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Author: Subject: Smart Battery Charger
myke pocock

posted on 22/1/21 at 06:24 PM Reply With Quote
Smart Battery Charger

Please excuse the ignorance but what exactly are smart battery chargers? Can they be left attached to the battery and charging even if it is still connected to the car? I ask as both my MX5 and Locost loose charge and I could do with keeping them topped up without disconnecting the battery.
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steve m

posted on 22/1/21 at 06:43 PM Reply With Quote
I bought a plug in smart charger, years ago from lidl/aldi but have never really used it
in my experience, disconnecting the battery on the vehicle is a much better way of dealing with the problem if its going to be left un used etc for quite a while

A disconnected car battery loses minimal power, unless its dead already !!

I dont like leaving stuff on charge all the time, as i had a serious garage fire a few years ago, 21k worth of damage, as the battery charger had caught light, we could of lost the house, !!!

steve

[Edited on 22/1/21 by steve m]





Thats was probably spelt wrong, or had some grammer, that the "grammer police have to have a moan at




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cliftyhanger

posted on 22/1/21 at 07:15 PM Reply With Quote
Yes, I am no expert, but have an aldi/lidl version, and a noco? i won in a raffle. Both are slow chargers, 1A or so, but seem to sense the battery and turn off when happy.
If I need a fast charge, I have acquired a small forklift charger (or it came from a forklift place) and that balances the cells first, then can charge at 25A if needed. It again senses stuff, and switches off. It also weighs about 10Kg, so a quality bit of kit.

The lidl/aldi one (sorry, cant remember which) has a few programs, and at about 12 seems a decent value bit of kit. Never heard a bad thing about them, but of course only appear for sale once you get one elsewhere.

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02GF74

posted on 22/1/21 at 07:48 PM Reply With Quote
quote:
Originally posted by steve m
disconnecting the battery on the vehicle is a much better way


This.

It was discussed on another forum and consensus was a constant smart charge is a sure way to speed up the demise of a car/motorcycle battery.

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gremlin1234

posted on 22/1/21 at 09:02 PM Reply With Quote
if you connect a smart charger the wrong way round, it will not try to charge the battery in reverse. (this is good) but it also will not start charging a very flat battery.

they will also try and charge at their max rate 'till the battery is nearly full (again this is good)

they will then go into a maintenance mode, monitoring the battery voltage and topping up as required.

some trickle charges charge continuously at at low rate (without voltage cut-off) and as said above gently cook the battery. (absolutely fine if put on for a few days, but doubtful for the whole winter),

in short yes you can charge it in-situ, there are other caveat's though - the negative should go to the chassis. - not the battery terminal - so the cars monitoring system knows its being charged.

edit to add
my lidl charger has a standard charge mode, and a 'winter boost' setting. standard should be fine indefinitely, the boost should only be for a short period else it overcharges/cooks the battery as explained above.

[Edited on 22/1/21 by gremlin1234]

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coyoteboy

posted on 23/1/21 at 04:09 PM Reply With Quote
quote:
Originally posted by 02GF74
quote:
Originally posted by steve m
disconnecting the battery on the vehicle is a much better way


This.

It was discussed on another forum and consensus was a constant smart charge is a sure way to speed up the demise of a car/motorcycle battery.


This is illogical unless your smart charger isn't smart. There are battery backups for telecoms systems kept on charge endlessly without failing.





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peter030371

posted on 23/1/21 at 05:56 PM Reply With Quote
Speak to a battery expert and the thing that damages a car battery the most is periods of no (or very little use) use. A decent smart charger is designed to be left connected during these periods. Some of the cheaper chargers are not smart, just a basic charger with smart added to the name to sell more!

My leisure battery is left connected to a smart charger all the time and maintains it perfectly.

I have a lithium battery in the Striker and that has a decent lithium specific charger all the time.

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gremlin1234

posted on 23/1/21 at 11:39 PM Reply With Quote
quote:
Originally posted by peter030371
Speak to a battery expert and the thing that damages a car battery the most is periods of no (or very little use) use.

particularly true if there is any parasitic drain, which is one of the reasons disconnecting the battery is generally good idea.

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pigeondave

posted on 24/1/21 at 12:01 PM Reply With Quote
I have the Fury hooked up to an Optimate 6, Its on there all the time. The kill switch is flicked to off so its just doing the battery.
It's hard wired to the little plug which comes with it.

It also comes with clips which i use on other cars in the house from time to time. It does a good job of reviving dead batteries but like others have said they cant be connected to the car. Im talking totally dead batteries here.

When its hooked up for more than 24 hours it does all sorts of pulsing charging so it doesn't bugger the battery. Or at least that's what it says in the manual.

for a lot of these things you can download the manual for free, why not have a look through a few which your thinking about.

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coyoteboy

posted on 25/1/21 at 12:47 PM Reply With Quote
I've spent a lot of time working with, characterising and testing batteries in my current job, though I'm not a battery expert by electrochemical training. And mostly lithium polymer (characterising the cycle capacity fade, self discharge rates, thermal effects, physical expansion with charge level and their interdependencies). They're sensitive little mares. Lead acids are less so, especially flooded lead acids. However all secondary batteries suffer the same types of problems:

1) Self discharge - they have an internal resistance. When leaving them, they go flat on their own.
2) If you leave lead acids to go below a lower voltage threshold (temp dependant), you cause damage to the plates that is not recoverable.
3) IF you over-charge, you cause damage both to the plates and boil off electrolyte.
4) Their "charged" voltage, and capacity, change with temperature, as does the availability of current (internal resistance).

This means you need a charger that is smart enough to maintain voltages with a trickle charge AND compensate for thermal effects on that voltage. If you have a parasitic drain (the car) then that should be maintained happily by an appropriately smart charger. The problem is, many "smart" chargers work by having a few operational regimes, where the final float regime is constant current. This means if you have a larger parasitic drain, it won't account for it, and if you have a smaller battery with no drain, you over-charge it. If the temperature falls to near freezing, your trickle voltage threshold comes down, so some smart chargers detect this as dropping back into full charge regime and dump current into it, when it's least capable of accepting it. And some smart chargers are one-shot action - where they assume you're taking a flat battery and charging it once, not leaving it on charge.

A good quality, known brand charger should account for thermal variation, account for parasitic drain and never cause over or under-charge. Cheap ones *can* be bad to batteries. Either just shutting off at a voltage, or continuously trickling a fixed current, or dropping back into full charge mode if the temp drops. Batteries are expensive, so it's worth getting a good charger.





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Mr Whippy

posted on 26/1/21 at 12:27 PM Reply With Quote
We had an old JCB digger that the electrics was shot with just a wire to the starter and that's it (started it by shorting the terminals in the stater motor!). So to keep it charged we stuck a solar panel on the roof and clipped it onto the battery. We'd check the levels in the battery now and again but that battery lasted over 8 years till we sold it and even in winter that battery was always fully charged.
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coyoteboy

posted on 27/1/21 at 06:09 PM Reply With Quote
I had an old battery powering my greenhouse, charged from a 20W solar array. I forgot to disconnect it when I left the greenhouse for the winter. Came back to a very dry battery!





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Mr Whippy

posted on 27/1/21 at 07:15 PM Reply With Quote
quote:
Originally posted by coyoteboy
I had an old battery powering my greenhouse, charged from a 20W solar array. I forgot to disconnect it when I left the greenhouse for the winter. Came back to a very dry battery!


20w is a lot of power to be pumping into a battery. You can get regulators to trickle charge from a solar panel.

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