how to choose the right AGM battery?

[catmomtoo]

Hello battery aficionados! 

I've been researching and still no wiser on AGM battery quality or how to find side by side reviews for these. A brand name is no different than the same product with another company's brand on it. Today's its 34 degrees, so I need a battery that can go to 20 degrees and still perform. I have 200W of solar panels, and a 1250 Aims power inverter, battery controller and meter installed. I want to run a laptop and speakers for ten hours a day, and a plug in electric cooler 24/7. Maybe a USB fan occasionally.

>>SLD AGM deep cycle batteries range in price from $130 to $500+ for ONE battery. Can anyone tell me how to really compare these?   THANKS in ADVANCE!!

 

[drysailor]

Hello battery aficionados! 

I've been researching and still no wiser on AGM battery quality or how to find side by side reviews for these. A brand name is no different than the same product with another company's brand on it. 

Hi Cat - if you haven't already, try searching for "RV battery reviews". Always keep in mind that you're looking for deep cycle batteries. If you do find some good data, it might be nice to post that here as well..... Good luck.

 

[bullfrog]

When I looked a couple years back there were very few manufactured in the United States but I found one through Batteries +, a Duracell I believe that they were able to order from the factory in Pennsylvania. It arrived and was less than 6 weeks old. They were around $300 each. I bought 2 so a little over 100 amp hours usable storage for my 305 watt solar. You really don’t want to drain the batteries any more than you have to and recharge them daily if possible. You will come closer to doing what you want by making everything 12 volts which is more efficient, that inverter will use a lot of power just because of its size in my opinion.

 

[Weight]

Duracell are manufactured by East Penn. They are the same as Deka. They also label NAPA, West Marine, and Walmart's line. I prefer Duracell. They are a good middle grade AGM battery. They make the best gel battery and GC2 flooded.

 

[Drmiller100]

A coleman cooler or a good compressor refrigerator?

How many amps does each unit draw?

 

[Matlock]

I'm not aware of a AGM battery that can be full recharged at 20*. Actually I'm not sure any current production battery will survive cycling at 20*F without adjusting the charger amps. Most recommend you keep them warm for charging.

Checkout Lifeline AGM batteries and see what the say regarding below freezing temps in their spec sheet. It's a great battery @ $330 each for 6V.
https://lifelinebatteries.com/

Also, for whatever battery you choose email the manufacturer "tech support" before buying. They will have recommendations beyond the one-off user like me.

 

[MrAlvinDude]

As I have only ever used seal lead acid batteries as a starter battery in my cars. I would say that charging a lead acid battery at 20*F (-6*C). Is quite possible.

I have operated vehicles (and started them, after sitting for 12-16 hours) in temperatures down to -10*F (-24*C).
And the batteries have definitely needed to get charged again after such an operation.

As the cars I have used, all have had the batteries in the engine room, they would however naturally have been heated quite quickly to above freezing. So above 32*F (0*C).
So I have no experience about trying to charge a sealed lead acid battery if it remained at temperatures below freezing, Like 20*F (-7*C).

---

At this page (Battery University) they simply state that lead acid batteries need to be charged slower than 1C  - sometimes at 0.1C in order to avoid damage to the special sealed-in-gasses (the gasses that get absorbed - the A in AGM) in a sealed lead acid battery.
https://batteryuniversity.com/learn/article/charging_at_high_and_low_temperatures

C is for capacity, so for a 100Ah battery 1C is 100Amp. For a 35Ah battery 1C is 35 Amp
For a 100Ah battery 0.1C charge rate is thus max 10 amp charge rate.


And on this page they have a chart that shows capacity rates at different temperatures.
https://www.victronenergy.com/blog/2019/01/09/lead-acid-battery-charging-in-cold-weather/

It does not quite show how to charge, but since the charge rate should never be above 1C, and the chart does show the capacity at different temperaturs (at different load rates), the chart can also be used to give a good indication of highest charge rate, as charge rate should never be above 1C, and preferably 0.5 or 0.1C, when at or below 14*F (-10*C)

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So all in all: use lower charge rates (to avoid damage to SLA/AGM batteries), and charge to a higher voltage (for a 100% charge state), if the battery is being charged at low temperatures.

Also remember that the load capacity of a battery is quite a bit lower at lower temperaturers.

So there is many benefits if one is able ro keep a lead acid battery above freezing. And preferably above 50*F (10*C).


So a heating blanket, may prove to increase the capacity of an AGM battery, by more than the heatring blanket needs in order to increase the temperature of the battery.

And heating the battery a bit, before using it. And especially before charging it, will improve the use-ability, AND the charge-ability.

 

[Drmiller100]

Old school lead acid batteries can indeed be charged at very low temps. Recognize at cold temps lead acid batteries are less efficient, take longer to charge, and frozen engines take a lot more power.

Lithium does not work when cold.