I would like to expand the functionality of my warming box (6) by adding a rechargeable battery and thus allow mobile operation just like everyone knows it from a notebook approach.
Default supply should be provided by an external power supply (1). In parallel, the connected power supply should charge the permanently installed battery (4) via a DC coverter (2) followed by charge controller/BMS (3) - depending on the applied accumulator technology. So the battery should be constantly fully charged.
In addition, change over relay (5) should connect the accumulator and the load per default. As soon as the power supply is plugged in, the relay shall switch to interconnect the lines to supply the load via external power supply. Simultaeously, the interconnection between battery and load gets disconnected. Also, the battery charging pathway should become active. The relay itself is protected by a diode.
Is this a reasonable plan and diagram? Are the shown specifications suitable for the load (12V, max 6A)? And if so, has anyone please some recommendations regrding parts for (2), (3) and (4)? Which accumulator technology would you recommend? Li-Ion or lead–acid battery? 10Ah is the absolute minimum requirement, 20-30Ah would be much better.
Since you posted this in an Arduino forum, There are chances or an Arduino being somewhere in the circuit. Is this true? And if true, how will your Arduino react to the switching of the power?
of course there is sorry for the incomplete information: The "load" consists of an arduino nano that reads out a T sensor value and uses it to control a heating element as well as some fans (both via relays) depending on the measured sensor value (to keep T constant). Further, there are additional DC/DC buck converters installed to power the arduino (9V) as well as the connected sensor & relays (5V). The heater and the fans operate at 12V. The installation is completely finished and used since months with the external power supply without any malfunction.
Ideally I am looking for a setup where deplugging the external power supply has no impact on operating state of the arduino. But if this is more complicated to realize (because there might be a short time span where the arduino does not receive any power) then I am totally fine with a reset/restart of the arduino after having the external power supply deplugged!
I suggest you use a lead acid battery and a float charger, dead simple and no special charge controller or change over relay needed.
Your power supply will need to be 13V2 to 13V8*, just put it in parallel with the battery and the load. Add a buck converter to get whatever lower voltages you need.
You MUST put a fuse in one of the leads to the battery, as physically close to the battery as possible. A lead acid battery can easily produce enough current to melt wires and start a fire.
Change the battery after 5 years.
*Based on between 2V2 and 2V3 per cell. Depending who you ask and what you read you'll get different answers, but anything in that range should be OK.
Diodes can be used to automatically and very simply switch between any number of power sources. The highest voltage source wins out (the capacitor and resistor merely represent the load).
Just make sure that the diodes can handle the required current.
simply putting the power supply and the battery in parallel with the load sounds great. Would it look like shown below? Or needs the buck converter be installed at the location of the yellow placeholder? Also, the flow charger might be installed at the location of the brown placeholder.
Would this battery here fit my purpose? Could you please prove a link to a flow charger as well as to a fuse both suitable for my application so I can check all specifications and buy the correct parts? That would be extremely helpful.
NO!
Power the Arduino from 5V! They run on 5V!!
--> According to the spec sheet of my arduino nano (clone) it can be operated at 7-12V.
Regarding the idea with the diodes: Great, but I think there is a problem for me since I want to charge the batteries without dismanteling or a I wrong?
No problem, if the voltage of the float charger does not exceed that of the AC/DC power supply. Connect the float charger directly to the battery.
For the two diode solution shown in reply #5, the supply with the highest voltage automatically powers the entire project.
According to the spec sheet of my arduino nano (clone) it can be operated at 7-12V.
True, but it is not a good idea to exceed 9V on Vin. Since you need a regulator in any case, use a 5V switching regulator and power the Arduino via the 5V pin.
You show a "Float Charger" and a buck converter in parallel. What is that supposed to mean?
You show a "Float Charger" and a 13.8 V power supply. A 13.8 V power supply is a float charger to a SLA battery - but probably should be 13.2 V and current limited. One or the other, it is difficult to externally current limit a supply which is already the nominated voltage.
You do not use the diodes with a float charged SLA battery. Given that the float charger is indeed, voltage regulated and capable of providing the full current for the project, you simply pull the fuse in series with the battery if you need to change the battery, the float charger will keep things running while you do so..
Do not use "Vin" on a Nano - or indeed, any of the older Arduinos. the on-board regulator is essentially useless.
That is where you use the "buck" regulator, to provide regulated 5 V to the Nano etc., from the 12 V.
Would that work? If so, based on the specified load as well as on this lead-acid accumulator. Could you please provide a datasheet/link for a suitable fuse as well as for a suitable float charger so I purchase the correct parts? In my optinion, in a worst case scenario, the float charger needs to supply 6A for the load as well as the max current involved in the battery loading program (which seems to be up to 50% of nominal capacity so in my case this would be 6A, too).
Since I already own a 12V/10A AC/DC Power supply (it is used to supply the load since months): Why cant I use this power supply and connect it with an M083 charge regulator part as shown below? If this is a feasable approch - do I need to connect a diode to make sure current only flows in one direction (no connection between power supply and battery without passing the charge regulator). Is any diode type from this data sheet suitable? Also, in this case noch DC/DC Buck converter is required, correct?
Yes, that's exactly what we mean, but there are some points.
Does the load need exactly 12V? Many devices designed for 12V are quite happy with a range of voltages close to 12V. If you are using a SLA battery as shown then the voltage will be from about 11V when the battery is pretty much discharged to 13V2 (or 13V8) when the power supply is on and the battery is charged. If the load can cope with the variation then remove the DC/DC converter with the 12V output.
If the load does need 12V exactly (LED strips are quite fussy for example) then you need a buck/boost converter not a buck converter. A buck/boost converter will cope with the input voltage varying from less than 12V to more then 12V, a buck converter will not.
Can the power supply be adjusted to between 13V2 and 13V8? If so you can use it. No need for the charge regulator, if you supply a SLA battery with 2V2 to 2V3 per cell it will regulate it's own charging, that's one reason they are so easy to use.
In my opinion, in a worst case scenario, the float charger needs to supply 6A for the load as well as the max current involved in the battery loading program (which seems to be up to 50% of nominal capacity so in my case this would be 6A, too).
That seems like a safe assumption. However, I think a 10A PSU will be OK for what you are doing, 4A to charge the battery will be fine. Any decent PSU will just go into current limit if you overload it, limiting the charge current to the battery to something reasonable.
No, the voltage of my PSU may not be adjusted - it is fully enclosed equivalent to this one. But this is exactely where I thought the M083 - Battery charging regulator 12 V/DC will solve the problem. It is capable of processing 12V input and charges the accumulator at 1.5A max. Further this little helper manages the charging status and recharges if required etc. I think the PSU in combination with the M083 is fully equivalent to a float charger.
Conculding, I think I will try it as schemed in the 2nd picture in my previous post including the buck/boost converter modification described in this post. Just not sure about the flyback diode within the connecting line from the battery to the load. As a fuse I will simply use a 10A fuse known from automotive - is that fine?
That's not what the specification on the Kemco page says, it says the input voltage is 16 to 20V, not 12V. I conclude it is a linear regulator, that's all. Not suitable.
The second image in reply #11 is nonsense! The first image is what you need. I suggest you re-draw what you are proposing and post it, then I or someone will comment. At the moment I suspect you've still not understood, but without a schematic it's hard to know.
i) 13.2V seems to be the maximum possible since voltage may be adjusted 10% around nominal value - I hope this is enough. ii) For some reason it just scares me that there is not charging management device included. "Battery charging regulator" sounds so reassuring but if you all say that everything is fine as long as the PSU has a higher voltage that the max voltage of the accumulator (I guess max voltage occurs when the accumulator is fully charged) and further that it is also no problem to have the permanent connection between PSU and accumulator even if the device is being supplied by the PSU - then I think i should change my mind
Read the specification, how much current do you need? How much can it supply? I suspect it's just a linear regulator in a fancy box, if I'm right chuck it in the bin.
Your image in reply #15 is correct. If your load can tolerate the voltage varying between about 11 and 14V then you don't need the buck/boost converter, but if you are not sure then leave it in.
Only way to know is to buy a PSU like the one I lined to in reply #12 and see. I have a similar set up with 4 off 12V 12Ah batteries very similar to the one you linked to. I have a nominally 48V PSU, similar to the 12V one I showed you, adjusted to 52V8, I am not at the limit of its adjustment. The only problem I have is the batteries are getting old and I really should buy new ones
Marketing b******* (I can't swear, the mods will be on to me. Oh wait! I am a mod! )
Lead acid is an old technology, it's cheap, simple and robust. The downside is its heavy and bulky, but for a lot of applications that doesn't matter. Lead acid batteries were charged perfectly successfully long before there were electronic charge controllers.
Haha - but you seem to handle the power "they" gave you wisely
Thanks again to everyone who took the time and provided support. After the endorsement I will go with the approach shown in reply #15 and see if i get it realized. Please keep your fingers crossed
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