3 stage battery chargers

Submitted: Wednesday, Jan 11, 2006 at 22:18
ThreadID: 29594 Views:5228 Replies:6 FollowUps:10
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G'day all
Want to permanently mount a battery charger in the 4by for the AGM.

Want to be able to grab the 240v lead and just plug into the genny or
240v power source.

Seen the CTEK 7amp for $299, the next size 25amp, is probably
too big.

Any other good value chargers out there which would suit.
Cheers
John
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Reply By: Member - Roachie (SA) - Wednesday, Jan 11, 2006 at 22:41

Wednesday, Jan 11, 2006 at 22:41
www.durst.com.au

Mine is the 15amp jobbie and i have it permanently mounted on the camper trailer.
AnswerID: 147910

Follow Up By: Mike DiD - Wednesday, Jan 11, 2006 at 23:13

Wednesday, Jan 11, 2006 at 23:13
The best value 240volt-in switchmode 3-stage charger is this one for $99.
http://www.jaycar.com.au/productView.asp?ID=MB3612

It will charge at 12 amps (or 6 amps) so it limits the initial current (Stage 1) to 1/4C for batteries larger than 25 amphour.

Since this current is not adjustable over a wide range, it is only advertised as a Two Stage charger - e.g. it will not function as a Three Stage Charger for a 7 amphour battery - it won't overcharge it, it will just exceed the recommended Stage 1 current for it (1.8 amps).

Mike

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FollowupID: 401224

Follow Up By: Member - Ozdyssey (QLD) - Wednesday, Jan 11, 2006 at 23:18

Wednesday, Jan 11, 2006 at 23:18
Mike
Sounds like value
what is 1/4C - one quarter _?

So if I have an 110amp AGM at 50% what will it do.

John
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FollowupID: 401225

Follow Up By: Mike DiD - Wednesday, Jan 11, 2006 at 23:23

Wednesday, Jan 11, 2006 at 23:23
C is the Battery Capacity in AmpHours - for a 110amphr, Stage 1 should be limited to less than 27 amps for maximum battery life - so 12 amps is fine.

Mike
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FollowupID: 401227

Follow Up By: Member - Ozdyssey (QLD) - Wednesday, Jan 11, 2006 at 23:28

Wednesday, Jan 11, 2006 at 23:28
gotcha
so it should do about the same job as the CTEK . it's just bigger.
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FollowupID: 401229

Follow Up By: Mike DiD - Thursday, Jan 12, 2006 at 08:24

Thursday, Jan 12, 2006 at 08:24
The cost of high-current switchmode power supplies has come down significantly recently, as well as the computer control to do Three Stage Charging. The Jaycar is a realistic price for a 12 amp charger.

The other Three Stage Charger manufacturers are still counting on the mystery around Three Stage Charging to charge unjustifiable prices.

All that a Three Stage Charger needs to do is to provide a constant Absorption voltage (Stage 2) while limiting to the Bulk current (Satge 1). When the current drops to a preset level it needs to change to the lower Float Voltage (Stage 3).

If you want to charge everything from 3 amphour to 300 amphour batteries, then you will need something with more complex current controls. If you want to charge Calcium-Calcium Lead-Acid Batteries, then you will need something with more complex Voltage Controls.

If you want to charge Low-Maintenence or AGM batteries of the size used for cars or 4WDs, then the Jaycar will do all you need.

Mike
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FollowupID: 401265

Follow Up By: Member - Ozdyssey (QLD) - Thursday, Jan 12, 2006 at 16:46

Thursday, Jan 12, 2006 at 16:46
Mike
Back to square one. Jaycar have recalled these units.
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FollowupID: 401343

Reply By: Redback - Thursday, Jan 12, 2006 at 07:57

Thursday, Jan 12, 2006 at 07:57
Call me nieve but why a charger so big, i have one those 0.9 of an amp battery fighters for the batteries in my setup as i was told that trickle charging deep cycle and calcium batteries was better than using a charger that has big amps.

Mine seem to work great when i'm near 240 and charges all 3 of my batteries fully over night.

Oh this is only a query, i'm not saying mine is the way to go, it works for me it mighten work for others.

Baz.
AnswerID: 147950

Follow Up By: Mike DiD - Thursday, Jan 12, 2006 at 08:33

Thursday, Jan 12, 2006 at 08:33
If you have a 0.9 amp trickle charger then overnight it will only put in 9 amp hours - if that's all you've discharged them, fine. These are only designed to keep a battery charged that has virtually no load on it e.g. Burglar Alarm.

Limiting current is certainly important to long battery life - but anything less than 0.25C is fne - for a 100 amphour battery that is 25 amps. This is what Stage 1 is all about.

If you only trickle-charge a battery that is significantly discharged, then it could take many days before it is fully charged This will shorten the battery life due to sulphation - whenever a battery has less than full charge, the Lead/Lead Oxide is converted to Lead Sulphate which will eventually harden and prevent recharging.

IDEALLY, you should complete recharging a battery within a day.

Mike

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FollowupID: 401267

Follow Up By: Redback - Thursday, Jan 12, 2006 at 08:55

Thursday, Jan 12, 2006 at 08:55
OK thanks for that i think with me it's just to keep it topped up as i never really drain our batteries very low i've always kept a charge up to them by solar or running the car for a little while or going for a drive, which is why i got the battery fighter, as a top up device for when at a 240 outlet.

I guess you guys use more power than i do so it's probably better to have a bigger charger.

Baz
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FollowupID: 401271

Reply By: atoyot - Thursday, Jan 12, 2006 at 14:16

Thursday, Jan 12, 2006 at 14:16
Are you planning on mounting the charger in the engine bay, cause if you are, I don't know if there are many chargers that will fit the bill. I've seen some smaller ones that are designed to be mounted in an engine bay, but I don't think the CTEK is. I have a 3.6 and 7 amp CTEK, and they were about the only ones I could find that are made to withstand water splashes etc for outdoor use (IP65 standard). It's definately worth going for at least a 3 stage charger though.

Andrew
AnswerID: 148036

Reply By: Member - Collyn R (WA) - Friday, Jan 13, 2006 at 13:55

Friday, Jan 13, 2006 at 13:55
John

Don't even THINK of permanently charging an AGM battery from anything but a really top grade three-stage battery charger.

AGMs are tolerant of charging voltages and currents generally - but if float charged that charge must be kept to as low as 13.1-13.3 volts (even 13.0 is fine in hot places). Unless left standing for years however it's better to first fully charge them and then store in a cool place. They are fine left like that for 12-24 months.

Float charge them too high - and you'll damage them
Collyn Rivers
AnswerID: 148300

Follow Up By: Member - Ozdyssey (QLD) - Wednesday, Jan 18, 2006 at 18:48

Wednesday, Jan 18, 2006 at 18:48
Thks Collyn,

What about how the AGM in my vehicle is charged when in transit through the Rotronics dual battery system - alternator in the Disco is 80amp I think. Will this bugger it. I do turn it off every 2 weeks or so to let it rest and drain a bit.

Should I just let it charge up after a trip and then switch off the Rotronics til next trip (every 2mths or so).

Also what brand charger would you recommend to mount in the vehicle for extended touring.

BTW: CT book has been very benefical.
Cheers
John
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FollowupID: 402687

Follow Up By: Mike Harding - Wednesday, Jan 18, 2006 at 19:13

Wednesday, Jan 18, 2006 at 19:13
Hi Collyn

Good to see you back again :)

The float charge on my AGM (C&D Tech - UPS12-310) is spec-ed. by the data sheet at 13V5 to 13V8 at 25C? Why do you suggest a lower float?

Mike Harding
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FollowupID: 402697

Reply By: Member - Collyn R (WA) - Thursday, Jan 19, 2006 at 19:54

Thursday, Jan 19, 2006 at 19:54
John

I don't want to be overly dogmatic about this, but I have had a substantial number of reports of AGM failure where the batteries were mounted underbonnet and used in high temps. But next to no failings otherwise.

The common denominator seems to be the high 'float voltages' in a vehicle set-up.

Further, whilst not all AGM battery makers quote the same specs, many recommend 13.2 or so volts at 25 degrees C, and and as low as 12.9-13-volts at 35-40 degrees C.

Do bear in mind that many AGM makers still advise against charging AGMs and conventional lead acid batteries in parallel anyway - early copies of books also advised against it, but I now feel there is no real problem if the starter battery is protected by a Redarc or similar voltage sensitive relay.

On the whole I would prefer to charge the battery fully and simply let it be - if you are using it again within a few months.

As a matter of interest I have set up my new 4.2 litre TD Nissan Patrol with a couple of solar modules on the roof to drive my 60-litre fridge (from a 100 Ah AGM Lifeline battery) via a Plasmatronic PL20 regulator programmed specifically to suit my perceived requirements.

There is also a via a Redarc relay from the alternator.

The Redarc is that company's new low current consumption unit - and I have connected the solenoid via an on/off switch on the dashboard so that I only connect the AGM to the alternator when required (yet having the starter battery protected by the Redarc against excess float charge).
Collyn Rivers

AnswerID: 149673

Reply By: Member - Collyn R (WA) - Thursday, Jan 19, 2006 at 20:03

Thursday, Jan 19, 2006 at 20:03
Mike (Harding)
I certainly would not go against a maker's recommendations. But do note that float voltage is at 25 degrees C and that it's a safe bet there is a lower voltage for higher temps. My main concern would be under-bonnet mounted AGMs where ambients are usually closer to 50 degrees C - and often way over in the tropics.
Collyn Rivers
AnswerID: 149675

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