Other than amount of lead and glass mat, what are the diferences between AGM and FLA?

[wdc]

Hello, I'm trying to understand what makes a deep cycle battery "deep cycle", AFAIK the only two differences between a "deep cycle" AGM and a car FLA is that the AGM has more lead and the glass mat, if this is true, a 25Kg "no gassing" FLA would be as good as a 25Kg AGM but, since I don't think this is true, the glass mat has to have something that makes the AGM better at deep cycling, has it?

also, why does an AGM need more current to charge than a FLA?

thanks in advance.

[SunEagle]

Deep cycle batteries usually have thicker plates and lower resistance. IMO the better deep cycle battery is an FLA. While the AGM can be mounted in any direction and not spill they usually cost more and actually have a lower cycle count. The AGM can also be charged faster but for the buck a low voltage (2v, 4v or 6V) FLA is better then just about any AGM.

[wdc]

Deep cycle batteries usually have thicker plates and lower resistance. IMO the better deep cycle battery is an FLA. While the AGM can be mounted in any direction and not spill they usually cost more and actually have a lower cycle count. The AGM can also be charged faster but for the buck a low voltage (2v, 4v or 6V) FLA is better then just about any AGM.

Thanks! I assume when you say the best deep cycle battery is an FLA, you are talking about Trojan, Rolls or Surrete ones, those are so expensive for my wallet that I can only dream about them right now.

Why a low voltage FLA is better than a 12V one?

[SunEagle]

Thanks! I assume when you say the best deep cycle battery is an FLA, you are talking about Trojan, Rolls or Surrete ones, those are so expensive for my wallet that I can only dream about them right now.

Why a low voltage FLA is better than a 12V one?

The simple reason is that a low voltage FLA allows you to increase the size of your battery Ah rating without wiring the cells in parallel.

I can get 2 x 6V 225Ah FLA batteries for about $250 wire them in series for a 12V system or get 2 x 100Ah 12v AGM's and wire them in parallel but they will probably cost more and yield less cycles.

[peakbagger]

I used to work for a firm that did a lot of remote power systems that went in all over the world in nasty environments on all the continents Many were unattended or rarely attended sites like monitoring sites, remote pipelines and unattended platforms in the Gulf of Mexico. We almost exclusively used AGMs. They just held up better to abuse in shipping and day to day operation. The environments were harsh and everything would get packed into ConEx boxes modified so once they were shipped to site they could be quickly assembled into a remote power station. The logistics of getting there meant stuffing as much stuff into each box as we could. AGMs could be stacked in racks in cabinets with the buss bars on the sides. FLAs could not so they took up more room. AGMs didn't need watering and no acid leaks with no outgassing. Even though our designers tried to maximize battery life it was hard service, so "if in doubt change them out". The AGM cabinets were ordered with racking gear built in so swapping them out although still not a pleasant task was a lot easier than FLAs.

[wdc]

I used to work for a firm that did a lot of remote power systems that went in all over the world in nasty environments on all the continents Many were unattended or rarely attended sites like monitoring sites, remote pipelines and unattended platforms in the Gulf of Mexico. We almost exclusively used AGMs. They just held up better to abuse in shipping and day to day operation. The environments were harsh and everything would get packed into ConEx boxes modified so once they were shipped to site they could be quickly assembled into a remote power station. The logistics of getting there meant stuffing as much stuff into each box as we could. AGMs could be stacked in racks in cabinets with the buss bars on the sides. FLAs could not so they took up more room. AGMs didn't need watering and no acid leaks with no outgassing. Even though our designers tried to maximize battery life it was hard service, so "if in doubt change them out". The AGM cabinets were ordered with racking gear built in so swapping them out although still not a pleasant task was a lot easier than FLAs.

thanks, I've dediced to stay away from AGM batteries because of this:

1) they are too sensible for high temperatures, they shouldn't be charged above 50ºC ambient and I'm not sure if in summer my battery would be exposed to 50ºC or more.
2) they need to high current to be charged, for a 100Ah battery the min current to charge should be 20A and I don't have that amount of panels. Also, I read that, if the battery don't get the min current when charging, it will suffer or chronic undercharging and capacity loss.
3) they are too sensible to overcharge, if the CC is not precise the voltage applied to the battery could be too high and gas could be produced, that will damage the battery, that's why they suggest use of a temp variable CC.

So I'm going to stick with heavy FLA's.