Sir I would like to build battery charger 27.2 Volt 35 / 70 Amp by paralleling 5 / 10 no. of 27.2 Volt 7.0 Amp Battery chargers.
I designed 27.2 Volt 7.5 Volt according to Power Integration design note 14 using OpAmp LM 358
This is Constant Voltage Constant Current o/p power supply used as float type battery charger which is working fine.
I tried to parallel 2 no. of such PSUs they are also working fine,charging current is doubled. Even I tried to parallel two chargers of different max current limit, charging current is sum of max current limit of both the chargers.
Now I want extend this to still higher level say 35 / 70 amp.
a) Is it possible ?
b) Is there any changes needed ?
c) What will be Max. current & Power can be achived ?
I designed 27.2 Volt 7.5 Volt according to Power Integration design note 14 using OpAmp LM 358
This is Constant Voltage Constant Current o/p power supply used as float type battery charger which is working fine.
I tried to parallel 2 no. of such PSUs they are also working fine,charging current is doubled. Even I tried to parallel two chargers of different max current limit, charging current is sum of max current limit of both the chargers.
Now I want extend this to still higher level say 35 / 70 amp.
a) Is it possible ?
b) Is there any changes needed ?
c) What will be Max. current & Power can be achived ?
Hello!
First of all, I am sorry, but I was not able to find the design note you were referring to after a quick google… perhaps you could provide a link or download, please?
As for your questions, much depends on the actual circuit. I am assuming you are charging lead-acid batteries or something similar… dealing with the interaction of dedicated charger chips for something like Lithium ion batteries would be difficult 🙂
To answer your questions:
1. Yes, it is certainly possible to parallel then for increased current capacity, but: it is not as simple as it might seem.
2(a) Yes again, there will almost certainly be changes needed. First, if these are indeed SMPS, then they will likely have good load regulation. Normally, you would need some low value resistors in series with each supply to help share the load current properly. Otherwise, one supply will take most of the load until its output voltage collapses, resulting in a very uneven split. Worse still, some supplies I have seen have a positive slope in their load regulation – higher loads actually increase the output voltage slightly! Without proper current sharing, this would likely cause a failure very quickly. However, your supplies have current limiting built in. This is probably why you were able to directly parallel two so easily. Without seeing a schematic, I cannot tell you how two or more would interact – I suspect that without load sharing resistors, there could be still a possibility for problems.
(b) You would also want to synchronize the oscillators of the supplies, if possible. For audio, this is often done to prevent audible beat frequencies. In your case, I would still suggest it to reduce instantaneous stresses from current sharing.
(c) Be sure to respect the charging curve and limits of your battery. Remember that the current limit is now effectively the sum of all the supplies. Are you attempting to charge multiple batteries simultaneously? If so, in what configuration? If multiple batteries are in parallel at any point, then it may be possible to exceed the desired current for a single battery despite the overall current still being below your total limit of 70A.
3. In theory? Limited only by your wiring gauge, number of supplies, etc. Practically, it may be cheaper to design a few, better-rated supplies to achieve a given output current. As always, keep a margin of safety for your ratings (larger than usual, if possible, as the load sharing will never be perfect).
First of all, I am sorry, but I was not able to find the design note you were referring to after a quick google… perhaps you could provide a link or download, please?
As for your questions, much depends on the actual circuit. I am assuming you are charging lead-acid batteries or something similar… dealing with the interaction of dedicated charger chips for something like Lithium ion batteries would be difficult 🙂
To answer your questions:
1. Yes, it is certainly possible to parallel then for increased current capacity, but: it is not as simple as it might seem.
2(a) Yes again, there will almost certainly be changes needed. First, if these are indeed SMPS, then they will likely have good load regulation. Normally, you would need some low value resistors in series with each supply to help share the load current properly. Otherwise, one supply will take most of the load until its output voltage collapses, resulting in a very uneven split. Worse still, some supplies I have seen have a positive slope in their load regulation – higher loads actually increase the output voltage slightly! Without proper current sharing, this would likely cause a failure very quickly. However, your supplies have current limiting built in. This is probably why you were able to directly parallel two so easily. Without seeing a schematic, I cannot tell you how two or more would interact – I suspect that without load sharing resistors, there could be still a possibility for problems.
(b) You would also want to synchronize the oscillators of the supplies, if possible. For audio, this is often done to prevent audible beat frequencies. In your case, I would still suggest it to reduce instantaneous stresses from current sharing.
(c) Be sure to respect the charging curve and limits of your battery. Remember that the current limit is now effectively the sum of all the supplies. Are you attempting to charge multiple batteries simultaneously? If so, in what configuration? If multiple batteries are in parallel at any point, then it may be possible to exceed the desired current for a single battery despite the overall current still being below your total limit of 70A.
3. In theory? Limited only by your wiring gauge, number of supplies, etc. Practically, it may be cheaper to design a few, better-rated supplies to achieve a given output current. As always, keep a margin of safety for your ratings (larger than usual, if possible, as the load sharing will never be perfect).
Here you go Terran .
http://www.nalanda.nitc.ac.in/industry/appnotes/PowerInt/dn14.pdf
About the synchronising the powersupply's .
In the top series of power intergration you dont have that option .
This serie of regulators is typical for powers upto 250 watt powersupply's .
Mostly you will find it in anything from phone chargers to for instance laptop supply's.
Maybe its wise to choose a topology that can handle with 1 powersupply .
Professionaly i design and build battery chargers and we actualy builded the power intergration during the last year but we never even considert to parallel the supply's (sorry that i cant offer you detailed experiences on that)
If you want to synchronise the supply's you would have to use pwm controllers like sg3525 or tl 494 .
Where my doubt comes in paralleling to 75 amperes is this .
Cost efficiency (and size) would rule out building 10 powersupply's instead of 1 big one .
Further i fear imbalance problems & following to that interactions between slight differences of output A with the nearest feedback of output B .
(the wrong feedback loop trying to decrease or increase dutycycle)
(lossy but it might solve some matters is seperate all outputs from the common output by a diode so you're actualy certain you measure the right output)
For leadacid battery's we build chargers (microprocessor controlled) upto 100 ampere's .
did you consider a conventional supply with microcontroller (current & voltage measuring) with thyristors for switching of charge (rectification)
Goodluck 🙂
http://www.nalanda.nitc.ac.in/industry/appnotes/PowerInt/dn14.pdf
About the synchronising the powersupply's .
In the top series of power intergration you dont have that option .
This serie of regulators is typical for powers upto 250 watt powersupply's .
Mostly you will find it in anything from phone chargers to for instance laptop supply's.
Maybe its wise to choose a topology that can handle with 1 powersupply .
Professionaly i design and build battery chargers and we actualy builded the power intergration during the last year but we never even considert to parallel the supply's (sorry that i cant offer you detailed experiences on that)
If you want to synchronise the supply's you would have to use pwm controllers like sg3525 or tl 494 .
Where my doubt comes in paralleling to 75 amperes is this .
Cost efficiency (and size) would rule out building 10 powersupply's instead of 1 big one .
Further i fear imbalance problems & following to that interactions between slight differences of output A with the nearest feedback of output B .
(the wrong feedback loop trying to decrease or increase dutycycle)
(lossy but it might solve some matters is seperate all outputs from the common output by a diode so you're actualy certain you measure the right output)
For leadacid battery's we build chargers (microprocessor controlled) upto 100 ampere's .
did you consider a conventional supply with microcontroller (current & voltage measuring) with thyristors for switching of charge (rectification)
Goodluck 🙂
High Power SMPS
actually what I want is theory
suppose 5 different power supplys ( any topology linear SMPS flyback/forword any methode ) of different max current limit but with same o/p voltage say about +/- 1% are connected across lead acid battery.
initialy when battery is fully discharged each PSU will deliver its max. current, when battery voltage reaches a certain level one after another all PSU
will come out of constant current mode but still there o/p voltage will be same equal to battery voltage. During this periode battery current is continuously reducing & will
reach to a level which will decided by O/P voltage setting of all these PSUs.
I am using this methode of charging lead ACID batteries but with only one / two PSUs
Normaly I do this to increase charging current of customer UPS system I just add my SMPS Charger across there Battery this works fine, of course those UPS systems are made by me. All these systems have same charging methode a CVCC power cupply with O/P voltage 13.7 Volts. Some very old systems have linear supply with 723 voltage regulator type & some have fly back SMPS with TOP Switch. I never had any problem adding another SMPS charger across battery.
I want extend it further to make high current chargers
actually what I want is theory
suppose 5 different power supplys ( any topology linear SMPS flyback/forword any methode ) of different max current limit but with same o/p voltage say about +/- 1% are connected across lead acid battery.
initialy when battery is fully discharged each PSU will deliver its max. current, when battery voltage reaches a certain level one after another all PSU
will come out of constant current mode but still there o/p voltage will be same equal to battery voltage. During this periode battery current is continuously reducing & will
reach to a level which will decided by O/P voltage setting of all these PSUs.
I am using this methode of charging lead ACID batteries but with only one / two PSUs
Normaly I do this to increase charging current of customer UPS system I just add my SMPS Charger across there Battery this works fine, of course those UPS systems are made by me. All these systems have same charging methode a CVCC power cupply with O/P voltage 13.7 Volts. Some very old systems have linear supply with 723 voltage regulator type & some have fly back SMPS with TOP Switch. I never had any problem adding another SMPS charger across battery.
I want extend it further to make high current chargers
From what i read you charge your battery the wrong method .
13.7 volt is what you use for wet lead antimone accu's .
Further you say its for ups systems which makes me think its a dryfit ca or gel battery .
27.2 volt tell's that you probably charge battery's connected in series.
Let me try to stick to this order .
First the method of charging & the amperage of charging .
Let assume for now its a normal wet lead antimone accu .
Conservative advice is to charge at 5% of its Ah rating 100 Ah battery means 5 Ampere charging .
Common acceptable faster charging is 10 % being 10 Ampere .
That is for *dumb* charging .
You can charge with higher currents IF you keep a close eye on the charging proces .
If you don,t monitor you will lose to much elektrolyte by gassing and damage the battery .
Start with bulk charging at your maximum amount of available amperes .
When the battery reaches its gassingpoint you lower the voltage for absorbtion charge .
But still 70 Ampere is for BIIIIIIG battery's .
I can tell you from experience battery's can have boiling elektrolytes if you over do this with all the consequences of that (read acid foam over the floor etc. etc.)
http://www.victronenergy.com/upload/documents/User manual Blue Power Charger IP20.pdf
http://www.victronenergy.com/upload/documents/Book-EN-EnergyUnlimited.pdf
HAve a look at the first link for the graphic showed there .
then go to the second link and read page 11 to 22 😀
(sorry i cant help that ,but this is a relative good explanation they do know more about battery's then i do)
Brings me to the second point you charge with the voltage for wet accu's where i suspect you to use gel accu's or dryfit ca .
They need different (higher) voltages as you will see in the book power unlimited every battery has his own optimal charging voltage & function .
What i mean is this if you want the battery's to live try to make a charger suitable for the task & battery type .
Brings me to my last point battery's in serie .
Battery's in serie is in itself not advisable although also not impossible .
But you would have to *pair* battery's straight out of the box before they are builded in you pick the most identical battery's from the box and after lets say a year you will see that there is already a imbalance between your accu's ,charging them in serie will only increase the speed of that proces (sorry).
It would be better to build a double charger for that (2 x 13.7 or 14.4 volt depending on type )
If you want (or have) to use chargers that big ,implement current sensing (like with a acs750 + micro controller) & voltage regulation .
Don't count on current & voltage regulation of the top series cause its not an advisable way of handling battery's .
Yes it works no its not good for youre accu's ,you aint getting vallue for youre money and their life expectation will fall short
Not to mention that a wooden floor is advisable cause they corrode less with acid accidents
🙄
Goodluck .
13.7 volt is what you use for wet lead antimone accu's .
Further you say its for ups systems which makes me think its a dryfit ca or gel battery .
27.2 volt tell's that you probably charge battery's connected in series.
Let me try to stick to this order .
First the method of charging & the amperage of charging .
Let assume for now its a normal wet lead antimone accu .
Conservative advice is to charge at 5% of its Ah rating 100 Ah battery means 5 Ampere charging .
Common acceptable faster charging is 10 % being 10 Ampere .
That is for *dumb* charging .
You can charge with higher currents IF you keep a close eye on the charging proces .
If you don,t monitor you will lose to much elektrolyte by gassing and damage the battery .
Start with bulk charging at your maximum amount of available amperes .
When the battery reaches its gassingpoint you lower the voltage for absorbtion charge .
But still 70 Ampere is for BIIIIIIG battery's .
I can tell you from experience battery's can have boiling elektrolytes if you over do this with all the consequences of that (read acid foam over the floor etc. etc.)
http://www.victronenergy.com/upload/documents/User manual Blue Power Charger IP20.pdf
http://www.victronenergy.com/upload/documents/Book-EN-EnergyUnlimited.pdf
HAve a look at the first link for the graphic showed there .
then go to the second link and read page 11 to 22 😀
(sorry i cant help that ,but this is a relative good explanation they do know more about battery's then i do)
Brings me to the second point you charge with the voltage for wet accu's where i suspect you to use gel accu's or dryfit ca .
They need different (higher) voltages as you will see in the book power unlimited every battery has his own optimal charging voltage & function .
What i mean is this if you want the battery's to live try to make a charger suitable for the task & battery type .
Brings me to my last point battery's in serie .
Battery's in serie is in itself not advisable although also not impossible .
But you would have to *pair* battery's straight out of the box before they are builded in you pick the most identical battery's from the box and after lets say a year you will see that there is already a imbalance between your accu's ,charging them in serie will only increase the speed of that proces (sorry).
It would be better to build a double charger for that (2 x 13.7 or 14.4 volt depending on type )
If you want (or have) to use chargers that big ,implement current sensing (like with a acs750 + micro controller) & voltage regulation .
Don't count on current & voltage regulation of the top series cause its not an advisable way of handling battery's .
Yes it works no its not good for youre accu's ,you aint getting vallue for youre money and their life expectation will fall short
Not to mention that a wooden floor is advisable cause they corrode less with acid accidents
🙄
Goodluck .
High Power Charger
Batteries i am going to charge are traction batteries minimum 500 AH rating & O/P voltage 13.6 is not fixed it will change according to battery type .
My concern is can I parallal 2/3/4 no of CVCC Power supplies to charge battery in float charging mode
Batteries i am going to charge are traction batteries minimum 500 AH rating & O/P voltage 13.6 is not fixed it will change according to battery type .
My concern is can I parallal 2/3/4 no of CVCC Power supplies to charge battery in float charging mode
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