Will a 7 stage 10amp charger work with 120AH AGM battery

Submitted: Saturday, Feb 08, 2020 at 11:47
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Hi

Went to Super Cheap today as they have a 7 Stage 10 amp charger on special. The salesman told me I would need the 15 amp charger to charge my 120AH battery, think he might just be trying to sell me a dearer unit. Do we have any experts that can advise me if this would be correct?

https://www.supercheapauto.com.au/p/sca ... 44706.html

Myles
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Reply By: Member - Core420 - Saturday, Feb 08, 2020 at 11:59

Saturday, Feb 08, 2020 at 11:59
I use a 5 amp charger on my 100 amp battery without problems. It only takes longer.
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Reply By: Batt's - Saturday, Feb 08, 2020 at 12:16

Saturday, Feb 08, 2020 at 12:16
I'm no expert but I would say he is correct the minimum recommendations I have read is to have 10amps of charge per 100ah. The bigger the charger the faster it will recharge the battery which is good for short trips and if you run the battery down low you can get the power back into it faster which is better for it. That's the basics you can get into the technical reasons why but that bores me. Also they say a 100ah battery will take approx 30amps of power so you are limmiting it with a 10 amp charger bigger is better. In my 4wd I have a 40amp charger looking after 2 x 105ah batteries it works well I don't have a 240v charger I have no need for one.

I tried your link came up error is it a 12v car charger or house 240v
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Follow Up By: mynance - Saturday, Feb 08, 2020 at 12:25

Saturday, Feb 08, 2020 at 12:25
240 volt want it for back up as I have a Ctek DC - DC charger hooked up while driving it works well, thought I might get the 240 volt to keep it charged when we are not mobile. The battery only runs my Engel.

Thanks
Myles
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Follow Up By: Frank P (NSW) - Saturday, Feb 08, 2020 at 14:06

Saturday, Feb 08, 2020 at 14:06
"Also they say a 100ah battery will take approx 30amps of power so you are limmiting it with a 10 amp charger bigger is better."

I'm not sure that bigger is better.

It is true that a 30 amp charger will charge a given battery faster than a 10 amp one, but for long life the recommended charging rate for most deep cycle AGM's is about 10% of C20 capacity. So for a 120Ah AGM deep cycle battery, about 12 amps. It's not precise - either 10 or 15 would do.



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Follow Up By: Batt's - Sunday, Feb 09, 2020 at 12:42

Sunday, Feb 09, 2020 at 12:42
From what I have read an understood over the past few yrs I was under the impression agm's when charged in the vehicle off 12v like the power and should be charged up faster but are you saying it's the opposite of that a slow charge is better or is that mainly related to 240v charging when the battery is not in use. My batteries are nearly 5yrs old and are fine only ever been charged via a redarc BCDC40amp and from a fixed 170w solar panel never been put on a 240v charger for conditioning.
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Reply By: Bushranger1 - Saturday, Feb 08, 2020 at 12:23

Saturday, Feb 08, 2020 at 12:23
G'day Myles,
I have 3 different chargers I use & sometimes use the 2 amp smart charger on 1 of my 120AH batteries when the others are used elswhere. Fully charges it but just takes longer.
For longevity of batteries best to charge at no more than 10% of battery capacity. So thats 12 amps for your 120AH.
I use a 16amp when using Gennie so its quicker. Bit over the 10% rule but battery is still fine after years of use.

Cheers
Stu.
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Reply By: Ron N - Saturday, Feb 08, 2020 at 12:52

Saturday, Feb 08, 2020 at 12:52
Mynance - You're spot on with your perception about the sales "pump up". A 7 stage 10 amp charger is quite suitable for your 120AH battery.

I use a simple old 4 amp taper charger mostly, I'm never in a hurry to charge batteries - charging lead-acid batteries fast is not an ideal way to treat them, due to the potential for gassing, and increased battery temperature.

Correct charging voltage is more important than high amperage charge rate.

Pulsing chargers are most effective at keeping lead acid batteries in good condition.
I use an Infinitum Battery Desulphator when charging, it greatly assists in combatting battery sulphation and short life.

Cheers, Ron.
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Follow Up By: Frank P (NSW) - Saturday, Feb 08, 2020 at 14:12

Saturday, Feb 08, 2020 at 14:12
"I use an Infinitum Battery Desulphator when charging, it greatly assists in combatting battery sulphation and short life."

Ron, is that a high voltage desulphation cycle, like 15+ volts?

That would kill most deep cycle AGM batteries - it killed one of mine, confirmed by the battery manufacturer (Exide).
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Follow Up By: Ron N - Saturday, Feb 08, 2020 at 15:12

Saturday, Feb 08, 2020 at 15:12
Frank, as far as I'm aware, the Infinitum Desulphator does not increase the charging voltage. It operates by pulsing the signal frequency.
I can find nothing that says the Desulphator produces additional voltage. From the manufacturers website ...

"The Infinitum Desulfator Battery Life Optimizer prevents sulfation on batteries and removes the existing lead sulfate crystals, ensuring a battery with maximum lifespan and optimum performance.

Infinitum Desulfators generates Amplitude Modulated Pulses (AMP) at the resonant frequency of the crystals to shatter the covalent bonds that hold it together.
This allows the lead sulfate to be reconverted once the battery is charged.
A battery free from lead sulfate crystals will have its lifespan stretched to its maximum".

These little devices work, and are effective, I have proved it to myself by recovering at least 10 sulphated batteries over several years - and these batteries went on to provide an additional 2 to 4 years of working life.
I'm talking mostly automotive batteries that I use in utes, forklifts, tractors, and other industrial items of equipment - but I do have one AGM battery that I have also recovered satisfactorily.

This AGM was bought at an auction with a pile of others, that were obviously deemed dead by the corporate seller, but I have no idea of this particular batterys history.
It's still performing well, 12 mths later after being desulphated. Voltage was around 12V when I first tested it.
I don't usually try to recover batteries that are showing less than 12V initially, these are usually unrecoverable.

The U.S. military utilises these pulsing desulphators to keep much of their idle equipment batteries in good order.

Cheers, Ron.
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Follow Up By: RMD - Saturday, Feb 08, 2020 at 15:53

Saturday, Feb 08, 2020 at 15:53
Ron
That pulsing and sulphate removal sounds like Sonic sound waves on Kidney stones. Shatters them too it does.
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Follow Up By: Allan B (Sunshine Coast) - Saturday, Feb 08, 2020 at 16:31

Saturday, Feb 08, 2020 at 16:31
.
Desulphation devices do employ higher than charging-voltages, usually above 20v, but delivered in brief-duration pulses of high frequency, so you won't see it on a meter. The frequency in the Mhz range is chosen as a resonant to oscillate the lead sulphur crystals and progressively destruct them. The voltage is chosen to produce the required high current, and the pulse width is chosen to deliver a high pulse current but limit the average current to a low value. Generally, the current is delivered by the collapsing field of an inductance. The battery must be connected to a regular charging source during the desulphation procedure to maintain cell voltage. The desulphation pulse has no significant effect upon the connected charger.

They have been demonstrated to be effective but not in all sulphation cases. If the battery has been brought to a severe stage of sulphation, recovery is impossible by this technique, or any other for that matter. Flooded lead-acid cells seem to benefit more from the device.
Best results are obtained by employing the desulphator every few months of battery use.
As with most things, some desulphators are designed and built well and some are not. Price may be a guide.

Cheers
Allan

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Reply By: OzzieCruiser - Saturday, Feb 08, 2020 at 14:32

Saturday, Feb 08, 2020 at 14:32
A higher amp charger will get a battery up quicker but for longevity low and slow is best. Also remember a battery only takes what charge it needs - if it only needs 2amps it will only take that even if a total of 20amps is available.

I have had a supercheap 12 amp smart charger for 15 years and it works fine.

Also dont post links direct to the site as they do not work - yours doesn't.

In the menu box there is a post link option - use that and all would be good

LIKE THIS
AnswerID: 629958

Follow Up By: Peter_n_Margaret - Saturday, Feb 08, 2020 at 15:01

Saturday, Feb 08, 2020 at 15:01
The original link works fine for me. :)
Cheers,
Peter
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Follow Up By: Allan B (Sunshine Coast) - Saturday, Feb 08, 2020 at 16:37

Saturday, Feb 08, 2020 at 16:37
.
Well yes Peter, it would.
Cheers
Allan

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Reply By: Allan B (Sunshine Coast) - Saturday, Feb 08, 2020 at 14:34

Saturday, Feb 08, 2020 at 14:34
.
Hi Myles,

Yeah, the salesman is 'mistaken'. A 10A charger will adequately charge your 120Ah battery.
If your battery is discharged to its lowest safe level (80% SOC) then it would take maybe 4 hours to bring it up to full charge. But as you are using it solely as a maintenance charger at home then this should be fine.

A reservation I would have about this charger is that although it is promoted to be suitable for a variety of batteries, "GEL, Lead Acid, AGM & MF Calcium", good practice requires each of these to have a different voltage for the finishing value. This charger has no adjustment provided for these voltages. "One size fits all" is old-style and not good. Do not be fooled by statements such as "Charger automatically senses and adjusts to battery type". Not possible! And do not be impressed by expressions of the number of "Charging Stages". There are only 5 "Real" stages possible at most. Any additional quoted "steps" would be "sensing" only, not charging stages.
There was a problem with your Supercheap link. Here is another link.

Jaycar on the other hand offer a well-made 10A charger that does have settings for these different battery types. Jaycar 10A charger. Although it costs a little more at $139, I would consider it to be much better value.

There is also the "Kickass" (Australian Direct) at $109 but it also has no provision to adjust for differing battery types.

EDIT:
Perhaps I should expand on the "battery types end voltages". These are only small differences and are only of consequence if the battery is going to be left on 'float' for an extended time. If the charger is only used to bring the battery up to full charge, then a basic charger with a non-adjustable 'end voltage' is adequate. Most are set to suit flooded calls.



Cheers
Allan

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Reply By: Bushranger1 - Saturday, Feb 08, 2020 at 15:19

Saturday, Feb 08, 2020 at 15:19
One other thing Myles.
One of my chargers (jaycar brand) has a setting for 6 or 12 amps. If the outside temp is 30C or over the thermal overload cuts in on the 12 amp setting. It does have a fan but it just can't get rid of the heat.
Nothing wrong with Jaycar gear as I have many items purchased there just wanted to warn you about that.
My Oz Charge will work at 16amps even on a 40c day. Something to ask about with the charger you purchase.

Cheers
Stu
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Follow Up By: RMD - Saturday, Feb 08, 2020 at 15:49

Saturday, Feb 08, 2020 at 15:49
I wouldn't expect any salesperson to know the temps and charge rates and thermal issues, Way beyond their understanding, good you are aware of it but they won't have a clue.
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Follow Up By: Allan B (Sunshine Coast) - Saturday, Feb 08, 2020 at 16:00

Saturday, Feb 08, 2020 at 16:00
.
RMD,
I could agree, in the general case. But a Jaycar salesperson is more likely able to provide intelligent responses to product queries than in most other cases.
Cheers
Allan

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Follow Up By: Bushranger1 - Saturday, Feb 08, 2020 at 16:18

Saturday, Feb 08, 2020 at 16:18
Guys,
Bought the Jaycar charger first & of course did not ask the question because high temp charging performance didn't cross my mind.
Yep the people at Jaycar are pretty knowledgebase thats why I like to shop there.
Bought the Ozcharge from a battery supplier & told him I needed to charge in warmer weather so he suggested the Ozcharge unit from the few brands they sold. Still use the Jaycar as I have quite a few batteries to charge so switch it to 6amps if its over 30 deg C.

Cheers
Stu
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Follow Up By: Allan B (Sunshine Coast) - Saturday, Feb 08, 2020 at 16:33

Saturday, Feb 08, 2020 at 16:33
.
I don't think it would have crossed my mind either Stu. lol

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Allan

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Reply By: Zippo - Saturday, Feb 08, 2020 at 16:27

Saturday, Feb 08, 2020 at 16:27
As others have indicated, it will be fine - and perfectly adequate unless you are in a gut-busting rush to replenish the battery.

Basically an up-sell attempt. Their 15A charger is currently twice the sale price of the 10A (both are SCA "house brand"), so their profit would be way better on the 15A unit. "Just saying ...".
AnswerID: 629963

Reply By: Gbc.. - Sunday, Feb 09, 2020 at 08:01

Sunday, Feb 09, 2020 at 08:01
For AGM charging I am reading more and more that .2C is the preferred current. For a 120aH battery that equates to 24a charging. I would have no issues using either charger, but would buy the best I could afford every time.
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Follow Up By: Zippo - Sunday, Feb 09, 2020 at 13:49

Sunday, Feb 09, 2020 at 13:49
I'd say maximum rather than "preferred". Many recommend 10%, with a 20% max. I've yet to see any manufacturer say preferred, or even use that term.
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Follow Up By: Gbc.. - Sunday, Feb 09, 2020 at 15:23

Sunday, Feb 09, 2020 at 15:23
C rate term? Is there any other?

Some light reading for the OP. Skip straight to the recharging sections.

Low and slow is definitely the realm of archaic flooded lead acid batteries only. AGM ‘preferred’ rate is double.

http://www.sunxtender.com/pdfs/Sun_Xtender_Battery_Technical_Manual.pdf

https://www.trojanbattery.com/pdf/TrojanBattery_UsersGuide.pdf

http://support.rollsbattery.com/support/solutions/articles/4345-agm-charging

Note this is for batteries which are actually deep cycled down to 50 odd percent. Any sized charger will suffice to keep a bank topped up.
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Follow Up By: Zippo - Sunday, Feb 09, 2020 at 16:29

Sunday, Feb 09, 2020 at 16:29
Gbc, interesting that Trojan in one place (p18) say recommended, then in the table below it (p19) they say MAXIMUM. Two bob each way? Or simply that they encourage FAST recovery after deep (50%) discharge so they RECOMMEND the MAXIMUM rate?

Sunxtender - "the heart of your solar system" - also have AGM's that are reputedly (p20) designed to accept 5C rates. That doesn't align well with the mainstream AGM's in popular vehicle use.

Let's just agree that everyone should check the manufacturer's charging specs/limits on the batteries they use or are contemplating using. I know I do, and my current 100Ah AGM selections both say 20A max, so I use a BCDC1220 as my recharge device.
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Reply By: Member - Bigfish - Sunday, Feb 09, 2020 at 09:16

Sunday, Feb 09, 2020 at 09:16
First up I wouldn't buy a supercrap charger. Why? Because they are cheap knock off models from china and having bought other electronic stuff from this mob I have learnt my lesson. 10 amp will do the job well. If your battery is not a top quality like Ritar, Powersonic , Fullriver etc. the your battery is probably closer to 100amp hr than 120 amp hr. 10% is a generally accepted figure for longevity. Save a few more dollars and get a quality charger that you will look after and use for many years.. Rmember...the poor man pays twice. Good luck.
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Reply By: HKB Electronics - Sunday, Feb 09, 2020 at 10:14

Sunday, Feb 09, 2020 at 10:14
I'll just add most chargers are built to a price, this generally means when the battery is low and charger is working at 100% output to bring it up to fully charged it will be running hot.

Heat is not good, it stresses internal components, most failures I have encountered in switch mode power supplies over a long working career have been caused by heat stress, ie dried out electrolytic capacitors, dried out heat sinking grease causing switching transistors/IC's to fail.

A small say 5A will charge a 150Ah ok but will take around 18 hours to bring it up to 100% SOC from 50% SOC, a 15A charger will take around 5.2 hours. If you are going to be deeply discharging the battery I would be going with a the higher capacity charger to keep run times and heat stress down. If your only keeping it topped up then it doesn't matter.
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Reply By: Peter_n_Margaret - Sunday, Feb 09, 2020 at 13:45

Sunday, Feb 09, 2020 at 13:45
I suggest that it is insufficient to consider charge amps in isolation from voltage.
The charge voltage offered will very often limit the amps accepted by the battery, irrespective of the amps available.
An alternator is a common example.
Despite 100A +/- being available, actual charge rates are typically not excessive because the voltage is relatively low at around 14.4V.
The same battery fed by the same alternator but at 15V would be a whole different story. The charge rate would be very much higher and damage would likely occur quite quickly.
Different battery chemistries are best charged (and floated) at different voltages, so for mine, every battery charger whether it be 240V or solar should have adjustable voltages in order to treat the battery as the manufacturer intended.
After that is achieved, the more amperage available, the faster the battery will be charged, within the limits of the battery size and chemistry.
Cheers
Peter
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Follow Up By: HKB Electronics - Monday, Feb 10, 2020 at 10:11

Monday, Feb 10, 2020 at 10:11
Yes charge voltage needs to be taken into account as does charge state of the battery.

However your statement that an alternator with a 14.4V output can supply more than a relatively low charge rate is incorrect.

If we look at a typical dual battery setup, car has a alternator with an output voltage of around 14.2V, alternator is connected to battery by around 4M of 10mm2 cable, fuses, VSR etc. 100Ah battery discharged to 50% SOC.

Initial connection, terminal voltage rises to approx 13V, initial inrush current 60A in excess of 60A, after 10 minutes with a terminal voltage of 13.2V battery is still be pulling 35A, after 60 minutes at 13.7V it will still be taking over 20A. Higher voltage is only advantageous at high states of charge.

No idea what the same AGM would draw with an initial terminal voltage of 14.4V but it is certainly going to be well higher than the above.

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Follow Up By: Peter_n_Margaret - Monday, Feb 10, 2020 at 10:50

Monday, Feb 10, 2020 at 10:50
OK, but the point is that the battery will control the charge rate to "safe" levels.
Were it otherwise, every crank battery would be killed if the lights were ever left on too long when stopped.
I use a standard AGM as a crank and have done for 9+ years and all is good :)
Cheers,
Peter
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Follow Up By: HKB Electronics - Monday, Feb 10, 2020 at 11:51

Monday, Feb 10, 2020 at 11:51
Generally your cranker will be flooded or specialty AGM batteries like an Optima, or stop start battery etc which can handle large recharge currents. In the US it seems AGM batteries are becoming very popular as crankers with a lot of drivers looking to increase their charge voltage to a suitable level to maintain them which is the opposite to what the car manufacturers are doing.

In your case I assume you don't discharge the battery deeply therefore your charge currents will be kept relatively low due to the battery usually being in a high state of charge so all is good.

Your typical AGM on the other hand if being deeply cycled may not be happy if your dumping large currents into it on a daily basis. If charging from any source that has the ability to supply high recharge currents then the expected current flow needs to be taken into account and recharge currents kept within reasonable levels for the specific battery.

The typical recharge rates often quoted ie 20% of Ah capacity are for a battery being charged by a typical smart charger with a constant current initial stage and then a constant voltage stage when the battery terminal voltage reaches the max allowed voltage. An alternate charge method on the other if you have a high current source might be to initially charge at 50A and tapper the charge rate as they SOC increases, this is what happens in the case of an alternator. There are no hard and fast rules.

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Follow Up By: Peter_n_Margaret - Monday, Feb 10, 2020 at 13:43

Monday, Feb 10, 2020 at 13:43
I have never counted the number of times it has been run down over the last 9 years, but there would be a number. It is simply there and set and forget which is how any electrical system (or any other system) should be.
I reckon batteries (and in particular AGM batteries) are tougher than some give them credit for when it comes to the occasional departure from "ideal" treatment.
Cheers,
Peter
OKA196 motorhome
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Follow Up By: Allan B (Sunshine Coast) - Monday, Feb 10, 2020 at 13:47

Monday, Feb 10, 2020 at 13:47
.
I'm inclined to agree with you Peter...... with one exception....... HEAT.
They don't like heat!
And I recall that yours are not in the engine bay....... nor are mine anymore!
Cheers
Allan

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Reply By: HKB Electronics - Monday, Feb 10, 2020 at 10:15

Monday, Feb 10, 2020 at 10:15
As for the ethics of the salesman, on checking the charger manufacturer recommends:

6A unit for upto a 65Ah battery .

10A for upto a 100Ah battery.

15A for upto a 150Ah battery

So salesman was recommending the correct unit as per the manufacturers literature.
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Reply By: RMD - Monday, Feb 10, 2020 at 15:50

Monday, Feb 10, 2020 at 15:50
mynance
Apart from battery charging, Will a defibrillator work on a salesman? Answer: No it won't, because they don't have a heart.
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