Battery AGM (4) 6V GC2 vs (2) AGM 8D

[Torpedo Family]

I am looking at replacing my 8D wet cell batteries with AGM batteries. The two large 8D batteries that were factory installed weigh appx 158 each and replacing them with four GC2 6volt batteries that weigh 69.5 lbs each. The cost is only $80.00 differance, anyone have an experience with the four AGM 6volt batteries?

[92landyacht]

Both would work, but keep in mind that you want the total bank capacity to be as high A/Hr as possible. Also check the ratings as A/Hr can be based on various specified Amp draws. One battery may be rated 200A while another rated at 225A but the first is rated at a 5-hour rate while the other is rated at 20-hour rate. The second battery may seem like it’s better, but the first actually has more power density.

From what I've seen the 8D's tend to have a little higher A/Hr rating then the GC2's. The cheaper 8D's are lower and are very close to the better GC2's but the better 8D's have a bit higher power density then the GC2’s. I've seen some 8D's that are in the 240A/Hr @25amp draw range. More weight, in lead acid batteries, usually is an indicator of higher power density as well so saving 60lbs may not be the best.

I’m sure you understand but just for clarification, series batteries combine voltage but are limited by the lowest Amp rating in the series. That means that two 6v GC2's that have 180A ratings each tied in series would yield a total of 12V but only have a 180A rating.

While batteries in parallel would add amps but not volts. Two 6v 180A GC2's in parallel would yield 6V but have 360 Amps total capacity. Banking all four would give you the 12V you need but still only have 360A total capacity.

With the 8D's you could get 12V 240A x 2 or 480A of reserve power @ 12V.

You could also consider 4 12V deep cycle batteries in parallel if space is available.

Personally I prefer the least number of batteries to bank as each battery can be a failure point and requires more interconnections to fail as well.

Just my opinion though. I’m sure others will chime in as well.

[Torpedo Family]

Thank you for the information, that give me a lot to consider, I like to observation of four batteries to fail and connect as opposed to two with less connections.

[masseyfarm]

All depends on how much money you want to invest. I opted not to go with AGM because of the up front cost and chances of a failure of one battery which usually results in replacing all too start over.
The Trojan T105's are about $50.00/battery cheaper and will do most everything you want for a house battery bank. Depending on use/abuse, changing them every 5 years does not break my budget.

Trojan T-105 6V, 225AH (20HR) Flooded Lead Acid Battery

My other consideration was that I have three battery banks that are charged by all systems, and an AGM bank would not work with my setup.

Dave

Originally Posted by Torpedo Family

I am looking at replacing my 8D wet cell batteries with AGM batteries. The two large 8D batteries that were factory installed weigh appx 158 each and replacing them with four GC2 6volt batteries that weigh 69.5 lbs each. The cost is only $80.00 difference, anyone have an experience with the four AGM 6volt batteries?