[RCSE] Re: Redundancy for Scale
You can go overboard on a scale project with redundancy, but a scale ship is no more difficult to wire up than anything else. I take advantage of the fact that most (if not all) scale ships are heavy to begin with, and require significant amounts of nose weight to balance. The answer, big batteries. I use 2400 mah C cells, which makes for a nice heavy pack. In my 1/4 scale K-8, balance this kind of battery plus another pound or so. In my SBXC (another big ship), I use the 2400 mah plus about 10 oz. Hope this helps. Jim Thomas
[RCSE] Re: Redundancy for Scale
Oh boy. This is a can of worms we've discussed before. My personal paraphrase of the topic is that dual batteries are not worth it. If you typically maintain your batteries, you'll be gaining very little. If you typically skimp on your battery maintenance, you'll be gaining very little. Plus, how will you install the redundant battery? Disagreements exist here as well. If you add extra components, you add points of failure. Often these points will be mission critical and your added redundancy will STILL be adding single points where a failure will equal loss of the plane. So what will you have gained? In light of the above, I suggest: Use a new battery and new wires and connectors. Test your battery regularly. REPLACE your battery regularly, approximately once every two years. If it's a VERY expensive plane or if you're a worrier do it every year. Bill Swingle Janesville, CA RCSE-List facilities provided by Model Airplane News. Send subscribe and unsubscribe requests to [EMAIL PROTECTED] Please note that subscribe and unsubscribe messages must be sent in text only format with MIME turned off. Email sent from web based email such as Hotmail and AOL are generally NOT in text format
Re: [RCSE] Re: Redundancy for Scale
I just ordered a 1/3 scale all carbon, super stiff, super heavy, OH MY GAWD gorgeous, DG800 best display of a molded scale ship I've ever seen. The same one Mike Smith got. It's not exactly, uh... free. But it is gorgeous. And with 5K plus radio floating (or in this case) haulin' ass around the sky... I'll be going with redundant systems. I asked a fellow soaring geek who knows much more about these types of systems than I. Here is his reply: As far as batteries go, on anything with the room I use dual packs of the same cell count, two switches and plug into any two open slots. If no open slots, then I just use a Y to plug the battery into one side and whatever servo n the other side. Depending on how much weight you need up front and the available space you can use Nicad or NiMH packs of anything between 1950 to 4000 mAh. Don't get sucked into using battery backers or any other just nonsense. 2 packs, 2 switches, plugged into the RX. Easy as pie, plenty of capacity and a redundant system. The reason I like 2 pack set ups is the redundancy and the fact that it splits the load between the two packs. SO each sees half the load or current draw. Keeps voltage depression under high load to a minimum. And I like 2 switches since they are the cheapest POS we use and they are really the failure point that you are trying to eliminate. On my TD ships I don't even use them, that's how much I distrust them. Here's a good resource for dual pack set ups: http://www.rcbatteryclinic.com/parallel.html See you guys at the aerotows... I'll be the one going really really fast... To see the model - go here. Not a great website, but Thomas has been great to work with. www.xl-sailplanes.com D __ Do You Yahoo!? Tired of spam? Yahoo! Mail has the best spam protection around http://mail.yahoo.com RCSE-List facilities provided by Model Airplane News. Send subscribe and unsubscribe requests to [EMAIL PROTECTED] Please note that subscribe and unsubscribe messages must be sent in text only format with MIME turned off. Email sent from web based email such as Hotmail and AOL are generally NOT in text format
Re: [RCSE] Re: Redundancy for Scale
Hi Bill, Replacing batteries, or switches, or anything regularly, especially if the original components in use are healthy, is full of danger! The odds are the replacement will fail where the perfectly good component pulled out has proved already it's integrity. Every time you introduce a new component, like a battery pack, you have now introduced an unknown. You have no idea if it is put together correctly, the crimps are good, all the cells are operational to the same degree, etc. Folks have employed this logic of replacing their batter packs every year without exception, only to experience a crash because that brand new part failed. You are best to stick with components that have proven themselves to function properly, especially after many flights. Only replace battery packs when they have reached the end of their useful life (whatever that may be). As to adding extra points of failure, I disagree. If something fails on either of the separate packs (including a short), the other pack stands an excellent chance of continuing to supply PWR. The alternative os well, no control. Quoting Bill Swingle [EMAIL PROTECTED]: Oh boy. This is a can of worms we've discussed before. My personal paraphrase of the topic is that dual batteries are not worth it. If you typically maintain your batteries, you'll be gaining very little. If you typically skimp on your battery maintenance, you'll be gaining very little. Plus, how will you install the redundant battery? Disagreements exist here as well. If you add extra components, you add points of failure. Often these points will be mission critical and your added redundancy will STILL be adding single points where a failure will equal loss of the plane. So what will you have gained? In light of the above, I suggest: Use a new battery and new wires and connectors. Test your battery regularly. REPLACE your battery regularly, approximately once every two years. If it's a VERY expensive plane or if you're a worrier do it every year. Bill Swingle Janesville, CA RCSE-List facilities provided by Model Airplane News. Send subscribe and unsubscribe requests to [EMAIL PROTECTED] Please note that subscribe and unsubscribe messages must be sent in text only format with MIME turned off. Email sent from web based email such as Hotmail and AOL are generally NOT in text format Simon Van Leeuwen PnP Systems - The E-Harness of Choice Radius Systems Cogito Ergo Zoom RCSE-List facilities provided by Model Airplane News. Send subscribe and unsubscribe requests to [EMAIL PROTECTED] Please note that subscribe and unsubscribe messages must be sent in text only format with MIME turned off. Email sent from web based email such as Hotmail and AOL are generally NOT in text format
Re: [RCSE] Re: Redundancy for Scale
I agree, however you could take that pound of dead weight out and put in a second pack and some significant peace of mind! Quoting [EMAIL PROTECTED]: You can go overboard on a scale project with redundancy, but a scale ship is no more difficult to wire up than anything else. I take advantage of the fact that most (if not all) scale ships are heavy to begin with, and require significant amounts of nose weight to balance. The answer, big batteries. I use 2400 mah C cells, which makes for a nice heavy pack. In my 1/4 scale K-8, balance this kind of battery plus another pound or so. In my SBXC (another big ship), I use the 2400 mah plus about 10 oz. Hope this helps. Jim Thomas Simon Van Leeuwen PnP Systems - The E-Harness of Choice Radius Systems Cogito Ergo Zoom RCSE-List facilities provided by Model Airplane News. Send subscribe and unsubscribe requests to [EMAIL PROTECTED] Please note that subscribe and unsubscribe messages must be sent in text only format with MIME turned off. Email sent from web based email such as Hotmail and AOL are generally NOT in text format
Re: [RCSE] Re: Redundancy for Scale (Two or more batteries)
I suppose you could say that two batteries in parallel are as good as whatever battery's the oldest / weakest. There's no point in doing this unless the batteries are identical (age as well as characteristics) and then all you're really doing is making one big battery -- that is, without some kind of isolation circuit you're not getting redundancy. (You're actually increasing the chances of failure because you're introducing extra places where things can go wrong.) So Bill Swingle's right...don't waste your time, just use one relatively new, good quality battery. The world won't end if you use two smaller ones but you won't gain anything except a false sense of security. I wouldn't obsess over everything being brand new, though. Electronics failure rates are usually described as a 'bathtub' curve -- new stuff has a higher probability of failing for a short time, then everything's stable for quite a long time and finally things start to fail as they get to the end of their life. This curve is messed up these days because modern electronics is so well made that infant mortality is rare for consumer products but the principle is still valid. So I'd take a battery that's been used successfully over a couple of months over a new one any time. (I'd be wary of switches, though -- the ones that you buy are pretty reliable (they actually have two sets of contacts) but they're still quite cheaply made. Its easy to buy good quality switches.) Martin Usher RCSE-List facilities provided by Model Airplane News. Send subscribe and unsubscribe requests to [EMAIL PROTECTED] Please note that subscribe and unsubscribe messages must be sent in text only format with MIME turned off. Email sent from web based email such as Hotmail and AOL are generally NOT in text format
Re: [RCSE] Re: Redundancy for Scale
Simon, If you're saying that a new battery may possibly fail. It is of course possible. But testing before installation does help that significantly. Yes, replacing things regularly is worthy of concern but more because the connectors can fail. But their typical life cycle is long enough that I thought a one or two year cycle wasn't concerning. Just test before installation. I suggested it because the one item that is expected to degrade over time is the battery and will eventually need replacement. I was only suggesting a replacement before failure. The user picks the time he's comfortable with. Daryl, mentioned switch failure but since it doesn't cycle during flight I didn't consider it significant. All I've had fail did so on the ground while I cycled them. Naturally, it's tough to disagree with Daryl given his credentials. I don't do so lightly. Bill Swingle Janesville, CA RCSE-List facilities provided by Model Airplane News. Send subscribe and unsubscribe requests to [EMAIL PROTECTED] Please note that subscribe and unsubscribe messages must be sent in text only format with MIME turned off. Email sent from web based email such as Hotmail and AOL are generally NOT in text format
Re: [RCSE] Re: Redundancy for Scale
Hi Bill, I oversee our production facilities which build GPS/DGPS precision guidance systems (in the thousands - http://www.hemispheregps.com/main/) for the agricultural industry, we observe daily lots of interesting and unique failures of new componentry/systems. However at the hobby level that failure rate is higher, especially with battery packs. I agree with you, and to be more succinct; - Replacement of serviceable componentry, especially battery packs, introduces a potential failure where one did not exist before. However those who regularly replace packs for the sake of it, re-introduce (each time) that potential for failure. Some more tidbits: Due to differing rates of PWR consumption in part to varying series-resistnce when employing dual packs, one pack will be more discharged than the other. This is normal. In large scale sailplanes dual packs offset lead used to balance, and the advantages of dual packs (as Bill points out) have been employed in IMAC-style aerobatic aircraft for years. There are plenty of stories where an aircraft was safely landed, or the pilot landed only to discover one PWR supply had failed in one form or another. As was pointed to previously, Red's Battery Clinic has an accurate and readable section on how to set them up...and just as importantly points out the old wive's tales and misinformation that permeates throughout the hobby/sport regarding a worthy form of PWR reduncancy. Quoting Bill Swingle [EMAIL PROTECTED]: Simon, If you're saying that a new battery may possibly fail. It is of course possible. But testing before installation does help that significantly. Yes, replacing things regularly is worthy of concern but more because the connectors can fail. But their typical life cycle is long enough that I thought a one or two year cycle wasn't concerning. Just test before installation. I suggested it because the one item that is expected to degrade over time is the battery and will eventually need replacement. I was only suggesting a replacement before failure. The user picks the time he's comfortable with. Daryl, mentioned switch failure but since it doesn't cycle during flight I didn't consider it significant. All I've had fail did so on the ground while I cycled them. Naturally, it's tough to disagree with Daryl given his credentials. I don't do so lightly. Bill Swingle Janesville, CA RCSE-List facilities provided by Model Airplane News. Send subscribe and unsubscribe requests to [EMAIL PROTECTED] Please note that subscribe and unsubscribe messages must be sent in text only format with MIME turned off. Email sent from web based email such as Hotmail and AOL are generally NOT in text format Simon Van Leeuwen PnP Systems - The E-Harness of Choice Radius Systems Cogito Ergo Zoom RCSE-List facilities provided by Model Airplane News. Send subscribe and unsubscribe requests to [EMAIL PROTECTED] Please note that subscribe and unsubscribe messages must be sent in text only format with MIME turned off. Email sent from web based email such as Hotmail and AOL are generally NOT in text format
Re: [RCSE] Re: Redundancy for Scale (Two or more batteries)
I have a 9000 mah battery in my Duo Discus. Would it be better to have two 2400 mah batteries in parallel (same weight) or just stick with the 9000? I have an automatic redundancy switch in one of my other scale planes, but it only switches if the primary pack goes bad. I have a 3000 mah primary and a 2400 mah secondary. Have flown 10+ hours and it never switched over. Tested (static on the ground) the switch with a 150 mah pack and it switched over in 66 min to the secondary. Tom - Original Message - From: Martin Usher [EMAIL PROTECTED] To: soaring@airage.com Sent: Monday, March 06, 2006 12:23 PM Subject: Re: [RCSE] Re: Redundancy for Scale (Two or more batteries) I suppose you could say that two batteries in parallel are as good as whatever battery's the oldest / weakest. There's no point in doing this unless the batteries are identical (age as well as characteristics) and then all you're really doing is making one big battery -- that is, without some kind of isolation circuit you're not getting redundancy. (You're actually increasing the chances of failure because you're introducing extra places where things can go wrong.) So Bill Swingle's right...don't waste your time, just use one relatively new, good quality battery. The world won't end if you use two smaller ones but you won't gain anything except a false sense of security. I wouldn't obsess over everything being brand new, though. Electronics failure rates are usually described as a 'bathtub' curve -- new stuff has a higher probability of failing for a short time, then everything's stable for quite a long time and finally things start to fail as they get to the end of their life. This curve is messed up these days because modern electronics is so well made that infant mortality is rare for consumer products but the principle is still valid. So I'd take a battery that's been used successfully over a couple of months over a new one any time. (I'd be wary of switches, though -- the ones that you buy are pretty reliable (they actually have two sets of contacts) but they're still quite cheaply made. Its easy to buy good quality switches.) Martin Usher RCSE-List facilities provided by Model Airplane News. Send subscribe and unsubscribe requests to [EMAIL PROTECTED] Please note that subscribe and unsubscribe messages must be sent in text only format with MIME turned off. Email sent from web based email such as Hotmail and AOL are generally NOT in text format RCSE-List facilities provided by Model Airplane News. Send subscribe and unsubscribe requests to [EMAIL PROTECTED] Please note that subscribe and unsubscribe messages must be sent in text only format with MIME turned off. Email sent from web based email such as Hotmail and AOL are generally NOT in text format
Re: [RCSE] Re: Redundancy for Scale (Two or more batteries)
Stick with the 9000mA pack if you like, but yes two 2400mA packs would be better than the single large pack. Redundancy switches work, but in themselve represent significantly more points of failure than second pack and switch. Your scenario with the 3000/2400 packs shows that the 3000mA pack exceeds your longest flight, but do you know by how much? How much cpacity was left would have been interesting to note. This in turn helps you determien the mA/Hr consumed by that aircraft's electrical system. Quoting inventorforhire [EMAIL PROTECTED]: I have a 9000 mah battery in my Duo Discus. Would it be better to have two 2400 mah batteries in parallel (same weight) or just stick with the 9000? I have an automatic redundancy switch in one of my other scale planes, but it only switches if the primary pack goes bad. I have a 3000 mah primary and a 2400 mah secondary. Have flown 10+ hours and it never switched over. Tested (static on the ground) the switch with a 150 mah pack and it switched over in 66 min to the secondary. Tom Simon Van Leeuwen PnP Systems - The E-Harness of Choice Radius Systems Cogito Ergo Zoom RCSE-List facilities provided by Model Airplane News. Send subscribe and unsubscribe requests to [EMAIL PROTECTED] Please note that subscribe and unsubscribe messages must be sent in text only format with MIME turned off. Email sent from web based email such as Hotmail and AOL are generally NOT in text format
