Solar and alternator charging on passage observations and questions

[monte]

Hi
We recently made our first multi week passage from the canaries to Martinique which was the fist chance to seriously test our battery and charging systems. Prior to this it was all theoretical and quite different to our actual observations.
Our power budget was around 280Ah/ day for passage making and around 150Ah at anchor.
Actual power usage was closer to a consistent 18Ah continuous, so more like 420A/day. This was with the AP, plotter, 2 fridges, computer, radar on all the time.
On the charging and storage side, we have 1.2KW of solar and an 840Ah flooded cell battery bank. Also the engine has an 80Ah (I think) standard yanmar alternator.
The solar can put in up to 85 Ah, however it's usually closer to 60 in full sun.
We found we had ample power in the first week due to starting with full batteries and putting enough back in with the solar, but then the batteries started to drop below 60% and voltage dropped to 12V so we had to charge using the engines for a couple of hours each night. This usually bought the batteries back up to 70%, back down to 60% around dawn and then the solar started putting enough back in for the day and storing enough till midnight! when it would be back down to 60%.
One of the reasons the solar didn't produce enough power was most mornings were cloudy. The clouds would usually clear a bit by mid day, but by 3pm the solar started to become shaded by the parasailor. It was dark for approximately 12 hrs.
So a couple of questions I have are,
I know 12V is much lower than 60%, but assumed this was low due to the constant power draw and if they were at rest for an hour the true voltage would have been quite a bit higher. Is this assumption correct?
I know that battery monitors aren't always accurate with SOC % but this is really all we had to go on, and I know they can get quite a bit out over time. Ours did seem fairly consistent with it's readout though.
When we started the engine to charge, I found 1200RPM in neutral was enough to put in around 80 amps and any more revs didn't increase the input, but after 30 minutes the input would drop to 40 amps, even though the batteries were still only 60%. Is this because the voltage went up to 13V and the alternator has a regulator to cut back the input? This was a bit frustrating as 80amps continuously would have charged the batteries much faster and meant half the engine running time
Hopefully these observations will assist anyone else and also hopefully someone can explain the alternator output question.
Thanks
Monte

[nigel1]

No expert here, but your assumption that the voltage would have risen as the batteries rested is correct.
Couple of questions for you.
Did you have the radar on transmit continuously, or on stand by. Only running on TX for a few minutes an hour really cuts down on the amps used.

Chart plotter: any need to run this continuously? I tend to turn mine off when off the coast, and use a GPS for fixing and plot on a paper chart. For Ocean passages you can get plotting sheets to keep a check on progress.

[Maine Sail]

Originally Posted by monte

Hi
We recently made our first multi week passage from the canaries to Martinique which was the fist chance to seriously test our battery and charging systems. Prior to this it was all theoretical and quite different to our actual observations.
Our power budget was around 280Ah/ day for passage making and around 150Ah at anchor.
Actual power usage was closer to a consistent 18Ah continuous, so more like 420A/day. This was with the AP, plotter, 2 fridges, computer, radar on all the time.
On the charging and storage side, we have 1.2KW of solar and an 840Ah flooded cell battery bank. Also the engine has an 80Ah (I think) standard yanmar alternator.
The solar can put in up to 85 Ah, however it's usually closer to 60 in full sun.
We found we had ample power in the first week due to starting with full batteries and putting enough back in with the solar, but then the batteries started to drop below 60% and voltage dropped to 12V so we had to charge using the engines for a couple of hours each night. This usually bought the batteries back up to 70%, back down to 60% around dawn and then the solar started putting enough back in for the day and storing enough till midnight! when it would be back down to 60%.
One of the reasons the solar didn't produce enough power was most mornings were cloudy. The clouds would usually clear a bit by mid day, but by 3pm the solar started to become shaded by the parasailor. It was dark for approximately 12 hrs.
So a couple of questions I have are,
I know 12V is much lower than 60%, but assumed this was low due to the constant power draw and if they were at rest for an hour the true voltage would have been quite a bit higher. Is this assumption correct?
I know that battery monitors aren't always accurate with SOC % but this is really all we had to go on, and I know they can get quite a bit out over time. Ours did seem fairly consistent with it's readout though.
When we started the engine to charge, I found 1200RPM in neutral was enough to put in around 80 amps and any more revs didn't increase the input, but after 30 minutes the input would drop to 40 amps, even though the batteries were still only 60%. Is this because the voltage went up to 13V and the alternator has a regulator to cut back the input? This was a bit frustrating as 80amps continuously would have charged the batteries much faster and meant half the engine running time
Hopefully these observations will assist anyone else and also hopefully someone can explain the alternator output question.
Thanks
Monte

Monte,

You really ought to lose the Hitachi alternators if you want effective alternator charging on a large deep cycling bank.

Those internal Hitachi regulators have a temp gradient built in to the regulator which drops/reduces regulated voltage to prevent the alt from over heating. They do this because they are really automotive duty alternators that can't really handle charging large cycling banks. This voltage gradient does two things;

*Leads to chronic under charging due to the low reduced voltage output

*Leads to painfully slow charging. Voltage is the pressure that allows current to flow into the bank. Low charge voltage = lower charge current.

BTW we just finished a charter on a Lagoon 420 and had the same exact issues. Highest alternator voltage we ever saw, over 10 days, was 13.2V..... Best I could get out of the house alt, amperage wise, was about 24A, when hot, into a 700Ah bank... BTW the 6V battery bank was new on this boat last year and they were already destroyed.

[BobH260]

I think the stock alternator was part of the problem. The stock alternator will heat up and reduce its output. Did you try letting it cool off and running the engine say a couple of hours later to see if the alternators output came back up ?
Investing in a high output alternator with external regulator with voltage sense wire direct to the bank, and battery/ alt temp probes would make a big difference in how quickly you can bring the bank back up.
I would have run the engine a couple of times in the morning trying to get all the bulk charging done then use the solar to top up the battery bank when the battery acceptance has gone down.
I'm sure the experts will have lots of good suggestions, just a few thoughts based on my experiences, good luck, Bob

[monte]

Nigel, yes we pretty much had all systems on continuosly. There were a lot of squalls we were tracking on radar most days. Occasionally I set it to do a scan every 15 minutes to reduce consumption which works well. We leave the plotter on mainly to view radar and AIS. Yes we could have reduced consumption by around 5Ah if we tried.
Maine sail, interesting regarding the alternator temp. Do you think running one engine for 30 mins or so, then alternating between engines would improve output?
Btw, no need to charter, next time you feel like spending a week on a cat in the sunshine your welcome aboard Sephina! Just bring your multimeter

[HappyMdRSailor]

Originally Posted by monte

Nigel, yes we pretty much had all systems on continuosly. There were a lot of squalls we were tracking on radar most days. Occasionally I set it to do a scan every 15 minutes to reduce consumption which works well. We leave the plotter on mainly to view radar and AIS. Yes we could have reduced consumption by around 5Ah if we tried.
Maine sail, interesting regarding the alternator temp. Do you think running one engine for 30 mins or so, then alternating between engines would improve output?
Btw, no need to charter, next time you feel like spending a week on a cat in the sunshine your welcome aboard Sephina! Just bring your multimeter

Ha!
BRILLIANT!

[herbhunt]

It seems likely that the alternator is overheating as posted earlier. As you have a cat I would suggest upgrading an alternator on one engine to a higher capacity with an external charge controller. By using only one engine to charge (you imply you are running both while charging in a post earlier) and a higher output alternator you will not only reduce total engine hours but also run the engine at a higher load which will reduce total fuel consumption and engine wear.

[herbhunt]

And I should have added check the ventilation to the engine compartment to ensure that the temperature is not so high that it will inhibit any alternator from working properly.

[Moontide]

Might want to consider getting a Honda generator to use. We have a 12kw generator but don't need all that power 99% of the time. Bought a Honda to supplement the solar when needed as I figure better to wear out a $1,000 generator than a $20,000 one.

Yanmars have a reputation of building up carbon on the valves if they are not run hot enough. That can happen when running with basically no load. They also cost a bit more than a Honda when it comes time to replace them.

Of course the attendant issue is storing gasoline aboard.

Bill

[monte]

Yes thanks. We just run one engine at a time. Usually the starboard one as it heats water as well. Its likely to be more than a year before we do a long passage that requires another charging source as the solar keeps the batteries over 90% for day sails and anchoring. We may do a few overnighterls but not enough to get the batteries down near 70% again. I'd like to try running the port engine then the starboard when the output drops to check if it is a temperature thing. I'll look into changing the alternator if it's not too major a job.
Thanks again for the feedback

[hellosailor]

monte-
You're lucky MS is a pro and has Fluke multimeters that can be switched for both Imperial Volts and Metric Volts. Here in the Colonies, Imperial Volts are the standard but since you guys have everything in metric...our regular meters would be confusing to you. (VBG)


Alternating engines every 1/2 hour (that's about two centidays, metric) would give you the benefit of having a "cold" alternator twice, but you'd probably need to rest both engines for another couple of hours to get them back down to ambient temps again. Engine room equipment tends to get hot then stay hot.
But using both engines probably is actually digging a deeper hole, as you are putting wear on two starters, two alternators, two exhaust systems, two sets of engine internals. A substantial amount of the wear on all of those things comes from the shock loads of starting, making that an expensive way (long term) to buy more power, as opposed to installing at least one proper heavy duty alternator and regulator.

[Stu Jackson]

Here's Maine Sail's long version of the Hitachi alternators. They do NOT heat up, they just never get to a good charge profile. Here's why:

Hitachi/Yanmar Alternators: (by Maine Sail)

Some alternators though, such as those made by Hitachi and found on Yanmar diesels, are dumber than a pound of beetle poop. Actually, to the alternator, they are pretty smart but to your batteries and the speed of charging they are flat out stupid. Why?

Hitachi alts with dumb regulators, and some others, limit voltage but also reduce voltage based on alternator temperature. This is a self protective feature installed in the internal dumb regulator to prevent the alternator from cooking itself. Remember voltage is the pressure that allows more current to flow. So, if we reduce the absorbtion voltage, then we also reduce the current the alternator is supplying.. The battery simply will not accept the same current at 13.4V that it did at 14.4V and as a result the alternator will run cooler. What do you suppose this does to your batteries over time.......?

The problem is that when cold you will get 14.3V to 14.4V out of the Hitachi but as the alternator heats up the dumb regulator begins to reduce the CV/voltage limit based on the alternators internal temperature. It is not uncommon to find a Hitachi alternator at 13.4V when hot. This is REALLY, REALLY DUMB....

If you have a dumb regulator, and notice the voltage dropping, it is likely a temp compensated dumb regulator. Get rid of it or plan to buy new batteries more often.

If you have a temp compensated alternator or a Hitachi alternator on a Yanmar you really are in dire need of external regulation if deep cycling a larger battery bank.

This is from:

Musings Regarding External Regulation - SailboatOwners.com

and this, too:

http://www.cruisersforum.com/forums/...on-125843.html

[roland stockham]

Hi
Think you might find that for the next trip you can significantly reduce power use. 400+ Ah/day is a lot and in the range where an onboad genset may be an economical solution. As you get used to life aboard away from marinas many people find they use less water, less hot water, open fridges less etc. All this adds up to a drop in demand which is significant.

The other thing is that you do not say what your batter bank is. The charge acceptance rate is the main controlling factor for lead acid batteries. It is proportionally higher for things like AGM (at the expense of higher cost and shorter life) but will always be in the range of 10-15% of 10hr capacity rate so a 400Ah flooded wet cell will not be happy with a charge rate much above 40A. You can push this up a bit by using high voltages but only so much. At 15v you risk blowing connected electronics so most people stick to 14.6 - 14.8 as max voltages. Even a very small change does make a difference so its worth checking the actual voltage at the battery terminals. If this is low that is why you alternator output is down. From what you say in your post it would seem that you are looking for a steady charge rate of about 80A for bulk charge from 50% to around 75-80%. This would reqire a battery bank of between 800 and 1,000 Ah depending on technology.
I am a assuming you have good 3 step regulators on both alternator and solar charge circuits. (If not fit them and your problem will be solved!)
The other possibility in banks that size is to look a NiCaD batteries. They are available as flooded wet cells and normally used in the pow industry for things like emergency power supplies to hospitals. More expensive to install and requires different charge technology but they have the following advantages.
Very stable voltage output down to about 10% charge
No sulphation so very tolerant to deep discharge and can be run to flat regularly with no problems with 'winter storage' as they prefer to be stored discharge
20yr+ service life.
Very high charge/discharge rates. I really mean high a 500A/h bank will take a charge rate of about 500A to 60% and will not suffer the 'drop off' lead acids do. Charging is by constant current to full charge so the same 500Ah bank would probable be able to take an 80A charge rate right up to full charge.

The combination of stable voltage and deep discharge means that you can use a smaller capacity bank. However they are physically larger per Ah capacity so this tends to cancel out

If they made smaller batteries I would fit them but on my boat (35ft) they ar just physically to big.

[sailorboy1]

Originally Posted by monte

On the charging and storage side, we have 1.2KW of solar and an 840Ah flooded cell battery bank.

The solar can put in up to 85 Ah, however it's usually closer to 60 in full sun.

One of the reasons the solar didn't produce enough power was most mornings were cloudy.

Well these don't seem right to me. I have 460AH batteries and a 290W of solar and I can get 60AH charge a day in the Northeast, even on most partly cloudy days.

[monte]

Thankyou and Thankyou, Roland, the battery bank is 840Ah. Yes we can reduce consumption. We didn't use much water and the watermaker just draws 24Ah for 65l. We probably ran it for an hour/ day. I'm not sure about the 3 stage regulator, I don't really understand how the factory alternators work or are wired. Maybe that's an option though..
Sailorboy, 85Ah is 85 amps per hour. We were probably averaging 50Ah for 6 hrs on a good day due to cloudy conditions, so putting in 300Ah with a shortfall of 130Ah.