Actual power budget of cruising monohull?

[a64pilot]

The issue is most charge controllers go into float prematurely, you need to determine if your acceptance rate indicates a full charge, then let it go into float. I won't be surprised too much if mine never go into float, but why wait until float to use "stuff" as long as your making in excess of what is going into the batteries, use the excess.
I draw about 15 amps more or less continuously, sometimes less, depending of course on what all is on.
I'll know I guess in some months if 1,000 W of panels can keep up with that or not, and if it can fully recharge my bank, or not. I likely won't really know for another year, by then we will really be out doing it, and things settled down into a routine. I don't think our two weeks a yr vacation and weekends are very telling.

[Copacabana]

Originally Posted by a64pilot

I draw about 15 amps more or less continuously, sometimes less, depending of course on what all is on.

15ah x 24 hours = 360ah per day of energy comsumed...

There's your problem!!

[donradcliffe]

Most people who talk about the solar topping their batteries up by noon are talking about when they are at anchor, not on a passage.

[Suijin]

Originally Posted by a64pilot

I draw about 15 amps more or less continuously, sometimes less, depending of course on what all is on.

Are...are you serious? 15 amps continuously? What are you running on your boat? lol

I don't think I've ever seen my draw go above 5 amps, and that is with the fridge compressor running, lights on, stereo going...I don't have a water maker, or a washing machine, or AC, but those are hardly continuous anyway.

Ok, so I can now see why you want a generator, lol.

[robert sailor]

Originally Posted by a64pilot

The issue is most charge controllers go into float prematurely, you need to determine if your acceptance rate indicates a full charge, then let it go into float. I won't be surprised too much if mine never go into float, but why wait until float to use "stuff" as long as your making in excess of what is going into the batteries, use the excess.
I draw about 15 amps more or less continuously, sometimes less, depending of course on what all is on.
I'll know I guess in some months if 1,000 W of panels can keep up with that or not, and if it can fully recharge my bank, or not. I likely won't really know for another year, by then we will really be out doing it, and things settled down into a routine. I don't think our two weeks a yr vacation and weekends are very telling.

Wow, your out of our league for sure. Generally we are drawing no more than an amp or two until the fridge kicks in and then it's up to 7 or 8 amps. We might see 15 plus with the watermaker on for a short time in the afternoon. I also have a Sterling controller on my engine alternator that will allow up to 14.8 volts on absorption, Solar will only allow 14.6 on absorption so I like to hit lead acid batteries on the harder side, it's worked out well for me in the past but you have to really watch the water as the batteries will use more at higher voltages. I have fooled around with starting the engine after the solar controller kicks the batteries to float stage to see how much longer the batteries can accept a higher charge rate and while it does allow a higher rate for a bit longer it's never really that much and it's down to less than 5 amps. Panels seem to float between 3 and 4 amps. In the past I used to discharge to 50% and charge back to 80% because it took so long to get that last 20% into the batteries but dropping our daily use and having more solar power means I'm always in the top part of the batteries capacity and with any luck I should get some extra time out of them. Even in the old days I'd get close to 5 years out of my batteries and I might only equalize them once or twice a year and they were never really fully charged the rest of the time.

[dwedeking2]

He just wants to be able to see kayakers. Safety First!

[Paul L]

Originally Posted by donradcliffe

Most people who talk about the solar topping their batteries up by noon are talking about when they are at anchor, not on a passage.

Agreed. Solar is not enough for us while on passage. Between the added load from chart plotter and AP 24hrs and the sails shading the solar we need to supplement with genset everyday or every other day typically.

[robert sailor]

We are the same but we never run the chart plotter more than an hour a day, same with radar, not necessary as long as you keep a good watch. If we see another boat then we'll turn it on. The autopilot can be a real suck 24/7 and we ended up using our back up CPT when we crossed the Atlantic and it made a huge difference in how long we had to run the engine, Yes your spot on we were getting lots of shading on the solar panels which really made a big difference in our power management on passages. No problem right now in the Caribbean, passages are very short and I don't even bother with power and we run the big autopilot all the time. The only time we are foot loose with lots of solar power is at anchorage.

[noelex 77]

Originally Posted by Paul L

I'm with MarkJ on this. I think Mainesails analysis is a bit skewed to the negative side.

Maine Sail is right in my view. With lead acid batteries it takes a long time to charge the last few percent.

Figures differ depending who you believe, but if you want to get a lead lead battery to reach a true 100% charge it is going to take a positive charge rate for something like 12 -24 Hrs, some would say longer.

Lead acid batteries like to get to 100% charge occasionally, but most chemistries will have a long and happy life if you can charge them to 90-95% and keep the discharge rate as low as possible. A 90-95% charge level is achievable in a reasonable time frame.

The exception is some AGM batteries which need to reach 100% regularly (say once a month) to achieve a good life. This is fine if you often plug into shore power but it almost impossible achieve a true 100% under solar power on a boat that is being used. Generator charging is generally terminated around the 80-85% level where the charge rate starts to severely taper.

Many people define 100% charged as when the regulation drops down to float. This is sometimes called the "Cruisers 100%". For many purposes the battery capacity at this stage is close to fully charged so the definition is not unreasonable. But if want to be precise the battery capacity can be increased a little more, but it will take many hours to reach a true 100% charge.

To get the longest life out of lead acid batteries the most important factor is the level of discharge. Keep the discharges as shallow as possible.

However, it is worth bearing in mind that the least expensive lead acid battery bank is where the batteries regularly reach somewhere around 50 % SOC. If you keep your battery bank to around 20% discharge it will last longer, but the annual cost will be higher than a smaller battery bank discharged more. (These numbers will vary with different models of battery but serve as a rough guide for deep cycle batteries)

[Paul L]

Originally Posted by noelex 77

Maine Sail is right in my view. With lead acid batteries it takes a long time to charge the last few percent.

Figures differ depending who you believe, but if you want to get a lead lead battery to reach a true 100% charge it is going to take a positive charge rate for something like 12 -24 Hrs, some would say longer.

Lead acid batteries like to get to 100% charge occasionally, but most chemistries will have a long and happy life if you can charge them to 90-95% and keep the discharge rate as low as possible. A 90-95% charge level is achievable in a reasonable time frame.

The exception is some AGM batteries which need to reach 100% regularly (say once a month) to achieve a good life. This is fine if you often plug into shore power but it almost impossible achieve a true 100% under solar power on a boat that is being used. Generator charging is generally terminated around the 80-85% level where the charge rate starts to severely taper.

Many people define 100% charged as when the regulation drops down to float. This is sometimes called the "Cruisers 100%". For many purposes the battery capacity at this stage is close to fully charged so the definition is not unreasonable. But if want to be precise the battery capacity can be increased a little more, but it will take many hours to reach a true 100% charge.

To get the longest life out of lead acid batteries the most important factor is the level of discharge. Keep the discharges as shallow as possible.

However, it is worth bearing in mind that the least expensive lead acid battery bank is where the batteries regularly reach somewhere around 50 % SOC. If you keep your battery bank to around 20% discharge it will last longer, but the annual cost will be higher than a smaller battery bank discharged more. (These numbers will vary with different models of battery but serve as a rough guide to deep cycle batteries)

Isn't dropping to Float a good indication if the transition is based on the battery accepting in the order of .5% amps of the batt capacity at acceptance voltage? It might not be exactly 100%, but it is close enough for full-time liveaboards. Iny case I have a nominal 600ah bank and often see the solar at 14.6 - 24.7v and 4 a in the afternoon. ( with lots of excess solar available)
Sure, the defaults on most charge regulators are way off, but decent solar controllers are programable.

[tomfl]

Originally Posted by MarkJ

I agree with Suijin. No generator needed. I have used my engine for electricity for less that 10 hours in the last year. That's less than 1 hour per month.




I think this 1 paragraph sums up many "rules":
Solar panels wattage should roughly equal house battery amp hour capacity.
You should be 100% full by 12 noon or 1pm. (10am is very good)
You get to know your system and know when it should hit 100% or you can 'feel' the problem.
Only charge battery operated stuff when you are 100% and just wasting sun.
Use your high draw stuff last.

Since I use flooded batteries I will limit my comments to that type of battery; noting that this is the type of battery most folks use.

First off getting to 100% charge may not have the same definition for everyone. There are different instruments and shunt installs that will give a different reading on the same batteries, especially when the charge gets above say 95%. While it is probably correct to say flooded batteries never, or almost never, get to 100% this is really meaningless. Once you get above 95% or higher you really don't need to worry on a daily basis, and lets not get into stuff like equalizing on a monthly basis at this point. It is silly to get too hung up on getting to 100% if you are using the definition an EE guy would use.

What is much more important than getting a 100% charge is how deep the discharge is on a regular basis. Rule of thumb is you should not discharge below 50%. Even discharging to 50% is much more damaging to batteries than only recharging to ~95% or so. This is why your house battery bank is suppose to be at least twice (and hopefully a little more) your daily power usage.

When you are charging your house bank at first you may be putting in lots of amps. On my boat on a sunny cool day I have seen 24 amps going in to start, but it quickly will drop as the bank charges and the batteries can not absorb more power. Once I get over 90% charged the reading will be around 5 amps going in. At this point I am dumping maybe 20 amps of power and can use an inverter to charge up my toys or other power intensive activities; including opening up the fridge/freezer. Of course using things like LED lights reduces usage; but not nearly so much as being careful about opening up the fridge which may require more power to get the temp back to where it was than leaving an LED on all night.

A lot of this is what I will call life style choices. I use things like Luci Lights instead of the wired lights on my boat, not so much because I think it saves a lot of power but because when I move around the boat I have to the light move around as well.

Just as an aside I have never noticed my AP uses a lot of power. But I suspect that is because I tend to not turn it on till I am on course and have trimmed the sails so the boat is basically balanced and the AP is not really working very much. I have seen it go thirty minutes or more with no course corrections. On a boat with a heavy weather/lee helm the AP would have to work much harder.

I still am shocked at some of the comments I see from folks who never seem to have enough power when they have huge solar arrays and battery banks. Like Mark I have run my Honda 2000 less than ten hours last year, and that was because I follow the rule that gas engines should be run at least once a month for 20-30 minutes, not because I needed to charge the batteries.

If you get a solar array and battery bank with watts and amps roughly equal and take care to match the components and use the right size and color wires to connect things up along with taking care to not waste power a 500 watt array and 500 amp bank should be more than enough for your needs.

[robert sailor]

I won't argue that it probably does take a long time to get a full 100% charge but for everyday field use its just not required as even lower numbers will give you long battery life, in my experience anyways. Right now my batteries have never been treated better, way better than any time in the past years.

[noelex 77]

Originally Posted by Paul L

It might not be exactly 100%, but it is close enough for full-time liveaboards.

I agree. When entering float, if the charge parameters are set correctly, the batteries are close to 100% charged. It is often called the "Cruisers 100%" for good reason. However, if you want to be accurate it is about 90-95% charged, (some would put the numbers a bit lower). It is not 100%. The extra 5-10% takes a long time of positive charging to achieve.

Originally Posted by Paul L

Sure, the defaults on most charge regulators are way off, but decent solar controllers are programable.

Lead acid batteries take a long time to reach a true 100% charge. Selecting aggressive charging parameters (high voltages and a long absorption time) helps charge the batteries slightly quicker, but it is simply not possible to reach a true 100% charge in a short period of time no matter how aggressive the settings.

Charging the batteries to 90-95% on most cycles is actually very good. If you manage to do this, and more importantly limit the discharge, your batteries will live a long healthy life. Although an occasional true 100% charge is beneficial if it can be achieved.

In the days before solar, when batteries were charged solely by the main engine or by a generator when at anchor, the charging was typically terminated around 80-85% SOC. So adequate solar can produce a distinct improvement by virtue of the longer charging time. However, the solar day is normally too short to achieve a true 100% charge, unless you are not using the boat.

Other sources of charging such as wind, water or shore power can raise the batteries to 100%. This is providing a positive charge current can be maintained for a long period which is not common except for shore power.

[Paul L]

Originally Posted by noelex 77

I agree. When entering float, if the charge parameters are set correctly, the batteries are close to 100% charged. It is often called the "Cruisers 100%" for good reason. However, if you want to be accurate it is about 90-95% charged, (some would put the numbers a bit lower). It is not 100%. The extra 5-10% takes a long time of positive charging to achieve.



Lead acid batteries take a long time to reach a true 100% charge. Selecting aggressive charging parameters (high voltages and a long absorption time) helps charge the batteries slightly quicker, but it is simply not possible to reach a true 100% charge in a short period of time no matter how aggressive the settings.

I set my solar reg to the specs I got from Rolls for my AGMs. I wouldn't characterize those as aggressive or conservative. Just what the manufacturer suggests. I don't consider all daylight hours as 'a short period of time'.

I really wasn't aware that a batt that transitions at the correct acceptance amps/volts to Float is only at 90% charge. If this is true, then I am not getting to 100%.

[a64pilot]

For a used lifeline battery, your looking at about 6 hours to get to 100%, from a SOC of 50% but you can get to above 90% in two hours if you have a big charge source
http://www.pbase.com/mainecruising/e...battery&page=1

Point of the article was I believe to illustrate that increasing charger size doesn't cut charge time as much as you may think..

The 15 amp I state is worst case TV on, maybe making ice, listening to stereo, not trying to conserve.

So I'm saying run a generator a couple of hours early in the morning, let Solar finish you to 100% SOC. This gets you to a full charge once a week