Harbor Freight battery float charger #42292 circuit?

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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  


Re: Harbor Freight battery float charger #42292 circuit?

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



Re: Harbor Freight battery float charger #42292 circuit?
On Mon, 21 Nov 2016 15:57:49 -0500, "Carl Ijames"

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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      |
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Re: Harbor Freight battery float charger #42292 circuit?
On Monday, November 21, 2016 at 2:24:48 PM UTC-5, P E Schoen wrote:
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The TIP41 and S9013 form a comparator with positive feedback. No need for a
dding your series diode as the TIP41 and its base 1N4007 prevent any revers
e currents from the battery. If the battery has a shorted cell or is otherw
ise damagingly low, the TIP41 should come out of saturation allowing the S9
013 to turn on and start diverting TIP41 base current etc until TIP41 is co
mpletely off and S9013 is saturated on. But that's a real rough HFE depende
nt threshold.

Re: Harbor Freight battery float charger #42292 circuit?
Fred Bloggs wrote in message  

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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  


Re: Harbor Freight battery float charger #42292 circuit?
On Tuesday, November 22, 2016 at 3:22:49 AM UTC-5, P E Schoen wrote:
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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 disch
arging around R5-LED+diode-BC junction of TIP41, which looks substantial- a
lso maybe some discharge thru the 7805 bias network through base to collect
or of TIP41 in inverse mode conduction... not even going to get into revers
e 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 enoug
h of a clue.

Re: Harbor Freight battery float charger #42292 circuit?
On Monday, November 21, 2016 at 11:24:48 AM UTC-8, P E Schoen wrote:
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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

Re: Harbor Freight battery float charger #42292 circuit?

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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.

Re: Harbor Freight battery float charger #42292 circuit?
wrote:

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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      |
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Re: Harbor Freight battery float charger #42292 circuit?
wrote:

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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      |
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Re: Harbor Freight battery float charger #42292 circuit?

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those voltage might be OK for a few hours a day in a car alternator....
but they are rather high for a 24/7 float charger.

m

Re: Harbor Freight battery float charger #42292 circuit?
makolber wrote in message  

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The regulator in my 1989 Toyota truck probably is not very sophisticated,  
and does not really apply to a float charger needed only because I often  
don't drive it for weeks (even months) at a time. It is now charging with an  
old Schauer 6-8 amp charger somebody gave me about 40 years ago - still  
works fine - and stupid simple.

Here is some useful information if I decide to make my own high-tech battery  
charger, using a PIC:

http://www.evdl.org/pages/hartcharge.html

http://batteryuniversity.com/learn/article/charging_the_lead_acid_battery

http://batteryuniversity.com/learn/article/bu_214_summary_table_of_lead_based_batteries

http://batteryuniversity.com/learn/article/how_to_measure_state_of_charge

http://batteryuniversity.com/learn/article/caring_for_your_starter_battery

http://batteryuniversity.com/learn/article/what_everyone_should_know_about_battery_chargers

Thanks for the information and discussion.

Paul  


Re: Harbor Freight battery float charger #42292 circuit?
wrote:

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Wrong!  They are the desired cell voltages at those temperatures.

My patents:

3,496,447 Alternator Voltage Regulator Responsive to Temperature
3,505,590 Temperature Responsive Output Voltage Apparatus
3,522,482 Temperature Compensated Voltage Regulation
3,546,563 Alternator Voltage Regulation Utilizing A Constant Current
Source

By the late '60's _every_ (*) American car manufacturer was using one
of my alternator regulator designs.

Ford, Chrysler, GM, and American Motors (Nash, etc, for you youngsters
;-)

I can't remember if Kaiser-Frazer was still existent, they aren't on
my list.

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A conventional battery charger will overcharge a battery if left on
indefinitely, because it provides a voltage well above cell voltage.
        
                                        ...Jim Thompson
--  
| James E.Thompson                                 |    mens     |
| Analog Innovations                               |     et      |
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Re: Harbor Freight battery float charger #42292 circuit?
"Jim Thompson"  wrote in message  

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From the second graph, the ideal voltages seem to be:

Temp       Vpc        V12    Tempco
0C        2.49    14.95V
25C        2.47    14.80V        -6 mV/C
50C        2.38    14.30V        -20 mV/C
75C        2.32    13.90V        -16 mV/C
100C    2.25    13.50V        -16 mV/C

The information I found elsewhere was about as follows, for state-of-charge  
after settling 3 hours:

SOC        Vpc        V12
100%    2.116    12.700
90%        2.083    12.500
80%        2.070    12.420
70%        2.053    12.320
60%        2.033    12.200
50%        2.010    12.060
40%        1.983    11.900
30%        1.958    11.750
20%        1.930    11.580
10%        1.890    11.340
0%        1.750    10.500

And my charging algorithm as originally conceived:

Initial charge at 0.2C for 5 hour nominal charge time for a 12 V, 12 A-h SLA
initial charge at 2.4A
Maintain charging until voltage reaches 2.4-2.5 Vpc = 14.4-15 VDC
At 14.4V battery is 70-80% charged
Keep at 14.4 volt until current = 0.02C (240 mA for 12 Ah)
Float charge at 12.8-13.2V (or initiate new charging cycle at 12.5 volts  
(90%)
Voltages are based on 25C. Voltage changes by -0.003 Vpc/DegC. So 14.31V at  
30C and 14.49V at 20C

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My battery is being charged at 13.85 volts at about 45C ambient (about 7C).  
That seems to be well below even the minimum of your charts (as well as I  
could read them). And my SLA is reading 13.42 volts. So those seem to be  
safe values. I find it hard to believe the "Ford limits" of 14.5 to 15.3  
volts at about 20C. Even for fast charging (30+ amps) I would expect no more  
than 14.4 volts under any circumstances.  And the high temperature of 125C  
(257F) seems way above any expected temperature that might be encountered  
under the hood of a vehicle.

I'll have to read the patents for more information.

Thanks,

Paul  


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