dual 6 volt batteries

timebandit · Mar 15, 2012

You don't suppose that when switching from 110v to 12v that the compressor had to start aginst too much head pressure and that is the reason for the big start load.

Might try switching over after the frig has shut down on it own and had time for the compressor to bleed down befor switching to 12v.

"I went back to the boat yesterday and did a little snooping around.
The fridge was running on AC. It showed about 33 F. so it was near shutting down, but was still running. I plugged in the 12 volt, then unplugged the 120. It shut down just like I thought it would. This time, instead of trying to get it to start, I just waited. Well it took maybe 3-4 minutes and it started up on its own.
I feel better about that now. I guess it just takes a few minutes for it to make the switch over??
Amp draw still went to 7 or 8, and volts dropped to 11.8 from (I forgot. 12.8 maybe). I pulled the plug and found the end was hot enough to burn if I kept touching, so I cut the 12 socket plug off and attached a 3 ft #10 extension, and wired it direct to the battery.

finding41 · Mar 20, 2012

I poped into Interstate Batteres today to ask some questions about wirirng and battery /solar /tender charger / pricing. What they recommend is 2 6v golf cart batteryes. The guy told me you can draw 30 amp for 7 hr! Unless I put central air in my 26D that's way more than I will use on a long weekend.
Pricing was pritty good to. ( I think, more research needed.) $270 for a 30w solar panel with mounting hardware and wiring. $40 for a .75amp tender. $ 100 each for the batteries.

Sumner · Mar 20, 2012

finding41 said:
I poped into Interstate Batteres today to ask some questions about wirirng and battery /solar /tender charger / pricing. What they recommend is 2 6v golf cart batteryes. The guy told me you can draw 30 amp for 7 hr! Unless I put central air in my 26D that's way more than I will use on a long weekend.
Pricing was pritty good to. ( I think, more research needed.) $270 for a 30w solar panel with mounting hardware and wiring. $40 for a .75amp tender. $ 100 each for the batteries.

I think the guy is full of it myself. Most of the 6 volt batteries are about 230 amp/hours or in that range. You can't add the amp/hours of 2 6 volt batteries together if you are running them in series for 12 volts. You have about 230 amp/hours total. They don't recommend running them down over 50% for long life so that would be about 115 amp/hrs if you did that or about 4 hours using his 30 amp discharge and a discharge that high would even run the batteries down faster as they are rated at a much lower discharge rate. If you don't worry about the life of the battery you could run it down to as low as 20% or so with a 'true' 6 volt deep charge, but I wouldn't.

I know you aren't in the states, but here you can do a lot better than that for solar pricing. Solar Blvd has had 80 watt panels on sale for as low as $99 recently and a 10 amp PWM controller for $45. They have a 40 watt like...

http://purplesagetradingpost.com/sumner/macgregor/outside-22.html

.... we got a couple years ago for $55. A good MPPT will cost more though and is what we are using.

Sum

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Scott B · Mar 21, 2012

finding41 said:
I poped into Interstate Batteres today to ask some questions about wirirng and battery /solar /tender charger / pricing. What they recommend is 2 6v golf cart batteryes. The guy told me you can draw 30 amp for 7 hr! Unless I put central air in my 26D that's way more than I will use on a long weekend.
Pricing was pritty good to. ( I think, more research needed.) $270 for a 30w solar panel with mounting hardware and wiring. $40 for a .75amp tender. $ 100 each for the batteries.

That's actually a pretty good price for those batteries. I was quoted 140 from Interstate couple years back. Other than that, I would not listen to "the guy" since he doesn't know what he's talking about....

finding41 · Mar 21, 2012

I'm grateful for this site. I was wondering if 30w would be enough. No eh. I like Doe hunter will only be spending weekends on the boat htis year and can plug it in when it's moored in the driveway. I am installing all new wiring and led lights throughout. The only other electrical things will be; bilge (That's a big one if it rains but I can augment with a bucket.), Lowrance chart/GPS/ look at the fishy thing, Tablet for active captain and entertainment, both radios. All 12v.
I found a place in town that sells just solar and plan to pop in when I get a chance.
(What is the deal with running deep cell batteries down? Buddy at Intersttate said that they will get a memory... Why don't the batterys in my vehicle get memories? I have a Interstate battery in the work van from 2003. 700 cca I think. Still works fine. The battery is on its 4th van! Is he pulling my rode?

Cruiser1 · Mar 21, 2012

Thanks to all for this very informative thread. I currently run a single 12V battery and have a spare are home. Once these are done I would like to go to a 2 x 6V in series system. I have just blown my 3Amp Calibro battery charger and was thinking of going to a 7Amp C-Tek - lot more expensive. As the changer needs to be matched to the volts I assume one would charge the 2 x 6V at home with them wired up in series? Am I missing something here as I don't wish to shell out for an expensive 12V chager and then find I have to replace it with a 6V charger later on when I go to 2 x 6V?

Sumner · Mar 21, 2012

Cruiser1 said:
Thanks to all for this very informative thread. I currently run a single 12V battery and have a spare are home. Once these are done I would like to go to a 2 x 6V in series system. I have just blown my 3Amp Calibro battery charger and was thinking of going to a 7Amp C-Tek - lot more expensive. As the changer needs to be matched to the volts I assume one would charge the 2 x 6V at home with them wired up in series? Am I missing something here as I don't wish to shell out for an expensive 12V chager and then find I have to replace it with a 6V charger later on when I go to 2 x 6V?

You would use the 12 volt charger and have them in series. To avoid confusion here is a link with pictures.....

http://batteryminders.com/static_page.php?nick=b_multi#12s

..... Sum

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Sumner · Mar 21, 2012

finding41 said:
I'm grateful for this site. I was wondering if 30w would be enough. No eh. I like Doe hunter will only be spending weekends on the boat htis year and can plug it in when it's moored in the driveway. I am installing all new wiring and led lights throughout. The only other electrical things will be; bilge (That's a big one if it rains but I can augment with a bucket.), Lowrance chart/GPS/ look at the fishy thing, Tablet for active captain and entertainment, both radios. All 12v.
I found a place in town that sells just solar and plan to pop in when I get a chance.
(What is the deal with running deep cell batteries down? Buddy at Intersttate said that they will get a memory... Why don't the batterys in my vehicle get memories? I have a Interstate battery in the work van from 2003. 700 cca I think. Still works fine. The battery is on its 4th van! Is he pulling my rode?

Your van battery can supply a lot of amps for short periods, just what you need to start the engine, but since hopefully it starts right up the amp/hour amount isn't very high as the high amp draw is for only a couple seconds.

The alternator replenishes that quickly and the main purpose of the alternator is not so much to charge the battery, but provide any electricity that is needed while the vehicle is running and not require the battery to do that.

On a boat it is about the opposite. We use the battery to provide the electricity as it is needed and then usually try and replenish it by charging either at the dock or with the engine or some other charging system.

One nice thing about solar is that electricity that is being used when the panels are seeing the sun is hopefully provided by the panels and not the battery, kind of like the alternator in the car.

Sum

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Cruiser1 · Mar 21, 2012

Sumner said:
You would use the 12 volt charger and have them in series. To avoid confusion here is a link with pictures.....

http://batteryminders.com/static_page.php?nick=b_multi#12s

..... Sum

Thanks Sumner - that is a very handy site to have for future reference on battery issues.

walt · Mar 22, 2012

For Finding..

My experience.. I have LED lights in the cabin (but lots of them), run LED 110V Christmas tree "anchor" lights, run a car stereo as much as I want, VHF radio listening, use a lap top computer occasionally run from an inverter, DVD player. In the past, I’ve had teenagers on the boat watching movies, charging video games, etc. I generally make almost no effort to conserve electricity on the boat (unlike at home).

I find that my typical use is around 20 to 25 amp hours per day - sometimes a little more, sometimes a little less.

The 30 watt panel - if in a good spot - will supply maybe 8 amp hours per day. Assuming you use 25 amp hours, your deficit per day is 25 - 8 = 17 amp hours.

If you have two golf cart batteries, you have about 100 amp hours you can use. So at a deficit of 17 amp hours per day, you can go for about 6 days without any worry about the battery getting discharged past 50%. If your outboard has charging, you can go even longer.

I think 30 watt is not a bad choice for a trailer sailor - especially since 99% of the time you own the boat, the panel will be doing nothing more than keeping the batteries topped off.

If you get a fridge, these numbers all change dramatically and then you need a LOT more charge capability. But if you don’t mind an ice chest and buying a block of ice, the 30 watt panel and the two golf cart batteries are very adequate for under a week trips.

FYI, that is a 40 watt panel in this picture. This was in Febuary at Lake Havasu and the sun stayed low enough that I needed to tilt the panel. In the summer, you probably dont really need the tilt.

Maine Sail · Mar 22, 2012

walt said:
If you have two golf cart batteries, you have about 100 amp hours you can use. So at a deficit of 17 amp hours per day, you can go for about 6 days without any worry about the battery getting discharged past 50%. If your outboard has charging, you can go even longer.

One thing folks very often forget is that you will rarely if ever get back above 80% SOC once you've been away from the dock for more than a day. Even running the motor will rarely get you above 80% SOC.

225Ah's / 2 = 112.5 Ah's usable from 100% SOC before you hit a 50% SOC.

Or 80% SOC of 225Ah's = 180Ah's - 112.5 (to 50% SOC) = 67.5 usable Ah's......

This cuts the use at an average of 17Ah's day down to about 4+/- days. Still not bad but if you went six, and did not have a battery monitor, you could be chronically discharging your bank more than you think.....

If you're under the banks rated 20 hour load of 11.5A, which most trailer sailors would be, then you'll get slightly more amp hours due to Peukert but you'd need a monitor to accurately keep track of this..

For example an average load of 4A on a 225Ah bank with a Peukert of 1.2 would give you approx 277 Ah's of capacity vs. 225Ah's @ 11.5A...

walt · Mar 22, 2012

I always start a trip 100% charged.. the battery monitor does give me a lot of peace of mind since I know exactly what my deficit is every day.

On my last three day trip where I was both sailing and running the outboard charger, I think the most I was down was about 30 amp hours - mostly because of the long Feb nights running about .7 amps for all the anchor lighting.

And.. I was even removing the solar panel during the day to sail..

walt · Mar 22, 2012

Since the "80%" battery usuable capacity has been mentioned several times, I wanted to give some of my personal experience regarding this.

In my case, when I do an outing, I start with the batteries completely charged (usually from the 40 watt solar panel charging them for a long time).
What I have observed is that my solar charge controller (this one http://www.ecodirect.com/ProductDetails.asp?ProductCode=Morningstar-SunLight-SL-10L-12&site=google_base) will charge the batteries with all the current available from the solar panel even when the battery state is between 80 to 100%. This is because the solar current is less than 2.4 amps and this is less than the controller/battery maximum acceptance even when the battery is near full charge.

My Nissan 9.8 hp outboard (about 2010) however does have some sort of regulation – but it’s a very simple regulation that backs off the current when the battery voltage gets much above 13 – maybe 13.5 volts. So on the first few days of the outing, even though the outboard is capable of 6 or so amps, I’ve noticed that what the battery is actually receiving is considerably less current. Since 6 amps is still low compared to what the two golf cart batteries will accept, I start to get the full 6 amps when the battery is down a bit (exactly where I’m not sure – maybe 90%???).

So during my trip, I start at 100%, maybe drop to 85% by the next morning, charge back up a little during the day, drop again at night etc. All I really care about is that at the end of the trip, I don’t have the battery much below 50%. Since I am lucky to do a long enough trip where I get the battery down this low once per year, it probably isn’t a big deal to even go below 50% - since I hardly ever do this.

The 80% number more applies to larger boats where you have a high amp generator (like 50 amps) and a big daily draw (like a fridge) and are using the boat for extended trips where you draw the batteries down a significant amount every day and then need to put the bulk back in using the generator.

Kestle · Mar 22, 2012

walt said:
For Finding..

My experience.. I have LED lights in the cabin (but lots of them), run LED 110V Christmas tree "anchor" lights, run a car stereo as much as I want, VHF radio listening, use a lap top computer occasionally run from an inverter, DVD player. In the past, I’ve had teenagers on the boat watching movies, charging video games, etc. I generally make almost no effort to conserve electricity on the boat (unlike at home).

I find that my typical use is around 20 to 25 amp hours per day - sometimes a little more, sometimes a little less.

The 30 watt panel - if in a good spot - will supply maybe 8 amp hours per day. Assuming you use 25 amp hours, your deficit per day is 25 - 8 = 17 amp hours.

If you have two golf cart batteries, you have about 100 amp hours you can use. So at a deficit of 17 amp hours per day, you can go for about 6 days without any worry about the battery getting discharged past 50%. If your outboard has charging, you can go even longer.

I think 30 watt is not a bad choice for a trailer sailor - especially since 99% of the time you own the boat, the panel will be doing nothing more than keeping the batteries topped off.

If you get a fridge, these numbers all change dramatically and then you need a LOT more charge capability. But if you don’t mind an ice chest and buying a block of ice, the 30 watt panel and the two golf cart batteries are very adequate for under a week trips.

FYI, that is a 40 watt panel in this picture. This was in Febuary at Lake Havasu and the sun stayed low enough that I needed to tilt the panel. In the summer, you probably dont really need the tilt.

Walt, am a waffling around on how to mount my panel off the stern. Would you mind posting any picture you have of your mount?

My problem is that I launch by crane off of a trailer, so going much above the rails is not an option.

Jeff

walt · Mar 23, 2012

I think you should be able to find a bunch of threads in sailboat owners with good ideas on how to do this..
http://forums.macgregor.sailboatowners.com/showthread.php?t=134705
http://purplesagetradingpost.com/sumner/macgregor/outside-22.html
http://purplesagetradingpost.com/sumner/macgregor2/outside-33.html
http://www.holderness.info/boats-a-projects/macgregor-mods.html

My setup
http://i359.photobucket.com/albums/oo33/waltcolorado/Mac%201990S/IMG_7894.jpg
http://i359.photobucket.com/albums/oo33/waltcolorado/Mac%201990S/IMG_6486.jpg

finding41 · Mar 23, 2012

Thanks All! One thing.. Is everyone using 6v batterys or 12v right now?
I was thinking of just using the 12v I have this year and changing to two 6v next season. (I just have a ton of stuff to do on the boat now before we get it in the water. Rewireing is one of those things but I am going to keep using the old fuse box and the newer one a PO installed. Total of 7 fuses between the two. I will be leaving a BIG idiot loop to allow me to place the batterys somewhere other than under the starbourd seat)

Sumner · Mar 23, 2012

I'm using 2 12 volt and will until they need replaced and will then switch. If your battery is doing the job now I use it till it dies,

Sum

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dual 6 volt batteries

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