Trickle Charger

eadmr04

eadmr04

Member
I have a mains trickle battery charger for my P6b and wanted to know if you should leave it on constantly when car not in use or should you turn it on and of every now and then. I don't use the car that regularly but it gets a decent run every now and then. I was concerend that I may be overcharging the battery?
 
Very good question and a very difficult topic, as there is no truly satisfactory answer. Trickle charging on a continuous basis definitely will cook the battery, in fact it will boil it dry! To work you would have to get the trickle charge current to exactly match the natural rate of decay of the battery plus any loads (eg the clock) that run with the ignition off - a very small current indeed and almost impossible to replicate. Plus the overall effect would be to damage the plates so that, although charged, the battery was no longer able to deliver the high current burst to operate the starter. Oh dear! It's as bad if you simply disconnect the battery and let it naturally discharge and then charge it up prior to wanting to use it.

The basic problem is that the action of a short very heavy discharge followed by a rapid recharge has been taken as the normal operating regime when designing the battery. Any other regime tends to clog up the pores in the plates and render them unable to perform when required.

The nearest I've seen anyone come to a successful charging regime is "pulse charging". In this the battery is allowed to run down naturally for a period - normally between 5 minutes and a 1/2 hour - while being monitored by a very sensitive voltmeter. When the battery reaches a preset level of discharge the voltmeter triggers a very heavy pulse of charging current for around 1/2 sec to restore the charge level.

I ran a fleet of small, car size engine, standby generator sets which were required to start up without fail in the event of a mains electricity failure. Such failures are pretty rare in this country - say 4 to 6 a year per set on average - so the duty was quite similar to what we want from our classic cars. With trickle charging the batteries were a complete nightmare - and we used really sophisticated trickle chargers with built in regulators that related the charge current to the charge state of the battery! With pulse charging we could get a couple of years 100% reliability from each battery.

Even so, pulse charging will not deliver the same sort of battery life as if you were using the car every day. I'm afraid it's a fact of life that the less often you use the battery the shorter its life! The opposite of natural assumption!

There are pulse chargers advertised in the classic car magazines or do a search on Google - I'm afraid I'm not familiar with what's available now.

The other moral of this tale is to buy cheap batteries frequently rather than trying to buck the underlying physics by buying good quality ones!

Chris
 
I've just bought a charger that monitors the battery voltage and cuts off at 90% full charge .I assume it cuts in again when the voltage drops.

Previously I'd been using a charger I found in my loft when I moved here 16 years ago .It put out the amps but would bubble away the water in the battery if left unnattended
 
Ctek make good chargers for this type of application, have a look at http://www.ctek.com
Not cheap though, probably cheaper to buy a cheap battery every 3 years, if you go to a autoelectrical wholesaler you can often get batterys for < £30 usually with 3 year guarantee.
As long as you disconnect the battery when the car is parked for more than a few days you should get decent life. I had a removable cut off key-switch (same as a race car electrical cut out) that disconnected the battery from the rest of the car, without having to get the spanners out.
 
Hello each,
I have used the Draper Battery Master for many years with no problems. This unit is designed to be left connected and on for "extended periods of time" and my Three Thousand Five was always connected whilst in the garage.
I bought it from Halfords for £20 although I believe it could be bought cheaper elswhere.
Hope this helps.
regards, John.

p.s. Dom, you must have this Draper unit that I gave you when you purchased the car!
 
My battery is old and ran flat . My new high tech charger wouldn't charge it because I assume it would take too much current. The old charger ( must be 30 years old ) did the job , no bother

So never throw your old equipment away - it will come in useful
 
I build my own trickle chargers and leave them permanently on, a properly designed charger will not "cook your batery" or "boil it" they should be set up to charge at exactly 13.8 Volts and may be left connected year in and out.
Another method is to use a solar panel and a regulator. I use both methods at the moment as I have several cars which are rarely used and the cost of replacment batteries is too expensive.

Graeme
 
I have been wondering whether theres some sort of small solar gizmo that could charge the battery from the rear parcel shelf of our P4 when shes sitting around.
 
Most of the solar panels I have seen that are designed for that purpose are inadaquete for the task for a number of reasons. Most lead acid batteries in good condition (like new) self discharge at approx 100 milli amps (mA) 24/7 older batteries are much much worse 200 to 400 mA, then you generally have other ancillary items in the car such as the clock which also have a continous drag on the battery, yet these chargers struggle to provide 100 to 200 mA in good sunlight and then only for a few hours out of the 24 available. To put it plainly it's like bailing a sinking boat with a teacup. Another disadvantage is of course the UV rays that you are inflicting on your car whilst in the those sunlit conditions.
My solar charger consists of 3 lower power panels in parallel (6, 4, 2 watt panels) which are placed on the garage roof and then go to my regulator which I have set up for 14.4 Volts, this system keeps 2 cars fully charged, my Rover and my Mitsubishi GTO.
Solar charging due to it's intermittant operation should have the volts set to 14.4V as the charging is of a more cyclic nature as opposed to trickle charging which is continious and should be set to 13.8 Volts.

Graeme
 
Caravaners use solar panels to keep their liesure batteries topped up but they're not cheap, saying that You can get small ones for about £30 it might be enough I dunno!
Regards Colin
 
I work away from home on a 6 week on/off rotation and use an Optimate for my bike's battery. I have had it for about 2 years now and have not replaced the (3rd) battery since buying the Opti.

'Er indoors starts the car from time to time if I forget to disconnect the flattery.
 
Mmmm. I'm pleased people have had good results with a correctly set up trickle charger. I used to be in charge of around twenty standby generator sets that looked after the railway signalling systems when the mains went down. Originally these had top of the range trickle chargers and they were a disaster! I think my analysis is that they are perfect as long as the battery is perfect; but as soon as the battery develops any defect, no matter how minor, they then destroy it totally in very short order. Pulse chargers cope fine with a less than perfect battery, so overall they are a more reliable solution.

Chris
 
I have spent many years involved with remote telecomunication and main trunk radio stations all of which involved standby generator and battery plant in the advent of mains failure, battery failure was relativly uncommon given the many hundreds of batteries that were in service. Failure of batteries was only ever due to 2 reasons 1: a dodgy one was installed from new, ie a manufacturing defect. 2:the battery had been in service for 10 or more years(usualy more) indeed most of our batteries were were 20 years plus and still had 105 to 110% of rated capacity and were checked fully every year (full discharge and recharge cycles). All of these batteries were on a constant charge.
I have yet to find a domestic battery charger that is properly designed for continous charge application to that end I have always designed and built my own. On the current market there seems to be a range of "intelligent" charges available and some of these may work well but I have not had the time to test them in long term charge situations.
Timed charge cycles on the face of it look a good mid measure however these systems have a problem in that you can end up micro cycling your battery, micro cycling occurs as the battery self discharges (as all flooded cell lead acid batteries do)when the charger is turned off, when the charger is turned back on the battery is replenished. While this is of less effect over a short period ie 12 months or so longer periods of 3 or 4 years this will have an effect on battery life.

Modern lead acid car batteries have only a limited cycle life possibly as low as 5 or 6 deep cycles only unlike batteries of 30 to 40 years ago which would last for many many years and soaked up owner abuse.
I am a cynic when it comes to current automotive battery manufacturing technology, my definiton of latest technology is that the product should be better and last longer, unfortunatly this does not apply to car batteries. What does apply is that technology now means that your car battery that has a warrenty of 24 months will die at 26 months and need replacement. The only advantage of the technology is that the manufacturer gets a gaurenteed income stream from predictable sales of his "high tech" car battery.

end of rant :D

Graeme
 
I thought modern car batteries lasted longer . My friend got over 10 years out of the battery in her 1986 Micra and 9 years out of the battery in a 1998 Escort. These are cars that do about 2000 miles a year so the batteries weren't well looked after
 
There are a range of factors that determine the length of life a battery will last and important factor that should not be left out is the vehicle they are installed in ie the cars drain current when turned off suitability of its charging system and efficiency of its starting system such as the current required to turn the starter motor etc. I also have had some batteries that you can nurse along for many years but in the main I beleive the car itself is a great determiner of longevity of the battery.
Cars that start instantly when you turn the key and have low current starters will last best. This is very important because as lead acids age there internal impeadance or resistance increases which means your battery volts and effectivly the current available drop markedly, cars that start easily are much less affected by this characteristic.
What batteries really hate is great wads of current being taken from them ie cold starts that require extra cranking, high continous loads and deep cycling (going flat from your lights left on etc).
If your loads are minimal you are generally fine.

Graeme
 
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