Battery Replacment advice

[artbyjody]

Originally Posted by whroeder

Could you explain this please.

The amount of battery lead wire - you want it to be as short as possible as longer runs equates to more frictional losses (thermal)...especially when creating a "bank" which consists of batteries in parallel. So having one on the port side and another to the other starboard side...you lose current in terms of heat of it having to travel the additional distance. You want to group batteries as close as possible (especially if in a "bank") and as close to the main bus as possible to minimize losses...

[erps]

3. The saving weight / additional amps is a myth...

A couple of boats ago, I had an 8D battery for the house bank. It was rated around 225 amps. It was a bugger to move. A couple of golf cart batteries would have had around the same amp hour rating and while their overall weight might have been about the same, it's a little easier to lift two smaller batteries over one big one. I think that's where the weight/ease of handling comes in.

Our current boat has six 2 volt batteries for the house bank. It was a larger investment up front over golf cart batteries, but when you do the math with amp hours and number of cycles the $/amp was considerably less. We expect to get 15 years our of them before replacement at which time we'll re-evaluate whether that was the way to go or not.

[peteramc]

Hey Guys, Thanks for the comments, very useful, If I get rid of my 4 six volts and older 12 volt and then, run 1 optima blue top for starting and just keep one backup bluetop not wired and replace my house bank golf cart batteries(2), would that work? That way all the batteries are new... maybe I get one extra blue top optima and store it for backup...as Ive had batteries fail on me before...also I have loads of room in both banks. no space issues here... thanks...

[Newport41]

That sounds like a better plan. I was in your shoes not that long ago. After much research we ended up with a single dedicated starting battery as one bank and six Trojan T-105 batteries as our house bank. The T-105's are 6 volt golf cart batteries but wires to produce a single 12 volt 675 amp hour bank. The cost of all the T-105's was around $750 but that was up here in Canada before our dollar was worth more than the american dollar so I would assume they are cheaper than that now above or below the boarder. Compare other options amp hour for amp hour and see if you can find a cheaper option. The trojans also have a good reputation for being of good quality. If people try to talk you out of it based on weight ignore them. The amount of lead in a battery has a direct correlation to the amount of power it stores. Heavy is good in other words. And my advice when saildog tries to talk you into AGM's is that he is right, if you can afford them. For us AGM's where not worth the cost.

[k1vsk]

This is admittedly somewhat of a soapbox comment:
The choice between 12V batteries or combining 6V batteries is fundamentally a matter of personal preference. Notwithstanding the box size which should be the worst problem any of us ever have and the need for a few add'l cables, the issue seems largely aesthetic. Arguments can be made either way in terms of which is more problematic - the issue of a cell failure is common to both and can effect the bank regardless of which or how many batteries are interconnected.
This seems to me as just another ex of someone making a declarative statement as to which is "the best" when there are valid arguments either way - in itself not surprising but when someone apparently not as well informed comes along and asks a simple q, it is misleading at best to make such a statement without qualifying it as opinion.
This is not intended to be a criticism of any one person but rather the way in which we tend to communicate opinion(s).

end of soapbox and sorry if I offended anyone

[btrayfors]

Peteramc,

Lotsa good advice in the above (esp. Camraderie and Billyruffin); also some questionable stuff in other posts.

A few suggestions:

1. Re-read Cam's and Billy's comments and heed that advice.

2. There's nothing inherently wrong with using 6V batteries. In fact, it's the preferred way for many cruisers due to cost, efficiency, weight and ease of carrying, space, capacity, etc.

3. Wired correctly, there's also no problem with creating a single bank with batteries located port and starboard. Mine have functioned just fine that way for over 15 years (total of six 6-volt T-105s).

4. There's no chance of "thermal runaway" because of separated batteries; that's pure bunk. However, it IS a good idea to keep batteries as close together as possible to keep wiring runs short.

5. People tend to underestimate the size wiring needed to wire batteries together, be they 12V or 6V or whatever. Always use a heavy guage cable, 1/0 or larger, even if your batteries are close together.

6. The use of a single large battery bank for house plus a separate starting battery is the current preferred method, for several very good reasons.

7. You don't need to have them on a 1-Both-2-Off switch. A better arrangement for many installations is a simple ON-OFF for each bank (i.e., for the house bank and the starter battery).

8. Charging sources on a moderate or large-sized cruising vessel should all be wired directly to the house bank (not the starting battery). Use a battery combiner or, better, an EchoCharge device for keeping the starting battery topped off.

9. DO NOT think about keeping a battery "in reserve". Batteries deteriorate from the moment they leave the factory, due principally to lead-sulfate buildup on the plates caused by less than full charging and use. A battery sitting idle is a battery going bad.

10. Battery failures in a properly designed system are NOT all that common. You don't need to carry a spare battery.

11. The charging methods used are absolutely critical. There's a lot of info on this board and others (esp. SSCA board). Short version: be sure you have a modern 3-stage charger and leave it on. Very good chargers which are cost effective are the Iota series from Iota Engineering. They make models from 15A to 90A which use high-tech charging methods which extend battery life.

The advice in a previous posting to seek the counsel of a marine electrician is good. It can save you lotsa heartaches and $$$ in the long run. Batteries are expensive; wire prices are out of sight; and an inadequate or poorly designed electrical system can be anything from an expensive headache to a disaster.

JMHO,

Bill

[chucklesR]

Originally Posted by btrayfors

Peteramc,

Lotsa good advice in the above (esp. Camraderie and Billyruffin); also some questionable stuff in other posts.

7. You don't need to have them on a 1-Both-2-Off switch. A better arrangement for many installations is a simple ON-OFF for each bank (i.e., for the house bank and the starter battery).


Bill

Say what?
When saying others give bad advice, please ensure yours is good and follows Marine standards.
Simple on off switches are good for outboards only.

Otherwise,( and in this case surely) he will need a proper "make before break" switch including an alternator field disconnect with 1-both-2-off positions that even with a disconnect should never be in the off position with the engine running. Having two independent switches is a recipe for disaster, unsafe at best and a alternator diode or ancillatory equipment destroyer at best.

[christyleigh]

One thing I think needs to be kept in mind is that golf cart batteries were keeping golf carts going day after day...... way before 99% of the boats out here on sailnet and their high amp hour needs were even built. The thick plates of a storage battery compared to the thin multi plates of a starting battery, while not rocket science, have been perfected long ago in golf cart batteries.
The thing is you can't just walk into Interstate (where I buy mine) and get a real A - B comparison between 6v and 12v because the 12v equal of the 2-6v just plain doesn't exist there. Order up a 12v marine storage battery and they will hand you your 1 choice at x amp hours. Ask for 6v golf carts and you will have about 5 choices - with the x amp hours of the 12v about in the middle and the #5 at the top of the line will be a significantly more durable/amp hour battery.
To compare Apples to Apples you must go to the Rolls or other significantly higher $$$ 12v battery maker to match the amp hours in the top of the line 2-6v say from Interstate or Trojan.
So as the other 'soapboxer' above said it's a personal preference but there are some differences.
* Edit - Sorry for the incomplete posting - My last couple replacemetns have been 4D's and 8D's are so unreasonably heavy that I was 'tunnel visioning' on 4D's. As I remember 8D's would bring up my 1-5 loosly stated rating at least a notch... but their weight !!

[camaraderie]

This whole 12V vs. 6Volt thing is getting like the anchor threads. Both work just fine. Both are available in varying quality levels. And both can be made to perform well over a long period of time and cycles.

The MAJOR differences are that 6V T105 type is more easily moved as it is essentially 1/2 the size and weight of an 8D of similar 12volt amp hour capacity. Offsetting this is the extra complexity/cost of the additional cables required to pair the 6Volters. Take yer pick...it don't matter much as long as ya get a good one and then take good care of it.

[btrayfors]

ChucklesR,

You've got a point....but not the way you made it (quite apart from the snide tone and rebuke).

The point to be made is that you should never break the current to the field winding on an alternator while the engine is running. Damage could occur to the alternator EITHER by turning the switch off while the engine is running OR, if you have a battery selector switch which isn't make-before-break, switching from one bank to another.

My suggestion re: a simple on/off switch for the house batteries and another for the starter battery will work just fine -- assuming you know enough not to turn a switch off while the engine is running.

On-Off switches such as this one: http://www.defender.com/product.jsp?path=-1|328|51495|299265&id=341919
are made for such applications, and meet all ABYC standards.

Bill