25amp ctek charger fro 80ah deep cycle agm battery

Submitted: Wednesday, Jul 03, 2013 at 01:47
ThreadID: 103070 Views:9837 Replies:7 FollowUps:14
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As far as i know rule of thumb for charger amperage is battery capacity ah/5. Too much amps overheats the battery and can damadge it, too litle amps takes ages to charge a battery. But ctek msx25 25 amp charger spec says that it is good for batteries anywhere between 50 to 500 ah. Is this marketing bull or are those chargers really somehow exceptional?
The reason I want to go for 25 amp charger is to charge my 80ah agm battery quicker from yamaha 1kw generator. But isn't 25 amps too much for a battery this size?

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Reply By: Ozhumvee - Wednesday, Jul 03, 2013 at 07:41

Wednesday, Jul 03, 2013 at 07:41
It really depends on the particular battery, check the manufacturers specs re charging rate to be sure.
I use my 25 amp Ctek to charge anything from the 20ah mower battery to the 500ah bank in the motorhome.
AnswerID: 514175

Follow Up By: Notso - Wednesday, Jul 03, 2013 at 08:16

Wednesday, Jul 03, 2013 at 08:16
The MXS 25 has a temperature sensor that will reduce the charging voltage if the temperature of the battery gets too high.
FollowupID: 793081

Follow Up By: Ross M - Wednesday, Jul 03, 2013 at 10:42

Wednesday, Jul 03, 2013 at 10:42
It temp senses ONLY if you fit a sensor onto the battery so it can sense.
Otherwise it won't sense at all, just two charging wires won't.
FollowupID: 793099

Follow Up By: Notso - Wednesday, Jul 03, 2013 at 10:50

Wednesday, Jul 03, 2013 at 10:50
The MXS 25 is equipped with an external temperature sensor. Activated
temperature sensor will be indicated by a lit temperature sensor indicator lamp. The temperature sensor will adjust the voltage to the ambient temperature. Place the temperature sensor in the positive clamp or as close to the battery as possible
FollowupID: 793100

Reply By: olcoolone - Wednesday, Jul 03, 2013 at 08:23

Wednesday, Jul 03, 2013 at 08:23
You will be fine, all automotive batteries can handle more than 25amps whilst charging comfortably.

The Ctek is a very smart battery charger using temp sensing to help determine charge rate.

Your battery is very lucky to be charged by a Ctek...... look at how many are being charged in vehicles with no current limiting or heat sensing of the alternator, they survive.
AnswerID: 514179

Reply By: Member - Frank P (NSW) - Wednesday, Jul 03, 2013 at 09:18

Wednesday, Jul 03, 2013 at 09:18
I was taught the rule of thumb was 10% of the battery's C20 Ah capacity, so who knows?

I don't think it matters much for a crank battery - they're designed to be charged by vehicle alternators which have no current regulation.

I think it is more important for house batteries and hybrids - AGM, gel, semi-sealed wet cell (so-called "maintenance free") etc.. Supercharge says 10 amps for its105Ah Allrounder. Peter's advice is good - check with the battery manufacturer.

It's a pity that charger manufacturers don't make their top-end products fully programmable. Most are switch selectable to control voltage profiles, but always will deliver their max current in the bulk phase, which may not be appropriate. There was one fully programmable device but it is no longer available - the locally made, Australian designed and built Ranox. It got priced out of the market by the big fellas before it could get a foothold. If you ever get the chance to buy a second-hand one, grab it.



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AnswerID: 514184

Reply By: The Bantam - Wednesday, Jul 03, 2013 at 09:40

Wednesday, Jul 03, 2013 at 09:40
Not all deep cycle AGM is specified to handle 25 amps.

One very popular deep cycle AGM in 100AH is specified with a maximum initial charge rate of 20 amps

It is not wise to rely on temperature sensors to limit charge rate.
If the charge is correctly selected or adjusted to suit the charge requirements of the battery Temperature sensors are a great thing...BUT they are not a current limiting device.

Temperature is only one factor in limiting charge rate in AGM batteries, depending on the battery and how it is designed excessive charge rate can also result in.

excessive gas production that overcomes the recombination process resulting in the battery venting and loss of electrolite.

Gas being produced at a faster rate than it can migrate thru the electrolite and glass mat....not sure on the effects of that, but it would influence the above, as recombination occurs in the open space above the plates.

and other less important factors

It is very wise to stay within the maximum initial charge rate specifications of the battery

Most automotive batteries can tolerate the charge being hammered into them at very high rates.....the problem is a lot of the AGM ( particularly deep cycle) being used are not "automotive batteries".

The 25 amp charge is indeed suitable for batteries from 50 to 500 AH.....but not all batteries in that range.

Remember even a good modern 25 amp charger may not deliver 25 amps into a given battery appart from in the very early stages of charge.

And charging a lead acid family battery takes a finite time.

You have to have big battery to get best value from a big charger.

You may find that the 15 amp version will be more appropriate and better value in the situation.

AnswerID: 514187

Follow Up By: Odog - Wednesday, Jul 03, 2013 at 16:39

Wednesday, Jul 03, 2013 at 16:39
I have a rearc dc/dc 1240, under the bonnet, which puts out 40 amp, the second battery is only 65 ah. Massive over kill. But when the camp trailer is hooked up, which has another two batteries in it, another 150ah, charges them in no time at all. My under standing was they are a smart charger, which reduces the charge flow when the battery is full? This set up was done by arb, on a 150 prado. Any thoughts? Cheers Odog
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Follow Up By: olcoolone - Wednesday, Jul 03, 2013 at 21:39

Wednesday, Jul 03, 2013 at 21:39
Odog, not the ideal set up and yes the 1240 is to big for a 65ah battery, the advantage of DC-DC charging apart from the correct charge algorithms it can also act as a current limiter for the battery..... but then again batteries are like babies..... they are very robust and you may get many happy years out of your battery.

The lower the charge to better it is for the battery.

The way ARB should of done it is a BCDC1220/25 for the 65ah battery and them pick up another feed from the starter battery to a second BCDC1225/40 mounted in the camper.

The only thing to worry about them is if you exceed the duty cycle of the alternator if the batteries were extremely low.

The Redarc DC-DC chargers are quite smart but like all other DC-DC chargers; they not smart enough to detect the best charge rate and adjust accordingly for small batteries.

One way around it (sort of) is to go to a conventional lead acid deep cycle battery that can be topped up when needed.

Sealed led acid batteries can take big charge rates but when they have be charge with excessive current or voltage they start to expand and deform and very rarely they may vent...... by this stage damage has been done.
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Follow Up By: The Bantam - Wednesday, Jul 03, 2013 at 22:47

Wednesday, Jul 03, 2013 at 22:47
One reality that all to often people fail to understand is that lead acid batteries naturally reduce the charge rate as the battery fills.

This means that the charge rate will be high in the early stages of charging and will progresivly reduce...in fact if the charger is capable of delivering a good solid charge the charge rate will reduce quite rapidly.

The result is that the final portion to "fully charged" ....."may take some time"

The modern multistage chargers are designed to reduce this as much as possible in an effort to bring the battery to "fully charged" faster.

BUT....."Ya can'a change the laws of physics Jim"....so no matter what charger you used, getting a battery properly and fully charged takes time.

Another reality that is very very often ignored is that there is a wide variety of characteristics in different batteries, and generalisations can be very unreliable.

A battery designed for heavy cyclic use like a "starting lighting ignition" battery, will usually cop a very stiff initial charge rate quite happily...like off the order of 100% of its amp hour capacity.

Batteries designed for long term deep cycle work may have maximum initial charge rates as low as 20% of amp hour capacity...in some cases much lower.

This is regardless of the technology type.

We can only speak accurately and sensibly when we know the properties of the particular battery...and these properties vary considerably.

Back to the original poster...and any body else selecting a charging system or a battery...in particular AGM and similar sealed batteries.

We must know the specified maximum initial charge rate for the specific battery.

There are a lot of people out there spending high $$$ and getting very very poor life out of AGM because they fail to ensure their batteries are charged within their maximum initial charge rate.

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Reply By: edvard p - Thursday, Jul 04, 2013 at 01:57

Thursday, Jul 04, 2013 at 01:57
found this article: www.westmarine.com/webapp/wcs/stores/servlet/WestAdvisorView?langId=-1&storeId=11151&page=Battery-Charging#.UdRF-f5uvbU

it says agm deep cycle batteries can accept current of up to 40% of C in bulk stage. bulk stage is when a battery acceps most current because its voltage is down. bulk stage lasts up until battery is 80% recharged.
AnswerID: 514246

Follow Up By: The Bantam - Thursday, Jul 04, 2013 at 11:23

Thursday, Jul 04, 2013 at 11:23
Again at the risk of sounding like a cracked record.

Generalisations about batteries are most unreliable.

Check the specifications of the particular battery in question.

If we all want to get narky.

I can pull up specifications of 3 different AGM batteries from the same manufacturer that have very different "maximum initial charge rates" specified.

The lowest of the 3 has a "maximum initial charge rate of around 20% of its amp hour capacity, the highest is a cranking battery that has exraordinarily large cranking capacity and a very high "maximum initial charge rate" comparable with top shelf wet cell cranking batteries.

Then if you want to get into discussions about temperature and AGM batteries...some AGM batteries tolerate higher temperatures extraordinarily poorly.
I have seen spec sheets on AGM batteries that the battery is not designed for operation over 45C, and charge rates have to be significantly reduced well below that.

I recently read a paper that confirmed what I had known in general terms for a long time.
This paper examined the influences of various factors on service life of AGM batteries.
It proved and quantified that 3 major factors reduced service life of the batteries in question considerably....even when operated within specification.

1. Higher than optimum charge rates
2. Tempertures higher than 25C
3. Repeated deep discharge

They found that using all 3...within specification...that they could reduce the service life of a battery from a designed and proven 10 years to as little as 60 days.

So....be as optomistic as you like.....but charging any battery in particular AGM above optimum charge rate reduces its life......chargeing an AGM battery above its specified "maximum initial charge rate" will reduce its life CONsiderably.

Look up the specifications for the particular battery.....or even simpler, most AGM and similar sealed batteries have the basic specs printed in the side.

Ignore these specifications at your own cost.

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Follow Up By: Member - Frank P (NSW) - Thursday, Jul 04, 2013 at 12:02

Thursday, Jul 04, 2013 at 12:02
Good post, Bantam.


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Follow Up By: edvard p - Thursday, Jul 04, 2013 at 19:07

Thursday, Jul 04, 2013 at 19:07
currently looking for specs of DEKA Intimidator AGM 8A27M 92Ah.
can't find anything about recharging. sent aquestion on dekas' website 2 days ago, no reply.
FollowupID: 793228

Follow Up By: The Bantam - Thursday, Jul 04, 2013 at 21:12

Thursday, Jul 04, 2013 at 21:12
The deka batteries are in general more like starting lighting ignition batteries, and in general capable of with standing reasonably high charge rates.

if you go to the US home web site...and look for their most excellent document on VLRA batteries ( remember this is a very informative document BUT some content is specific to DEKA batteries) on page 5

you will find this.

"Use the highest initial charge rate available (up to 30% of the 20 hour capacity per hour) while staying within the proper temperature compensated voltage range"

Don't forget the "proper temperature compensated range"

reading this is an example of how it works.....the maximum initial charge rate is one issue.....proper temperature compensated voltage range is another.

When we select or adjust a charger..we consider Maximum initial charge rate......we then compensate charge voltage for temperature.

So if we go to the Intimidator brocure we see that an 8A24M

has a capacity at the 20 hour rate of 79 Amp Hour....thus according to the documents the maximum initial charge rate would be 26.33 amps.....a 25 amp charge would be appropriate as I read the specs.

If however we where considering a Fullriver HGL100-12, a bigger sized batteryhttp://www.fullriver.com/products/admin/upfile/HGL100-12C.pdf

We would see that it has a 100AH capacity at the 20 hour rate and a maximum initial charge rate of 20 amps...a 25 amp charger would be pushing the friendship

If we went to the HGL80-12......a battery of similar capacity to the intimidator above we see that the maximum initial charge rate is 16 amps.

This does not make either battery better or worse.....just different trade offs have been made for a particular goal.

We must deal with the specs of the specific battery in question.

FollowupID: 793254

Follow Up By: Member - graeme W (WA) - Saturday, Jul 06, 2013 at 15:43

Saturday, Jul 06, 2013 at 15:43
Hi Bantum. Just for everyones interest i have two auxillaries one a 65amp valve regulated agm fullriver under the bonnet and the other same type 120 amp under the tray connected with 8b@s cable charged with 280 watts of solar. In full shade however i use a 40amp xantrax charger run by the honda 1kva on eco. Longest time using this was two weeks running 3 to 4 hours everyday depending on need and not letting battery voltage get much below 12.4. Running two fridges one as a freezer {60 litre trailblazer} and the other an 80 litre wacoe fridge.Batteries are 5 years old and still good although i think the charging rate while doing this may have been above recommended limits. Ive also been carefull and not let voltage get to low if possible.The big battery i on its side as well.
cheers Graeme.
FollowupID: 793380

Follow Up By: The Bantam - Saturday, Jul 06, 2013 at 22:12

Saturday, Jul 06, 2013 at 22:12
Graeme, the single most important thing you are doing is not letting the cycle depth get too deep.

One of the biggest misconceptions is that "deep cycle batteries" tolerate a lot of very deep cycles....in general they do not.

The shallower you cycle any lead acid battery the longer it will last.

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Reply By: Lex M - Thursday, Jul 04, 2013 at 14:26

Thursday, Jul 04, 2013 at 14:26
Someone should tell this guy :-

evilbay link.
AnswerID: 514262

Follow Up By: Lex M - Thursday, Jul 04, 2013 at 14:35

Thursday, Jul 04, 2013 at 14:35
Sorry. Wrong thread. Need an edit function.
FollowupID: 793206

Follow Up By: Member - Frank P (NSW) - Thursday, Jul 04, 2013 at 15:48

Thursday, Jul 04, 2013 at 15:48
It has already been reported as an illegal product.

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FollowupID: 793214

Reply By: Ross M13 - Saturday, Jul 13, 2013 at 21:40

Saturday, Jul 13, 2013 at 21:40
I can vouch that icharger is descent thermostatic charger that works in a smarter way. I used it for AGM batteries too and found effective indeed.
AnswerID: 514761

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