RE: How to convert an ATX power supply to rc use
Not sure about your specific charger, but many have a built-in voltmeter that will show you the voltage of the power supply feeding it. If so, you don't really need one on the supply itself unless you want it for other hookups. But to answer your question: A voltmeter is wired in parallel with the 12v output wires. So take the positive lead of the meter and hook it to the +12v output line. Then, take the negative lead of the meter and hook it to the ground output. It looks sort of like this: [code] POWERSUPPLY(+) ======== OUTPUT_CONNECTOR(+) ===== (+) VOLT_METER POWERSUPPLY(-) ======== OUTPUT_CONNECTOR(-) ===== (-) [/code] An amp meter needs to be wired [b][i]in series[/i][/b] with the output. [b]This is very important![/b] This means you have to "break" the positive connection from the power supply wire to the output connector and insert the meter in series. Hard to explain, but it looks like this: [code] POWERSUPPLY(+) ===== (+)AMP_METER(-) ===== OUTPUT_CONNECTOR(+) POWERSUPPLY(-) =========================== OUTPUT_CONNECTOR(-) [/code] To wire both up at the same time, do this: [code] POWERSUPPLY(+) ===== (+)AMP_METER(-) ===== OUTPUT_CONNECTOR(+) ===== (+) VOLT_METER POWERSUPPLY(-) =========================== OUTPUT_CONNECTOR(-) ===== (-) [/code]
Posted on: 8/1/2012 10:14 AM by Author "bgosselin" in the forum "Batteries & Chargers"
http://www.rcuniverse.com/forum/fb.asp?m=11177308

RE: How to convert an ATX power supply to rc use
Yeah, that's possible too. Either way, I wasn't trying to pick on Red or anything, just trying to prevent SirNoob from doing something incorrectly. Hopefully, he reposts the actual value. What a difference a simple 0 can make! :)
Posted on: 7/3/2012 9:04 AM by Author "bgosselin" in the forum "Batteries & Chargers"
http://www.rcuniverse.com/forum/fb.asp?m=11141290

RE: How to convert an ATX power supply to rc use
[quote]ORIGINAL: Red Scholefield Connect them all in parallel. This should give you a better output voltage. Collectively they will draw about 2 amps which is 10 watts total. [/quote] That was probably a typo (?), but hooking all four 1ohm resistors in [i]parallel[/i] will equate to [b]0.25ohm[/b], which will draw [b]20A[/b] from the 5v line and generate [b]100w[/b]. Personally, I'd start by putting just two or three of those 1ohm resistors in [i]series[/i] (2ohm or 3ohm total). The more current you draw from the 5v line, the more stable the 12v line will be, but you are wasting more power as heat. [EDIT] Now that I re-read it Red, you probably thought he had four [b]10[/b] ohm resistors...
Posted on: 7/3/2012 7:38 AM by Author "bgosselin" in the forum "Batteries & Chargers"
http://www.rcuniverse.com/forum/fb.asp?m=11141161

RE: Adjustable voltage 18V PSU
The only adjustable PSU I've ever built was a linear type (large heavy mains transformer and multiple pass transistors for output regulation). For the current you want, a switching type would be far smaller/lighter. It would likely be cheaper and easier to just find a switching supply that has the voltage and current you need. Assuming your charger can handle 24v-28v, I would just get a couple of 12v server power supplies and put them in series for 24v.
Posted on: 6/25/2012 8:21 AM by Author "bgosselin" in the forum "Batteries & Chargers"
http://www.rcuniverse.com/forum/fb.asp?m=11130988

RE: Unique Charging Situation
[quote]ORIGINAL: t9dragon You are asking for problems.. Lipos should never be left unattended when charging. [/quote] I agree! If you want a more hassle-free setup, I'd use properly-sized Li-Ion's (or A123 cells) that aren't as prone to issues, similar to what power tools use. Really, all Lixx cells need is constant-current charge up to the termination voltage (4.2v for lipo, 3.6v for A123). After that, it should switch to constant-voltage - but because you don't get much charge at this stage, you could simply stop the charge. You should also use a BMS circuit so the cells are balanced, and so the voltage on any single cell will dip too low or rise too high; similar to what laptops use. Something like this: http://www.all-battery.com/pcb4SLi-ion15-20A-32128.aspx
Posted on: 6/20/2012 10:57 AM by Author "bgosselin" in the forum "Batteries & Chargers"
http://www.rcuniverse.com/forum/fb.asp?m=11125380

RE: could some body explain this to me please?
That's a pretty large variance between actual mAh and rated mAh. I would suspect that either the battery is rated very conservatively, the discharge terminal voltage is really low, or the charger is miscalculating somehow.
Posted on: 6/14/2012 9:18 AM by Author "bgosselin" in the forum "Batteries & Chargers"
http://www.rcuniverse.com/forum/fb.asp?m=11118025

RE: could some body explain this to me please?
Also, I would pay more attention to the amount of mAh taken out during[i] discharge[/i] and what the termination voltage is. During the [i]charge[/i] cycle, the cell heats up near the end and most of that bit of charge is not being stored in the battery but dissipated as heat. So a good percentage of the mAh the charger claims is being put back in the battery at the end of the charge is not really going into the battery after all.
Posted on: 6/14/2012 9:04 AM by Author "bgosselin" in the forum "Batteries & Chargers"
http://www.rcuniverse.com/forum/fb.asp?m=11118009

RE: Hot LiPo balancer?
Yeah, like chuckk2 said, the balancer is discharging the high cell(s) and that is creating heat. IIRC, that balancer (I have one) balances at 150mA, which equates to around 0.6w of heat dissipation [i]per cell[/i]. If one cell is being actively balanced (discharged), then it should be a little warm, but if multiple cells need balancing, heat can climb quick. Keep in mind that the balancer, since it isn't connected to the charger, doesn't "talk" to the charger to tell it to lower the charge rate, and so isn't truly 100% effective. If you are charging at 5A, any cell that is being balanced is effectively being charged at around 4.85A (5A charger rate minus 150mA balancer bleed current). At that high of a charge current, the balancer might not be able "keep up" with the charger to prevent an individual cell from exceeding the 4.2v limit. If the balancer is quite hot, it means it is working hard, so I would lower the charger's charge rate to allow the balancer to have an easier time to do its job; something like 1A. I have an older version of their balancer and I modded it a little to help with excessive heat by adding a heatsink to the bottom. Ideally, the sink should be attached directly to the heat-producing devices, but that wasn't feasible. So I found a spot on the back that had no exposed components, traces, or solder tabs and attached it there: [image]http://scriptasylum.com/forumpics/balancer_mod.jpg[/image]
Posted on: 6/14/2012 7:26 AM by Author "bgosselin" in the forum "Batteries & Chargers"
http://www.rcuniverse.com/forum/fb.asp?m=11117900

RE: Lipo Fires Are Real![Fantastic Advice!] Can I ask for further help?
@raptorboy: While the batteries in laptops, phones, cameras, etc [i]are[/i] lithium, your analogy is not quite apples-to-apples. There are some substantial differences between batteries for these devices and those for R/C use: 1) Batteries for lower-powered devices (like phones and cameras) are mostly single-cell (1s) so no balancing is/can be done and so the charge circuits are much simpler. Multi-cell packs (like laptops) are made so each cell has a built-in monitoring circuit (BMS) that shuts off main current flow if temperature is exceeded or if any cell is over charged/discharged. 2) Cells are chosen specifically for the device to make sure they can easily handle the load. Not like R/Cs where people routinely stuff batteries of all types and sizes in their equipment which are not up to the task. 3) The charge circuits are integrated into the device so no chance for a erroneous cell count/amperage entry. Of course, someone could shoe-horn the wrong adapter that has the wrong output voltage/polarity, but sometimes you just can't account for all levels of stupidity. 4) Charge rates are usually lower than 1C. 5) Discharge C rates are far lower than just about any R/C I can think of. And, despite all those manufacturer precautions, there still have been cases of battery issues in those devices, like pushinoldrc said.
Posted on: 5/31/2012 2:23 PM by Author "bgosselin" in the forum "Batteries & Chargers"
http://www.rcuniverse.com/forum/fb.asp?m=11101587

RE: Lipo Fires Are Real![Fantastic Advice!] Can I ask for further help?
As said, you are good to go as long as they are being charged correctly; proper cell count and amperage settings, and assuming the charger is a quality unit and doesn't malfunction. And ALWAYS balance-charge! Most chargers today have built-in balancers to ensure each cell is not being overcharged and will shut off the charger if something is wrong. If you don't use the balancer function, the charger has no way of knowing what each cell is at, only the overall pack voltage. Even though a 2s pack is at 8.4v overall (which is fine if both cells are equal), one cell could be at 3.5v and the other could be at 4.9v. A balancer would cut off the charger once the latter cell got to 4.2v. A built-in balancer is better because it actively "talks" to the charger. Most external balancers do not communicate with the charger or interrupt the main charge current, so even though it knows something is wrong, it has no way of communicating that to the charger. Charge location can be anywhere, but to provide protection in the unlikely event of a flame out, charge them in some sort of fire-proof container. The container should be large enough to contain the lipo (obviously), but also large enough to contain the fire itself. Not much good if the flames reach something flammable outside/above the container! The container should also have a lid to help contain any flames, but NOT be airtight - you don't want the pressure from rapidly expanding gasses to blow it apart. I personally like to use a stone/ceramic style container (pretty much anything fire-proof that doesn't pass heat well). A metal container could accidentally short out a pack (especially if there are any breaks in the pack's wire insulation) and if a fire does happen, the container itself could get hot enough to ignite whatever it is sitting on if it is flammable. I also like to [b]store[/b] lipos similarly. Lipos have been known to puff just sitting there not connected to anything. I've never heard of a lipo puffing enough to start a fire this way, but I suppose it could happen. If you plan to not run your packs for a day or more, it's best to keep them at around half-charge or a little less. Also, be aware that there is a LOT of smoke generated from a flaming lipo (how'd they put all that smoke in such a little package, lol) and that smoke is not healthy to breathe, so a nearby window with a handy fan to suck out the smoke would be a good idea if charging anywhere inside. Of course, all this is IF the lipo flames up, but as long as the charger is sound and you are following proper procedures, there shouldn't be any issues. But it's nice to be prepared for the worst-case scenario. I like the quote "Expect the worst and all surprises will be good ones". I don't think you need to go overboard and use bomb-shelter to charge/store lipos, but a little care can go a long way to mitigate any chances for disaster.
Posted on: 5/31/2012 8:50 AM by Author "bgosselin" in the forum "Batteries & Chargers"
http://www.rcuniverse.com/forum/fb.asp?m=11101228

RE: 500mah to 180mah, which resistor?
Personally, the use of a simple resistor can be tricky to figure once you try to take into account existing output impedance, voltages, etc. The way to go IMO for that small of a current is to use a LM317T linear regulator (available at pretty much any electronic components shop like Radio Shack) configured for constant current (easy to do with one resistor: 7ohms @ 1/2 watt for 180mA). This should work if the charger is just a "wall-wart" type of device and the loaded output voltage is high enough to charge the battery AND compensate for the regulator dropout (~2v) and program (1.25v) voltages. But, if this is a true charger with peak-detect and so on, any added components (even a simple resistor inline) may confuse the logic circuits. But, if this is for a lithium battery, you also need something that would terminate the charge once cell voltage reaches 4.2v/cell. Even if this is for NiXX, you'd want a circuit that would either detect delta peak (requires logic circuits) or terminate using temperature (easier method that only requires a thermistor and a few other support components).
Posted on: 5/15/2012 8:48 AM by Author "bgosselin" in the forum "Batteries & Chargers"
http://www.rcuniverse.com/forum/fb.asp?m=11081546

RE: Ideal Rx battery for Bird of Time?
[quote]ORIGINAL: Goldenduff A BEC would an unnecessary risk as it is extra connections and components? [/quote] I suppose, but the same thing can be said for any other BEC on the market (including ones built into ESCs). And generally, those fail because current draw is high. I have only had one BEC fail on me ever, and that again was from a stalled hi-torque servo. Anyway, it was just an idea. Not sure if weight was the OP's primary concern or what.
Posted on: 5/10/2012 1:32 PM by Author "bgosselin" in the forum "Batteries & Chargers"
http://www.rcuniverse.com/forum/fb.asp?m=11076107

RE: Ideal Rx battery for Bird of Time?
4 of those LSD cells in series would give you 4.8v nominal at 1500mAh. Not sure where you figured 8000mAh? Hmm, I would think going to a lipo with a BEC would be a good choice too. I would think the added weight of the BEC would be more than offset by the lighter battery type. A 2s 2000mAh lipo pack and small BEC has got to be lighter than 4 NiXX cells? The [link=http://www.dimensionengineering.com/products/parkbec]Dimension Engineering Park BEC[/link] is very small/light. Yeah, it would cost a bit more, but not sure how much is too much for you.
Posted on: 5/10/2012 12:59 PM by Author "bgosselin" in the forum "Batteries & Chargers"
http://www.rcuniverse.com/forum/fb.asp?m=11076071

RE: Wire a LiPo into a Field Amp for Music?
I wouldn't use a SERIES adapter for dual 3s packs (would be 22.2v), but rather a PARALLEL adapter. I bet that's what Goldenduff meant though...
Posted on: 5/1/2012 12:06 PM by Author "bgosselin" in the forum "Batteries & Chargers"
http://www.rcuniverse.com/forum/fb.asp?m=11064234

RE: Wire a LiPo into a Field Amp for Music?
"Timing the run" doesn't work so well with audio because current draw (and therefore runtime) varies tremendously with type of audio content (lots of bass vs little), overall volume, amount of clipping (distortion). Even though the input of that amp is rated 2A, don't be surprised to see average values around 1A, and peaks over 2A (again depending on content, volume, etc). Personally that LVA (Low Voltage Alarm) would be the best bet to make sure you don't overdischarge the lipo - you just have to make sure you can hear it over the audio. You could mod the LVA and replace the speaker with a hi-brightness LED/resistor combo so you can see when the LVA activates. This would take a little experimenting. As to the original question; yes, you can easily make an adapter that goes from Deans to whatever plug the amp uses. [b]Just make sure you have the right polarity at the amp's plug![/b] Incorrect polarity will surely blow the amp. The plug for that specific amp requires the tip to be positive (the "tip" is the inner hole and is +12, the outer sleeve is the ground). Use a voltmeter once you finish the adapter to make sure it's wired right. Another thing to consider is the lipo voltage. Fresh charge on a 3s pack is 12.6v, and nominal is 11.1v, but some amps shut down below 10-11v. One more thing; if you use this outside, you [i]may[/i] need a bit more power. A house/room has walls to contain/reflect sound so it sounds louder. Outside, the same volume will not sound as loud and you may find yourself turning it up louder to compensate, and if you go too loud, the amp starts to clip which sounds horrible in these "digital" amps.
Posted on: 4/27/2012 8:20 AM by Author "bgosselin" in the forum "Batteries & Chargers"
http://www.rcuniverse.com/forum/fb.asp?m=11058973

RE: Anyone use this charger?
I don't use that charger, but the link should be: http://www.hobbyking.com/hobbycity/store/__6478__IMAX_B6_AC_Charger_Discharger_1_6_Cells
Posted on: 4/25/2012 3:08 PM by Author "bgosselin" in the forum "Batteries & Chargers"
http://www.rcuniverse.com/forum/fb.asp?m=11056631

RE: Hyperion 0606i charging NiMH problems
Yeah, I guess if I wasn't so lazy to look I would've seen that. :) But, you can still test it by not using the built-in supply and hooking up the 12v leads to a car battery or 12v power supply.
Posted on: 4/25/2012 9:53 AM by Author "bgosselin" in the forum "Batteries & Chargers"
http://www.rcuniverse.com/forum/fb.asp?m=11056224

RE: Hyperion 0606i charging NiMH problems
Hmm, that is odd. I have two Hyperion chargers (old EOS7i and a newer EOS 0615 duo 3+) and switching display screens doesn't affect the charge process on either of them. One other thing to check is your power supply. If the 12v DC supply is "noisy" (meaning, it has excessive AC ripple), that could cause random weirdness in the charger's logic circuits - it does contain a "computer" of sorts after all. Either check the supply output with a meter set to A/C to see how much noise is present, or just try a different 12v supply. Since you are charging at such low rates, even a small 2-3A 12v supply would be enough for this test.
Posted on: 4/25/2012 8:23 AM by Author "bgosselin" in the forum "Batteries & Chargers"
http://www.rcuniverse.com/forum/fb.asp?m=11056091

RE: Hyperion 0606i charging NiMH problems
Probably because the NiMHs he's working with are transmitter/receiver packs. Depending on the cell brand/quality, certain batteries respond better to lower charge/discharge rates. For instance, I have some Turnigy LSD (low self-discharge) AA batteries rated for something like 2300mAh. But I monitored the cells at various charge/discharge rates and found that a ~0.2C charge and ~0.5C discharge rates yield the best performance and most usable capacity with little to no heating. Or maybe he's not in a hurry. :)
Posted on: 4/25/2012 7:42 AM by Author "bgosselin" in the forum "Batteries & Chargers"
http://www.rcuniverse.com/forum/fb.asp?m=11056042

RE: Hyperion 0606i charging NiMH problems
You could try increasing the delta peak sensitivity to something above 3mV. When charging at that low current, I would go by temperature to determine a good delta peak setting. At the end of the charge, the cells should be a little warm; not hot and not cool. If hot, the delta setting is too high. If cool, the delta setting is too low. So, it might take a little trial and error to get it set right.
Posted on: 4/24/2012 12:10 PM by Author "bgosselin" in the forum "Batteries & Chargers"
http://www.rcuniverse.com/forum/fb.asp?m=11055058

RE: RC Car Jerking.. Is this normal ?
Yeah, most chargers require a 12v DC power supply. They do this so people can run them off their 12v car battery when at the field. So, if you want to use it at home, you have to come up with a 12v solution. The charger you got is only 50w, so you only need a supply that will deliver around 6A @ 12v. Even then, 6A is a bit much to ask for a normal wall-wart power supply. Either convert a PC power supply, or get a retail one.
Posted on: 4/11/2012 2:09 PM by Author "bgosselin" in the forum "Batteries & Chargers"
http://www.rcuniverse.com/forum/fb.asp?m=11037976

RE: RC Car Jerking.. Is this normal ?
I agree with it being the battery's fault. The voltage is likely sagging under load and is getting too low to move the truck right. Until you get a new battery, make sure you have any LVC setting shut off.
Posted on: 4/11/2012 1:35 PM by Author "bgosselin" in the forum "Batteries & Chargers"
http://www.rcuniverse.com/forum/fb.asp?m=11037921

RE: How to convert an ATX power supply to rc use
[quote]ORIGINAL: Andrew I must confess that I'm running out of options here; maybe bgosselin has a suggestion that can help out. [/quote] I'm out of ideas as well...
Posted on: 4/11/2012 6:35 AM by Author "bgosselin" in the forum "Batteries & Chargers"
http://www.rcuniverse.com/forum/fb.asp?m=11037375

RE: How to convert an ATX power supply to rc use
Thanks for the pics. Couple points I want to mention though: 1) The two heatsinks doesn't necessarily mean two rails. Actually usually one heatsink is for the AC mains side switching section (FETs, bridge rectifier, etc), the other heatsink (closer to the output wires) is for the output FETs and associated components. 2) To really see how many 12v rails there are, you'd have to pull out the PCB and follow the traces. Even though there are 3 sections, they could simply be tied together via copper traces underneath. However, there are three coils/caps per output wire, but that could just be paralleled/split to help handle the high currents without using larger (and more expensive) components. Again, a peek at the traces (especially before the coils) would tell you more. 3) All the grounds are the same point. Typically, I use the same amount of grounds as the yellow wires. So, if I bundle 6 yellows together, I'd also bundle 6 blacks together. Since all grounds go to the same point, it doesn't matter which ones you use - there are no separate 5v, 3.3v, and 12v grounds. It is odd that the PCB has three 12v outputs labeled, but specifies only two on the outer case label. I probably should go look at the ATX spec, but I assume the red/brown connection consists of the 5v line and the 5v sense wire tied together?
Posted on: 4/9/2012 7:35 PM by Author "bgosselin" in the forum "Batteries & Chargers"
http://www.rcuniverse.com/forum/fb.asp?m=11035357

RE: How to convert an ATX power supply to rc use
[quote]ORIGINAL: ImpalaPolicePack im charging 5s and 6s 5000mah packs at 7amps. i know its not 1c but i dont care if the packs does not last as long since they are cheap to buy. i tought that i was only pulling 7amps, why is it more because of a 5s pack ? anyway, like you said, the ps should handle it... [/quote] Ready for a bit of math? Charging a 5s pack at 7A requires up to 147w of power (4.2v/cell * 5cells * 7amps). Since the charger is not 100% efficient (typically around 80%), add in another 20% of power for 176.4w. That is the power the charger will pull from the power supply. Since the PS outputs 12v, the power supply will need to supply 14.7A (176.4w/12v). Charging a 6s pack at 7A requires up to 176.4w of power (4.2v/cell * 6cells * 7amps). Again, to account for efficiency losses, add in another 20% for 211.68w. At 12v PS output, it has to supply 17.64A of current. I say "up to X watts" because the most power a charger will have to output is [i]just before[/i] the battery reaches 4.2v per cell and so is still in the CC phase of the charge. Before and after that point, the actual power required is a little less, but we always want to use worst-case to figure things like this.
Posted on: 4/9/2012 1:19 PM by Author "bgosselin" in the forum "Batteries & Chargers"
http://www.rcuniverse.com/forum/fb.asp?m=11034829

RE: How to convert an ATX power supply to rc use
You're charging what size pack at 7A? 2s, 3s, 6s, 8s? Because if you are charging a 6s pack @ 7A, that's around 16A being drawn from the PS. It still should be able to handle that though.
Posted on: 4/9/2012 8:05 AM by Author "bgosselin" in the forum "Batteries & Chargers"
http://www.rcuniverse.com/forum/fb.asp?m=11034367

RE: How to convert an ATX power supply to rc use
What are the current ratings for each of the 12v rails? Odd that it says two rails, but there are 3 wire labels (A, B, C). Anyway, try hooking the charger to just one of the 12v wire sets by itself, preferably the highest current rated one (multiple 12v rails usually have slightly different current ratings).
Posted on: 4/5/2012 8:15 AM by Author "bgosselin" in the forum "Batteries & Chargers"
http://www.rcuniverse.com/forum/fb.asp?m=11029276

RE: How to convert an ATX power supply to rc use
That is rather odd. You said this is a thermaltake 500w PS, but does it have a single 12v rail or multiple 12v rails? One of my converted PS units had two 12v rails, and when I paralleled them, they seemed to fight each other and got something like what you describe. I had to use each one individually.
Posted on: 4/5/2012 6:45 AM by Author "bgosselin" in the forum "Batteries & Chargers"
http://www.rcuniverse.com/forum/fb.asp?m=11029161

RE: How to convert an ATX power supply to rc use
[quote]ORIGINAL: Andrew On a different note, I had wondered how responsive the current standard ATX supply might be to perceived changes in voltage levels on the 3.3v rail, so I dropped a pot inline on the remote sense line running to the 3.3v connector pin. On the supply I used, a 350W SPI, it had essentially no effect on the 12v or 5v output. Unfortunate, since it would have provided an easy way to fine tune output when the PSU was under load. [/quote] I've had a couple supplies with a separate sense wire (old Antec true-power IIRC) for each rail. The pot trick does work if the 12v line has the pot, but seems to be hit or miss if only the other rails have the sense lead. I've since given up on ATX supply conversion in favor of a server supply. The single 12v high current rail is nice, they are usually very robustly built, can usually be tweaked if they have some kind of sense terminal, and you can get them on eBay for ~$25 if you're lucky. I've been using a few of those HP 47A 12v supplies lately and they work great with VERY little voltage sag when drawing high currents. I've boosted the output to ~13.2v - any higher and the supply just shuts down. Soldered a couple banana jacks to the terminals and they're good to go!
Posted on: 4/4/2012 10:13 AM by Author "bgosselin" in the forum "Batteries & Chargers"
http://www.rcuniverse.com/forum/fb.asp?m=11028084

RE: How to convert an ATX power supply to rc use
[quote]ORIGINAL: Andrew Agreed. While many of the newer supplies will latch on without a pre-load, the load resistors significantly improve the supply's performance and reduce voltage drop under load. [/quote] Honestly, today's PCs put wayyy more stress on the 12v line than any of the others, so you'd think designers would put the feedback/regulation circuit on that rail instead of the less-used 5v line. I wonder when PC power supplies will be like server supplies where there is only one rail (12v) to worry about. That will make things much easier.
Posted on: 4/4/2012 7:04 AM by Author "bgosselin" in the forum "Batteries & Chargers"
http://www.rcuniverse.com/forum/fb.asp?m=11027867