using a4 alt to charge house batteries

[Hymodyne]

I currently have a small solar panel that maintians the charge on the twin marine batteries that I use for my house power. Is there a way, say, by wiring the house batteries to the Vreg from the engine, that I can use the alternator's charging power to recharge the other batteries? The solar panel has an external regulator, but I believe it would be quickly overloaded by the alternator.

James

[Marian Claire]

I have my batteries charged by the alternator/VR via the battery selecter switch. I also have a 60 W panel that runs to a small charge controller then to the #1 bat. Never had any issues. Elecrical is not my best field so hopefully others will chime in. Dan S/V Marian Claire

[edwardc]

What you want is something called a charge combiner. It will connect the batteries together when charging, and isolate them the rest of the time.

There are several different types, from a simple relay style one (often sold in WM), to a simple set of high-current isolation diodes (which can cause voltage drop issues), to fancy low voltage-drop electronic ones that have the best of all worlds but cost (lookup Hellroaring Technologies to see one of the better examples of this).

Selection criteria are:

• Manual/Automatic Operation
• Power Consumption
• Voltage drop and its effect on your charging system(s)
• Cost

The thing you absolutely want to look for in a charge combiner is that it is automatic! The last thing you need is to wake-up one morning and find that both your house and starting banks are dead because you left a manual combiner turned on!

EDIT: Link to Hellroaring Technologies

[sastanley]

Originally Posted by edwardc

What you want is something called a charge combiner. It will connect the batteries together when charging, and isolate them the rest of the time.

There are several different types... to a simple set of high-current isolation diodes (which can cause voltage drop issues), ...

I have one of these types and it works great for me. I also have an adjustable voltage regulator on the alternator to compensate for the voltage loss (of approximately 0.70-0.75 volts).

On the other side of the isolator, I have a Gr 24 start battery, and two Gr 29 batteries stacked together as the house bank.

I also have a small solar panel with regulator & alligator clips..My standard practice has been to simply swap this from one battery bank to the other each visit to the boat. The little cheap regulators that go with solar panels will NOT handle the alternator...mine is max rated at 7 amps...good thing my 3.2 watt solar panel churns out a whopping ~220 mA.

[Hymodyne]

Originally Posted by edwardc

What you want is something called a charge combiner. It will connect the batteries together when charging, and isolate them the rest of the time.

There are several different types, from a simple relay style one (often sold in WM), to a simple set of high-current isolation diodes (which can cause voltage drop issues), to fancy low voltage-drop electronic ones that have the best of all worlds but cost (lookup Hellroaring Technologies to see one of the better examples of this).

Selection criteria are:

• Manual/Automatic Operation
• Power Consumption
• Voltage drop and its effect on your charging system(s)
• Cost

The thing you absolutely want to look for in a charge combiner is that it is automatic! The last thing you need is to wake-up one morning and find that both your house and starting banks are dead because you left a manual combiner turned on!

EDIT: Link to Hellroaring Technologies

Ed, can you recommend one of these for me, based on the set up I have described?

james

[edwardc]

Originally Posted by Hymodyne

Ed, can you recommend one of these for me, based on the set up I have described?

james

Yes, but I'll need to know a little more about your setup, and about what you want.

From what you've written, it sounds like you have two "marine" batteries in parallel for your house bank. I'm assuming there is a smaller, dedicated, starter battery for the engine.

Questions about your setup:

1. Are the "marine" batteries true, deep-cycle batteries?
2. Are they wet cells, gel-cells, or AGM?
3. Is the starter battery Wet, gel, or AGM?
4. What is the combined amp-hour capacity of the house bank?
5. What is the amp hour capacity of the starter battery?
6. What is the full-sun output of your solar charger?
7. Do you have a "smart" 3-stage charge system on the alternator, or just the standard "automotive" type regulator?
8. Do you have a shore-power charger?
9. If so, is it a "smart" 3-stage charger?
10. Does the shore power charger have multiple outputs for charging multiple batteries?

And some questions about what you want from the system:

1. How much engine runtime do you want per day to keep your batteries charged?
2. What is your daily amp-hour power budget for the house bank?
3. How much do you want to spend?

All of these will affect the type of charging system you want. The charge combiner is just one piece of the system.

The very simplest system is probably a manual Off-1-Both-2 switch. It is cheap, gives you lots of flexibility, but suffers from the big flaw that you must remember to manually switch it from "Both" to just the house bank after you're done motoring. It also allows the big DC transients at starting to effect all of the electronics.

The more complicated but fully automated system would use one of the two-sided Hellroaring combiner/isolators to use all charging sources to charge all batteries, while still keeping the engine/start battery isolated from the house bank and all the electronics. And then there are hybrid systems that use the 4-way switch and a combiner/isolator. Take a look at some of the circuits on the Hellroaring page:

Simple starting battery isolation
More complicated isolation

And I strongly suggest you get & read the battery chapter in Nigel Caulder's book.

[sastanley]

Originally Posted by edwardc

And I strongly suggest you get & read the battery chapter in Nigel Caulder's book.

+1! An excellent reference. This is the equivelant of the Moyer Manual for the rest of your boat.