Battery Charging Puzzle

[noelex 77]

Originally Posted by Dockhead

So if you're trying to efficiently use say 6 hours of generator use, you will get a lot more charge into the batteries by doing it in three runs of two hours each, then if you just leave the genset running for 6 hours. It really seems to me.

It should not be a lot more, but it will be more. The intial acceptance for a given SOC is higher, so short runs achieve a bit more. As batteries age the effect becomes more pronounced.

Against this the wear and tear on the generator is greater with multiple short runs.

As you would expect running the generator when loads are the highest and the SOC is at its lowest is best.

[Dockhead]

Originally Posted by noelex 77

It should not be a lot more, but it will be more. The intial acceptance for a given SOC is higher, so short runs achieve a bit more. As batteries age the effect becomes more pronounced.

Against this the wear and tear on the generator is greater with multiple short runs.

As you would expect running the generator when loads are the highest and the SOC is at its lowest is best.

Naturally, and so I typically shut down the generator soon after the charger reaches absorption stage. That way I use 50% or 60% to 80% or 90% as my working range for working the batts.

And then get them up further up than that once and a while when I have more lengthy AC tasks on board (washing and drying clothes, etc.). Then try to go into a port once every week or ten days to let the batts soak up a good, full charge, plus equalization.

That's working pretty well so far. I am eager to get some wind or solar working so I have a way of getting them all the way up when I'm not on board. This will surely be much better for the batts' health.

[noelex 77]

Originally Posted by Dockhead

That's working pretty well so far. I am eager to get some wind or solar working so I have a way of getting them all the way up when I'm not on board. This will surely be much better for the batts' health.

One thing to consider is I would be very surprised if your next set of batteries are not lithium. The technology is not quite there yet, but its getting very close and the very high acceptance rate of this chemistry is a major advantantage for boats that get most of their electrical power from a generator.

With a generator equipped, relatively high power consumption boat like yours solar and/or wind has got a lot advantages with lead acid batteries. It enables you to get the battery SOC 100%, compensates for the self discharge when you are away and helps reduce your generator run time.

However, most of the above advantages disapear with lithium. They don't like being charged to 100%, there is little self discharge and the very high acceptance rate means that your generator run times will be much shorter anyway. Unless your solar array is very large where it starts to contribute a reasonable proportion of your daily needs, it won't have a lot of impact.

Solar/wind infrastructure would be very worthwhile with your current lead acid batteries, but I have my doubts if you would still consider the investment (both in terms of money, time, effort and windage aesthetics etc) worthwhile after the installation of lithium batteries.

[hellosailor]

dockhead-
Rashly assuming you have those obsolete flooded acid lead batteries...The electrolyte gasses (I just call it "boils") as you charge them. Hit them with pure DC (instead of pulsed) and as the electrolyte gets heated and the charge flows, microbubbles form against the plates, displacing liquid electrolyte, raising the internal resistance, lowering the charge rate. So they charge less effectively. Also, the electrolyte stratifies, and it needs time for the electrolyte to flow around and equalize all through the battery.
Net result? Sure, short charges and rests could allow the bubbles to go away and the electrolyte to even out, so it might be more effective. How much more so, I don't know, I'm just suggesting there are physical reasons that might be valid.
Of course it also means multiple genset runs to be done and that's "more work" in my book.

Noelex-
As long as the lithium makers keep calling each other names (everyone else makes dangerously explosive inferior products) and arguing about BMSes...what's the line from Lawrence of Arabia? That as long as the tribes keep squabbling like children they will never be etcetera?

Maybe they'll grow up, integrate the BMS at the cell level during manufacturing, and establish a Bluetooth standard (or NFC or whatever) so all the integrated BMS systems can play nicely and not make Mamma come upstairs to whack 'em. (So to speak.)

'scuse me, gotta run to the patent office with that one now.

[goboatingnow]

Hit them with pure DC (instead of pulsed)

who is using pulsed ? , not a good way to charge LA at all really,

As long as the lithium makers keep calling each other names (everyone else makes dangerously explosive inferior products) and arguing about BMSes...what's the line from Lawrence of Arabia? That as long as the tribes keep squabbling like children they will never be etcetera?

dont Lagoon ( Frank ) would agree with you here ( nor the thousands of cordless drills either).
Dave

[hellosailor]

"who is using pulsed ? , not a good way to charge LA at all really"
All MPPT controllers output pulsed DC. And one of the US's top battery makers told me, some years ago, that they had found pulsed DC so much more effective than pure DC, that they were recommending it across the board for all charging sources.
Sorry, Dave, not my opinion. Scuttlebutt from a very senior engineer at a very well respected firm, who was speaking very bluntly and off the record on several topics regarding charging mysteries.

[Dockhead]

Originally Posted by noelex 77

One thing to consider is I would be very surprised if your next set of batteries are not lithium. The technology is not quite there yet, but its getting very close and the very high acceptance rate of this chemistry is a major advantantage for boats that get most of their electrical power from a generator.

With a generator equipped, relatively high power consumption boat like yours solar and/or wind has got a lot advantages with lead acid batteries. It enables you to get the battery SOC 100%, compensates for the self discharge when you are away and helps reduce your generator run time.

However, most of the above advantages disapear with lithium. They don't like being charged to 100%, there is little self discharge and the very high acceptance rate means that your generator run times will be much shorter anyway. Unless your solar array is very large where it starts to contribute a reasonable proportion of your daily needs, it won't have a lot of impact.

Solar/wind infrastructure would be very worthwhile with your current lead acid batteries, but I have my doubts if you would still consider the investment (both in terms of money, time, effort and windage aesthetics etc) worthwhile after the installation of lithium batteries.

Indeed. My plan when I bought these Trojans was that they would be my last lead-acid batts. Still hopeful.

[goboatingnow]

Originally Posted by hellosailor

"who is using pulsed ? , not a good way to charge LA at all really"
All MPPT controllers output pulsed DC. And one of the US's top battery makers told me, some years ago, that they had found pulsed DC so much more effective than pure DC, that they were recommending it across the board for all charging sources.
Sorry, Dave, not my opinion. Scuttlebutt from a very senior engineer at a very well respected firm, who was speaking very bluntly and off the record on several topics regarding charging mysteries.

mppt is a switched mode power supply, I have one in front of me , on my scope its a standard DC signal with a littel switching ripple.

other then cheap PWM solar controllers ( and there arnt really pulsed) Im not aware of any specifically DC pulsed chargers ( there was a funny UK one a few years back)

dave

[socaldmax]

While I don't (yet) own a boat, I do own two "toyhauler" trailers, which are always used to dry camp deep in the desert. The systems I have on those are basically the same as on a boat, with the exception of water makers.

Both trailers are equipped with 6v golf cart batteries, Xantrex inverter/chargers, 400-500 w of solar panels and 5-6Kw of onboard generators (for microwave and occasional air conditioning.)

We use a lot of power, with HD sat dish, 3 LCD TVs, 3 DVRs, laptops, wifi, outdoor spotlights, etc. The solar panels do an excellent job of providing all power we use aside from micro/ac use. I'd also suggest solar panels.

Solar panels and lower capacity MPPT controllers are getting cheaper, especially on craigslist. I've seen a lot of used (3-5 yrs old) panels in the 200 - 260w range for sale for 75 cents/watt.

I've also bought/installed 3 of the Eco-worthy 20 amp MPPT controllers and they are very nice units, especially for only $102 delivered. The have gold plated contacts, a nice large toroidal inductor and the pc board is mostly surface mount devices and covered in a nice conformal coating. Under optimal socal conditions, it will peak at 20 A with only 300w of panels on a 12v system, 600w on a 24v system. I have 410w of 24v panels on that system and it peaks at 22 A. The nice thing about this unit is it has a 2 line 40 character display and 4 buttons to give voltage and current info as well as full control of float and bulk charge voltages all the way up to 15.4v.

If you'd rather go with a more well known brand, I've also had great performance with my 25 A Blue Sky Solar Boost 2000e controller with 475w of 12v solar panels. Most days it's putting 20 -25 A into the 660AH battery bank, keeping them fully charged after about 11am or noon. They can be found for about $225 online.

Speaking of charge, as a Navy instructor, we usually just described batteries like a bucket. Fill them with current, and use the current when you need it. However, after reading a website called "The 12v side of life", written by a full time RVer who lives in the northern US, I've changed my views on lead acid batteries and what SOC really is.

According to the author, who lives entirely on solar power and doesn't even own a generator, batteries are more like a compressed air tank. Meaning that if your regulators and charge controllers are set to stop bulk charging at 14.6v or less, then your batteries have never been fully charged and are more like at about 80% charged. Assuming one never drops below 50% SOC, most people are only getting/using 30% of their battery bank's rated power an leaving the other 20% unused.

He cites the Interstate and Trojan websites as his sources. Somewhere on those websites he found info that indicated that the batteries should be charged at 15.4v for 3 hours after they hit that peak voltage in order for them to be fully charged. Very interesting reading. Based on his info, I increased my solar controller bulk charge voltage to 15.4v during the winter when I use them and adjust them down to 14.6v during the summer, when they are much warmer and sit unused for long periods. Even though my controllers shut off at 15.4v instead of maintaining that level for 3 more hrs, I did see a big increase in usable power from my batteries compared to before, when my controllers were factory set at 14v.

I also installed Water Miser caps on all of my batteries, and they have drastically reduced water loss from charging, discharging, high temps, etc. I can check water levels much less often and replace much less water each time. In the past, I've wondered if I was doing anything right or wrong in regards to care and charging of my battery banks, but I get 6 yrs out of each set and I buy the cheap Kirkland ones from Costco (made by Johnson Controls, who also make them for other "labels"). Considering the heavy loads and sporadic use, I'm pretty happy.

I hope the solar power and charging advice helps out!

[sailinglegend]

Originally Posted by socaldmax

,,,,after reading a website called "The 12v side of life", written by a full time RVer who lives in the northern US, I've changed my views on lead acid batteries and what SOC really is.....

This is 13 years old - and some of it is so out of date!!!!!

[socaldmax]

Originally Posted by sailinglegend

This is 13 years old - and some of it is so out of date!!!!!

At the time that he wrote some of that, copper wiring was much cheaper and solar panels were much more expensive. However, nothing has changed in terms of FLA batteries, charging voltage vs SOC, MPPT vs PWM, solar panel sizing, current vs wire gauge, solar panel tracking, shading effects, etc.

A lot of the basic info is still relevant. He managed to maximize his solar harvest of power per day with a surprisingly small amount of solar panels and the right sized battery bank and properly adjusted solar controller. Much better results than people are getting throwing up 800w worth of panels on their bimini or roof where it's shaded all day by the sail or boom, connected with 14 ga wire and wondering why they're only getting 15 A of power at noon, while their batteries are being charged at 14.4v and never exceed 75% SOC.

I see a lot of discussion about Sunpower panels on this forum due to their superior efficiency, but most of the pics I see of solar panels actually mounted on boats they are either partially or fully shaded for much of the day. Even partially shaded panels provide far less power, enough so that a Honda eu2000 becomes a far better alternative, especially considering the weight penalty of panels at 50-70 lbs ea. and they never produce power at night.

[Exile]

I have a system similar to Dockhead's, albeit all 12v Lifeline AGM's. Namely 675ah of batt. capacity, no solar/wind, a 50-amp charger (small, I know), and a 8kw genset. If, like Dockhead's, the goal was purely to keep topped off when away from the boat with no shore power or genset usage, and the only significant consumption was occasional bilge pump usage, would a 30-watt solar panel producing say, an avg. of 2 amps for 5-6 hrs./day, be sufficient to keep up with the minimal usage and the self-discharge rate?

[noelex 77]

Self discharge rates do vary a lot with temperature, battery type and age.
30w should be enough to cope with this and allow a little for bilge pump loads.
It is worth checking the parasitic loads they are often a bit higher than people imagine.

With a large battery bank like yours and the cheap cost of solar I would fit something a bit larger.

[socaldmax]

According to the lifeline website, at 68*F., they discharge at 3% per month. At 86*F., they discharge at 5% per month. In your case, 20A to 34A depending on temp.

If you really make 10-12 A per day from that panel, that could be 300-360A per month, if you get perfect sunshine every day, which never happens. Even here in socal, we get less that optimal sun, especially along the coast. Next add in how much the bilge pumps are going to use, which could vary widely based on number and severity of leaks... and I would guesstimate that this system would barely be able to handle things under perfect conditions, ie., no shading, sunny days, not too much bilge action or parasitic losses.

Another way to approach the issue is looking at the costs of installing a solar panel system. You need solar panels, a good controller, cabling, and mounts. Due to economies of scale, a 100w panel is going to be cheaper per watt, and a 200w panel is going to be an even slightly better value. When it comes to solar controllers, I will not install anything less than an MPPT controller, especially since I've started using the Eco-worthy at only $102. I don't know what a 30 watt panel goes for in your area, but I'm seeing $72 to $150 per panel online, plus shipping. A 100w panel sells for $89 to $179 and a 200w panel sells for $202 new. I've bought a lot of them used, in perfect condition, for $150.

It's kind of a "might as well..." situation. It takes virtually as much effort to mount a small panel as a medium panel, same effort to run the cabling, mount the solar controller, etc. The only difference is price, and I've just shown you can get a new 200w panel for $50 more than a 30 watt panel, and the price difference is only $25 if you get a used one locally, plus you save on shipping.

Let's say your target solar system size is 20A, you'd need 2x 160w panels for that. Even 170 or 175w would work. If you have the room, plan for 2 panels, by them both used for about $250-300, then get the solar controller for $102. The rest of the expense is mounting hardware and cabling, which varies widely based on length and wire ga.

With a system like this you'd have your batteries topped off, all bilges dry, and you could leave your freezer and/or fridge running if you wanted, regardless of when you return.

[Exile]

All good info. For the time being & in light of other priorities, however, I am inclined to confine my efforts & money towards having a way to keep my batts. topped off & healthy when not plugged into shore power. The refrig. & freezer run off of 110v & engine drive, so unless I change over to 12v or install an inverter, I'm only concerned with self-discharge & parasitic loads.

If say, worse case, this amounts to as much as 40-50A/month, it seems that a solar panel that produces at least 2A for 5 hrs. each day -- i.e. 300A/month -- would be more than adequate to cover it, even taking into account cloudy days. Is this too optimistic?

Like Dockhead, I don't have many good places to permanently mount panels, and so am intrigued by the portable ones that could be draped over the boom at anchor or mooring, for e.g., and then easily stowed when not in use. Aurinco & Solbian come to mind, but they are very expensive. I just found a company that sells on Amazon called PowerFilm that is more reasonable. They are the amorphous silicon type so not as efficient as mono's, but they make highly flexible, rollable panels from 28-60 watts that are about 16" wide and approx. 6-7' long. They also advertise being made with marine grade materials & connectors, and include grommets for tying down. They operate at 15v so I would assume a controller would also be desirable or necessary.

Here's a link: http://http://www.amazon.com/PowerFilm-R-28-Rollable-Solar-Charger/dp/B001UHAAAC/ref=sr_1_3?m=A1VOUFSIGRIGBC&s=merchant-items&ie=UTF8&qid=1378051440&sr=1-3

For those with similar needs, let me know what you may think if you're interested. Tks.