Do AGM Batteries need to be trickle charged ?

[henni]

Reading this link on AGM capabilities but don't know "Best Practice" for a battery that sits in an engine with long downtimes (storage, ie. car not driven, generator not started for months etc.)

http://batteryuniversity.com/learn/article/absorbent_glass_mat_agm

My guess is that using a CTEK MUS 4.3 or similar would not damage but would help AGM battery life

https://www.amazon.com/CTEK-56-864-Automatic-Battery-Charger/dp/B006G14FK8

Any different opinions or facts ?

 

[Donald]

Well the Battery Minder people have a charger just for AGM. But thats to get the best possible charge.

 

[JHZR2]

ALL batteries should be trickle charged and kept cool if you want longest life.

As soon as the SOC drops slightly, irreversible sulfation reactions start to occur.

AGMs have lower self discharge, but it doesnt mean that you need not trickle charge.

In the end, its all abouthow long you want your battery to last, and if youre satisfied with life and failure modes for batteries you have.

Modern, fancier and more electric cars also have more standby parasitic loads, making trickle charging even more prudent.

 

[440Magnum]

For long-term battery maintenance, I'd recommend something smarter than an old-style maintainer. I like this thing, because it's got 7 charging/maintaining stages. Most of the time, after its got the battery charged initially, it does nothing. But periodically it will either trickle charge, or apply a small load for a while then recharge to "exercise" the battery and help prevent sulphation. Note that it has presets for flooded, AGM, and gel batteries, so it applies the correct profile to each. When I first got mine, it revived a lawn tractor battery that wouldn't hold a charge for a week anymore. Put it on the maintainer for about 2 weeks, and then the battery worked without being recharged for another 1-1/2 years.

https://www.amazon.com/SOLAR-PL2320-Pro-Logix-Battery-Charger/dp/B007P7ABE6/ref=sr_1_8?s=automotive&ie=UTF8&qid=1483723129&sr=1-8&refinements=p_4%3AClore%2BAutomotive&th=1

 

[SHOZ]

I wouldn't bother unless there is a draw on them. I leave mine in the car and boost them once a month. If disconnected then once every 6 months should be good.

 

[Kestas]

Mercedes recommends trickle charging batteries every 3 months during storage.

 

[SHOZ]

If they are connected then there is a constant draw on them. Usually under 50 mA though.

 

[barryh]

My experience with an AGM on a motor cycle is that they don't need to be trickle charged.

I'm very keen on looking after batteries and keeping them at full charge but I've learnt that if I leave the bike unused for a couple of weeks and then put the charger on it then I see the charge current fall to zero in a matter of seconds. That tells me I was just being anal and it didn't really need charging. If was leaving an AGM for months then I would charge it occasionally but still wouldn't use a permanent trickle charger. They don't need it and if you get the float charge voltage wrong then you could do more harm than good.

The act of charging a battery is a diagnostic process. As described above if the battery reaches full charge quickly that tells you one thing and in a similar way charging an old wet cell at the ends of it's life tells you that it's loosing a lot of charge while standing and it's time to replace it. For me that's more worthwhile than permanent trickle charging.

Instead of worrying about trickle charging I prefer to worry about giving the battery the correct charge voltage in the first place. So many motorcyclist's splash out a premium price on the most expensive brand of AGM and then omit to ensure that the bikes charging system is charging it an optimum voltage which will be higher than for a wet cell. If the battery is truly fully charged at the end of each use then it's going to last longer in storage.

I'm sure if you get the voltage right trickle charging an AGM will do no harm but for me, generically advising that trickle charging is OK would be wrong.

 

[JHZR2]

Id suspect that a motorcycle has a substantially lower parasitic draw when off, compared to a modern car.

 

[901Memphis]

Yes a good smart charger/maintainer will make the battery last much longer, but i do not like that term "trickle" charger that charges continuously at the self discharge rate which is very low on agm.

You want something that monitors the voltage with a computer and only charges it when the voltage goes below the set float voltage threshold. The Ctek is one of the best on the market for this and there are a few other good options including Pro Logix, Noco, and Deltran/Battery Tender

 

[barryh]

Originally Posted By: JHZR2
Id suspect that a motorcycle has a substantially lower parasitic draw when off, compared to a modern car.


Yes as low as it gets - zero.

Once you start to factor in parasitic current then of course it's going to need charging at some point. I charge my car every week but that's partly another story about modern ECU controlled alternators that deliberately don't fully charge the battery in order to save fuel.

 

[wrcsixeight]

Some AGM batteries, do not really have the low self discharge rate quality that all AGMS seem to have as attributes. The most popular AGM sold in Flaps and relabelled is the Deka intimidator. Its self discharge is not much better than a flooded, and neither are the CCA figures, but it is sealed and should not offgass and corrode battery terminals. Its claims to higher cycle-ability and lifespan are highly suspect, and in comparison to higher$$ AGMS does not stack up in cycles, CCA, or self discharge.

AGM has become a marketing term as much or more than an actual design term, as the general public knows they cost more, and attribute 'super battery' status to them.

The battery manufacturer listed float voltage, which should be temperature corrected, varies 0.6v among different AGM manufacturers. So super battery maintainer brand X, could easily miss the mark.

If I am using my DC power supply set at 13.2v in the intent of keeping my AGM battery fully charged while I power DC loads, if I goose the voltage to 14.4v, the amperage it accepts indicates that somehow the battery was being discharged while being kept at a voltage higher than its fully charged resting voltage.

The break even point on my AGM in mild temps is 13.6v, which happens to be the recommended float voltage by Northstar. If I hold it at 13.6v while powering DC loads and goose voltage to 14.7v, amps quickly taper back to near zero. If I hold it at 13.2v while powering DC loads and goose it to 14.7v, amps go as high as 1.1, and then slowly start tapering toward Zero and might take a half hour more more to taper back to near zero, indicating the battery was being 'trickled' but still slowly discharging.

This changes with battery temperature too. At 54f battery temperature I raise float voltage to 13.8v or the goosing to 14.7v reveals the battery was discharging.

Not sure why this is, only that it occurs and is repeatable, and All I have to do is twist a dial to compensate, but someone with a bells and whistles 23 stage charger with extra special marketing simply gets to put faith in the marketing material and stick their head in the sand.

Measuring tools and reality be Danged.

So a maintenance charger would Ideally have a battery temperature sensor And a user selectable float voltage for whatever brand of AGM they are trying to maintain at 100% full charge.

But this product would never sell well to the masses, as user selectable settings and 'fully automatic' are not one and the same in this day and age of automatic everything.

 

[barryh]

Like I said above it's not as simple as generically saying it's OK to trickle charge AGM batteries. There is a simple answer and that is do what the battery manufacturer recommends as regards float voltage.


I was guilty of being generic myself when I said I had an AGM battery in my motorcycle. In fact it's a GEL/AGM hybrid but I don't usually mention that as it causes confusion and I get told by "experts" that such a thing doesn't exist. They do and they have a remarkably low self discharge rate. The manufacturers data sheet is quite detailed and tells me what voltage to charge it at and what temperature compensation to apply.