|
Can someone tell me what DC power supply and maps per hour to use for the Bitx v6? Does 12 volts need to be stepped down to a certain value?
|
a 7amp hr sealed lead acid 12 volt battery with a 2 or 3 amp fuse does a very nice job.
Gordon
Can someone tell me what DC power supply and maps per hour to use for the Bitx v6? Does 12 volts need to be stepped down to a certain value?
|
Thank you.
Sent via the Samsung Galaxy A10e, an AT&T 4G LTE smartphone
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-------- Original message -------- From: Gordon Gibby <docvacuumtubes@...> Date: 6/21/20 2:34 PM (GMT-06:00) Subject: Re: [BITX20] Power supply
a 7amp hr sealed lead acid 12 volt battery with a 2 or 3 amp fuse does a very nice job.
Gordon
Can someone tell me what DC power supply and maps per hour to use for the Bitx v6? Does 12 volts need to be stepped down to a certain value?
|
Keep in mind that those batteries that are lead-acid when fully charged are closer to 13.6V but that comes down to closer to 12V after some current draw. Therefore, a better question, for my part, is whether the V6 can be run with confidence with 13.6V or should it be run only at about 12V? This is an important question to me since I will either be using a cheap batter like for a lawn mower that runs about $25 at Wally World or an emergency light gell cell which is about the same except without the liquid in the cells like in a simple lawn motor battery.
On a uBITX for 40M I had before, I had some series 1A diodes to lower the applied voltage to the main board while keeping the two amplifier transistors at the higher 13.6V (brown wire) which may not have been necessary.
In my case, perhaps a better way to get to the meat of the matter is to ask, what is the maximum voltage that can be safely applied to a V6...?
On Sunday, June 21, 2020, 3:34:25 PM EDT, Gordon Gibby <docvacuumtubes@...> wrote:
a 7amp hr sealed lead acid 12 volt battery with a 2 or 3 amp fuse does a very nice job.
Gordon
Can someone tell me what DC power supply and maps per hour to use for the Bitx v6? Does 12 volts need to be stepped down to a certain value?
|
I run my v5 at 13.8 from a regulated supply with no problems .
73,
Ora
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On Jun 21, 2020, at 10:45 PM, Bob Lunsford via groups.io <nocrud222@...> wrote:
?
Keep in mind that those batteries that are lead-acid when fully charged are closer to 13.6V but that comes down to closer to 12V after some current draw. Therefore, a better question, for my part, is whether the V6 can be run with confidence with 13.6V or should it be run only at about 12V? This is an important question to me since I will either be using a cheap batter like for a lawn mower that runs about $25 at Wally World or an emergency light gell cell which is about the same except without the liquid in the cells like in a simple lawn motor battery.
On a uBITX for 40M I had before, I had some series 1A diodes to lower the applied voltage to the main board while keeping the two amplifier transistors at the higher 13.6V (brown wire) which may not have been necessary.
In my case, perhaps a better way to get to the meat of the matter is to ask, what is the maximum voltage that can be safely applied to a V6...?
On Sunday, June 21, 2020, 3:34:25 PM EDT, Gordon Gibby <docvacuumtubes@...> wrote:
a 7amp hr sealed lead acid 12 volt battery with a 2 or 3 amp fuse does a very nice job.
Gordon
Can someone tell me what DC power supply and maps per hour to use for the Bitx v6? Does 12 volts need to be stepped down to a certain value?
|
hi bob -- I understand your point, but i must just purchase?crappy sealed lead acids....mine NEVER make it to 13.6.? ?They hang out in the 12's.? ?It is also HOT here in Florida.? That reduces the voltage a bit.? ? ? I would prefer with a bitx product to stay below 13 and my poor batteries have obliged nicely? (grin!)
Gordon
On Sun, Jun 21, 2020 at 10:46 PM Bob Lunsford via <nocrud222= [email protected]> wrote:
Keep in mind that those batteries that are lead-acid when fully charged are closer to 13.6V but that comes down to closer to 12V after some current draw. Therefore, a better question, for my part, is whether the V6 can be run with confidence with 13.6V or should it be run only at about 12V? This is an important question to me since I will either be using a cheap batter like for a lawn mower that runs about $25 at Wally World or an emergency light gell cell which is about the same except without the liquid in the cells like in a simple lawn motor battery.
On a uBITX for 40M I had before, I had some series 1A diodes to lower the applied voltage to the main board while keeping the two amplifier transistors at the higher 13.6V (brown wire) which may not have been necessary.
In my case, perhaps a better way to get to the meat of the matter is to ask, what is the maximum voltage that can be safely applied to a V6...?
a 7amp hr sealed lead acid 12 volt battery with a 2 or 3 amp fuse does a very nice job.
Gordon
Can someone tell me what DC power supply and maps per hour to use for the Bitx v6? Does 12 volts need to be stepped down to a certain value?
|
You dont have to grinn.? We have friends at hyderabad, india reaching? indonesia with 8 to 10w aith a direct ubitx.?
Be sure that you can optimize and ruggedize your antenna? with minimum feeder loss. You surely enjoy rhe qsos?
Regards Sarma vu3zmv
hi bob -- I understand your point, but i must just purchase?crappy sealed lead acids....mine NEVER make it to 13.6.? ?They hang out in the 12's.? ?It is also HOT here in Florida.? That reduces the voltage a bit.? ? ? I would prefer with a bitx product to stay below 13 and my poor batteries have obliged nicely? (grin!)
Gordon
On Sun, Jun 21, 2020 at 10:46 PM Bob Lunsford via <nocrud222= [email protected]> wrote:
Keep in mind that those batteries that are lead-acid when fully charged are closer to 13.6V but that comes down to closer to 12V after some current draw. Therefore, a better question, for my part, is whether the V6 can be run with confidence with 13.6V or should it be run only at about 12V? This is an important question to me since I will either be using a cheap batter like for a lawn mower that runs about $25 at Wally World or an emergency light gell cell which is about the same except without the liquid in the cells like in a simple lawn motor battery.
On a uBITX for 40M I had before, I had some series 1A diodes to lower the applied voltage to the main board while keeping the two amplifier transistors at the higher 13.6V (brown wire) which may not have been necessary.
In my case, perhaps a better way to get to the meat of the matter is to ask, what is the maximum voltage that can be safely applied to a V6...?
a 7amp hr sealed lead acid 12 volt battery with a 2 or 3 amp fuse does a very nice job.
Gordon
Can someone tell me what DC power supply and maps per hour to use for the Bitx v6? Does 12 volts need to be stepped down to a certain value?
|
FANTASTIC!? ?I was grinning about my less-than-perfect-batteries --- but they have served me very very well over the years!
Thanks, Gordon
On Mon, Jun 22, 2020 at 4:12 AM MVS Sarma < mvssarma@...> wrote: You dont have to grinn.? We have friends at hyderabad, india reaching? indonesia with 8 to 10w aith a direct ubitx.?
Be sure that you can optimize and ruggedize your antenna? with minimum feeder loss. You surely enjoy rhe qsos?
Regards Sarma vu3zmv
hi bob -- I understand your point, but i must just purchase?crappy sealed lead acids....mine NEVER make it to 13.6.? ?They hang out in the 12's.? ?It is also HOT here in Florida.? That reduces the voltage a bit.? ? ? I would prefer with a bitx product to stay below 13 and my poor batteries have obliged nicely? (grin!)
Gordon
On Sun, Jun 21, 2020 at 10:46 PM Bob Lunsford via <nocrud222= [email protected]> wrote:
Keep in mind that those batteries that are lead-acid when fully charged are closer to 13.6V but that comes down to closer to 12V after some current draw. Therefore, a better question, for my part, is whether the V6 can be run with confidence with 13.6V or should it be run only at about 12V? This is an important question to me since I will either be using a cheap batter like for a lawn mower that runs about $25 at Wally World or an emergency light gell cell which is about the same except without the liquid in the cells like in a simple lawn motor battery.
On a uBITX for 40M I had before, I had some series 1A diodes to lower the applied voltage to the main board while keeping the two amplifier transistors at the higher 13.6V (brown wire) which may not have been necessary.
In my case, perhaps a better way to get to the meat of the matter is to ask, what is the maximum voltage that can be safely applied to a V6...?
a 7amp hr sealed lead acid 12 volt battery with a 2 or 3 amp fuse does a very nice job.
Gordon
Can someone tell me what DC power supply and maps per hour to use for the Bitx v6? Does 12 volts need to be stepped down to a certain value?
|
Hi,
The direct answer to your question is *yes*. Not even a qualified yes. I operate *all* of my "twelve volt" gear on thirteen point eight volts (or a little more. That includes my uBitx.
More info - The "12" volt automotive electrical voltage specification allows up to 15 volts (it did when I was young) and still gets up to 14 volts (or so). It can drop to around 10 volts at discharged. That 13.8 number is a "nominal" which means a "name" for the average charging voltage. That 15 volts was the recommended limit for adjustment of the mechanical voltage regulators. We used to run with the headlights on - not for safety - but to pull the system voltage down from that 15 (or more) volts. Voltages that high were hard on some of the parts including the battery. The battery need a drink of water frequently. 13.8 volts is trivial.
Now doomsday people can list all the "12 volt" radios that die instantly from 13.8 volts so I can make a list of radios to *never* buy (or even accept as a gift).
73,
Bill KU8H
bark less - wag more
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On 6/21/20 10:45 PM, Bob Lunsford via groups.io wrote: Keep in mind that those batteries that are lead-acid when fully charged are closer to 13.6V but that comes down to closer to 12V after some current draw. Therefore, a better question, for my part, is whether the V6 can be run with confidence with 13.6V or should it be run only at about 12V? This is an important question to me since I will either be using a cheap batter like for a lawn mower that runs about $25 at Wally World or an emergency light gell cell which is about the same except without the liquid in the cells like in a simple lawn motor battery.
On a uBITX for 40M I had before, I had some series 1A diodes to lower the applied voltage to the main board while keeping the two amplifier transistors at the higher 13.6V (brown wire) which may not have been necessary.
In my case, perhaps a better way to get to the meat of the matter is to ask, what is the maximum voltage that can be safely applied to a V6...?
On Sunday, June 21, 2020, 3:34:25 PM EDT, Gordon Gibby <docvacuumtubes@...> wrote:
a 7amp hr sealed lead acid 12 volt battery with a 2 or 3 amp fuse does a very nice job.
Gordon
On Sun, Jun 21, 2020 at 2:57 PM thomas.adair <thomas.adair@... <mailto:thomas.adair@...>> wrote:
Can someone tell me what DC power supply and maps per hour to use
for the Bitx v6? Does 12 volts need to be stepped down to a certain
value?
|
The TDA2822 audio amplifier integrated circuit on the original uBITx V6 is limited to 15 Volts.?
The LM386-N audio amplifier IC used later can tolerate 22 Volts.?
The maximum input voltage of the LM7805 voltage regulator is rated for 35 Volts no load,?
but is heat-limited to 20 Volts input at 1 Ampere rated output.?
The output power amplifier transistors are rated for 24 Volts.?
I do not recommend operating at more than 15 Volts input.?
My uBITx will draw 2.7 Amperes key-down at 13.8 Volts, and still operates at 9 Volts (with reduced output power).?
?
Note that healthy lead-acid batteries can rise to 14.2 Volts during rapid charging,??
and are typically 13.8 Volts during normal charging.?
Fully charged no-load voltage at room temperature is typically 12.7 volts,?
dropping to 12.2 Volts at 50 percent capacity, and 12.0 Volts at 25 percent capacity.?
Repeatedly discharging below 50 percent will significantly shorten the life of a lead-acid battery.?
?
|
Everyone seems to forget the LM78L05ACZ regulator, however, for this discussion, it is rated at 30 volts input, so also not an issue.
In the pre v6 kits, having to wire the separate power lines, I always put in a diode to drop the voltage to the mainboard. This was done as much for reducing the voltage drop across the Raduino 5 volt regulator as any of the other components.?
With the way that the power is supplied to the v6, it is now much harder to split off the power, so I would not do it for those rigs as N0YWB is suggesting.
YMMV
73
Evan?
|
Don't forget the V3 which had power supply issues with audio amp. V4 was changed to a discrete audio amp to mitigate this. V5 was changed to a more voltage tolerate audio amp.
Thanks!
On June 22, 2020, at 10:55 AM, Evan Hand <elhandjr@...> wrote:
Everyone seems to forget the LM78L05ACZ regulator, however, for this discussion, it is rated at 30 volts input, so also not an issue.
In the pre v6 kits, having to wire the separate power lines, I always put in a diode to drop the voltage to the mainboard. This was done as much for reducing the voltage drop across the Raduino 5 volt regulator as any of the other components.?
With the way that the power is supplied to the v6, it is now much harder to split off the power, so I would not do it for those rigs as N0YWB is suggesting.
YMMV
73
Evan?
|
I work for a phone company in maintenance. The fire alarm batteries get swapped out every 3 years need it or not. All of the batteries I use have been used for 3 years before I use them on the radios. If you know of a fire system company or maintenance people of buildings these are the people to ask. The batteries are scrap at that point and some people are strict about there scrap but the fire alarm people I deal with don't care that much, if you want one or two no problem. If you had an old one to swap fantastic. I have also found that?battery AH tester?at Aliexpress for a couple of dollars, I forget but under 5$. I use a tail light off of a car as a load. It runs the battery down to a certain voltage and cuts off. It then tells you how many amp-hours the battery will produce and give you an idea of how long it will last..Great for used batteries and to know what you have for field day 73, John This is the one I use. New ZB2L3 Li-ion Lithium Lead-acid Battery Capacity Meter Discharge Tester Analyzer Measurement Analysis Instruments??
--
¡°A single light can banish the darkness¡±
Lux e tenebris?
"A fool stares?at the finger that points at the moon"
I Ching
|
Hi,
I have a V3 here and I do run from a lead-acid battery. Some of mine reach above 13 at full charge. I do NOT charge while I am actually using any of the batteries. That can go higher than 14 volts sometimes and will affect the load (the radio). My V3 has one of the more robust versions of the audio amp IC. Some were junk. If mine does die a different IC will be hired:) I also used the lead-acid battery to power a few uBitx radios I have fixed for some other hams (varied models). It has never been a problem.
In the end the owner must decide. This thread has been in response to a question about power supplies and "12 volts". I think we all covered it.
73,
Bill KU8H
bark less - wag more
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On 6/22/20 11:11 AM, Allen Hill via groups.io wrote: Don't forget the V3 which had power supply issues with audio amp. V4 was changed to a discrete audio amp to mitigate this. V5 was changed to a more voltage tolerate audio amp.
Thanks!
On June 22, 2020, at 10:55 AM, Evan Hand <elhandjr@...> wrote:
Everyone seems to forget the LM78L05ACZ regulator, however, for this discussion, it is rated at 30 volts input, so also not an issue.
In the pre v6 kits, having to wire the separate power lines, I always put in a diode to drop the voltage to the mainboard. This was done as much for reducing the voltage drop across the Raduino 5 volt regulator as any of the other components.
With the way that the power is supplied to the v6, it is now much harder to split off the power, so I would not do it for those rigs as N0YWB is suggesting.
YMMV
73
Evan
|
I also run my V6 from a 13.8 Vdc switching power supply (jet stream jpts32mab) and I have not had any issues. -- ?
73
Mick VA3EPM?
|
Hi John,
I have rolled my own and have considered additional sophistication like what you describe. I have only four of those SLABs and I just pay attention to how long they run the radios before a swap is required. My idea was to use a power transistor as a current sink into a dead short and draw it down to the low set point while monitoring and recording the voltage. All while *I* do more interesting things. Pencils and graph paper on a clipboard with a clock demand a lot of attention. Been there- done that. An arduino controller would be ideal. They don't seem to get bored:)
73,
Bill KU8H
bark less - wag more
toggle quoted message
Show quoted text
On 6/22/20 11:33 AM, JohnR wrote: I work for a phone company in maintenance. The fire alarm batteries get swapped out every 3 years need it or not. All of the batteries I use have been used for 3 years before I use them on the radios. If you know of a fire system company or maintenance people of buildings these are the people to ask. The batteries are scrap at that point and some people are strict about there scrap but the fire alarm people I deal with don't care that much, if you want one or two no problem. If you had an old one to swap fantastic. I have also found that?battery AH tester?at Aliexpress for a couple of dollars, I forget but under 5$. I use a tail light off of a car as a load. It runs the battery down to a certain voltage and cuts off. It then tells you how many amp-hours the battery will produce and give you an idea of how long it will last..Great for used batteries and to know what you have for field day
73, John
This is the one I use.
New ZB2L3 Li-ion Lithium Lead-acid Battery Capacity Meter Discharge
Tester Analyzer Measurement Analysis Instruments
--
¡°A single light can banish the darkness¡±
/Lux e tenebris
"A fool stares?at the finger that points at the moon"
I Ching/
|
I have a v5 with the 2.8" Nextion screen.
I run off a 13.8V desktop supply at home with no problems.
For portable operation I use 12V rechargeable 3 Amp hour batteries from Talentcell..
I can run a whole day SSB on one charge.
73,
Dean
KK4DAS
Dean
|
I remember working in a foreign car garage in the late '60's and the cars there were Renaults and Peugeots among a few Japanese cars. The French cars recommended setting the mechanical voltage regulators at between 13.8 and 14.2 volts for charging purposes but this was also to compensate for the batteries frequently being placed at one end of the car and the motor starter/generator at the other end. Therefore, it was to compensate for voltage drop in the battery cable. Also, if the voltage was too high, it tended to boil out the water in the battery but when this happened, you could smell it.
Bob ¡ª KK5R
On Monday, June 22, 2020, 9:38:42 AM EDT, Bill Cromwell <wrcromwell@...> wrote:
Hi,
The direct answer to your question is *yes*. Not even a qualified yes. I
operate *all* of my "twelve volt" gear on thirteen point eight volts (or
a little more. That includes my uBitx.
More info - The "12" volt automotive electrical voltage specification
allows up to 15 volts (it did when I was young) and still gets up to 14
volts (or so). It can drop to around 10 volts at discharged. That 13.8
number is a "nominal" which means a "name" for the average charging
voltage. That 15 volts was the recommended limit for adjustment of the
mechanical voltage regulators. We used to run with the headlights on -
not for safety - but to pull the system voltage down from that 15 (or
more) volts. Voltages that high were hard on some of the parts including
the battery. The battery need a drink of water frequently. 13.8 volts is
trivial.
Now doomsday people can list all the "12 volt" radios that die instantly
from 13.8 volts so I can make a list of radios to *never* buy (or even
accept as a gift).
73,
Bill? KU8H
bark less - wag more
On 6/21/20 10:45 PM, Bob Lunsford via groups.io wrote: > Keep in mind that those batteries that are lead-acid when fully charged > are closer to 13.6V but that comes down to closer to 12V after some > current draw. Therefore, a better question, for my part, is whether the > V6 can be run with confidence with 13.6V or should it be run only at > about 12V? This is an important question to me since I will either be > using a cheap batter like for a lawn mower that runs about $25 at Wally > World or an emergency light gell cell which is about the same except > without the liquid in the cells like in a simple lawn motor battery. > > On a uBITX for 40M I had before, I had some series 1A diodes to lower > the applied voltage to the main board while keeping the two amplifier > transistors at the higher 13.6V (brown wire) which may not have been > necessary. > > In my case, perhaps a better way to get to the meat of the matter is to > ask, what is the maximum voltage that can be safely applied to a V6...? > > > On Sunday, June 21, 2020, 3:34:25 PM EDT, Gordon Gibby > < docvacuumtubes@...> wrote: > > > a 7amp hr sealed lead acid 12 volt battery with a 2 or 3 amp fuse does a > very nice job. > > Gordon > > > On Sun, Jun 21, 2020 at 2:57 PM thomas.adair < thomas.adair@... > <mailto: thomas.adair@...>> wrote: > >? ? Can someone tell me what DC power supply and maps per hour to use >? ? for the Bitx v6? Does 12 volts need to be stepped down to a certain >? ? value? > >
|
I've been planning to build an arduino based battery evaluator as well.
> My idea was to use a power transistor as a current sink into a dead short and draw it down to the low set point while monitoring and recording the voltage.
Be aware that a lead acid battery (SLAB = sealed lead acid battery) has a very low internal impedance.
A short could be hundreds or even thousands of amps, and may cause the battery to explode.
I'd put some sort of load resistor on the output of that power transistor, an incandescent automotive tail-light
as suggested by JohnR seems ideal for the small batteries typically lugged around with a radio.
Here's the specs for the dual filament 1157 builb:??
So the brake filament burns 26.8 Watts at 12.8 Volts, the tail-light filament burns 8.3 Watts at 14 Volts.
Why the brake filament is assumed to run at a lower voltage I have no idea, but current draw from
a 12.0 Volt supply should be roughly 2 Amps for the brake filament and 0.66 Amps for the tail-light filament.?
We're off grid, for our really big lead acid batteries?I use solid copper wire from old house wiring.
For example, 14 awg solid copper wire is 2.5 ohms per 1000 feet, so 100 feet is 0.25 Ohms,
and across a 12 Volt battery will draw around 12/0.25 = 48 Amps, dissipating 12*48=576 Watts.
An old car battery is worth about $10 at a scrap yard, as the lead can be recovered.
The smaller batteries that JohnR described are worth a little bit as well,
hence his statement of " If you had an old one to swap fantastic".
Some outfits may consider batteries to be hazardous and have policies to prohibit
giving them away, trading in an old one would keep their numbers lined up.
Jerry, KE7ER
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Show quoted text
On Mon, Jun 22, 2020 at 08:47 AM, Bill Cromwell wrote:
Hi John,
I have rolled my own and have considered additional sophistication like what you describe. I have only four of those SLABs and I just pay attention to how long they run the radios before a swap is required. My idea was to use a power transistor as a current sink into a dead short and draw it down to the low set point while monitoring and recording the voltage. All while *I* do more interesting things. Pencils and graph paper on a clipboard with a clock demand a lot of attention. Been there- done that. An arduino controller would be ideal. They don't seem to get bored:)
73,
Bill KU8H
bark less - wag more
Hide quoted text
?
On 6/22/20 11:33 AM, JohnR wrote:
I work for a phone company in maintenance. The fire alarm batteries get swapped out every 3 years need it or not. All of the batteries I use have been used for 3 years before I use them on the radios. If you know of a fire system company or maintenance people of buildings these are the people to ask. The batteries are scrap at that point and some people are strict about there scrap but the fire alarm people I deal with don't care that much, if you want one or two no problem. If you had an old one to swap fantastic. I have also found that?battery AH tester?at Aliexpress for a couple of dollars, I forget but under 5$. I use a tail light off of a car as a load. It runs the battery down to a certain voltage and cuts off. It then tells you how many amp-hours the battery will produce and give you an idea of how long it will last..Great for used batteries and to know what you have for field day
73, John
This is the one I use.
New ZB2L3 Li-ion Lithium Lead-acid Battery Capacity Meter Discharge
Tester Analyzer Measurement Analysis Instruments
--
¡°A single light can banish the darkness¡±
/Lux e tenebris
"A fool stares?at the finger that points at the moon"
I Ching/
|
I worked at Fort Hood in avionics for six years. Repaired some battery analyzers that would rejuvenate the NiCads used in the aircraft. Periodically, they'd discharge the batteries and recharge them to kill the memory that NiCads developed. They used aircraft landing lights for the load (we'd probably use brake lights) and when they got down to no light output, they'd clip shunts between the cells and leave 'em overnight. Then the analyzer would recharge the batteries and if they failed the test, they'd go through the discharge cycled again. The batteries could be recycled this way countless times.
Today, lithium batteries are the name of the game. I've even wondered about putting three or four cell phone batteries in series to try them out. For their size and power possibilities, they interest me for QRP rigs.
Bob ¡ª KK5R
On Monday, June 22, 2020, 4:45:36 PM EDT, Jerry Gaffke via groups.io <jgaffke@...> wrote:
I've been planning to build an arduino based battery evaluator as well.
> My idea was to use a power transistor as a current sink into a dead short and draw it down to the low set point while monitoring and recording the voltage.
Be aware that a lead acid battery (SLAB = sealed lead acid battery) has a very low internal impedance.
A short could be hundreds or even thousands of amps, and may cause the battery to explode.
I'd put some sort of load resistor on the output of that power transistor, an incandescent automotive tail-light
as suggested by JohnR seems ideal for the small batteries typically lugged around with a radio.
Here's the specs for the dual filament 1157 builb:??
So the brake filament burns 26.8 Watts at 12.8 Volts, the tail-light filament burns 8.3 Watts at 14 Volts.
Why the brake filament is assumed to run at a lower voltage I have no idea, but current draw from
a 12.0 Volt supply should be roughly 2 Amps for the brake filament and 0.66 Amps for the tail-light filament.?
We're off grid, for our really big lead acid batteries?I use solid copper wire from old house wiring.
For example, 14 awg solid copper wire is 2.5 ohms per 1000 feet, so 100 feet is 0.25 Ohms,
and across a 12 Volt battery will draw around 12/0.25 = 48 Amps, dissipating 12*48=576 Watts.
An old car battery is worth about $10 at a scrap yard, as the lead can be recovered.
The smaller batteries that JohnR described are worth a little bit as well,
hence his statement of " If you had an old one to swap fantastic".
Some outfits may consider batteries to be hazardous and have policies to prohibit
giving them away, trading in an old one would keep their numbers lined up.
Jerry, KE7ER
On Mon, Jun 22, 2020 at 08:47 AM, Bill Cromwell wrote:
Hi John,
I have rolled my own and have considered additional sophistication like what you describe. I have only four of those SLABs and I just pay attention to how long they run the radios before a swap is required. My idea was to use a power transistor as a current sink into a dead short and draw it down to the low set point while monitoring and recording the voltage. All while *I* do more interesting things. Pencils and graph paper on a clipboard with a clock demand a lot of attention. Been there- done that. An arduino controller would be ideal. They don't seem to get bored:)
73,
Bill KU8H
bark less - wag more
Hide quoted text
?
On 6/22/20 11:33 AM, JohnR wrote:
I work for a phone company in maintenance. The fire alarm batteries get swapped out every 3 years need it or not. All of the batteries I use have been used for 3 years before I use them on the radios. If you know of a fire system company or maintenance people of buildings these are the people to ask. The batteries are scrap at that point and some people are strict about there scrap but the fire alarm people I deal with don't care that much, if you want one or two no problem. If you had an old one to swap fantastic. I have also found that?battery AH tester?at Aliexpress for a couple of dollars, I forget but under 5$. I use a tail light off of a car as a load. It runs the battery down to a certain voltage and cuts off. It then tells you how many amp-hours the battery will produce and give you an idea of how long it will last..Great for used batteries and to know what you have for field day
73, John
This is the one I use.
New ZB2L3 Li-ion Lithium Lead-acid Battery Capacity Meter Discharge
Tester Analyzer Measurement Analysis Instruments
--
¡°A single light can banish the darkness¡±
/Lux e tenebris
"A fool stares?at the finger that points at the moon"
I Ching/
|
Bob Lunsford
N0YWB
Mick