Trickle chargers??

[andywood]

Hi all

Hadn't used my '2 for a few weeks and had a flat battery when tried to start it today, so had to jump off my company car after pushing it out the garage and up the sloping drive   s:roll: :roll: s:roll:  
Has been touch and go a few times over the winter on starting and reckon that the battery which was new 3yrs ago probably needs some conditioning.

Am thinking on splashing out on a trickle-charger as will no doubt be cheaper than replacing the battery.

Am torn between these two which seem to have collected various accolades between them:
 m http://www.amazon.co.uk/CTEK-XS3600-Bat ... 460&sr=8-1 m
 m http://www.amazon.co.uk/CTEK-XS800-Batt ... _cp_auto_1 m

Anyone got any advice on trickle-chargers or have one of these particular models??

Cheers

Andy

[Tem]

I have the XS3600 myself.

They are basically the same, the only difference being the current output. It takes forever for the 800 to charge an empty battery, but it's perfect for keeping a battery charged, when you're not driving it. 3600 charges a normal sized battery in a day. 800 needs several days, even up to a week to do that.

So just for keeping a charge, 800. If you ever need to charge a drained battery, 3600. I bought the latter, cause the price difference wasn't that much and you never know when you need it..

[alancdavis]

What about those solar chargers ?

[enid_b]

What about those solar chargers ?

they will only work for 3 days a year here alan   s:D s:D

[uktotty]

I use this one on the bike,http://www.accumate.co.uk/it010003.html cheaper if you shop around

[Gif]

Hadn't used my '2 for a few weeks and had a flat battery when tried to start it today

We must be living in a parallel universe   s:lol: :lol: s:lol:  

Exactly the same.  Except I thought I had mine on a trickle charger but there must have been something wrong with it cos the battery was on Shrove Tuesday duty   s:roll: :roll: s:roll:  

I bought a new one from Halfords @ £25 when I was there replacing the battery (Decided it was time to make doubly sure). It's only 750ma so would take ages to charge a battery but then again that's not what it's for so I will stick with it.

[Mike68]

If using a trickle charger you will do the battery more long term harm. A battery needs to be worked, they are similar to a human body, you feed the body with no exercise and it will get unfit and that's what you'll do to a lead acid battery.

If you use a charger to keep it topped up rather than charging from flat then try and work the battery too, if you can get a charger with a discharge function and cycle the battery then it will last so much longer.

[Gif]

Knew that.  What I am going to try is keeping the charger plugged in and connected but power the charger through a digital timer clock so for most of the time it is actually powered down to allow the battery to drain with the clock / alarm etc.  Then for a fixed period, it will power up and charge the battery.

Just need to get the duration right so it's on long enough and often enough to refill but with big enough gaps to allow the drain.

PS normal car batteries are not deep cycle so they don't respond well to being completely flattened.  But I guess you probably know that too   s:) s:)

[Mike68]

The only thing with that is at some point there will be a time where the battery won't turn the engine but will power the alarm etc, that is the point to where a full discharge needs to be so it's not totally dead flat, a charger that will cycle will take it to that point quicker and it's more controlled. I just gave my opinion for the op to consider this type of charger as the battery life will lengthen as it is worked harder rather than trickle to recharge point.

[Tem]

If using a trickle charger you will do the battery more long term harm.

Are you sure?

Assuming we're talking about the lead-acid batteries found in cars, I believe a single discharge does more harm than keeping it charged all the time.

At least my original battery is still just fine after +10 years and it has been on a trickle charger every year for months. Many have failed their batteries during that time simply by discharging them too often.

Then of course there are chargers and Chargers. Ctek's seem to be the best around. I have actually bought several "dead" batteries back to life with mine and they have been fine for years.

 
 m http://en.wikipedia.org/wiki/Lead-acid_battery m

[cclarke99]

Thanks Tem for providing the Wikipedia link - lots of good information. The charge voltages match those which I found to work best when designing uninterruptable power supplies a few years ago and also the need to temperature compensate the charge voltage.
Particularly interesting was

A common misconception is that starting batteries should always be kept on float charge. In reality, this practice will encourage corrosion in the electrodes and result in premature failure. Starting batteries should be kept open circuit but charged regularly (at least once every two weeks) to prevent sulfation.

The cycling type of trickle charger (such as the one Tem recommends) would avoid this, but then you're up against the problem that the total number of charge/discharge cycles the battery can stand is fixed. It can take 1000 complete charge/discharge cycles, or 10,000 cycles where only 10% of the capacity is used, and so on. It depends on how often the charger does the charge cycle

[Tem]

The part you quoted is the reason why you shouldn't use cheap chargers that just keep the battery full. It'll just kill the battery too soon.

you're up against the problem that the total number of charge/discharge cycles the battery can stand is fixed. It can take 1000 complete charge/discharge cycles, or 10,000 cycles where only 10% of the capacity is used, and so on. It depends on how often the charger does the charge cycle

I once tried to measure that. According to CTEK manual, it lets the battery charge fall from 100% to 95% before it recharges it. I only had the measuring instrument for one week and it didn't charge during that time. So I don't know how fast a battery drops down to 95% or how often the CTEK charges it back up, but it didn't seem to be often enough to cause any worry.

My battery was disconnected, so it would be a faster cycle with the battery connected and alarms etc on.



Here's a very rough calculation. Say we have a 40Ah battery and the alarm etc drains 100mA. 95% would be 38Ah and it would take roughly a day to consume that amount. So it more or less causes same stress on a battery as driving the car once a day. And like you said, the more it discharges between charges, the more it will wear. So it would actually be better to use CTEK than drive the car once a day (days drain + start). I really wouldn't worry about using the charger.  s8) s8)

[andywood]

Wow, as always i am pleasantly reminded of the level of enthusiasm, support and knowledge on this forum. Thanks guys for all the informative responses.   s:D s:D  

I don't claim to be a battery geek, but based on all the above and the hassle factor when i turn the key and nothing happens, i think i would rather run the gauntlet of premature battery ageing (if that will really happen vs driving the car through normal daily drive cycles) of hooking up a decent well-regarded trickle-charger to the car.

Fair point by Tem with regards to paying a little extra for the 3600 incase the full/quick re-charge facility is ever needed, will give it some thought.

Group-buy anyone??   s:wink: :wink: s:wink:  

Andy.

[cclarke99]

Thinking about Tem's calculation above, unless the alarm is taking a lot of current, the battery really should not go flat that soon. Assuming that the battery won't start the car with less than 75% of full charge and that the alarm, immobiliser, radio memory, etc takes 10mA then it should take a month before it won't start. In fact it should be longer than that as the battery capacity is more for small currents. I'd hope that the drain was less than 10mA, but for one radio I tried it was a lot more. So if your battery goes flat after a short while then either it's dead and needs replacing or the radio is taking too much current. Just Googling i found a wide range of standby currents quoted ranging from 100mA (that was killing the battery) down to a more sensible 5mA. Has anyone actually measured this?

[t-bone]

Thinking about Tem's calculation above, unless the alarm is taking a lot of current, the battery really should not go flat that soon. Assuming that the battery won't start the car with less than 75% of full charge and that the alarm, immobiliser, radio memory, etc takes 10mA then it should take a month before it won't start. In fact it should be longer than that as the battery capacity is more for small currents. I'd hope that the drain was less than 10mA, but for one radio I tried it was a lot more. So if your battery goes flat after a short while then either it's dead and needs replacing or the radio is taking too much current. Just Googling i found a wide range of standby currents quoted ranging from 100mA (that was killing the battery) down to a more sensible 5mA. Has anyone actually measured this?

No have not measured but in my experience 4 weeks is all you get out of an OEM battery if left undriven. I think the immobilizer, clock, and radio presets pull more then you think.  I store my car from November to late February-early March I have a battery tender which works quite well. it will complete charge my chevy suburban battery in two days will fill up the spyder's in half that time. The great thing about it is goes into a homeostasis mode where it holds the battery at a perfect charge indefinitely I disconnect the terminals, hook up the charger with he battery in the car and its good to go in spring. Not sure the company makes 220v units but here is the website
 m http://www.batterytender.com/ m

[cclarke99]

Not wanting to get into geek mode too early in the day, but I have found that the supercapacitors used in some ICE power amps need balancing resistors which can take 100mA in standby mode. As these are wired direct to the battery they would be a real killer.

[Tem]

Just Googling i found a wide range of standby currents quoted ranging from 100mA (that was killing the battery) down to a more sensible 5mA. Has anyone actually measured this?

I measured mine before buying the PC545, I'll see if I still have the data around..

It wasn't that far from 100mA though. IIRC, it was less, but way above 50mA. 5mA is crazy low, must be on some older cars, where the ignition basically cuts all power? Like T said, we have some stuff, which always consumes some power. Immobilizer, remote key receiver, alarm, stereos, clock, even the different ecu's have a power consuming memory. Alarms are generally the biggest drain, cause they keep monitoring sensors all the time and charging the siren battery.

But I'll see if I can find the numbers.  s8) s8)

[Mike68]

If using a trickle charger you will do the battery more long term harm.

Are you sure?

Very sure, a while ago I worked with many different battery banks and batteries, lead acids and NiCads the largest bank was a 36v bank with a continuous discharge for a 5 hour test was in the region of 1200 amps. I worked on various UPS systems and batteries. although most of the individual battery knowledge has gone the underlying understanding has not.

[Tem]

Very sure, a while ago I worked with many different battery banks and batteries, lead acids and NiCads the largest bank was a 36v bank with a continuous discharge for a 5 hour test was in the region of 1200 amps. I worked on various UPS systems and batteries. although most of the individual battery knowledge has gone the underlying understanding has not.

I'm not sure I fully understand, could you tell more? If we think about the three scenarios below, which is best/worse and why?

1) Car is parked for two weeks. During that time the battery drains so much that the car doesn't start. You'll have to charge the almost fully drained battery once before driving it.

2) Car is parked for two weeks and being charged by CTEK. It lets the charge fall down to 95%, which happens in a day and then charges the battery back up.

3) Car is parked for two weeks and being started daily to charge the battery. The charge falls down to 95% and then the start drains a bit more. Battery is charged by the alternator while idling.

Why would #2 do more harm than the others?

Then there's of course #4, which is a bit annoying, at least to me.  s:? :? s:?  

4) Car is parked for two weeks and the battery is disconnected. The battery stays fully charged, but you lose all settings from stereo system, alarm and gauges. I have a PFC, so the ECU doesn't lose the values it learns, like the stock ECU would do.

[Slacey]

I can't add to the technical stuff, but I've got a C-Tek on the TVR and I'd highly recommend it, good unit.

[Anonymous]

Hi all,

I design power supplies for Jaguar Land Rover, so I hope I can offer something to this discussion.

If your battery is 3 years old and has become flat enough to stop you from cranking your car, the chances are the battery has some level of sulphation on the lead plates and will never be as good as new, no matter what charger you use.  In testing, we find that float charging a battery won't cause damage if you plan to store the car for more than a week.  It's pretty pointless float charging if you use the car regularly however, because as someone pointed out previously lead acid batteries do prefer a bit of mild cycling.  Very long term float charging can even introduce a problem known as stratification, where the acid forms discrete layers in the battery (this is displayed as a high resting voltage but dies under heavy load).  In this case, it is a good idea to disconnect your battery and charge it for an hour or so on a weekly basis.

Manufacturers nowadays attempt to reduce the shutdown current (known as quiescent current) to enable customers to be able to start their cars after 31 days of inactivity, but with various degrees of success over the past 10 years.  I suppose I should measure my Roadster and post the results on here, but I've only had it a couple of weeks...

Some of the premium brands are now using more advanced lead acid batteries known as AGM that can be cycled more deeply, but these are 3 times as expensive as normal lead acid.

So, after boring you with all this (and myself to be honest), I would recommend:
1. New battery if it's old and been flattened
2. Float charger if you plan to store the car without using it more than weekly
3. Avoid repeated short journeys with lots of electrical loads (lights, blowers)
4. If you regularly get a flat battery even though you use the car at least weekly, check for problem aftermarket installations, e.g. ICE, alarm, tracker etc.

Hope that helps guys.  Now I'll go and corner someone at a party and drone at them all night...   s:P s:P

[Mike68]

Very sure, a while ago I worked with many different battery banks and batteries, lead acids and NiCads the largest bank was a 36v bank with a continuous discharge for a 5 hour test was in the region of 1200 amps. I worked on various UPS systems and batteries. although most of the individual battery knowledge has gone the underlying understanding has not.

I'm not sure I fully understand, could you tell more? If we think about the three scenarios below, which is best/worse and why?

quote]

Sorry, can't right now, am recovering from surgery and cannot think straight enough to give reasonable answers. The whole charge discharge thing is based around depth of discharge which for lead acids is about 82% of it's standing voltage. I don't think a drop to 11.6v is deep enough although it is about right to keep the battery sweet, also better than being kept on float charge.