Lead Acid vs Dual purpose Batteries for Solar?

[McIntoshUSA]

I have 300 watts of Solar and a MPPT controller. It is time to replace my house batteries. I currently have 3-29 lead acid batteries. I plan to replace them with 3-31 batteries. I have a separate engine battery.

Question: Is it best to replace them with 3-31 Lead Acid Deep Cells or 3-31 Dual Purpose batteries. I was planning on going with 3-31 Lead Acid Deep cells, but a friend of mine had a good point. He said that Deep cells are Not made to have a charge every day. (ie - Solar charging daily) He said that the Dual purpose batteries would last longer since they are made to take a charge every day like a regular car battery? Decisions? Anyone have any experience on how long Deep Cells would last vs Dual purpose batteries being charged daily by solar? PS: I am in Florida where the heat takes a toll on our batteries. Thanks

 

[Brian S]

I think that's wrong there. All lead acid batteries prefer to remain at full charge. I don't see how charging them every day is a problem, especially if you have a proper charge controller.

The dual use batteries are not good for storage use. A starting battery uses thin plates, or sometimes even foamed lead, to give lots of surface area for plenty of cranking current. This thinner lead can't handle being drawn down, and sulfating, and the plates can wear out and deteriorate if they are drawn down to lower voltages. But a deep cycle battery uses thicker lead to provide more consistent current, and also to be able to handle the effects of being drawn down to lower levels. So, a "dual purpose" isn't as good at either use scenario.

 

[Johann]

This might help:
http://www.pbase.com/mainecruising/deep_cycle_battery

 

[Benny17441]

Stick with deep cycle batteries, which in reality are dual function batteries, as they will provide more charge/ discharge cycles but can safely be used to start the engine. True deep cycle batteries are sensitive to movement and are usually found in massive banks for computer systems backup and not suitable for marine duties. What is sold as a marine dual function battery is more of a starter battery than anything else. Would only use them in powerboats with small needs for discharge.

 

[Maine Sail]

I have 300 watts of Solar and a MPPT controller. It is time to replace my house batteries. I currently have 3-29 lead acid batteries. I plan to replace them with 3-31 batteries. I have a separate engine battery.

Question: Is it best to replace them with 3-31 Lead Acid Deep Cells or 3-31 Dual Purpose batteries. I was planning on going with 3-31 Lead Acid Deep cells, but a friend of mine had a good point. He said that Deep cells are Not made to have a charge every day. (ie - Solar charging daily) He said that the Dual purpose batteries would last longer since they are made to take a charge every day like a regular car battery? Decisions? Anyone have any experience on how long Deep Cells would last vs Dual purpose batteries being charged daily by solar? PS: I am in Florida where the heat takes a toll on our batteries. Thanks

Your "friend" is simply incorrect. That said, any group 24, 27 or 31 flooded battery is really only a "quasi" deep-cycle battery. They should really labelled as "light-cycle" not deep-cycle...

BCI Groups 29, 30 & 31 are all the same case size, don't let the marketing fool you. In that case size Trojan, Crown and US Battery build batteries that can deliver the actual "rated" Ah capacity pretty consistently. I have yet to test any other group 24, 27 or 31 flooded battery that could delivered it's Ah capacity. This is not to say they can't or won't but I suspect they are less likely to than one from US Battery, Trojan or Crown.

Before you invest money in batteries for cycling use you may want to read this;

What is a Deep Cycle Battery (LINK)


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[McIntoshUSA]

Thank you everyone.