Replacing 12 volt House battery with four 6 volt batteries for longer off shore power

[Goodxcharly]

The previous owner converted my boat from 2 - 12 volt to 4 -6volt, 2 banks. Works out great. Lots of power and keeps everything, electrical, pretty much the way it was other than replacing the batteries.
I use 2 100 watt Solar panels and could probably go up to a week and still be able to start the boat.
I’ve learned to use All on the battery switch when using the solar as a higher % of the solar charge will be retained by the batteries which diminishes as the batteries become fully charged.
I always think about converting to lithium though the 6 volt batteries serve my needs.
I power a fridge and freezer plus other random boat gadgets.
Hope to get 5 years out of the batteries. Then only $450. to replace them at Costco.

[GordMay]

Originally Posted by Ken Goodings

We disagree.
Our 6v golfcart batteries were 230ah capacity.
The original 12 v batteries of similar size were only 170ah
...

Two of your original 12V batteries, wired in parallel, provided 340A/Hr @ 12V.
Two of your 6V golf cart batteries, wired in series, only provide 230A/Hr @ 12V.
Per your spec's, those 12V batteries provided more power, in a similar space, than do the 6V version.

[merrydolphin]

I have had very good luck with Trojan T-105’s. The ones I have now are SEVEN yrs old. Have used T- 105’s on several boats with very good luck. HOWEVER , WHEN I REPLACE THEM I WILL BE GOING WITH Li Po 4 Lithium batteries. Far superior and now cheaper than anything else, when you look at long term usage ,weight, space, safety, FAST charging! The way to go.

[sailcrazy]

Following. We are 6-month liveaboards, then 6 mo up on the hard for hurricane storage. We converted from 2-8D 12v to 6-Trogen T-105s (675AHrs when new) about 20 years ago, and they have served us well....about 6 yrs per set. We've set it up with 3-12v "batteries" each w/an on/off sw for solation, to a busbar that feeds the house load. Our boat was built and bought in Asia, so she's wired for 230vAC, 50Hz. And over the years we've added an elect stove(no propane below deck!), a 230v refer sys, and a 230v watermaker.....we run the genset 1-2x/day. But the biggest issue we've encountered is batt charger size. We bought the biggest WestMarine had to offer at the time, a ProMariner 12-50 (amp), 3-legged charger (that's only17 amps per leg max!). Even though we have some 320w solar, and a windgen, we still need to run the batt chgr daily, for 2x longer than it takes to cool down the refer/freezer boxes and/or cook to get the batts back from ~80% to near 100% SOC. When you're putting your new scheme together, make sure you include a properly-sized batt chgr!

[holtjp]

Originally Posted by boatpoker

I have a few reasons to stay with lead acid ... For almost 30yrs as a full time cruiser/liveaboard and one time ABYC Certified Marine Electrician ... They are dirt cheap. I buy whatever Walmart or Costco has on sale. About 18 months ago I bought four for $100 each. I expect them to last as as long as all the other no names I've had ... about 8 years on average.

My battery compartment is properly designed and does not vent gasses into my boat. I don't need a BMS, I don't need a DC to DC converter, I don't need to modify my alternator. With our two 315W solar panels the only reason we need to got to shore is for water and diesel. We are at anchor about 7 months per year and see no reason or benefit from changing.

The phrasing of my statement/argument could be better. If you are happy with the status quo of your battery bank then by all means stick with your FLA setup. If you are not happy with your current battery situation, as the originator of the post expressed, then I would argue the swap to LFP batteries is the most logical and desirable solution. You appear to be getting acceptable life from your cheap batteries and your power needs must be relatively modest. The average lifespan for most FLA batteries is less than 500 cycles. Sailboaters are a tough use case as the engine is often run for only brief periods and the bank is not charged to 100% on a consistent basis. Nor is a sailboat optimized for solar charging due to extensive shading issues.

So long argument short, if you're happy with your current house bank then why make changes. If you're not satisfied, then the conversion to LFP batteries is the smarter choice.