Automatic vs. Trickle Charger for Car

The automatic charger shuts off when battery is fully charged, the trickle charge current is continuous....

..." the critical difference lies in the chargers' ability to automatically shut off the charge current and not overcharge batteries, which can lead to overheating and serious damage. "...

http://www.pulsetech.net/assets/Misc/Trickle-vs-Maintenance-Chargers.pdf

Since the URL you gave led to PulseTech, I have a couple of questions that perhaps Andy or others can respond to.

The PulseTech desulfating system sounds great; except I have found no independent evaluation of their system. Until then I need to consider PulseTech as an overpriced charger.

I have had OK luck with both Harbor Freight and Battery Tender float chargers.

I actually, without full proof, do believe they make a difference. But I'm fully prepared to be wrong when someone finally proves it....

Up to now it simply has not been proved either way.

The simple pulse units are very cheap here, under US$20, so I connect one inside my chargers.

I do believe that it does no damage.

I do also believe that it was the "New Scientist" that thought they were good, but its probably 20 or more years ago now, maybe longer....they are usually a good source.

Automatic chargers are more expensive, but work better.

How Do I Pick a Battery Charger! - BatteryStuff.com

Car Battery Charger: Charger Mysteries Revealed

Not quite sure what you mean by automatic, I take it that it's a float charger, you use a float charger if you plan on storaging you battery for a period of time.

Same thing, I believe. Need to store car for 4 months in MN (very cold here) but how does the float feature work? I was told my trickle charger might overcharge and damage the battery. Harbor Freight has a float charger for $ 13 (incl.shipping), wondering about the low price.

It's on sale. Sale: $5.99

I've bought lots of things from them.

No complaints here.

HAD TO GIVE YOU A GA for that great and really accurate comment.

You are basically the first person that I have seen here that REALLY understands how lead acid batteries need to be charged/handled.

What many here do not understand is that a trickle charger HAS TO BE SET UP/ADJUSTED FOR each battery individually, taking into account battery style, battery age, battery temperature......to name but a few, and to never actually increase charge as most do, thereby shortening battery life dramatically.

Which is why I never use trickle charging myself in my own design chargers. Too many parameters to get right...though a small microchip could do all that nowadays, but why bother?

AND the battery is not "exercised" either.....(my name for charge/discharge cycles)

I charge my batteries up to 13.7 V approximately. Switch off. Wait till 12.6 volts is reached and then switch on and charge again. This basically means (depending upon style )that the battery is at around only 70% charged....but it is the most energy efficient area of charge.

Higher charge levels drop the efficiency quite dramatically, ignoring any possible damage as well, and gassing etc!!

Basically exercising the battery.....(I call it!!) Using full charging current of around 10 amps (C/10 or less) (depending upon battery size!) each time.....No gassing and I forget how long ago it was that I had to add some water.....a year or so.

My 12 volt 125 amp leisure caravan battery for example, is over 11 years old and appears to be liking the charging style, winter and summer.

If it craps out tomorrow, I am still very happy.....

Hello Andy.

I have an automatic Victron Inverter/charger on my narrowboat fed by a 230vac mains land line that I keep switched on all the time to charge the batteries to full capacity when moored up.

I have never trusted the 'automatic' aspect because a previous set of batteries seemed to lose capacity - where supposedly fully charged - ran down quickly when compared to similar use in previous years.

I put this down to 'overcharging' in trickle mode albeit the charger was automatic, but I don't think it switches the current to zero off when fully charged.

So I fitted a 13a timer socket on the boat - set for a couple of hours a day. This keeps the batteries at 100% capacity.

In your case, and it makes sense, to switch an ordinary charger on/off at the preferred voltage - you do not say if this is by a voltage sensitive switch, or whether you do this with a manual switch and voltmeter.

Please advise.

Its voltage sensitive, this is a reasonable indication of SOC/capacity.

I don't remember the chip concerned, but it switches a triac on and off between the two set voltages. Set by two pots.

The circuit just needs a milliamp or two and is powered directly by the battery on charge, not directly from the mains.

That is so there is NO current drawn from the mains when "Off".

But this means that a deeply discharged battery may not power the circuit, (this can happen with leisure deep discharge batteries) so I add a "force charge" switch, usually for say 15 minutes and then the charger can usually run in normal mode again, that is once above around 6 volts (on a 12 volt Battery).

I switch a triac on and off (quieter than the relay I used before!) to turn the charger on and off.

Its a transformer to a full wave rectifier, with smoothing...pretty standard......ring(?) transformer for low noise (both types) cheap to buy for halogen lamps and efficient operation.

I do not recommend EVER to charge to over 70% capacity 13.6 - 13.8 volts, that way you are using the mains more efficiently (efficiency drops off dramatically over about 70% depending on battery manufacturer) and you extend the lives dramatically of what might be an expensive battery or two...

There is NOTHING like regular 100% charges to damage a battery, gas off the water and lower its capacity/shorten its life. Its why some car batteries don't last more than 3-4 years at best.....a few longer and a few shorter....

Remember, charging to less than 13.8 volts there is next to no gassing and water loss!! Also a plus....

Pick your needed capacity and buy batteries that achieve that at 70% (from memory) of their capacity.....

Some large LA batteries can be 50 or more years old, but they have been PROPERLY looked after.....as some Telephone exchange backup batteries can be.....and then they are over 90% recyclable when "broken"!....

I forgot to mention, that a trickle charger really needs well designed active circuitry, so that it maintains the SOC/capacity at where you want it, no matter what the age of the battery, its size, or the outside/inside temperature or anything....

Actually a pretty simple job that as far as I can tell, almost no charger is actually designed to do properly !! Maybe somewhere in a far off galaxy......

At least none of the ones I have checked achieved it properly, usually too high a charge level, over charging was the usual result....

I simply don't even bother with it, even if properly implemented I still see it as having a negative effect on the battery life anyway.....

Thanks Andy.

It looks as though I have been doing it wrong for years. I have batttery management meter panel that tells me how much % charge there is - and I have tried to keep it at 100%.

Are the voltages you quote 'on charge' at the designed charging current. Or off charge?.

I have ringing my ears from RAF National Service training days days of "fully charged on charge - 14.7 v". The current on-charge was at the 10 hour rate - aircraft batteries had to pass a "high load" test to check internal resistance and efficiency before and after charging. If they failed they were transferred to mechanical transport service - and then if failing a lesser test - were scrapped.

I don't bother with all these tests. We run our boat batteries until we get problems with too many 'flat' battery warnings - they are not flat as such - that is when the bleeper flashes. We charge them more often or replace them if it becomes a nuisance - such as the TV going off at critical times - which means running the engine - which is a bit anti-social in the evening if moored up with other boats.

So perhaps 80% might be better to try - then run the batteries down to what? 60% - 70% ?? - but I need to check voltages first.

This is just from memory, so exact it is not and I am talking about averages, not every single battery in the wold with a LA construction.

My personal take, but its only been 11 years with a single Varta leisure battery in my caravan, so its not guaranteed for all, but I did have many years of LA batteries experience in the RN and privately.

But it was never a proper "scientific" approach.....just my RN knowledge and years of hands on....

I do use and believe in this small easy to understand document, its my basic "Bible":-

http://scubaengineer.com/documents/lead_acid_battery_charging_graphs.pdf

It is fairly well known that at around 70% of capacity (as you can see from the first diagram), you have the "sweet spot", that first 70% requires relatively little energy to charge, but after that point is where many batteries need more energy to charge per percent. e.g. efficiency drops even lower.

This is why its best to have a physically larger battery, being "under used" I feel. I also find that Leisure type are better, provided the engine starting battery is a separate battery, not of the leisure type.

Leisure batteries can handle a deep discharge far better than say car batteries....

I tend to use around 13.6 to 13.7 volts as my upper charge level. Simply because this usually precludes gassing and water loss for most types. Gassing appears to shorten the working life.

You can see that the charge rate has a major effect on the actual voltage at that point. The charge rate is the battery capacity "C" in amps, over the charge rate in amps. So for a 100 A/H battery, charging at C/10, is 10 amps. Simple.

I tend to use usually around C10 for my leisure batteries, a good balance between reasonably fast charging and long life.....

Most LA batteries, if allowed to sit at a voltage below around 12.5 volts for long periods, will start to sulfate. So I use this as a lower voltage at which I start charging. So the battery, without even drawing any current, will idle when a charging voltage is available, between those tow points on my charger...

This appears to keep the battery "busy" and "fit" is all I can say.

While underway, my battery is basically at the end of some quite long cables and it is also feeding the fridge. So it is charged by the car 120 amp alternator, but discharged by the fridge. The end effect is that the 14.5 v Car alternator voltage is down to about 13.7 v, so no overcharging occurs.

If it had, I would have simply fed the battery, from the alternator via my charger to reduce that, it has never proved necessary....but should not be simply ignored. You may need to reduce the charge if the cabling is short in some manner....

When on a camping site, the fridge is switched to mains or gas if there is no mains available (the BEST camping sites!), not left on 12 volt battery.

I have to get ready to drive my wife now for a hospital checkup, if you have any questions, I will answer them later.

Thanks AndyG. I will check voltages and study the Victron manual to see if voltages cab be adjusted to suit.

But coming from a different direction - where previously we have been talking about the OP 'Automatic v trickle' and the best way to keep batteries fully charged - what is the voltage for safe minimum charge for storage - then to fully charge when needed.

Actually, once the acid is in, they need to be kept at about 13.6 volts, in a cool ventilated place for storage.

A very small "power wise" intelligent charger should be enough....say a 1 amp version.

This is what the battery university recommends:-

How_to_store_batteries

Thank you. Looks like a good source.

AndyG. Thanks for the link. Reading that will keep me out of mishief for a while.

LOL!!!

I don't personally agree with everything they say fully, but its still one of the best sites I know.....

Anyone, regularly charging/using LA Batteries to more than 70% of capacity, should realize that battery life will be affected.

Sometimes this shorter life/higher capacity is even acceptable to allow a physically smaller/lighter battery to be used in vehicles for example.

I trickle charge is a battery charger. It may have a timer, but it charges and will not stop charging until you stop it, unless it has a timer. A Float charger will maintain the battery with a charge.

For storage you use a float charger. As far as HF, read the reviews of their float chargers.

I was thinking of buying one also from them.... Some of their product is comparable in quality to others, but some of very cheap and does not meet its claim.

ps

I see lyn had some good results.

So how does float charger stop overcharging the battery? (just like a trickle charger does).

If its properly designed!

At least some of the ones I have tested simply seem almost to never stop charging, eg. cheapo design.

Circuitry

Lots of good information here, but also some very important information, as far as I can see, is not even mentioned.

But many thanks for drawing our attention to it.

A typical error of many battery Websites.

It is a really good start, for which I thank you for, but missing much VERY important detail, or at least I did not see it prominently displayed......as it should be!

No information about SOC

No information about Capacity

No information about gassing

No information about possible water loss

No charge levels mentioned using specific voltages

No mention of that floating a battery at full charge will actually seriously reduce battery life, possibly ruining the battery completely if kept at full charge for say 3 months.....drying out being a very possible effect......

No mention that a good float charger should either be adjustable to a lower voltage, or fixed (best) to only charge to just below the gassing voltage

I could go on, but that should be a small indication of what is missing. This website is not alone either.....

I am still grateful that you took the time to post it for us all, may thanks.

The Battery University, is probably one of the best battery websites around, with lots of good infos, has similar failures, sadly.....fewer maybe, but still there......

I would love to find a website that covers everything 100%, but I think that I am asking too much.

I still find that the .pdf that I recently posted on this blog, if read and fully understood, to be as good as it gets online.....though I would be stupid to try to imply that its perfect, its simply not!!

You website and the pdf combined, would probably be pretty close to being perfect, one covering what the other missed out on!!...

I agree unfortunately, gassing is very important, as well as a lot of those should have been at least mentioned for an introduction so that from the start its made aware.

You are dead right phoenix911, I agree fully and many thanks for your post.

You obviously know your way around LA batteries, you are a rare person here indeed.....

I had to laugh though, some other "ignorant wanker" gave me an OT!

How childish!!

But who really cares.

The opinions of such people are simply unimportant in the great scheme of things as they will simply remain pig ignorant all their lives in more ways than anyone can count.....

Their loss!

They know who they are, I can also make a very good guess!! He will never ever change......

you too kind,...... really

But thank you

Don't take the OT to heart AndyG. I have voted to negate it.

I have learnt a lot of useful things about LA batteries that are very relevant to my situation - so a GA from me - and thanks also to Phoenix and others, and the OP for starting the discussion.

One final thought: Normally batteries are kept charged to provide instant power when needed. If instant power is not needed, the alternative is to do nothing at all. So what harm is there just leaving the batteries disconnected and off charge - and then charging them up when needed ?

Thanks for your very kind comments and actions on the OT.

I readily admit to not not being a seeker of GAs, but not OTs either!! Your action was excellent!

Thanks.

So, onto your post:-

LA Batteries are really only good for relatively short term storage and are quite inefficient, even when only used below 13.7 volts....

You need to keep a lead acid battery, one that is not a "leisure" type or any other that can handle "deep discharge" safely, above approximately 12.5 volts. 13 volts should be perfect, or as I do it, cycling between 12.6 and to around 13.6 volts = no gassing and no sulfation - hopefully!!.....

12.5 volts is the approximate point at which sulfation starts as the battery self discharges, which they all do.....some slowly, some not so slow...different batteries different sulfation point, different self discharge rates.

Also a partially or fully discharged battery can easily freeze in winter. Keeping it reasonably charged keeps the acid strength higher and far less likely to freeze.

I actually keep my leisure battery always above that 12.6, just to be on the safe side, but it should not be needed officially as long as it doesn't get too cold.

I hope this was helpful.

So what harm is there just leaving the batteries disconnected and off charge

Batteries will still discharge even when its not being used.

Its actually a maintenance issue of the battery.

Float charging manages the service life and efficiency of the car battery.

When you fully discharge the battery where it would require a deep charge, this will effect the life and output of the battery.

I'm not sure what temperatures you expect there as we really don't know what cold is here in Australia, but what is meant by overcharging is both excess heat and water loss due to outgassing.

Over temperature is unlikely to be a problem if using a trickle charger in a very low ambient environment so you can pretty well forget that problem.

Outgassing is when the water in the electrolyte begins to evolve into its constituent parts of Oxygen and Hydrogen, and will only occur as the battery approaches full charge, and is dependent on battery temperature as outlined below.

In a flooded type battery those gasses escape into the atmosphere and water must be added to compensate.

In a VRLA battery the gasses generally recombine, but under adverse conditions they can cause the safety valve to open and release pressure in the case. This basically spells the end of that battery as the water cannot be replaced.

Whether this will be a concern for your situation depends on the storage temperature of the battery.

A battery at a cell temperature of 69°F will begin gassing at a cell voltage of 2.415v or 14.5v for a 12v battery. Drop that temperature down to 0°F and the gassing will not begin until cell voltage reaches 2.97v or 17.82v for a 12v battery. It's pretty much a straight line between those two extremes, so you can extrapolate your own temperature/gassing level.

It is unlikely that any proprietary brand trickle charger will supply a float voltage much in excess of 13.7v and definitely never higher than 14v, so gassing in a low temperature environment is also highly unlikely if a trickle charger is left on indefinitely.

Bear in mind that rate of self discharge drops considerably as temperature falls, Calcium types will lose far less than Antimonials.

Don't allow your battery to become discharged....As a LA battery discharges, the electrolyte becomes closer and closer to pure water (the Sulphuric acid is absorbed into the plates), and so allowing your battery to become severely discharged under very cold conditions could cause the electrolyte to freeze and so rupture the case.

Typically, a fully charged battery - rested OCV of 12.7v/SG at 1.265 would freeze at -65°F whereas one at just 25% state of charge - rested OCV of 11.75v/SG of 1.15 would freeze at 5°F.

With the XtremeCharger XC-100 nominally desulfanating pulse charger, I have brought two seriously depleted (less than 7 volts residual) 12 v lead acid batteries back to life well beyond their 36 month service life. (Both were in boats.)

First, I checked for shorted cells, which, of course, is unrecoverable. Then I placed the XC-100 on the posts of a good fully charged battery that is jumped to the depleted battery. It takes 1-2 days to get the reading on the XC-100 to make its first indication of charge acceptance by the pair, then I disconnected the slightly depleted good battery, and went straight to the seriously depleted battery, now reading about 8-9 volts of potential. The recharge to 100 per cent reading takes about 2 days.

I did a single cold crank test with headlights on (pick-up truck) with one of the renewed batteries compared to almost new fully charged battery, timing to the point of noticeable (audible) loss of cranking RPM for each. I then checked the XC-100 charge state indicator, finding that both were at 25 per cent. The new battery exceeded the cold cranking time by almost 30 per cent of the renewed battery.

The renewed battery is now installed in a regularly driven pick-up truck with one of Xtreme's "parasitic pulse chargers" installed. At almost a year, no problems. At this point I am "thinking" that the "parasitic pulse charger" is further renewing the battery through Xtreme's proprietary pulse desulfanation process. As I recall, the combined cost of these gadgets is a bit over $100, well on their way to paying for themselves.

Now what may be interesting for you is that some shorted cells can be recovered by emptying out the shorted cell, and removing/flushing out all the debris that is usually (but not always!) shorting the cell plates out at the bottom, remember, its fallen out from the plates, which is a bad sign!

I believe its possibly caused by a cell that was allowed to run at least partially dry.....eg. gassing too much.

Then replacing the acid, charging and re-adjusting the acid concentration. It will not "live" as long as the other cells, but it may give it some useful extra Battery life. Especially worth doing in large expensive batteries.

Never done it myself, but was taught how to do it over 50 years ago....by the way, thats all from memory!!

Remember, any battery, any type, any chemistry ALWAYS has one strong cell and one weak cell, no matter how many cells are in the battery!

In LA batteries the weak cell is further weakened when doing a full charge to say 14.5 volts or so......(actually, this is basically true of the other types too, which is why its better to charge a battery, by charging each cell individually, but often not possible due to the physical design!)

This "poor" weak cell is then reverse polarised when it is empty first!!

These two points demonstrate clearly that charging to full and discharging to empty, simply accelerate aging of the battery, by damaging the weak cell first!!

Thanks, Andy. I am working my way toward large, expensive batteries. A while back, I saw a video of some Asians in a sweat shop type environment tearing apart, cleaning and rebuilding a very large (I was thinking an old submarine) battery. So, naturally, I have been wondering if there may be a source for battery housings (cases) that could be used to reconstruct, say, golf cart and larger batteries cast in seal housings after those housings were demolished for access to the plates, etc.? If this wheel does not exist, maybe we could invent one, given the number of high-priced batteries in use and expected to be in use for the brave new world of intermittent and mobile renewable energy.

You can make batteries out of plywood, doped with tar, but today, fiberglass may be better, painted onto the wood.

In WW2, my father was sent to Turkey by Churchill to train the Turkish army. They had trucks but no truck batteries so he made them!! So I know its possible, but I have never done it. Think safety, LA batteries can be dangerous!.

Look here, it may help:-

Homemade Lead Acid Batteries Complete Guide

I hope this gives you some good ideas.

Thanks. I may jump into this when I am lining up my projects for 2016.

Received and hooked up the Automatic Charger from Harbor Freight. Decent-looking piece of gear (actually bargain at $14 incl. shipping). Hooked up to car, voltage at battery terminals read 13.45 volts initially. Next day (maybe 15 hrs. later) voltage is 12.85 volts and has stayed at that since. Have not driven car since connecting charger. I assume the charger is supplying the low current the car's utilities and memory consume while resting. Seems OK to me.