Yea or nay, good batteries to start a growing system?

[tx2sturgis]

On the other hand, if you lose a cell in a parallel bank of batteries, you can unhook one of them and keep operating on the remaining good batteries. 

If you lose a cell in one battery of a series 6v combo, you are dead in the water.

It a bit like running dual tires on a motorhome or truck axle. Both tires share the load, in parallel. Sure, if one goes flat, you have a problem, but you can single them out and continue for awhile on one tire on that end of the axle.

I disagree that parallel batteries are 'bad'....

If they are matched properly, and good quality to begin with, they will give good service for years.

In the world of truck transportation, parallel batteries are the 'norm'. 

But there are valid reasons and arguments to use, or not use, either arrangement.

 

[John61CT]

My rule of thumb is at least 2 strings for redundancy.

Best to not go over 3-4. Which may mean going to very large cells for big banks.



Which means

 

[jimindenver]

It is the reason I have three 8-D's instead of six smaller batteries.

 

[tx2sturgis]

It is the reason I have three 8-D's instead of six smaller batteries.

You know those aren't true deep cycle! It will never work! Toss them and buy the right batteries dangit!

 

[jimindenver]

At 157 pounds each I ain't tossin nuffin.

 

[tx2sturgis]

You ol' scofflaw you....

 

[John61CT]

Yes, flooded automotive form factor batts like 4D & 8D are usually very heavy duty "dual use" starters, not designed for true deep cycling. Same as G-24, 27, 29, 30 & 31.

Rolls & Dyno are the only two exceptional makers I know of in the NA market.

Obviously, whatever batteries are working in use should be kept until their useful life is over. After a 20-30% decline in AH capacity - usually within 5 years even if coddled - they become increasingly likely to short or fail catastrophically in heavy use.

 

[jimindenver]

Lifeline is a pretty exceptional manufacture too but you really pay for the advantages they give you.

 

[John61CT]

Above was about flooded only.

Yes the top 3-4 makers of deep cycling AGM

Lifeline, Northstar, Odyssey, Firefly

pretty sure they don't even make dual-use starters, totally different market.

All excellent, none inexpensive.

 

[jimindenver]

Buy what you can afford

Buy what fits

Buy what you can charge

 

[JohnnyK]

Buy what you can afford

Buy what fits

Buy what you can charge

^^This^^

A pair of Trojan 6v T105s fit the bill for me. Next decision is which solar system will work best for us.