Battery Tenders

[varkpilot]

I've been away from large boats for quite a while and have a question about battery charging. My new (to me) Chris Craft 47 Commander has 6 batteries. All appears to be well and I'd like to keep it that way. On my experimental airplane, I have a 12 volt system which I keep connected to a little battery tender. It keeps the battery at 14.3 volts no matter how much time passes between flying days. I was wondering if the same sort of thing might work on the boat. Probably have to have more than one, but the little tenders are cheap enough to put one on each battery set that is paralleled, without bankrupting me. Any of you good folks have any experience with these? Thanks.

Ray

[a64pilot]

Battery tender won't work.
First there is a ground issue with any automotive type of chargers that could cause an issue with your underwater metals.
Second there is just not enough amperage to do the job, but an good marine battery charger will go into float once the batteries are charged and that is what a battery tender does.
If your boat Charger is like mine was and is either off or on without any temperature compensation, charge voltage can't be adjusted and has three stages of charging, plan on replacing it.
Or just plan on changing your batteries every couple of years, if you go this route, Walmart batteries are as good as anything else and are significantly less expensive

[varkpilot]

Originally Posted by a64pilot

Battery tender won't work.
First there is a ground issue with any automotive type of chargers that could cause an issue with your underwater metals.
Second there is just not enough amperage to do the job, but an good marine battery charger will go into float once the batteries are charged and that is what a battery tender does.
If your boat Charger is like mine was and is either off or on without any temperature compensation, charge voltage can't be adjusted and has three stages of charging, plan on replacing it.
Or just plan on changing your batteries every couple of years, if you go this route, Walmart batteries are as good as anything else and are significantly less expensive

Appreciate your comments, a64. I'm still in a learning curve that's straight up right now, so your input is most welcome. Been quite a few years since I had one of the bigger boats, and all the new whistles and bells are fascinating to read about. Maybe I'll even be able to afford some of them one of these days. You don't happen to know anyone looking for an experimental, all-metal, low wing plane , do you? I've pretty much hung up my flight suit.

[SteveInMD]

If you are always plugged into shore power or running your motors you do not need a very big marine battery charger. However it needs to be big enough to at least keep up with 12 volt power usage while plugged in to shore power. You could turn on every 12 volt system you might use at the dock and measure the amps being used, and then round up to the next size charger. However you will probably find that chargers are not prohibitively expensive and there is not much downside to having a fairly powerful unit. Sailboats often show up at a dock with less than a full charge and want a charger that will charge at a rate close to the max rate the batteries will accept, but this is usually not necessary on a power boat.

All decent modern chargers will charge in a bulk, acceptance, and float voltage sequence and are switchable from flooded, gel, and AGM modes. The three phases require different voltages for different types of batteries. And some chargers will also adjust voltages based on battery temperature as well.

If you want to have 120 volt AC power while away from the dock you can install a inverter/charger.

Typically, float voltage for flooded lead acid batteries is around 13.5 to 13.8 volts. I'm guessing your airplane does not have flooded lead acid batteries, but if it does, make sure someone checks the electrolyte levels frequently if the float voltage is that high!

Batteries are a complex subject. There is a ton of reading you can do on the subject.

[ranger58sb]

Vark, you might read threads here about charging batteries... to get an idea about sizes, brands, features, etc. Trawlerforum.com (sister site) is another good resource for your style of boat.

Then be aware that some brands/models of 3- or 4-stage smart chargers actually sell for about 60% or MSRP... so don't let yourself be frightened off by cost. The system is charger, batteries, wiring... etc... so remember the cost of killing batteries with an inadequate charging system is another potential factor.

-Chris

[varkpilot]

Originally Posted by SteveInMD

If you are always plugged into shore power or running your motors you do not need a very big marine battery charger. However it needs to be big enough to at least keep up with 12 volt power usage while plugged in to shore power. You could turn on every 12 volt system you might use at the dock and measure the amps being used, and then round up to the next size charger. However you will probably find that chargers are not prohibitively expensive and there is not much downside to having a fairly powerful unit. Sailboats often show up at a dock with less than a full charge and want a charger that will charge at a rate close to the max rate the batteries will accept, but this is usually not necessary on a power boat.

All decent modern chargers will charge in a bulk, acceptance, and float voltage sequence and are switchable from flooded, gel, and AGM modes. The three phases require different voltages for different types of batteries. And some chargers will also adjust voltages based on battery temperature as well.

If you want to have 120 volt AC power while away from the dock you can install a inverter/charger.

Typically, float voltage for flooded lead acid batteries is around 13.5 to 13.8 volts. I'm guessing your airplane does not have flooded lead acid batteries, but if it does, make sure someone checks the electrolyte levels frequently if the float voltage is that high!

Batteries are a complex subject. There is a ton of reading you can do on the subject.

Checking the amperage drain is a great idea. An Ampclamp ought to work, as all the battery wires are in the open. I do have the alternators on both engines and an inverter already installed on the boat. Also have a genset, 13.5 kw I think, for anchoring. I just have to spend some time in the engine room.

On my little plane, the alternator also produces about 14.3 while in flight. I have a full-time voltage meter on the panel. It is a lead/acid battery, sealed. Have to see if I can get a look at the cells or if it is truly sealed. Thanks.

[varkpilot]

Originally Posted by ranger42c

Vark, you might read threads here about charging batteries... to get an idea about sizes, brands, features, etc. Trawlerforum.com (sister site) is another good resource for your style of boat.

Then be aware that some brands/models of 3- or 4-stage smart chargers actually sell for about 60% or MSRP... so don't let yourself be frightened off by cost. The system is charger, batteries, wiring... etc... so remember the cost of killing batteries with an inadequate charging system is another potential factor.

-Chris

I've been to the Trawler forum. Initially I looked at it simply because of having the power boat. Those folks don't seem to be anywhere as near active as this forum, and since this one does have the power boat section, here I am. You also seem to have several pilots which is a definite plus for me (retired USAF fighter pilot).

I liked a64's comment about the Walmart batteries. Good to know you don't need the big-bucks type the marinas push. I'll see what the draw on the batteries is, then check the charging system. We'll get it right. I want to enjoy this thing, not spend my time pouring time and money into repairs. Thanks, Chris.

[SteveInMD]

If you plan to spend some time at anchor, unplugged from the dock and not under way, you may want to consider a larger charger. This will reduce the number of hours you will spend listening to your genset running while recharging.

Google up float voltages for lead acid batteries. 14.3 is fine while flying but I think you will see it is way too high for continuous float charging.

[Lepke]

If money is an issue, many brands are sold on sites like Amazon and Ebay for much less than many marine stores. Some OEMs sell direct on those sites.

[varkpilot]

Originally Posted by SteveInMD

If you plan to spend some time at anchor, unplugged from the dock and not under way, you may want to consider a larger charger. This will reduce the number of hours you will spend listening to your genset running while recharging.

Google up float voltages for lead acid batteries. 14.3 is fine while flying but I think you will see it is way too high for continuous float charging.

Okay, did the Google trick and see what you mean, Steve. Seems the experts are in two camps about float charging, at least to some degree. 13.6 volts seems to be accepted by most as nominal. That's from a quick read of several sites. I have a friend who owns U.S. Batteries, Steve Kay. I'll also check with him, see what he has to say on the subject. One more voice kind of thing. Since the plane has been sitting for a bit over two months without starting, I may have ruined the battery. Glorious. Leave it to me to hurriedly ruin things. I need that battery for air starts in case the engine dies for some reason. Never has, but who knows. The prop isn't big enough to spin the engine if it quits. Anyway, much to look at and test. Thanks for the heads up.

Ray

[varkpilot]

Originally Posted by Lepke

If money is an issue, many brands are sold on sites like Amazon and Ebay for much less than many marine stores. Some OEMs sell direct on those sites.

LOL. Being retired military, money is ALWAYS an issue. Ebay and I are old friends. Thanks, Lepke.

[SteveInMD]

I had a battery in my home standby generator explode due to a float voltage of 14.3 volts. What a mess!!!!! Once the electrolyte falls below the top of the plates you are at risk of this happening to you.. It took mine about 9 months at 14.3 to go boom.

If it has only been two months, and the battery is serviceable (not AGM, gel, or sealed) you are most likely okay just checking / properly topping it up. But that is your call given the mission critical nature of your application. If it is not serviceable I would think keeping it could be risky. Again, your call of course.

[a64pilot]

The Walmart comment was meant to mean if you don't spend bunches of money buying equipment to maintain an expensive bank, and or you live in a Marina and don't need a big house bank, don't pop for expensive batteries and their expensive support system.
Batteries are usually murdered, meaning they don't usually wear out, they usually die from abuse. Don't waste a whole lot of money on super duper batteries if your going to kill them, kill Walmart batteries for a whole lot less.
People that almost never plug into a Marina have to rely on their bank almost exclusively, often using Solar to charge it, and supplement with a generator.
These people are often the ones that spend lots of money, $ (thousands) to maintain a bank, and may spend thousands on that battery bank. If your not going to be one of them, then it may well be that all you need is the Walmart bank, not to spend excessive amounts of money and become anal about trying to make that expensive bank last as long as you can.
Before I bought this boat that we will cruise on, I just bought Walmart batteries every other year, and took the ones out of the boat and put them into the RV.
I never had a battery problem and never worried about them either.

[varkpilot]

Originally Posted by SteveInMD

I had a battery in my home standby generator explode due to a float voltage of 14.3 volts. What a mess!!!!! Once the electrolyte falls below the top of the plates you are at risk of this happening to you.. It took mine about 9 months at 14.3 to go boom.

If it has only been two months, and the battery is serviceable (not AGM, gel, or sealed) you are most likely okay just checking / properly topping it up. But that is your call given the mission critical nature of your application. If it is not serviceable I would think keeping it could be risky. Again, your call of course.

Wow, I bet that was a mess. This plane has the battery mounted behind my seat (single place design), so that would be really nice if it happened at, say, 5,000 ft. And now that I think about it, it's been a couple of years since I got that battery, so probably ought to replace it, anyway. Thanks, Steve. You might have just saved my old butt.

[a64pilot]

You sure you have a battery tender and not just a trickle charger?
I have one on my airplane too, and it has an absorption voltage of about 14.3, but then floats at about 13.2
http://www.batterytender.com/faq/products