Charging house bank from alternator?

[Panhandler]

All,

I'd like to be able to charge, or at least maintain, our house banks while running from the engine alternator. We have 12 6v Trojans split into two 12v banks, although I'm about to replace them and may do so with 8 batteries total. Twelve is a lot.... The two house banks can be combined with a 1/2/all/off switch.

The house banks are not linked in any way to the two engine start batteries, which themselves are separated by a 1/2/all/off switch. The engine alternator only feeds the engine start battery switch. I would like to be able to charge the house bank from the engine alternator so we can minimize generator run time while cruising at night (solar charges the house bank during the day).

What are my options for charging the house banks from the engine alternator power?

Do I need to worry about overloading the alternator? How do I avoid it?

Yes, I realize we should be able to last the night on the house bank as it is, but the auto-pilot pump, radar, inverter, microwave, refrigeration, and other loads draw the house bank down while cruising at night. I'll also be using the boat to tow a sonar this summer - another nighttime load. So, rather than worrying about minimizing loads, I'd prefer to charge the house bank while running without firing up the generator.

Thanks for the help!

 

[dhays]

I’m pretty ignorant, but why not consider sending all the alternator charging to the house bank. Then you can use a DC to DC charger to keep the engine start batteries topped off? The engine start batteries should never really get low as long as your engine and the batteries are in good shape.

A Balmar Duocharger or a Xantrex Echo-Charger would would.

Do you have any thrusters or windlass and how are they powered?

 

[SteveD]

Sterling Power does the trick

The Sterling Power alternator to battery charger is a very clever device that really works well. It tricks your stock, unregulated alternators into seeing a lower voltage than is actually on the house batteries so that they will put out more current than they would otherwise. It then sends a regulated three-stage charge to your house batteries (and some current to your start batteries as well). It has a temperature sensor on the alternator and sensors on the batteries. Not cheap, but they do a really good the job.

Sterling Power DC Input Alternator to Battery Chargers, 12v & 24v DC powered battery charger

 

[Bay Pelican]

We kept it simple and it worked for 20 years. 12 Trojan 105 serving as both the house and start bank. We have a separate 12 volt battery for a special use (think either generator start or helm radio). Thus the alternator on the main charges the house bank.

 

[O C Diver]

My solution was a second commercial grade alternator with an external 3 stage regulator. The Leece Neville alternator is 220 amps continuous duty and the Sterling regulator controls charging like a quality battery charger. If you don't want to add a second regulator, it might be feasible to replace one of the engine alterators with it.

Without a smart regulator controlling the alternator, they do a poor job (slow and improper voltage) charging house bank batteries.

Ted

 

[Rogerh]

Panhandler, do you have Detroit engines? I have Detroit 6V92s and am presently using a battery combiner. It eliminates the voltage drop that an isolator gives. It works to some degree but does not regulate to the house batteries. I am interested in the Sterling solution because if I am reading it correctly it provides a full 4 stage regulator for you house batteries and still a steady charge for your Engine batteries. SteveD am I reading that correctly? Has anyone used the Sterling solution for Detroit internally regulated alternators???

 

[FF]

Simplest is to use your existing rotary switch to hook in the house when running.

BUT the danger is forgetting on shut down and depleating the starts with the house.

At your local RV store you can purchase a solenoid for under $20.00

It can charge the house from the alt at its rating , usually 65 to 85A.

A switch is the simplest control, BUT it must be switched off to not discharge the start batts with the engine off.

Same problem as with rotary switch , one can make a bo-bo.

The RV folks do not have this hassle as they use the ACC terminal on the back of the ignition switch.

The simplest boat solution is to install an auto style start switch with an ACC terminal.

Cole Hersey sells quality marine key switches , again under $20.00.

 

[DavidM]

Well, there are two issues at play here: 1) How to charge the house batteries from the engine alternator and 2) Will it overload the alternators.

1) The best way to do this is to rewire the output of the alternator to go directly to the house batteries. Then use an ACR or combiner to route the power to the start batterie when the house batteries get up to about 13.5 volts. The reason is 98% of the time you will be charging the house. The starting batteries need very little charging.

You could keep them as is and just install the ACR/combiner.

2) With that big house bank that can absorb lots of amps, I would not use the Sterling regulator. That will put a continuous large load on the alternator and it probably isn't designed for that duty. If you stick with the OEM internally regulated alternator then it won't charge as fast, but it sounds like you may not need much from the way you describe your usage.

If you do want to charge fast from the alternator then I would replace it with a high output type with an external Balmar regulator.

David

 

[Tom.B]

It is not a problem at all to connect both of your alternators to the house bank! In fact, it is the more accepted way to do it. Starting the engines takes very little from batteries (you know... if they start), so all you need is a voltage sensing relay to jump from your house bank to start bank to top it off underway. I don’t understand why boat builders insisted on sending alternators to the start bank anyway. But they did, so it’s up to us to make it right

 

[caltexflanc]

Well, there are two issues at play here: 1) How to charge the house batteries from the engine alternator and 2) Will it overload the alternators.

1) The best way to do this is to rewire the output of the alternator to go directly to the house batteries. Then use an ACR or combiner to route the power to the start batterie when the house batteries get up to about 13.5 volts. The reason is 98% of the time you will be charging the house. The starting batteries need very little charging.

You could keep them as is and just install the ACR/combiner.

2) With that big house bank that can absorb lots of amps, I would not use the Sterling regulator. That will put a continuous large load on the alternator and it probably isn't designed for that duty. If you stick with the OEM internally regulated alternator then it won't charge as fast, but it sounds like you may not need much from the way you describe your usage.

If you do want to charge fast from the alternator then I would replace it with a high output type with an external Balmar regulator.

David

I second this post as the most reasonable solution so far offered, based on the limited and somewhat vague info at hand. . But I have a question for the OP. It sounds like you have two engines but only one alternator? What exactly is the set up.. including the size of the alternator(s), battery chargers involved, generator?

Methinks you'd be best served having a good marine electrician evaluate your whole set up in person, as we are shooting in the dark to a large degree here.

 

[john61ct]

Yes ACR is the cheap easy good enough way to go, high amp Blue Sea if leaving alt output on Starters.

Alts to House with low-amp Echo Charger a bir better.

Sterling DCDC only if expensive special, sensitive House chemistry, or to correct for voltage drop over a long run.

 

[Panhandler]

Thanks for the great information. Sounds like rerouting the alternator output to the house bank and then using an ACR or echo charger to the start bank is the simplest for now.

Is there a danger of this overloading or overheating the alternator because of how much power the house batteries could accept?

Single Cat 3208NA with a single alternator. Windlass currently wired to one engine start battery.

 

[DavidM]

Thanks for the great information. Sounds like rerouting the alternator output to the house bank and then using an ACR or echo charger to the start bank is the simplest for now.

Is there a danger of this overloading or overheating the alternator because of how much power the house batteries could accept?

Single Cat 3208NA with a single alternator.

Probably no. If the house batteries are at 75% or greater state of charge when you start the alternator, the fixed mid 13s voltage output of the internal regulator won't put out that much current, probably less than half of the rated alternator output. Only if the batteries are significantly discharged (below 50%) will the current be high and for a long period.

I believe that the Cat alternator can be replaced with a fairly inexpensive Leece Neville high output alternator that has connections for an external regulator like the Balmar. For less than $500 you could upgrade both.

Here is a thread on TF that discusses a high output alternator for the 3208- http://www.trawlerforum.com/forums/s4/cat-3208-alternator-improvement-20560.html

If you upgrade make sure that you increase the wire size to handle the increase current.

David

 

[tiltrider1]

Echo chargers are now referred to as DC to DC chargers and if you decide to go the way of an ACR you will want to use a “Smart ACR”. Smart ACR protect the start batteries by only allowing the correct voltage to be passed through.

 

[CMS]

Single Cat 3208NA with a single alternator. Windlass currently wired to one engine start battery.

If this is the standard Prestolite/Motorola/Leece-Neville 8MR alternator, on a 3208, then you will want some level of temp protection. The internal regulators on these alternators do not have any sort of thermistor driven voltage reduction circuit and they will literally run until they burn out, if you let them.

They can be converted to external regulation so that current limiting and an alternator temp sensor can be used to protect them.

Leece-Neville 8MR External Regulation Conversion


.

 

[john61ct]

Echo chargers are now referred to as DC to DC chargers and if you decide to go the way of an ACR you will want to use a “Smart ACR”. Smart ACR protect the start batteries by only allowing the correct voltage to be passed through.

No, Echo Charger is a specific branded device, low amps and is voltage following with a drop and limit.

Nothing to do with a DCDC charger.

Please post a link to this so-called "Smart ACR".

All ACRs are voltage following, which is fine 99.9% of the time.

This is the most reliable and robust ​ https://www.bluesea.com/products/7620/ML-ACR_Automatic_Charging_Relay_-_12V_DC_500A

 

[Ski in NC]

It could overheat the alternator. Best to try combining the banks and monitor alt temp. Seen a couple alts fried by trying to recharge a big house bank.

There are regulators out there that include a temp sensor that is affixed to the alt. Drops excitation if alt gets too hot. Seen that, but don't recall the brand. That's the way I would go.

Unfortunately, the 3208 alternator fits in a little gap in front of the right bank exh manifold. Not much room to put a physically larger alt in there.

 

[john61ct]

Convert as MS said, Balmar MC-614 VR will protect both the alt and bank.

Custom rebuilders can provide higher amp alts to fit in the stock spot, but try using the above VR first.

 

[FlyWright]

Your issues are very similar to those others have posted about here in recent months. Here's a thread that does a great job of explaining electrical systems. I think you'll find your solution here.

http://www.trawlerforum.com/forums/s4/battery-switches-isolator-31495.html

Whenever you see something written by CMS (Compass Marine/Mainsail/Rod), read it twice and commit it to memory. It's straight from the expert's fingertips.

 

[Panhandler]

Thanks for all the awesome advice and the links to the other threads. I note after reading a post by CMS in another thread, we have a lot of "dead lead" aboard. I don't really need four start batteries for one engine and one generator.

Thanks also for the notes on the 3208 alternator. I'll double check the type and model.

One other option - we've got stern thrusters that I don't use. The hyrdraulic pump is engine driven with two belts and mounted off engine but close. I assume I could just bolt in a new high output alternator that uses a similar two belt system? Of course a little mount fabrication might be required. When I looked at the high output marine alternators they were all north of a boat buck. Since my mount can be custom, are there any inexpensive options? Thanks!

 

[Tom.B]

Thanks for all the awesome advice and the links to the other threads. I note after reading a post by CMS in another thread, we have a lot of "dead lead" aboard. I don't really need four start batteries for one engine and one generator.

That may or may not be true. While it is true that may be overkill, setting up that start bank with dual purpose batteries would be a smart play. It could provide a stout backup house bank in the case of a failure in the main house bank. For reference, I have 8 6v golf carts and 3 12v dualies as start/backup house.

Like other have mentioned, you really should combine your house into a single bank.

 

[caltexflanc]

You could give the guy at ZRD a call, they do some really nice work fitting new alternators. Perhaps the world's wierdest e-commerce site, but I've seen their work. They were helpful when I was looking to add capacity on my old boat via an additional alternator. The site and the guys there are actually a wealth of info.

ZRD Electric Designer OEM - Your Source for 24-Hour Power, DC Generator, Alt, ...

 

[tiltrider1]

http://www.magnum-dimensions.com/si...s/spec/ME-SBC_datasheet_revC_#64-0600_web.pdf Link to smart ACR.

Echo charger was a dc to dc charger developed by a company called Ample Power. Xantrex now markets a dc to dc charger under that name. I am not say all dc to dc chargers are equal.

 

[O C Diver]

One other option - we've got stern thrusters that I don't use. The hyrdraulic pump is engine driven with two belts and mounted off engine but close. I assume I could just bolt in a new high output alternator that uses a similar two belt system? Of course a little mount fabrication might be required. When I looked at the high output marine alternators they were all north of a boat buck. Since my mount can be custom, are there any inexpensive options? Thanks!

My 220 amp Leece Neville was 6 or $700 with the pulley. Beware of Chinese knock offs!

Ted

 

[john61ct]

You could give the guy at ZRD a call, they do some really nice work fitting new alternators. Perhaps the world's wierdest e-commerce site, but I've seen their work

Wow! I taught 3rd-6th graders basic HTML classes in the mid-90's, and most created better-looking sites than that.

But hey, it does convey the information, and in fact is very convincing, obviously not a marketing oriented company, so their engineering **must** be good!

 

[john61ct]

http://www.magnum-dimensions.com/si...s/spec/ME-SBC_datasheet_revC_#64-0600_web.pdf Link to smart ACR.

They don't call their product a "Smart ACR"

All ACR/VSR/combiners do what that does, as I said voltage following, as they all have been since Ann-Marie Foster @ Yandina invented the product category (highly recommended still!)

What is special is the adjustable open/close setpoints, I've seen less than a dozen VSR products with that feature.

Looks like a great unit!


>> Echo charger was a dc to dc charger developed by a company called Ample Power. Xantrex now markets a dc to dc charger under that name.

If Ample ever used that specific name they stopped a very long time ago, and I doubt it was a true DCDC charger design.

What is now sold by Xantrex as the Echo Charger is a very robust and successful design, and has been around virtually unchanged for 30 years now.

A bit different from other combiners, but also voltage following, as I said with a bit of a drop, plus an upper limit, you could say buck conversion.

 

[john61ct]

My 220 amp Leece Neville was 6 or $700 with the pulley. Beware of Chinese knock offs!

+1

eBay can have great deals, sometimes $200, even new not much more.

Pulleys can cost more than the alt.

Beware of the torque required to drive the big-amp ones when actually loaded, def want a serpentine belt, soft start and derating VR, and a disable switch at the helm when your propulsion needs the HP back.

I wanted to set up a 500+A @24V Hummer alt, until I was told it alone needs ~28HP at max output

 

[O C Diver]

My 220 amp Leece Neville maxes around 10 HP. You need to be over 800 RPM to get 100 amps output. Have an 8 groove serpentine belt driving only it off a second crank pulley. Whole system works extremely well.

Ted

 

[john61ct]

Assuming that's at nominal 12V, @4x the load makes my 28HP likely an underestimate!

8-O

 

[TDunn]

This is a very simple fix. Wire the alternator directly to the start batteries. Then connect the house bank to the start batteries with an automatic charging relay (ACR) sized to take the full alternator output. Problem solved. No fooling with switches. This setup will charge the start battery until its voltage goes above the ACR kick in voltage at which point the house batteries will be connected to the start batteries AND the alternator. When the engine is off the ACR will open and disconnect the start and house batteries. If you have two house banks, put a second ACR between the house banks. That way the alternator will charge all three banks. Simple, fool proof and cheap.