Bavaria 56 - 40A battery charger too small ?

[VINCE]

My 2015 Bavaria 56 appears to have an inadequate charge level from the 40A charger fitted.  Could be my own fault - I could have specified the 80A charger.  I am now thinking of doing this upgrade but I wonder if the wiring is adequate for the 80A.  Does anybody know if it is ?  And can you tell me the names and types of chargers fitted - I can't go and look at the boat because it is in Greece.   Many Thanks

[tiger79]

What is the Ah capacity of the domestic bank?

[Symphony]

The charger is likely to be a Cristec - it is on the smaller boats built in 2015. The size is determined by the capacity of your battery bank. Rule of thumb is 10% of bank capacity, so your current charger will support a total bank of 400AH - that is house and starter plus bow thruster if it is also wired to the charger. However, the starter and bow thruster battery rarely need any charge, being quickly charged from the alternator, so if your house bank is not significantly more than 400AH then you do not need the bigger charger. My 33 has 285 in the house, plus 95 each for the start and bow thruster, so total of just under 400 and a 40 amp charger which is more than adequate.

Worth fitting a battery monitor on the house bank so that you can better understand your usage pattern.

[geoff]

I have a 40amp charger and 440ah of domestic capacity. It has not given any problems in 16 years. Geoff

[Craig]

I'm assuming you don't have some exotic lithium batteries that can accept massive charging rates. The 40amp charger mentioned is the shore power charger. Does it really matter how long it takes to charge a battery bank under shore power as most boats typically can plug in for as long as they like. The "Rule of Thumb" mentioned by Symphony is about right. I would even think that an 800amp/hr battery bank would be adequately charged using a 40 amp charger.

I'm wondering whether the question has arisen because the batteries have a problem and are not holding their charge.

My solution to the electrical situation on my Bav 38 is as follows:-
1. 115amp alternator on engine more than adequate for my 440amp/hour domestic bank and the 75amp/hour starting battery.
2. 40amp shore power charger more than adequate.
3. 120watt solar panels not enough for anchoring long term but great to keep batteries charged if Refrigerator not on.
4. 1000watt generator rarely used but great for anchoring long periods, more so after  changed the 1200watt water heater element with a 500watt element so that I could charge batteries and heat water at same time. ( getting a generator was a waste of money in my opinion)
5. my 2000watt inverter can easily handle the microwave and other 240v appliances, ( I usually ensure that I am using the engine if I use the microwave)  and if on shore power, the inverter allows power directly from shore.

Given that motoring into or out of harbour usually generates enough power to top up batteries, I don't bother to plug into shore power whilst at home.

I'm sure this issue is not charger related but battery and/or large current draw related.

Craig
Shirley Valentine
Gold Coast
Australia

[VINCE]

Vince here again - The battery charger is used almost exclusively for charging the batteries from my generator which has a capacity of 6.4 KW.  I am afraid that the boat has rather a lot of electrical gear aboard.  I have a total of six batteries - one for engine, one for bow thruster, and four coupled together for the other domestics.  I very rarely plug into shore power.  Each of my batteries is 92 Ah - so the total load is 6 x 92 Ah.  I think that the generator needs to be on much more than it is but I have no other use for it after about half an hour.  The boat has two refrigerators which are also heavy users of power.  I wondered if an 80A charger would put in more charge when the generator is on.  Thank you all very much for responding to my questions.  Do you know if the boat's wiring will take the 80A if I change the charger ?  Is there maybe a fuse somewhere that will blow or something.  I have very little info on the boat's electrical systems.  If you know where I can get more info it would be very useful.  Thanks

[Symphony]

It is the rate at which the batteries will accept the charge that is important. As I said earlier, you really should not need any charging for your start and bow thruster batteries because although current draw is high, the amps used is low and the engine will bring them back up to full charge in minutes as your split charge system will favour those batteries before putting any charge into the house bank.

So, you only have to worry about your house bank which is well under 400AH and a 40A charger is more than enough. That bank simply will not accept any more charge.

If you have a battery monitor you will be able to understand you power usage better, and I suspect with all your kit the next step would be to increase the capacity of your house battery bank and you could reasonably add two more batteries (if you have room) which will increase your capacity by 50%. You may well find your current charger will cope with that, depending on how much you run them down before charging. Even if you have a larger charger you may not necessarily reduce your running time of the generator as you will still have the limitation of the rate at which the batteries will accept the charge. Little and often is the best way to keep the batteries fully charged - that is not running them down too low before charging.

You don't say if you have solar panels, but this is the best investment you can make as particularly in the area you sail they will be putting in charge all day and reducing the need to run the generator.

[Salty]

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You don't say if you have solar panels, but this is the best investment you can make as particularly in the area you sail they will be putting in charge all day and reducing the need to run the generator.

They really are a great investment, though finding somewhere to place them can be a bit of a problem on a smaller boat. They are however very reliable, they don't make any noise, maintenance consists of an occasional drop of fresh water and a soft cloth, and as Symphony indicated they just get on and do the job during daylight hours without any fuss or bother - brilliant !!

[VINCE]

Vince here again - Yes I have a couple of solar panel - 50 watts each I think - they put in a couple of amps ( I know - I have measured it ) but are not really big enough - many thanks for your assistance - I will consider putting in a battery monitor.

[Craig]

Also, a 6.4kw generator is much too large if your main use is charging the batteries. To charge batteries at 40amp maximum you only need a generator of about 1/2 kw. A generator of that size is really designed for air-conditioning on the boat.

I agree with Symphony. Your best investment would be a larger battery bank, particularly if your current draw is more than 100amp/hrs per day. Increasing solar panels should also be considered.

Craig
"Shirley Valentine"
Gold Coast
Australia
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[Lyra]

The key issue is that you say that you operate the generator for only half an hour - unless you are starting with a nearly full battery then this is clearly not enough time, even if you put a much larger charger. As the batteries get charged they accept less and less current. Getting to ~80% of charge level can be quick and will depend on the capacity of the charger, however the last 20% will take time regardless of charger max current.

[Kibo]

I have a 2014 Bav Vision 46 with genset, wind gen and two 100 w solar panels. I have a Victrex battery monitor and same house battery/bowthruster/engine start set up as you do.

I run a freezer and a fridge along with the usual miscellaneous items, lights etc.and average draw is about 9-10 amps. When fully charged my battery monitor tells me that I have about 24 hours until discharge so I run either my engine (usually when moving, obviously) or my genset for about two hours per day to keep topped up. When charging with engine about 70 amps is going into the battery, with genset the monitor indicates about 90 amos input.  I think from previous comments that your expectation to run your genset for 30 minutes and hope to keep topped up is not realistic.

We liveaboard for 4 months of the year so I have quite a few months experience with this set up and charge discharge cycle.

Hope this helps.

[Kibo]

Well I guess I jinxed myself !

Just days after my last post my house batteries died on me. Wouldn't take a full charge and discharged really quickly. So I upgraded to 2 x 12v big boys of 285 AmpHours each....

Haven't been through a discharge/charge cycle yet since I am in a marina for a few days but my Victron monitor tells me that they should last over 36 hours with a 9amp draw so we will see what I get in the real world....

[tiger79]

Well I guess I jinxed myself !

Just days after my last post my house batteries died on me. Wouldn't take a full charge and discharged really quickly. So I upgraded to 2 x 12v big boys of 285 AmpHours each....

Haven't been through a discharge/charge cycle yet since I am in a marina for a few days but my Victron monitor tells me that they should last over 36 hours with a 9amp draw so we will see what I get in the real world....

If you want your new batteries to last a reasonable time, you should avoid discharging them by more than about 45-50%, so at 9A you're looking at about 30 hours max.

[Kibo]

Thanks Tiger. The Victron says zero hours remains at 50% discharge so that is what I refer to. If I can get 24 hours between charges I am happy

[tiger79]

Thanks Tiger. The Victron says zero hours remains at 50% discharge so that is what I refer to. If I can get 24 hours between charges I am happy

You mentioned though that your Victron monitor suggested you would have "over 36 hours with a 9amp draw", which is over 324Ah.  So perhaps you need to check that your monitor is correctly adjusted for the 570Ah total capacity.

[Kibo]

Good point Tiger. I will check it once I am in discharge mode. Still on shore power right now so it may not be as accurate with a very "hot" battery since I simply turned shore power off and checked the monitor quickly.  I will see what it does after a few cycles and adjust as needed.   Thanks again for the advice.

[Kibo]

Update: after a few days cycling the Victron is pretty accurate. With 100% charge it indicates 25-27 hours under the average (net) load of around 9-9.5 amps. That is pretty accurate timing on the actual cycling down to 50% from 100%.