Charging a Deep Cycle Bank

[Tar34]

I am looking at installing two 6v golf cart batteries to create one 12v house bank. One concern I have is the ability of my 55 amp alternator to charge this bank to at least 80%. The batteries I want to install will each have a rated capacity of 215AH. I would consider a higher rated alternator as long as it is plug and play. I am also in the market for a battery charger which will handle this 12 volt bank plus a 12v dedicated starting battery. I want to keep this as simple as possible so your collective insight and experience is most welcome. Thanks in advance.

[edwardc]

The amp-hour ratings of batteries in series don't get added. What you end up with is a 12v bank with 215 Amp-Hours.

I'm currently charging two 197 Amp-hour 12 V batteries in parallel ( for a total of 394 A-H) with a Mando 55 amp alternator. I don't have a smart charger (yet), just the stock regulator. Measurements I made summer of 2012, using a battery charge monitor, suggested that I needed about 4 hours of engine run time at cruising rpms (~2000) per day to make up our daily consumption of about 50 A-H per day. (cold plate system accounts for a lot of that)

This is way too much run time for any extended cruising or passage making, but is acceptable for just potting around here on the Chesapeake, where fuel is usually not very far. For extended cruising, I'd like to get that down to 2 hours runtime per day. I think that is doable with the 55A Mando if I convert it's regulator to a smart charger, but I'll probably go the whole way and put in a 100A Balmar and a Balmar smart charger/regulator. You'll never get 100A out of it given the slow rpms of the A4's accessory drive, probably not much more than 50A, but it'll be running much cooler and not as close to it's limits.

As always, YMMV

[Tar34]

Edward
Yes in series, amps is not doubled. I am unfamiliar with this Mango Alternator you speak of. I believe what I have is a 55 amp Motorola. I'll have to double check. Does a smart charger see the two 6v batteries in series as one battery? I assume it must. I'm adding an auto pilot this winter so my entire minimalist program must necessarily come to an end. I have been getting by on one crippled 100Ah deep cycle and one 100Ah starting battery. I've nursed this program for three years mostly on my alternator until very recently when I added shore power and new AC Panel. I have not as yet selected a charger for the boat, instead relying on a "smart" portable charger. I have a Tartan 34c, so my choice of auto pilot is a debate in itself. Laden at 13,000 lbs displacement, it seems the less expensive choice may not be robust enough and the next option a budget buster. So if we can expand on the Mango, I'll search the forum and look for comments on this unit. Is there a specific model number or the A4? Is there a benefit changing out from a properly running Motorola?

[ndutton]

I agree with everything Ed offered. You have to produce more power than you consume daily or eventually you'll end up in dark territory. You may manage this on the supply side or the consumption side or a combination of both. Big banks will buy you some time but for an extended cruise it's the daily supply-demand balance that tells the tale. One other caveat: it's generally accepted that alternator output should be in the area of 1/4 battery bank capacity.

The big consumer on my boat is the refrigeration. My only charging system is the engine alternator - no solar or wind generator. Battery banks total about 400 amps not counting my dedicated engine starter battery, alternator capacity is 100 amp but as Ed pointed out, at our RPM 50A is the best I can hope for.

I use my boat two different ways, either daysails or 3-4 day Catalina weekends. My banks are sufficient to carry me through two full days without replenishment (no more than 50% depletion) although I run the engine daily on Catalina excursions for an hour to help a little but I'm operating at a deficit for sure. If I were away from the slip for more than 4 days I'd shut down the fridge in favor of tried and true ice (demand side management).

L.E.D. cabin lights went a long way toward power conservation. With all the lights on I went from 10 amps to 1.

[Tar34]

Yes, a deficit for sure. LEDs for sure on the list. I have already decided a solar panel will be a big part of the "new" system. I'd like to concentrate on the alternator. You have an 100amp. Can I assume modifications of pulley and belt size? I'll look through the forum.

[ndutton]

No modification to pulleys or belt, the 3/8 belt does fine but remember the best I'm getting out of the alternator is 50 amps. I don't have the fancy monitors like others, the alternator output was measured on a dyno test @ 2000 RPM at a marine alternator shop.

One thing that may help belt longevity is the automatic tensioner. With it I'm not over tensioned which benefits the auxiliary drive and alternator bearings too.

[hanleyclifford]

You can get very serious about juice production if you want to:

[Tar34]

Alternator sizing: While our 55 amp Mando didn't quite meet the rule of thumb for alternator sizing (theoretically we needed a 77 amp alternator with our new set of batteries), I left the Mando installed, if only to see how it would perform. Not surprisingly, it would more or less max out at 50 amps for a few minutes when we ran the batteries down at anchorage, but most of the time, the output remained between 10 and 25 amps (depending on battery condition). However, whenever we attempted to use our rather dated refrigeration unit, the Mando spent most of its time between 40 and 50 amps.

Above from Don M sticky:

I have never seen this type of output on my ammeter in the cockpit. Where is this output measured? Sorry for my profound ignorance but that seems to me far more than I could expect to read on my ammeter. I know my house bank is needy but 50 amps? I want one of those!!!! Mango Model number Please....

[ndutton]

Remember too that getting the full output from a big alternator means the battery banks are seriously depleted which is bad practice in terms of battery life.

[Tar34]

You can get very serious about juice production if you want to:

That's what I'm talking about...I can feel you guys sucking me in. I'm not rebuilding the furniture .... yet.

[joe_db]

There are quite a few threads about ammeters, voltmeters, and how to hook them up.
That said, here is the fundamental issue: The stock A4 setup will NEVER be all that good at charging big banks because of the pulley ratio. Moyer sells two different upgrade alternators and some of us have done some FleaBay engineering with them as well. If you look at the output vs. RPM curves, no matter if it is a 90 amp or 120 amp alternator it is not likely to get past 60-80 amps at *most* at RPMs A4s usually run at. Charging at idle will be very minimal.
IMHO here is the upgrade in order:

read THIS thread http://www.moyermarine.com/forums/sh...ight=voltmeter

1. Replace 35 amp with 55 amp if you haven't done so and then:
2. Replace the long runs of wire that are common with a short thick wire from the alternator to the battery switch, battery, or starter terminal depending on how you want to do it.
3. Replace the standard center-0 ammeter with a voltmeter.
4. Add a shunt-type ammeter in the alternator output circuit.
5. Add a shunt-type ammeter that is center-0, digital with + and - amps, or an amp-hour meter in the house battery circuit.
6. Add an adjustable or 3-stage regulator.
7. Get the 120 amp alternator from here or ??.
8. The ultimate - get the brackets made to drive off a big pulley on the crank

[Tar34]

There are quite a few threads about ammeters, voltmeters, and how to hook them up.
That said, here is the fundamental issue: The stock A4 setup will NEVER be all that good at charging big banks because of the pulley ratio. Moyer sells two different upgrade alternators and some of us have done some FleaBay engineering with them as well. If you look at the output vs. RPM curves, no matter if it is a 90 amp or 120 amp alternator it is not likely to get past 60-80 amps at *most* at RPMs A4s usually run at. Charging at idle will be very minimal.
IMHO here is the upgrade in order:

read THIS thread http://www.moyermarine.com/forums/sh...ight=voltmeter

1. Replace 35 amp with 55 amp if you haven't done so and then:
2. Replace the long runs of wire that are common with a short thick wire from the alternator to the battery switch, battery, or starter terminal depending on how you want to do it.
3. Replace the standard center-0 ammeter with a voltmeter.
4. Add a shunt-type ammeter in the alternator output circuit.
5. Add a shunt-type ammeter that is center-0, digital with + and - amps, or an amp-hour meter in the house battery circuit.
6. Add an adjustable or 3-stage regulator.
7. Get the 120 amp alternator from here or ??.
8. The ultimate - get the brackets made to drive off a big pulley on the crank

Thanks Joe, I was looking at the Moyer API offerings, is that the Mango he speaks of? Second, searched around for a suitable voltmeter to replace my ammeter in the cockpit to no avail. I feel I'm getting into the weeds here with too many questions. My plan was simple, linear and doable. I'm starting to lose focus. I will look through your attached thread.

[ndutton]

On this boat and the last I decided I wasn't going to live like a caveman. I try to bring a little civility and class to the party. I don't take it as far as Grey Poupon but I eat off real china (not paper), use real utensils (not plastic), like my water to flow from the faucet when I turn it on and don't live out of an Igloo cooler. That means I consume power and I'd better have a way to manage it or the necessary equipment will cease to function.

This is the first boat I've owned with refrigeration. For me the benefit is worth the cost and power hit. There are ice cold Pacifico Clara's waiting for me at all times.

[joe_db]

Moyer has one

http://www.moyermarine.com/cgi-bin/shopper.cgi?search=action&category=GAUG&keywords=all&template=Templates/B000_storebuilder.html

Here is what I have:

Thanks Joe, I was looking at the Moyer API offerings, is that the Mango he speaks of? Second, searched around for a suitable voltmeter to replace my ammeter in the cockpit to no avail. I feel I'm getting into the weeds here with too many questions. My plan was simple, linear and doable. I'm starting to lose focus. I will look through your attached thread.

[sastanley]

Tar34..

There are many, many options as already noted.

One place the standard A-4 charging system is also deficient was the common practice of those darn ammeters in the cockpit..while an important device, it really cuts down on the efficiency of the charging circuit, as the charge from the alternator has to go all the way up to the gauge, thru it, and back down to the battery bank..(and usually I think the wires are undersized, mine had 8 or 10 gauge wire) - this is one reason why Joe mentioned a simple volt meter in place of it. You eliminate that long charging run, and if you want to keep it simple, run the alternator output wire wherever the other end of the ammeter ended (common on the 1-2-all switch maybe?) - Tap the voltmeter into hopefully the purple circuit which should be on the back of your gauge panel, and if the voltmeter is reading more than 12.6v when the engine is running, you know the alt. is charging. Those digital gauges he showed you are cheap and effective (I have a few on my fleaBay watch list), if you really want to track the data.

I simply added another group 29 marine battery, in parallel (122 Ah each), for a total of 245 amp hours on the house side. It was less hassle for me than 6v batteries. I am using the old stock 35a Motorola, but I have modest power needs..LED everything and no refrigeration. Sometimes my wife likes to charge her gadgets or the laptop though. The other thing nice about that is if one battery goes bad, I can eliminate it from the circuit and still have 122Ah to work with.

At any rate, for not a lot of money, I think we can help with some recommendations to improve what you got without throwing a high amp alternator at the problem..there are likely other losses present in the system we can correct/modify to increase charging efficiency.

Being down in the weeds is OK..this can be a complex issue to sort out, and you need to explore many options to decide which one works best for you. The nice thing about discussion forums is it doesn't cost any money to experiment.