Battery tender or Picaxe 12v dc battery tender

newplumber

Senior Member
#1
Hi
I searched the forums but came up short ... I was hoping someone did a post on tending their car battery since Allycat,Marks and others did awesome posts on reading voltage but I didn't find tender battery posts.
Here's my future project ...my 12vdc battery in my riding lawn mower/tractor seems to play dead every time I try to mow the grass and I believe its because it sits all winter long. I've read alot
on google about maintaining batterys and seems if a battery is charged and discharged regularly(daily) it keeps it healthy. I'm sure there is a lot of battery tenders out there but mine will be the first
battery tender that does all the maintenance at 2AM and if possible will all be run off solar cells, but for basics my idea is
at 2 am
...discharge battery to 12.5v ...using a 12v 2-amp power source ( fan ,heater etc)
...charge battery to 14.5v ...using a 12v 2amp charger
every other day or so using ds3231 rtc

The only simple way I can see using solar power is to convert 12vdc to 120ac to use my ac/dc charger
unless there is a simplier way? ...I plan on using a 100watt 12vdc solar panel with a few stationary batterys

I will draw up my simple idea later on to make sense.

I also was planning to use the picaxe 20m2 and maybe add a few safety sensors
-- battery temp
-- battery boil over
etc

like always any extra input always helps
 

oracacle

Senior Member
#2
Look into the optimte range of charges. Aloy of motor cycle riders are nice weather only and so the bike sits all winter on one of those.
I would suggest you look to them for a starting point or a plug and play solution.

They are great bus of kit, i have seen them bring batteries back from the dead along side the maintenance abilities
 

techElder

was Texasclodhopper
#3
A lead type battery does not need to be discharged to charge it.

Just maintain 13.8 volts and a minor charge current to maintain the battery when not being used.

Everything else is fluff and fun. :D
 

premelec

Senior Member
#4
Temperature should be taken into account in your charging and discharging... there are many essays written on lead acid battery care - been with us over 100 years... in any case do not over discharge! [and there are pulsing circuits claiming to de-sulphate the plates if you do - various opinions on the effectiveness of these - just don't over discharge and with sealed cells don't over charge - with open cells just add water before the plates show].
 

manuka

Senior Member
#5
Newplumber: Your need calls for so called "trickle charging". Best forget PICAXE at this stage,& first expland on the battery type,capacity,storage conditions and function - the latter assumed for engine starting. There may well be in circuit battery drain for your mower even when parked -a clock perhaps?

FWIW -the little I know of North Dakota relates to the regions V-E-R-Y continental climate,with your icy winters perhaps even causing the battery's watery acid electrolyte to freeze in the snow. Simply wintering the battery indoors & occasionally tending (perhaps with a cheap solar car battery charger) may be enough?

Stan. in subtropical NZ (where even frosts are rare!)
 

lbenson

Senior Member
#6
Happy to accept critiques, but what I'm now using to maintain a charge on a battery (while supplying power to modem & router) is one of these fed by an old 18V laptop charger and set to 13.8V with a schottky diode and a 10 ohm resistor between the module output and the plus terminal of a 12V SLA battery: https://www.ebay.com/itm/DC-DC-Step...h-button-Module-with-LCD-Display/112165057965

DC-DC module with LCD.jpg

For another similar setup, using one of these: https://www.ebay.com/itm/5pcs-Mini-...wn-Module-4-75V-23V-to-1V-17V-FJ/142771201523
DC-DC module without LCD.jpg

Fine-tuning the output voltage is fiddly with this module and its little pot.
 

newplumber

Senior Member
#7
Well thanks you all for the input

oracacle said:
Look into the optimte range of charges
ok I will check it out optimate charges


texas said:
A lead type battery does not need to be discharged to charge it
okay so your saying just maintain the voltage with a slow current draw?

premelec said:
and there are pulsing circuits claiming to de-sulphate the plates
that's exactly what i was wanting to do...and of course not over charge and your right i need to watch the heat


manuka said:
Your need calls for so called "trickle charging".
ok but if i just trickle charged the battery it seems sulphate can still build on the plates
and was thinking I need a heavy discharge once in a while ...but i have been wrong ...ONCE!
btw if the battery's water/acid freezes which I am sure it does but I see no downside to the amps
its pushing out other then the motor is very stubborn to turn over

lbenson said:
one of these fed by an old 18V laptop charger and set to 13.8V with a schottky diode and a 10 ohm resistor between the module output and the plus terminal of a 12V SLA battery
thats a great idea ...I have a few of those buck convertors and its awesome to see the output on the display
but what i am going to try is duplicating how my van battery goes thru cycles since it seems to be lasting 10+ years

Its going to be a few days before I can draw a clearer picture ...but thanks again for the info
 
#8
I have a home made uninterruptible DC power supply unit that uses a Picaxe for under-voltage detection, which switches a latching relay to protect the sealed lead acid batteries, and kills it's own power as it does so, to prevent any drain at all. For charging and normal running I have a mains powered switched mode 12V power supply, around 10A at 12V nominal, there are loads of these on ebay, and they all seem to have a voltage adjustment of at least +/- 10%, often a bit more. Because I use sealed lead acid cells, I have the voltage set to 13.2 V, which seems fine - it's been working for a couple of years now.

As a trickle charger these cheap power supplies are pretty good, but they can have problems with the current limiting, as some use a "hiccup" protection mode where if the battery tries to draw more than the current limit the power supply shuts down and then tries to recent half a second of so later. I found that just using a low value, high power rating, resistor in series was a good enough way to stop this happening. The value in my case was chosen to minimise power loss when the power supply was running the voltage regulators (my unit runs my home VDSL modem, router, switch, so we have internet connectivity for a day or so if we have a power outage). for a battery charger you can choose a value that drops, say, 2V at the maximum charge current (so for a 10A supply, the resistor would need to be 0.2 ohm) with a power rating that is enough to cope with the short duration dissipation in the resistor (so for 2V at 10A, 20W). In practice the resistor never gets near that sort of power dissipation, as I have the Picaxe set to disconnect the battery at 11V, and when charging even the 56 Ah sealed lead acid battery pack I have only takes a minute or so to get up to around 12.5 V when initially charging from flat, and quickly rises to around 13V after a few minutes, so the resistor loss is pretty small.

Overall I'm happy with the setup, as it's rare for us to get a power outage for more than a few hours, so the batteries don't really get used a lot. It's handy being able to have an internet connection and still use wifi for the laptop and my wife's iPad if the power fails, though.

For your trickle charger, one of these cheap LED metal frame power supplies fitted in a ventilated box would make a pretty cheap trickle charger, as they are pretty efficient, so use very little power from the mains when running, and barely get warm.
 
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geoff07

Senior Member
#10
Likewise, I use the CTEC 10A model to float two lead-acid batteries to power my kitchen lights, We have overhead mains and it goes out occasionally, So 12v leds and a picaxe with pushbuttons around the kitchen keep the lights on.
 

geezer88

Senior Member
#11
Batteries can last for decades if properly taken care of. You need to research "float charging" or "floating" a battery. The best voltages will be temperature and plate chemistry dependent. This means buying a battery that comes from a major manufacturer and provides information for properly caring for the battery. Armed with this information, you will be ready to design a proper charger for your battery.

By the way, I've got a riding mower, and the little battery to start it seems to only get about 5 years of useful life. That's if I take it out of the mower for the winter, and float charge it periodically. Unfortunately, the charger on the mower is unregulated and seems to be very hard on the battery. Good luck with your project, I feel the pain.

tom
 

rq3

Senior Member
#12
Hi
I searched the forums but came up short ... I was hoping someone did a post on tending their car battery since Allycat,Marks and others did awesome posts on reading voltage but I didn't find tender battery posts.
Here's my future project ...my 12vdc battery in my riding lawn mower/tractor seems to play dead every time I try to mow the grass and I believe its because it sits all winter long. I've read alot
on google about maintaining batterys and seems if a battery is charged and discharged regularly(daily) it keeps it healthy. I'm sure there is a lot of battery tenders out there but mine will be the first
battery tender that does all the maintenance at 2AM and if possible will all be run off solar cells, but for basics my idea is
at 2 am
...discharge battery to 12.5v ...using a 12v 2-amp power source ( fan ,heater etc)
...charge battery to 14.5v ...using a 12v 2amp charger
every other day or so using ds3231 rtc

The only simple way I can see using solar power is to convert 12vdc to 120ac to use my ac/dc charger
unless there is a simplier way? ...I plan on using a 100watt 12vdc solar panel with a few stationary batterys

I will draw up my simple idea later on to make sense.

I also was planning to use the picaxe 20m2 and maybe add a few safety sensors
-- battery temp
-- battery boil over
etc

like always any extra input always helps
I'm coming at this from the aircraft industry, where the batteries are generally wet cell lead-acid (you can unscrew the caps and add water), or Recombinant Glass Matt (RGM) lead-acid, where the battery is permanently sealed.

We also deal with Nickel-Cadmium, which is not germane here.

Aircraft batteries live in a pretty nasty environment, may sit for weeks or months between uses, and are required by law to be capacity tested once a year, so we have a pretty good data base based on hundreds of batteries of different types.

Wet cell batteries that are used (flown) regularly tend to last about 3 years.
Sealed batteries that are used (flown) regularly tend to last about 5 years.

Wet cell batteries that are removed during the winter when it is known that they won't be flown, and regularly charged once a month tend to last about 3 years.
Sealed batteries that are removed during the winter when it is known that they won't be flown, and regularly charged once a month tend to last about 5 years.

Either type of battery placed on a "battery minder" whenever the battery is not in use lasts about 18-24 months. It's tough to convince the owner of a $500 aircraft battery that the best thing he can do is not monkey with it. The battery WILL self discharge over time (sealed MUCH less than wet), and fighting that chemical reaction with an opposing, and constant charging action only lessens the life of the battery.

But hey, there's a huge industry out there convincing folks to buy products that help to kill their batteries. One little bit I've learned over the years: the initial charge is CRITICAL. Slamming a new battery with a Sears battery charger at 25 amps is guaranteed to at least halve the life of the battery. A nice, slow, 3 amp charge overnight leads to a long, happy battery life for either type.
 

newplumber

Senior Member
#13
jeremy said:
I have a home made uninterruptible DC power supply unit that uses a Picaxe for under-voltage detection, which switches a latching relay to protect the sealed lead acid batteries, and kills it's own power as it does so, to prevent any drain at all. For charging and normal running I have a mains powered switched mode 12V power supply, around 10A at 12V nominal, there are loads of these on ebay, and they all seem to have a voltage adjustment of at least +/- 10%, often a bit more. Because I use sealed lead acid cells, I have the voltage set to 13.2 V, which seems fine - it's been working for a couple of years now
thanks for the good information ... someday I am going to try doing the same thing for if the power fails
do you have a schematic on how your powering the picaxe? thru a buck convertor? good info tho


texasclod said:
Or ...
You could use one of these, as I have with great success.
https://www.amazon.com/s/ref=nb_sb_s...=243UJHX7BKRFE
thanks for mentioning that ....shows I/we can build one thats smarter and cheaper with a battery!
if I do the math right
1 = picaxe 20m2 = $3.00
2 = sensors = $4.00
1 = rtc = $2.00
1 = 12v charger = $8.00
1 = relay =$3.00
1 = battery = $26.00 at menards
https://www.menards.com/main/tools-...6819218414.htm?tid=3093445509982668089&ipos=3
1 = plumber wiring up wrong and redoing it 4+ times to get it right = (on the final correct way) $46.00
so 58 - 46 = I save 12volts :) of course someday I hope to give it back to the forum

geezer88 said:
Batteries can last for decades if properly taken care of
your probably right ....so starting my van 4+ times a day seems to be properly taken care of my battery
since its been lasting a long time with no issues at all .....well....I better go start it again since I typed that!

rq3 said:
Either type of battery placed on a "battery minder" whenever the battery is not in use lasts about 18-24 months.
again thanks for the information ...sounds like you've seen a few batterys ... according to your information it almost seems
like the battery would last longer with out using a battery minder...or maybe I'm reading with out glasses


Thanks again for all of you adding info ..it helps me with a better idea for a design
 

mikeyBoo

Senior Member
#14
hi newplumber,
If you choose to build your own charger, the following links might be useful for you:
(You would of course need to read the battery voltage to prevent overcharging).
The cool thing about the Picaxe is you could build custom charging profiles (some batt. vendors supply profile data).
Good luck with your project.

Easy Current Control via Picaxe PWM (0…350mA or 0…700mA)
http://www.picaxeforum.co.uk/showth...for-Constant-Current-Hi-Intensity-LED-Drivers

Easy Home-Made Current Shunts (calc.ed for US wire gauges) I’ve made small shunts using “furnace wire” from Home Depot (pretty accurate)
https://www.rcgroups.com/forums/sho...de-Current-Shunts-for-Measuring-Motor-Current
 
#15
hi newplumber,
If you choose to build your own charger, the following links might be useful for you:
(You would of course need to read the battery voltage to prevent overcharging).
The cool thing about the Picaxe is you could build custom charging profiles (some batt. vendors supply profile data).
Good luck with your project.
Thanks for that ....I am going to experiment with 18 gauge and a meter but what i don't know is
how can I read the millvolts with the picaxe and not let the 12 volts blow it up?
 

premelec

Senior Member
#16
There are a variety of curent ICs like this high side current monitor https://www.diodes.com/assets/Datasheets/ZXCT1009.pdf - basically sense a shunt and
convert it to current to V- ... You shouldn't weed much current in your app... note that at lower currents a cheap current source can be made from a LM317 regulator with a heat sink attached if needed. [see the 317 data sheet - one resistor + one 317 = regulated current].

High side current sense - TSC101C has 100x gain and higher price and better accuracy... Or LTC6102 for better yet... ;-0
 
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#17
Thats pretty cool premelec thanks ... never seen/heard one of those (zxct1009)
now a huge box of projects just landed in my brain which of course in turn pushed out some/alot of my memory :)


Well here is my first thought drawn up
I was planning on like during the winter months ...this battery tender could
charge/discharge every 3 days or so and see if the battery will last longer




soon i have to try testing on reading current which seems pretty cool
always something new
 

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manuka

Senior Member
#18
newplumber: Top marks on your very colourful "layout" ! However - as I'd mentioned before - your (probably ?) non critical yard needs may mean simpler approaches would suffice ? The more technology you have wintering out in the barn then then more there is to go wrong. Rodents may even set up home around a warm item,or overheating may start a fire...

Hence best elaborate on the tractor/mower's electrical load, engine (petrol or diesel & how large?) and the BATTERY itself - cost, type,Ah capacity,ease of removal for winter storage etc. What seasonal use does this tractor have -May to September perhaps ? WHAT WINTER SUN DO YOU ENJOY? WHAT DO YOUR NEIGHBOURS DO?

FWIW -I was raised in a highly mechanised NZ farming region (admittedly more Californian in climate that North Dakota !) where diverse reluctant battery techniques abound. Popular these days for starting/tending occasionally used appliances are Li-ion/LiFePO4 "jump starts" & small solar trickle chargers. Stan.
 

hippy

Technical Support
Staff member
#19
how can I read the millvolts with the picaxe and not let the 12 volts blow it up?
You can reduce that voltage with a resistor divider so it's within the PICAXE range and read it directly. Unfortunately you will also reduce the resolution of the millivolts above 12V.

Or you can use an op-amp to remove some of the voltage and have the PICAXE read what's left. What's left can also be multiplied-up by the op-amp. For example; if you want to read 11V to 13.5V you can subtract 11V leaving 0V to 2.5V and you can double that to provide 0V to 5V to the PICAXE.
 
#20
manuka said:
Hence best elaborate on the tractor/mower's electrical load, engine (petrol or diesel & how large?) and the BATTERY itself - cost, type,Ah capacity,ease of removal for winter storage etc. What seasonal use does this tractor have -May to September perhaps ? WHAT WINTER SUN DO YOU ENJOY? WHAT DO YOUR NEIGHBOURS DO?
Well I have three just cheap craftsman 42" lawn mowers and I don't know the battery info...but I do know they hold a charge like as a window screen holding water :)
I am going to do some testing and see if I change a bad battery into a good battery by charge/discharge...of course all of you know it wont work but I'm still going to try...cause I like when
someone says it can't be done and I agree with them only after I tried 100+ fire extinguishering different ways
and my mowing season is around may to october ...winter sun? lol..prolly when i'm indoors at 70*F and my neighbors are smart enough to follow the geese.
btw If i do make this project I will keep the battery/charger in a small weather box outside so if something does goes wrong it wont hurt anything
and thanks


hippy said:
Or you can use an op-amp to remove some of the voltage and have the PICAXE read what's left. What's left can also be multiplied-up by the op-amp. For example; if you want to read 11V to 13.5V you can subtract 11V leaving 0V to 2.5V and you can double that to provide 0V to 5V to the PICAXE.
That sounds pretty cool but i guess I need to look at more examples.
as to subtract 11v? I have read more on op-amps
 

Pongo

Senior Member
#21
We have a very short yard work season here between the wet season and the too hot/dry to safely mow season. I've wrestled with the same pathetic battery lifetime issue and tried most of what has been suggested above. Now with years of experience I am convinced that the lawn/garden tractor/mower batteries sold here are garbage and you may just as well add $40 to your annual maintenance budget and get a fresh one each season. I also have a Japanese mini tractor with a similar usage pattern. The battery on that is only slightly larger than the garden tractor battery but it's a regular auto battery as installed in small cars, it gives reliable service for years...
 

manuka

Senior Member
#22
newplumber: THREE lawn tractors - sounds quite a spread you have! Golf course ?

My long standing approach often means initially shelving technical solutions to first learn more about the user's setup. Questions may be the answer! Even the most trivial aspect(s) could be at the heart of a problem...
Hence the classic coffee mug saga -

Patient: When drinking coffee I get a stabbing pains in my right eye. Can tests to run to see if I have a caffeine allergy,eye problem or serious health condition ?
Doctor: Do you have sugar in your coffee ?
Patient: Yes.
Doctor: Ah - do you remove the spoon from the mug before drinking?
Patient: Doh!
Pongo: Thanks for your confirming experiences. Google reveals lawn tractor users from Alaska to Florida have similar woes. It increasingly seems mediocre materials in cheap batteries (~US$20) are the culprit...

However Sears Gold DieHard types (~ US $50) gain high praise, with some working 5-10 years before failure. These also have superior CCA (Cold Cranking Amps) than the budget types. Stan.

EXTRA:Classic secondary batteries (Lead Acid, NiCd, NiMH etc) are are of course now being seen off by superior Lithium based technologies. I'm a great fan of lightweight & mega reliable LiFePO4 types,& with 3.2 V per cell four in series conveniently give 12.8V. These may hence suit retro fitting in the normal battery bay- performance motor cycles are using them for weight savings. Check this lawn tractor offering - pix below.
 

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Pongo

Senior Member
#23
However Sears Gold DieHard types (~ US $50) gain high praise, with some working 5-10 years before failure. These also have superior CCA (Cold Cranking Amps) than the budget types. Stan.
There are only a couple of lead-acid battery manufacturers here but they sell under a plethora of brand names. DieHard is currently made by Johnson Controls who claim to be responsible for an amazing 1/3 of world lead-acid battery production. DieHard used to be made by Exide but that arrangement ended when both parties got busted for consumer fraud (selling used batteries as new). Sadly Sears is now circling the drain with many stores already closed or closing including my local one so I'm not sure if DieHards will continue to be available.
 

manuka

Senior Member
#24
Pongo: I recall that sorry late '90s battery saga,but the Exide versions should have long worked their way out.

Where in the US are you? Sears may sadly be shutting the stable,but there seem namerous other lawn & garden outlets in most states. I've lived in Canada (BC) & US (CA) so am aware of the seasonal, retailing & distribution issues that may arise

Stan. - half a world away in South Seas NZ
 

Pongo

Senior Member
#25
Hi Stan, I'm in the far north of California. Sears sold their Craftsman tool brand to Stanley/Black 'n Decker last year, I would not be surprised if they sell the DieHard battery brand too.
 
#27
manuka said:
newplumber: THREE lawn tractors - sounds quite a spread you have! Golf course ?
no just 2.5 acres of grass/toys/rocks that the mowers seem to spit out.
that's pretty neat for the scorpion battery ...wonder how it does at -20 F .
Also I read a little on skidoo snowmobile batterys ...seems they are using just super caps.

Pongo said:
Sears sold their Craftsman tool brand to Stanley/Black 'n Decker last year
I didn't know that ...I do believe sears and kmart are slowly going under...last time i was in kmart seems there was only
4 poeple in the store and 3 of them was wearing kmart uniforms.
 
#30
Thanks manuka ... never heard of warming up the battery


That is cool stuff premelec ...it seems for my simple understanding, big companys are in a race trying to build the mega capacitor which replaces all batterys.


FWIW I tried building a super cap...using coal,tin,bags,oranges,wife's important kitchen items,etc... and after alot of trials and errors, I gained 99.99% confidence
that its safer to buy them...plus they also work!


Has anyone used the INA219 ... datasheet V
http://www.ti.com/lit/ds/symlink/ina219.pdf
I searched the forum but nothing shows up ..it seems would be perfect
for reading the 12v battery since its max voltage is 26vdc
but I think the max current is 3.24
 
#32
Nope - I'd stick with the Diodes Inc ZXCTxxxx line of current monitors as mentioned early on... [look on Mouser.com]
Okay...I ordered a few of the ZXCT1009FTA from mouser....so on the bottom of the first page schematic, does the "Rout" resistor make a voltage divider to "Vout"?
So the value of the resistor will be the dividing factor of Vout?
 

premelec

Senior Member
#33
They make current output and voltage output units... the ZXCT1009 is a _current_ output unit so you choose the output resistor to give the desired voltage range you want to go into a READADC input pin [V = IR] - as well as choosing the shunt resistor to cause the current output... Voltage 'division' is not what is being done - the resistor 'changes' a current to a voltage... For various other units [pages of them...] :
https://www.diodes.com/search/q=zxct&t=keyword&action_results=Go&start=20

The ZXCT1009 is roughly 10 microamperes out per millivolt 'seen' on the shunt... however notice that there may be a zero shunt voltage output [offset] and the accuracy of this part is not very high [like its price] ... so calibration as installed is required... and the higher the shunt voltage you can use the better dealing with offset...
 
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