My ancient window opener motor is powered by three of the subject rechargea ble batteries. The circuit includes a trickle current of about 35 mA but I ?m still finding it necessary to recharge the batteries every few w eeks. To ensure I always have a replacement set ready I plan a little circu it to cycle through: charge (say the recommended 300 mA for 16 hours), cut the supply, wait for N days, reapply the supply...repeating until needed. I s that a sensible approach? If so, what would be a good value for N?
Or could I achieve this more simply by increasing the trickle charge? The b atteries use about 4A two or three times a day on average, taking about 5 s ecs to open or close the heavy curtains with the ex-screwdriver motor.
I?m also been toying with the idea of dispensing with batteries and using a mains-derived power supply. But that would mean another largish ca se alongside the existing compact one. And presumably large heat sinks and consequent nervousness when away.
On Wednesday, February 19, 2020 at 10:36:43 AM UTC-5, snipped-for-privacy@gmail.com wr ote:
eable batteries. The circuit includes a trickle current of about 35 mA but I?m still finding it necessary to recharge the batteries every few weeks. To ensure I always have a replacement set ready I plan a little circ uit to cycle through: charge (say the recommended 300 mA for 16 hours), cut the supply, wait for N days, reapply the supply...repeating until needed. Is that a sensible approach? If so, what would be a good value for N?
Batteries are charged when they are low on power and the charging stops whe n topped off. This usually requires measurements. It would be hard to do using timers for both the charge time and the time between charges unless y ou know exactly the power consumed. Even then eventually they would either be overcharged or under charged.
batteries use about 4A two or three times a day on average, taking about 5 secs to open or close the heavy curtains with the ex-screwdriver motor.
I don't know that it is ok to trickle charge NiMH batteries. There are man y web pages on this. What do they say?
nd using a mains-derived power supply. But that would mean another largish case alongside the existing compact one. And presumably large heat sinks an d consequent nervousness when away.
What power do you need?
Lead acid batteries can be trickle charged ok. Have you considered one of those?
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Rick C.
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On Wednesday, February 19, 2020 at 10:36:43 AM UTC-5, snipped-for-privacy@gmail.com wr ote:
eable batteries. The circuit includes a trickle current of about 35 mA but I?m still finding it necessary to recharge the batteries every few weeks. To ensure I always have a replacement set ready I plan a little circ uit to cycle through: charge (say the recommended 300 mA for 16 hours), cut the supply, wait for N days, reapply the supply...repeating until needed. Is that a sensible approach? If so, what would be a good value for N?
batteries use about 4A two or three times a day on average, taking about 5 secs to open or close the heavy curtains with the ex-screwdriver motor.
nd using a mains-derived power supply. But that would mean another largish case alongside the existing compact one. And presumably large heat sinks an d consequent nervousness when away.
Batteries are more complicated these days. Battery University is OK.
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(It says NiMH can be damaged by over charging.)
5V at 4A sounds like something a little wall wart could do.
Probably simplest for you to increase the charge current. If that's the route you choose, try ~70mA instead of 35mA. You want to keep the charge rate to about .05C Note that this is not optimal for the batteries, but seems the simplest approach.
The N days approach is possible, too, but picking the number N would be done by trial and error. The problem with charging NiMh is avoiding overcharge. (In your case, we already know the existing problem is undercharge.) If during the trial and error the batteries are overcharged, then the trial and error itself is harming and perhaps killing them. If you decide to use that approach, I'd try starting with every other day, charge at 300mA for 1 hour each charge cycle. Not enough charge? Try every day instead of every other. Still not enough? increase to 2 hours per day. And so forth.
Regarding using a mains powered supply, you can avoid the large heat sink issue by using a switching supply instead of a linear supply. That is likely more costly (around 10 pounds ?) than other approaches, depending on what you have on hand. But at least it avoids killing your NiMh's by improper charging. :-)
Thanks all, very helpful. Just raised the trickle charge to 50 mA for the present set, rated 2200 mAH. I'll pursue some of the other suggestions.
Searching didn't find any UK available 'wall warts' or 'AC adapters' capable of 4A at 5V,and anyway I favour retaining the present design if possible. It has worked well at times; I've just recalled an earlier discussion about *reducing* its speed!
A 6V lead acid would need voltage reduction and not confident it could supply 4A +.
I now have four sets (of three C-Type NiMh), bought over the last few years, so reluctant to buy yet another fresh set. What diagnostics would others apply to each set to establish a set's health', apart from trying it over a period of days?
Directly after charging, the set currently installed was showing 4.3 V unloaded. In the past that's usually been fine to get the '2.4 V' motor to do its job, but now needs supplementing with human effort.
Of course, the batteries may not be the cause, or the sole cause,.
Other things under consideration:
- The present motor must be at least 16 years old (I built the project in 2004), so I could try a new one of identical type I still have.
- Remove the curtains and look for potential 'sticking points'
- Make the regrettable assumption that all four sets are no longer up to the task and buy a new set of higher quality
argeable batteries. The circuit includes a trickle current of about 35 mA b ut I?m still finding it necessary to recharge the batteries every f ew weeks. To ensure I always have a replacement set ready I plan a little c ircuit to cycle through: charge (say the recommended 300 mA for 16 hours), cut the supply, wait for N days, reapply the supply...repeating until neede d. Is that a sensible approach? If so, what would be a good value for N?
The batteries use about 4A two or three times a day on average, taking abou t 5 secs to open or close the heavy curtains with the ex-screwdriver motor.
s and using a mains-derived power supply. But that would mean another largi sh case alongside the existing compact one. And presumably large heat sinks and consequent nervousness when away.
argeable batteries. The circuit includes a trickle current of about 35 mA b ut I?m still finding it necessary to recharge the batteries every f ew weeks. To ensure I always have a replacement set ready I plan a little c ircuit to cycle through: charge (say the recommended 300 mA for 16 hours), cut the supply, wait for N days, reapply the supply...repeating until neede d. Is that a sensible approach? If so, what would be a good value for N?
The batteries use about 4A two or three times a day on average, taking abou t 5 secs to open or close the heavy curtains with the ex-screwdriver motor.
s and using a mains-derived power supply. But that would mean another largi sh case alongside the existing compact one. And presumably large heat sinks and consequent nervousness when away.
A simple diode or two could provide the voltage reduction. I have no idea why you think a lead-acid battery can't supply the current. They are used to supply hundreds of amps to start car engines! Even a small one can be u sed as a booster to start a car.
When you say C-Type, do you mean C size?
What is the battery voltage when running? Batteries can develop high resis tance dropping the voltage under load.
Does the motor run ok when not connected to the curtain? Does the curtain work smoothly without the motor?
Four sets? You have four sets of batteries? For four windows?
You could reduce the size of your spindle giving the motor more leverage.
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Rick C.
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I stand corrected. That Swedish product Lasse referenced is a good example.
amazon.co.uk call them C 'types'. And yes, of course, they relate to the sizes.
Typically 3.7-3.8 V. I understand battery resistance.
Well, it spins fast and is hard to stop by hand! But I haven't rigorously tested its torque. Did you see this: "...I could try a new one of identical type I still have."
The only way to open/close the curtain is to do so awkwardly by rotating the spindle by finger power.
"I now have four sets (of three C-Type NiMh), bought over the last few years..." I obviously need at least TWO sets, to allow for usage while one set is being recharged. And the earlier ones naturally are no longer as effective. Also did you read this from my opening post: "My ancient window opener motor..." Singular.
I'd prefer to focus on restoring its previous (designed) performance. It was at one time swishing them open in about 1.5 s. Sure don't want to reduce its *current* slow speed. Did you read this: "It has worked well at times; I've just recalled an earlier discussion about *reducing* its speed!"
echargeable batteries. The circuit includes a trickle current of about 35 m A but I?m still finding it necessary to recharge the batteries ever y few weeks. To ensure I always have a replacement set ready I plan a littl e circuit to cycle through: charge (say the recommended 300 mA for 16 hours ), cut the supply, wait for N days, reapply the supply...repeating until ne eded. Is that a sensible approach? If so, what would be a good value for N?
e? The batteries use about 4A two or three times a day on average, taking a bout 5 secs to open or close the heavy curtains with the ex-screwdriver mot or.
ries and using a mains-derived power supply. But that would mean another la rgish case alongside the existing compact one. And presumably large heat si nks and consequent nervousness when away.
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ea why you think a lead-acid battery can't supply the current. They are us ed to supply hundreds of amps to start car engines! Even a small one can b e used as a booster to start a car.
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sistance dropping the voltage under load.
I don't know how easy it is to disengage and mechanism. This seems to be a home-brew rig and I would have provided a quick disconnect just for such t esting. Elsewhere you said you provided hand assist. Was that by pulling the curtain or pulling on the cord?
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Quoting earlier text is not useful for information. I didn't see anything that indicated you disconnect the batteries to charge. My phone does not n eed to disconnect the one battery to charge. That seems like an inordinate ly clumsy way to work. In fact, if you swap two sets of batteries, where i s the problem??? You should be able to charge faster in a conventional cha rger and always have a set ready to use by the time the set on the curtain runs down.
Yes, is that supposed to be a hint about the batteries? Can you decode it for me?
.
You seem to like to point out hints you've provided that I didn't pick up o n as to their full meaning. If the unit is running slowly because the batt eries or motor are now insufficient to the task, either because the curtain is binding slightly or because of reduced power in the drive, a change in gearing to properly match the load to the drive might allow a speedup regar dless of where the problem is. It seems like a simple thing to do.
Clearly you lack some aspect of understanding the problem or you would not be asking for help. I don't know exactly what parts you understand and whi ch you don't. So I'm shotgunning ideas. Sorry if this isn't welcome.
--
Rick C.
-- Get 1,000 miles of free Supercharging
-- Tesla referral code - https://ts.la/richard11209
I welcome shotgun suggestions but I got the impression that you did not bother to read my posts with any care before firing them off.
Several of your questions were answered in the subject heading and first two sentences of my opening post. For example you now ask "I didn't see anything that indicated you disconnect the batteries to charge." Yet at the start I wrote: "The circuit includes a trickle current of about 35
t rechargeable batteries. The circuit includes a trickle current of about 3
5 mA but I?m still finding it necessary to recharge the batteries e very few weeks. To ensure I always have a replacement set ready I plan a li ttle circuit to cycle through: charge (say the recommended 300 mA for 16 ho urs), cut the supply, wait for N days, reapply the supply...repeating until needed. Is that a sensible approach? If so, what would be a good value for N?
arge? The batteries use about 4A two or three times a day on average, takin g about 5 secs to open or close the heavy curtains with the ex-screwdriver motor.
tteries and using a mains-derived power supply. But that would mean another largish case alongside the existing compact one. And presumably large heat sinks and consequent nervousness when away.
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ng that indicated you disconnect the batteries to charge. My phone does no t need to disconnect the one battery to charge. That seems like an inordin ately clumsy way to work. In fact, if you swap two sets of batteries, wher e is the problem??? You should be able to charge faster in a conventional charger and always have a set ready to use by the time the set on the curta in runs down.
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p on as to their full meaning. If the unit is running slowly because the b atteries or motor are now insufficient to the task, either because the curt ain is binding slightly or because of reduced power in the drive, a change in gearing to properly match the load to the drive might allow a speedup re gardless of where the problem is. It seems like a simple thing to do.
ot be asking for help. I don't know exactly what parts you understand and which you don't. So I'm shotgunning ideas. Sorry if this isn't welcome.
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Exactly, you still think it says something it doesn't.
I'm not interested in arguing with you about this. Enjoy.
--
Rick C.
-+ Get 1,000 miles of free Supercharging
-+ Tesla referral code - https://ts.la/richard11209
if changing batteries you could think about NiCds. Same voltage but more capable of high load currents (like starting a motor) plus they are more tolerant of trickle charging.
chargeable batteries. The circuit includes a trickle current of about 35 mA but I?m still finding it necessary to recharge the batteries every few weeks. To ensure I always have a replacement set ready I plan a little circuit to cycle through: charge (say the recommended 300 mA for 16 hours) , cut the supply, wait for N days, reapply the supply...repeating until nee ded. Is that a sensible approach? If so, what would be a good value for N?
? The batteries use about 4A two or three times a day on average, taking ab out 5 secs to open or close the heavy curtains with the ex-screwdriver moto r.
ies and using a mains-derived power supply. But that would mean another lar gish case alongside the existing compact one. And presumably large heat sin ks and consequent nervousness when away.
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Searching for parts these days I first go to Digikey to find the part I want. (good search engine) and then go to octoparts to see who has that part in stock. I assume octopart works in Europe.
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