What to do with batteries I am not using for a long time, in the cold.

[kevinnem]

I have 2 starting batteries, and 2 "house" batteries in my boat. The 2 house batteries are 6 volt GC2 (golf cart batteries).

I will not be using my boat for the next 6-8 months.

The house batteries are hooked up to a solar panel and MPPT controller. The starting batteries are only hooked to the engine.

They are all currently charged.

What is best practice, so that I don't have to replace them next year?

Local temperatures will hit -30c maybe up to -40c.

Thoughts?

Kevin.

[DeepFrz]

Best advice I can give with the limited information that you have provided is to disconnect them all and take them to your basement where you can give them a top up charge every couple of months.

[SecondBase]

Suggestion: Upgrade your battery caps. Will make a significant difference. I like this model.

[Paul Elliott]

Folks, the issue here is the -40C temperature. I know that letting batteries freeze is a very bad idea. Will a constant trickle charge keep the batteries warm enough, and if so, how much charging current is necessary?

OK, I googled this and found a paper by Trojan about battery storage: http://www.trojanbattery.com/pdf/WP_...orage_0512.pdf

It appears that with a 100% charged battery the electrolyte won't freeze until the temperature drops to -68 deg C. At 85% charge the battery is good down to -52C.

Assuming that the OP's batteries are flooded LA, it seems that a small trickle charge will do the job.

[UNCIVILIZED]

Keep them somewhere warm'ish for the winter. Topping them off from time to time.

[Slamjunk]

Best practise is to bring them somewhere warm, 2nd is to charge them fully and disconnect them fully. I’ve left my Jeep in Yellowknife over the winter and it started in the spring after reconnecting. I did the same with my f-250 at various times. I wouldn’t leave older batteries outside even fully charged, if a cell is weak it could allow the battery voltage to come down to a point where it could freeze.

[john61ct]

Assume on float, put them all in a box with a small 12V heating pad, cheap from trucker supply.

Get fancy if you like, $10 thermostat off eBay.

[alley]

Agree that the best scenario is to remove batteries and store them somewhere warm with a float voltage applied.

If that's not feasible, then a second option would be to parallel the starting bank in with the house bank so that it, too, will have the solar array there to provide either a trickle charge or float voltage to minimize any chance of freezing.

Is the regulator on the solar array capable of going into a float mode if the batteries are full?

[wrwakefield]

Originally Posted by kevinnem

I have 2 starting batteries, and 2 "house" batteries in my boat. The 2 house batteries are 6 volt GC2 (golf cart batteries).

I will not be using my boat for the next 6-8 months.

The house batteries are hooked up to a solar panel and MPPT controller. The starting batteries are only hooked to the engine.

They are all currently charged.

What is best practice, so that I don't have to replace them next year?

Local temperatures will hit -30c maybe up to -40c.

Thoughts?

Kevin.

Kevin,

Unfortunately we also achieve those cool conditions in interior Alaska on occasion. Lead acid batteries will do fine as long as they are kept charged. [Supplementing the literature with personal experience, I can attest that discharged lead acid batteries will freeze at those temps and are not recoverable after that- even if they remained intact after freezing...]

If you can't keep lead acid batteries warm, keep them charged and they won't freeze at those temps.

Also if they are lead acid and not adequately charged during your period of absence, the self discharge rate may allow them to reach a low enough charge state that they could freeze later into the timeline you mention- if the temps get that low then.

Healthy AGMs have a slower self discharge rate and will likely survive if initially fully charged.

The best practice in such conditions- if you cannot keep the batteries warmer- is to keep a trickle charge on them.

As you know, how much you might hope to gain from your [clean, snow free] solar panel(s) will depend upon your latitude and panel positioning... Given the temps you mention, I suspect you may need to supplement solar charging Dec-Feb [assuming northern hemisphere...]

Here is a good reference from Battery University regarding storing batteries [of all types...]

Best wishes for a positive outcome when you return to your boat.

Cheers! Bill

[Mike OReilly]

All of my cruising has been done in cold climates where it definitely freezes throughout winter. While the best option is to take the batteries home and charge them occasionally throughout the winter, that is not always possible.

If the solar will produce enough amps then it might be OK to let that keep them up. I tried that one year without success. My batteries were dead when I came back. Interestingly though, they did not die. I charged them up and they worked great for two more years.

When possible I have been able to get down to the boat through the winter and charge them up periodically. This works great.

But what I have done most years is charge them fully, then completely disconnected them. I usually leave them like this for up to six months through the cold winter. Not ideal, but in my Canadian cruising world, pretty common for most of us, and I’ve never heard of anyone having any problems.

My understanding of the chemistry is that cold temps will slow the self-discharge rate. So as long as the batteries are fully charged, and the cold sets in before much discharge has happened, you should be fine for six or seven months. Get back to them as soon as you can.

[hamburking]

I live in kingston ontario. And although its not alaska, we put the boats on the hard for the long cold winter, and we usually get a week or two at least down at 30 below or worse.

When I wore a younger man's shoes, I would bring the batteries home each winter, and keep the topped up in my warm basement where I would diligently monitor their open circuit voltage. But as my shoes got older, I found the batteries seemed to be getting heavier each year. Finally, an old friend told me a new battery is cheaper than a new back. So I started leaving them aboard.

Left on board, fully charged, and with no other attention, the volts would be down a bit in spring, but still plenty to start the engine. Did this a few winters. No trouble at all. Lead acid batteries. Cheap canadian tire deep cycle marine batteries.

Then on the next boat, I had the bright idea to hookup a small charger, 4amps I think. I ran the cord off the boat, and left the plug hanging near a power outlet nearby. A few times during the winter, when the temps where really getting low, I would plug in the charger for 24 hours. No need to climb on the boat, clear snow, or open hatches. Just plug it in. Come back the next day and pull the plug. In the spring, I would plug it in for 24 hours a few weeks before launch. And maybe just before launch too. Worked great. Full batteries all the time, and they lasted for years. Same type of cheap FLA batteries.

The real danger with leaving a charger attached (and active) is boiling the batteries dry. They WILL EXPLODE. Something called THERMAL RUNAWAY. To offset this possibility, make sure your batteries are topped up before you go, and use a small charger. I believe they sell 2amp, smart trickle chargers for just this purpose. And they are not expensive.

[alley]

This is why it's important to have a charger that will go into a "maintenance" or "float" mode once the batteries are fully charged. This decreases the voltage (typically to 13.1 V) to where it will offset any self-discharge of the battery without boiling off any electrolyte. At that point, there is very little (milliamps) of current flowing through the battery and it can be maintained in this state indefinitely without worry of electrolyte boiling or plate sulphation.

[ramblinrod]

Originally Posted by kevinnem

I have 2 starting batteries, and 2 "house" batteries in my boat. The 2 house batteries are 6 volt GC2 (golf cart batteries).

I will not be using my boat for the next 6-8 months.

The house batteries are hooked up to a solar panel and MPPT controller. The starting batteries are only hooked to the engine.

They are all currently charged.

What is best practice, so that I don't have to replace them next year?

Local temperatures will hit -30c maybe up to -40c.

Thoughts?

Kevin.

Many believe it is wise to remove batteries for the winter.

We winterize about 20 boats per year in southern Ontario, and this is what we recommend to our customers and in our marine maintenance seminars.

1. Removing and reinstalling batteries holds too great a risk of damage to the batteries, the boat, the vehicle, and the person.

2. Leaving charging systems (either shore power or solar) operational while unattended poses too great a risk of an electrical fire should something go wrong.

3. Top up the electrolyte with distilled water.

4. Charge the batteries fully.

5. Perform a load test.
a) if they pass disconnect the negative terminals; they'll be fine until spring.
b) if they fail take them to a battery recycler.

On an associated note, semi-flex panels should not be flexed (left outside exposed to wind) below OC (32 F).

[CaptTom]

Originally Posted by ramblinrod

Many believe it is wise to remove batteries for the winter.

We winterize about 20 boats per year in southern Ontario, and this is what we recommend to our customers and in our marine maintenance seminars.

1. Removing and reinstalling batteries holds too great a risk of damage to the batteries, the boat, the vehicle, and the person.

2. Leaving charging systems (either shore power or solar) operational while unattended poses too great a risk of an electrical fire should something go wrong.

3. Top up the electrolyte with distilled water.

4. Charge the batteries fully.

5. Perform a load test.
a) if they pass disconnect the negative terminals; they'll be fine until spring.
b) if they fail take them to a battery recycler.

+1 - best answer yet.

Back in the old days we all believed the dire warnings about leaving them in the boat, and also about storing them on a concrete floor. We'd build elaborate wooden shelves and drag them out each winter.

All unnecessary. A fully charged FLA battery will survive the winter, if it's disconnected. Better still is the suggestion to plug in a charger once in a while, but I've found when I do that it almost immediately goes to "float," confirming that I didn't really need to.

This is not Alaska, but Maine used to get some pretty cold weather too.

[marujo.sortudo]

+1 to both of the above. If they happen to be sealed batteries that the manufacturer recommends equalizing from time to time, I find spring is a nice time to equalize them. I've been getting a few more years out of my AGM starting battery this way.