Passive Car Battery Trickle Charger

There are already products on the market that do just that. Solar panel car chargers that plug into the cigarette lighter to charge the battery. Work well enough outdoors from now onwards but useless in mid winter.

The only component needed is a series Schottky diode to prevent the panel leakage overnight outweighing the daytime charging gain.

Mine was from Maplin's going bust sale. It looks after the seldom used runabout car during the summer months quite happily. Though it is as well to turn the engine over every couple of weeks and move it slightly to stop the brakes rusting into the on state permanently.

Snag is some modern cars isolate the lighter when they power down.

Midwinter in the UK even professionally designed solar powered radar signs for "Please go round the dangerous bend" are dead in the water every frosty winters morning. They kill their rechargeable battery every winter too for good measure. There is one not far from where I live.

It lasts about two hours after sunset in mid winter when it might just make a difference to someone coming in too fast to go round the bend. The gaps in the hedging show just how (in)effective it is!

--
Regards, 
Martin Brown
Reply to
Martin Brown
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Don't forget to add in the hefty replacement battery cost into your "circui t" development costs.

Schumacher has been in the battery charger business for over 70 years. They manufactured the chargers rebranded and sold under the DieHard brand for c harging their batteries back when that name actually meant something. The p anels used in their PV chargers are customized for charging lead acid, they don't need any regulation, the current supply floats down to zero at somew hat less than 2.4V/cell. You're another one who should write a letter to th eir CEO detailing your refusal to use their product on technical grounds.

Reply to
Fred Bloggs

Sounds like they're using NiCd. Either that or some shit lighting technology.

Reply to
Fred Bloggs

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ce. I measured it delivering just 17mA into a 12.2V on the battery on a sun ny day. That's enough to keep it topped. I've been using three (SP-200) of them for over ten years and never got close to a battery problem. I can lea ve a vehicle parked six months and they spin right up when I start them. Th e main thing they're good for is not to keep the charge topped so much as t o prevent sulfate build-up on the plates. Apparently you don't need a lot o f current to achieve that. If you let the battery discharge for too long, t he sulfate makes the battery unsalvageable, it can't be re-charged ever aga in. The batteries I use are in the 100Ah range.

I'm not sure 17 mA is enough. It would take some calculations. I did that for a 2 AHr SLA and the self discharge rate came out to be 175 uA at room temperature. Higher temps give higher drains. Factoring in the much large r car battery and I think 17 mA would be marginal if working at all given t he duty cycle. On the up side, there is no worry about not having peak sun for a few days. It's all about the average.

--
Rick C. 

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Rick C

e:

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tice. I measured it delivering just 17mA into a 12.2V on the battery on a s unny day. That's enough to keep it topped. I've been using three (SP-200) o f them for over ten years and never got close to a battery problem. I can l eave a vehicle parked six months and they spin right up when I start them. The main thing they're good for is not to keep the charge topped so much as to prevent sulfate build-up on the plates. Apparently you don't need a lot of current to achieve that. If you let the battery discharge for too long, the sulfate makes the battery unsalvageable, it can't be re-charged ever a gain. The batteries I use are in the 100Ah range.

for a 2 AHr SLA and the self discharge rate came out to be 175 uA at room temperature. Higher temps give higher drains. Factoring in the much larger car battery and I think 17 mA would be marginal if working at all given the duty cycle. On the up side, there is no worry about not having peak sun fo r a few days. It's all about the average.

I did a double take and a double check on it, that measurement was right. I can attest to the fact the product works very well, and my vehicles get co oked alive in the sun here. I don't have the time to get into the details a nd second guess their design. That particular product as well as all their chargers get high ratings from the battery people. I certainly give it 5-st ars. I've been using them on three vehicles for a few years now without any problems.

Reply to
Fred Bloggs

There was something seriously wrong with your solar panel, then. My A4 sized one puts out around 500mA unless positioned directly towards the sun in which case this rises to over 600mA. A problem with modern cars which no one has mentioned yet is that they draw a lot of quiescent current for their various fancy features, so you can have anything up to 300mA or more being sucked out of the battery when the car's not being used. This must be taken into account so it's important to measure Iq when the car's left. Measure it with and without the central locking set and measure again an hour or so later as there is usually a difference for some reason as the car's systems settle down. The immobilizer is largely responsible for this, I believe. Anyhoo, your suggestion to get a SP200 is a cop-out. Of course I could buy some device from China that would do the job, but this is a design forum and I'd hoped for some design suggestions!! --

"Andrey Semyonovitch really was rather stupid; he attached himself to the progressive cause and 'our younger generation' from enthusiasm. He was one of the numerous and varied legion of dullards, of half-animate abortions, conceited, half-educated coxcombs who attach themselves to the idea most in fashion, only to vulgarise it and who caricature every cause they serve, however sincerely."

- Fyodor Dostoevsky

Reply to
Cursitor Doom

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actice. I measured it delivering just 17mA into a 12.2V on the battery on a sunny day. That's enough to keep it topped. I've been using three (SP-200) of them for over ten years and never got close to a battery problem. I can leave a vehicle parked six months and they spin right up when I start them . The main thing they're good for is not to keep the charge topped so much as to prevent sulfate build-up on the plates. Apparently you don't need a l ot of current to achieve that. If you let the battery discharge for too lon g, the sulfate makes the battery unsalvageable, it can't be re-charged ever again. The batteries I use are in the 100Ah range.

at for a 2 AHr SLA and the self discharge rate came out to be 175 uA at roo m temperature. Higher temps give higher drains. Factoring in the much large r car battery and I think 17 mA would be marginal if working at all given t he duty cycle. On the up side, there is no worry about not having peak sun for a few days. It's all about the average.

I can attest to the fact the product works very well, and my vehicles get cooked alive in the sun here. I don't have the time to get into the details and second guess their design. That particular product as well as all thei r chargers get high ratings from the battery people. I certainly give it 5- stars. I've been using them on three vehicles for a few years now without a ny problems.

Having no problems is not the same as the product actually working. I carr y a charm to ward off elephant attacks. So far, so good!

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Rick C. 

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Reply to
Rick C

ice. I measured it delivering just 17mA into a 12.2V on the battery on a su nny day. That's enough to keep it topped. I've been using three (SP-200) of them for over ten years and never got close to a battery problem. I can le ave a vehicle parked six months and they spin right up when I start them. T he main thing they're good for is not to keep the charge topped so much as to prevent sulfate build-up on the plates. Apparently you don't need a lot of current to achieve that. If you let the battery discharge for too long, the sulfate makes the battery unsalvageable, it can't be re-charged ever ag ain. The batteries I use are in the 100Ah range.

It might be that a meter was inserted inline to measure the current. It wo uld not take much additional voltage to impact the operation of the charger , making it think the battery was more fully charged.

If you aren't worried about the efficiency the only requirement is to reduc e the current when the battery is 100%. 17 mA would not even be enough to need reduction. 500 mA is also low enough to not harm a car battery. Then , as you say, the car itself is draining the battery, so that current must be provided by the charger before it can even start charging the battery.

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Rick C. 

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Reply to
Rick C

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practice. I measured it delivering just 17mA into a 12.2V on the battery on a sunny day. That's enough to keep it topped. I've been using three (SP-20

0) of them for over ten years and never got close to a battery problem. I c an leave a vehicle parked six months and they spin right up when I start th em. The main thing they're good for is not to keep the charge topped so muc h as to prevent sulfate build-up on the plates. Apparently you don't need a lot of current to achieve that. If you let the battery discharge for too l ong, the sulfate makes the battery unsalvageable, it can't be re-charged ev er again. The batteries I use are in the 100Ah range.

that for a 2 AHr SLA and the self discharge rate came out to be 175 uA at r oom temperature. Higher temps give higher drains. Factoring in the much lar ger car battery and I think 17 mA would be marginal if working at all given the duty cycle. On the up side, there is no worry about not having peak su n for a few days. It's all about the average.

t. I can attest to the fact the product works very well, and my vehicles ge t cooked alive in the sun here. I don't have the time to get into the detai ls and second guess their design. That particular product as well as all th eir chargers get high ratings from the battery people. I certainly give it

5-stars. I've been using them on three vehicles for a few years now without any problems.

ry a charm to ward off elephant attacks. So far, so good!

Prior to installing these SP-200 I was losing batteries all the time due to sulfate contamination. Now I don't lose any. I call that "working." Pre-pa ndemic they were only about $18.00, now they're about $28.00. They're avail able everywhere, Amazon, WalMart, HomeDepot, some of the auto parts stores. They're also good for seasonal stuff like tractors, any kind of lead acid electric start machine that can have a long down time.

Reply to
Fred Bloggs

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n practice. I measured it delivering just 17mA into a 12.2V on the battery on a sunny day. That's enough to keep it topped. I've been using three (SP-

200) of them for over ten years and never got close to a battery problem. I can leave a vehicle parked six months and they spin right up when I start them. The main thing they're good for is not to keep the charge topped so m uch as to prevent sulfate build-up on the plates. Apparently you don't need a lot of current to achieve that. If you let the battery discharge for too long, the sulfate makes the battery unsalvageable, it can't be re-charged ever again. The batteries I use are in the 100Ah range.

d that for a 2 AHr SLA and the self discharge rate came out to be 175 uA at room temperature. Higher temps give higher drains. Factoring in the much l arger car battery and I think 17 mA would be marginal if working at all giv en the duty cycle. On the up side, there is no worry about not having peak sun for a few days. It's all about the average.

ght. I can attest to the fact the product works very well, and my vehicles get cooked alive in the sun here. I don't have the time to get into the det ails and second guess their design. That particular product as well as all their chargers get high ratings from the battery people. I certainly give i t 5-stars. I've been using them on three vehicles for a few years now witho ut any problems.

arry a charm to ward off elephant attacks. So far, so good!

to sulfate contamination. Now I don't lose any. I call that "working." Pre- pandemic they were only about $18.00, now they're about $28.00. They're ava ilable everywhere, Amazon, WalMart, HomeDepot, some of the auto parts store s. They're also good for seasonal stuff like tractors, any kind of lead aci d electric start machine that can have a long down time.

That's fine, but you didn't say that. How do they connect to your car's ba ttery?

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Rick C. 

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Reply to
Rick C

ice. I measured it delivering just 17mA into a 12.2V on the battery on a su nny day. That's enough to keep it topped. I've been using three (SP-200) of them for over ten years and never got close to a battery problem. I can le ave a vehicle parked six months and they spin right up when I start them. T he main thing they're good for is not to keep the charge topped so much as to prevent sulfate build-up on the plates. Apparently you don't need a lot of current to achieve that. If you let the battery discharge for too long, the sulfate makes the battery unsalvageable, it can't be re-charged ever ag ain. The batteries I use are in the 100Ah range.

There are standards for that and the UK is probably different from U.S. I c an tell you definitively that 300mA is WAY out of line. Even 30mA sounds h igh. Find that circuit and pull the fuse, it's dumb.

Haha- have it your way, spend $250 to do a $20 job, it's your money.

e

e,

Reply to
Fred Bloggs

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in practice. I measured it delivering just 17mA into a 12.2V on the batter y on a sunny day. That's enough to keep it topped. I've been using three (S P-200) of them for over ten years and never got close to a battery problem. I can leave a vehicle parked six months and they spin right up when I star t them. The main thing they're good for is not to keep the charge topped so much as to prevent sulfate build-up on the plates. Apparently you don't ne ed a lot of current to achieve that. If you let the battery discharge for t oo long, the sulfate makes the battery unsalvageable, it can't be re-charge d ever again. The batteries I use are in the 100Ah range.

did that for a 2 AHr SLA and the self discharge rate came out to be 175 uA at room temperature. Higher temps give higher drains. Factoring in the much larger car battery and I think 17 mA would be marginal if working at all g iven the duty cycle. On the up side, there is no worry about not having pea k sun for a few days. It's all about the average.

right. I can attest to the fact the product works very well, and my vehicle s get cooked alive in the sun here. I don't have the time to get into the d etails and second guess their design. That particular product as well as al l their chargers get high ratings from the battery people. I certainly give it 5-stars. I've been using them on three vehicles for a few years now wit hout any problems.

carry a charm to ward off elephant attacks. So far, so good!

e to sulfate contamination. Now I don't lose any. I call that "working." Pr e-pandemic they were only about $18.00, now they're about $28.00. They're a vailable everywhere, Amazon, WalMart, HomeDepot, some of the auto parts sto res. They're also good for seasonal stuff like tractors, any kind of lead a cid electric start machine that can have a long down time.

attery?

You have two options: 1) cigarette lighter adapter or 2) battery clips. The connecting cord is about 10' so no problem whichever you go. Panel sits on the dash below the windshield. It has to be taken down when you want to dr ive off. The manufacturer recommends disconnecting before you start the veh icle.

Reply to
Fred Bloggs

Even heavy duty batteries are dirt cheap so it's really not an issue. Dunno what it's like where you are but here I pay the equivalent of only about US$200 for a HD battery from a really *excellent* manufacturer like Compton, Exide or ACDelco and I'm talking 900CCA plus for that price. --

"Andrey Semyonovitch really was rather stupid; he attached himself to the progressive cause and 'our younger generation' from enthusiasm. He was one of the numerous and varied legion of dullards, of half-animate abortions, conceited, half-educated coxcombs who attach themselves to the idea most in fashion, only to vulgarise it and who caricature every cause they serve, however sincerely."

- Fyodor Dostoevsky

Reply to
Cursitor Doom

That's premium battery in U.S. $100 tops gets powerful and long lasting ACDelco type around here. Still, your in progress circuit development is $200 and counting.

Reply to
Fred Bloggs

My supplier, who's an ACDelco distributor, is always complaining about how those batteries are made in China.

Reply to
Fred Bloggs

This sounds like it's becoming needlessly overly complex. The idea is to be able to make it from readily available junk box parts and it needs to be passive so running solely off the power from the solar cell, the specs of which are on the diagram. --

"Andrey Semyonovitch really was rather stupid; he attached himself to the progressive cause and 'our younger generation' from enthusiasm. He was one of the numerous and varied legion of dullards, of half-animate abortions, conceited, half-educated coxcombs who attach themselves to the idea most in fashion, only to vulgarise it and who caricature every cause they serve, however sincerely."

- Fyodor Dostoevsky

Reply to
Cursitor Doom

Just chiming in for a second on something just mentioned.

If you can, avoid the 10 minute every week or two thing. Automobile engines produce quite a bit of H20 in their exhausts and that water will accumulate in the exhaust system, especially the muffler, and contribute towards rusting out the muffler pretty quickly.

An answer is to run it more like 20-25 minutes every 2 or 3 weeks, so that the entire exhaust system gets up to full temperature and drives out the moisture that has condensed in the system.

Better yet, and since automobiles don't charge all that efficiently at idle anyway, drive it down the road to the store back or similar every so often.

Or just have a trickle charger as the thread is about. Modern engines sit just fine for a couple of months as long as a charger is on.

Ray

Reply to
Ray Otwell

A simple circuit called "disconnect the battery so it don't sit there discharging" would be cool

Reply to
bitrex

Sure would be. Disabling the immobilizer would invalidate your insurance! --

"Andrey Semyonovitch really was rather stupid; he attached himself to the progressive cause and 'our younger generation' from enthusiasm. He was one of the numerous and varied legion of dullards, of half-animate abortions, conceited, half-educated coxcombs who attach themselves to the idea most in fashion, only to vulgarise it and who caricature every cause they serve, however sincerely."

- Fyodor Dostoevsky

Reply to
Cursitor Doom

Yeah, but some current meters are a bit funny about when the starter is spun over. :-D --

"Andrey Semyonovitch really was rather stupid; he attached himself to the progressive cause and 'our younger generation' from enthusiasm. He was one of the numerous and varied legion of dullards, of half-animate abortions, conceited, half-educated coxcombs who attach themselves to the idea most in fashion, only to vulgarise it and who caricature every cause they serve, however sincerely."

- Fyodor Dostoevsky

Reply to
Cursitor Doom

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