Visit our Popular Forums

Rays your Glass · 20-02-2018, 10:03

Hi folks. Needing to replace the batteries in my 306 Hunter. Currently there are 2-12V Interstate batteries used for house and starting. Boat is in Mexico where we only use for approx 25 days per year over the spring and fall. During use she is day sailed with an occasional overnight and then docked in a slip plugged into 110 every night. When not in use she is on the hard with a solar battery tender to keep the batteries topped off. For this little bit of use I'd like to get away with something on the cheaper side but still reliable for the next 4-5 years if possible. Your thoughts would be appreciated. Thanks

john61ct · 20-02-2018, 10:18

Best cheap value is pairs of FLA 6V golf cart batts.

Duracell brand made by Deka sold at Batteries+ and Sam's Club are fantastic for the money, about $1 per 12V AH.

Dunno in Mexico, but beware automotive or Big Box sources, 12V "deep cycling" is 99.9% fraudulent.

For AGM, stick to Odyssey or Lifeline if possible, then Northstar, Trojan or Rolls but all are pricey and don't last as long.

Best to keep Starter separate, but a good VSR does add to the cost.

**Pete7** · 20-02-2018, 10:27

My choice would be a pair of 12v type 31 flooded lead acid with caps so you can top the water up occasionally. I like the Varta Hobby 110AH which have lasted us 7 years so far, the first set lasted 6 years until l left them on by mistake.

The problem with just a pair of batteries is if you choose 6v and one fails later on you are stuffed. Equally since you are probably a very light user I would ignore AGM or gel batteries due to cost and the risk to them whilst you are away for long periods.

However, have you worked out how much electrical use you have in say a 24 hr period both at anchor and at sea? without this information you can't reach any sensible decisions on how big the battery capacity should be.

Pete

john61ct · 20-02-2018, 10:32

2 pair of those Deka GCs is around 400AH at 12V for about $400.

G-31 form factor pretty rare to find true deep cycling, sure Interstate (actually JCI) isn't bad, but something like Crown, US Battery, Deka or Rolls will last much longer, especially in the 6V or lower cells.

**Pete7** · 20-02-2018, 10:48

Quote:

Originally Posted by john61ct

2 pair of those Deka GCs is around 400AH at 12V for about $400.

G-31 form factor pretty rare to find true deep cycling, sure Interstate (actually JCI) isn't bad, but something like Crown, US Battery, Deka or Rolls will last much longer, especially in the 6V or lower cells.

True, but look at his usage, day sailing then plugged into mains each night, so does he need a 400AH bank at $400, or say a a pair of 12v batteries at a third of the price?

There is a chap called Rod who posts on here and who is also believes that the 6v cart batteries aren't necessarily the best choice. I tend to agree with him particularly in this case.

Pete

Rays your Glass · 20-02-2018, 15:21

I would agree with your line of thinking Pete. Thanks for all the input

Rays your Glass · 20-02-2018, 15:22

Thanks for all the input everyone it was helpful

smac999 · 20-02-2018, 20:06

if you bought a pair of golf carts you still need a 3rd 12v start battery. so you have to fit all 3.

if you currently get by with a single 12v house battery. without it dropping below 12v. then replace with similar for easiest results. you don't need more batteries unless you are ever going below on the existing one. depends how much you are running.

a single 12v battery for a 30' boat is tiny though. that won't even run a fridge for 24h. let alone anything else turned on.

john61ct · 21-02-2018, 06:57

I was just covering the redundancy issue.

Better too much capacity than too little, lower DoD will extend lifetime a lot.

But just one 6V pair plus a quality 12V as Starter does give redundancy.

But bottom line is, real deep-cycling quality in 12V is much more expensive per AH.

Personally I'd drop the dedicated Starter and go with two pair 6V,

put an adjustable LVD in between to keep the "starter half" from dropping too low, in practice may never kick in

maybe have a little lithium jumpstarter powerpack as backup just in case.

stormalong · 21-02-2018, 11:21

Quote:

Originally Posted by smac999

if you bought a pair of golf carts you still need a 3rd 12v start battery. so you have to fit all 3.

if you currently get by with a single 12v house battery. without it dropping below 12v. then replace with similar for easiest results. you don't need more batteries unless you are ever going below on the existing one. depends how much you are running.

a single 12v battery for a 30' boat is tiny though. that won't even run a fridge for 24h. let alone anything else turned on.

Why are you saying that? Do you mean a separate engine start battery? On a small boat a separate engine start battery may not be needed. The concept of the engine start battery is that it never gets discharged from "house" type loads. For the use that the OP described that may not be needed.

A battery that is going to be ignored for most of the year I would suggest getting the cheapest available and accepting the fact that it will need to be replaced every year or two. Battery life is determined as much or more by how well it is maintained than it is by price. IOW the best Rolls battery left discharged or dry will fail just as fast as a cheap battery.