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Passive Car Battery Trickle Charger

On Wednesday, March 3, 2021 at 8:46:08 PM UTC-5, snipped-for-privacy@kjwdesigns.com wrote :

te:

e system at different voltages and I'm agreeing with you. You seem to be sa ying you won't see this in the head lights because they run at the higher v oltage when the headlights are on, but you seem to be missing the point. Th at means the battery is charged at the higher voltage *regardless* of the s tate of charge. Doesn't everyone run with headlights on all the time? It's a law on some roads in Maryland. It's also a PITA in my car. I have to go i nto a menu to turn off the auto headlights.

fitted with them; neither of mine are. As you mention some states such as Maryland have running light requirements but not all, California doesn't ex cept for when windshield wipers are running. I just leave my Tesla and Priu s in their Auto modes.

ring the day - I would like the icon on the display to be active.

nsity.

How do you know headlights are run at a lower intensity during the day?

s on then the 12v rail will run higher voltage than otherwise in cars with these features.

Yes, that was my point, cars mostly just don't worry with trying to figure out how charged a battery is. To do that you need to measure both the volt age and the current watching for the current to taper off while charging at the higher level. Does anyone measure the current into the battery? I've not seen that. I've only seen where they measure the current out of the a lternator.

he 3000 page workshop manual.The Chevy spark, although an EV, shares a grea t deal with the Chevy Volt so I wouldn't be surprised if the 12v battery ma nagement is similar and maybe also to other Chevys.

attery Sulfation Mode (high voltage for a 5 minutes), Normal Mode (13.9-15.

5 depending upon SOC), Fuel Economy Mode (12.6-13.2), Headlamp Mode (13.9-1 4.5), Voltage Reduction Mode(12.9-13.2) and Plant Assembly Mode (Increased voltage(?) for the first 500 miles of the vehicle).

rrent, SOC, vehicle speed, windshield wipers, and a few other parameters.

.

How do they measure the battery state of charge?

I've been working on a project with a lead acid battery and figuring out th e state of charge while operating is not easy.

--

Rick C. 

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Reply to
Rick C
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I've made up a little 'confidence' indicator circuit:

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The voltage drop across the 1N5001 is sufficient to turn on the transistor whenever a current of more than about 100mA is flowing. The green LED indicates that a) the panel is sufficiently illuminated and b) it really is connected to the battery, rather than just generating enough voltage but perhaps disconnected without the user knowing.

The dark reverse current is around 1mA and it all fits inside a (slightly butchered) IEC connector.

--
~ Liz Tuddenham ~ 
(Remove the ".invalid"s and add ".co.uk" to reply) 
www.poppyrecords.co.uk
Reply to
Liz Tuddenham

I could measure no leakage current... I put a 1 k ohm R in series with panel and 12V battery. On the 200mV scale it read -000.01(0) maybe 10 uV... 10nA. This was at room temperature I think it should leak more if it's blazing hot out. (should I stick it in the oven?)

It's not at all clear to me that the ~200mA max current can hurt my smaller batteries... but I'm going to make a voltage limit with a 5W zener and some other diodes/ transistors... Maybe with a series Schottky

George H.

Reply to
George Herold

With the older batteries that had inspection holes, the excess energy was dissipated splitting up the water into hydrogen and oxygen. A battery left on prolonged trickle charge would need to be checked and topped up from time to time.

Modern batteries don't have antimony in the lead grids, so gassing doesn't occur below the voltage corresponding to fully charged. That means that as long as the maximum charging voltage is strictly limited, there should be no gassing or water loss throughout the battery's lifetime. In turn, that means the manufacturers no longer need to provide any way of checking the individual cell and topping up the lost water.

If you put them on a trickle charge that leads to a rise in cell voltage and gassing, no matter how gentle, they will eventually 'boil dry' and fail. There is nothing equivalent to the gas recombination action of sealed nickel-cadmium cells which would protect lead-acid batteries against water loss; even sealed lead-acid batteries have strict limits on charging voltage.

Reply to
Liz Tuddenham

The shortest route from western Michigan where my cousin lives to Rhode Island cuts through Canada, nice trip prior to Covid when they let you do that. Cuts a 14 hour drive down to just over 12

Reply to
bitrex

Great, so what's the maximum charging voltage? I've got a AC powered charger. On the 10A range it cycles between 14.2 and 12.9V. (When the battery is charged.) I'm checking the 2A range. It's about the same. I don't think my 0.2A panel can get it above 13 volts. (This is charging the smallest lawn mower battery.)

George H.

Reply to
George Herold

Depends on temperature. Hence the tactic of undercharging is often used to avoid temp comp.

That's why you feed a buck-boost converter from an MPPT controller!

I use a 48V panel to charge a 48V stack.

Reply to
Don Y

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