Have just inherited a Halfords Battery Charger from a neighbour. It says on it: ' Most suited for engines over 1800 cc' fast charge 7.5 adc. max battery capacity 110 ah Slow charge 5.5 adc max battery capacity 70 ah
Would that mean its not suited for use on my smaller 1600 cc Toyota engine ? Thanks
As far as I can see the engine size is mostly meaningless - they just seem to be using it as a shortcut to estimate the capacity of the battery - where larger engine will probably need more starting current and have hence have a larger capacity battery fitted.
I would guess they are just indicating what size of battery can be fully charged in ~15 hours.
So in short, it will be fine.
This sounds like an older dumb charger, based on a transformer and selenium rectifier.
Look at the ampere-hours number on the battery.
The objective is to charge at roughly C/10 rate.
A 50Ah battery, you would charge at roughly 5 amperes and it would take 10 hours.
Well, the battery is not really empty. It is only down about 13Ah. The other 39Ah are still inside the battery.
The 5 ampere dumb charger doesn't really supply 5 amperes.
After a few minutes the current is between 1 ampere and
3 amperes (I check for this, using a clamp-on DC ammeter).If the battery is healthy, it tends to "hold" the charging voltage to 14 to 14.5V or so. If it rises to 17V or so, the battery is in bad shape.
To replace the 13Ah at 3 amperes rate, takes four or five hours.
To read the battery voltage, disconnect the dumb charger, wait 24 hours, then take a voltage reading. Now, consult a temperature compensation table, which reads out battery voltages at the air temperature of the time you take the digital multimeter reading of battery voltage.
That will then tell you, how close to "full" it is.
The multimeter method is suited to sealed and maintenance batteries (six "water caps"). If the battery is sealed, you cannot use a hydrometer to check charge quantity. The hydrometer also has a temperature compensation table (should be on the package cardboard), to correct for air temperature at the time of reading. If the air outdoors is -10C, then the hydrometer reading would have to be pulled from the table entry for -10C.
The further away from 25C standard temperature you are, the more of a difference the table lookup makes to the charge determination.
It was my conclusion, after doing this stuff for a few years, that me and my dumb charger were only getting to within
50% of the correct fill value. In other words, the measurement methods are so crude, as to be "almost useless".You don't really want to be policing "100% fill" situations with a dumb charger. The dumb charger is good for times when you put enough current into the battery to start the car. Then, you drive the car around for 30-60 minutes and let the car fill it up.
Even cars don't always do a good job on regulation of the battery. Some Hondas, you will find complaints about coming out in the morning and the battery is dead. This is a combination of a phantom discharge path... but also is likely to be related to "sub-filling" the battery, and it does not have the amp hours in it that are supposed to be there.
*******Some of the prices I see on smart chargers right now, are ridiculously high, or I would have recommended you buy a smart charger (SMPS based) instead. Before COVID, there used to be some great sales on items like that.
Hopefully, this site will geolocate and give a price in pounds. I'm not saying to buy this one, just use it as an example.
Mine is missing that feature, so is not as good. I paid about half the price of that one for mine. My charger is also a bit lower on max charge current (SMPS constant current), and at
3 amperes, that's not really enough to de-sulphate an automotive battery properly.The worst feature on the little chargers... is the push button on the damn thing. They stick. They malfunction. And the charger casing is glued shut - no screws.
The smart charger, does Stage 1 and Stage 2, in this diagram. Stage one is CC (constant current). Unlike the dumb charger, which is all over the place on current, the smart charger is CC. The Stage two is CV and topping up takes place. This is how the smart charger "sneaks up" on full. And with the temperature compensation, it adjusts the full voltage value, for the air temp of the charger. Note that batteries and charger bodies do not track on temp - if you come home after a long drive and whip the charger onto the battery, the charger is 25C, the battery is 45C. Charging works best if the battery is at ambient, and when you bring the plastic charger outdoors, it rapidly approaches ambient too.
What I was seeing though, is a battery that would start low, and you'd check back in ten minutes and it was already at a high voltage (and a low charging current). (And this is a battery that won't start the car, which is why I would be charging it.)
I could understand your point, if the thing had spent several hours at 14V and had actually gone through an apparent charging phase. And "honestly" arrived at that point on the graph.
I'm just comparing to a known-good battery, where there is no faffing about and it sticks to the 14V or so range for long periods of time.
And the reason for the long periods of time, is my "6 amp" dumb charger, doesn't charge at nearly that current level when the battery is not completely flat. If the battery has any sort of fill level, the current flow tapers off and then the time-to-charge, can be a lot more than the desired target of ten hours.
That's where the smart chargers have the dumb ones beat, is in predictability.
And the smart charger has some ability to detect bad batteries, and should have a LED pattern indicating the battery is no good.
Paul
It's a weedy little charger and it won't do any harm. Just put it on slow charge and leave it overnight.
I should check the case isn't live if it's metal.
Bill
I only use a dumb charger for a short time to start charging an overly flat battery and then switch to a smart charger (often available from Aldi or Lidl for about 12 to 15 pounds), as the smart chargers refuse to charge from too flat.
Switching to the smart charger means that I can leave it on and not worry about forgetting it the next day and wrecking the battery through overcharging.
It is often possible to connect both chargers at once and disconnect the dumb one immediately, having fooled the smart charger into beginning to charge.
A common problem with smart chargers, especially if like me, you use recycled car and lorry batteries for electric fencers and lighting in a mains-free site.
To be fair to dumb chargers, properly designed ones drop to a low current provided all the cells are working, and at least for an unsealed battery should not be capable of wrecking it in a few days. The worst that will happen is that you will uncover the top of the plates and need to top up.
An indication of over-charging is if the battery gets warm.
If it's anything like my Halfords charger, those rates are to say the least optimistic. it might hit them early on in a charge, but very quickly reduces to well below the peak.
I have a cheap (£14) Lidl smart charger. Peak output about 4 amps. But it charges my battery to full quicker than the Halfords one which claims 11 amps peak.
The reason it refuses is because the reverse polarity protection involves a relay fed via a diode. Needs some volts from the battery to pull it in. If you use a jump start pack across the flat battery with the charger connected. you can disconnect the jump start pack almost immediately, and the 'flat' battery will charge from the smart charger.
But the same applies to my older and definitely not smart Halfords charger
- uses the same reverse polarity protection.
Totally fine
No. It means that it is fine for your car battery but it would be a bit too hefty for anything much less than a 50Ah battery.
C/10 charge rate is 10 hours nominally to fully charged and is about as fast as you really want to push it with a dumb charger.
Ballpark rule of thumb is
Charge time in hours = 1.1 x Ah of your battery / Charge Current
Better measured current output - they are always optimistic about it.
Dumb chargers are very useful for getting flat batteries up and going again since smart ones will refuse point blank to even start.
Only thing is set a timer and *remember* to disconnect it after at most
14 hours or you will damage your battery by over charging. (that is where smart chargers have the edge)Never let a lead acid battery remain flat for any length of time or permanent damage may result - as many people found out during lockdown.
FWIW my dumb charger is an elderly green Halford special and has no working meter at all. I can judge from the connection spark if it is charging. It's slow and fast rates are 3A and 6A respectively.
Ever inserted an ammeter to see the actual charge rate at start and finish of the cycle? A basic dumb one won't charge at its rated max for long. A smart one will charge at near enough constant current - meaning it does the job quicker, like for like in max. output.
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