solar charge controller?

[walt]

The tech said that if you had one panel that puts out 16 volts and another 17 and another 19 volts then the voltages will average and you will be wasting the potential output of the panels above the average. If I understood him right.

When you hook the panels all together, they will all be the same voltage. The MPPT controller is continually searching for the maximum power point of the panels as this constantly changes - for example by a cloud passing. Since the different panels all generally have different max power points, the controller can only look at the average of what comes in - and this may not be optimum for any of the panels (but stilll generally a benifit)

The PWM (or obsolete shunt) simply connects the panels directly to the battery - the panel voltage drops to the battery voltage. Since the panels are "constant current", i.e., the current output from them is independent of voltage, the current from each panel is simply added together. Doesn’t matter what the open circuit or max power voltage of the panel is, they will all be at the battery voltage. No tradeoff at alll to connect differnt panels in parellel.

FYI, I like MPPT controllers, just don’t think they are always the best for what most people with our trailerable boats need. My opinion is that a 20 to 40 watt panel is all these boats need unless you have special needs (such as a 12 volt fridge).

Here is an example..
Say a baseline is a 20 watt panel (use solartech as an example) and a Morningstar Sunsaver 6 (PWM) – cost is $142 for panel and $38 for the charge controller.

Then look at two upgrades on this.

1. Go to the Genasun GV-4 MPPT controller. Added cost is about $100-$38 = $62. What did you get for $62 – about 15% more current in general.

2. Keep the same charge controller, go to a solartech 30 watt panel. Added cost is $154-$142 = $12. What did you get for $12 – about 50% more current in general.

Of course the 30 watt panel is larger than the 20 and that can be very important..

 

[Sumner]

my panels were given to me, I didn't choose them, so I figured I'd put em to use!
They are BP 350U. Looking around online I think they are probably obsolete now.
rated-50 watts
Isc- 3.2 short circuit current
Vmp- 17.3 voltage at rated power
Voc- 21.8 volts open circuit
Vnom- 12 volts nominal voltage
Multicrystalline
The places where I did see pricing showed they were pretty pricey.
The newer ones seen to have more power and are cheaper!

Free in most cases is good and those are probably very good panels.

You didn't say what the Imp, Maximum Power Current, was but from the Vmp and the 50 watts I'd guess it is 2.9 amps. If you had 2 panels together that would be about 6 amps potential. Divide that by .7 and you get 8.6 amps. So a MPPT controller that would be able to output 10 amps would work fine. The short circuit amps for two panes, 2 X 3.2, would be 6.4 amps, so any MPPT controller that can handle that or more input amps will be fine.

Blue Sky and Morningstar are the names that keep coming up. We started with a small Morningstar PWM on our 40 watt panel, but went to a Blue Sky MPPT controller when we added the additional panels. We have been very happy with it. We bought the 2512iX since at the time I was considering having a separate battery in the laz to start the outboard and it has two charging circuits on it. Latter I decided it was as cheap or cheaper to run #4 wire from the cabin to the outboard and use the 2 batteries that we had up there, so we never used the two charging circuites. Like Walts you also had the option, if you didn't use the second charging circuit, to have a timed output to something like an anchor light. We solved the need for that with an....

http://purplesagetradingpost.com/sumner/macgregor/outside-23.html

...anchor light that only consumes 2 watts. The 2512iX sells for $212.00 from Solar Blvd, but the 2512....

http://www.solarblvd.com/Charge-Con...V-3-Stage-Charge-Controller/product_info.html

...with out the 2 charging circuits sells for $178. If I had it to do over again I'd buy the cheaper one as I didn't need the extra features. It will handle up to 20 amps of short circuit current, but limits output to 25 amps, so you are wasting amps if your total array puts out over 17-18 amps, but that is a lot. That would be almost 300 watts of panels so this controller would probably do anything you could ever want on our size boat.

We have 480 watts of panels going on the Endeavour and will be using Blue Sky's 3024iL that is just big enough for that array. The 2512 would make a nice controller for you. As I said before the panels and a good controller will really pay off for you if you start doing trips greater than 3 days and don't use the outboard much.

Talking about the outboard, now that you have the batteries in the cabin have you been starting it off of them with the #10 wire ok, I think you had an electric start?

Sum

Our Endeavour 37

Our Trips to Utah, Idaho, Canada, Florida

Our MacGregor S Pages

Mac-Venture Links

 

[walt]

That is a big benefit when the battery is low like in our situation cruising on a day to day basis where the battery ends up low in the morning and and needs to be re-charged each day.

Hate to argue.. but I thiink this is a minor benifit.... the MPPT in general will only get you 10 to 15% more current than a PWM. The battery voltage for this application probably only varies by up to .7 volts for your application, much less for mine. Were your batteries still any good after the trip..

 

[Sumner]

...FYI, I like MPPT controllers, just don’t think they are always the best for what most people with our trailerable boats need. My opinion is that a 20 to 40 watt panel is all these boats need unless you have special needs (such as a 12 volt fridge)...

I agree that is true in most cases as most people aren't taking extended trips with a trailerable boat, but if they do want to stay out over 3 days or so then they need to weigh the options. For instance your extended trips have been to Lake Powell where you did a lot of motoring each day and got the charging from the outboard. Now lets say you head up north like we did to Idahao and/or Canada and get on the lakes us there where you just don't need the outboard. I don't thing we burned 2 gallons of gas in a month. Stay out a week there and I'll bet you would of started running out of amps .

You also make a valid point that you can probably add amps cheaper with more panels vs. going from a PWM controller to a MPPT controller. I don't mind adding panels to our boat, but some people can't do it easily due to limited fabrication abilities or they don't like the looks of the panels on the boat, which I often hear. In that case or in a case like us where we do want a frig and some other items maximizing the panels we have is important.

I do agree with you that probably 80-90% of the people on this board can get along fine with 40-60 watts of solar and a PWM controller 90% of the time. For the other 10% of the time they are out when they run the battery down running the outboard is probably a good alternative.

With that in mind I hope people realize that I'm making suggestions often that only make sense for a small number of people . Oh it is nice to be retired and have time for those longer trips :dance:. Of course the downside is that I'm old and getting older every day and better make good use of every day :cry:,

Sum

Our Endeavour 37

Our Trips to Utah, Idaho, Canada, Florida

Our MacGregor S Pages

Mac-Venture Links

 

[Sumner]

Hate to argue.. but I thiink this is a minor benifit.... the MPPT in general will only get you 10 to 15% more current than a PWM. The battery voltage for this application probably only varies by up to .7 volts for your application, much less for mine. Were your batteries still any good after the trip..

Let's take the 100 watt panel I have on the boat in the array and I realize these figures or optimal figures, but still will show the difference that the MPPT can make over the PWM.

The panel is 'rated' at 5.8 amps at 17.2 volts (5.8 X 17.2 = 99.76 watts).

With the battery at 12.0 volts the PWM controller is passing 5.8 amps to the battery. The MPPT will pass 8.3 amps to the battery.

With the battery at 12.7 volts the PWM will still pass 5.8 amps potentially as the battery will now except less. The MPPT could still pass 7.8 amps if the battery will accept it.

There again they say up to 30% more current to the battery vs. a PWM and you are right it might average more like 10% to 20%, but in 'our' case I'll take that. I don't like running the gen-set anymore than needed.

Walt do you agree with what they are saying here on how MPPT works?

http://windsun.com/ChargeControls/MPPT.htm

Here is a quote from that source....

MPPT's are most effective under these conditions:
Winter, and/or cloudy or hazy days - when the extra power is needed the most.

• Cold weather - solar panels work better at cold temperatures, but without a MPPT you are losing most of that. Cold weather is most likely in winter - the time when sun hours are low and you need the power to recharge batteries the most.
• Low battery charge - the lower the state of charge in your battery, the more current a MPPT puts into them - another time when the extra power is needed the most. You can have both of these conditions at the same time.
• Long wire runs - If you are charging a 12 volt battery, and your panels are 100 feet away, the voltage drop and power loss can be considerable unless you use very large wire. That can be very expensive. But if you have four 12 volt panels wired in series for 48 volts, the power loss is much less, and the controller will convert that high voltage to 12 volts at the battery. That also means that if you have a high voltage panel setup feeding the controller, you can use much smaller wire.

For us going to Florida in the winter the MPPT will pay off on the new boat. Also if we pull the batteries down like we do now on a daily cycle. For someone that only goes out in the summer months the MPPT won't have as big of an effect. Also with the 480 watts we now have on the Endeavour we might not be pulling the batteries down as much, but we will have a larger frig/freeze combo and a few other things. If we don't discharge the batteries as much then the PWM controller would be about as good. The MPPT is going to be $350 vs. around $150 for a PWM controller. So lets say we have the boat for 5 years. What is that $40 more a year for the one vs. the other about the cost for 10 gallons of gas. In our case we will spend the extra as I don't see a down side other than the cost.

As I mentioned in my other post above I'm presenting ideas that might not be viable for very many people on the board, but I know from e-mails received that there are some out there that hope to head down a similar road/waterway that Ruth and I have taken .

Sum

Our Endeavour 37

Our Trips to Utah, Idaho, Canada, Florida

Our MacGregor S Pages

Mac-Venture Links

 

[doehunter]

Free in most cases is good and those are probably very good panels.

You didn't say what the Imp, Maximum Power Current, was but from the Vmp and the 50 watts I'd guess it is 2.9 amps. If you had 2 panels together that would be about 6 amps potential. Divide that by .7 and you get 8.6 amps. So a MPPT controller that would be able to output 10 amps would work fine. The short circuit amps for two panes, 2 X 3.2, would be 6.4 amps, so any MPPT controller that can handle that or more input amps will be fine.

Blue Sky and Morningstar are the names that keep coming up. We started with a small Morningstar PWM on our 40 watt panel, but went to a Blue Sky MPPT controller when we added the additional panels. We have been very happy with it. We bought the 2512iX since at the time I was considering having a separate battery in the laz to start the outboard and it has two charging circuits on it. Latter I decided it was as cheap or cheaper to run #4 wire from the cabin to the outboard and use the 2 batteries that we had up there, so we never used the two charging circuites. Like Walts you also had the option, if you didn't use the second charging circuit, to have a timed output to something like an anchor light. We solved the need for that with an....

http://purplesagetradingpost.com/sumner/macgregor/outside-23.html

...anchor light that only consumes 2 watts. The 2512iX sells for $212.00 from Solar Blvd, but the 2512....

http://www.solarblvd.com/Charge-Con...V-3-Stage-Charge-Controller/product_info.html

...with out the 2 charging circuits sells for $178. If I had it to do over again I'd buy the cheaper one as I didn't need the extra features. It will handle up to 20 amps of short circuit current, but limits output to 25 amps, so you are wasting amps if your total array puts out over 17-18 amps, but that is a lot. That would be almost 300 watts of panels so this controller would probably do anything you could ever want on our size boat.

We have 480 watts of panels going on the Endeavour and will be using Blue Sky's 3024iL that is just big enough for that array. The 2512 would make a nice controller for you. As I said before the panels and a good controller will really pay off for you if you start doing trips greater than 3 days and don't use the outboard much.

Talking about the outboard, now that you have the batteries in the cabin have you been starting it off of them with the #10 wire ok, I think you had an electric start?

Sum

Our Endeavour 37

Our Trips to Utah, Idaho, Canada, Florida

Our MacGregor S Pages

Mac-Venture Links

No, on the electric start! It's all manual. It does have a generator but it's not wired up. I usually don't run the motor very long and when I do I don't run it real fast, so I don't think I'm missing too much.

 

[Sumner]

No, on the electric start! It's all manual. It does have a generator but it's not wired up. I usually don't run the motor very long and when I do I don't run it real fast, so I don't think I'm missing too much.

Since the outboard's output is probably 6 amps max you don't need the #4 that we are running back to the laz. Sounds like you are ready to enjoy some more time on the water ,

Sum

Our Endeavour 37

Our Trips to Utah, Idaho, Canada, Florida

Our MacGregor S Pages

Mac-Venture Links

 

[Sumner]

... Were your batteries still any good after the trip..

Hey in the heat of the arugment I forgot the above. The batteries seem to still be fine, but I don't think they are quite what they use to be. They are the same brand and type, but about 2 months apart in usage. I usually see .1-.2 difference in them on the volt meter, but keep them tied to gether for use and charging (thanks to you ). When I replace them it will be with two 6 volt golf cart batteries again thanks to your advice . I'd recommend the same to anyone else trying to make a decission on batteries for their boat. The Endeavour has 2 6 volt banks and a separate 12 volt starting battery.

We only saw voltages on the batteries slightly below 12.0 a couple times. I try and keep them at over 50% charged. Those were the times and a couple times when they were around 12.0 that I ran the gen-set in the morning to make best use of it.

Is is capable of 60+ amps output, but the most I ever saw was 22-23 amps and then only for a couple minutes. It would quickly drop to 18 amps or so and when it got down to 12 amps or so, usually within 30 min. or less, I turned it off and let the panels take over.

Almost every day by afternoon the batteries were in the 'float' mode on the charge controller. We turn the frig off at night and would take it down to 38-39 deg. before turning it off. In the morning when we started to see 90 deg. daytime temps the frig would be back up to 44-45 deg F.. It would then run most of the day, usually 8-10 hours to get back down to the 38-39 deg.

Seems like a long time, but still only on about 33-40% of the time in a 24 hour period. Running it consumes about 3.5 amps. We love it, no more soggy food or planing the trip around where to get ice every 4-6 days. I was surprised that as populated as the area we were in during the FL trip finding a place to go ashore is not easy or convenient most of the time if you are moving.

Then when we were in the 10,000 Island/Everglades area there is nothing except going into Everglades City and that isn't convenient most of the time. The frig is one of those things that once you have one going back to ice is one of those things you just don't want to do. We had to do it for the 5 day trip with the Endeavour and didn't like it,

Sum

Our Endeavour 37

Our Trips to Utah, Idaho, Canada, Florida

Our MacGregor S Pages

Mac-Venture Links

 

[walt]

With the battery at 12.0 volts the PWM controller is passing 5.8 amps to the battery. The MPPT will pass 8.3 amps to the battery.

I see where you got the number of 8.3 amps (99.76/12) but on my MPPT controller I never see anywhere near that amount of boost. The one I have (an older Blue Sky) has a display showing current from the panel (which is exactly what the PPM would deliver to the battery) and current out of the MPPT controller. I’m pretty sure my system has never exceeded 20% boost to panel current (probably more like 15%) and this panel always stays cool. Panel voltage drops when the panel gets hot and boost current also drops. I have not paid attention to the battery voltage when noting the boost I got however. Your number also doesn’t consider the controller operating current and conversion efficiency.

FYI, what you listed here is a 43% boost in current (8.3/5.8 = 1.43). This never happens. My data point shows much lower than this - anyone else have some real numbers?

Lake Powell trips..

The first year we went (family of four), my outboard charger did not even work and I had a 20 watt panel placed in a poor location because of partial shading. We had LED lights, watched a movie every day, ran the stereo a bit, charged AA batteries. I had about 200 amp hour of battery so approx. 100 available, at the end of the trip, I was probably about out of excess capability but there is no problem with that - plugged in the AC charger when I got home.

Each year after that, I kept going to larger and better placed panels and somewhere in that time fixed the alternator on the old Honda but it didn’t amount to much. The fourth year, I had the new Nissan with the charger but that year I had to keep the outboard disconnected most of the (which meant I couldn’t use the electric start) because it would have overcharged the batteries since the lower power outboards have little regulation. For the most part, I just got by on the 40 watt panel. Kids were watching several movies per day using the stereo, LED lights, charging the AA batteries, etc..

 

[Sumner]

I see where you got the number of 8.3 amps (99.76/12) but on my MPPT controller I never see anywhere near that amount of boost. The one I have (an older Blue Sky) has a display showing current from the panel (which is exactly what the PPM would deliver to the battery) and current out of the MPPT controller. I’m pretty sure my system has never exceeded 20% boost to panel current (probably more like 15%) and this panel always stays cool. Panel voltage drops when the panel gets hot and boost current also drops. I have not paid attention to the battery voltage when noting the boost I got however. Your number also doesn’t consider the controller operating current and conversion efficiency.

FYI, what you listed here is a 43% boost in current (8.3/5.8 = 1.43). This never happens. My data point shows much lower than this - anyone else have some real numbers?....

I agree that you aren't going to get 43% and they don't advertise that. They commonly say up to a 30% increase. My numbers didn't take into account any losses due to controller efficiency, usually about 3%-6%, or other losses and assumed peak power from the panel. They were optimal numbers and not 'real life' but were mainly presented to show that the MPPT controller can give you an amperage increase vs. no increase for the PWM controller and that is what I'm looking for.

Here is a quote from Blue Sky about their MPPT controllers...

The actual charge current increase you will see varies primarily with module temperature and battery voltage. In comfortable temperatures, current increase typically varies between 10 to 25%, with 30% or more easily achieved with a discharged battery and cooler temperatures. What you can be sure of is that Solar Boost charge controllers will deliver the highest charge current possible for a given set of operating conditions.

and it backs up your 10-25% and I agree with that. In 'our' case I'll take the 10%-25% increase, but as I've said over and over again this is probably a minor issue for most the people on here that are reading this as their needs are so different than ours,

Sum

Our Endeavour 37

Our Trips to Utah, Idaho, Canada, Florida

Our MacGregor S Pages

Mac-Venture Links

 

[FourPoints]

Genasun has a write up on how the MPPT generates the boost, http://www.genasun.com/aboutmppt.shtml, but I like this analogy better http://www.altestore.com/howto/Sola...ponents/How-MPPT-Charge-Controllers-Work/a13/

Using the previous numbers of a 50w panel at 17.2v you get 2.9A, but when you connect that same panel to the battery with a PWM/Shunt controller you lower the panel voltage to ~12v, but still get roughly the same 2.9A, but worked backwards that only equates to 35w coming from the panel, a big loss... hooked up to a MPPT controller, you effectively operate 12v at 50W, or 4.1A, or 30% boost. Typical conversion loss is around 5% for the MPPT controller, plus voltage drop of the wires (~3%), so you will get in the batteries around 3.8A, which at 5-6 hours a day of average good solar time, that's another 5AH of juice into the batteries every day, which is equivalent to having a panel about 17w larger than you actually have (it's a 12w boost, but you have factor in the same efficiency loss from the panel which means you need a 17w increase in panel size to get 12w at the battery).

In short, 50w panel with MPPT is roughly equal to a 67w panel with a PWM controller...

 

[FourPoints]

I had the new Nissan with the charger but that year I had to keep the outboard disconnected most of the (which meant I couldn’t use the electric start) because it would have overcharged the batteries since the lower power outboards have little regulation.

I had the same issue, but wasn't willing to disconnect the outboard as I didn't want to be without the power generation in case I really needed it, so I fixed the regulation problem instead.

http://sailingit.com/blog/boat-projects/outboard-voltage-regulator

 

[walt]

67/50 = 1.34 = 34%..

I believe that type of regulator simply dissipates the charge in a resistive load when the battery is full. Looks like a nice solution - even fit well. I wonder how hot it gets if you ran the outboard for a while with the battery full? 80 watts in a small area can get very hot - way past what typical electronics are specified for.

 

[FourPoints]

I actually haven't checked to see how hot it gets, but the charge circuit almost never outputs the full 80w because it's dependent on engine RPM, and most of the time I don't run the engine past 75% throttle. I believe it dissipates the excess power to ground, but I'm not exactly sure on that, I just know that even when running the engine for many hours coming back from NYC with no wind at all, the voltage stayed under 15.0v...

between the engine and the solar charging system, I meet my power consumption needs quite effectively now. If I was going on extended trips (more than 3 days long) I might look into more power, but as I use the boat, it suits my usage quite well

 

[walt]

Yup, I normally dont run my outboard for more than maybe 1/2 hour. Might be worth checking on a long run but if the regulator didnt burn out already, probably wont in the future.

Sumner knows some of the trips I took at Lake Powell where the outboard was run for a LONG time. One trip, we did 180 miles in six days most of it motoring (and yes, I enjoyed the heck out of the trip). I think my kids may have outgrown those trips.. but I will for sure go back!!!!

Off topic a little... but it seems to me that there is some sort of regulation in the Nissan/Tohatsu 9.8 hp 4 stroke.. Sumner, what do you think, you must have also been watching this...

 

[Cruiser1]

I had the same issue, but wasn't willing to disconnect the outboard as I didn't want to be without the power generation in case I really needed it, so I fixed the regulation problem instead.

http://sailingit.com/blog/boat-projects/outboard-voltage-regulator

Sorry to be very much a 'learner' in the electronics department but I have been pondering these issues for some time. Purchasing a digital multimeter and 'dedicated' electronics tool box (for my electonics tools and parts) a few months ago seemed like a very positive step in the right direction.

My motor is a 1992 Nissan 8HP with electric start and 80W alternator/rectifier. It is conected directly to a 60Ah sealed wet cell battery located under the galley, although I am in the process of looking at replacing that with a 100Ah AGM that a friend has given me from his RV (when he replaced it with dual batteries he wanted 2 of he same type and age). I could never quite understand how the only 2 leads that come out of the motor send current to the motor for starting and back from the motor with charging - but I have just accepted that it is the case and all works well.

The boat came with a 10W flexible solar panel which I thought would be good for trickle charging the battery, to protect against sulphation, when the boat is in mast up storage. However I have not been game to connect it for two reasons. Firstly I heard mixed opinions about about the need for a regulator on such a small panel and secondly I do not imagine it has a diode in the system to protect agianst reverse flow at night. Thirdly is currently designed to sits flush on top of the pop top with 4 clips and I don't like that idea on a permanent basis - i.e I would prefer to make a bracket to mount on a pole on the pushpit and be able to face the panel towards the sun during storage - given that the panel is probably as old as the motor and the boat and that it is not likely to be able to handle being outside permanently, I have been reluctant to even bother with it. On the other hand some sort of trickle charge solar panel seems obligatory in order to avoid battery sulphation over time.

Panel specs are as follows:
United Solar Systems Corp Troy, MI
Electrical Ratings at 1,000 W/m2 AM 1.5 Cell Temp 250C
Max Power 10.3W
Current Max Power 0.62A
Voltage Max Power 16.5V
Short Circuit Current 0.78A
Open Circuit Voltage 23.8V
Model Type USF-11
Max System Voltage 30V
Serial Fuse 1.5A

I have been concerned that, given we often motor for 1-3 hours in a day, the outboard charger could cause damage to the battery. Some people say you can damage the motor by running it without being connected to the battery, my mechanic says the opposite.

I have been reading up on marine electrics a fair bit (mainly Nigel Calder's "Boatowners Mechanical and Electrical Manual" plus web forums) but up to this point I have a assumed I can install a voltage MPPT regulator, close to the battery, that both the motor and solar panel would feed into and that would solve all my concerns, although I gather I would still need some sort of diode to prevent back flow to the panel overnight.

Does this make any sense at all or am I way off the mark?

 

[Maine Sail]

FYI, what you listed here is a 43% boost in current (8.3/5.8 = 1.43). This never happens. My data point shows much lower than this - anyone else have some real numbers?

Never seen anywhere close to that with any brand of MPPT. Normally 10-12% with the occasional 15-18%+/- but that is on a huge 24V panel feeding a 12 volt bank so ti has lots of excess voltage....

 

[FourPoints]

My motor is a 1992 Nissan 8HP with electric start and 80W alternator/rectifier. It is conected directly to a 60Ah sealed wet cell battery located under the galley, although I am in the process of looking at replacing that with a 100Ah AGM that a friend has given me from his RV (when he replaced it with dual batteries he wanted 2 of he same type and age). I could never quite understand how the only 2 leads that come out of the motor send current to the motor for starting and back from the motor with charging - but I have just accepted that it is the case and all works well.

your motor is identical to mine, they even share the same parts manual. if you follow the same steps I used you will be able to add the regulator to your motor without much trouble. if you need help locating I can give you more info on the process.

As for the solar panel, the genreal rule of thumb is a charge controller should be used when the solar panel to battery ratio exceeds 10 Watt to 100Ah.

If I were you, I would install the regulator on the engine, and permenantly install the panel with a controller of some sort. Thy type of controller you pick will be determined by the level of discharge you intend on recharging the batteries from using the panel, and the time you want them recharged in.

 

[Cruiser1]

Thanks FourPoints, when you say a 'regulator' on the motor and a 'contoller' on the panel I gather there is a difference between these tow pieces of equipment? I also gather it is not possible to feed the output from both the motor rectifier as well as output from the solar panel into the one regulator - is that correct?

Also, regardless of the answer to the above, does the existing rectifier on the motor need to be removed or can I just insert the new regulator on the positive wire (near to the battery) coming from the motor?

 

[FourPoints]

Thanks FourPoints, when you say a 'regulator' on the motor and a 'contoller' on the panel I gather there is a difference between these tow pieces of equipment?

a regulator only limits the peak voltage that is output from the charging system on the engine, it does not attempt to determine the state of charge of the batteries or perform any kind of intelligent charging.

I also gather it is not possible to feed the output from both the motor rectifier as well as output from the solar panel into the one regulator - is that correct?

there are charge controllers you can output the engine charging to, but the kind that won't damage the charging circuit start around $150, and still require something else present to divert the excess voltage into like a hot water heater or fridge. unlike a solar panel, you cannot disconnect and reconnect the charge circuit while the engine is running without damaging components, and nearly all solar charge controllers do exactly that when they no longer need any power from the panel.

Also, regardless of the answer to the above, does the existing rectifier on the motor need to be removed or can I just insert the new regulator on the positive wire (near to the battery) coming from the motor?

it will have to be disconnected at the least, but it is only one screw, and one wire that needs cut, the other 2 wires are snap connectors and the whole thing can be removed in about 60 seconds. If I needed to do the job again, it would only take me about 10 minutes to make the whole rectifier / regulator swap, it is a very easy process once you understand what you are doing.

You cannot install on the wires near the battery because you need to pull power from the battery to start the engine (unless you exclusivly pull start it). Read through this thread where I was working through the problem with George, the process is really pretty simple once you understand what is going on.
http://www.seafaring.com/forum/viewtopic.php?f=2&t=22569