Jump to content

Battery bank size verses charging capacity


Recommended Posts

Booboo, not sure if you have a Yanmar or a Volvo, but a couple of thoughts assuming you have a Yanmar and for now you decide not to install a second alternator.

This outfit in the US makes a drop in 94 amp output alternator for Yanmars that can be controlled by an external regulator.

http://www.zrd.com/pd/esdalternators.html

I would then suggest directing the output from the alternator straight to the house bank (ie not via the starter motor positive stud as it most liekly is now), with the regulator sense wire taken from the house bank,

then installing one of these to charge the engine battery

http://www.balmar.net/products/digital-duo-charge/

I have one of these on my yacht and Works just fine.

Link to post
Share on other sites

Just a note for anyone interested. If you want to test a deep cycle battery yourself, you can make a fairly usefull test rig like this - Battery to inverter, mains powered clock, and load by light bulbs. Use higher wattage bulbs and or more/less to get the load you want, leave it on, and the clock will stop when the battery gets flat. So then a simple calc tells you capacity - time in hours x amps = amp hours. Its not perfect, but it will give you a pretty accurate capacity for a given battery...

 

Battery Tester.JPG

Link to post
Share on other sites

Josh another thing to check that had me going when we first got our boat in the Med was the digital readout on the instruments wasn't  calibrated

We thought the batteries were flat every morning  but when I checked them at the battery terminals they were reading 12.4 but the instruments were saying 11.9 or something like this

I reset this and then found out everything was OK, the previous owner had put in a new charger and had bought a load tester all because the readout was wrong

also check that the power into the instrument computer is the same as the batteries as a dirty connection will also give a incorrect reading.

If the batteries are original or over 5 or 6 years then your doing the right thing considering the length of trip your undertaking

Another thing is you can possibly make more changes in the Caribbean if you still haven't sorted things by then, It will be cheaper there as you will be paying in USD plus the Med is a lot more expensive in general we found.

Link to post
Share on other sites

Hi Jon, yes our readout on the panel is always about 0.5v under what out victron battery monitor reads. I have checked the victron monitor against an actual multimeter on the batteries and it is right. I don't know how to reset the panel readout but really don't even look at it anyway.

Batteries going in the boat tomorrow along with a new forestay then we can get out cruising!

What's your total battery capacity Jon and a typical daily draw for you when at sea? I can't remember if you had solar power?

I just replaced all the nav lights bulbs with LED so instead of a 3amp draw it's now down to about 0.5. Much happier but $$$ bleeding again at 45euro each....

Link to post
Share on other sites

Good call on the batteries, just get on with it and go sailing.

Jon is right though the Caribbean is well priced for marine electrical stuff.

We swapped our 880 amp hour bank in Grenada through Budget Marine at very good pricing.

If you are buying a bit their listed prices are negotiable.

http://www.budgetmarine.com/Catalog/Electrical/Chapter.aspx

 

For the meter calibration with our BEP you have to guess an efficiency figure and see if the amp hours remaining numbers work out.

Not a lot of science as I saw it but I think 95% was where we ended up.

This is to account for heat losses I guess, charging and out through the invertor.

Link to post
Share on other sites

Josh, we have 5 house batteries

Can't remember exactly but either 180 or 220 amp hours each

We now have two 150 w solar panels, but only added them here, we can run the boat on a mooring off the solar but our main baulk charging comes the 170amp alt on the main engine or if we are sailing we use the genset and have a 80amp mains charger connected

The genset only uses 1 ltr per hour and we would run it for two to three hours a day

We don't have a battery monitor thing, I've never really had much faith in them personally, preferred to just keep an eye on the volts

I'd say we use between 10 to 29 amps to run the boat at sea, but we have two fridges and a freezer so one more than you

Link to post
Share on other sites

Checking to make sure there are no parasitic loads on the house bank is always a good move if your finding they are not lasting as long as they should. Sometimes a few owner installed devices may have bypassed the shunt for the battery monitor. If one of those has a constant draw ( either due to failure or simply thats how it operates but you cant easily measure it ) then you will get erroneous readings on your battery monitor.

 

Another thing I have found to be a useful method of maintaining your batteries is to do a big charge early morning, get those batteries up to the absorption state ( 80-100% which is the slow charge phase ) with your alternator/genset and then let the solar do the absorption stage ( which is around 14.2 volts for Lifelines ) upwards to whatever the max voltage the battery is specified for ) as its time consuming but only requires a low current ( although this could easily be 20 amps with a bank the size of yours, plus any loads you have on top ). This will naturally lead to the float stage where the panels and or any other generation source will operate the loads without any drain on the battery - leaving it fully charged.

 

Another thing to consider is what voltages are you actually getting to? What voltage are you seeing on the bank when you consider it to be "flat", "charged" etc? Are they sensible voltages? Flat is not 10 volts - its 12.2 to be maintaining the State of charge above 50% ( which is what you should never go below. Lifeline consider 11.6 volt to be dead flat. You need to test with no current flow - no charging at all and no draw off at all, rested for at least 30 minutes. You can do this yourself easily.

Link to post
Share on other sites

 

We don't have a battery monitor thing, I've never really had much faith in them personally, preferred to just keep an eye on the volts

 

A good monitor is far more reliable than going simply by Voltage. Volt meters can have calibration issues. But most importantly, if you do not get your batteries into Float mode, you are slowly Killing them. And replacing 1000Ahrs every 5 yrs is more than my pocket could handle.

 

 

I'd say we use between 10 to 29 amps to run the boat at sea, but we have two fridges and a freezer so one more than you

Do you mean 100 to 290

Link to post
Share on other sites

 

Flat is not 10 volts - its 12.2 to be maintaining the State of charge above 50% ( which is what you should never go below. Lifeline consider 11.6 volt to be dead flat.

Correct TT. 

Bbut if the battery is under load, the voltage will actually read 10.5V and will, or should lift back to a rest voltage of 12V when the load is removed. This is why Inverters have a cut off at 10.5V. If the rest Voltage is 10V, then the battery life expectancy will be greatly reduced.

Link to post
Share on other sites

A good monitor is far more reliable than going simply by Voltage. Volt meters can have calibration issues. But most importantly, if you do not get your batteries into Float mode, you are slowly Killing them. And replacing 1000Ahrs every 5 yrs is more than my pocket could handle.

 

Do you mean 100 to 290

Absolutely agree Wheels, with the monitor. You can't tell state of charge at all when a battery is in use with volts alone. And resting a battery properly (10 Hours) before reading a voltage is not practical.

 

I read the consumption part as he's using 10-29 amps when at sea with everything running, but thats a LOT of load - if its a 15 amp average that's 360 amp/hours per day, so allowing losses, say 400 amp hours to replace....

 

I'd just like to reiterate - batteries don't often die - they are killed!! Under charging is the most common way. 

Link to post
Share on other sites

I don't have a motor sailor like you lot but do drop a Weaco CF40 into my little family cruiser now and again. We have found when it is pulling everything down to temp she is a thirsty wee beast. Once there she is very economical, nearly 1amp as long as it stays out of the sun and the kids don't open it every 20 seconds.

 

I did try turning it off and on but found what IT suggests, it used more doing that then leaving it on full time. We tend to load it at home/on the marina while connected to mains then drop it into the boat when down to temp and just leave it on.

 

The CF range are the compressor range, not the thermo electric...which are wickedly thirsty in the am dept.

Same,but we drop in everything almost frozen,set on green light 3,turn off at 10.00pm turn on at 6.30am runs 5 mins and all is good,forget about those electrix?? chew power 2 dvds a night,house battery sad now 3yrs on.

Link to post
Share on other sites

Typing on a ph so big fingers and small numbers

9 should have been 0

So load very rarely drops below 10 amps but I've seen it in the high teens when AP is working hard

The original batteries lasted 8 years so not all bad considering the use they had

Euro boats do have a much higher load than kiwi boats but then you have more boat as well

Typical day at sea we run genset for 1 to 1 1/2 hours to make breakfast and fill water tank

Then will run it again in the evening, that gives us over 200amos in the bank so slightly running in deficit , when the wind is light we will use the main engine at 1500rpm this is putting in 150 amps every hour so 6 hours of motor sailing tops everything right up

Link to post
Share on other sites

It really pays to trim to keep your autopilot happy as they suck heaps when they aren't.

With our Coursemaster adjusting the sea state setting would also help it a lot.

We also had one of those little Raymarine rubber ban drive wheel pilots.

It had no chance when we were powered up but used a lot less amps in the light.

Link to post
Share on other sites

Ok next question, how much should I be expecting my 450 watt of solar panels to be putting in. It seems to be only around 8-12 amp at the moment and that's with batteries at 85%. I feel like I should be getting a bit more?

Was getting 105 amps out of the alternator this morning so that's good. Means I don't really need to upgrade that.

Link to post
Share on other sites

On the 44.7 we had 2 banks of solar panels, a pair of new 100w and a pair of 6 year old 60w.  So a total of 320w, although the 60w ones may not have been outputting the full 60w being old.

 

From both banks total we were typically seeing 10-15amps if the panels were in good sunlight.  Hit 20ish amps in perfect conditions now and then.

 

So without going scientific and actually working it out, 450w should create about half as much again so I'd expect 20amps normally and peaks a bit above?

Link to post
Share on other sites

Depending on how they are wired you could use the clamp meter to check all the panels are working.

After a lightning side swipe in Panama one of ours had melted the printed circuit where it joined the output wire.

Pretty delicate soldering job but we got it going again.

Link to post
Share on other sites

If they're wired in parallel then you can check the output on a sunny day by covering them with towels and uncovering one at a time and checking what you're getting.  If wired in series I don't think this will work though.

Link to post
Share on other sites

Bit of a tricky one Booboo. If everything was perfect, the max that 450W can put into a 12V bank charging at 13.8V is about 32A. That would require the panels to be directly facing the Sun, Sun to be high in the Sky of Mid Summer, Sky to be very clear, no shadows cast on the Panel in anyway and the Panel surfaces to be clean. This time of the year in the Northern Hem, I would expect a fall off in power and the sky not being so clear up there can also drop the current. Plus not being able to face the panels directly at the Sun could drop the output dramatically. How much is a bit of a guess, but it could be by half.
The next question and it's an important one, what is the Charge reg? Is it MPPT or just a plain jane PWM? That can make a huge difference.
It is also a good idea to connect the panels in Series, especially with MPPT regs. This raises the Voltage and thus less loss in the wiring and you get the reg switching on earlier and off later. Although the current is not a lot at those extremes, it is still something. 
 

Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.


×
×
  • Create New...