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Old 29-11-2012, 17:11   #1
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One battery?

Hi all
I am near to launching my wharram tiki 26 in the not too distant future.I have yet to do the wiring and have found this forum immensely helpful but i have a problem that wiser heads may be able to help me with.

I want to run a the following;
Led nav light
garmin 300c fishsfinder
led cockpit lights
compass light
handheld gps
I have two 20 watt solar panels.


I was looking at having two 6v trojans initially and later as my financial embarrassment eases add another two with enough solar to help keep the battery bank charged.

what is a poor boy meant to do?

cheers paul.
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Old 29-11-2012, 17:16   #2
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Re: One battery?

Sounds like plenty of battery power for those items. You can save even more by buying a couple of Sam's Club golf cart batteries, which are the same as the ones sold at West but half the price. You may even want to switch to a couple of the WalMart marine 12-volts, which some people have had good results with. Doesn't look like you'll be doing much deep-cycling--you might get away with one.
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Old 29-11-2012, 18:15   #3
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Re: One battery?

Thanks mate for the reply, unfortunately I am on the east coast of oz so i reckon the Sams club and walmart are beyond reach as far as batteries go.So what i gather from your post is that the trojans may be overkill?
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Old 29-11-2012, 18:28   #4
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I don't know alternatives in your part of the world....but I like Trojans in the US and think they are worth the difference in cost. I would not switch to 12V batteries.
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Old 29-11-2012, 18:44   #5
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Re: One battery?

G'day Mate,
we have Trojan 105 and have been very pleased as compared with the D4 units we replaced. do it.
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Old 29-11-2012, 18:47   #6
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Re: One battery?

Yep, Trojans are good batteries. You really can't go wrong with them, though you could probably get away with less. It is always better to have more than enough battery capacity.
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Old 29-11-2012, 18:47   #7
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Re: One battery?

I'd stick with one large supply of 12v. The performance of your boat is contingent on being light so don't add any more weight than you absolutely need to. Batteries weigh a lot.
I'd start with one large deep cycle 12v battery.
Just my opinion of course.
kind regards,
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Old 29-11-2012, 18:59   #8
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Re: One battery?

you're loads are very light. with any decent sunshine i don't think you'll have any problem keeping the battery charged.

trojans are great batteries - mine lasted six years. but i replaced them with sams club batteries because they had gone up so high in price. the sams batteries have been working good for the past year and a half.

trojan also makes some excellent deep cycle batteries in 12 volt, so you might be able to save a few bucks by buying just one of those.

if i may suggest, you might make your first upgrade a larger solar panel, say 80 watts. you may be able to sell both the 20 watt panels to help pay for it...
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Old 29-11-2012, 20:05   #9
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Re: One battery?

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Originally Posted by salticrak View Post
I was looking at having two 6v trojans initially and later as my financial embarrassment eases add another two with enough solar to help keep the battery bank charged.
Batteries in a bank should always be installed together and replaced together. Adding new ones to a bank that contains old ones can cause significant imbalances within the bank, dramatically shortening the life of all the batteries.

If you think you will enlarge the battery bank in a few years, start by building a large enough battery box to handle the whole thing, even if the initial setup will only fill half of it. When it comes time to expand, sell the old batteries (they may still have enough life left to be worth a fair bit) and buy all new, matched batteries. This will be quite a bit cheaper than having to replace the whole bank early when the imbalances damage it.

Have you done daily and weekly amp-hour consumption calculations yet? It's pretty hard to choose batteries without those calcs.
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Old 29-11-2012, 20:14   #10
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Re: One battery?

I use a LiFePo4 200 aH bank for everything.
Watermaker, refrigeration with freezer, engine start, HAM, laptop with wifi, chartplotter, GPS, etc.
320 watts of solar into one battery bank does it all. In fact, here in the PNW, the fridge is running right now with no shore power. What's not to like?
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Old 30-11-2012, 03:14   #11
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Re: One battery?

Why thank you all for your input all, some great advice here and options to look at.
Thank you all.
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Old 30-11-2012, 03:55   #12
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Re: One battery?

Smaller battery bank, more solar. The energy comes from the solar. The batteries are for nighttime and dark days. I would think the battery bank should be able to be mostly charged in two sunny days. So 40W of solar panel might give you 20Ah of charge (at 12v, 6 good hours) per day. A 40 to 80 Ah battery should be enough.

Too large a battery might even have a significant self-discharge rate ... anybody know?

The other nice thing, which I post every time, is that new batteries are so much better than used batteries that keeping the investment small might enable you to replace them more often.

I would think even such a small battery would support your tiny loads for many days.
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Old 30-11-2012, 04:23   #13
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Re: One battery?

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Smaller battery bank, more solar. The energy comes from the solar. The batteries are for nighttime and dark days.
Good advice.
I do have a soft spot for the 6v Trojan batteries. (Batteries are very expensive in OZ), but they are a little too large to be cost (and weight) effective in your system.
If you are planning on upgrading the system they would be a good choice as you could add a lot more solar later without worrying about adding extra batteries and the associated problems of mixing old and new.

40w should be enough for your equipment at the moment (although you don't say where you are, there is a big difference in insolation values between Tasmania and Brisbane), but there is several things left off the list VHF, Phone charger etc that you are likely to want. The way forward is more solar and multihulls are in the great position of having plenty of room for them.
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Old 30-11-2012, 09:49   #14
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Re: One battery?

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Originally Posted by noelex 77 View Post
Good advice.
I do have a soft spot for the 6v Trojan batteries. (Batteries are very expensive in OZ), but they are a little too large to be cost (and weight) effective in your system.
If you are planning on upgrading the system they would be a good choice as you could add a lot more solar later without worrying about adding extra batteries and the associated problems of mixing old and new.

40w should be enough for your equipment at the moment (although you don't say where you are, there is a big difference in insolation values between Tasmania and Brisbane), but there is several things left off the list VHF, Phone charger etc that you are likely to want. The way forward is more solar and multihulls are in the great position of having plenty of room for them.
I am am up on the sunshine coast, and you are right about the vhf/charger. The trojan route with more panels later seems to be a good idea.2x6v or 12v ?

cheers
paul.
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Old 30-11-2012, 09:57   #15
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Re: One battery?

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2x6v or 12v ?
a single deep-cycle 12v, either group 24 or 27, will weigh significantly less than two 6v golf cart batteries.
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