Charging Inverter batteries with motor alternators

[Aussie Mike]

Gidday All, (in Aussie drawl....)

I have recently installed a 32v house battery bank and Outback 2000w Inverter/Charger as a separate system. (to start batteries, also 32v)

Im happy with the inverter (and mate controller) and battery life, it will last 12-15 hours once fully charged from the genset (20KW Kohler). It runs large refrig/freezer, lights, TV etc and once the inverter shuts down on low voltage limit of 27v, I need to run the genset about 3-4 hrs to fully charge up to 33 volts again.

My question is- if Im underway, it would make sense to connect the engine alternators to the house bank (as addition to start batteries) to charge instead of the genset wouldnt it? The only problem I can see I need to protect against is having the start batteries feed the inverter constantly, just incase all batteries are drained and for some reason the genset fails to start to recharge everything.

is there a simple way to acheive this??

My boat is a 1986 model 63' MY (galley up)

thanks in advance,

Mike

 

[SKYCHENEY]

Most of these boats originally came with 2 battery banks. The stbd bank started the stbd engine and generator and was known as the start bank. This bank was charged off of the stbd engine. The port bank started the port engine and was known as the "house bank" as most of the house loads came off of this bank. It was charged by the port engine.

I guess I don't understand your setup. Do you have a completely separate inverter bank or are you using the port(house) bank for your inverter?

 

[kwerges]

The previous owner of our 58YF added a separated, isolated alternator that only charges the inverter and house banks when the starboard engine is running. Works great...

 

[Aussie Mike]

There are 3 separate 32v banks. Port bank starts that motor and supplied the house supply with 32vDC. Starboard just starts that engine. In the generator room I stuck the new 32v bank just for the inverter. Genset has a separate twin supply 12v for starting genset and supply of 12v sysytems.

 

[SKYCHENEY]

There are 3 separate 32v banks. Port bank starts that motor and supplied the house supply with 32vDC. Starboard just starts that engine. In the generator room I stuck the new 32v bank just for the inverter. Genset has a separate twin supply 12v for starting genset and supply of 12v sysytems.

Okay, so why not just tie the house bank to the inverter bank permanently? I run my inverter off of the house bank. There is almost no chance of drawing all of the banks down at once as you still have the start bank separate. Plus you'll gain more amp/hour capacity for inverter use. Win/win in my book.

 

[Pascal]

Dedicated inverter bank is the set up I have on my boat and one the 70 footer i run and they are charged by shore/genset only

If you want to charge 3 banks from 2 alternators you need to use isolator. On the 70 we also have a house bank so the 2 alternators charge 2 engine banks plus the house bank. It s worth doing for an inverter bank if you spend a lot of time underway each day, but if you're spending a lot of time on the hook, you ll end up running the genny to charge anyway

 

[SKYCHENEY]

Dedicated inverter bank is the set up I have on my boat and one the 70 footer i run and they are charged by shore/genset only

If you want to charge 3 banks from 2 alternators you need to use isolator. On the 70 we also have a house bank so the 2 alternators charge 2 engine banks plus the house bank. It s worth doing for an inverter bank if you spend a lot of time underway each day, but if you're spending a lot of time on the hook, you ll end up running the genny to charge anyway

Good luck finding a 32v isolator.

 

[Pascal]

I know...

With a 32v system it s probably easier to add an alternator to charge that 3rd bank. Typically, Inverter banks are Big and the average alternator may not be able to cope with all the combined loads

One good reason not to tie the house and inverter banks is that inverter banks are often drawn down to near 50% because of the higher loads items like refrigeration. Better to have regular house loads, especially bilge pumps, on a separate bank

 

[GJH]

If you are really running those down to 27 volts, that bank will be killed very soon. If your inverter bank is deep cycle batteries, you shouldn't let them get much below 32 volts, where they are 50% discharged. At 27 volts they are totally dead, the same as a 12 volt battery at 10.1 volts.

 

[SKYCHENEY]

If you are really running those down to 27 volts, that bank will be killed very soon. If your inverter bank is deep cycle batteries, you shouldn't let them get much below 32 volts, where they are 50% discharged. At 27 volts they are totally dead, the same as a 12 volt battery at 10.1 volts.

I have posted this before, but here is the info from Rolls on a 32v system:

I wanted to set up my Outback with the proper charger settings for my Rolls 275a/h batteries. I called Outback and the offered to upgrade the software in my Mate for free to the lastest version so I have the most programming options. Great company! I may also add the HUB and the FLEXNET-DC to the system to get even more info.

Next I called Rolls and got their recommended settings. They are as follows:

absorb voltage 38.4
absorb time 2.0 hrs
float voltage 35.0
absorb time 24.0 hrs
refloat voltage 33.3
equalize voltage 42.0
equalize time 2.0 hrs

This all sounds about right, but I was surprised at how high the equalize voltage was. Rolls told me to monitor the specific gravity and make sure that all cells were coming up to 1265 at the end of the equalization. I will do that to make sure this works out correctly, but those were the recommendations.

I also asked about how far I can draw this back down. He told me that it would not hurt the batteries to draw them as low as 28v, but that was completely discharged. He said that most like a 50% reserve so that would make the low cutout setpoint at 31.4v. I don't know what's in there now, but we do get a 12hr period on that bank before charging, so I may just leave it alone.


I did put the inverter cutout voltage at 31.4v. As George stated, I wouldn't go below that 50% value.

 

[krush]

Contact these guys...they may be able to set up a 32v battery combiner relay (automatic) http://www.yandina.com/

Another option is just to get continuous duty contractors (aka solenoid) that you flip a switch to combine banks. I'd make sure your alternator us up to snuff and continuous duty rated.

 

[SKYCHENEY]

Contact these guys...they may be able to set up a 32v battery combiner relay (automatic) http://www.yandina.com/

Another option is just to get continuous duty contractors (aka solenoid) that you flip a switch to combine banks. I'd make sure your alternator us up to snuff and continuous duty rated.

Or use a fuel pressure switch to activate the contactors automatically.

 

[Jim saco]

I've used this place a bunch of times with good luck. This isolator is rated for 12v-48v and you can get it in 2 configurations. http://www.delcity.net/cartviewitem?item=992501&search=992501

I don't know how efficient the alternator will be at bringing up that bank quickly. But this may be a good alternative if your cruising for long periods.

 

[Aussie Mike]

Thank you all for the ideas and recommendations. It is great to be able to tap into this "knowledge bank"

Mike.

 

[davidwigler]

I highly recommend Nigel Caulder's book on this topic.

http://www.amazon.com/s/?ie=UTF8&ke...ooks&hvadid=9242658841&ref=pd_sl_93qvqziir0_b

As I recall he recommends against separate house and inverter banks. One large 32 volt house/inverter bank would be simpler, cheaper, more efficient, easier to maintain and monitor, and last longer before reaching the 50% discharge level. Plus, a separate 24 volt bank won't be charged by the alternators (unless you add another), so you are depleting the inverter bank the whole time you are underway unless you run the generator, which defeats the purpose of the inverter. The stock 32 volt alternators will probably keep an inverter/house bank fully charged while underway while also supplying normal refrigeration, lighting and entertainment loads.

 

[Pascal]

Calder's book is indeed a must own but keep in mind his primary focus is on smaller boats with limited loads and space.

It really comes down on how you use the boat. For instance if you spend a lot of time on the hook (multiple days in a row) not being able to charge the inverter bank with the mains is not an issue. On the other hand if you move everyday, then yes it s a downside

But even then... Usually you will need AC power at night to cook, maybe make water if you re in the Bahamas, and often run the Air to sleep so I find that the genset will be running at least the 3 to 4 hours a day needed to recharge

And if your usage pattern is such that using the mains to recharge is needed, adding an alternator is pretty simple

Also, keeping the house bank separated is important since that a what your bilge pumps depend on. All it would take is a tripped shore breaker for the inverter to kick in, run your house batteries down leaving the boat without bilge pumps.

 

[Boatnut]

After observing the agony a friend went through, where the boat nearly sank due to rain water when the one bank the bilge pumps ran offwent dead. I got to thinking this should never happen. Thinking about it, I made up a circuit to help avoid this situation. A simple circuit to combime batteries in the bilge pump circuit allows the pumps to have power available from all banks on board.

I am of the impression alternators come in different ratings, seems like a larger alternator could be installed. I agree a second alternator would work.

When it comes to charging batteries, I have always understood a long slow charge works better than a quick charge. Trying to accomplish quick recharge times may not be the answer.