Improving the C320 Charging System - Approach 2


Technical Articles

John Langford's electrical upgrade discussed two options to improve the cruising capabilities of the Catalina 320. The first and least pricey was to modify the existing alternator to remove the internal regulator and add a smart" external regulator. This provided the boat with a nominal 160 amp-hour capability, assuming the second 4-D battery was dedicated to starting the engine and not used as a house battery. In actuality you then have between 50 and 80 amp hours available depending on how charged your house battery is and its "health". He also installed an ammeter/amp-hour meter to have the ability to determine the charging amperage to his batteries and the amp-hours lost while on the house bank at anchor or at a dock without shore power.

Roy Kraft, #187, "Sea Wings"

I decided to take the second, more costly approach since I already had the ammeter/amp-hour meter installed with my LINK 2000/Freedom 10 combination. This revision involved: 1. Adding a dedicated starting battery. 2. Removing the Lucas 55 amp alternator and its internal regulator and 3. Installing a new Balmar 75 amp alternator with smart external regulator. I wanted to be able to keep my starting battery fully charged while paralleling the two 4-D remaining batteries. Thus I would have a nominal 320 Amp hours or a useable 100 to 160 amp hours available before recharging. I looked at several ways to do this.

With a goal of installing a minimum of "new" wire I decided to place the new start battery (Group 24 750 CCA/60 AH West Marine) under the port settee just forward of the Nav station. The existing red cable (1/0) leading to house battery #2 was removed and pulled through its routing channel to the plus of the start battery which now becomes battery #2.

I installed a new short cable (1/0) between the positive posts of both 4-D's. putting them in parallel. A new 16 foot length of black cable (1/0) was run through the open channel to the negative distribution point (in my case the meter side of the Link 2000 shunt located under the stbd setee near the two 4-D's). Thus I now had both 4-D's on switch position ONE with the start battery on switch position TWO. The problem of charging the start battery was solved by installing an Ample Power "Isolator Eliminator". This box is not a diode isolator and has almost zero voltage drop. It runs between the house bank and start bank with No. 12 wire and takes its charge current (maximum of 7 amps) directly from the house bank WHEN the bank is charging. I could just have easily installed a West Marine "Battery Combiner" for less money but the eliminator is a bit more sophisticated. At this point the system was tested making sure all wiring was correct and secure. On the Link I read the house bank as batt #1 and the Starter Bank as Batt #2. So far so good.

Now came time to install the Alternator. I bought a Balmar 901-75 alternator with the Balmar ARS III "smart regulator". Removal of the Lucas was easy since I labeled all wires as they were removed. I found the Balmar fit the existing space and hole pattern of the Lucas; however, the existing upper mounting bracket needed to be modified to locate on the aft side of the alternator. This required some milling from the bottom of the bracket as well as cutting and re-welding the bracket mounting holes. I also had to have two shims made and a longer 6mm screw to re-orient the bracket. Then in order to line up the 3 pulleys, I had the bottom bracket modified to elongate the holes. This bracket is now adjustable to line up pulleys. Since the starter is dedicated to the starter battery only (while in switch position 1) and the existing wiring uses a common red power cable in series with the alternator it was necessary to remove this cable and run a dedicated no. 2 gauge cable from the alternator to the common post of the 1-2-BOTH switch (after removing the red wire between the alternator and starter).


I mounted the regulator in the space under the aft bunk next to the engine compartment. An alternate spot would have been next to the coolant tank but a little crowded for me. Balmar provides a nice harness running between the alternator and the regulator. After all wiring and dressing of wires was complete I gave it a preliminary check. I then put on about 6 amps of lighting for the night and ran the house bank down 100 AH's. When starting the engine the next day it immediately went to +62 Amps and the battery charged from -102 AH's to -20 AH's in about 1.5 hours! I had to adjust the regulator since it was set for gel cells but instructions are good. Finally, I removed the engine instrument panel and made a screw driver adjustment of the tach. It appears very close to what it was before. It is a good idea to put some tape on the binnacle so you can mark various RPM's BEFORE starting the project as I guarantee your tach will need to be adjusted.

I now have a hefty house bank and won't be reluctant to leave the frig and anchor light on all night. I leave the 1-2-Both switch in the #1 position without worrying about draining or over-charging the start battery. Should the start battery fail I can still switch to the BOTH position thereby paralleling all three batteries for an "emergency" engine start. Best of all I can spend more time sailing and less "charging".

Balmar has asked that I send them my Lucas so they can ensure the 901 becomes a true "plug and play". I would check with them before investing as the bracket modifications took the most effort and about $40. Also, since you don't need an isolated ground alternator you might beat the price I paid.

Cost of it all:

Alternator and ARSIII $ 630.00 Defender
Eliminator 225.00 "
Group 24 Battery 59.95 West Marine
Wire/Lugs/etc 200.00
TOTAL $1,094.95

Was it worth it? Considering the man hours spent, I sure hope so. By the way, if you don't have a Link 2000, I would recommend either the Cruising Equipment Link 10 or Link 100. There is little need to monitor the starting battery as I did since it should always remain charged. Since the Link 2000 is a double shunt I decided to use it rather than not. One more comment is whether or not to install isolation between the start and house bank. One could save the money by manually switching to position #2 for starting and charging the start battery and switching back to No. 1 for using the house bank. I'm convinced that sooner or later I'll leave it in the wrong position and either I or my mate will turn on the microwave and kill the start battery. You only need to do that 3 times and you have paid for the combiner.
Roy Kraft, #187, "Sea Wings"


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Is there any reason why you wouldn't install a larger Ah alternator such as the 110 instead of the 75. Not much of a price difference between the two.
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