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Old 12-03-2018, 10:04   #1
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Upgrades Needed Along with Larger Battery Bank?

Most battery threads seem to be based on what type of battery to get. I have questions about pretty much everything but that, it seems.

I've decided to upgrade my battery bank and charger in our Hunter 380 and will likely go with something similar to this setup of 4 house + 1 starter battery. Hunter 380 Owner Modifications and Upgrades

I currently have a Guest 10 amp ChargePro and am looking to replace that with a 2000W charger/inverter. But I'm confused about what amp charger I "need"? Common options in that size inverter seem to be 50 or 100 amps. I don't have a generator so all away from shore power charging would be via running the engine while underway. This is leading me towards the 100 amp option, but is that overkill for a ~450 amp hour house bank? Will the long-term life of the house bank be affected by a higher charging amperage?

Next question is the alternator. I believe (need to confirm) my current alternator is 30 amps. Will I need to upgrade this to a higher output alternator if I want to get the benefit of the higher amperage charger? If so, do I match whatever the charger is (e.g., 50 or 100) or go with some other amperage?

Thanks in advance for the help!
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Old 12-03-2018, 10:56   #2
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Re: Upgrades Needed Along with Larger Battery Bank?

A lot depends on how you plan to use your boat. Lets assume you keep the boat in a marina with dock power and plan to weekend cruise it. The house bank of 4 T105's will have a maximum capacity of 450 amp-hrs at 12v, of which about 50% is useable. If you take 225 amp-hrs out of the bank, it will take 250 or more amp-hours to fully recharge it.

As you don't have a genset, the only time you can use the charger part of an inverter/charger is when you are plugged into dock power. If you got an inverter/charger which would charge at 50 amps AND you arrived will essentially depleted bank, your batteries would be nearly full after a night at the dock, say 12 hours. After an initial bulk charging period the battery charging rate is limited by the acceptance rate of the batteries, rather than the charging rate of the charger, so a 100 amp charger would get you closer to full batteries in the first few hours of dockpower, but not a whole lot closer after 12 hours. OTOH, 2000 Watt inverter/chargers with 100 amp capacity are not much more expensive than those with 50 amps.

The battery bank you are considering should be good enough for a 2 day cruise when the batteries are new and start full. If you want to stay out longer, the only way for you to charge underway or at anchor/mooring would be through the alternator, and you will probably want to minimize the time you are running the engine--it is a sailboat after all.

I would recommend a 100 amp alternator for you as the largest practical size before another sharp jump up in price to upgrade mounts and belts. If you sailed all day and anchored overnight, you might draw the batteries down by 70-100 amp hrs per day, assuming you have 12v refrigeration. Running 24 hours might draw 150 amp-hrs. Replacing that energy on a daily basis for more extended cruising would require running the engine 6-10 hours per day with your current alternator, as not all 30 amps are available when the alternator heats up, and some current is used for the house loads. With the 100 amp alternator and a smart regulator you can replace your daily energy use in 2-3 hours of motoring, with the caveat that operating at a partial state of charge over extended periods does reduce your battery bank life.
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Old 12-03-2018, 12:14   #3
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Re: Upgrades Needed Along with Larger Battery Bank?

This is super helpful and makes a a lot of sense. Thank you!

One question I forgot to ask:

I have one large AGM house battery now. If I switch to flooded golf cart batteries, my understanding is they need to be vented somehow. I doubt my current settee is vented due to always having an AGM. How do I go about venting that area to prevent vapor buildup?
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Old 12-03-2018, 12:55   #4
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Re: Upgrades Needed Along with Larger Battery Bank?

Don's response is spot on!

Venting batteries. Actually all lead acid batteries require venting. AGMs and GELs don't gas as much as flooded lead acid batteries but they do gas.

That said, why are you considering going back to FLA batteries? AGMs generally have a higher charge acceptance rate (CAR) and require no maintenance. Take a look at Full River DC-250-6 batteries. They are 6VDC golf cart batteries with a 20hr rate of 250Ahr. In my area, they sell for about $200/each with a 1250 cycle life when discharged to 50% per cycle.
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Old 12-03-2018, 19:20   #5
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Re: Upgrades Needed Along with Larger Battery Bank?

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Don's response is spot on!

Venting batteries. Actually all lead acid batteries require venting. AGMs and GELs don't gas as much as flooded lead acid batteries but they do gas.

That said, why are you considering going back to FLA batteries? AGMs generally have a higher charge acceptance rate (CAR) and require no maintenance. Take a look at Full River DC-250-6 batteries. They are 6VDC golf cart batteries with a 20hr rate of 250Ahr. In my area, they sell for about $200/each with a 1250 cycle life when discharged to 50% per cycle.
Mostly the cost difference and FLA seemed like the more popular option for people who had done a lot more research than me. I could definitely still be swayed. Any idea how I could check into current venting or lack thereof? I have never noticed an issue with any weird smell from offgassing, but safety first and all that.
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Old 12-03-2018, 19:23   #6
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Re: Upgrades Needed Along with Larger Battery Bank?

you don't really have charger options. a 2000w inverter will normally be around a 100a charger.

a 1000w inverter will likely be a 50a charger.

pick the brand and size of interter you want. and you'll end up with whatever charger size it comes with. you won't have a choice of charger.

there is really no such thing as too big a charger.
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Old 13-03-2018, 08:33   #7
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Re: Upgrades Needed Along with Larger Battery Bank?

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Originally Posted by CharlieJ View Post
Don's response is spot on!

Venting batteries. Actually all lead acid batteries require venting. AGMs and GELs don't gas as much as flooded lead acid batteries but they do gas.

That said, why are you considering going back to FLA batteries? AGMs generally have a higher charge acceptance rate (CAR) and require no maintenance. Take a look at Full River DC-250-6 batteries. They are 6VDC golf cart batteries with a 20hr rate of 250Ahr. In my area, they sell for about $200/each with a 1250 cycle life when discharged to 50% per cycle.
Where do you get Full river 250-6 for $200.? best price I can find is $310.00
Thanks
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Old 13-03-2018, 09:17   #8
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Re: Upgrades Needed Along with Larger Battery Bank?

Have you considered adding solar? Cost is a fraction of what it was a decade ago.

Your charger can be larger than the battery bank requires but it must be a smart charger. Then it will track the battery voltage and charge accordingly. Most marine grade chargers today are "smart" chargers.

IMO Flooded lead acid batteries are best because they can take some abuse. AGM and Gel batteries will quickly die if overcharged. I have been using T-105's forever.

A 30 amp alternator will barely cover the loads when the engine is running - you definitely need higher output. About 25% of your battery bank capacity is about right.
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Old 13-03-2018, 09:53   #9
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Re: Upgrades Needed Along with Larger Battery Bank?

Flooded lead acid (FLA) batteries are still the least expensive on a cost per amp-hour (a/h) basis, and if you have good access and you're willing to maintain them by checking/adding water regularly, they are a good choice. FLA batteries should generally be charged at a rate of about 20-25% of the bank's capacity. That means a 100 amp alternator (or charger) is a good fit for a 450 a/h bank. To size the bank, determine your total daily energy needs and then size the bank so that you never discharge below 50%. Also, remember that once your state of charge reaches about 85% of the bank's capacity, charging the last 15% takes a very long time and generally isn't cost effective. For that reason, we figure we're only going to realistically be able to use 35% of the bank's capacity so we size the bank accordingly. We sailed a 42' ketch in the Caribbean for 6 years with no generator and a battery bank of 4 golf cart batteries. Charging was via a 100 amp alternator which we ran 45 min. in the AM and 45 min in the PM. (We had engine driven refrigeration, so while we were pulling down the cold plates we were also making amps and weren't relying on batteries for refrigeration.) We were very satisfied with the system and never worried about our electrical usage.
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Old 13-03-2018, 12:54   #10
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Re: Upgrades Needed Along with Larger Battery Bank?

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Originally Posted by nickfox45 View Post
This is super helpful and makes a a lot of sense. Thank you!

One question I forgot to ask:

I have one large AGM house battery now. If I switch to flooded golf cart batteries, my understanding is they need to be vented somehow. I doubt my current settee is vented due to always having an AGM. How do I go about venting that area to prevent vapor buildup?
The hydrogen gas that is generated during the latter stages of battery charging is very buoyant and diffuses very quickly. You have to work pretty hard to collect and retrain that gas enough to cause an explosion, especially if you are using a constant voltage charging source where the current tapers off as the battery gets charged. I personally think the venting requirements are more directed at regulators which have gone haywire and are pumping full alternator current into a full battery.

The gas is going to want to rise, so don't seal off the top of any battery box. My guess is that a couple of square inches of vent is more than adequate if distributed around the top of the box. If you worry about it, the water miser caps will cut down the hydrogen released.

Full disclosure--while I worked on the Fukushima reactor design, I did not do the hydrogen recombiner system
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Old 13-03-2018, 12:56   #11
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Re: Upgrades Needed Along with Larger Battery Bank?

Another good thread (not quite what the OP asked, but definitely related) to ask my question that no one answered last time: With the availability and efficiency of compact and low cost quick start batteries, why is a separate starter battery needed at all? If you screw up (or something fails) and you exhaust all your available amps you no longer need a separately maintained starter battery (at least in my opinion). The former starter battery can become a part of your "house bank" (probably change its specs) and add its amps to the reserve.

I still had a starter battery on my last boat, but I also took along a small jump start battery. The thing could be used to jump start an engine several times if needed (it worked fine for my car, but I never actually used it on the boat), would quickly recharge, and also had a USB port for charging such things a phones, as well as a bright LED flashlight. It cost under (US)$50, and I still have it in a car.
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Old 13-03-2018, 13:09   #12
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Re: Upgrades Needed Along with Larger Battery Bank?

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Originally Posted by buzzstar View Post
Another good thread (not quite what the OP asked, but definitely related) to ask my question that no one answered last time: With the availability and efficiency of compact and low cost quick start batteries, why is a separate starter battery needed at all? If you screw up (or something fails) and you exhaust all your available amps you no longer need a separately maintained starter battery (at least in my opinion). The former starter battery can become a part of your "house bank" (probably change its specs) and add its amps to the reserve.

I still had a starter battery on my last boat, but I also took along a small jump start battery. The thing could be used to jump start an engine several times if needed (it worked fine for my car, but I never actually used it on the boat), would quickly recharge, and also had a USB port for charging such things a phones, as well as a bright LED flashlight. It cost under (US)$50, and I still have it in a car.
A bit off topic, but a good point. The only downside to the book sized jumpstart batteries is that you need to top them up every month or two due to self discharge. I put one in my backpack when I sailed on a friends Catalina 30, and it saved us a Seatow call. I'm thinking of getting them for the YC boats I run.
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Old 13-03-2018, 21:24   #13
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Re: Upgrades Needed Along with Larger Battery Bank?

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Originally Posted by buzzstar View Post
Another good thread (not quite what the OP asked, but definitely related) to ask my question that no one answered last time: With the availability and efficiency of compact and low cost quick start batteries, why is a separate starter battery needed at all? If you screw up (or something fails) and you exhaust all your available amps you no longer need a separately maintained starter battery (at least in my opinion). The former starter battery can become a part of your "house bank" (probably change its specs) and add its amps to the reserve.

I still had a starter battery on my last boat, but I also took along a small jump start battery. The thing could be used to jump start an engine several times if needed (it worked fine for my car, but I never actually used it on the boat), would quickly recharge, and also had a USB port for charging such things a phones, as well as a bright LED flashlight. It cost under (US)$50, and I still have it in a car.

I'm still betting those things would be useless on a discharged house bank. it would be an interesting test.

IE if your only bank was a 800ah golf cart house bank. that you normally st art the engine with. and you drained it down to 8v by mistake. and you stuck a little booster on it. do you really think it will do anything? maybe raise it to 8.5v if you are lucky. I doubt it is going to start an engine.

vrs a single car group 27 at 8v. the booster would actully do something and raise the voltage. much easier to raise voltage on a car battery then the 800ah bank that would just suck it all up.

if in the first case. you'd probably have to dissconnet a bunch of batteries. and leave only 2 golf carts connected. then boost that. maybe that would work. then reconnect others once engine was started...
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Old 13-03-2018, 23:02   #14
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Re: Upgrades Needed Along with Larger Battery Bank?

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I'm still betting those things would be useless on a discharged house bank. it would be an interesting test.

IE if your only bank was a 800ah golf cart house bank. that you normally st art the engine with. and you drained it down to 8v by mistake. and you stuck a little booster on it. do you really think it will do anything? maybe raise it to 8.5v if you are lucky. I doubt it is going to start an engine.

vrs a single car group 27 at 8v. the booster would actully do something and raise the voltage. much easier to raise voltage on a car battery then the 800ah bank that would just suck it all up.

if in the first case. you'd probably have to dissconnet a bunch of batteries. and leave only 2 golf carts connected. then boost that. maybe that would work. then reconnect others once engine was started...
I do not know. that is why I asked. One thing though is I do think (but again do not know) they operate by charging the dead battery, just by getting a slug of juice to the starter. Maybe someone can answer with knowledge, and not opine. Thanks
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Old 14-03-2018, 06:22   #15
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Re: Upgrades Needed Along with Larger Battery Bank?

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I have one large AGM house battery now. If I switch to flooded golf cart batteries, my understanding is they need to be vented somehow. I doubt my current settee is vented due to always having an AGM. How do I go about venting that area to prevent vapor buildup?
6V golf cart AGMs exist; Lifeline, for example.

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