Upgrading UPS battery

[alexan_e]

I think he was referring to the first schematic in post #12

 

[Raza]

Yes may be by the time he posted it was not updated.

 

[Pjdd]

That's right. I was referring to the previous diagram and the second one had not yet appeared when I posted my comment.

And here's post explaining the principle of a battery charger - post #8 in the thread "Regarding Vehicle Battery Charger". Here. The sample circuit I posted is that of a manual charger, but it shows the principle of setting the charging current by means of a resistance between a voltage source and the battery.

 

[Raza]

Pjdd,
You are right but here we were talking about a particular battery under consideration. I have added a bunch of 10 batteries (7.5 AH each) to the one of this UPS, APC Back UP500, actually 350 VA and the internal battery is also in circuit but these batteries have an external charger capable of controlling the charging current and Low and High Battery monitoring. All these batteries are Lead-Acid Gel batteries. Once I made a mistake and did not disconnect the internal charger and forgot to power up the external charger, THE RESULT (was obvious) the internal charger was damaged caused by over current draw. The transformer (only 10VA) was burnt, the diodes, 1N4004 were shortened.

 

[holabr]

After reading all these posts and the fact that I am really a novice, I am confused. Bottom line question is should I use an external "trickle charger" or some other type of charger connected to the new larger battery? If so, do I simply connect it to the battery terminals while it is also connected to the UPS?

 

[Pjdd]

Sorry, holabr, but these things happen from time to time when two people have different opinions about a technical point. I understand your wish to have an unambiguous answer, But that is exactly where Raza and I disagree. I say go ahead and simply connect the larger battery in place of the internal one. And Raza says no. The only thing to do now is to go back to the technical discussion and continue to thrash out the issue.

Fact 1: Current flows from a higher voltage to a lower one. The amount of current is determined by the difference in voltage between the two and the total equivalent resistance between them. That is, I = (V1-V2)/R where the higher voltage V1 is the charger voltage and V2 is the instantaneous battery voltage at the time of charging. It has nothing to do with the Ampere-hour (Ah) capacity of the battery.

Fact 2: Stress on the charging circuit is determined by the charging current, not by the capacity of the battery. An exception would be if the charging took place only for a very short time (seconds or a very few minutes) and the circuit components do not have time to reach a stable temperature (a state of thermal equilibrium), but this is not the case here.

Unless the charger is very poorly designed, it can be expected to be able to charge a fully discharged (not over-discharged) battery to full capacity. This will take at least a few hours and the circuit components will have more than enough time to reach a final temperature. That is, component temperature will stop rising after some time. Any half-decent design will ensure that the final temperature will be well within safe limits for the devices.

So, even if a battery of higher capacity is being charged and the charging time is prolonged, there is no reason for the charging components to burn up. There are some possible reasons for the damage to Raza's charger:
1) The charger was badly designed (not likely)
2) One or more of the paralleled batteries was defective
3) Accidental wrong (reversed) connection of one or more batteries

There are other possibilities but it's not practicable to consider all possibilities without knowing the exact circumstances.

 

[tpetar]

I have a small UPS (APC Back-UPS 350) that has a 12 volt 7aH battery. I use it to keep my router and cable modem up and running in case of a power outage. I recently got a couple of Group 24 wheelchair deep cycle batteries. Can I connect these in parallel to the 12 volt battery in the unit to greatly improve the up time of the UPS? Do I need to provide a seperate battery charger/tender for the Group 24s and somehow "isolate" them from the UPS? What other considerations are there? I don't want to burn up the UPS.

1. Can I connect these in parallel to the 12 volt battery in the unit to greatly improve the up time of the UPS?
You can everything, but this is not good. Paralleling batteries of different size and chemistry not good. Deep cycle lead acid is different from starter lead acid. Must be the same capacity, chemistry, tech and even with similar internal resistance if you whant to paralleling them. You must get out existing 7,2Ah battery and put only bigger one.

2. Do I need to provide a seperate battery charger/tender
Yes. UPS charging 7,2Ah battery with max 0,7A. You can put 100Ah you will get only 0,7A charging. If lead acid chemistry of battery this is bad, only because needed time for charging. Lead Acid should put on charge, immediately after fully discharging. Should put some charger (float charger 13,8V or 13,5V if voltage higher from ups charging voltage then ups will pull power from charger).

3. Charger should be float charge with limited current. For car I using LM338K over ten years, like float charger, also he limit current to 5A (cant go over 13,8V or 13,5V depends from temperature, and cant go over 5A, suitable for 45-55-60Ah /10). First stage of charging "CAN" be constant current but this is only because to shorten time of charging. Better is float charging, this prolong life of batteries. I speaking this from expirience. I have several older batteries lead acid car starter, different manufacturer, about 14 year old, I test it for cranking at winter (below 0C, often at -10C) like new (also desulfatisator involved in regular maintance, always charged with float charger, and current limiter circuit /10 /12. I monitoring and measuring internal resistance of this batteries and its good, not new but good). If you whant to shorten time for charging battery use multistage charger, but for battery life (lead acid), and circuit implementation use float charging. First step of charging "CAN" be constant current but this is not law for charging, because that goes absorption stage to relax battery. DO NOT LEAVE LEAD ACID DISCHARGED FOR LONGER TIME, RECHARGE IT IMMEDIATELY !!!!

4. LM317 have internal current and thermal shutdown limit for protection of IC. You can ask for more amperage but you will get only what you get, not over 1,5A for LM317 if datasheet conditions are fulfilled. We talk about LM317 maybe you have LM338T or something else, check circuit and device parts, maybe is not at all LM317. You can shortcut LM317 LM338 and nothing, you cant killing like that, they have internal current limit protection and thermal protection. Maybe 0,7A charging need smaller heatsink (obviously), if you pull 1,5A constant for longer time, then semiconductor will work on higher temp, and shorten his life, you should improve cooling. But what I know, current in UPS is limited to 0,7A!!!!!!!! Gelled lead acid 7Ah are charged with 0,7A recommended according to datasheets, max 1A-1,1A but on what temperature. In UPS device temperature is very HOT!!! Trafo core is small and very hot, designed to work several minutes, not hours, battery is sticked together with trafo.

5. Standard PC UPS not designed for longer working time. They are designed to take over on few minutes not for hours and hours, because that cooling and heatsinks are small, you need to put some additional cooler/fan, I mean bigger 12V like for power supply 7x7cm, should I dare to say to increase heatsink (replacing with bigger). Trafo core is smaller then should be. Because that temperature rising in case of device, shorten battery life. Should put some nice fans there. Also there is larger expensive server room UPS, I mean real UPS, but price hmm hmmm :roll: this nice devices are designed to work on longer times.

6. You mention deep cycle batteries, this type of batteries, are different from starter. They charging and discharging with smaller current. Not appropriate for UPS usage, Ok only if you plan to use bank of this batteries and special chargers for them. Lead acid starter and deep cycle are different types, but familiar chemistry. Its long story, but in few words, starter is for higher amperage for shorten time, 100A-200A (depends from capacity) for few seconds, and not for total disharging. If you go to 10,5V this can kill or drasticaly decrease capacity and health of battery. Simple its float battery about 70% level or 30% discharging is Ok. But deep cycle can go to deep discharge, but you cant pull high amperage from it. Higher amperage can melt plate, and kill battery.

7. Safety and health. If you use ups indoor, should use gell/glass tech of battery. Consider that lead acid with sulfuric acid make dangerous gases when charged and discharged, even flamable.

8. Check schematic of UPS. Use ampermeter and voltmeter and monitor what happening when you put bigger battery. Test it on some harder load for some time, and later inspect PCB and parts.



I use Mustek 2000 several years with two 100Ah in serie for 24V and all ok.

 

[alexan_e]

Unfortunately we have lost anything posted in the forum in the the last 12 hours because of problems in the forum engine during the update.
I have received the two missing posts in my email so I will add them below


POSED BY Pjdd

*
1. Can I connect these in parallel to the 12 volt battery in the unit to greatly improve the up time of the UPS?*
You can everything, but this is not good. Paralleling batteries of different size and chemistry not good. ...........(snipped for brevity).........)

This was all covered in previous posts.

*2. Do I need to provide a seperate battery charger/tender*
Yes. UPS charging 7,2Ah battery with max 0,7A. You can put 100Ah you will get only 0,7A charging. If lead acid chemistry of battery this is bad, only because needed time for charging. Lead Acid should put on charge, immediately after fully discharging. Should put some charger (float charger 13,8V or 13,5V if voltage higher from ups charging voltage then ups will pull power from charger).

According to his own account, the OP has limited experience in electronics. Explanations and suggested solutions are best given to suit an OP's level of understanding. If the UPS's internal charger and and external charger are connected at the same time, there's no way of knowing how they will interact unless the design details of both charging circuits are known.

_*_3. Charger should be float charge with limited current._*_ ........(snipped for brevity)........ DO NOT LEAVE LEAD ACID DISCHARGED FOR LONGER TIME, RECHARGE IT IMMEDIATELY !!!!

These are all general comments on good battery charging practice. Not really relevant to the OP's situation.

*4. LM317 have internal current and thermal shutdown* limit for protection of IC. You can ask for more amperage but you will get only what you get, not over 1,5A for LM317 if datasheet conditions are fulfilled. We talk about LM317 maybe you have LM338T or something else, check circuit and device parts, maybe is not at all LM317. You can shortcut LM317 LM338 and nothing, you cant killing like that, they have internal current limit protection and thermal protection. Maybe 0,7A charging need smaller heatsink (obviously), if you pull 1,5A constant for longer time, then semiconductor will work on higher temp, and shorten his life, you should improve cooling. But what I know, current in UPS is limited to 0,7A!!!!!!!! Gelled lead acid 7Ah are charged with 0,7A recommended according to datasheets, max 1A-1,1A but on what temperature. In UPS device temperature is very HOT!!! Trafo core is small and very hot, designed to work several minutes, not hours, battery is sticked together with
trafo.

If you're talking about the charging transformer, they are not designed to operate for just a few minutes. A 0.7A charger will take about 15 hours to fully charge a 7.5Ah battery. If the charger cannot run for more than a few minutes, the battery will never get charged to a useful level.

Say you're using a UPS to power a desktop computer drawing 250W and mains power goes off and the UPS takes over for a few minutes until you can shut the computer down. During that time, the UPS draws at least 25A (at an overall efficiency of more than 80% which is rather optimistic). Say you take 5 minutes to wind up what you were doing and shut down. In those 5 minutes, you will have drained more than 2Ah from the battery. (The actual effect will be more than 2Ah because batteries are inefficient at the very high current drain relative to their rated capacity).

When mains power comes back, the UPS charger has to replenish the lost 2Ah. At 0.7A charging current, it will take at least 4 hours to top up that 2Ah (at an estimated charging efficiency of 70% which again is optimistic). This kind of situation is expected to happen. In fact, it's the very reason we use UPSes. So it's simply not correct to say that the charger is designed to operate only for a few minutes.

*5. Standard PC UPS not designed for longer working time.* They are designed to take over on few minutes not for hours and hours, because that cooling and heatsinks are small, you need to put some additional cooler/fan, I mean bigger 12V like for power supply 7x7cm, should I dare to say to increase heatsink (replacing with bigger). Trafo core is smaller then should be. Because that temperature rising in case of device, shorten battery life. Should put some nice fans there. Also there is larger expensive server room UPS, I mean real UPS, but price hmm hmmm :roll: this nice devices are designed to work on longer times.

That is when the UPS is working at or near its maximum rated power. In the OP's case, he's running it at perhaps less than one-tenth of its rated capacity. Any UPS that cannot run indefinitely at that load will be a very very poorly designed one.

*6. You mention deep cycle batteries,* this type of batteries, are different from starter. They charging and discharging with smaller current. Not appropriate for UPS usage, Ok only if you plan to use bank of this batteries and special chargers for them. Lead acid starter and deep cycle are different types, but familiar chemistry. Its long story, but in few words, starter is for higher amperage for shorten time, 100A-200A (depends from capacity) for few seconds, and not for total disharging. If you go to 10,5V this can kill or drasticaly decrease capacity and health of battery. Simple its float battery about 70% level or 30% discharging is Ok. But deep cycle can go to deep discharge, but you cant pull high amperage from it. Higher amperage can melt plate, and kill battery.

Again this is irrelevant to the thread because the OP want to use them only for very light loads.

Now for my own practical experience in comparable situations:

1. Two month ago (last November), I used a small UPS to run a light load at an outdoor sporting event where there was no mains power. I used it for several hours everyday for 3 consecutive days. It stayed cool.

2. Some years ago, I needed an extra UPS for one of my computers. I had an old APC UPS that I had discarded a few years because the battery was no longer usable and I didn't bother replacing it. I also had an old car battery that I had replaced with a new one because it was no longer good enough for use in a car. I combined the two without any external charger and it served me well for a long time.


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POSED BY tpetar

2. Some years ago, I needed an extra UPS for one of my computers. I had an old APC UPS that I had discarded a few years because the battery was no longer usable and I didn't bother replacing it. I also had an old car battery that I had replaced with a new one because it was no longer good enough for use in a car. I combined the two without any external charger and it served me well for a long time.

I hope that you know what you say. If you read and understand my post you will understand. When you paralleling different batteries even the same tech. and capacity, if internal resistance is not the same, one will draw power from another.

1. Two month ago (last November), I used a small UPS to run a light load at an outdoor sporting event where there was no mains power. I used it for several hours everyday for 3 consecutive days. It stayed cool.

UPS cant stay cool it any operation. It warm up during regular funcioning. Maybe you have some ups in fridge.

Any UPS that cannot run indefinitely at that load will be a very very poorly designed one.

This is not true! All UPS is designed for their purposes. You must read manufacturer user manual and other data. Manufacturer make UPS (we talking about regular desktop PC UPS) for giving backup time of few minutes to 30-45min. Because that they puting smaller heatskinks, and battery is not 10000Ah but 7Ah.

If you're talking about the charging transformer, they are not designed to operate for just a few minutes. A 0.7A charger will take about 15 hours to fully charge a 7.5Ah battery. If the charger cannot run for more than a few minutes, the battery will never get charged to a useful level. .... ....

You didnt read what I write, or you didnt read carefully. I say he need additional charger. 0,7A is enough for charging bigger batteries.

If the UPS's internal charger and and external charger are connected at the same time, there's no way of knowing how they will interact unless the design details of both charging circuits are known.

Again you didnt read my text carefully. I said : Should put some charger (float charger 13,8V or 13,5V if voltage higher from ups charging voltage then ups will pull power from charger).

According to his own account, the OP has limited experience in electronics. Explanations and suggested solutions are best given to suit an OP's level of understanding.

Pjdd I respect any people with their level, he ask some question I answer it. Maybe he is prof. on some university and just open account on edaboard.

 

[tpetar]

Actually this is my version, then something happen to web site:

My friend and dear Pjdd,

2. Some years ago, I needed an extra UPS for one of my computers. I had an old APC UPS that I had discarded a few years because the battery was no longer usable and I didn't bother replacing it. I also had an old car battery that I had replaced with a new one because it was no longer good enough for use in a car. I combined the two without any external charger and it served me well for a long time.

I hope that you know what you say. If you read and understand my post you will understand. When you paralleling different batteries even the same tech. and capacity, if internal resistance is not the same, one will draw power from another. I guess that you have lots efficiency of power in that connection where one battery have role to be load and other battery charger. Pjdd what is that battery from your car 10Ah ? You should know what current is needed for charging batteries. According to manufacturer advice /10 > if 55Ah battery then you need 5,5A of charging current. That told us that you have bad sulfated batteries in your "efficient" ups, because you didnt recharge batteries, they stay long period disharched waiting to charge from 0,7A from UPS. Pjdd You should inform yourself about lead acid batteries. Can You be specific with "long time" period (day two) ? Are you using it like standby only and never used just standby, or you deepcycled it? Do you know that desktop UPS discharge batteries to 10,5V you must inform yourself what that voltage means for starter lead acid batteries! Read UPS and battery manufacturer advice for battery life in UPS.

1. Two month ago (last November), I used a small UPS to run a light load at an outdoor sporting event where there was no mains power. I used it for several hours everyday for 3 consecutive days. It stayed cool.

UPS cant stay cool it any operation. It warm up during regular funcioning, even just in standby. Maybe you have some ups in fridge and turned off, and power pull from fridge power cable. But if not we must immediately announce manufacturers, because we improve theirs devices. You dont need to carry that heavy "efficient" UPS and battery bank with you on sport event, yous hould take just and ordinary inverter (switcher, there is lots in shops for small money). Pjdd you should know that desktop ups not made to be efficient, look trafo core square area, if you know about transfmormers something you will that that is small trafo for that purposes. But this trafo have lots of loses and not efficient, just look a disipation in temperature. Manufacturer made ups to be small, compact, cheap, and that they do the job for their purposes. I dont know what batteries you carry with you on that sport event, maybe is bodybuilding with heavy truck lead batteries. What battery size you propose for carrying for several hours, and did you turn some load on that ups at all, or just ups stay in standby with one led or red le diode ?

Any UPS that cannot run indefinitely at that load will be a very very poorly designed one.

This is not true! All UPS is designed for their purposes. You must read manufacturer user manual and other data. Manufacturer make UPS (we talking about regular desktop PC UPS) for giving backup time of few minutes to 30-45min or some other defined time. Because that they puting smaller heatskinks, and battery is not 10000Ah but 7Ah.

If you're talking about the charging transformer, they are not designed to operate for just a few minutes. A 0.7A charger will take about 15 hours to fully charge a 7.5Ah battery. If the charger cannot run for more than a few minutes, the battery will never get charged to a useful level. .... ....

You didnt read what I write, or you didnt read carefully. I say he need additional charger. 0,7A is enough for charging bigger batteries.

If the UPS's internal charger and and external charger are connected at the same time, there's no way of knowing how they will interact unless the design details of both charging circuits are known.

Again you didnt read my text carefully. I said : Should put some charger (float charger 13,8V or 13,5V if voltage higher from ups charging voltage then ups will pull power from charger). Its a basic Pjdd you should know this, that always higher potencial goes to lower potencial first.

According to his own account, the OP has limited experience in electronics. Explanations and suggested solutions are best given to suit an OP's level of understanding.

Pjdd I respect any people with their level, he ask some question I answer it. Maybe he is prof. on some university and just open account on edaboard, and just now he have rookie account, but this dont tell us that he dont know anything, he just ask us something, and we should try to help him. Maybe your answers good but bad presented, or bad answers good presented. Purpose of forum dialogs is in that, that many people says their opinions. Pjdd you take role of some professor of electronics and selling lessons which answer is good which is bad.



Pjdd do you know difference between deepcycle and starter batteries ?
Can you read again question on first post, what he ask?

Pjdd, if you read carefully, I say that he can put some bigger batteries on UPS to prolong working time of UPS, but should improve cooling, charging, .....

Pjdd I see your pain from many previous posts, but you should stay open for others opinion.

 

[Pjdd]

@tpetar: Everybody's entitled to his own opinion and different people sometimes have different opinions on technical matters. But I'll appreciate it if you stopped sending me rude PMs. Some of the disagreements may be due to the fact that English is not your first language. Neither is it mine, but perhaps I have the benefit of more practice.

You keep repeating the same warning about paralleling different battery types. I already covered that issue in post #7 and the OP accepted it in post #10. I kept the explanation brief without going too much into the technical details because the OP said that he's a novice in electronics. This was apparent from his earlier posts and he specifically said so in post #25.

Originally Posted by Pjdd
1. Two month ago (last November), I used a small UPS to run a light load at an outdoor sporting event where there was no mains power. I used it for several hours everyday for 3 consecutive days. It stayed cool.

UPS cant stay cool it any operation. It warm up during regular funcioning. Maybe you have some ups in fridge.

There's no need to be sarcastic. "Cool" is a relative term. If you live in a place where summer temperatures reach 45°C, 35°C will feel cool. If your local tempearture seldom goes over 30°C (as it is where I live), 28°C feels quite hot.

When I used that UPS for outdoor work, I checked the internal temperatures from time to time. They never got more than slightly warm. In terms of safe operating temperature limits, that is cool.

Any UPS that cannot run indefinitely at that load will be a very very poorly designed one.

This is not true! All UPS is designed for their purposes. You must read manufacturer user manual and other data. Manufacturer make UPS (we talking about regular desktop PC UPS) for giving backup time of few minutes to 30-45min. Because that they puting smaller heatskinks, and battery is not 10000Ah but 7Ah.

I have used desktop UPSes at light load for long periods many times. The incident I related was just one example. Manufacturers don't always include all possible information. They provide information for situations in which their product is used for its main purpose. But in the real world, we often use a product for purposes other than the main intended application.

Temperature rise can be easily calculated from power dissipation and heatsink thermal resistance. But even without doing precise calculations, it can be deduced with common sense that if a UPS can run without overheating for 10 minutes with a load of 300W, it should be able to run continuously with a load of 30W. Otherwise it's of a very poor design. And running at one-tenth or less of the full rated power is exactly what the OP wants to do with his UPS.

If the UPS's internal charger and and external charger are connected at the same time, there's no way of knowing how they will interact unless the design details of both charging circuits are known.

Again you didnt read my text carefully. I said : Should put some charger (float charger 13,8V or 13,5V if voltage higher from ups charging voltage then ups will pull power from charger).

It is you who did not read my post carefully. The UPS will certainly try to pull in power from the higher voltage from the external charger. BUT that may be harmful to the UPS. For example, if the UPS charger has no protection against reverse current from an external higher voltage, it could well destroy the UPS's internal charger.

According to his own account, the OP has limited experience in electronics. Explanations and suggested solutions are best given to suit an OP's level of understanding.

Pjdd I respect any people with their level, he ask some question I answer it. Maybe he is prof. on some university and just open account on edaboard.

This is one of those misunderstandings that may be due to a language problem. "According to his own account" means "From what he said about himself". It does not refer to his account at edaboard.

 

[tpetar]

But I'll appreciate it if you stopped sending me rude PMs.

Please tell us what I send you. Or we should ask admins what is rude in PM.

There's no need to be sarcastic. "Cool" is a relative term.

I just quote what you say, and you say nothing about wheather outside you say: "Two month ago (last November), I used a small UPS to run a light load at an outdoor sporting event where there was no mains power. I used it for several hours everyday for 3 consecutive days. It stayed cool. "

...
...
...

We can continue this conversation but I dont see purpose of that.
You are obviously angry for some reason, but we cannot help with that to Holabr. :roll::smile::wink:

 

[Pjdd]

tpetar's post #29 came in while I was typing my own post #30, so there's some lack of synchrocity. I was answering the points in the post quoted by alexan_e. But tpetar added a lot of comments in #29 and that may cause some confusion.

@tpetar: You criticise and argue with my posts, which is your right, but you criticise me for making my own comments and you keep making condescending personal remarks too. Do you have any idea how insulting some of your remarks are?

To other forum members who have been following this thread, I apologize for the direction this thread is heading. In the interest of keeping a decent atmosphere, I'll bow out now without making any further posts.

 

[Raza]

To all my colleagues,
The original question was very simple,

I have a small UPS (APC Back-UPS 350) that has a 12 volt 7aH battery. I use it to keep my router and cable modem up and running in case of a power outage. I recently got a couple of Group 24 wheelchair deep cycle batteries. Can I connect these in parallel to the 12 volt battery in the unit to greatly improve the up time of the UPS? Do I need to provide a seperate battery charger/tender for the Group 24s and somehow "isolate" them from the UPS? What other considerations are there? I don't want to burn up the UPS.

The answer should have been to ease the guidance seeker not to put him in confusion. I can not say this post is going in which direction and how far we are gone but still his REQUESTED INFORMATION is awaited. My humble request to all is that please put some simple reply and let him be satisfied.
HOPE my requested will be honored.

 

[tpetar]

To all my colleagues,
The original question was very simple,

The answer should have been to ease the guidance seeker not to put him in confusion. I can not say this post is going in which direction and how far we are gone but still his REQUESTED INFORMATION is awaited. My humble request to all is that please put some simple reply and let him be satisfied.
HOPE my requested will be honored.

Because that I make post #27 but I'm interrupted from Pjdd. I because that put thread question on top of post #27.



There is another edaboard thread can be useful like additional material :

Battery duration calculation
https://www.edaboard.com/threads/237578/

 

[Raza]

Again my request that the TOLERANCE IS THE BEST WAY. We can be in discussion for years to each other but I feel the the question poster expects a nice and easy way of guidance, so please.............................!

 

[tpetar]

Again my request that the TOLERANCE IS THE BEST WAY. We can be in discussion for years to each other but I feel the the question poster expects a nice and easy way of guidance, so please.............................!

Of course I agree with that, and support that.


We not heard recently our friend Holabr, what he thinking about his problem-question, based on posts from all discussants. Maybe some additional question for all ?

 

[holabr]

I really did not intend to start a fight. I really am a novice and don't understand a lot of the theory being debated.

There was some mention of an inverter in an earlier post which raises a question (hopefully without starting another fight). Can you use a larger capacity battery with an appropriate charge to power an inverter to act as a UPS? Basically the charger would be supplying power to the inverter while mains was on and the battery would take over if mains fails. Is this in essence what the UPS does or is there some sort of switching between mains and battery when power fails? I bring this up because it seems to me that an inverter is designed to run for an extended period of time and not just a few minutes like some posters suggested concerning desktop UPS units.

 

[tpetar]

I really did not intend to start a fight. I really am a novice and don't understand a lot of the theory being debated.
There was some mention of an inverter in an earlier post which raises a question (hopefully without starting another fight).

We are all friends of course, there should not be space for angry. Sometimes bad thing happen but we are all humans, we are all brothers and sisters. Sometimes confrontation of opinions make great solution. Sometimes we have to add some additional heat to make better sword from steel.

Can you use a larger capacity battery with an appropriate charge to power an inverter to act as a UPS?

Of course you can! But that inverter must have possibility to be a UPS. You can add 200Ah if you whant, you will get more UPS time. On market, there are inverters and ups (ups also have inverter inside), standard inverter devices dont have ups possibility.

Basically the charger would be supplying power to the inverter while mains was on and the battery would take over if mains fails. Is this in essence what the UPS does or is there some sort of switching between mains and battery when power fails?

Yes my friend, if mains is present, UPS giving power from mains, if lose mains power ups (name of ups told everything), then ups fast switch on inverter. Inverter get power from battery. For attaching charger on inverter I write in my post I think #27.

I bring this up because it seems to me that an inverter is designed to run for an extended period of time and not just a few minutes like some posters suggested concerning desktop UPS units.

I have UPS working several years on big batteries with chargers on it, without problems, but I just make cooling stronger. I add some additional bigger fans, open cases on some places...


But only to know there is device known as commercial portable inverter and desktop PC ups (inverter is for long duty cycle, UPS is for UPSssss situations, but can be done) Take in mind that Desktop PC UPS have very bad efficiency and commercial portable inverter have better almost 90% - but manufacturer data is last word :




Desktop UPS PC is not made to be efficient, its just UPS. If you put bigger trafo core then we can talk.

Question : Why then manufacturers dont make Desktop PC UPS like switcher tech ?
They make but price is higher, and electronics must be complex. Switcher cant give that short time period for switching from main power outlet to inverter/battery, cant make power from inverter in that short period, and switcher will pull lots of power in peak on start. This is challenge for designers.



Additional :

Will be nice and helpful to look some transformator tutorial or basics, specially about efficieny, core square area, frequency,...

Also will be nice and helpful to look some heatsink calculation and need for semiconductor power dissipation, specially for MOSfet's,....


All of this should starts from efficiency and trafo. In desktop PC ups there is small trafo, catastrophic efficiency, heat everywhere arroundon trafo you can bake food. Its for shorter term, because that, price, smaller, compact,...
You must have proper square area of trafo core to make efficiency better, but price, weight, not portable,........

In solar house systems almost all use system using switching inverter design, efficiency nice, compact,.... Also there is switcher UPS, but price,.... To improve efficiency need big square area of trafo core, because that complex electronics do the thing. Switchers use and works with smaller HF trafo on 25KHz (example) and .....

Keep in mind that common UPS have square wave shape!!! Motors, compressors, trafo, pumps, ..... and other inductive load will suffer. "Inverter" (left picture) often have simulated sinusoide or pure sine shape. .............



One example of switching for mains to battery/inverter power in ups (this is done in 2ms or 4ms manufacturer make declare for particular model type):






How long will battery stand read my posts in this thread :
https://www.edaboard.com/threads/237578/

Take in mind Peukert's law :
Peukert's law - Wikipedia, the free encyclopedia

What is an Amp Hour and How to Calculate Battery Capacity | OverlandResource.com – Overland expedition travel info.

 

[Tahmid]

I don't understand, lead acid batteries are supposed to need a constant current cycle in the first stage of the charge, how does a constant voltage method like the above provide a proper charge?
I'm not experienced at all with USP so I'm just asking these questions to help me understand the circuit operation.



I did a search for LM317 lead acid charger but the circuits I found included some kind of current limiting

Most UPS-es that I have seen use the LM317 set at somewhere around 14V (fixed) to charge the battery at constant voltage (no constant current mode). This means that the battery takes a long time to charge as it doesn't draw much current. But it's a good system as my "mikro" UPS was bought more about 9 years ago and needed battery replacement only 2 times. The battery is hardly ever overcharged, because it enters trickle mode when charging is "full". I've also seen that the charger has overcurrent limiting via a shunt resistor and transistor, using the 0.6-0.7V as the voltage at which current is limited. Not a very accurate method, but it works.

Hope this helps.
Tahmid.