battery chargers

Submitted: Monday, Jan 30, 2006 at 13:11
ThreadID: 30240 Views:1964 Replies:5 FollowUps:6
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would anyone know about a 3 stage charger called ' power saver' brand

have not heard of this brand. On e-bay $210.00 (10)amp are they any

good . My system is 2 agm batt (90) amp start (100) amp house. I

want to keep them100% charged so i can get the best usage possible

yours lewjack.

p.s

only other form of charging is by car altinator

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Reply By: Member - Collyn R (WA) - Monday, Jan 30, 2006 at 14:03

Monday, Jan 30, 2006 at 14:03
Need to be very careful if permanently charging AGM batteries. Their internal leakage is ultra-low. Most need a much lower float voltage than other types of battery. This is rarely provided for in bargain price chargers.

If unused for a length of time, AGM actually are best left fully charged - and then recharged only every six months - unless you are 100% certain re the charger.

My own recommendation is the newish Redarc three-stage charger. Well-made, locally made and affordable. Has excellent AGM setting.
Trust this helps
Collyn Rivers
AnswerID: 151788

Follow Up By: Member - Ozdyssey (QLD) - Tuesday, Jan 31, 2006 at 12:31

Tuesday, Jan 31, 2006 at 12:31
Hi Collyn

I phoned Redarc for info on their charger and it is a 12v 5amp charger. Is this big enough to service 100amphr+ batts?

Also would you recommend AGM's or GEL's for day to day running of a 50lt fridge in the vehicle for extended touring.

Cheers
John

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Reply By: 4145derek - Monday, Jan 30, 2006 at 18:24

Monday, Jan 30, 2006 at 18:24
Hi Lewjack

Always best to buy a good charger of at least 15 amp rating.

Regards Derek
AnswerID: 151868

Follow Up By: bouncer - Monday, Jan 30, 2006 at 22:32

Monday, Jan 30, 2006 at 22:32
I just received one of Dereks 15amp chargers on my doorstep this afternoon (Bought it from ebay, thanks Derek), must say I am impressed and have put it on to charge my 130ah trojan.
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Reply By: Mr Z - Monday, Jan 30, 2006 at 19:07

Monday, Jan 30, 2006 at 19:07
i asked the same question yesterday PostID: 30218

they seem to be the same as durst, which are heavier and not as weather proof as the c tek chargers

the c tek chargers are available in 7a and 25a

cheers
AnswerID: 151883

Follow Up By: Member - Ozdyssey (QLD) - Monday, Jan 30, 2006 at 21:43

Monday, Jan 30, 2006 at 21:43
even though their new ad say 7, 14 & 25.

14 must be on its way
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Follow Up By: Mr Z - Tuesday, Jan 31, 2006 at 16:36

Tuesday, Jan 31, 2006 at 16:36
hopefully!

maybe i should hold off on buying the 7a, and wait for the 14a
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Reply By: Member - Peter S (NSW) - Monday, Jan 30, 2006 at 21:36

Monday, Jan 30, 2006 at 21:36
Can someone please tell me what an AGM battery is? Sounds like a great battery if it has 100AH.

Cheers
Peter
AnswerID: 151929

Follow Up By: 4145derek - Monday, Jan 30, 2006 at 22:23

Monday, Jan 30, 2006 at 22:23
Yes. Pricey very heavy and at 6 to 10 years service life great value.

They don't leak, can be mounted on their side and have no internal resistanace against charge.

I don't supply to NSW only Brisbane but try your local battery shop. They should quote you around $260.00.

Regards Derek

ion 6FM90T</A
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Follow Up By: 4145derek - Monday, Jan 30, 2006 at 22:24

Monday, Jan 30, 2006 at 22:24
AGM 6FM90T
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Reply By: Member - Collyn R (WA) - Tuesday, Jan 31, 2006 at 13:32

Tuesday, Jan 31, 2006 at 13:32
Lewjack

There is a lot of misunderstanding re battery charging.

A battery is charged by applying a voltage across it that is greater than it has already. The bigger the difference between the applied voltage and the original battery voltage the greater the charge.

All basic battery chargers (ie non-three-stage chargers) work by producing a more or less fixed voltage (typically 14.4 volts).

A 'flattish' battery is likely to be at about 11.8 volts. Thus, when that battery is initially connected across a fixed voltage charger, there is a difference of 14.4-11.8 volts. That is 2.6 volts - and more than enough for effective charging. In this condition, a '15-amp' charger will charge at 15 amps.

But as the battery charges (and its voltage rises) the voltage difference decreases. By the time the battery has reached 50% charge (which is about the lowest it should be anyway) it will have reached about 13.2 volts - and the voltage difference is now down to 14.4-13 volts = 1.2 volts. At this stage the '15-amp' charger is typically putting out about 6 amps.

By 60%, charger output is down to 4-5 amps, by 70% charging it is tapering off to an amp or two. From there on it will drop to about 1 amp. It will eventually charge the battery and, if left connected will sooner or later boil it death.

With conventional chargers, the rated output is only realised with a close to flat battery. Three-stage chargers work quite differently - such that a 5-amp unit may well outperform a 15-amp conventional unit (and almost always a 10 amp conventional unit).

The initial charge of a three-stage unit is at 'constant current' - that is, as the battery charges the charging voltage automatically increases to maintain a constant voltage difference. So that whilst the charger is nominally (say) 5 amps, that 5 amps is maintained until about 80% charge.

If you routinely flatten batteries, then a 15 amp conventional charger will get them back up to 50% or so faster. But if you more typically wish to charge from (say) 50% to 95% then the 5-amp three-stage charger will beat that 15-amp unit hands down. Further it will charge that battery more deeply and far more safely.

This is why virtually every battery maker in the world recommends the use of high quality three-stage chargers.

I have both the Redarc and a good brand 15-amp charger side by side and can demonstrate this effect any time.
Trust this helps
Collyn Rivers
AnswerID: 152061

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