical changes start. Not very economical given the price of decent batteries.

Pulses off the prop shaft !? Fine if you want/need a rev counter but otherwise ...?
I would prefer to stick to the essential problem Martin wishes to solve, namely; Low main/drive battery voltage detection.

"a boat running slowly would be the best indication to come in" Agreed.👍
Guess martin's basic idea is to double the run time if there is space for a second drive battery.
And maybe a little fun showing the flag 😊
All the best. Cheers, Doug 😎

The web is full of low-battery detection circuits - including those with latchable switching to stop the circuit turning back off when the main battery recovers voltage as it is rested. See the link below.https://www.google.co.uk/search?client=opera&q=low-battery+detection+circuits&sourceid=opera&ie=UTF-8&oe=UTF-8

An alternative approach might be to detect, not the dropping of a voltage to some specific level, but the actual failure of the R/C signal at the servo due to low voltage. You can do this with a 555 easily enough and less than half a dozen components - this is often used to drive a sound generator to find a missing aircraft (just turn off the radio), or some other failsafe action. For instance http://www.circuitstoday.com/missing-pulse-detector-circuit-using-ne555

A latchable missing pulse detector coupled to a switch to add a single C NiMH battery to the main power (and an LED warning) would let you get the absolute maximum out of a battery and then boost the voltage sufficiently for a short home run. That is, if you want to run your batteries down to their limits and you are running on such a low voltage that the BEC is the first thing to go. You could also take pulses off the prop-shaft if you didn't mind the circuit switching in whenever the boat stopped.... 😊

Usually, a boat running slowly would be the best indication to come in and change batteries....

Just kiddin' Rob 😁
Although, a vague idea how to raise the flag is trying to hide behind my last few grey cells🤓
Got an old home made winch driver kicking about to use for some trials.
Just ordered a batch of ICs, relays, and selection of MOSFETs to play with!
So if you see puffs of black smoke and hear loud swearing, in German and English, coming out of the SSE you'll know who it is 😮😉

Four way (All Round) flasher unit prototype is done and tested.
If I have time I'll put up some vid and scope pics of the tests.
Built it while experimenting with improving the brightness of Haig's (Reilly4) strobe unit for his patrol boat.

Next up is the comparator / switch trigger. Tricky bit is setting a stable reference threshold voltage - retires to Man Cave scratching head! Have an idea so have ordered a few chips to test it. Damn, have I still got the right Zeners in my stash!?😮
The actual switching board is the 'easy' bit!

I've been wondering about the current you guys are thinking of switching! Any thoughts on that?
The higher you go the more expensive the power switching elements get. 🤔
So maybe a smaller, lower voltage 'Get me home' battery is the answer, especially if space and weight margin is limited.
I've ordered some 'stuff' to cope with around 10 to 15A max, more than enough for most scale boats / ships I think. The speed merchants would have to dig deeper in their pockets!

Any and all inputs on this welcome Gents (and Ladies Nerys😉)
Cheers, Doug 😎

Hi Doug.
Chicken out ?.....Not really.
The flag thing would indeed be just a gimmick and a LED is far more practical in all respects so I'll definitely 'pass' on that suggestion. But I'll definitely Raise my Hat to your electronics skills for a practical circuit that'l do the switching bit.
Rob.

Maybe the yacht sailing Guys have some suggestions?
They have some awesome and crazy ways for adjusting and setting there sails.

Martin.

Aha! I see you two have 'chickened out' on the flag raising😠😭
Shucks, would be a nice gimmick.
RISE to the challenge lads!👍
All printable suggestions gratefully received😉
Cheers, Doug 😎

I quite agree.
The flag raising was just in case it was a sunny day and you could not see the LED.
(Mind you we don't get that many bright sunny days here in the U.K.)

Martin.

Forget the 'flag raising' mechanics, it's not worth the additional complexity when a simple LED would do the trick and far easier to integrate into the circuitry too. The 'KISS' principle rules OK!

PS I leave the mechanicals of the flag raising to you two Martin and Rob 👍😊
I'll start rummaging in the electricals and component boxes tomorrow😉
Oh well, fish cutter on the back burner again 🙄
PPS: there are actually such low battery indicator boards on the market which it may be possible to rig up to an external driver stage .....

Great minds Robbob 👍👍

Funny you should mention that Martin 😉
I built one many years ago.😊
It used a 5V two pole change over relay to switch to a second battery.
It must be still kicking about somewhere. I had it in my destroyer.
Originally I set it up to work like an overdrive.
I had two 6V SLAs in the ship.
Cruised around on one battery and used the relay to switch the second in series for 'ALL AHEAD EMERGENCY'. RC controlled of course 😉
Was quite spectacular and made some 'speedboat' drivers look silly if they started driving in circles around me while I was cruising 😂🤣 Hotspur was halfway across the lake before they realised I'd gone. Had to go easy on the rudder when flat out though, the heeling was heart stopping😮
Nowadays I might try it with power MOSFETs (like in modern ESCs) instead of the relay. Relay is simpler to build though.

Simple enough to rig the comparator circuit up to either relay or power FETs.
You just need a small single transistor preamp in between to boost the few mA from the chip output to enough to drive the relay or FET switch.
For emergency 'Get Home' use the second battery could just be a small capacity version, if there isn't enough space or weight margin for a second full spec drive battery.
I think I would prefer a high brightness all-round LED flasher to raising a flag.
Plus an alarm horn perhaps.
Although a flag would be a nice gimmick. Cream on top so to speak.
'spose it could be rigged up to small winch and a closed loop of cord with a pulley at the mast top.
Once the basic circuit stands what you use it to drive is only limited by imagination, resources and space and load margins. So get your thinking caps on lads and lasses!!
You don't want to flatten the emergency battery too quick though!
Gotta go now, Dinner with the GF 😋😋😋
CU later, Doug 😎

Over to you Doug....you've been volunteered for the job 😜

Hi Robbob,
Excellent we are part way there already.

Martin.

Nice idea Martin, Doug's the lectrickery wizard so if anyone can come up with something practical...he can.
I would suggest that the circuit operate a solid state switch or relay so that any type of battery or voltage can be switched and a high brightness LED be used to indicate a successful changeover.
Rob.