Absolutely correct Sir Dave! There are statistics, lies and damned lies! Test gear calibration was a professional pain in the ... for me for many years. All comments re ambient temperature, internal resistance absolutely spot on👍 Goes back to my comment in the debate you mentioned, pay a bit more for the batteries and you'll get more out of 'em. But unfortunately 'what goes in does not (always) come out' 🤔 The capacities printed on the jacket should always be taken with the proverbial pinch! They are only an indication of perfect performance in 'this the most perfect of all possible worlds'! I remember matched cells too, much more expensive, and not critical for scale ships. Cheers Doug 😎
Hi Roy I can understand your conundrum. My work at one time involved gathering and presenting statistics. The difficult part was knowing what answer was expected. There are statistics and dammed lies and at the end of the day they are at best an indication, but should be taken with a pinch of salt. To try and shed some light: What charger were you using and was it calibrated and if so who by? Same goes for the recorder. Did you measure the temperature when charging and discharging. Looking at your chart I not sure I quite agree with your consumption calculation as the 2.55 amps was at best for no more than 40 mins. Batteries will waste energy in the form of heat and this explains why more energy is required to charge to the retained capacity. We did discuss the battery internal resistance earlier and this can have a real effect on the capacity and the batteries ability to deliver. Assuming your measuring equipment is correct then I believe the differences are likely to be due to temperature variations caused by the internal resistance. If when you charge your pack one cell is noticeably warmer than the rest of the pack it has a higher internal resistance. At one time you used to be able to buy race packs which had been formed from individual cells that had been matched. Cost a lot more but if you were racing with the pack they gave you the edge. Cheers Dave
Hi Fred For a 3' boat the 700 size motors and required batteries will make for a very heavy model. The table Doug has provided indicates a speed 600 size motor would be more suited and would certainly be about half the weight. I have two 700 motors in a 4' hull for a RN Exploit model which does require the weight and can carry the large capacity batteries. Each motor can and does draw about 15-18 amps. I do not know your model but if it is anything like the Rivas then weight and internal space will be at a premium.
First, thanks to all for their helpful replies. To answer a few questions: 1) The installation has two independently controlled ESC/Power train systems in a long, narrow patrol boat. They were fitted for maneuverability and achieve that target well. 2) All Rx functions failed when the ESC failed, pointing to a BEC circuit failure. 3) The ESCs are of UK manufacture and, I hasten to add, have previously worked well. Have used this product for years and am satisfied with it. 4) The presumed reason for failure was, in a effort to increase the performance and reduce the weight of the model the power has (after a series of trials with 9 to 14 v NiMh batteries) gradually evolved to a 17 volt Li-Po system. This final iteration had performed well for some time. Guess using a 12 volt ESC on a 17 volt system would eventually lead to failure - Mea Culpa! Funnily enough,when cooled down all functions work properly - until they heat up again. Have ordered 2 more ESCs from the same manufacturer, but now rated at 12 - 24 volts - should solve the issue. In view of the various recommendations to use a separate Rx power system, think this is the easiest solution to avoid a total system failure in future. Again, thanks for the advice.
Hi Doug...it's this one: and no that little issue is still ongoing...have changed my Tx/Rx/ESC to Turnigy....the Mtroniks ESC's I was using were 'compromised' regarding the set-up...I now have a programmable card to set up my ESC's - The Dauntless has been converted to a Police launch, it's a twin screw using two Electronize ESC's.....just needs a Tx/Rx and batteries, possibly looking at lead acid x2
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
I have seen this done a few times online and figured it would be a quick turn around; I was wrong. Every time I think I have it licked, another problem arises. I am at two pumps, one motor, two micro switches and three servos. I do not have batteries or cooling for the motor figured out. But when I get tired of my scratch builds I go back to this. I did my math and six vessels await my attention plus these two fine examples. Then, I start looking at plans for another one. I may have a problem. Latest picture is the ballast tank sealed with fittings.
Hi Rolf Hope ewe are successful in you bid. Other than the paint the main area of problem is the old IC engine area with fuel getting in the wood. As for cheap parts, Hobbyking. Radios, brushless motors, ESCs, batteries and props. The boat is big, so a motor in the 50mm diameter with about a 50mm 2 blade prop. We will to see what happens and maybe a few posts with pics(we love pics), good luck. Canabus
Thank you, AllenA! Well, no science behind the running time. As long as I run at low speeds it just happens everything seems fine. But when I put the throttle down... then all is over within 15 minutes or so. I pretty much stick to the same power layout. 540 motors with 30A controllers, 2000 or higher mAh capacity and 35mm or 40mm props and 4mm shafts. Dirty Deeds is a bit special. I was on my learning curve (I'm still there!) so due to a novice error I used a 2mm shaft so I had to get a special propeller and a big mean battery (kind of a Viagra approach). So, I had a 4-bladed 35mm propeller bored for the 2mm shaft and a 10.8v 4000 mah battery pack. A bit in the heavy side but it gave the boat nice stability. I can achieve better running time with Lipos, but I'm an old-fashioned guy still concerned with the maintenance Lipos involve and do appreciate a bit more of the weight offered by NIHMs, not to mention I'm a cheap guy (LOL). Something that really worked for me is the choice of propellers. I noticed a remarkable run-time difference between plastic and metal (yes, more expensive) propellers, but it is well-spent money. Other boats I have run with 9.8v 2000 mAH batteries achieving almost 50 min at low speeds, which is OK with some of my models for realistic ride purposes. Here I have my two "inspirational" pics.
Hi both It would appear that one cell is damaged/faulty. I have had trouble with bad meter connections in the past and it can cause all kinds of trouble & strife. The pack will be no better than the weakest cell. If you have a good electronic charger it will give you the internal resistance of the whole battery in milliohms. I checked all my NiMh batteries we use for the public sails and found several that had high internal resistance. Replacing the faulty (>1.2v) cell restored the pack to full capacity Dave
In old money Edward it is 28" long and weighs 11lb , full with water. Its a bit on the heavy side of course but then i am more interested in the working and making of the thing and the individual components rather than blistering speed. If i wanted that i would use a brushless motor and modern batteries! Each to his own. What do you make ? Les Breame
I have always embraced new technology and agree some of the older skillsets are fast disappearing as it is now possible to design and build almost anything from an electronic gizmo. I embrace these new techniques and have delved into 3d CAD and printers and can now make most of the bits I need. I started like many born just after the war with plastic kits followed by balsa and tissue planes, model trains, cars, boats then into electronics and early RC. I get great pleasure from the building either scratch or kit but I do worry that many prefer to just buy the finished product. I still have my IC engines and planes from my flying days but for all but the fast racers, brushless more than meets the power requirements for our scale models, but I don't deny or object to the many who still enjoy IC and have access to permitted venues. Battery power has improved over the years and Lithium batteries are capable of delivering massive power at little weight. Provided they are handled and treated correctly they are safe to use but rather like fireworks incorrect handling can be unpredictable and dangerous. This refurbishment really goes back to basics and will result in a model being restored and enjoyed for many years and Colin has certainly shown us some new techniques. I doubt if some of the off the shelf newer models will survive quite so long. Dave
Hi RNinMunich I agree with you past, respect the past but move forward. With a lot of areas of limit to IC motors we have to move to brushless motors and Lipo batteries. I have changed over with the times and running brushless motors in my Aerokits Sea Hornet, Sea Commander and a restoring a Precedent Huntsman. These old boats can go as fast if not faster with the change over. Canabus