Battery charger

[rwappleton]

We are moving along with the final work before leaving the yard and the PO installed the battery charger incorrectly and it fried.

Yard says we need a 100 amp 4 leg charger.

We have 4 8D's 2 port and 2 starboard. I think the starboard bank starts the genny.

Future plans call for the genny to get it's own battery.

After that, A dedicated house bank powering an invertor.

HeLp!!!! I don't know squat about chargers!

 

[Boatsb]

We are moving along with the final work before leaving the yard and the PO installed the battery charger incorrectly and it fried.

Yard says we need a 100 amp 4 leg charger.

We have 4 8D's 2 port and 2 starboard. I think the starboard bank starts the genny.

Future plans call for the genny to get it's own battery.

After that, A dedicated house bank powering an invertor.

HeLp!!!! I don't know squat about chargers!

why only 100. Keep going maybe a 200.

 

[Boatsb]

Ok I feel better.


depending on how you use the systems a 2 or 3 bank charger , between 40 and 60 amps should be fine. I have a 30 on my convertible and have no troubles. We have a separate genny battery and no major 12 volt draws. Just pumps, freshwater, a head and a few lights.

Just sold and installed bunch of the pro nautics in the last few months and all seem fine.

 

[rwappleton]

I am glad you do!

We spend most of the time plugged into shore power. Very little 12 volt draw that I know of. And when we are out and about the genny is running most of the time.

what does each "bank" of the charger do? (hey I admitted it in the first post)

 

[jim rosenthal]

You should be fine with a 40 amp charger. The yard may be trying to sell you more than you need.

You need a three-output charger, not four, unless you are planning another 12v battery for a windlass or something like that. You have two banks of 2 8Ds each, plus you are going to put in a dedicated genset starting battery, which is a good idea. That is three legs.

A good charger will divide up its charging output proportionate to the needs of each battery bank. Modern boats have a "house" bank and a "starting' bank, but older Hatteras yachts were not wired that way. So you have two banks of two 8Ds each, both of which probably handle both starting loads and house loads such as lights, pumps, heads, etc. It's possible that these loads can be assigned to different banks, to balance the amperage draw on the two banks.

I would suggest you get a good quality "smart" charger that puts out forty amps. I don't think you need more than that. I would also suggest that you avoid Xantrex products as their warranty backup isn't good. I've seen good chargers from Pro Mariner, Charles, Sentry, and others. You want a "smart" high-frequency charger which can be configured to different kinds of batteries, definitely.

Since all of your 8D batteries are going to be used for house loads, you should (IMHO) make sure your 8Ds are suitable for deep-cycle use. An ordinary starting battery will quickly be ruined and unusable if it is cycled down like a deep-cycle battery can be. Although deep-cycle batteries do not put out as much amperage for starting diesels as starting batteries do, with two 8Ds on each bank you will have enough amperage to start your engines, especially if you are in a warm area or you use block heaters. One 8D would probably start your engines just fine.

If you find you really love the boat and you are doing a lot of cruising and anchoring out, you might think later about having the boat rewired so that all the house loads are on the house bank and one starting bank starts both engines. I did this (I had it done, I am not competent to do it myself) with my boat and it has worked out very well. I have a small starting bank which cranks both engines and a much larger house bank that powers all the other loads, plus a separate starting battery for the generator set. If I did a lot of anchoring out, I would get an even larger house bank. One of the advantages of this setup is that if you run your house bank down, you can still start your engines and move the boat- and recharge your house bank.

 

[SeaEric]

If the 43 DC is similar to my (older) 41 TC, The "house" source may be selected with a battery switch at the main panel. No re-wire required. Engines start with their respective battery bank and may be momentarily paralleled from the helm if one bank or the other is weak (or its really cold outside, or the block heaters forgot to plug themselves in....)

I have added a stand-alone Generator starting battery (when I replaced the Gen) but I left in place the option for starting the Gen from the starboard bank.

 

[mdshore]

i just went through this, called my friends at pro mariner . said I need a 60 amp for the 2 bank 2 8d confiig otherwise it will strain the charger and shorten life of it and possibly the life of the batteries. I had a 1230 p , I just bought the 1260p pro nautic .

 

[Boatsb]

i just went through this, called my friends at pro mariner . said I need a 60 amp for the 2 bank 2 8d confiig otherwise it will strain the charger and shorten life of it and possibly the life of the batteries. I had a 1230 p , I just bought the 1260p pro nautic .

I would have to question the amp draw on the bank. Low draw would not have a significant effect on the charger unless the batteries were low.

I usually match the charger to the use not the total banks rating. If the boat always has ac power it should not stress the charger unless there is a huge discharge .

 

[mdshore]

pulled off of a site, seems logical.

What size battery charger or alternator do I need ? I hear so many different things I don't really know what size to buy ?

This question crops up often. Salesmen usually reply with something along the lines of "10 percent of the battery capacity" or "15 percent of the battery capacity". An engineer will either ask you a LOT of questions about your installation and useage requirements or explain to you the effects of charging at different rates then let you make the decision.

The fact is that the size of charger required depends upon too many variables for there to exist a simple rule of thumb such as "10 percent of the battery capacity".

I offer the following by way of explanation:-

Let's look at 2 extremes of battery charger size in relation to battery capacity and see what we get........

In both these cases we will be considering a wet cell deep cycle battery and a real 3 stage smart charger. It doesn't matter whether that is an AC mains powered charger or an alternator with a true 3 stage controller. For our purposes here it makes no difference.

The first thing to remember is that batteries are "consumable" items. They do not last forever. Each time a battery is charged or discharged it shortens it's life. The harder it is charged or discharged the more the life is shortened. There exists a certain folklore that "batteries need to be worked". It is total rubbish. The more a battery is used the shorter it's life will be. The less it is used, the longer it's life will be.

The only exception to this rule is that batteries should NOT be regularly discharged by only a few percent. Discharging a battery by less than 5% can shorten it's life and limit it's ability to deliver high currents. This is due to the way the sulphate builds up on the plates which is very irregular during the first stage of the discharge cycle. Either don't discharge the battery at all, or ensure it is always discharged by more than 5%. This is not a particularly well known phenomenon (except by the battery manufacturers) and could be the genesis of the urban folklore/myth of "the batteries need to be worked".

Example 1 A 100 Ah battery with a 1 amp charger.

Assuming the battery has been discharged by 50% we have to replace 50 Ahrs. On the face it this will take 50 hours but it's not that simple. Generally (all other things being equal) we need to add 40% to this figure (this is because, as the battery becomes more fully charged it will accept less and less charge current) so this will give us a recharge time of 70 hours. Now in some installations this may be acceptable. In others (certainly on my liveaboard) it would be totally out of the question.

2 points to note here.

1. This battery would have a good long life. It is being "gently" treated.

2. Because the battery was very slowly charged it would have a genuine, good charge. It really would be 100% charged (see below for counter example and explanation).

Example 2 A 100 Ah battery with a 100 amp charger.

Again assuming the battery has been discharged to 50% we have to replace 50 Ahrs. For the same reasoning as given above this will take 42 minutes. "Wonderful" everyone thinks, such a quick recharge time.

There are 2 serious problems with this fast recharge cycle. Firstly, due to what is known as "surface charge" this battery will not actually be fully charged. The charge rate would have reduced considerably during first 15 minutes or so. This is because at such a high (and therefore fast) charge rate the charge (which remember is actually a chemical reaction between the acid and the lead plates) would not have been able to penetrate deep into the lead plates. The only parts fully charged would be on the surface of the plates, hence the term "surface charge". Once the charger was disconnected there would be some balancing of this charge due to internal chemical reactions within the battery resulting in the surfaces of the plates and deep within the plates becoming equally charged, at considerably less than a fully charged state.

Secondly and perhaps more importantly, this battery was very heavily charged, this causes severe stresses within the battery which SERIOUSLY shorten it's life.

Somewhere in between these two extreme examples is the typical battery/charger combination.

You can clearly see that a small charger (in relation to the battery capacity) has the benefits that it.....

A) Treats the battery "gently" thereby resulting in a long battery life.

B) Ensures the battery is indeed fully charged and not simply "surface charged"

It has the disadvantage that it takes an awful long time to recharge the batteries.

A large charger (in relation to the battery capacity) has the benefit that it.....

A) Recharges the batteries quickly.

It has the disadvantages that it......

A) Doesn't ensure a genuine 100% charge due to surface charge effects.

B) Severely shortens the life of the battery.

Finally, let's assume someone did actually fit a charger of, say, "10 percent of the battery capacity" because a salesman told him that was what he needed. This owner has a 200 amp hour battery bank. He now has a 20 amp charger. What about the fact that he has almost permanent loads of 25 amps on the batteries? The charger will not even keep up with the demand of the loads let alone charge the batteries.

From the above I hope it is very clear that for someone to state "you need a charger with 10% (or some other figure apparently plucked out of thin air) of the capacity of the battery bank" simply shows a total lack of understanding of battery charging and DC power systems.

The fact is you have to weigh up various different aspects such as required charge time, expected battery life, insistence on obtaining a full charge, average loads during charging etc etc etc.

There are no hard and fast rules on finding a suitable compromise but experience does indicate the following (very) general results.....

Users with a charger of 10% or less of the battery capacity generally complain of excessively long recharge times. Their batteries do however last a long time.

We have experienced many users with battery chargers of around 100 to 150% of the battery capacity. They gloat at their quick recharge times. They also continually complain that "batteries these days are rubbish and don't last 10 minutes"

Users with chargers of around 25% to 30% of the battery capacity tend to seem reasonably happy with the compromise they have of battery life versus recharge time.

Other users (myself included) tend to go slightly higher than this and generally run a charger between 35% to 50% of the battery capacity, enjoy the slightly shorter recharge times, but accept the (again) slightly shorter battery life.

Deciding on the required charger size is a series of compromises. Until there is a drastic breakthrough in battery technology this will remain the case.

Draw your own conclusions.

Addendum

During the last few years AGM (Absorbed Glass Matt, a type of VRLA [Valve Regulated Lead Acid]) batteries have become freely available outside the rather expensive markets they were previously seen in. The same rules apply as above but in the case of these batteries much higher charge rates can be tolerated and sustained. Note that this is the charge current. Excessive charge voltage will damage these batteries very quickly indeed. They are very intolerant of high charge voltages (with the exception of Optima Spiral AGM batteries which can tolerate higher charge voltages).

And as we've said elsewhere, like most things, battery technology changes.

There are now two distinct type of VRLA batteries. In one type the only difference is that the electrolyte is held in a glass matt. This type usually use charging voltage similar to standard flooded wet cell batteries.

The other type has additional chemicals (the same as Gel cell batteries) that affect how the batteries perform and in particular the terminal voltage. It is typically around 0.2 volts higher than an equivalent flooded battery. This type often requires a lower charge voltage than the first type of VRLA mentioned above.

Check the battery manual for the correct charge voltages!



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[carolinacoast]

We have an outback 3232 and the extra battery life alone has justified the expense. Several owners here installed the same unit, long before me. We have the battery combiner/de=combiner setup FWIW.

Here is an old thread on the topic:

http://www.samsmarine.com/forums/showthread.php?6040-Outback-32V-Inverter-Charger