Odyssey AGM batteries, continuing confusion with charging

[jen1722terry]

Hello again,

I’d like to resurrect this thread to update all of you on our continued issues with charging our Odyssey AGM batteries on our CD 31.

We have two Odyssey group 31s (92 ah each) for a house bank and one Odyssey group 24 (62 ah) for a starter (all installed new in 2015). We also have a 130 watt solar panel and a new 65 amp engine alternator. We originally had a Morningstar Duo-Saver solar controller charging the house bank and the starter battery on separate circuits controlled by the standard battery selector switch.

On the advice of some kind folks on this board, especially Maine Sail, we learned that the Duo-Saver was not providing sufficient voltage to fully charge and maintain the three AGM batteries. So, we recently had a local solar electrician here in coastal Maine install a new Morningstar ProStar MPPT 25M controller.

A couple of problems occurred with the new controller installation:

The electrician informed us that we no longer have a separate charging circuit for our starter battery. All three batteries are now on one circuit. Thus, if a malfunction (like a bilge pump switch) should run down the batteries, we have no separate starter battery to rely on.

2. We just heard from Odyssey that, even with the new solar controller, we do not have sufficient solar charging power on board to get the full absorption charge on all three batteries. Thus, we may be slowly killing the batteries by not bringing them up to the full float charge at fairly frequent intervals. Sulfation of the batteries will eventually kill them.

3. Also, we’re not sure how long we have to run the engine and at what speed to have a chance of getting the two 92 amp AGM batteries to a full charge on a sunny day or on a cloudy day.

So, we feel we may have gained little by spending $800 to have the Morningstar ProStar controller installed.

So, what to do?

1. We own an Odyssey portable charger. We can bring the boat into a slip for shore power once a month or so and run the full “recondition” program on each battery individually to remove sulfation.

2. Disconnect the 62 ah starter battery completely (remove ground cable from battery) from the charging circuit (after reconditioning). It will just sit on board disconnected for the rare time we may need an emergency starter battery: it would then be used to start the engine with jumper cables or, if possible, by reconnecting it to the other two batteries via the solar controller for the engine start (this may not work if the other two batteries are really under charged). We’re not sure how to start our engine with jumper cables only now that the batteries are all on the same charging circuit (“in parallel” according to the Morningstar rep).


3. Doing the above would leave us with two, 92 ah Odyssey AGM batteries on the one solar charging circuit. We’re not sure that, even with this lower total amperage, we can fully charge these two batteries using our Prostar MPPT 25M controller with or without our 65amp engine alternator. We’re also not sure how long it might take to fully charge the batteries with the solar and engine alternator.

Any advice any of you can give would be most appreciated. If worse comes to worse and we’re slow killing our AGM batteries, we can start planning for new batteries that will work better with our on-board charging capabilities.

Pasted in below is the most recent message from Odyssey technical support.

Any comments or advice any of you can offer would be deeply appreciated. Also, if any of you can recommend a good marine electrician in the Mt. Desert Island area, we would love to hear.

Now, today, we’re looking forward to seeing many of the CD Maine summer cruise gang today at cocktail hour in Northeast Harbor.

Jenn and Terry McAdams
CD 31 “Glissade”

From Odyssey Battery customer support:

Equalization (exceeding 15.0V at 77°F or 25°C) is not recommended for any ODYSSEY battery as it can lead to overheating due to overcharging resulting in loss of critical moisture and premature failure. The charger is temperature compensated and that is good. You may see voltages exceed 15.0V when the temperature drops below a certain point which is acceptable when required. When paralleling batteries, the battery bank becomes the total Ah rating of all of the batteries in the bank. In this case 92 + 92 + 62 = 246Ah at the 10 hour Ah rate. At 40% of that rating, we would recommend a minimum charge current for the entire bank of about 100A. I would suggest doing a custom setting with Absorption at 14.7V for 180 min or longer if available, Float at 13.5V, and Equalize OFF. If the equalize mode can be set at 14.7V as well, then I would suggest turning that ON with maximum length available as well to prolong the Absorption time on charge if that is how it works (ask Morningstar to verify). That said, if the batteries are at 50% depth of discharge (12.2V with no electrical load), at 125Ah to recover it would take 5 hours (300 min.) at an optimum charge current of 25A at 14.7V to get to a 85-90% state of charge. Hence the recommendation to charge at 14.7V in both Equalize and Absorption modes for a combined charge time of about 420 minutes if that is how it works.

Note that a higher current charger would be recommended for the entire bank. At 25A (optimum) the charging system will eventually get the batteries fully charged however, I would not recommend discharging them below 50% depth of discharge on a regular basis. Most solar charging systems are about 85-90% efficient and can be less efficient and are dependent on the sun availability. A 130W solar panel can provide 8.8A at 14.7V optimum. I’m not sure but I believe that even if the controller can work at 25A max, a single 130W solar panel will never provide that type of current. It would take 3 panels that size to max out the system. I would contact Morningstar to confirm. If I am correct, then at optimum of 8.8A (100% efficiency), it would take almost 30 hours constant voltage at max current at 14.7V to get the batteries to 100% state of charge from 0%. Again, low current “trickle” charging is not recommended as it will contribute to the premature sulfation of the batteries over time. Solar charging tends to be that way. It will eventually get the batteries fully charged but will not de-sulfate the batteries as well as with higher current charging (100A for the battery pack).


_________________
Jennifer & Terry McAdams
Kearsarge, New Hampshire
Mahone Bay, Nova Scotia
CD 31 #33 "Glissade"
Way too many other small boats


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[tjr818]

Now, today, we’re looking forward to seeing many of the CD Maine summer cruise gang today at cocktail hour in Northeast Harbor.

We are in the Art Fair on the grounds of the Bar Harbor Inn, today and tomorrow. We can’t leave or we would head over there. Google maps says that it is a four hour walk! Sad to be so close and yet so far.

[Boyd]

Hi:
I just posted on your more recent question.

You have several issues.

First,your electrician seems to have connected all three batteries to the controller directly. Not a good idea. I suggest having the two house batteries connected directly to the solar controller and getting a Xantrex Echo Charger (about $100 and simple to install) for the starting battery. That way you set you 1/2/all switch to the house battery. The only time you switch to all or the start battery is when the house is too low to start the engine.

I use this strategy for battery management:

My switch is always set to house. I start the engine on house. If the house is too discharged to start the engine, I switch to all and crank it. I run the engine until the battery monitor reads nearly full. I stop the engine and switch back to house. If I restart the engine then the house is getting charged directly and start is getting charged thru the Echo Charger. The Echo Charger taps excess voltage off of the charging system and feeds it to the start battery. It stops the start battery from back feeding the house. I typically would never start the engine with the start battery. Its a misnomer to call it that. I prefer "Spare Emergency" battery. The solar panels will then top off both the house and start battery. On a good day I get 10 hours of charging and the system goes to float on the solar charger.

I have 4-100 watt solar panels on my boat as mentioned in my earlier post. They will just about keep up with the refrigerator load.

A good battery monitor is Victron BMV 712 or 7200 by Victron (about $150 or $200). Without one your running blind. A simple microvolt meter is pretty nearly useless.

Sorry to hear you have AGM's. Fair warning, I had them once and really dont like them. For the money and performance 6volt Golf Cart batteries are the best cost/value option and you dont have strange charging cycle problems. Yes you do have to water them, but thats easily handled with a watering system or a turkey baster. I currently use standard 27 deep cycle batteries and they are dirt cheap at Costco. My whole bank cost about $400. Old technology does work better some times.

But your stuck with them so...

If your alternator is an internally regulated one then its basically an automotive taper charger. It tapers the charge over time and its going to need to run for VERY long hours to get your batteries to full charge. Its unlikely that type of alternator will ever fully charge your batteries. You would need an externally regulated high output alternator ($$$ and your engine will need new alternator mounts) to even come close to floating your AGM's after a deep discharge. 130 watts of solar is not going to do it in even a 10 hour day.

I basically agree with Oddessy on their assesment.

An option is a Honda 2000i on board. You fire it up and it will feed a battery charger. Its light and is a great backup if you have the room to store it. They even make a 1000i but I doubt it has enough output for a good battery charger.

Your other option is to hook to shore power a lot of time.

Boyd
s/v Cat-A-Tonic
Prout 34
Fort Lauderdale, Fla.

[jen1722terry]

Thanks so much for the thoughts, Boyd, and we apologize for being late responding. We were busy with haul out and lay up for the winter up here in Maine.

Yes, we may have gotten sold a bill with the Morningstar Prostar. We'll think about it over the winter and maybe replace it in the spring after we add a new, larger solar panel (at least 300 watts, 400 if we can fit it).

We have no idea what kind of regulator we have on our alternator. The engine was new last year, but Beta Marine doesn't give any info on the regulator (I asked them).

We're presently looking (again) for a competent marine electrician who can go over the whole boat and recommend a correct solar panel/controller/charger/battery combination that will meet the needs of a couple who live aboard full time for the summer. Money well spent if we can find such a person.

thanks again for taking the time to post such a thoughtful, helpful response.

Jenn and Terry

[Jim Walsh]

https://marinehowto.com/about/
Perhaps our esteemed contributor Maine Sail can be of service.

[Boyd]

Hi:

The Morningstar Prostar is fine. I have a Morningstar controller also. Its the way your system is set up that I suggest changing.

If your alternator is a factory supplied standard, then its 99% likely an internally regulated type which will not be set to the correct voltage or charging profile for your batteries. It will eventually destroy them. The internally regulated alternators are designed for liquid lead acid starting batteries not the deep cycle type we typically need on house banks or the more sophisticated AGM's .

An externally regulated type generally has a separate controller with settings for charge profiles. Check with online with companies such as:

http://www.hamiltonferris.com/categories/Alternators/2

http://www.balmar.net/balmar-technology ... egulation/

for solar and refrigeration check:

https://coastalclimatecontrol.com/index ... nning.html

Keep working on it. You will get the system functioning. One consequence of owning a boat is you learn a lot about systems you never intended to know much about.

Keep Sailing
Boyd
s/v Cat-A-Tonic
Prout 34
Fort Lauderdale, Fl