Power supply and battery connected together?

[Shadetree Mechanic]

Here is a link to a site with a ton of information. Although it is geared towards car audio, it has a lot of info about electrical and electronics and is a great resource for reference.
http://www.bcae1.com/charging.htm

 

[Cutlass327]

So basically if I turn the volts on the p/s to 13.6v, it is safe for the battery?

 

[Shadetree Mechanic]

So basically if I turn the volts on the p/s to 13.6v, it is safe for the battery?

It would be fine for the battery, the power supply is a different story. Does the power supply specify that it can charge batteries? Maybe all switch mode supplies are ok or maybe just certian ones, I don't know. My Trip Lite power supply did not like it at all.

 

[StrangeBrew]

Battery chargers are usually regulated to put out a constant current as well as constant voltage, on a power supply it's usually only the voltage that's regulated. If a battery is low the current it draws could be too much for the supply to handle.

 

[Captain Kilowatt]

Personally I would not use a power supply and battery in parallel. Too much to go wrong. Off gassing of hydrogen, corrosive gasses, no ability to limit initial charging current, ideal battery charging voltage is a bit over 14 volts so most power supplies will not fully charge a battery which is not good for the battery long term, risk of acid spill. Nope.......use a battery charger outside the shack or get a proper power supply.

 

[Tallman]

Battery chargers are usually regulated to put out a constant current as well as constant voltage, on a power supply it's usually only the voltage that's regulated. If a battery is low the current it draws could be too much for the supply to handle.

Actually that depends on the type of battery being charged. Lead acid batteries are charged with constant voltage although the current may vary.
Ni-Cad batteries and Lithium are constant current types, but in reality both current and voltage change during the charging process. I have multi-rotor camera platforms AKA drones. The lithium ION batteries are charged with a complex computerized charger.
A lot of detail I won't go into but you set the number of cells, battery chemistry, and the charge rate and hit the start button. When finished the battery is perfectly peaked and at maximum capacity. The lithium cells have a charge level they need to be at for storage and so do the NI-cads.

 

[Captain Kilowatt]

Actually that depends on the type of battery being charged. Lead acid batteries are charged with constant voltage although the current may vary.
Ni-Cad batteries and Lithium are constant current types, but in reality both current and voltage change during the charging process.

Exactly. Current control and limiting is actually accomplished by controlling the charging voltage. Less applied voltage equals less current. I used to charge AGM batteries using a variable voltage power supply that had current limiting. I would first set the desired output voltage for a fulll charge and then turn thge current limiting control all the way down and short the output leads together and adjust the current control for maximum charge current. With a dead short this would typically be be less that 2 volts. When the leads were connected to the battery the current would be limited to the maximum charge current I set the supply for and it would remain constant as the battery charged. As the voltage came up on the battery the supply would ramp up the voltage to maintain the same current until it reach the preset value and then as the battery neared a full charge the voltage would remain constant while the current slowly dropped to top off and maintain a full charge. I wouldn't use a power supply without current limiting to charge a battery.

 

[Shadetree Mechanic]

Current limiting is not needed unless you plan on deep discharge cycles. If running the system with the supply on it would not be a problem. Just make sure that your time off key is more than on key. The car alternator doesnt have current limiting.

 

[Mustang 131]

I bought a well used 250amp battery charger as into pair of 8v scrubber batteries in series. In "start" mode it ran about 17vdc into the batteries...Did that for many years. Just keep the batteries outside! If you hear any AC..add water.
I remember whole setup cost me $50. Still have the charger.

 

[Captain Kilowatt]

Current limiting is not needed unless you plan on deep discharge cycles. If running the system with the supply on it would not be a problem. Just make sure that your time off key is more than on key. The car alternator doesnt have current limiting.

True but your alternator is capable of delivering perhaps up to 200 amps depending on the unit. It would be quite inadvisable to have a battery pretty much discharged and connected to a 30 amp power supply. I guarantee the power supply will not like it.

 

[Handy Andy]

Boy, I guess I'm behind the times...

I used to use Batteries as much like a filter capacitor - I put the battery in past the rectifier - but before the regulation section.

That way, the older style Battery charger method worked as it made the battery able to charge up, but as it obtained more charge - the rectifiers took on the task of recharging to more of a low-level sustaining because of the battery now acting more like a capacitor than a resistive load.

The concept here was to use a smaller transformer like those at R/Shack that had the 18V CT winds - gave you easily 19~25VDC but only 2.5 Amps output at the most - it worked well for loading - because the secondary just didn't have a lot of amps to push into the battery+Supply. I did this so I can keep overcharge rates low so the batteries didn't waste a lot of gassing - so You'd let the battery charge and as it's "float level" rose - the secondary power would also rise and you'd start to see ripple and higher output from the secondary - but the batteries own loading across the bridge rectifier - kept the secondary under enough load to keep the ripple voltage low enough not to exceed the linear power supply input (usually 35 to 36 volts I used LM337 and 78XX series for an older computer drive tower for SCSI drives).

I used two batteries or three if I need -5VDC to provide TTL drive - the 12V simple car battery and a couple of smaller 6V Lawnmower types with "ground" of two (one 6V + one 12V =18V in series) ties to Positive of separate 6V and it's negative to provide the linear negative logic level TTL - the bane was having to use separate wind of another simple secondary to apply the charger to the negative supply - ran some ripple noise issues and then came across an old Tripp-Lite type that had separate power supply secondary winds, one used for their logic board and another for the 1218V side - upon experimentation easily output over 36 volts - and my world smoothed out from there once I used a single "iron" and got all my secondary's tied in proper phase to make the unit charge 18VDC (the two battery tied side - used a modified 5V and 12V 78XX series and I used the LM337 to charge the negative side.

I set it up as more of a stop gap to keep the SCSI drives working on a separate feed - for the intent was to make up a battery supply using a solar charger or portable generator to offset the power needs of older 386 - AT/XT style systems as more of a remote operation "standalone" - which became moot once Laptops became the rage...

So I can see where someone can get the notion that it is possible - simply based on the ideas of how a simple battery charger works, but the complexity rises rapidly once you try to figure out how much resistance a battery shows to the system as a resistive load across it's terminals so the transformer you use is effective yet not there to spike the equipment one the battery is charged up.

I do find it interesting the concept of the battery packs used in todays laptops are of similar design of cell packing and "tap points" to obtain the voltages and currents necessary for those power levels - only now in lithium and Ni-Cad/Ni-MH

And that can also tell you it was a long time ago...

 

[Rwb]

Boy, I guess I'm behind the times...

I used to use Batteries as much like a filter capacitor - I put the battery in past the rectifier - but before the regulation section.

That way, the older style Battery charger method worked as it made the battery able to charge up, but as it obtained more charge - the rectifiers took on the task of recharging to more of a low-level sustaining because of the battery now acting more like a capacitor than a resistive load.

The concept here was to use a smaller transformer like those at R/Shack that had the 18V CT winds - gave you easily 19~25VDC but only 2.5 Amps output at the most - it worked well for loading - because the secondary just didn't have a lot of amps to push into the battery+Supply. I did this so I can keep overcharge rates low so the batteries didn't waste a lot of gassing - so You'd let the battery charge and as it's "float level" rose - the secondary power would also rise and you'd start to see ripple and higher output from the secondary - but the batteries own loading across the bridge rectifier - kept the secondary under enough load to keep the ripple voltage low enough not to exceed the linear power supply input (usually 35 to 36 volts I used LM337 and 78XX series for an older computer drive tower for SCSI drives).

I used two batteries or three if I need -5VDC to provide TTL drive - the 12V simple car battery and a couple of smaller 6V Lawnmower types with "ground" of two (one 6V + one 12V =18V in series) ties to Positive of separate 6V and it's negative to provide the linear negative logic level TTL - the bane was having to use separate wind of another simple secondary to apply the charger to the negative supply - ran some ripple noise issues and then came across an old Tripp-Lite type that had separate power supply secondary winds, one used for their logic board and another for the 1218V side - upon experimentation easily output over 36 volts - and my world smoothed out from there once I used a single "iron" and got all my secondary's tied in proper phase to make the unit charge 18VDC (the two battery tied side - used a modified 5V and 12V 78XX series and I used the LM337 to charge the negative side.

I set it up as more of a stop gap to keep the SCSI drives working on a separate feed - for the intent was to make up a battery supply using a solar charger or portable generator to offset the power needs of older 386 - AT/XT style systems as more of a remote operation "standalone" - which became moot once Laptops became the rage...

So I can see where someone can get the notion that it is possible - simply based on the ideas of how a simple battery charger works, but the complexity rises rapidly once you try to figure out how much resistance a battery shows to the system as a resistive load across it's terminals so the transformer you use is effective yet not there to spike the equipment one the battery is charged up.

I do find it interesting the concept of the battery packs used in todays laptops are of similar design of cell packing and "tap points" to obtain the voltages and currents necessary for those power levels - only now in lithium and Ni-Cad/Ni-MH

And that can also tell you it was a long time ago...

easy now Handy Andy your giving our ages away

 

[Cutlass327]

This is the battery I am using.

 

[loosecannon]

we do this at work with our 48v power supplies to ensure that we don't have a glitch if we lose a power supply.

of course the power supplies are designed for it and monitor the battery charge.

your supply needs to be able to supply all the current needed, and the batteries are just loafing along.

we use sealed gel cells, like the ones you would find in your home alarm system.
LC

 

[Cutlass327]

OK, here's a question. I was looking thru the swap-shop section, seeing if I could find an affordable used 50+ amp power supply, and I found one thread selling a Megawatt 50A supply because of the loud fan. In it, they were talking about paralleling 2 p/s units. How would I know if I could parallel another one of these 30A units, or should I just keep looking for that evasive good deal on a used unit? Seems like nobody is selling anything used over 10A anywhere...

MegaWatt S-700-12 switching power supply