AGM Batteries

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AGM Batteries

Post by Bignuggs on Tue 20 Jan 2015, 5:28 pm

First topic message reminder :

Here's something that has me puzzled.
If you start with a new AGM battery, discharge it a few times and recharge, do they get better.
It seems like it, as the one battery I've been using is lasting longer after each discharge/recharge.
The battery is only about 4 months old and I've been using it a fair bit to run the fridge.

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Re: AGM Batteries

Post by Boulder on Wed 18 Feb 2015, 12:10 pm

Bignuggs wrote:It's a never ending saga  lol!
So I've contacted the Projecta mob about the 8amp/240v charger.  It appears according to what they tell me, the 8amp charger is too small and they now suggest using the 21amp charger to get a full charge into the 100ah batteries.
which brings me back to the 120w solar panels which has a standard 8amp regulator.  I'm now waiting on an answer about that.
Bugger me, is the bar open yet    

I am planning to use a 120ah AGM and from what I've been told on the size smart charger to use then work on 10% of the Battery's capacity. Therefore in your case a 10 amp charger for a 100ah or 12 amp for a 120ah but I am yet to decide on whether to go larger or not.

I have also been told not to discharge the AGMs too much before doing a recharge so as to maintain a long cycle life from the battery.
I will only be using a genny for recharging so if using a 12 amp smart charger researched showed it would take several hours to recharge a 120ah AGM back up to 100%.The amount of discharge one decides on from the battery will dictate how long to run a genny and fuel used.

Now if using the higher 21 amp charger as the Projecta mob suggested then for a 100% full recharge then my genny run time would be greatly reduced.

I see you mentioned your 8 amp Projecta is a Pro-Charge model although they make a intelli-Charge model as well which I will go for.
I suppose if I decide on a the 25 amp model I could use the option to set it to the lower 12 amp setting.
However I could use the 25 amp for quicker recharge to save on fuel and disconnect the charger say when the battery is 85% full.
Then when home with normal 240v mains supply use the charger at a lower amps to do a full 100% recharge.

I wonder if using my procedure by recharging each day with 25 amps to get the AGM only to 85% when out bush then how many days could I go for before I would need to do a complete 100% recharge using a lower amp setting and therefore hopefully maintain a long cycle life from the battery?

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Re: AGM Batteries

Post by Bignuggs on Wed 18 Feb 2015, 12:42 pm

Yep, I've got the 8amp Procharger and the 120W version of the folding solar panels.

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Also got my 100ahr batteries in these boxes
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Now if what the manufacturers say is correct, while I have the fridge and what ever else connected to the battery box, I can still connect the solar panels at the same time.  so I would be charging while using the battery.
The true test will come if I can get out this year and use them.  so if both batteries are fully charged before heading out, I should be able to get away with only using 1 battery constantly or maybe not.

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Re: AGM Batteries

Post by Metamorphic on Tue 24 Feb 2015, 8:05 am

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Yes your right Bignuggs, AGM Deep Cycles love to be constantly discharging and charging but as others have stated, do not discharge them below a certain level or you will reduce their lifespan.

For my Thumper Extreme 120AH AGM I use the level 40%. My voltage meter on the topright corner tells me this.
(12.7 v is full charge, 10v is completely flat). Having said that, I can usually get mine at around 13v fully charged and wont let it discharge below 11.3 - 11.5v.

For charging i have a 20amp 3 stage which runs off 240 (my genny) and 2x80watt solar panels charging through Anderson plugs.
I was advised never to charge above 27amps for the 120AH or I could risk damage to the glass matt cells.

I always run the solar to charge during the day as Im discharging also. I always top up to full charge every night using the genny if there is any shortfall from solar.

Now under OHMS Law I=P/V or Amps = Watts/Volts, with 2x80w panels this gives me approx 13.3amps of charge providing both panels are in full, direct sunlight of course

13.3 = 160/12. Im going to lose a bit in resistance (Ohms) R=V/I or Resistance = Volts/Current (0.9)

So i figure 12amps is roughly correct in full sunlight charge of both panels.

This is more than enough to keep running my 65lt Waeco and and a few other low wattage devices and still gain charge above discharge rate on solar. (as i said, on a good day of full sun)

Anyhow, this is how i try to maintain my AGM DC system and it seems to hum along fine on those long prospecting trips out scrub and have had no troubles so far!

Cheers all

Edit: Remembering that ciggy lighter connections are rated at 8amps so this would be a bottleneck if your charging at 12amps.

A Merit connection is rated at 16amps, and an Anderson plug @ 50amps.

Anderson may be higher than needed, but resistance is less and no chance of 'bottle-necking' your charging system.

For keeping an accurate eye on charge/discharge rates [You must be registered and logged in to see this image.]

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Re: AGM Batteries

Post by Nanjim on Tue 24 Feb 2015, 12:26 pm

Hay Meta,
What's that little gizmo with the two Anderson plugs ...
At the bottom of the pic....

Cheers Nanjim
Jim

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Re: AGM Batteries

Post by Metamorphic on Tue 24 Feb 2015, 2:42 pm

Hey jim

Was going to post the ebay link to it mate, but being new i gotta wait 7 days before linking.

Search 'Solar watt meter' on ebay.

I think Jaycar have them as well from memory?

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If you dont have Andersons coming from your load or source, simply just buy the 'Anderson to Alligator clip' adapter from Jaycar

Dude on ebay said, "Fish tanks can get expensive to run.  I always wanted to know if I could run my tank off solar power.
Here is the Watt Meter measuring the load through an inverter.
If you are interested in off-grid living (or you're a doomsday prepper) then this is a handy device to have".

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Cheers mate Wink

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Re: AGM Batteries

Post by Nanjim on Tue 24 Feb 2015, 3:16 pm

Meta,
Thanks for the info. I will check them out ....
Will be back in Perth this week ...

Cheers Nanjim
Jim

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Re: AGM Batteries

Post by Jack-Tar on Mon 02 Mar 2015, 1:00 am

Hi guys I would like to add my 2 bobs worth on a few things I have read throughout this thread.
Plan to not run your AGM batteries lower than 50% if you want them to last for any reasonable length of time. 70% is the lowest I will take mine (they are 5 years old now). A lead acid battery (gel, AGM or wet cell) only has a certain amount of charge cycles (some manufacturers claim between 300 and 400) and the deeper you discharge the battery the more permanent damage you are doing to it. By running the depth of discharge down to 11.5 or lower will mean you will be replacing that battery within a year or two if you are doing that daily. The battery should be considered flat at 12.1 volts with a load on it. You will notice an AGM battery may show 12.5 or 12.6 v with no load but as soon as the fridge starts it will drop to around 11.5 v, that is well and truly flat and you are destroying the battery.

An alternator will never charge a battery to full, they are not designed to do that. But if you have a solar system set up it will finish off the charging cycle. Deep cycle batteries require a multi stage charger to charge completely, that can be a 240v charger or a good quality solar charger (as long as it is a multi stage charger). My preference is a PWM controller as opposed to the MPPT solar controllers for the reason that the MPPT controllers don't like another power source coming in at the same time. An example of that is with my Motorhome whilst I'm driving the alternator is charging my battery banks as well as the solar fitted to the the roof. The MPPT would see 2 power sources coming in and  may stop the solar input (although I spoke to a solar dealer/fitter recently and he claims the better controllers don't do this).
Cliff, you will need to increase your solar panel size not just the solar panel regulator. This was mentioned earlier so I need not say anymore. Another option you have is to buy a reasonably sized 3 stage charger (20 amps) for when you are out bush and need to push some charge into the batteries. The trick here when using a genny is that you use the battery charger only for the bulk charge and then you done. The bulk charge will be coming in at 14.4v or there abouts depending on your settings and then it will drop back to a absorption charge when the battery reaches around 80%. The reason why you stop charging when the bulk charge finishes (when out camping) is it will be a waste of fuel to achieve the final part of the charge. If you do this early enough in the day the solar should finish off the charge cycle. Also the reason for a bigger charger is that you don't want to be running your genny all day just to put the bulk charge back in. Keep in mind if the sun is shinning then you should have the panel pointing at it, don't wait till the battery is low. Adjust your temp up a bit, 0 is far too cold for a fridge. It's great for the beer but the compressor will be running longer and you will be using more power. I am back in Perth again and will be happy to come over if you need a hand.

Regards
Craig

Jack-Tar


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