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Old 12-07-2017, 19:25   #1
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It's 2017! Can we talk about batteries, setup, etc?

I've been thinking about my upcoming boat and electrics, but most of the older threads are out of date.

2001 Hunter 340.

So here's what I'm thinkin'...

Boat has starting and 1 house battery. I expect to keep the starter, since it's newish.

Getting 400w solar. 2 controllers for 2 sets, parallel.

What would you recommend for a house battery bank? I do have AC, but won't care if it's not working. Have a fridge unit, but mostly it's just a few boat electronics, a laptop and a monitor (tv, lcd, low volts). Should I keep it as a 12v boat?

Thoughts? Cost and replacement are considerations, trying to keep it on the reasonable side.

Cheers!
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Old 12-07-2017, 21:05   #2
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Re: It's 2017! Can we talk about batteries, setup, etc?

Yeh, why not talk about it again. It only comes up about 3 times every year


That size - yes keep it at 12V.

Do an energy budget and work out how many Ah you will use during the day and overnight when sailing and when anchored/moored.

How often/how long are you away from "home base"?

How much time sailing v anchored/moored. Do you do night passages?

Do you have shore power when at "home base"?

Without that info, no one can give you any real recommendation.
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Old 13-07-2017, 06:09   #3
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Re: It's 2017! Can we talk about batteries, setup, etc?

StuM, you must have missed the other 1/2 dozen.
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Old 13-07-2017, 06:28   #4
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Re: It's 2017! Can we talk about batteries, setup, etc?

Have you managed okay on the two batteries to date?

400w of solar plus S/S frame, plus controllers and wiring will be north of $1000.

So do you really need that much, without working out your needs first as Stu has suggested you could be throwing money away needlessly.

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Old 13-07-2017, 06:48   #5
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Re: It's 2017! Can we talk about batteries, setup, etc?

I have 5 group 31's with a 450W solar array, a 30amp Mppt charge controller and a 3000 Watt inverter. We typically run our 7k btu ac off of it all night as well as a our norcold fridge and our 12v accessories (lights, fresh water pump ECT.) We have a kid so we don't typically stay up late so there lights aren't on late ECT. And we are a power boat so our electronics gps, spotlights, ECT are on a separate bank that is charged by the motor, but can be charged by the solar bank if necessary. We don't recoup our nightly use over the course of a day though, especially if it's cloudy. Every third night we will usually need to skip the A/c to let the solar catch up. But our typical trip is a 3 day weekend so it works. We did 10 days on the hook a few weeks ago and only skipped the a/c one night, but that was up in the Chesapeake which was a bit cooler than the Florida waters we are used to so the ac didn't run as much.
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Old 13-07-2017, 07:54   #6
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Re: It's 2017! Can we talk about batteries, setup, etc?

Quote:
Originally Posted by Pete7 View Post
Have you managed okay on the two batteries to date?

400w of solar plus S/S frame, plus controllers and wiring will be north of $1000.

So do you really need that much, without working out your needs first as Stu has suggested you could be throwing money away needlessly.

Pete
Thank you for the input.

"Upcoming" boat. In the purchasing stage, can't do any testing yet to find out how much of a pig the ac and fridge are. I expect the majority of my use to be from those two things.

Yes, I'm going for overkill with the 4x100w panels. I'd rather spend it now than be cranky when I don't have enough. Found a good deal on panels, so that's already done.

I guess what I really wanted to know is, are AGM 31's still the way to go? Would 2 be enough? The current storage location for the battery isn't that big, so is there a better choice?

Just spitballin' here....
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Old 13-07-2017, 09:10   #7
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Re: It's 2017! Can we talk about batteries, setup, etc?

Quote:
Originally Posted by StuM View Post
Yeh, why not talk about it again. It only comes up about 3 times every year


That size - yes keep it at 12V.

Do an energy budget and work out how many Ah you will use during the day and overnight when sailing and when anchored/moored.

How often/how long are you away from "home base"?

How much time sailing v anchored/moored. Do you do night passages?

Do you have shore power when at "home base"?

Without that info, no one can give you any real recommendation.
What he said. Begin with an energy budget for 12 V DC demand. That will let you decide on size of house battery bank, then you can think about charging issues. Note, you must consider all 12 V demands, lights, autopilot, refrigerator, computer. etc.
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Old 13-07-2017, 09:12   #8
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Re: It's 2017! Can we talk about batteries, setup, etc?

Quote:
Originally Posted by fSymo View Post
Thank you for the input.

how much of a pig the ac and fridge are. I expect the majority of my use to be from those two things.

Yes, I'm going for overkill with the 4x100w panels.

I guess what I really wanted to know is, are AGM 31's still the way to go? Would 2 be enough? The current storage location for the battery isn't that big, so is there a better choice?

Just spitballin' here....
If you want to run your AC, you're way off base with two group 31's and 400 watts of solar.
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Old 13-07-2017, 09:23   #9
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Re: It's 2017! Can we talk about batteries, setup, etc?

Quote:
Originally Posted by fSymo View Post
.............stage, can't do any testing yet to find out how much of a pig the ac and fridge are. I expect the majority of my use to be from those two things. >>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>

I guess what I really wanted to know is, are AGM 31's still the way to go? Would 2 be enough? The current storage location for the battery isn't that big, so is there a better choice?>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
Sure you can. A "fridge" normally uses 60 ah per day. This has been an industry standard for the 45 years I've been boating. You don't run AC off batteries, you get a generator (in general - otherwise a huge battery bank off an inverter).

Oh, finally your real question. AGMs have their limitations. Quantity question already answered, we don't know enough about your energy budget to know.

Here's an idea: buy a boat electrical book, would answer a lot of your questions; do a search on AGMs or read the electrical section topics here it comes up often; read this: Electrical Systems 101 Electrical Systems 101


Good luck, but planning is better.
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Old 13-07-2017, 11:08   #10
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Re: It's 2017! Can we talk about batteries, setup, etc?

Quote:
Originally Posted by fSymo View Post
Thank you for the input.

"Upcoming" boat. In the purchasing stage, can't do any testing yet to find out how much of a pig the ac and fridge are. I expect the majority of my use to be from those two things.

Yes, I'm going for overkill with the 4x100w panels. I'd rather spend it now than be cranky when I don't have enough. Found a good deal on panels, so that's already done.

I guess what I really wanted to know is, are AGM 31's still the way to go? Would 2 be enough? The current storage location for the battery isn't that big, so is there a better choice?

Just spitballin' here....
I suspect your refrigerator and AC will suck amps much faster than you can replace them without a generator or running your engine. More importantly to survive the night and maybe a cloudy day I suspect 4 group 31's will still be too little. Cannot be more specific but I would estimate my amperage draw over 36 hours and size my house bank to double that
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Old 13-07-2017, 11:20   #11
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Re: It's 2017! Can we talk about batteries, setup, etc?

Skip the AGMs and use FLA golf cart batteries, more amp hours for the dollar.
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Old 13-07-2017, 11:48   #12
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Re: It's 2017! Can we talk about batteries, setup, etc?

Quote:
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You don't run AC off batteries, you get a generator (in general - otherwise a huge battery bank off an inverter).
:
I do... no you cannot run it 24 hours a day, but we run it for 9-10 hours a night. the OP's boat should have a similarly sized a/c and should be possible to follow the same setup. The a/c is not running a 100% duty cycle, unless you really wanted to be cold. But to keep it at a comfortable level during the night, 5 group 31's work for me.
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Old 13-07-2017, 13:10   #13
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Re: It's 2017! Can we talk about batteries, setup, etc?

I take that back. I thought the op was looking at a 25 footer for some reason. I just noticed it was a 340. Yes that would take considerably more power to run an ac for that. I'm sure it's still possible but I'd be willing to bet he's going to need double my setup.
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Old 14-07-2017, 03:47   #14
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Re: It's 2017! Can we talk about batteries, setup, etc?

Forget air conditioning on batteries. It is possible in theory, in practice you'll need more batteries and charging than you could economically and feasibly put on a 34' boat.

The fridge will otherwise be the biggest draw unless you're using an electric autopilot. Add normal lighting, electronics, stereo, charging laptops and phones, etc a typical cruiser will have a min of 400 amp hours worth of house batteries, many go for 600.

AGMs vs regular FLA (flooded lead acid batteries) there's probably a gazillion threads on this. In short

AGMs
- Will accept a faster bulk charge (IF you have the charging capacity to feed them) BUT once you get to absorption will charge at about the same rate as a FLA so the total time to reach 95-100% charge is not that much shorter than a FLA.
- Can be mounted sideways if you need to fit a space.
- Are much more expensive
- pretty much maintenance free.
- Are much more sensitive to abuse than FLA. To avoid early death you really should fully charge them frequently, often difficult when cruising.

My opinion, the most bang for the buck is a set of 6V golf cart batteries in series/parallel.
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Old 14-07-2017, 04:21   #15
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Re: It's 2017! Can we talk about batteries, setup, etc?

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What would you recommend for a house battery bank? 400-500 amp-hr I do have AC, but won't care if it's not working.you will if you come south where it is 85 degrees in the mornings, your boat isn't big enough for the amount of batteries needed,
you have to have a generator or stay in a slip
Have a fridge unit, but mostly it's just a few boat electronics, a laptop and a monitor (tv, lcd, low volts). Should I keep it as a 12v boat? absolutely!!!!

Thoughts? Cost and replacement are considerations, trying to keep it on the reasonable side.

Cheers!
400W solar for a weekend boat is fine and even more than needed. If you are going to live aboard and not be plugged in you are going to need 600W so so if you aren't going to charge every other day with something else.
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