Batteries!, always a problem in the 50s on "paper round" money, used to cadge,"borrow" or steal batteries for our boats.Used to be able to buy a cheap kit and even a cheap Japanese motor (coupled to the prop shaft with bicycle valve tubing) but it would be unused for weeks until I could afford a battery, and then they did not last long.Used to borrow batts from my dads bike lamps,my grannies gas stove lighter and the door bell!.Also use to be able to remove cells from the "winner 120" batteries from my dads sky queen radio as the HV cells used to discharge first.This was the downfall of glowplug motors,we could start them at home but on getting to the pool the tall 1.5v battery would be flat.My dad showed me how to locate good cells on duff car batteries by putting a load on them and measuring the voltage across each cell,we then emptied the acid out into mums washing up bowl and sawed the good cells out,refilling them with acid filtered through a handkerchief!,this worked a treat for starting glow motors but my hankie and the pocket I kept it in suffered!I eventually sorted the power problem by using a clockwork motor removed from the family gramamphone to fit an autochanger.
Hi Doug I am impressed. There are also LiFe batteries around and are somewhat safer for Tx/Rx use, but require the same care as all Lixx batteries. I am confused by the CONRAD battery rated at 4amp and 30C. I would say this suggests a 120A max burst current. I can't see 60C marked on the battery. It may well be capable of being charged at 2C ie 8amps but like you I would never consider charging at this rate. The higher power and performance batteries are capable of taking higher charges and will withstand the heavy discharges demanded by those who race fast models. However such batteries are for the serious racers and do not come cheap. I do have one concern and that is your mention of overnight charging. I agree this may be OK for NiCad, NiMh and SLA's but LiXX batteries should never be left on charge unattended and certainly not overnight. My chargers have settings for Lixx batteries that adjust the charge current for the voltage and capacity and automatically give a varied charge current until the battery capacity is achieved, balancing the cells at the same time. Dave
Aye aye sir! Message received and understood! 👍 Go with what you have first. Don't look bad, but you have a pretty big boat there! One thing; NiCad 😡 that's a No No these days, at least swap it for a NiMh. For such a big boat and thirsty motor I would probably go for at least a 5000mAh. Aboat that size can surely carry it. Otherwise you could try a lightweight LiPo 2S = 7.4V. IF the ESC is declared as 'LiPo safe', then it shuts down when the cell voltage reaches the minimum, usually set 3.0 or 3.2 volts. A decent modern 2.4Gig RC set (e.g the Turnigy i6) will tell you the battery voltage by telemetry back to the TX display! 😉 If you ain't happy with the performance an upgrade may well cost you a candlelight dinner .... on top of the 80 quid! 😲😉😉 Let us know how it goes (the boat I mean 😁) Cheers Doug 😎
Hi Dave Wow! What a treasure chest. 👍 I have a few, mostly rescued from old video recorders. Next time an accu drill or screwdriver or whatever packs up must remember to strip the motor (and gears?). Many years ago in Conrad looking at their motor selection there was big box of mini low voltage motors so I, in my naivety I bought a bundle for peanuts. Several years later I realised they were surplus from vibrator dildo production! 😲 Was a pain grinding the damn weights off the shafts 🤔 You live and learn. Keep up the good works, Cheers Doug 😎
Hi Chris They are all based on 550 motors made by Mabuchi or Johnson. They were GP motors available in different configurations for specific purposes. You can look on data tables to find the exact specs if the motors still have visible markings. The Graupner is designed to run on 8.4volts but the motors can be wound to run on different voltages. I suspect the one with the fan is taken from an electric drill. They used to be popular with the fly boys pre brushless so they are available in large quantities at cheap prices. I suggest you run them with an ammeter connected to a 8.4 (approx) battery and see what current they draw. High current would be good for a fast runaround for 10 mins or so, low current will have more tork and be suitable for a scale cabin cruiser/tug etc. If you have two that draw roughly the same current at the same volts they might be suitable in a twin prop, provided they both rotate at the same speed. Dave
I apologise if this has already been covered here but I am now at the point of installing the motor in my new model. The motor is a Graupner speed 600, and the specs are : Nominal voltage 8.4 V Operating voltage range 4.8-9,6 V No-load rpm 15500 No-load current drain 1.8 A Current drain at max. efficiency 11 A Current drain when stalled 70 A Max. efficiency without gearbox 75 % If I use 8.4 volts what size wiring do I need? Do I need to cater for the 70A current or the 11A current, or somewhere in between, with a fuse? Sorry to be a bit dim on this but I am confused (with most things these days!) Chris
Glad to hear you have solved your problem. Overrunning any system will result in some interesting issues and you are fortunate that yours shut down or failed open circuit otherwise all the electronics could have cooked. If you are getting a separate on-board power source the best option is to go for a switched mode supply, most will give you lots of amps without the heat problems of an ESC and are designed to work with higher battery voltages. You must disconnect any +ve power lead from any ESC to your rx. If your ESC has an on/off switch do make sure it is switched on, preferable before you power up the switched mode unit. Be good to see some pics or on water video Dave
Oh yeh! Every picture tells a story! Had we known that at the beginning we would have missed out on an interesting debate 😉 Looks like you triggered the ESC's thermal cut-out. Lucky it wasn't permanently damaged. MIL Standard 217 Handbook for calculating MTBF (Mean Time Between Failure) lists the two top Stress Factors as Environment - Over-temperature and Exceeding rated Voltage - Over-volts. 🤔 After that comes Component Count - the more parts the more likely it is that one will go PHUT when you need it 😡 During my recently ended career I had a lot to do with MTBF for naval ship systems, and the associated FMECA - Failure Mode Effect And Cause Analysis! Lesson learned!? We all learn from our mistakes and those of others - I hope😉 Have fun with the new ESCs.👍 Don't get any speeding tickets 😉 Cheers Doug 😎 PS having a second power supply in the system more than doubles the MTBF. BTW: Where do you buy your 4.6 cell LiPos !?😲
Regarding Doug's suggestion of putting a diode in the red wire from two ESC's, the forward voltage drop in the diode will reduce the voltage at the receiver by 0.6 volt less than the BEC puts out. Is this going to affect the operation of the receiver and everything connected to it? Does the BEC voltage vary depending on the load on the ESC, or is it stable enough? Roy
Hi RHBaker What kind of ESCs are you using? Doug I would not use both BEC units even with your diode in place. Most manufacturers advise disconnecting one positive lead completely. Also if the ESC has a switch both ESCs must be switched on as I have damaged one of mine because it was switched off but still appeared to work. Result was similar to RH Bakers problem. I suspect the Mosfet gate voltage was exceeded without the internal power to the ESC, causing it to go permanently on. I also believe this may have been developed over time as I am sure this instance was not the first. The ESC still worked OK in reverse but went full on as soon as the stick on the tx was put forward. Further checking also revealed the internal BEC was dead. Sealed unit so no chance to repair. Both As Doug says a separate power supply is a better option if you have room, and modern switched mode supplies are freely available and will deliver much greater power for all your servos, lights etc Dave
Hi Doug I use a charger that measures the internal resistance of my batteries. Damaged cells exhibit high internal resistance and cannot be recovered to their full capacity. I agree you can flash the cells and they will recover the voltage but will not take or deliver the current. As a result they will quickly discharge under load and prevent the whole pack from delivering its full capacity. I sail model boats on a large lake and recovering a model due to battery failure is difficult, so I don't risk using sub standard batteries. I have not used wet Lead acid batteries for many years but I agree the Epsom salts trick did work on such batteries. I agree flashing is highly dangerous with any battery as there is a high risk of explosion. Great care should be taken and, unless you are competent, should not be attempted. Take care Dave
Good result Just what I was about to suggest as it happened to me.Re testing through insulation Bang Good sell pairs of adaptors to fit over the tips of standard test probes. Sharp as needles but strong enough to pierce most insulation. Nicads NiMhs and others develop needles or dentricles inside which short out the anode to cathode internally These can be dissolved or blasted away by flashing them with a higher voltage .A/C or D/C. I use my welder. Hold one contact to one battery terminal and flash the other with the other welder terminal. Just a glancing blow DO NOT hold it in place.There is no real need to split the pack but can if you would rather treat individual cells.They can be done without unsoldering them just use some wire held in the earth clamp and stickholder or feed gun to reach the ends of each cell.You get the picture .I have done this with battery powered tools for years .I have a 24 volt drill that is still on original battery after more than 10yrs. Another way is connect the supplied charger and plug in and switch on waggle the plug in wall socket in such a way as to make and break contact about 16 or more times. Not as good as the flashing method but works. Wet cells can be improved by putting 2 or three teaspoons of Epson Salts in each cell. Many tops can be chiseled/prized off to access the interior and glued back on with plumbers solvent cement or similar............Gorilla glue would probably do it too. Here 's hoping I've saved a few quid for some of you. BTW I wouldn't know if this would work for Lipos.I wouldn't want to be the first to try 😆🤐Here is the page https://www.banggood.com/search/insulation-piercing-needles....
Gentlemen, after charging the packs at 100mA for 24 hours, I stripped off the heat shrink from one pack for testing. Unloaded, 4 cells in the pack showed 1.40 volts on my multimeter, with one cell showing 1.37V - near as dammit to 7V for the pack. With a load applied, the current started at 0.95A, dropping to 0.9A when the voltage fell to 1.15. The one cell was consistently the lowest, but never more than ~30mV. From this test I calculated that the capacity used was 2250mAh. Not the rated capacity of 2550mAh, but almost there. During these tests I discovered that the recording meter that I had been relying on for the previous testing was giving inconsistent readings, a fact I only discovered when I started using my multimeter. This possibly resulted in my considering the battery discharged in previous tests, when it was not. Roy
Ron Yes it provides a good close fitting base and with a top clamp will give solid and aligned support. The final top clamp should not be too tight. I usually set with a low voltage battery connected via an ammeter and adjust for the lowest current. Happy days dave
Hi Ron Its food wrap as shown by Doug. I am posting some pics of a very rough set up to illustrate the process. I have used some white tissue to illustrate the white bath sealant but I think you will get the idea. The mounting blocks need to be wide enough to take any screw fixing you choose to use and can be mounted direct to the hull. Make a plate shaped to the motor diameter to hold and use some soft rubber or similar in between the plate and motor. Dont place this until the silicon has set and you have refitted the motor. I align by connecting the motor to the shaft and gently pushing into the silicon until level. Use a low voltage battery to make sure it runs freely. Then leave to set, could be a couple of days if cold before carefully removing the motor with film. Remove film and refit. As mentioned make sure any cooling holes on the motor are not blocked. Hope this helps but please ask if you need clarification. Dave