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Andrew McKelvey 1

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  1. Someone somewhere thinks there is validity in being able to measure cell resistance, my question is what do you do with the answer, no one has gone near an answer yet
  2. The video I watched showed typical resistance values for a new battery 4 cell of between 6 and 8 micro ohms, shown on the charger per cell, so adding them together is more than 20 micro ohm so that would write off a new battery so I took it as a value for each cell of over 20 would be enough to write off a battery of cells. My chargers don’t calculate the cell resistance, probably because they are circa 10 years old and reasonably cheap.
  3. DickW I think I may have found an answer on the t internet, There is a dc test to calculate battery internal resistance, open circuit voltage (OCV) with no load, followed by the second reading with a load; Ohm’s law calculates the resistance value (voltage difference divided by current equals resistance).= internal resistance. My guess would be the higher the load current the more accurate the result? I also found a video of a guy explaining the in’s and out’s of lipo’s, not sure his qualifications but he sounded like he knew what he was on about. His take on it was New battery’s of various capacities return an resistance of below 10micro ohms and continue to be usable up to 20 micro ohms and any thing above that should be retired. I normally use a 12v 60w headlamp bulb to discharge any unused lipos back to storage voltage (actually x2 to increase the current) The effect of the higher internal resistance reduces terminal voltage under load, the prop spins slower and causes more heat to be generated in the battery which makes it hotter and thus not what we want. This has taken most of the day so now I need to test my older lipo’s, thanks for the input guys
  4. I didn’t fly for about three of those due to the pandemic so they where stored with a storage charge and never abused before hand. I have one of those data loggers that got a write up in RCM&E a few years ago and have used that, my charger will only discharge at a few amps, I was hoping to emulate a real life situation and pull about 40A and see what that did to voltage etc but apart from giving me some electrical values how does that equate to how good the battery is? I have only ever binned one battery that puffed up severely, they seem to get demoted to powering hand drills etc but discovered that Li-On cells from laptop packs do a good job there after the ni-mh and ni-cads pack in. Requires surgery with a dremel but at least keeps then out of the landfill.
  5. I have just reinvested a healthy chunk of money in buying some new li-po batteries in the belief that the old ones I have may no longer be up to it. aka 4cell 3300mAh 60C as compared to the same with 20C and being about 6 years old or more. The comparison using my wattmeter with fully charged batteries in my plane setup gives nearly a 100 w difference , ie a difference of about 6 - 8A draw at full throttle and the older battery being about a volt or more down on the new one. I know this is down to internal resistance of the battery which has worsened with age and I could do comparison checks of my older battery's against new one but I am reluctant to do a load of testing with an 12x6 prop wizzing round at full chat just to provide the load plus the wind factor isn't good in the model room. The questions! 1 How do you test an battery for capacity and obtain comparative results 2 If you manage to compute the internal resistance of said item how do you determine a pass or fail 3 Is there a method or a bit of technology I can use that will mean I am not holding down my plane and applying full throttle and trying to read the numbers on my wattmeter. Your thought please will be gratefully received, I have more than enough electrical test equipment to do the measurements I just dont know what the results mean other than the old battery makes the plane unflyable and the new ones make it a pleasure to fly.
  6. I have a HP Envy 4500 think it is about 4 years old now, bought it in Currys, it is combined inkjet printer scanner copier and prints double sided A4 is wifi enabled so you can print direct, via a network or has a printer cable port and for the money was/is a cracking printer cost about £49 and there are newer versions available that has the same functions. Never had an issue with it and setup is a doddle. The downside, depending upon how much printing you do the combined 301 colour and black cartridge pack are around £26 and buying them singly significantly bumps the price up, a 301 Black cartridge is about £19, you can get an XL version but I have never used one, the tri colour lasts longer than the black because I don't print a lot of colour. The upside of this is you can use the printer in single cartridge mode, a setting deep in the software so if your black runs out at an inopportune moment you can still print, single cartridge mode I think it's called.
  7. Over the weekend I had reason to go looking for some information and thought I know I'll go and look it up in the magazine to check. Well, I tried every permutation of login id customer number and password and whatever I had and gave up in the end. Just spoken to a very helpful lady on the end of the helpline who now informs me I need a Digital and Print subscription to get access to the Digital Archive, I did explain I have used it before and that was under mytimemedia now we are with a new company mortons we have to pay and extra £12 a year to retain that facility. So, if you like me wondered why you can't access the Digital Archive or even read this month's mag online like what you used to do it's because you like me only have a Print subscription and not Digital and Print subscription. I don't know what I think at the moment, and I am erring on the side of caution because I don't want to make any hasty decisions but in recent months, I haven't been that taken with the content of the mag and since losing a couple of contributors who were key to my enjoyment the whole thing leave a sour taste.
  8. Max Z I don't suppose you have the script and a schematic available that you could send me. I have an Arduino ready to program and hook up..
  9. I just thought that proportional speed control would be a bi product of using off the shelf speed controllers with radio control, just a bit more refined than on off. I have made up a battery with Li Ion cells from a redundant laptop battery three in parallel each side which is about 3.3v and I charge it with one of my multi chargers at 6 and a bit volts both banks of cells are in series and it works well, I have only recharged it once and have had the bulldozer all over the house a lot better than the old U2 batteries as I seem to remember
  10. Thanks for the replies guys, I am in a much better position in understanding what I need to do. At the moment the control is on off via a couple of levers which are effectively change over contacts. I need to find out how much current the motors draw but as it was power by 4;U2 cells 2 each side it isn’t going to be a lot. I need to do a bit of experimentation with one of these mixers or even a couple of brushed esc connected to a receiver and see if something like a v tail mix will do it but I definitely have more idea now Thanks. I would have thought that the esc’s being proportional the voltage applied is also proportional so even a six volts i can limit the volts to about three, I am running it off 2 Li Ion cells at the moment which are 3.4v without any problem.
  11. I have an old Marx-A-Power Bulldozer which I am planning on installing some radio control to drive it. At the moment it has two brushed motors of 3v one for left track and one for right track with independent control. I require my control to drive the vehicle forward backward and steer. I would like proportional speed control, it is either on or off at the moment, my guess is that those of us that have tanks and other tracked vehicles have a solution to the problem but I don’t know what it is, is there an esc that will do the job, do I need two esc’s, do I need a mix in my tranny to drive two channels, how is it done. Any info will be great fully received to point me in the right direction. I could quite easily design something and then find a solution of the shelf. I want to keep the 3v motors if I can so as to be reverse any mods I make.
  12. For some inexplicable reason and actually reading this thread helped enormously, I think I am sorted...doh!
  13. It would seem my browser was logging me into the forum or I hadn't specifically logged out yesterday
  14. The main forum screen shows I am logged in as Andrew Mckelvey 1, I didn't log into the forum site specifically so I don't know if my browser logged me in or there is some sort of pass thru authentication. I am using MS Edge on my laptop Last evening when I tried this and then tried posting I got an error telling me my email address is already in use?
  15. Early Bird This morning I have logged into the Main Site and got a banner which said I had logged in successfully using my id Andrew Mckelvey 1, however when I go to subscriber services I get the screen you posted. I then have clicked on forum which is how I got here.
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