Refit: House/Starter Battery layout

[lkknapp]

I am in the midst of a refit and need to replace my batteries. Currently I have 3 optima 31 bluetops. They are configured with 2 as a house bank and 1 as a starter. They have been in service for about 10 years now and it is time to replace. They worked ok although I want to increase the house bank size. My refit list includes rewiring the AC and DC on the boat (long overdue).

My question has to do with the starter battery system design. I am thinking about going to Firefly batteries for the house bank and I am wondering if I should do a Firefly as the starter as well or if I can go for a less expensive starter battery. I currently charge my two banks off a Xantrex Truecharge 20 (older model) it allows me to hook up to 2 different banks but only has one setting for battery type. (Either Flooded, Gel, AGM). I am thinking I may need to get a different charger. Should I use two chargers? One for starter battery and one for house bank? Should I go Firefly batteries for house and a Starter AGM of some type (suggestions)? I believe that if I went to two different types of batteries I probably should not add a switch to combine them?

BTW: I am only worried about charging on shore power in this part of the design, Alternator/ Solar etc still to go.... I just have a stock Yanmar 3GM alternator currently.

How do you folks setup your starter system?

Thanks!
Linda

[john61ct]

I would do a big bank for House, and a smaller Reserve, same batts same age.

All charge sources direct to House, ACR to keep Reserve topped up as needed.

Belt & suspenders little lithium jumpstarter powerpak kept charged up monthly stored offline.

Cranking / engine / essentials circuits can A/B switch between either bank, use that facility to test/check Reserve regularly, otherwise kept isolated.

Firefly expense only required if PSOC abuse is unavoidable.

[smac999]

the firefly has a lower CCA then other batteries the same size. I would go with a normal AGM for the start. save money and more CCA. same charger should be fine on both.

20a charger is tiny though. if you get a bunch of fireflys you are going to want a much bigger one. or consider an inverter / charger if you are redoing the whole boat.

you could leave the 20a for the start battery

[ranger58sb]

Linda, you might hum a few more bars about your charging routine. Is this a day sailor, return to the dock -- and shorepower -- reasonably soon after being out for a while? Or are out on the hook for days and weeks on end, without routine access to shorepower? Or somewhere in between?

In some of those scenarios, Firefly Carbon Foam AGMs might be overkill, more expense without enough gain. In those cases, 2x house batteries and 1x start battery from Odyssey or Lifeline (for example) -- all AGMs and all from the same maker, all with the same charging profile -- could be fine. Or even Deka AGMs, even less expense.

Examples: 2x Odyssey PC-2150s (G31s) for your house, and 1x PC-1500 (G34) for your start. Or even just 3x PC-2150s. Or Lifeline G31 12V (GPL-31T, I think, something like that) deep cycles for your house and their 12V G31 start. Don't know Deka info offhand, but you can find similar there. If you do go with Fireflys for your house, the Odyssey PC-1500 is likely a decent starter choice anyway. YMMV, though.

A newer charger, more amps and with more set points for charging profiles, could be a good thing anyway, if you stay with AGMs. Batteries from different companiues (using Odyssey and Lifeline as examples) have different preferences for charge -- bulk and absorption -- voltages, so being able to pick the best voltages would be better than just being able to pick Flooded, AGM, or Gel. More charging capacity could also take advantage of the AGM's typically higher charge acceptance rate.

-Chris

[bradfordharley]

We have 900ah of agm and an optima start battery. My opinion (and you will get lots of differing opinions) is that your start battery doesn’t need a 3 stage charger. It is only used for a few seconds, especially with a modern motor. I use a xantrex echo charge and am very happy with it. You could also install a battery combiner.
There ar many ways to skin this cat.

[sailcrazy]

We redid our battery layout some years ago, and we followed the advice of folks smarter than me about batteries. Since the house is typically small loads for longer periods of time, we use deep cycle batts (we use Trojan T-105s). But the engine and genset starters are big draws for a short time...just what a car battery is designed to do. So we installed a car battery to start either. The start batts are kept charged via a Balmar Duo Charge off the house bank. Our house bank is monitored, and kept up by the batt charger, the solar, the windgen, and/or the engine alternator. Both sets are LA, so the charging parameters are similar....the system has worked very well for several years, thru Asia, to the Medd, and now the Caribb; we were full time live aboards in Asia, and only 6-7 months/yr in the Medd and Caribb.

[ranger58sb]

Originally Posted by sailcrazy

We redid our battery layout some years ago, and we followed the advice of folks smarter than me about batteries. Since the house is typically small loads for longer periods of time, we use deep cycle batts (we use Trojan T-105s).

That brings up a good point. My earlier comments start with the assumption that OP only has space for two 12V G31 batteries for the house and one for the starter, based on the 3X Optima info.

If there were space for 4X G6V GC2 golf cart batteries for the house, I'd probably change my tune a bit (but I don't think only 2x GC2s is all that perfect, just in case one were to go south).

-Chris

[rbk]

Also consider how your batteries sit in relation to heeling. Cells should not be allowed to uncover from electrolyte when heeled. Generally the fill caps should run perpendicular to the center line.

[billdre]

You mentioned use of shore power for most of your charging needs. So I don't have the technical detail that the other posters have offered but I do have a simple setup that works well for my type of sailing. So I have a Sears Die Hard Marine battery as my starter. It is hooked up to my electric start outboard and nothing else. The outboard keeps that battery fully charged all season. The outboard typically runs 30-45 minutes out and 30-45 minutes back each day sail. My house bank is 2 Lifeline 150ah AGM's which at hooked to a 30amp charger that is supplied by shore power only. I can go two or three days away from shore power when traveling and be back ready go the next day. But mostly I'm out for the day or overnight and the house bank isn't drawn down very much. I assume a diesel would charge a starter even more efficiently my 9.9 Mercury. The starter battery is 6 years old, the house bank 5, both still hold a full charge all winter and are ready to go in the summer.

[stnick]

I use 3AGM s and a house battery gel cell type 31 and a 100A smart charger .
I do use 240 Solar panels and I have a generator foir the AC at anchor.

[lkknapp]

Apologies for the delay in replying.... Wanted to thank you all for the ideas.
I am mostly concerned with getting a battery that has enough CCA added to the perceived need to keep all the batteries the same. I am still going back and forth on that one. I will likely try for 4 AGM of the same type and make one the starter and the other three the house. I believe that if I do go firefly I may need a different start battery though to get the CCA needed.
I prefer to stay away from flooded due to the difficulty getting at them to top up the cells.

[laika]

There are watering systems which make it easy to keep the batts topped up, even with very limited access. The Flowrite system is one example.

I have a 3GM as well. A house bank of two US2200s, and an AGM for start. Effectively, the AGM is a reserve as I always start from the house bank. The AGM will crank the engine over a hair faster and, because I never use it, is nice for it's low self-discharge, but my preference would be as John61 described and have all batteries onboard be the same make, same vintage. If you have the space and weight isn't a major concern, why not keep it low cost and simple and put the savings into more Ah or a better charging system?

[john61ct]

Originally Posted by lkknapp

I believe that if I do go firefly I may need a different start battery though to get the CCA needed.

Nope.

If you really want security, split the bank into two x2 batt sub-banks, keep them tied together at higher SoCs via an adjustable LVC.

If SoC / voltage drops then one pair gets isolated.

Put in a robust BSS 1/2/Both switch for cranking only.

[Q Xopa]

Originally Posted by john61ct

Nope.

If you really want security, split the bank into two x2 batt sub-banks, keep them tied together at higher SoCs via an adjustable LVC.

If SoC / voltage drops then one pair gets isolated.

Put in a robust BSS 1/2/Both switch for cranking only.

Yes agreed having a dual bank is a very good idea.

Most that do this have a 'main' and 'reserve' bank. Both banks can run everything, ie house and starter, usually through a load bus.

Usually they are not joined, except maybe for charging, usually through a ACR via a seperate charge bus. The main bank is normally on and powering everything. The reserve bank, is generally smaller and not normally powering any loads.

If the main bank has failed, switch it off, the the reserve on usinig either seperate switches or just the 1 and 2 positions.

I would not wire them together with a 1 2 B batt switch, ie Both position. Otherwise the bad bank can bring the good bank down when you most want power.

[john61ct]

Yes the 12B switch needs to be used judiciously, but in a true emergency is much better than scrambling for jumper cables.

In this case, only room for four units, a Reserve that is rarely used is too much dead lead.

Plus the prospect expressing skepticism that Firefly G31 has less cranking oomph than the Optima, figure better going half-half on the "low SoC reserve" idea.

Not an ACR is too high a cutoff, only joins while charging.

An adjustable LVD lets the owner tweak the SoC level to balance the ideal of keeping the bank whole as often as possible, and ensuring the cranking reserve sub-bank always has plenty of oomph left after the House loads' over drawing has triggered a split.