Batteries and Battery Charger usage

Hi all,
For some background, I came from sailing with two group 24 marine batteries for starting and house.
My current boat, Jefferson 37 Sundeck had an 8d for each diesel and house, and a 4d for the generator.
I replaced the 4d with a group 31 in 2019 and also one of the 8ds with two group 27's in parallel. Last spring I replaced the other 8d with the same setup, two group 27's in parallel.
Only the 27's are used for the house as well as starting.
Normally I have the battery charger on at all times when at the dock. I check the water in the batteries, they are all lead acid.
Since the batteries are now smaller, I bring them home to put a trickle charge on the occasionally during the winter months as the boat is stored outside in Michigan.
When I went to check the 'generator battery/group 31' there was hardly any water in the battery. I topped it off and put it on the charger here at home.
Now my questions: Do people leave their charger on at all times when at home port? Lights and electric toilets and water pump all run off 12v.
With the Group 31 as it was, could my Battery Charger on my boat be overcharging the battery, i.e., not going into float mode for the one battery. I have no idea how old the charger is, it is a NewMar 3 bank, HDM50 charger.
I will check the battery here at home in a while and see if it is holding a charge, otherwise I'll bite the bullet and purchase another battery. Any insights would be most appreciated.
Thanks.

Sounds like your Gen battery was over charged. I use my boat very differently than you. I have a charger on at all times and systems running 24/7/365. I check water every 6 months. House goes through a lot of water. Start only batteries never need water and my Crane battery needs water once a year.

Here's part of a "my battery charger" post from 2017 on your HDM50 model:

"I have that exact charger in my garage. I use it occasionally on cars, lawnmowers, etc.
It is the old "ferroresonant" type, and has only the same charging characteristics as a car alternator, unlike the modern 3 stage "smart" chargers."

Seems like the sort of charger you wouldn't want to leave on 24/7. I'd get a new smarter one.

Len,
The HDM50 are older technology of a ferro-resonant type that usually produce more heat when compared to newer smart chargers (all digital tech). The biggest issue is it is not a 3-stage charger and will not float the batteries. In another word, it cannot completely charge the batteries, and should not be left on once the absorption stage has been completed.

Using a lot of water in the house bank is a hassle with some sort of smart , but nor really smart chargers.

The liveaboard DC loads get high enough to tell the charger the bat voltage is really low so the charger switches on with big amps and it goes thru a complete charge cycle . Heavy charging is heavy water use.

In the past the technique was 2 charging units.
A Constavolt would hold the DC voltage at a preset modest voltage 12.8 or 13.0 at up to 40 or 60amps ,,that kept all the house goodies happy , but took a week to charge a batt set.

A constant amperage charger would fill and condition (slight overcharge) a run down batt set.

Worked fine tho the small charger needed to be operated by the owner, it was not automatic.

One would hope 60 years of "improvements" would have created a truly smart charger .

I am looking at a 'Charles' 3 bank charger. I currently have two 'Charles' Isolation Transformers installed on the boat and do a great job. I was looking at another couple of chargers, but I would be able to utilize the same positive and negative leads to the battery banks. The other chargers came with short leads and I would have to purchase new 'lead sets'.
Another question I have. My currently installed 'Newmar', which I am sure is old does not have fuses installed in the positive lead to the batteries. I was looking at the installation manual for the 'Charles' and it requires a fuse, in the positive lead for each bank. Is this newer ABYC regs?
I was also looking at my 'Shumacher' charger that I use at home to 'top off' my batteries and that does not have a fuse in the positive for the clip. In addition, a friend of mine has a 'Leichester' charger. That also does not have a fuse in the positive lead for the clip, but for the other type of lead set, it does have a fuse. Any ideas why?

As I was researching Battery Chargers since my last post, I again looked at the Charles Battery charger, they are now either out of stock or discontinued, unless you are looking at one for about $2k.
I am now looking at the Xantrex Trucharge 2 40 amp 3 bank charger. I had a two bank Xantrex charger on my last boat, a sailboat and it worked flawlessly. They seem to have good reviews and look pretty easy to install.

The same question as before though: Unless my existing Newmar charger has fuses for each positive lead at the charger, most of the chargers I have been looking at require a fuse in the positive lead to each battery.
Any ideas why that is?

The wires should be fused at the battery in case of a short between the battery and charger (or inside the charger). Even though current normally flows to the battery, it could flow the other way in a fault situation. And the battery can easily supply enough to cause a wire meltdown.

Len,
As others have said and you have concluded, you need a new battery charger. Promariner makes some good ones as do Victron, Mastervolt, etc.
There is a lot to know about batteries, types, uses, recharging, best ways to obtain best "bang for the buck" etc. If you want to learn more, alot more, check out marinehowto.com. This website is run by a TF member who does marine electrical for a living and Rod is very knowledgeable and provides real world testing and years of experience to back up what he says. Fuses are an important safety feature, especially on a boat.
Most flooded lead acid batteries are murdered by their owners by not properly recharging them. Discharging them too deeply or letting the acid level fall to expose the lead plates, or not recharging them regularly to a 100% full charge will all contribute to their demise. In a perfect world, you would want to separate your house bank (duties) from your start batteries with your house bank being true deep cycle batteries (eg. golf cart batteries). All or most of recharging effort should then go to the house bank with start battery recharging being accomplished with either a separate (smaller) charger, an echo charger (the charge comes from the house bank), or using ACR's (automatic combining relays). There is a lot to learn and it can get a bit complicated as many factors may need to be considered. Good luck, and I hope some of this makes sense and helps.

Thanks to all of the responses. A lot to think about. Being up in Michigan, and it being only 7 F, right now, I have some time to decide on charger and how I'm splitting up my DC system.

LenBuchanan said:

Thanks to all of the responses. A lot to think about. Being up in Michigan, and it being only 7 F, right now, I have some time to decide on charger and how I'm splitting up my DC system.

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As Firehoser suggests do spend some time at Rod's site Marine How To. I think this article 1/2/Both Battery Switch Considerations is one you will find worth the effort to read and understand as you decide how to divide up your DC system.

THe fuses in the + leads from the charger to the battery are needed CLOSE to the battery because the battery is the most dangerous source of short circuit power in the event of a short between the battery and charger.

A battery, for a short time, can supply sometimes thousand of amps which can vapourize even what you think are large wires. I've not experienced it but have heard about battery explosions from uncontrolled shorts.

EDIT: I have had one explode but from a different cause. NOT FUN.

Most chargers will have their own built in fuse or C.B. to protect themselves.

Just a note. I have used the square block fuses from Blue Seas mounted right on the battery post, link below. I have 3 batteries for the house paralleled with a #4 wire running to a large buss bar. Each battery has a 100A fuse on the + post.
THese fuses are actually made by Littlefuse or Bussman or similar so if you cannot find the Blue Seas ones look up Littlefuse/Bussman.

https://www.bluesea.com/products/category/15/42/Fuses/Marine_Rated_Battery_Fuses

LenBuchanan said:

As I was researching Battery Chargers since my last post, I again looked at the Charles Battery charger, they are now either out of stock or discontinued, unless you are looking at one for about $2k.
I am now looking at the Xantrex Trucharge 2 40 amp 3 bank charger. I had a two bank Xantrex charger on my last boat, a sailboat and it worked flawlessly. They seem to have good reviews and look pretty easy to install.

The same question as before though: Unless my existing Newmar charger has fuses for each positive lead at the charger, most of the chargers I have been looking at require a fuse in the positive lead to each battery.
Any ideas why that is?

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ALL positive wires except the starter circuit need to have fuses appropriate to the size of the wire, as close to the battery as possible. Starter circuit is optional, larger engines would probably blow the fuse especially if battery voltage is low and the amperage goes up. Smaller engines like in a sailboat usually won't blow a fuse. My 21 HP Kubota starter is fused at 250 amps and has never blown it.

Check out Pacific Yacht Services Youtube channel, he's got about 150 videos explaining all of this stuff. https://www.youtube.com/user/PacificYachtSystems/videos

I feel your pain about the weather, my boats are in Muskegon and St Joe. Got about a hundred projects lined up, can't get to any of them right now.

There are other perfectly acceptable ways of arranging battery banks. For example, there are no battery disadvantages to having a house bank also serve to start propulsion engines. Doing so greatly simplifies wiring.

firehoser75 said:

Len,
As others have said and you have concluded, you need a new battery charger. Promariner makes some good ones as do Victron, Mastervolt, etc.
There is a lot to know about batteries, types, uses, recharging, best ways to obtain best "bang for the buck" etc. If you want to learn more, alot more, check out marinehowto.com. This website is run by a TF member who does marine electrical for a living and Rod is very knowledgeable and provides real world testing and years of experience to back up what he says. Fuses are an important safety feature, especially on a boat.
Most flooded lead acid batteries are murdered by their owners by not properly recharging them. Discharging them too deeply or letting the acid level fall to expose the lead plates, or not recharging them regularly to a 100% full charge will all contribute to their demise. In a perfect world, you would want to separate your house bank (duties) from your start batteries with your house bank being true deep cycle batteries (eg. golf cart batteries). All or most of recharging effort should then go to the house bank with start battery recharging being accomplished with either a separate (smaller) charger, an echo charger (the charge comes from the house bank), or using ACR's (automatic combining relays). There is a lot to learn and it can get a bit complicated as many factors may need to be considered. Good luck, and I hope some of this makes sense and helps.

Click to expand...

2 suggestions. Get a battery charger that monitors battery temperature and be sure you understand what the definition of multiple banks means for the particular charger you purchase. I have a Promariner that says it is a 3 bank charger. But, what that means is that it will charge 3 separate batteries, not 3 banks of batteries. I had some charging issues with it initially and found this out after re-reading the instructions and calling Promariner tech support.

Curious what Promariner told you. What's the difference between 3 separate batteries and 3 banks? Seems to me the charger would be seeing 3 separate loads, be they banks of batteries or single batteries.

TBill36 said:

2 suggestions. Get a battery charger that monitors battery temperature and be sure you understand what the definition of multiple banks means for the particular charger you purchase. I have a Promariner that says it is a 3 bank charger. But, what that means is that it will charge 3 separate batteries, not 3 banks of batteries. I had some charging issues with it initially and found this out after re-reading the instructions and calling Promariner tech support.

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They told me the leads had to go to individual batteries. It's been a long time, but don't think they explained why, just said that is the how they had to be hooked up. As I remember, the owners manual shows hooking up to individual batteries also.

My Promariner 3 bank charger is wired to the batty sel sw so bank vs individual battys.
On my motorhome the Magnum inverter / charger serves a bank of 8 - 6V AGM GC in series / parallel.
I dont think I've ever seen individual battys charged in large banks... of 6 or 8 GCs.
I would be more concerned with matching the charger to the batty / bank AH rating and the recommended charge rate of 0.1C or 0.2C

catalinajack said:

There are other perfectly acceptable ways of arranging battery banks. For example, there are no battery disadvantages to having a house bank also serve to start propulsion engines. Doing so greatly simplifies wiring.

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There are many ways to wire a boat, some better than others
I still stand by my statement, IN A PERFECT WORLD, having a separate start battery so a person does not inadvertently run down the one (combined) bank so low that now they cannot start the engine, is a good idea! Mandatory, no. Have people gone this route (a single bank) and "made it work", yes. Best practise, probably not.
To each his own.
Bacchus is correct, having a properly sized charging system is important as well.

I prefer separate start batteries. One per engine is ideal, but generators can share with engines no problem. It's a safer layout, as I consider starting power to be safety critical. And it avoids any voltage sensitive stuff potentially rebooting after an engine start causes a voltage dip.

I have always kept the generator battery separate and only connected to the genny and never on a battery charger. Never had an issue with a weak battery that would not fire the genny. Even after a winter of storage the genny would fire up.

jleonard said:

I have always kept the generator battery separate and only connected to the genny and never on a battery charger. Never had an issue with a weak battery that would not fire the genny. Even after a winter of storage the genny would fire up.

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That is pretty much what I have moved to.
The only exception is I changed out my gen batty on/odd switch to a 1-2-all- off and added a jumper to my house bank as an emergency only back up. Another TF Mainship owner recommended it and was simple as the switches had same footprint and bolt pattern.
It will also allow topping off the gen batty from either shore charger or alt underway if I havent run the gen in a long stretch and have any doubts.

I do not. Only a fool runs down their house/start bank to the point engines cannot be started. I have started my Lehmans with my batteries depleted to 20% with no perceived difference in starting strength quickness to start. My bank is 920ah. Even so, I can use my generator start batteries if need be.

rslifkin said:

I prefer separate start batteries. One per engine is ideal, but generators can share with engines no problem. It's a safer layout, as I consider starting power to be safety critical. And it avoids any voltage sensitive stuff potentially rebooting after an engine start causes a voltage dip.

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