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Harbor Freight battery float charger #42292 circuit?

Started by P E Schoen November 21, 2016
I have one of the cheap ($5) Harbor Freight lead-acid battery float chargers 
and I found that it was not working (it may have been damaged some time 
ago - I had the case open). I traced the circuit and it is basically a FWB 
and capacitor providing 25 VDC to a 7805 regulator with resistors to set the 
output to about 13.5 volts. But it also has a TIP41 NPN BJT with a diode and 
LED to the base, with the collector of a S9013 NPN and some resistors that 
appear to be intended to stop charging or perhaps inhibit charging if the 
battery voltage is too low. The schematics of various versions, and some 
modifications, are in the following:

http://www.desert-home.com/2012/02/battery-charging-harbor-freight-item.html
http://www.desert-home.com/2012/03/battery-charging-part-2-harbor-freight.html
http://www.desert-home.com/2012/07/battery-charging-part-3-harbor-freight.html

The 7805 was blown in my unit so I replaced it with a 78M05 and I added a 
trimpot to adjust output to 13.5V. I also added a diode in series with the 
output to avoid damage from reversal. And I also removed R4 which 
essentially eliminates the function of the TIP41. It looks like the S9013 
transistor is biased so that it will turn on when the voltage from the 
negative output lead to circuit ground exceeds 4.9V, and that will turn off 
the base drive to the TIP41 and turn off the output and the indicator LED.

It seems to work OK now and it is holding a charge of 13.23V on a 12 A-h SLA 
I charged overnight at about 0.33A. The battery read 13.13V when 
disconnected and a minute later dropped to 13.00. When reconnected it 
charged at 0.25A and after a minute dropped to 0.15A.

I had planned to build a high-tech charger/monitor using a PIC, and I still 
may do so, but for now I just want something that works. I might tweak the 
voltage down to about 13.2V which should be plenty to maintain charge on a 
FLA 100 A-h deep cycle battery I have, as well as the starting battery of my 
seldom used truck.

I also have a gel-cell SLA charger that I need to test.

Any ideas about that odd circuit with the TIP41?

Thanks,

Paul 

"P E Schoen"  wrote in message news:o0vhkp$le0$1@dont-email.me...

I have one of the cheap ($5) Harbor Freight lead-acid battery float chargers
and I found that it was not working (it may have been damaged some time
ago - I had the case open). I traced the circuit and it is basically a FWB
and capacitor providing 25 VDC to a 7805 regulator with resistors to set the
output to about 13.5 volts. But it also has a TIP41 NPN BJT with a diode and
LED to the base, with the collector of a S9013 NPN and some resistors that
appear to be intended to stop charging or perhaps inhibit charging if the
battery voltage is too low. The schematics of various versions, and some
modifications, are in the following:

http://www.desert-home.com/2012/02/battery-charging-harbor-freight-item.html
http://www.desert-home.com/2012/03/battery-charging-part-2-harbor-freight.html
http://www.desert-home.com/2012/07/battery-charging-part-3-harbor-freight.html

The 7805 was blown in my unit so I replaced it with a 78M05 and I added a
trimpot to adjust output to 13.5V. I also added a diode in series with the
output to avoid damage from reversal. And I also removed R4 which
essentially eliminates the function of the TIP41. It looks like the S9013
transistor is biased so that it will turn on when the voltage from the
negative output lead to circuit ground exceeds 4.9V, and that will turn off
the base drive to the TIP41 and turn off the output and the indicator LED.

It seems to work OK now and it is holding a charge of 13.23V on a 12 A-h SLA
I charged overnight at about 0.33A. The battery read 13.13V when
disconnected and a minute later dropped to 13.00. When reconnected it
charged at 0.25A and after a minute dropped to 0.15A.

I had planned to build a high-tech charger/monitor using a PIC, and I still
may do so, but for now I just want something that works. I might tweak the
voltage down to about 13.2V which should be plenty to maintain charge on a
FLA 100 A-h deep cycle battery I have, as well as the starting battery of my
seldom used truck.

I also have a gel-cell SLA charger that I need to test.

Any ideas about that odd circuit with the TIP41?

Thanks,

Paul
===============================================================

I don't start my pickup for days at a time and the batteries were getting a 
bit weak last winter so I bought a little solar cell charger.  Don't know if 
it helped or not, but the batteries made it through winter and then died in 
the summer (got 5 years from 6 year warranty batteries so no complaints). 
Found out warranties are much shorter now and prices have doubled, sigh. 
Anyway, I was a bit concerned about overcharging and needed a toy so I 
bought one of these to play with: 
https://www.amazon.com/gp/product/B01HZ8HZQ6/ref=oh_aui_detailpage_o04_s00?ie=UTF8&psc=1 
It is a "MPPT Solar Panel Controller Battery Charging Board 1-100W 5A 9V 12V 
18V 24V Solar Energy Renewable" populated board, no case or leads.  I had 
fantasies that it would be a buck boost circuit so would charge a 12 V 
battery even when the solar panel output was less than 12 V, but no, it is 
only a buck.  What did I expect for $11, anyway :-).  The solar panel is 
https://www.amazon.com/gp/product/B012ZHGGXU/ref=oh_aui_detailpage_o07_s00?ie=UTF8&psc=1, 
"ALLPOWERS 18V 7.5W Portable Solar Car Boat Power Sunpower Solar Panel 
Battery Charger Maintainer for Automobile Motorcycle Tractor Boat 
Batteries", just because that was the cheapest I found at the time.  From my 
research it seems that with 15W or less panels and a car sized battery a 
controller isn't needed as you shouldn't be able to overcharge the battery 
anyway.  I wanted to play so I got the controller.  The solar panel has a 
cigarette lighter adapter to connect to the vehicle, with a little LED that 
has always bugged me since it draws current when the sun is down.  Only 5 mA 
but I cut it out anyway.  There is a Schottky diode in the panel to prevent 
battery discharge when the sun is down, so that is nice even without an 
external controller.  There is an LED on the controller that only draws from 
the solar panel, and I verified that it draws no current from the battery 
when the sun is down.  My dinky panel topped out at about 300 mA the day I 
was making measurements so the 5A rating is way overkill but it was about 
the smallest and cheapest I found.  There is a pot for output voltage 
adjust, it comes preset for 13.5 V according to my meter, so I left that 
alone.  There is a second pot for MPPT adjust, but absolutely no 
documentation came with it so I have no idea what this does.  I emailed the 
vendor and asked for any info and they sent a hand drawn figure showing the 
input and output pins, just like on the board itself, but no other info, 
sigh.  Anyway, it's double the cost of the Harbor Freight units but you 
don't have to rebuild it and you couldn't build it for twice that to use as 
a general power supply or a solar charger controller, but you do have to 
provide your own enclosure.  I tried to play a little checking the output 
current and voltage and solar panel voltage while moving it around, and it 
did seem to change the panel voltage with load but I won't swear it was 
really MPPT.  Just a long winded suggestion if you want to explore more 
options than your Yuasa.

-----
Regards,
Carl Ijames


On Monday, November 21, 2016 at 2:24:48 PM UTC-5, P E Schoen wrote:
> I have one of the cheap ($5) Harbor Freight lead-acid battery float chargers > and I found that it was not working (it may have been damaged some time > ago - I had the case open). I traced the circuit and it is basically a FWB > and capacitor providing 25 VDC to a 7805 regulator with resistors to set the > output to about 13.5 volts. But it also has a TIP41 NPN BJT with a diode and > LED to the base, with the collector of a S9013 NPN and some resistors that > appear to be intended to stop charging or perhaps inhibit charging if the > battery voltage is too low. The schematics of various versions, and some > modifications, are in the following: > > http://www.desert-home.com/2012/02/battery-charging-harbor-freight-item.html > http://www.desert-home.com/2012/03/battery-charging-part-2-harbor-freight.html > http://www.desert-home.com/2012/07/battery-charging-part-3-harbor-freight.html > > The 7805 was blown in my unit so I replaced it with a 78M05 and I added a > trimpot to adjust output to 13.5V. I also added a diode in series with the > output to avoid damage from reversal. And I also removed R4 which > essentially eliminates the function of the TIP41. It looks like the S9013 > transistor is biased so that it will turn on when the voltage from the > negative output lead to circuit ground exceeds 4.9V, and that will turn off > the base drive to the TIP41 and turn off the output and the indicator LED. > > It seems to work OK now and it is holding a charge of 13.23V on a 12 A-h SLA > I charged overnight at about 0.33A. The battery read 13.13V when > disconnected and a minute later dropped to 13.00. When reconnected it > charged at 0.25A and after a minute dropped to 0.15A. > > I had planned to build a high-tech charger/monitor using a PIC, and I still > may do so, but for now I just want something that works. I might tweak the > voltage down to about 13.2V which should be plenty to maintain charge on a > FLA 100 A-h deep cycle battery I have, as well as the starting battery of my > seldom used truck. > > I also have a gel-cell SLA charger that I need to test. > > Any ideas about that odd circuit with the TIP41? > > Thanks, > > Paul
The TIP41 and S9013 form a comparator with positive feedback. No need for adding your series diode as the TIP41 and its base 1N4007 prevent any reverse currents from the battery. If the battery has a shorted cell or is otherwise damagingly low, the TIP41 should come out of saturation allowing the S9013 to turn on and start diverting TIP41 base current etc until TIP41 is completely off and S9013 is saturated on. But that's a real rough HFE dependent threshold.
On Monday, November 21, 2016 at 11:24:48 AM UTC-8, P E Schoen wrote:
> I have one of the cheap ($5) Harbor Freight lead-acid battery float chargers > and I found that it was not working (it may have been damaged some time > ago - I had the case open). I traced the circuit and it is basically a FWB > and capacitor providing 25 VDC to a 7805 regulator with resistors to set the > output to about 13.5 volts. But it also has a TIP41 NPN BJT with a diode and > LED to the base, with the collector of a S9013 NPN and some resistors that > appear to be intended to stop charging or perhaps inhibit charging if the > battery voltage is too low. The schematics of various versions, and some > modifications, are in the following: > > http://www.desert-home.com/2012/02/battery-charging-harbor-freight-item.html > http://www.desert-home.com/2012/03/battery-charging-part-2-harbor-freight.html > http://www.desert-home.com/2012/07/battery-charging-part-3-harbor-freight.html > > The 7805 was blown in my unit so I replaced it with a 78M05 and I added a > trimpot to adjust output to 13.5V. I also added a diode in series with the > output to avoid damage from reversal. And I also removed R4 which > essentially eliminates the function of the TIP41. It looks like the S9013 > transistor is biased so that it will turn on when the voltage from the > negative output lead to circuit ground exceeds 4.9V, and that will turn off > the base drive to the TIP41 and turn off the output and the indicator LED. > > It seems to work OK now and it is holding a charge of 13.23V on a 12 A-h SLA > I charged overnight at about 0.33A. The battery read 13.13V when > disconnected and a minute later dropped to 13.00. When reconnected it > charged at 0.25A and after a minute dropped to 0.15A. > > I had planned to build a high-tech charger/monitor using a PIC, and I still > may do so, but for now I just want something that works. I might tweak the > voltage down to about 13.2V which should be plenty to maintain charge on a > FLA 100 A-h deep cycle battery I have, as well as the starting battery of my > seldom used truck. > > I also have a gel-cell SLA charger that I need to test. > > Any ideas about that odd circuit with the TIP41? > > Thanks, > > Paul
On that note, are there any good, reasonably-cheap SMPS 12V (14.4v?) battery chargers? You would think that in this era of energy efficiency, linear voltage regulators + 50/60Hz transformers would be frowned upon... Thanks! Michael
On Mon, 21 Nov 2016 15:57:49 -0500, "Carl Ijames"
<carl.ijamesXyZZy@ZZxyz.verizon.net> wrote:

[snip]
>I don't start my pickup for days at a time and the batteries were getting a >bit weak last winter so I bought a little solar cell charger. Don't know if >it helped or not, but the batteries made it through winter and then died in >the summer (got 5 years from 6 year warranty batteries so no complaints). >Found out warranties are much shorter now and prices have doubled, sigh. >Anyway, I was a bit concerned about overcharging and needed a toy so I >bought one of these to play with: >https://www.amazon.com/gp/product/B01HZ8HZQ6/ref=oh_aui_detailpage_o04_s00?ie=UTF8&psc=1 >It is a "MPPT Solar Panel Controller Battery Charging Board 1-100W 5A 9V 12V >18V 24V Solar Energy Renewable" populated board, no case or leads. I had >fantasies that it would be a buck boost circuit so would charge a 12 V >battery even when the solar panel output was less than 12 V, but no, it is >only a buck. What did I expect for $11, anyway :-). The solar panel is >https://www.amazon.com/gp/product/B012ZHGGXU/ref=oh_aui_detailpage_o07_s00?ie=UTF8&psc=1, >"ALLPOWERS 18V 7.5W Portable Solar Car Boat Power Sunpower Solar Panel >Battery Charger Maintainer for Automobile Motorcycle Tractor Boat >Batteries", just because that was the cheapest I found at the time. From my >research it seems that with 15W or less panels and a car sized battery a >controller isn't needed as you shouldn't be able to overcharge the battery >anyway. I wanted to play so I got the controller. The solar panel has a >cigarette lighter adapter to connect to the vehicle, with a little LED that >has always bugged me since it draws current when the sun is down. Only 5 mA >but I cut it out anyway. There is a Schottky diode in the panel to prevent >battery discharge when the sun is down, so that is nice even without an >external controller. There is an LED on the controller that only draws from >the solar panel, and I verified that it draws no current from the battery >when the sun is down. My dinky panel topped out at about 300 mA the day I >was making measurements so the 5A rating is way overkill but it was about >the smallest and cheapest I found. There is a pot for output voltage >adjust, it comes preset for 13.5 V according to my meter, so I left that >alone. There is a second pot for MPPT adjust, but absolutely no >documentation came with it so I have no idea what this does. I emailed the >vendor and asked for any info and they sent a hand drawn figure showing the >input and output pins, just like on the board itself, but no other info, >sigh. Anyway, it's double the cost of the Harbor Freight units but you >don't have to rebuild it and you couldn't build it for twice that to use as >a general power supply or a solar charger controller, but you do have to >provide your own enclosure. I tried to play a little checking the output >current and voltage and solar panel voltage while moving it around, and it >did seem to change the panel voltage with load but I won't swear it was >really MPPT. Just a long winded suggestion if you want to explore more >options than your Yuasa. > >----- >Regards, >Carl Ijames >
That solar approach is appealing. I have a pick-em-up truck that gets driven maybe once a month (bought new, 15 years old with only 39,000 miles ;-). It would be troublesome to plug it in to mains between trips, but the solar, particularly here in AZ, should work great. ...Jim Thompson -- | James E.Thompson | mens | | Analog Innovations | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | STV, Queen Creek, AZ 85142 Skype: skypeanalog | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at http://www.analog-innovations.com | 1962 | I'm looking for work... see my website.
In article <09ba71b9-6a5c-4562-8f8f-ba728a8e38d6@googlegroups.com>,
 <mrdarrett@gmail.com> wrote:

>On that note, are there any good, reasonably-cheap SMPS 12V (14.4v?) battery chargers? > >You would think that in this era of energy efficiency, linear voltage regulators + >50/60Hz transformers would be frowned upon...
If you can get by with modest charge rates, there are "high efficiency" members of the Deltran Battery Tender family. The biggest of these seems to be the 5-ampere model.
Fred Bloggs wrote in message 
news:a32be85b-3763-4715-9a9e-2f2798dbe702@googlegroups.com...

> The TIP41 and S9013 form a comparator with positive feedback. No need for > adding your series diode as the TIP41 and its base 1N4007 prevent any > reverse currents from the battery. If the battery has a shorted cell or is > otherwise damagingly low, the TIP41 should come out of saturation allowing > the S9013 to turn on and start diverting TIP41 base current etc until > TIP41 is completely off and S9013 is saturated on. But that's a real rough > HFE dependent threshold.
I did a simulation and it seems to work OK according to the schematic shown in the first of the links above in the OP, but R5 is actually 400 ohms and not 400k. It also seems to be protected against reverse connection as you describe. Here is the simulation with steps of battery voltage from 8 volts to 16 volts 1/2 volt per step, then zero volts (short) and -12V (reversed battery). http://enginuitysystems.com/pix/electronics/HF_Float_Charger.png And the ASC file: http://enginuitysystems.com/pix/electronics/HF_Float_Charger.asc Thanks, Paul
On Tuesday, November 22, 2016 at 3:22:49 AM UTC-5, P E Schoen wrote:
> Fred Bloggs wrote in message > news:a32be85b-3763-4715-9a9e-2f2798dbe702@googlegroups.com... > > > The TIP41 and S9013 form a comparator with positive feedback. No need for > > adding your series diode as the TIP41 and its base 1N4007 prevent any > > reverse currents from the battery. If the battery has a shorted cell or is > > otherwise damagingly low, the TIP41 should come out of saturation allowing > > the S9013 to turn on and start diverting TIP41 base current etc until > > TIP41 is completely off and S9013 is saturated on. But that's a real rough > > HFE dependent threshold. > > I did a simulation and it seems to work OK according to the schematic shown > in the first of the links above in the OP, but R5 is actually 400 ohms and > not 400k. It also seems to be protected against reverse connection as you > describe. Here is the simulation with steps of battery voltage from 8 volts > to 16 volts 1/2 volt per step, then zero volts (short) and -12V (reversed > battery). > > http://enginuitysystems.com/pix/electronics/HF_Float_Charger.png > > And the ASC file: > > http://enginuitysystems.com/pix/electronics/HF_Float_Charger.asc > > Thanks, > > Paul
I thought that 400k looked funny, sets the S9013 threshold at about 7x 0.6=4.2V. It also has a sneak circuit upon power loss with the battery discharging around R5-LED+diode-BC junction of TIP41, which looks substantial- also maybe some discharge thru the 7805 bias network through base to collector of TIP41 in inverse mode conduction... not even going to get into reverse battery mode.The circuit is basically trash. It's probably not even good for parts salvage since they're probably already salvaged from 30 year old junk they removed from boards with a torch and then washed them off in the yellow river. Harbor Freight, Northern Tools and all those Dollar this and that stores need to be banned from doing business in U.S.- they're merely a testimony to the stupidity of Americans- as if electing Trump wasn't enough of a clue.
On Mon, 21 Nov 2016 14:24:41 -0500, "P E Schoen" <paul@pstech-inc.com>
wrote:

>I have one of the cheap ($5) Harbor Freight lead-acid battery float chargers >and I found that it was not working (it may have been damaged some time >ago - I had the case open). I traced the circuit and it is basically a FWB >and capacitor providing 25 VDC to a 7805 regulator with resistors to set the >output to about 13.5 volts. But it also has a TIP41 NPN BJT with a diode and >LED to the base, with the collector of a S9013 NPN and some resistors that >appear to be intended to stop charging or perhaps inhibit charging if the >battery voltage is too low. The schematics of various versions, and some >modifications, are in the following: > >http://www.desert-home.com/2012/02/battery-charging-harbor-freight-item.html >http://www.desert-home.com/2012/03/battery-charging-part-2-harbor-freight.html >http://www.desert-home.com/2012/07/battery-charging-part-3-harbor-freight.html > >The 7805 was blown in my unit so I replaced it with a 78M05 and I added a >trimpot to adjust output to 13.5V. I also added a diode in series with the >output to avoid damage from reversal. And I also removed R4 which >essentially eliminates the function of the TIP41. It looks like the S9013 >transistor is biased so that it will turn on when the voltage from the >negative output lead to circuit ground exceeds 4.9V, and that will turn off >the base drive to the TIP41 and turn off the output and the indicator LED. > >It seems to work OK now and it is holding a charge of 13.23V on a 12 A-h SLA >I charged overnight at about 0.33A. The battery read 13.13V when >disconnected and a minute later dropped to 13.00. When reconnected it >charged at 0.25A and after a minute dropped to 0.15A. > >I had planned to build a high-tech charger/monitor using a PIC, and I still >may do so, but for now I just want something that works. I might tweak the >voltage down to about 13.2V which should be plenty to maintain charge on a >FLA 100 A-h deep cycle battery I have, as well as the starting battery of my >seldom used truck. > >I also have a gel-cell SLA charger that I need to test. > >Any ideas about that odd circuit with the TIP41? > >Thanks, > >Paul
Change the 7805 to an LM317 and adjust resistors accordingly. The TIP41 circuit is weird. Or simply toss most of it and change LM317 circuitry to a current source arrangement... documented all over the web. ...Jim Thompson -- | James E.Thompson | mens | | Analog Innovations | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | STV, Queen Creek, AZ 85142 Skype: skypeanalog | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at http://www.analog-innovations.com | 1962 | I'm looking for work... see my website.
On Mon, 21 Nov 2016 14:24:41 -0500, "P E Schoen" <paul@pstech-inc.com>
wrote:

>I have one of the cheap ($5) Harbor Freight lead-acid battery float chargers >and I found that it was not working (it may have been damaged some time >ago - I had the case open). I traced the circuit and it is basically a FWB >and capacitor providing 25 VDC to a 7805 regulator with resistors to set the >output to about 13.5 volts. But it also has a TIP41 NPN BJT with a diode and >LED to the base, with the collector of a S9013 NPN and some resistors that >appear to be intended to stop charging or perhaps inhibit charging if the >battery voltage is too low. The schematics of various versions, and some >modifications, are in the following: > >http://www.desert-home.com/2012/02/battery-charging-harbor-freight-item.html >http://www.desert-home.com/2012/03/battery-charging-part-2-harbor-freight.html >http://www.desert-home.com/2012/07/battery-charging-part-3-harbor-freight.html > >The 7805 was blown in my unit so I replaced it with a 78M05 and I added a >trimpot to adjust output to 13.5V. I also added a diode in series with the >output to avoid damage from reversal. And I also removed R4 which >essentially eliminates the function of the TIP41. It looks like the S9013 >transistor is biased so that it will turn on when the voltage from the >negative output lead to circuit ground exceeds 4.9V, and that will turn off >the base drive to the TIP41 and turn off the output and the indicator LED. > >It seems to work OK now and it is holding a charge of 13.23V on a 12 A-h SLA >I charged overnight at about 0.33A. The battery read 13.13V when >disconnected and a minute later dropped to 13.00. When reconnected it >charged at 0.25A and after a minute dropped to 0.15A. > >I had planned to build a high-tech charger/monitor using a PIC, and I still >may do so, but for now I just want something that works. I might tweak the >voltage down to about 13.2V which should be plenty to maintain charge on a >FLA 100 A-h deep cycle battery I have, as well as the starting battery of my >seldom used truck. > >I also have a gel-cell SLA charger that I need to test. > >Any ideas about that odd circuit with the TIP41? > >Thanks, > >Paul
If you want to do it right, locate the "charge-monitor" adjacent to the battery under the hood and follow a proper TC... <http://www.analog-innovations.com/SED/AlternatorRegulatorTC.pdf> ...Jim Thompson -- | James E.Thompson | mens | | Analog Innovations | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | STV, Queen Creek, AZ 85142 Skype: skypeanalog | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at http://www.analog-innovations.com | 1962 | I'm looking for work... see my website.