I am unhappy about the time it takes to charge the batteries and the drain from the refrigerator/freezer units on my B40 #247. I have the 53hp Yanmar with the stock 80amp alternator which puts out no more than 13.5 volts (which is the Yanmar spec) which is not enough to keep my two 4 D house batteries (wet cell) fully charged.

After 3 days out on our first cruise, the house battery bank was drawn down so low that the refrigerator/freezer compressor shut down. Each day we motored for at least 2 hours – but that was not enough.--I would think one hour would be more than sufficient.

To resolve this I will add a separate switch to allow me to shut down the freezer unit while running the refrigeration (apparently Beneteau did not think of this). I also want to upgrade the alternator and add a smart regulator. I know I should be concerned about too much strain on the engine and the maximum size for the V belt that this engine can handle. A larger alternator may need a bigger belt. I don’t want to upgrade to AGM batteries for a few years; the boat is only in its first season.

I’m hoping that some of you have upgraded your charging systems on this engine.

Any recommendations would be appreciated

Views: 487

Replies to This Discussion

Hi Gary,

I too wish that the refrigerator and freezer were on different circuits and could be switched separately. I did figure out a workaround. Since I don't use the freezer for cold storage, I simply turn the thermostat ALL the way down. If you really turn it, it will click, completely shutting down the freezer as opposed to just turning down the temperature. The switchoff takes about five seconds total.


I too wanted better charging, but didn't want to embark on a big alternator replacement project with a separate regulator - though that would be the best approach. Instead, I added a Sterling "Alternator to Battery Charger". This is an easy-to-wire box that acts like an external regulator without requiring you to replace or even modify your existing regulator. I doubt that it does as well as a high quality alternator plus an external regulator, but it's infinitely better than the stock setup.

Same engine and alternator on a B-40, hull# 182. I get 14.2 volts when the batteries are fully accepting a charge and refrigeration is not running. I will get 13.2 volts if the refrigeration is running and autopilot is operating as well. It normally takes me 2-4 hrs to fully recharge the batteries when at operating rpm. I do run down the batteries at anchor in less than 2 days when not operating the engine. The yard did increase the positive cable size to the main electrical panel to a size 4,. I think. I would check voltage when running at the battery terminal and not depend on the voltmeter at the panel. It usually reads several tenths low. It should be outputting at least 13.9 to 14.2 volts when batteries are accepting a full charge. If not, the the voltage regulator needs to be looked at. Also check you electrolyte levels in the 4Ds and engine battery.


Lets first consider how many amp hours (ah) your boat uses in a day before considering new equipment. Also take into consideration that a 80 amp per hour alternator will not put 80 amps into your battery bank in an hour unless you are running the engine at close to max rpm for an hour (very bad idea). Even then I doubt it will give you 80 amps. So running your engine for one or two hours a day will not replace the amps(ah) used by the refrig and freezer (they use about 5 amps per hour or 120 amp hours per day) in a 24 hour day. Basically if you are running your engine at 1500 rpm for two hours you "may" be putting 80 amps back into your batteries (not likely though). You are also using lights ( hopefully leds), radio, toilets (if you have electric head), instruments, pumps, etc. These boats love electricity! If you are using the inverter you gotta count those amps also.

You didn't say how many amp hours your batteries are rated so we don't know their size and are unable to figure just how long it should take to recharge your house bank with your alternator.

Installing a high output alternator is an idea but 1.) you will still have to run the engine to charge up the house bank when anchored for longer periods and 2.) there is the question of additional strain on engine front bearings to be considered, 3) Can be pricey if you do not know how to fabricate braces and do install yourself.

There are other solutions such as 1). increasing your house bank size (keeping in mind the size of your alternator and your battery charger), 2.) Adding solar panels to help keep your house bank charged up, 3.) Turn your freezer off to reduce ah consumption, 4.) Turn off all unnecessary electronic equipment at anchor, 5.) Wind generator (if you are in a historically windy area), 5.) portable generators (such as Honda eu2000i weigh is 35lbs).

My wife and I own  2008 B43 #19 with two electric heads frig, freezer, and all electric stuff. We installed one of the single most important piece's on board to help.  The battery monitor. Once we understood and could see how much power was being consumed we decided to go with the Honda gen as our solution. We chose this equipment based on cost and ease of implementation. While in Florida's Dinner key marina (on mooring) for 8 days awaiting good weather for our passage to Nassau this past March we kept our batteries charged by recharging our 400ah bank every other day for about 3-4hours with the gen. We charged batteries from 10am-2pm every other day while on mooring. The unit is very quiet and the hours of usage were civil.

I am not saying this should be your solution, you must first determine your ah use then choose your own path.

The charging system supplied by the builder is relatively good up to roughly a 400ah house bank. Anything larger than a 400ah house bank would necessitate consideration for replacement of battery charger, and maybe alternator to charge the larger bank in a timely and efficient manner.

I also doubt our alternator puts out 14.1 volts but, I do know it puts out at least 13.6-.8. and fills our 400ah AGM bank to 100%. The amount of time it takes to do this depends on how depleted the house bank is once charging commences.

.A good battery monitor will give you the correct (+ or -) status of your battery ( empty to full), charging voltage and it will tell you how many amps you will put into your battery in an hour at its current rate of charge. The numbers you see across your boats network (voltmeter) are only accurate when the battery is fully charged with no draw on the system and at rest, once you start drawing power the boats voltmeter is basically useless as an indicator of battery status and system voltage.

You may not need new batteries or alternator, first determine what your amp hour needs are and what your current system can supply, then, make the call. Hope this helps!

Hi Gary,

Some points to consider;

Alternators steal away some of your hp. A second alternator of same size will take away about 2 more hp.

Don't expect an internally regulated alternator (or whatever) to fully charge your batteries as a smart battery charger does.

You will probably never see an 80 Ah output from your alternator. Besides take into accunt that engine room fan draws about 4 Ah itself.

Running your engine at full RPM doesn't help to charge better or faster. 2200 RPM is sufficient for maximum output.

To stay at anchor for 2 days, you must increase your house bank capacity to at least 400 Ah. (Next comes upgrading your charger of course. Don't worry about alternator, it will also manage this load same way it used to be.) AGM's have the highest acceptance rates and charging regimes are similar to lead acid batteries which makes them preferable.




We had the same problem at the beginning

Snce them we installed a Sterling A2B ( ) that helped a bit ...

Next season we'll install some solar panels 

I agree that the charging system greatly benefits from a multi stage external regulator. I changed out the stock alternator and added an external regulator, keeping the electrical connections plug and play for the original alternator as a carried spare,

I installed a Balmar kit, 70-YP-110-KIT, and it fit perfectly. I have hull#8 B43, 2008.

I have 660 amp hours of AGM batteries. The smart regulator has an adjustment that you can set to reduce the field voltage of the alternator to reduce the maximum output, thus addressing the belt loads.

Great system. Not exactly cheap, but a very solid performing system now. I also added a Victron battery monitor to know what was actually going on.



B43, hull #8

One way to cut down on the amps consumed by the fridge and freezer is to keep the coils on both compressors clean. The grills in front of each are glued on but can be gently pryed off to allow thorough cleaning. Also keep both units frost free as much as possible. We added a plastic coated wire rack to the bottom of the freezer which allows for better air flow and the ability to keep the thermostat set at a higher temp resulting in less run time. Another addition are synthetic ice cube packs. We keep some in both the fridge freezer and main freezer. They help keep the temps in both stabilized. If loading the fridge for a long trip make sure you leave room between the food and walls. Doing so improves air flow.Doing all of the above we've been able to keep the amps consumed by both units down to apx 3.5 and hour.

As for the stock 80amp alternator I've never seen more than 50 amps out of it. (per a Victron battery monitor not the panel meter) That was with the 450 amp house bank at apx 50%. (Trojan T105 6V wet cells) We had 2 4Ds when the boat was new and they couldn't handle more than a weekend. Ours were Deka Dual Purpose and were likely only rated at apx 325 total. The Trojan T105s do a great job for 3-4 days with some recharging via stock alternator but after that we need to either motor for a couple of hours or plug into shore power. I'm planning on replacing the stock alternator with an Electromaax and external regulator. Dependig on which alternator will also add serpentine belt pullys to avoid the bearing wear issues. Will also add two more T105 to bring the total house up to 675ahr. Eventually will add a couple of solar panels over the biminin. Just waiting on the boat bucks to do so. A number of people go the Honda portable generator route as James suggest just not something we plan on doing.

Good luck



Latest Activity

Mike Brown commented on CAN DRAC's group Beneteau 40 & 43
"Robert glad to hear you go the problem solved. mike"
Robert & Sandy commented on CAN DRAC's group Beneteau 40 & 43
"Thanks for all your comments my friends at Seaknots. The halyard has been rerun without passing through the small stainless steel eye, as seen easily in the pic provided by Chris on 17th August. All furling now takes place without any undue effort,…"
Mike Brown replied to Jochen Vetterlein's discussion O43: Good tracking on starboard side - poor on port side in the group Beneteau 40 & 43
"Well at least you’ve narrowed it down to the Genoa. I doubt here’s any issue with the hull or running gear. Nor do I think the slight list you have will have an impact either as many boats have the same based on how full the water and or…"
Oct 9
Jochen Vetterlein replied to Jochen Vetterlein's discussion O43: Good tracking on starboard side - poor on port side in the group Beneteau 40 & 43
"In the meanwhile, I performed some sailing tests trying to be as impartial as possible. I was sailing close hauled on the starboard and port side. I used the autopilot steering the boat at 37 degrees to the apparent wind. Apparent wind was 12 to 19…"
Oct 9
James Taylor replied to Jochen Vetterlein's discussion O43: Good tracking on starboard side - poor on port side in the group Beneteau 40 & 43
"Sounds like your rigging may be in need of tuning????? (Owned B43#19 for 10 years), Sailed from Mass to Tampa to Bahamas with it, great boat, no major issues at all. Boat has flat bottom basically so no need to put rails in water. I found it a very…"
Oct 9
Mike Brown replied to Jochen Vetterlein's discussion O43: Good tracking on starboard side - poor on port side in the group Beneteau 40 & 43
"I’d also do a test using only the main. The more testing you do the more likely you’ll find the problem. I’d also check to see how much the leeward shrouds sag during all the tests. Let us know what you find. Good luck Mike"
Sep 27
Jochen Vetterlein replied to Jochen Vetterlein's discussion O43: Good tracking on starboard side - poor on port side in the group Beneteau 40 & 43
"It is only when sailing close-hauled. Unfortunately, this is the only course, where performance really matters. I‘m going to perform two tests: - Sailing with genoa only (track cars on the same position). In this case any (unequal) trim…"
Sep 27
Mike Brown replied to Jochen Vetterlein's discussion O43: Good tracking on starboard side - poor on port side in the group Beneteau 40 & 43
"Our 43 had a shaft drive. Depending on how much water or fuel that was in her she would sometimes have a very small imbalance. Nothing that would cause her to sail unevenly. Do you have the problem on all points of sail? Is it more on any particular…"
Sep 27

© 2021   Created by CAN DRAC.   Powered by

Badges  |  Report an Issue  |  Terms of Service