Posted by RamRod Sword of Baal on May 22, 2008, 4:20 pm
>> Has anyone seen such a thing (DC Voltage stabilizer), and knows where I
>> can
>> get one, or has a circuit diagram for something like this?
>>
>> I have not been able to find anything using Google.
> What I use is a Regulated DC Power Supply, as a Battery Charger.
> I set the Output Voltage of the Regulator, to what I figure should
> be Float Voltage, for the battery type, Minus .3 Vdc. I have a
> pair of L16HD's, in series, that supply the 12 Vdc Buss that runs my
> Radioroom/Office. Using a Regulated Dc Power Supply with the Output
> Voltage set at 13.3 Vdc, and capable of supplying 40 amps. My Base
> Load is usually in the neighborhood of 7 Amps, and jumps to Max of
> 50 amps, when one of the Transmitters is operating. The Battery
> Bank will support the load thru ANY Communication Session, and will then
> be recharged back to float, within a few hours after heavy use, all
> while maintaining a Buss Voltage, above 12.3 Vdc. Since I generate
> ALL my own power, and the genset only runs 10 hours a day, and the
> Regulated Power Supply, is not powered unless the Genset is online,
> this keeps my Radioroom/Office running 24/7/365, and the Battery
> Bank fully charged, and back at Float Voltage, at least twice a day.
> The only difference between your cheap Battery Charger, and my Regulated
> DC Power Supply, is the Voltage Regulation Circuits my unit has, after
> the Rectifier.
> --
> Bruce in alaska
> add <path> after <fast> to reply
---------------------------------
Thanks Bruce, sorry I have been so long in coming back to you, but I have
been travelling in Australia's outback, now in Sydney and heading back up
North to the warmth tomorrow, take me 3 days driving. Here of course it is
warmer North than South, where you are.
I live in the tropics hating the cold, only came into Sydney for a few days
to buy a few things and see some friends.
I hope to talk to a friend here tomorrow morning before I depart, he is
quite into electronics, and I am hoping he can help me with a design for
something like a 24 volt, 40 to 50 amp DC voltage stabilizer design that I
will attempt to build when I get home. Hopefully I can manage a stabilize
output voltage of around 26.5 - 27 volts.
I will feed it from my heavy (not cheap <G>) battery charger, if necessary I
can increase the voltage from the charger to feed the voltage stabilizer.
I am not a wiz kid on electronics, but willing to have a go, hoping I can
keep the smoke inside the components. :-)
A couple of years ago I came across a commercially build one on the net, but
alas I cannot find it now, and have done quite a few googles trying to find
it.
Thanks for the help
=======================================================
Original message
> I have a particular set up for powering my computers. We are on mains
> power (Australia 240 volts 50 cycles) but I have a system for running the
> computers, it has 4 x 6 volt T105 batteries (24 volt ) and a 2500 watt
> inverter.
> There are as many as 9 computers can be put on line, but in actual fact
> normally it would only be 2 or possibly 3, depending what is happening in
> the house. I cannot see where we would ever have as many as 5 running at
> one time.
> The system allows for running a TV and fridge in case of a power failure.
> The power for the batteries comes from a simple 40 amp 24 volt charger, it
> is a transformer and rectifier. It is a solidly built unit that I had made
> for the job.
> I also had a 25 amp electronic charger but it has failed and needs repair
> or replacement.
> These large chargers are quite expensive here in Australia, for instance a
> 24 volt 25 amp charger can run up above $1000.00.
> The inverter is a sinewave job and cost $2500.00 so any idea of throwing
> away what I have and replacing it is not on.
> Now comes the problem. The battery charger being only a simple battery
> charger need the battery voltage to drop quite a bit before you can get a
> large current out of it. I want to maintain around 27 volts in the
> batteries and have the charger put in what ever the inverter is dragging
> out, so if the inverter is using say 20 amps, I need to put in 20 amps,
> plus a small maintenace charge for the batteries and maintain the 27 volts
> in the batteries, so I am not constantly draining and recharging the
> batteries thus reducing their life.
> I have seen one of these devices in the past, but unfortunately lost the
> link.
> It is an electronic 'box of tricks' rated around 40 amps that you can put
> is a DC voltage and get out a constant dc voltage.
> As I can increase the DC voltage from my current simple battery charger to
> up over 40 volts if I so desire, I am looking at buying something that
> would give me a constant or near constant 27 volts, and rated at 40 amps
> output to maintain the batteries at full charge. Of course the 'box of
> tricks' needs to modulate the current to maintain the 27 volts in the
> system between 0 and 40 amps
> I understand it might not be able to hold it at exactly 27 volts, but it
> would want it to be somewhere near that number.
> At the moment I seem to be having the problem of either pulling power out
> of the batteries or over charging them, depending on what setting I use on
> the battery charger.
> Has anyone seen such a thing (DC Voltage stabilizer), and knows where I
> can get one, or has a circuit diagram for something like this?
> I have not been able to find anything using Google.
> I should have made the point that I want to use the DC power from my
> current
> simple battery charger to feed into a DC to DC voltage stabilizer.
Posted by Eric Sears on May 22, 2008, 6:53 pm
On Fri, 23 May 2008 06:20:45 +1000, "RamRod Sword of Baal"
>Thanks Bruce, sorry I have been so long in coming back to you, but I have
>been travelling in Australia's outback, now in Sydney and heading back up
>North to the warmth tomorrow, take me 3 days driving. Here of course it is
>warmer North than South, where you are.
>I live in the tropics hating the cold, only came into Sydney for a few days
>to buy a few things and see some friends.
>I hope to talk to a friend here tomorrow morning before I depart, he is
>quite into electronics, and I am hoping he can help me with a design for
>something like a 24 volt, 40 to 50 amp DC voltage stabilizer design that I
>will attempt to build when I get home. Hopefully I can manage a stabilize
>output voltage of around 26.5 - 27 volts.
>I will feed it from my heavy (not cheap <G>) battery charger, if necessary I
>can increase the voltage from the charger to feed the voltage stabilizer.
>I am not a wiz kid on electronics, but willing to have a go, hoping I can
>keep the smoke inside the components. :-)
>A couple of years ago I came across a commercially build one on the net, but
>alas I cannot find it now, and have done quite a few googles trying to find
>it.
>Thanks for the help
Hi
The thing you want is a simple linear regulator circuit using pass
transistors. Probably today you might use FETs, though the old bipolar
transistors were pretty rugged.
The back of the old Dick Smith catalogue (for both Aust and NZ) used
to have a circuit of a three-terminal regulator with wrap-around
transistors to give it greater current capacity. This could be scaled
up to 40 amps by adding more transistors on heat sinks. Even 2N3055s
would work if you had enough of them (You would probably need about 8
for reliability). There will be considerably heat dissipation.
Try googling "linear regulator circuit" or just "regulator circuit".
If you use an adjustable 3-terminal regulator, (LM317??) you could set
it to say 26.5v and the battery would sit at that voltage on float,
with the current effectively coming from the power supply, unless the
charging stopped - in which case the battery would take the load.
The use of diodes (to isolate the battery) with such heavy loads,
especially the start-up surge of the fridge, could make that a bit
difficult. I would just leave the battery floating on the supply, and
raise the voltage once a month (to say 29v) to give it an equalising
charge for a few hours.
Eric Sears.
Posted by Dale Eastman on May 27, 2008, 8:44 pm
RamRod Sword of Baal wrote:
> I hope to talk to a friend here tomorrow morning before I depart, he is
> quite into electronics, and I am hoping he can help me with a design for
> something like a 24 volt, 40 to 50 amp DC voltage stabilizer design that I
> will attempt to build when I get home. Hopefully I can manage a stabilize
> output voltage of around 26.5 - 27 volts.
>
>
>
> I will feed it from my heavy (not cheap <G>) battery charger, if necessary I
> can increase the voltage from the charger to feed the voltage stabilizer.
>
>
Adjustable voltage regulator:
http://home.sprintmail.com/~dalereastman/images/LM309.GIF
From:
Master Handbook of 1001 Practical Electrical Circuits
TAB BOOKS c 1975:
2 to 36 volt power supply 10 amps:
http://home.sprintmail.com/~dalereastman/images/2to36volt10amp.jpg
Notice that the output is a pair of parallel transistors at 5 amps each.
Find the base current for Q3 and/or Q4 and divide the max current for Q2
by that amount to calculate how many output transistors you could
parallel to increase the output.
My two cents on the fly. Good luck.
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>> can
>> get one, or has a circuit diagram for something like this?
>>
>> I have not been able to find anything using Google.
> What I use is a Regulated DC Power Supply, as a Battery Charger.
> I set the Output Voltage of the Regulator, to what I figure should
> be Float Voltage, for the battery type, Minus .3 Vdc. I have a
> pair of L16HD's, in series, that supply the 12 Vdc Buss that runs my
> Radioroom/Office. Using a Regulated Dc Power Supply with the Output
> Voltage set at 13.3 Vdc, and capable of supplying 40 amps. My Base
> Load is usually in the neighborhood of 7 Amps, and jumps to Max of
> 50 amps, when one of the Transmitters is operating. The Battery
> Bank will support the load thru ANY Communication Session, and will then
> be recharged back to float, within a few hours after heavy use, all
> while maintaining a Buss Voltage, above 12.3 Vdc. Since I generate
> ALL my own power, and the genset only runs 10 hours a day, and the
> Regulated Power Supply, is not powered unless the Genset is online,
> this keeps my Radioroom/Office running 24/7/365, and the Battery
> Bank fully charged, and back at Float Voltage, at least twice a day.
> The only difference between your cheap Battery Charger, and my Regulated
> DC Power Supply, is the Voltage Regulation Circuits my unit has, after
> the Rectifier.
> --
> Bruce in alaska
> add <path> after <fast> to reply