Hi Seebreezy,
Some time ago I developed a spreadsheet to calculate battery charge/discharge status under various real world scenarios.
This readily answers your question.
Unfortunately, one can't upload spreadsheet files to this forum, but pm me if you'd like a copy.
Meantime, here's a pic with values I have plugged in to explore battery charge/discharge status on my boat.
regards,
allan

Ramona said..

Seebreasy73 said..
I've got 4x deep cycle batteries with over 300 amp hour storage and I think it is a bit of an overkill. In theory I could draw 10 amps continuously for 30 hours. In a week's use being on the boat, without charge the batteries drop down to 80% from a full charge.

I recon, I could do with only 2x. And they are old fashioned led batteries needing maintenance at least once a month and are not sealed to my liking. But they work and are relatively new. I would think sealed or AGM batteries would have been a better choice.

How much amperage is enough?

It depends on how you are charging these batteries. Personally I would not buy any battery for my boat that I could not top up the levels. If nothing else you have to manually inspect them every month or so. Otherwise you tend to forget and do nothing till there is a problem.

charging either by motoring but mainly from the berth. I am planning to add some solar panels in the near future, so charging at the moment is not an issue.

Strangely enough Ramona that's why I went to AGM because I didn't check the water and ruined my old one. No gas, no chance of spilling acid, faster recharge capacity and no idiot forgetting to do the maintaince

Datawiz said..
Hi Seebreezy,
Some time ago I developed a spreadsheet to calculate battery charge/discharge status under various real world scenarios.
This readily answers your question.
Unfortunately, one can't upload spreadsheet files to this forum, but pm me if you'd like a copy.
Meantime, here's a pic with values I have plugged in to explore battery charge/discharge status on my boat.
regards,
allan

Cool spreadsheet Datawiz!

Seabreezy, I run 400AH as a house bank, and I don't believe that is excessive by any means. This is an upgrade from the specified 200A standard, when I added the hot water boiler I thought I needed a topup.

When we're racing, we'll need to run the diesel for an hour to recharge every 24 hour period even for this bank. I'll be hovering at 12V in a day, guaranteed. Below 12V and equipment will start to get squirrely.
Racing trim means the PC is on, fridge is on, instruments and gps and ais, nav lights, water pressure (hot water is from diesel heating though, the boiler is always off.)
The electric winch is off , as it's only used to get the mainsail up, after that it is used as a normal winch. The windlass is not used when racing of course.

When we're cruising/anchored up, I'll have a big chunk of all this stuff shut down, and then I can last a few days with just the radio and fridge only. If Im off the boat, only the fridge stays on and this will last 7 days before batteries are too drained.

One of the biggest hidden killers to my power budget is the crew all needing their mobile phones, doodads and ipads charged. This took a bit of a dint out of my calculations, as I never even thought about it.There is always at least 2 devices being charged, and it happens every day.

So, I dunno mate, if you're heading offshore even local, 300Ah is noway near an overkill, well for me at least!

shaggybaxter said..

Datawiz said..
Hi Seebreezy,
Some time ago I developed a spreadsheet to calculate battery charge/discharge status under various real world scenarios.
This readily answers your question.
Unfortunately, one can't upload spreadsheet files to this forum, but pm me if you'd like a copy.
Meantime, here's a pic with values I have plugged in to explore battery charge/discharge status on my boat.
regards,
allan

Cool spreadsheet Datawiz!

Seabreezy, I run 400AH as a house bank, and I don't believe that is excessive by any means. This is an upgrade from the specified 200A standard, when I added the hot water boiler I thought I needed a topup.

When we're racing, we'll need to run the diesel for an hour to recharge every 24 hour period even for this bank. I'll be hovering at 12V in a day, guaranteed. Below 12V and equipment will start to get squirrely.
Racing trim means the PC is on, fridge is on, instruments and gps and ais, nav lights, water pressure (hot water is from diesel heating though, the boiler is always off.)
The electric winch is off , as it's only used to get the mainsail up, after that it is used as a normal winch. The windlass is not used when racing of course.

When we're cruising/anchored up, I'll have a big chunk of all this stuff shut down, and then I can last a few days with just the radio and fridge only. If Im off the boat, only the fridge stays on and this will last 7 days before batteries are too drained.

One of the biggest hidden killers to my power budget is the crew all needing their mobile phones, doodads and ipads charged. This took a bit of a dint out of my calculations, as I never even thought about it.There is always at least 2 devices being charged, and it happens every day.

So, I dunno mate, if you're heading offshore even local, 300Ah is noway near an overkill, well for me at least!

Shaggy, I'm suprised to see that charging devices gives you grief, do have usb charging outlets or charge through a 240v inverter ?

woko said..

shaggybaxter said..

Datawiz said..
Hi Seebreezy,
Some time ago I developed a spreadsheet to calculate battery charge/discharge status under various real world scenarios.
This readily answers your question.
Unfortunately, one can't upload spreadsheet files to this forum, but pm me if you'd like a copy.
Meantime, here's a pic with values I have plugged in to explore battery charge/discharge status on my boat.
regards,
allan

Cool spreadsheet Datawiz!

Seabreezy, I run 400AH as a house bank, and I don't believe that is excessive by any means. This is an upgrade from the specified 200A standard, when I added the hot water boiler I thought I needed a topup.

When we're racing, we'll need to run the diesel for an hour to recharge every 24 hour period even for this bank. I'll be hovering at 12V in a day, guaranteed. Below 12V and equipment will start to get squirrely.
Racing trim means the PC is on, fridge is on, instruments and gps and ais, nav lights, water pressure (hot water is from diesel heating though, the boiler is always off.)
The electric winch is off , as it's only used to get the mainsail up, after that it is used as a normal winch. The windlass is not used when racing of course.

When we're cruising/anchored up, I'll have a big chunk of all this stuff shut down, and then I can last a few days with just the radio and fridge only. If Im off the boat, only the fridge stays on and this will last 7 days before batteries are too drained.

One of the biggest hidden killers to my power budget is the crew all needing their mobile phones, doodads and ipads charged. This took a bit of a dint out of my calculations, as I never even thought about it.There is always at least 2 devices being charged, and it happens every day.

So, I dunno mate, if you're heading offshore even local, 300Ah is noway near an overkill, well for me at least!

Shaggy, I'm suprised to see that charging devices gives you grief, do have usb charging outlets or charge through a 240v inverter ?

G'day Woko,
I wouldn't say its a big problem, but I do notice the difference. No 240V, I use the normal 12V -5V cigarette lighter adaptors, admittedly high charging rate ones. The IPads are the worst, when they're running wireless they seem to be always need to be on charge, phones are only bad when they're offhshore and constanly draining looking for weak signal. I just ordered a Telstra repeater that should help with this issue at least. The little lithium battery packs everyone seems to carry annoy me, they draw a lot. Charge 'em at home.

Marekkn said..

Datawiz said..
Hi Seebreezy,
Some time ago I developed a spreadsheet to calculate battery charge/discharge status under various real world scenarios.
This readily answers your question.
Unfortunately, one can't upload spreadsheet files to this forum, but pm me if you'd like a copy.
Meantime, here's a pic with values I have plugged in to explore battery charge/discharge status on my boat.
regards,
allan

Is your alternator only charge 5Amps ? isn't that AFTER all devices would get it's power from alternator? Even if you have 10ah draw you should end up with more charge after 10 hours motoring (alternators should do something around 15-20Amps ?)

Hi Marekkn,
You are, of course, correct.
The Average Charge Rate shown on the sample shown does not necessarily reflect any particular charging system - the picture is intended as an example only.
regards,
allan

How do you find the amperage rate? Would you simply put a multimeter on the battery terminals and turn everything on one at time?

Toph said..
How do you find the amperage rate? Would you simply put a multimeter on the battery terminals and turn everything on one at time?

Get yourself a good quality battery monitor. Easy to install, very worthwhile.

www.victronenergy.com/battery-monitors/bmv-700

The Zatara crew just installed a neat system:



www.simarine.net/

Toph said..
How do you find the amperage rate? Would you simply put a multimeter on the battery terminals and turn everything on one at time?

You have to put the multimetre between the load & the battery - disconnect the negative battery lead & put the multimetre between the battery & the disconnected lead.
Then turn any loads (fridge, lights, phone charger etc) on to get a reading.

I googled how to do it a while back.

I have 780 Ahs of AGM batteries & run my fridge, freezer, Pi3 24/7. My 550W of solar panels through a 60A MPPT controller keep them fully charged.

I just bought a Victron Battery Monitor BMV-700 to upgrade my monitoring - thanks for the link FreeRadical :)

Ramona said..

Seebreasy73 said..


charging either by motoring but mainly from the berth. I am planning to add some solar panels in the near future, so charging at the moment is not an issue.

Charging 4 batteries of any sort with an automotive type alternator is going to take a hell of a lot of motoring!

i never let it dischage below 80% so it takes 1 - 2 hours to recharge to full.

Jode5 said..

Most multi meters will not take much direct load through them. You will blow up your multi meter. You really need to install a shunt and run a amp meter off the shunt.

or use a clamp meter...

we have 3 x 200 ah lithium for house and 1 x optima for starter battery, 780 watts of solar running through tristar 45Mppt regulator, everything draws from house bank ( anchor windlass, lights , auto pilot fridges / freezers, microwave etc ) only ever had 1 issue ,when we replaced the stand up 12 volt fridge it constantly ran drawing 6-8amps 24 hrs / day just would not stop,( so from 16:00hrs to 08:00hrs close to 130ah consumed just by the fridge) thought it was a lemon, turned it off for 4-5 weeks and then back on and presto , works like it suppose to with normal cycling.