When I bought Tortuga it had what appeared to be the original batteries. They were monsters and I very nearly fell off the ladder carrying the 90lb Surette (far right in the photo).
After failed attempts to resurrect the old batteries I replaced them with three used Group 27s for the house bank and an isolated automotive starter battery. The house bank are showing their age. With the fridge on overnight they draw down to 12v by early morning. Time for new batteries.
I am leaning towards two sets of 2- 6v batteries wired in series. Why 6v and not 12v?
The short answer is the physical properties of the six volt make a better deep cycle battery then a 12v.
Both are lead acid batteries, both contain 2.1 volt cells. Three cells in the 6 volt battery and six cells in the 12 volt battery. The 6 volt battery has more space per cell than the 12 volt hybrid so the plates are thicker and will last longer. The 6 volt will be able to discharge deeper than any hybrid 12 volt deep cycle. Two 6 volt deep cycle batteries are a much better buy than two hybrid 12 volt batteries. quote credit
There’s lots of discussion on this in the RV and sailing forums, here’s another take by Beth and Evans on 6v. The gold standard 6v battery seems to be Trojan T-105, but I think I am going to see what I can get from Costco. With solar panels charging the batteries constantly, and solar providing most of the load during the day, with a smart external regulator on the alt, combined with the fact that we won’t be doing heavy cycling, our the batteries are will be living the life of Riley, so I think I can get away with cheaper batteries.
Found this comparison of Trojan T105s vs Costco clones:
|Capacity minutes @ 25 amps:||447||425|
|Capacity minutes @ 75 amps||115||100|
|20hr Rate AH||225||220|
- Costco part # 245725 – perhaps this is obsolete or US only part #?
- The current Canadian part number for the only Costco golf cart battery is #114723
- The Costco batteries are manufactured by Johnson Controls.
As of publishing, Spring 2015:
Costco price $ 134.99 only avail in Peterborough or Kingston.
Crosstown Battery: US2200 – $172.00 less $10 per core exchange.