Battery chargers

[Rossco]

I just bought repco 8 stage 8 amp one. Should have got one ages ago, works great, very happy with it.

Mines pretty much same scenario as you winnie, can be weeks between a decent drive plus i often work in the shed with the car radio going. Yeah i just leave it on most the time then cranks awsome when your ready to go. The redarc kicks in reasonably early so assume it's keeping that one toped up too.

[Cuppa]

With ctek you have to be careful if buying one intended for a smaller battery bank beause there is a chance it will overcharge the battery if left unattended. I had a ctek 7 amp charger on 300Ah of batteries & this was a problem. It has to do with the how ctek chargers 'check' the battery every 10 days when in float mode. My ctek had a 'Supply Mode'. I got around the problem by montoring the battery until it was full, (ie. dropped into float mode) & then switched the charger to 'Supply mode' which I could leave indefinitely. If buying ctek I'd suggest it is best to stick with the models suited to your battery capacity.

I had a 0.8A smart charger (not a ctek)supposedly intended for 'permanent' connection plugged into a wet motorcycle battery years ago. No mention in the instructions to regularly check & top up the battery fluid. It killed a new battery in less than 12 months, being plugged in whenever the bike as in the garage.

Whichever smart charger you buy, you will still need to check the battery fluid regularly & top up as needed (if a wet battery) or risk it dropping the fluid level below the plates, or even boiling it dry. This can happen with many smart chargers as the battery will bubble & gas when close to full charge, & can do so in float mode. Shouldn't be a problem with a correctly sized ctek though.

Personally if getting a new battery I'd suggest you get an AGM battery which don't suffer the same problem because of their recombination technology. Additionally AGM's have a far lower 'self discharge' rate than wet batteries & if fully charged when you park up can happily be left for a month or more at a time without needing to be on a charger. I had no problems with YellowTop Optima batteries, although there are cheaper AGM's suitable for starting duties.

[dom14]

Getting the batteries out of the engine bay will also help their longevity.

How do you do that?

[dom14]

With ctek you have to be careful if buying one intended for a smaller battery bank beause there is a chance it will overcharge the battery if left unattended. I had a ctek 7 amp charger on 300Ah of batteries & this was a problem. It has to do with the how ctek chargers 'check' the battery every 10 days when in float mode. My ctek had a 'Supply Mode'. I got around the problem by montoring the battery until it was full, (ie. dropped into float mode) & then switched the charger to 'Supply mode' which I could leave indefinitely. If buying ctek I'd suggest it is best to stick with the models suited to your battery capacity.

If it's a Ctek smart charger, it should cut the amps as the battery reaches it's full state of charge.
As much as to almost zero if the battery is "100%" full. If a smart charger overcharges a battery, that defeats the purpose of a smart charger, I reckon.

I had a 0.8A smart charger (not a ctek)supposedly intended for 'permanent' connection plugged into a wet motorcycle battery years ago. No mention in the instructions to regularly check & top up the battery fluid. It killed a new battery in less than 12 months, being plugged in whenever the bike as in the garage.

Ideally it shouldn't, if it's a properly working smart charger.
But, I don't leave them plugged anyway. I reckon it's a waste of electricity(not money. )
I charge the battery once a month with a mains electricity smart charger and a pulse charger.
Appears to be doing a really good job by keeping the battery going lot longer than it normally does.

Whichever smart charger you buy, you will still need to check the battery fluid regularly & top up as needed (if a wet battery) or risk it dropping the fluid level below the plates, or even boiling it dry. This can happen with many smart chargers as the battery will bubble & gas when close to full charge, & can do so in float mode. Shouldn't be a problem with a correctly sized ctek though.

If the smart charger does what it says it does, then ideally it shouldn't push excess current into the battery. But, I haven't tried leaving a smart charger plugged in indefinitely to see how it goes.

Personally if getting a new battery I'd suggest you get an AGM battery which don't suffer the same problem because of their recombination technology. Additionally AGM's have a far lower 'self discharge' rate than wet batteries & if fully charged when you park up can happily be left for a month or more at a time without needing to be on a charger. I had no problems with YellowTop Optima batteries, although there are cheaper AGM's suitable for starting duties.

[Cuppa]

Hi Dom,
I was pretty sure someone would post what you have in reply to what I wrote. It is what I would have expected too, but my experience suggests different.

I have learned over the years that there are smart chargers & smart chargers! Not all work the same. ’Smart’ can mean different things.

All smart chargers will be multi stage chargers, & it is not unusual to see the term smart charger used to just mean multi stage charger. All should when fully charged drop into float mode, generally providing a constant voltage between 13.3v & 13.8v (with a 12v charger) with little to no current

Most will have a voltage threshold below which the charger will switch back into bulk charging mode. Some will drop back into float mode when a voltage threshold is reached. Some will just remain in bulk charging mode for a set period of time. This runs a risk of overcharging.

The 7 amp ctek I had automatically changed from float to bulk every 10 days regardless of battery voltage. This would have been ok if the battery capacity had matched the charger, but as the charger was too small somehow the charger always thought that the batteries needed charge & if left in float mode would have overcharged them. Essentially the charger was ’too smart’.

If the ctek was left connected to my batteries when the vehicle was outside the solar regulator would periodically show a high voltage disconnect error, whilst still logging the battery voltage from the ctek. On occasions this would rise to as much as 16.1v leading to concern about the possibility of thermal runaway & even fire. This was a result of mismatched charger to battery capacity. I can’t recall more specific details, but had correspondence with Ctek at the time & am confident the charger was not faulty. They suggested I test it on just one of the 150ah batteries (instead of the two of them together) & there was no problem. Together 300Ah was a different story. I had expected that a smaller charger would just take longer to charge them, but there is clearly more to it than that.

[nissannewby]

How do you do that?

Buy a ute...

[lhurley]

Snip.... I had expected that a smaller charger would just take longer to charge them, but there is clearly more to it than that.

With my mains charger this is the case. It's a 4amp one can't remember the brand (procharge I think) and it will just keep chugging away until full. It will time out bulk charge mode after 24 hours though. So I learnt after my first camping trip with a new deep cycle battery. The charger also will sit in float indefinitely to maintain charge of a battery. Can find specific model if required.

[Cuppa]

With my mains charger this is the case. It's a 4amp one can't remember the brand (procharge I think) and it will just keep chugging away until full. It will time out bulk charge mode after 24 hours though. So I learnt after my first camping trip with a new deep cycle battery. The charger also will sit in float indefinitely to maintain charge of a battery. Can find specific model if required.

Yes this is similar to how many work, (the time periods my vary) even the Ctek, except it's what the ctek does 'extra' after being in float mode for 10 days which is different.
Some will also continue to put a small current into the battery whilst in float. Depending on battery type & size, over lengthy periods of time,this can reduce battery fluid levels (wet battery), so checking now & again is wise.

[Winnie]

Thanks cuppa, for that spanner in the works. So now I'm really confused.

[the evil twin]

snip... So now I'm really confused.

Excellent, our work here is done.

Perhaps this will help make it worse.
No matter which brand you choose you are looking for a "maintenance" Charger not a "bulk/float" and even in the one brand not all are the same.

For CTEK - look for the M series (with exception of the 0.8 which have been around for yoinks)
XS 0.8 - YES for batteries up to 100 AH (manuf spec) and FWIW I use for a tad more
XS 3.6 - NO
MXS 3.8 - YES for batteries to 130 AH (manuf spec) and FWIW I use up to 200 AH when paralleled
CT 5 - NO
MXS 5.0 - YES for batteries to 160 AH (manuf spec)
etc, etc as size increases

I have maybe 20 odd CTEK 0.8 and some 3.8's in vehicles and field installations.
The field batteries are changed out no earlier than 3 years and test as "98% charge, healthy battery" on SAE testers and find their way into vehicles, boats and campers.
The vehicle batteries mainly Century and Supercharge haven't been changed out yet (nearly 3 years in service) so no hard experience.

Now... I have a MXS 7.0 as my 'home' smart Charger as my 'go to' for reco and bulk/float charging.
I still prefer the 3.8 for maint of the Ute even tho the spec is 225 AH for the 7.0
It is just a gut feel but it seems to do a better job, maybe because the Ute battery capacity is a parallel sum or whatever I don't know.
I only use the 7.0 on my camper which has over 300 AH parallel capacity (3 x 100 and the Brake System battery)

Solar - works well but relies on the battery chemistry and the best combo is large battery small panel and no reg.