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Would it be possible to create an online charging system (no power loss from the load's point of view) using a NiMH battery and a peak-detection charger , more specifically the Tenergy 01005? My concern here is that the load on the battery will keep the peak detection from working, leading to an overcharged battery.-
If not, what would be the best way to create such a charging system? My current method uses a relay with the NC line going to the charger and the NO line going to the load, which is suboptimal as it has a number of important electronics running from USB power. As these devices sometimes draw a significant amount of power, they can trip the polyfuse in the USB bus and thus cause problems.
Hi,Quote from: rbtying on February 10, 2012, 04:55:53 PMWould it be possible to create an online charging system (no power loss from the load's point of view) using a NiMH battery and a peak-detection charger , more specifically the Tenergy 01005? My concern here is that the load on the battery will keep the peak detection from working, leading to an overcharged battery.Do you by "online" mean charging with a load connected?If so, you're right thinking that the load may fool a peak detector, but my guess would rather be too early termination, at least if the load varies/switches on-off at random times.
Would it be possible to create an online charging system (no power loss from the load's point of view) using a NiMH battery and a peak-detection charger , more specifically the Tenergy 01005? My concern here is that the load on the battery will keep the peak detection from working, leading to an overcharged battery.
Quote from: rbtying on February 10, 2012, 04:55:53 PMIf not, what would be the best way to create such a charging system? My current method uses a relay with the NC line going to the charger and the NO line going to the load, which is suboptimal as it has a number of important electronics running from USB power. As these devices sometimes draw a significant amount of power, they can trip the polyfuse in the USB bus and thus cause problems.Not qute sure what you mean by the relay setup and all, but if you want to get more current than your USB controller can supply, you could get a powered hub - or why not a separate power source?If you want to make a charger that can charge NiMH's while under load, use temperature and terminal voltage as EoC detectors.
Yes, I meant charging with a load connected. Do you think the charger would begin charging again if the voltage dropped to a sufficiently low level? That is, if it terminated charging because the load turned on, and then the load drained the battery, is it likely to need power cycling before it will begin charging?
I want to get more current, yes, but currently the only external power source I have is the battery that would be charging; thus, I'm looking for a way to charge it while leaving it connected to the USB hub.
With regards to making such a charger, are there any relatively simple ways to do so? I don't want to play with AC if I can avoid it, so if you know of an existing product that does EoC with dT/dt, that would be best.
Interestingly enough, my Tenergy charger does have a temperature probe, but the advertising implies that it uses peak detection instead...
Quote from: rbtying on February 11, 2012, 12:01:18 AMYes, I meant charging with a load connected. Do you think the charger would begin charging again if the voltage dropped to a sufficiently low level? That is, if it terminated charging because the load turned on, and then the load drained the battery, is it likely to need power cycling before it will begin charging?I don't know your specific charger so I cannot tell - but it is fairly easy to find out
Quote from: rbtying on February 11, 2012, 12:01:18 AMI want to get more current, yes, but currently the only external power source I have is the battery that would be charging; thus, I'm looking for a way to charge it while leaving it connected to the USB hub.Why do you have a battery connected to a USB hub at all?
Quote from: rbtying on February 11, 2012, 12:01:18 AMWith regards to making such a charger, are there any relatively simple ways to do so? I don't want to play with AC if I can avoid it, so if you know of an existing product that does EoC with dT/dt, that would be best. How many of the NiMH cells are in series?Do you have an adapter of a suitable voltage, perhaps from some discarded piece of equipment?If so, what voltage and current?
Quote from: rbtying on February 11, 2012, 12:01:18 AMInterestingly enough, my Tenergy charger does have a temperature probe, but the advertising implies that it uses peak detection instead...The temperature is used as a safeguard against the odd incidents where a semi-bad battery is too weak to give a clear dV/dT indication.
It's a 9 cell (10.8v) battery, so I imagine that I would be able to use a 12v/1A power adapter to charge it? Anything else I have would be too high of a voltage (laptop power supplies at 19v) or too low (9v)
NiMH cells need to be charged to 1.40V to 1.45V (charge termination voltage), so a 9 cell battery needs to be charged to 12.6V-13.05V and you need at least half a volt over that from the charger.You could use a booster circuit to use either the 9V or the 12V supply, but if it's OK to use your laptop charger, it wouldn't be hard to make a current limited constant voltage (taper charger) circuit for that.What is the capacity rating of your battery?You should still use the dV/dT charger for charging every now and then (perhaps once a week or once a month) to keep the battery in mint condition.
Do you have any resources/schematics on how to make a taper charger? If so, that would be extremely helpful.