Size of Battery Charger

[zboss]

Also - two banks means two of everything to connect... more fuses, more wires, more circuit breakers, etc. This increases the costs and complexity dramatically. I don't know about everyone else here but I find my system already difficult to trace.

I am finding that its not the big stuff that causes you to go over budget, it's the little do-dads that are required to install or maintain that add up.

[sailinglegend]

Originally Posted by Jeff Millar

....Then I learned one battery bank is better than 2, which made sense.....

Here's my views on four good reasons for a bigger bank.

In the past it was often popular to have two service banks and no starter battery. It was thought a smaller bank would charge quicker. Current thinking is that it is much more efficient to have just one large service bank and a much smaller starter battery.

1. Doubling the service bank size means the life cycle is longer as the DoD is unlikely to fall so close to 50% so often. Life cycle at 50% DoD may be 1000 charge and discharge cycles. At a DoD of only 25% the life cycle may be 2500 or more.

2. Doubling the service bank size also means the “apparent capacity” is greater. Peukert’s law says that the apparent Ah size of a bank changes depending on the current draw.

A bank is designed to deliver a capacity with a current discharge that will flatten the battery in 20 hours. (The 20 hour rate)

So with a 100Ah battery, a 5A load will flatten the battery to 10.5v in 20 hours.

When drawing currents higher than 5 amps the "actual" bank size will be much smaller, so the bank will not last as long before it needs re-charging. Conversely when using much less than 5 amps the bank size will be larger and will deliver more Ah.

If a 100 Ah that battery has a Peukert value of 1.25, then higher or lower loads than 5 amps will change the actual capacity of the battery by the following amounts.

With a 10A load for 20 hours there are only 84Ah's in the bank.

With a 1A load for 20 hours there are 150Ah's in the bank.

3. Doubling the service bank size also means it will be more efficient and accept more Ah more quickly from all charging sources during the boost phase up to 80%.

It takes a bit of very over-simplified maths to prove the point, but a 100 Ah battery that is discharged to 50% may accept 20Ah in the first hour during the boosts stage, maybe 10 Ah in the second hour during the start of the less efficient absorption phase, and the remaining 20Ah in another 5 hours.

Doubling the battery size to 200Ah, with the same charging source of 20 amps, will accept 10Ah into each battery in 1 hour, that’s 20 Ah into the bank. In the second hours it will store another 20Ah. That’s 40 Ah replaced in two hours, as compared to 30 Ah with a single bank. In the 3rd hour it may still accept 20 amps into the bank because a single battery in the start of the absorption phase could accept 10 amps. That’s 60 Ah in three hours.

The key point is that for two hours it is still in the more efficient boost stage where the battery is taking all the current the charge source can give it. Note that the initial boost charging stage has captured 40Ah in two hours, and 60 amps in three hours. With the smaller bank it could only capture 20 Ah in the first hour during boost and 30Ah after the second hour during the start of absorption. The third hour may add another 5 amps. That’s 35 AH with one bank and 60 Ahs with two banks. So a bigger bank will be more efficient and accept more Ah more quickly from all charging sources.

Since a lot of the time we are only charging up to the absorption stage which is about 80-85% then this increase of stored Ah is significant.

4. If you have a larger bank - or many smaller batteries in one large bank, it is easy when they start failing to just disconnect the bad ones and run on the others as long as you can until you can replace the whole bank. This may also allow skippers to search around and find the batteries they really want - not just be forced to buy the local "rubbish" because they are desperate.

[sailinglegend]

Originally Posted by Jeff Millar

...In conclusion seems to me the best battery to buy and best suited for World cruising would be the 6v wet cell Trojan ( T-105 ) RELIABLE AND AVAILABLE ALL OVER.

Please correct me if what I SUMIZE IS NOT LOGICAL.

But AGMs are available anywhere in the world that they have a courier service. Because they are classed as non-hazardous then shipping is easy and relatively cheap. Order in your home country and have them delivered for a premium or maybe 20% for the delivery. Order Trojans locally and you may be paying a premium of 100%. Its worth checking out.

My Lifelines are in their 10th year by the way!!!!

[skipmac]

Originally Posted by sailinglegend

But AGMs are available anywhere in the world that they have a courier service. Because they are classed as non-hazardous then shipping is easy and relatively cheap. Order in your home country and have them delivered for a premium or maybe 20% for the delivery. Order Trojans locally and you may be paying a premium of 100%. Its worth checking out.

My Lifelines are in their 10th year by the way!!!!

I think it would still be a lot cheaper to buy Trojans or similar. Not sure of the prices in Turkey or EU but in the US Lifeline AGMs are over USD$3.00/amp hour capacity. FLA batteries if you buy 6V deep cycle and pair them up, about $1.00/amp hour capacity (in series at 12V). Even if they ship as non haz, batteries are very heavy and would add several hundred dollars to the cost, especially for a small shipment.

I am interested in how well you have kept your lifelines. How do you keep them charged? Do you keep your boat at a marina and plugged in?

Thanks
Skip

[sailinglegend]

Originally Posted by skipmac

....I am interested in how well you have kept your lifelines. How do you keep them charged? Do you keep your boat at a marina and plugged in?

Thanks
Skip

We are full time liveaboards in the Med cruising for 7 months of the year and hardly EVER going into marinas. I have a 280 amp Fischer Panda DC genny that I use maybe once every 10 days, only 140 watts of solar, and a 100 amp alternator. My bank is large - 1050 Ah - which I think is why it has lasted so well. We have no heavy loads - a 42 Hunter Legend - air con run occasionally from the batteries for a hour if they are charged. Until the last four years we haven't been aware of the need to regularly charge the bank to 100%, so in their early years they weren't looked after so well. I would like forumites to produce the written evidence that AGMs need to get back to 100% more often than FLAs. They are after all wet lead acids as well.

We now take every opportunity to get back to 100% every three weeks or so.

[Paul L]

Originally Posted by sailinglegend

.... Until the last four years we haven't been aware of the need to regularly charge the bank to 100%, so in their early years they weren't looked after so well. I would like forumites to produce the written evidence that AGMs need to get back to 100% more often than FLAs. They are after all wet lead acids as well.

We now take every opportunity to get back to 100% every three weeks or so.

FLA batteries can be safely equalized, thus undoing some
of the damage from not fully recharging. Most AGM manufacturers advise against trying to equalize. Although Lifeline does spec the procedure. Equalization side, there are a lot more instances of AGM failures in a short period - 1 to 2 years than FLA.

[btrayfors]

In post #137 above, sailinglegend has very clearly laid out four principal reasons why a single, larger house battery bank is superior to two smaller ones.

I agree with his post 100%.

This includes the note that with a larger bank, it is easy to remove (disconnect) batteries which may be failing. This is exactly what I did on my boat several months ago, when one of my six Trojan T-105's in the house bank rather suddenly lost about half of their capacity, after having repeatedly tested better than new during their seven-year service period.

I just disconnected that pair (one of the two batteries still tested like new) for a few months, and ran on the remaining four. During a recent 5-day mini-cruise off-the-grid, these four performed very well. However, upon return I did some more testing and found two more batteries which were beginning to lose capacity, testing at only about 80% of their "new" capacity.

So, I replaced all of them with six new Crown golf-cart batteries @ $99 each, giving me a total rated house bank capacity of 690AH.

I also replaced the 5-year old Deka group 31 start battery which had failed at the beginning of my cruise, again choosing the Crown brand made in Ohio.

Bill

[skipmac]

Originally Posted by sailinglegend

I would like forumites to produce the written evidence that AGMs need to get back to 100% more often than FLAs. They are after all wet lead acids as well.

I think at least some of the advise on AGMs is based on the manufacturers recommendations. For example, see the following information copied from the Lifeline web site.

For maximum battery life, a battery must be recharged to 100% capacity. Recharging to less than 100% may result in premature battery failure. Lifeline batteries are not covered under warranty if they are not recharged properly. For more information, please refer to our warranty policy.


After you have discharged your batteries, be sure you fully recharge them. You know your Lifeline Batteries are fully charged when you can no longer push more than .5amp/ 100amp/hr into them. Never let your batteries rest in a discharged state as they will begin to sulfate. Make sure that all battery charging devices are dialed in as close as possible to our recommended charging values. You should always fully charge your batteries prior to storing them. We recommend putting a maintenance charge on your batteries every 6 to 8 weeks for best results.

[btrayfors]

But, wait....there's more!

Sorry, had to gulp down some dinner!

The advantage of a house bank this large (690AH) is readily apparent. I typically draw about 150AH per day, or about 6.25 amps average over each 24-hour period. The 20-hour rate of my house bank is 690 / 20 = 34.5 amps. Therefore, my average draw of 6.25 amps is only about 17% of the C/20 rate, so the effective house battery capacity size is much larger than 690AH.

Bill

[pbiJim]

OK, so then, the big advantage of a large bank is that you end up using a smaller percentage of the available power so that puts you at a longer discharge rate & gives you more total power available.

The big reason that I prefer a split bank is for it's resistance to oops situations, like when a bilge pump switch sticks on for a week straight. With a single large bank, that would leave you with nothing when you return to the boat. With a split bank, only one of the two smaller banks would be dead & you would have the second bank to get you going again.

[btrayfors]

Originally Posted by pbiJim

OK, so then, the big advantage of a large bank is that you end up using a smaller percentage of the available power so that puts you at a longer discharge rate & gives you more total power available.

The big reason that I prefer a split bank is for it's resistance to oops situations, like when a bilge pump switch sticks on for a week straight. With a single large bank, that would leave you with nothing when you return to the boat. With a split bank, only one of the two smaller banks would be dead & you would have the second bank to get you going again.

Yes, Jim, that can happen. Most bilge pump switches are notoriously unreliable. They can fail closed, open, or even partially closed (in the case of electronic switches).

Best protection against that is to use a very high quality switch, like the Ultra Safety Systems Senior or Junior switches. After trying just about every switch known to man over a total of 40 boat years, a few years ago I bit the bullet and shelled out the $$$ for an Ultra Senior and and Ultra Junior model, with a high-water alarm. Only time in my boating life I've ever had NO problems with switches and finally have some confidence in them. TEF-GEL - Ultra safety systems - Home page

Bill

[sailinglegend]

Originally Posted by pbiJim

....The big reason that I prefer a split bank is for it's resistance to oops situations, like when a bilge pump switch sticks on for a week straight. With a single large bank, that would leave you with nothing when you return to the boat. With a split bank, only one of the two smaller banks would be dead & you would have the second bank to get you going again.

Are pump switch problems a good reason to connect the bilge pump to the starter battery. If a faulty switch drags it down then you have only one small battery to replace - not a whole bank.

Your emergency parallel switch will get you going and you may get your dead starter battery back to life.

[btrayfors]

Originally Posted by sailinglegend

Are pump switch problems a good reason to connect the bilge pump to the starter battery. If a faulty switch drags it down then you have only one small battery to replace - not a whole bank.

Your emergency parallel switch will get you going and you may get your dead starter battery back to life.

That's certainly one strategy. But, I think it depends very much on how you use the boat.

If the boat is to be left for long periods, I think I'd prefer connecting the bilge pump to the house batteries because it would pump for a much longer time than if connected to the start battery. And, the reverse of what you suggested is also true: your start battery would start the engine and your emergency switch could also be used to recharge the house batteries. And, with the pump running for a long time -- and actually pumping water if a leak were to occur -- the chances might be better that someone would notice.

BTW, you forgot the fifth good reason for using a single bank: no switching needed. If you've set up your system properly, there's no need to think about switching from one bank to another, combining, etc., and possibly making a mistake. An EchoCharge, DuoCharge, or combiner would do all the "switching" necessary.

Bottom line: nothing is 100%. But, I believe the best option is to connect the bilge pump to the house batteries and use a very high-quality, reliable bilge pump switch. In the end, the $$$ you put out for that switch will very likely save you worry and further $$$ outlays.

Bill

[Maine Sail]

Originally Posted by btrayfors

Bottom line: nothing is 100%. But, I believe the best option is to connect the bilge pump to the house batteries and use a very high-quality, reliable bilge pump switch. In the end, the $$$ you put out for that switch will very likely save you worry and further $$$ outlays.

Bill

A simple low voltage cut off device fitted to the B+ of the bilge circuit will save the house bank. This however should be in addition to a high quality bilge switch..

There are many LVC products out there....

IMHO a split house bank often leads to more problems rather than fewer and you really wind up with three banks not two.. House #1, House #2 & Start.......

With a single large house bank you wind up with House & Start....

[hellosailor]

Mark-
"A 200A alternator is going to require a serpentine belt "
Ergh, no. A ribbed belt, or a double-belt (ugh) but ribbed belts actually work better when they are not installed serpentine fashion. Serpentine will require the extra roller/tensioner, ribbed doesn't need that, and by only bending in one direction instead of two opposite ones, it lasts longer too.

Jim-
In your mad bilge pump scenario (role of the bilge pump played by Jimmy Cagney perhaps?) if the bilge pump is trying to keep your boat afloat and you are using separate battery banks, what have you done? You've sunk your boat, because the bilge pump stops running in 1/2 the time it could have had, killing one bigger bank. Still think two banks beats one that way? I'd rather put away one small battery (group 24 or smaller) and tag it as the emergency start/distress radio battery. And the gentler cycling (to half the discharge depth) on the bigger bank will probably more than pay for putting aside that "extra" battery, too.

Warranties-
Guys, I think you miss a major part of the reason for long warranties. Yes, everyone wants to weasel out of them when they are replacement warranties. But when they are pro-rata warranties, the weasel clause will almost never be used. Consider, you buy a Lifeline battery for $400 with a 5-year pro-rata warranty. And after 48 months, it goes dead on you. So now you go to an authorized dealer, and as everyone says "You can't sell 'em unless you get 'em in the showroom" and the warranty has just brought you into their clutches.
But wait, you say, you're just there for the free warranty. Sure. That warranty is prorated and since you got 80% of the battery life, your warranty buys you a 20% discount off the LIST PRICE of a new one. Which may be $600 (they go up every year) so you're still going to spend $480. Ka-Ching!
All that warranty buys most customers is...nothing really, it just ensures their business comes back when the product dies, instead of seeing you shop around all over with the competition.

Now on the other hand if you cheap out and buy a WalMart battery...you get a three year full replacement warranty. The battery isn't as good as a Lifeline, but damn, in you're cruising in WallyWorld territory, can you beat the overall price and warranty?

Decisions, decisions.