Ashrez

Battery Spec AGM or Standard?

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I  was wondering if anyone has any idea if our car can use an AGM Battery? Modern cars have a lot of electronics that draws power even when it's just parked in a garage so i find myself having to hook up a trickle charger to keep it happy otherwise it goes flat if i don't use the car for more than a week. AGM batteries supposedly lasts longer and i was wondering if it could mitigate this issue by the use of one. Going through the owner's manual was no help.

Any input or experience with AGM batteries is greatly appreciated.

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1 hour ago, Ashrez said:

I  was wondering if anyone has any idea if our car can use an AGM battery? Modern cars have a lot of electronics that draws power even when it's just parked in a garage so i find myself having to hook up a trickle charger to keep it happy otherwise it goes flat if i don't use the car for more than a week. AGM batteries supposedly lasts longer and i was wondering if it could mitigate this issue by the use of one. Going through the owner's manual was no help.

Any input or experience with AGM batteries is greatly appreciated.

It is a misconception that AGM batteries "last longer". The length of time a Battery will be able to stand idle is governed by 3 things or possibly even 4 if temperature is configured into the equation. Cold weather has the effect of reducing Battery output.

(1) the amp/hr capacity of the Battery. The higher the better.

(2)The quiescent current drawn from the Battery. The current draw by the entry, and alarm systems while the car is turned off. 

(3) the self discharge rate of the Battery. This is quite low usually around 1.5% of capacity per month. 

So an AGM Battery of the same amp/hr capacity as a flooded lead acid Battery will hold up for the same period of time. AGM batteries however are supposed to stand up better to being discharged without being damaged as much as flooded batteries. AGM batteries are however more easily damaged by being over charged or charged at a higher rate than the maximum specified, and can therefore be damaged by some alternator charging systems that will put 80 to 100 amps into a Battery that is partially discharged. This leads to drying out of the cells as the only liquid acid is held like a sponge in the glass mat separators. Flooded batteries have copious quantities of liquid in the cells that can also topped up with distilled water as this is gassed of in high rate or overcharge situations.

AGM batteries are considerably more expensive than flooded batteries, and tend not to have the often long guarantee "5 years" that flooded batteries have.

Use as high a capacity Battery that will fit in the carrier. I replaced my GS450H 70 amp/hr Battery with a Battery rated at 110 amp/hrs modifying the Battery tray. At the end of the day however you can only keep drawing from the well for so long till it becomes empty, and rain is needed to fill it again.

John

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22 hours ago, Britprius said:

It is a misconception that AGM batteries "last longer". The length of time a battery will be able to stand idle is governed by 3 things or possibly even 4 if temperature is configured into the equation. Cold weather has the effect of reducing battery output.

(1) the amp/hr capacity of the battery. The higher the better.

(2)The quiescent current drawn from the battery. The current draw by the entry, and alarm systems while the car is turned off. 

(3) the self discharge rate of the battery. This is quite low usually around 1.5% of capacity per month. 

So an AGM battery of the same amp/hr capacity as a flooded lead acid battery will hold up for the same period of time. AGM batteries however are supposed to stand up better to being discharged without being damaged as much as flooded batteries. AGM batteries are however more easily damaged by being over charged or charged at a higher rate than the maximum specified, and can therefore be damaged by some alternator charging systems that will put 80 to 100 amps into a battery that is partially discharged. This leads to drying out of the cells as the only liquid acid is held like a sponge in the glass mat separators. Flooded batteries have copious quantities of liquid in the cells that can also topped up with distilled water as this is gassed of in high rate or overcharge situations.

AGM batteries are considerably more expensive than flooded batteries, and tend not to have the often long guarantee "5 years" that flooded batteries have.

Use as high a capacity battery that will fit in the carrier. I replaced my GS450H 70 amp/hr battery with a battery rated at 110 amp/hrs modifying the battery tray. At the end of the day however you can only keep drawing from the well for so long till it becomes empty, and rain is needed to fill it again.

John

Thank you John for the explanation. My current Battery is 70 amp/hr as well so i should be looking to get a higher capacity as well then with the right size. There's just so much to choose from. What would you say would be a good brand to go with?

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2 hours ago, Ashrez said:

Thank you John for the explanation. My current battery is 70 amp/hr as well so i should be looking to get a higher capacity as well then with the right size. There's just so much to choose from. What would you say would be a good brand to go with?

Reza, there are many good manufacturers of batteries, but if you stay with known brands "such as Bosch, Varta, and Exide  I do not think you can go wrong. All of these manufacturers do 5 year guarantee versions for very little extra cost. 
If your car is left standing outside a solar panel charger would help keep the Battery charged, and extend it's life. If you do purchase a solar panel make sure it has an output of at leased 20 watts. The cheap small 10 watt panels are a waste of money.

John.

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