Some Advice on Alternator , Battery and Solar Connectivity

[ian_brown]

Hi All,

I've been searching the web for some assistance with the above and stumbled upon this forum and have seen some good advice from you guys so decided to join up try it out for myself.

I've been tasked with overseeing the building of a 70ft dive boat built here in the Sinai, Egypt, its planned that the boat will have twin 400bhp(ish) Doosan engines using 24v 150Ah battery pack with their standard 24v - 50A alternator.

Im planning to install 2 x 150W 12v solar panels connected to a steca 30A solar controller charging 6 x Deka 100Ah AGM batteries to run the 12v devices and an inverter for a few 220 AC devices

All the above has been spec'ed and ordered but i'm struggling to decide/workout how to backup the solar with charging from the engines.

As we are pretty remote parts and experience are pretty limited, Im looking for an effective but "simple", "cost considered" and environmentally a solution as possible.

It seems the local practice is to install a generator and/or second 12v alternator on one of the engines to run the 12v devices. we are the first boat in the area to be installing any solar/battery system.

My question is, is this the best way considering my "simplistic" needs, can I install a manual switch inline to select concurrent charging from both the solar and alternator, or charging from each supply individually with causing harm!

I look forward your responses and recommendations, please let me know if i need to be more specific in my details.


Best Regards,

Ian

[noelex 77]

Hi Ian
Welcome to the forum.

Multiple charging sources don't create any problems. So solar and an engine alternator (or two) can both charge the battery at the same time without any significant problems.
Most sailboats set up the voltage (if the regulators are adjustable) so the engine alternator cuts out charging slightly before the solar panels. This is done so the engine gets maximimum power, but with 400hp to play with, the power draw of the alternator is not a great consideration.

[ian_brown]

Thanks noelex 77,

Assuming the 2nd alternator has build in regulator, would you suggest sticking with that or opt for an advanced regulator to optimise the charging, I believe I will be able to source a Bosch 100A, is this overkill.

Second point, if I install a switch will the alternator get damaged as it will be running (as in turning), with "nothing" connected...

I've also see lots of battery and alternator and device protection devices, are these necessary or just a nice luxury item to add extra protection to the system with appropriate fusing..

thanks again.

[noelex 77]

The advanced regulator will generally help particularly on a power boat when the engine run times are reasonably long. A 50A alternator is OK considering your small battery bank of 150 AHrs. As long as you do not have any high current draw devices. (No electric scuba tank compressors I assume.) A 100A would not gain you much extra the batteries won't accept the extra output.
Alternators can be damaged if the engine is run without a battery connection, particularly if disconnected while the engine is running. The safest option is to have a switching system where this is impossible.
Battery switches can be "make before break" so batteries can switched without any problems. There are switches that enable that enable the alternator to be disconnected by turning off the alternator output before disconecting the battery, saving the alternator diodes, but I don't see any advantage, in your sort of set up, of ever disconecting the alternator.

[DeepFrz]

A 100 amp alternator is a little small to charge 600 ah AGM battery bank. It depends on how much power you use. You really need a heavy duty alternator and an external regulator and battery and alternator temp. sensors. An AGM bank that size can eat your alternator pretty quickly. An external regulator will allow you to set a max. current to protect your alternator.

Also, some external regulators allow you to install a switch to turn the alternator off, although I don't know why you would want to do that.

Installing 2 Bosch 100 amp alternators, one on each engine, would be a good idea.

[noelex 77]

Sorry Ian I reread your post and I missed the bit about the 600AHr 12v battery bank. Running both 12 and 24v system is a bit more complicated.

What 12v appliances do you want to run?

The most common way to do this is run all the batteries as 24v with the solar panels in series also providing 24v, and a 24v inverter. There are generally only a few small items like CD players, phone and camera battery chargers, that cannot be powered by 24v. These can powered by a 24v to 12v converter.
The converters are not very expensive for low or medium powered versions, but can become dear for larger versions, so the above solution may not be appropriate depending on what needs to run on 12v.

[ian_brown]

It would probably have been better to set the house battery bank up as 24v. For most of the items you mention there are 24v versions, but I understand you already have the 12v versions so we need to keep the house bank as 12v.
Unfortunatly you cannot easily use 24v alternators to charge a 12v system.

There are three options as you mentioned before fit a 12v alternator to one engine ( this would benefit from being large as its charging a 600AHr battery bank). If doing this I would keep the 24v alternator as a spare.

Fit 2 alternators to one engine one 12v the other 24v.

Use a 24 to 12 v battery charger.


It would also be worth making up some cables so if your start battery is flat you can disconect 2 of your house batteries and rig these up in series to start the main engines. Having some premade up cables makes this much easier. Even with 2 start batteries and engines this will come in handy one day especially if you only have one alternator charging the start batteries.

[foolishsailor]

One thing to remember is that no matter how much power you have in terms of charging devices; solar, wind, multiple alternators etc. batteries can only receive so many amps at one time.

When they are very discharged they may take 100amps plus but after an hour or less they may only take 40amps and as they get closer to optimal this will drop and drop. You should not need two alternators in addition to 300w of solar to keep a 600ah bank charged. I would also think a 600ah bank may be a bit small for a charter vessel and possibly a 1000ah might be better as you will have more even and flat cycles.

It would be more efficient to attempt to calculate you average day usage in amphours and then build your bank and choose your alternator size to meet these demands

[ian_brown]

@ foolishsailor, I sent our power consumption estimate,(I overestimated everything) to the solar supplier who calculated we needed 800Ah for our needs with 60% charge coming from the solar, and a 100Amp Alternator. He said that if we had "overestimated" we could get away with 600Ah to start with but his system would enable us to add the additional 2 batteries if need be at a later date once we had done initial testing. I also have a couple of spare flexible 60W panels that I can retrofit if I want to up the Wattage later. His estimates did not take into account and advanced regulator.

Ive been looking at a few Advanced Regulators and came across Sterlingpower, does anyone have any knowledge or experience with this: http://www.sterlingpowerproductsbam....ads/proreg.pdf

from my understanding it will suit my needs of increasing the charging performance of the alternator whilst protecting the batteries and alternator in the even of a fault.

[noelex 77]

It would probably have been better to set the house battery bank up as 24v. For most of the items you mention there are 24v versions, but I understand you already have the 12v versions so we need to keep the house bank as 12v.
Unfortunatly you cannot easily use 24v alternators to charge a 12v system.

There are three options as you mentioned before fit a 12v alternator to one engine ( this would benefit from being large as its charging a 600AHr battery bank). If doing this I would keep the 24v alternator as a spare.

Fit 2 alternators to one engine one 12v the other 24v.

Use a 24 to 12 v battery charger.


It would also be worth making up some cables so if your start battery is flat you can disconect 2 of your house batteries and rig these up in series to start the main engines. Having some premade up cables makes this much easier. Even with 2 start batteries and engines this will come in handy one day especially if you only have one alternator charging the start batteries.

[foolishsailor]

Sterling Power products are quality, however I find this supplier to be the best in the industry. Their alternators also do not suffer as much performance degradation in higher temp situations as others and their output ratings for alternators and regulators are based on real world conditions.

http://amplepower.com/products/index.html

[bouncingyellow]

Quite frankly not a big fan of solar panels, the development of them makes your current installation outdated in a few years. Current top of line panels have an efficiency of 30% ,double from a few years previous. Boat arches are not cheap which must be calculated in the overall price. If money was an issue I would keep the 50 amp alternator and fit a quality battery monitor eg BM-1, plus an electro-magnetic clutch driven 100amp alternator . If you need more power than that you would be better off having a separate generator , anyway good luck with it.

[ian_brown]

@foolishsailor, Thanks for the advice, I guess you managed to read my last post before it was deleted by mistake.

I think Im going to opt for the simple solution of the 2nd alternator running at 12vdc via a yet to be decided Advanced Regulator without any manual switching option. If I find I'm low on Ahr, Ill install the extra pair of batteries

@bouncingyellow, I agree with your point about the costs and inefficiencies of Solar but we have to start somewhere.

Thanks all for the support and advice, l'll update the forum when the boat start to take more shape as Im sure more questions will arise.

Ian