Battery Drain problem

[djbroughton]

I purchased a Mobicool cooler for my because they were such a great deal at Canadian Tire this week. I would like to get an Engel but just can't justify the $600 plus compared to $80. I also replaced my number 2 house battery and spent the night on the boat with the cooler running. Both batteries are now dead and need to be charged. I tried to keep the cooler on battery #2 but it still drained both batteries. How come? I have a jumper cable that runs from negative to negative between the two batteries. Is this the correct configuration?

FYI- the Mobicool says it draws 46 watts for cooling

Dave Broughton- Calgary, Alberta

[DaveB]

You should always have both batteries the same kind and bought same time. One can drain the other when parrel. Have both batteries to run the cooler, neg. to neg. pos. to pos. for 12 volts.
Use battery cables connecting the two and not jumper cables.
I use this system for my house deep cycle bateries and a starter battery for engine start.
They are charged by a 10 amp charger that charges both house and starter battery same time but independent of them.
Dave

I purchased a Mobicool cooler for my because they were such a great deal at Canadian Tire this week. I would like to get an Engel but just can't justify the $600 plus compared to $80. I also replaced my number 2 house battery and spent the night on the boat with the cooler running. Both batteries are now dead and need to be charged. I tried to keep the cooler on battery #2 but it still drained both batteries. How come? I have a jumper cable that runs from negative to negative between the two batteries. Is this the correct configuration?

FYI- the Mobicool says it draws 46 watts for cooling

Dave Broughton- Calgary, Alberta

[Hardcrab]

djbroughton,
Not enough information in your post to understand your battery wiring set-up.
You have the two negatives tied together, which is correct for an "either/or" type set-up, but is that your intent?

As far as your current usage, what size battery do you have? Group 24, 27, etc?
Group 24 batteries are rated about 55 amp hours.
That's 1 amp draw for 55 hours, or 55 amps for 1 hour, or 110 amps for 1/2 hour, or 1/2 amp for 110 hours, etc.etc.
These results are only meant to be approx and not the gospel.

Your device is rated at 46 watts.
46 watts divided by 12 volts equals 4 amps current draw for quick rule of thumb figuring.
4 amp draw applied to a 55 amp-hour source gives 13 hours of use until a discharged battery, in theory.

Actual times will vary, but always less than expected.

Depending on when you started your "overnight", the battery size, and the actual state of charge at the start, you might be in the ballpark.

Ice might be a better answer

[Love MACs]

So to expand on your explanation Hardcrab... are two 55 amp batteys wired in parallel 110 amps total?? What if the are wired in series?? Or is that too obvious As you can see I am electrically challenged, to say the least And can you wire too house batterys in parallel and then wire them to the starter battery in series The only reason I can think to do that is so the all batterys could be charged when the engine is running, but the starter battery would not be drained when using the house batterys for lights, CD etc. Now I think I even have myself confused



Allan

[PollyAnna]

Allan,

Here is a good reference book to keep handy for questions like these:

http://www.marineengine.com/books/e3.html

I got mine from half-price books. A couple things to remember is that batteries in parrallel add amps like volt when batteries are connected in series. 2 12 volt/55 amp batteries connected in parallel have 12 volts and 110 amps capabilities, wereas, if they are wired in series (negative of one to the positive of the other) have 24 volts and 55 amps.

It is highly suggested that if you plan to run two batteries in parallel, they should be purchased at the same time. As use time climbs, the battery will always loose a little of it capability, so if you take an old batteries and connected it with a new one in parrellel, the old battery will limit the amount of charge and acutally discharge the new battery till it equalizes.

But, my suggestion is to get the book, look through it, there is a lot more to than just the batteries to be concern with....

Best of luck,

Shu

[Y.B.Normal]

If you connect your batteries in parallel, the total number of amps of both batteries is what you have available at 12 volts
ie 55+55= 110 amps @ 12 volts. If you connect the batteries in series, you'll have 24 volts (12+12=24) and 55 amps.
I suggest you get a battery switch that allows you to switch to battery A, battery B, Both or Off. You never want to drain all of your batteries completely if you want one to start your engine.
You could connect 2 batteries in parallel for the house batteries (battery A) and use a third battery separately (battery B) for starting the engine. In this case, you would have 110 amps (55+55=110) available for your cooler, lights, etc., and 55 amps for your starting battery. Clear as mud?
An idea my wife picked up during her Charter Certification Course is to have the battery switch switched to BOTH whenever the engine is running. This helps to keep all the batteries charged.
Having gone through what you're going through now with an energy-sucking cooler, I suggest you go with the previous suggestion and go with an efficient ice-cooled cooler. That's what I did. I use the 12V cooler for traveling in the car.

[djbroughton]

djbroughton,
Not enough information in your post to understand your battery wiring set-up.
You have the two negatives tied together, which is correct for an "either/or" type set-up, but is that your intent?

As far as your current usage, what size battery do you have? Group 24, 27, etc?
Group 24 batteries are rated about 55 amp hours.
That's 1 amp draw for 55 hours, or 55 amps for 1 hour, or 110 amps for 1/2 hour, or 1/2 amp for 110 hours, etc.etc.
These results are only meant to be approx and not the gospel.

Your device is rated at 46 watts.
46 watts divided by 12 volts equals 4 amps current draw for quick rule of thumb figuring.
4 amp draw applied to a 55 amp-hour source gives 13 hours of use until a discharged battery, in theory.

Actual times will vary, but always less than expected.

Depending on when you started your "overnight", the battery size, and the actual state of charge at the start, you might be in the ballpark.

Ice might be a better answer

When I got the boat this spring, the positives and negatives on both batteries lead somewhere. There is another black cable connecting the two negatives. I will try to gather the necessary info but we are heading out on a 10 day trip with the tomorrow so it might take some time. My intent was to use one battery to run accessories ie: lights, and cooler and the other to start the motor.

Maybe some sort of battery monitoring system is the way to go?

Appreciate the calculation info., I will try to figure out something with that.

Dave

[Hardcrab]

Monitors are cool but pricey.
A good multimeter tells you what you need to know and is available for other jobs as they come up.
Cheaper to boot.
I'd run your stuff from one battery, and leave one only for start.
Or go to Walmart and get a starting battery for the motor and stow it until you need it.
I'd think a larger motorcycle or garden tractor battery would work well for emergency starting duty for outboards used on the Macs.

All of the other replies are right on.
Good points about buying new batteries together to parallel for 110 amp hours at 12 volts.

In a perfect world, maybe.

But, I'll throw out this next useless tidbit for consideration.

If one parallels two batteries, he is, in effect, wiring twelve 2.2 volt, 55 amp hour individual cells together, first in series by it's construction and then in parallel to get the 110 amp hours at 12 volts.
2 battery cases, each with 6 discreet 2.2 volt cells.
Manufacturing slop as it is, none of these twelve cells will be identical or "matched" to each other.
Even in the same six cell battery.
Buying new is as close as you can ever hope to get, but far from the technical ideal.

Cells wired to each other should have the same "matched" discharge/charge profiles over the same time period as measured into a load, in an ideal world.

The fallout from this means that the upper "most healthy" cells in the twelve cell system will spend some of their energy feeding the lower "least healthy" cells, (relative terms) resulting in an average voltage/current availble for external use.
This results in a parasitic internal loss of energy not available to power the desired devices.
Average will always be less than the max, that which we really desire in a battery system.

You can't do much about the six cells per battery, but you will have more energy for the long run if you don't parallel them together.
Use the first battery until it's discharged, then switch to the second battery.

Nobody does this, but they could for best results.

Useless information, but something to chew on.

[pokerrick1]

An idea my wife picked up during her Charter Certification Course is to have the battery switch switched to BOTH whenever the engine is running. This helps to keep all the batteries charged.

OR when plugged into shore power to keep both batteries charged. One thing I had to ADD to my checklist of things to do when going out sailing (and I learned the hard way) - - I used to sail with my battery switch on BOTH - - - but then one day the stereo, lights, GPS, et all drained both batteries and I couldn't lower the engine to start it (or start it).

So I was advised to turn the battery switch to 1 when sailing so there was always a full battery with which to start the boat; and that was good advice! Then, when I got back to the slip, I turned the battery switch back to BOTH for charging. From that point forward, I always had sufficuient batteries for everything.

Rick less in Las Vegas

[djbroughton]

Appreciate the many replies. Will study this new info. and make some changes.

This is a great list!

Dave

[puggsy]

To solve that problem, I fitted a " RED ARC " battery controller. It allows the cranking/ starter battery to be brought up to full charge, then swaps the charge over to however many batteries you have set up for accessories, such as your fridge. I have fitted FIVE accessory batteries, all in a 12 volt bank...wired back to an ACCESSORY switch board. I can flatten all these and it will not affect my main cranking battery...the system is working fine. And I check the voltages on all batteries regularly.



Cost was about $120AU but well worth it.

[c130king]

Many, many, many threads on this topic...search them out and you will learn more than your brain can handle (at least I know my brain is quickly overloaded with electrical knowledge...that never seems to stay in my brain long enough).

As to motoring with the switch in BOTH to charge both batteries. A option, which I will be installing soon, is a Yandina Combiner (looks like they are $59 now but I got mine almost a year ago for $49). No matter which battery is hooked directly to the alternator based on the position of the 1-2-BOTH-OFF switch, the charge is shared via the combiner. There are other products that do the same thing.

I am installing 2 x Group 24 batteries (I think I have seen 70AH batteries advertised...but I haven't physically purchased them yet) and a 1-2-BOTH-OFF switch along with the aforementioned (oooh big word) combiner. As well as a new 8-position fuse/switch panel to replace the stock 4-switch panel. Hopefully starting on 31 August when I get back to the U.S.

My plan, which I got from some very experienced folks on this site, is to use Battery 1 on odd days and battery 2 on even days. If for some reason I happen to leave all my lights, my GPS, my radio, my stereo, and possibly some other future electronic gizmos such as a TV or powered cooler on overnight and drain my battery I can switch to the other battery and ensure I have power to crank the motor. Seems logical to me.

If you use always one battery as the house and one as the start battery then it seems to me you may easily run down the house battery frequently and rarely run down the start battery (depending on useage of course) thus over time wearing out the house battery faster than the start battery. This may not be a big deal. But my way of switching batteries based on odd/even days should ensure fairly level useage over time and hopefully a longer life for both my batteries.

YMMV.

Good Luck,
Jim

[Russ]

Now you know why the Engels are so expensive. They actually work and don't consume very much power. The cheaper units are power hogs and will drain your battery FAST. They work great in cars with the engine running. Go with a good quality (5-6 day) cooler and block ice.

What I don't understand is how you select which battery is being used. If you have an (A/B Both) switch I can understand. In that situation, keep one battery for starting the other for house. Otherwise, you can use what we have which is a combiner (as mentioned above). Our starting battery is connected directly to the engine and is not connected to the house battery which runs everything else. If the house drains down, the starting battery is isolated and charged.
Then when the engine is running and charging, the combiner connects the two batteries and charges the house battery. Shut off the engine (and no longer charging) and it disconnects.

I had a boat with A/B Both switch and always forgot to switch it back to the house bank. The combiner is a no brainer. If it's charging, both get charged. If I run the house down, I have the starting battery isolated to get me going.

Another good idea is to buy one of those jumper packs. In a pinch (dead batteries) you can jump start to get you home.

--Russ

[DaveB]

Another way of doing it is get two 6volt golf cart batteries @ $75 each and connect them in series for 12volts. I used them on my Compac 19 and were still in excellent shape when I sold the boat. They take many discharges without hurting them and have high amps.Many liveaboards will have 4 or more of these batteries for house.
David