Battery Bank Sizes on Sail Boats

[kungfoo]

Originally Posted by tedsherrin

I want maintenance free batteries and whether I get AGM or Maintance free wet cell,the prices are very similar. Exide 120AH I've been quote $285 each. A wet cell is $245. So I don't think they are that expensive.

As for life cycles and partial charging, well seems there is a lot of debate about that and if I make sure I have the means to keep them charged, e.g upgrading my solar for when it's on mooring and with my 90amp alternator for when I'm cuising, then a 480 AH bank should keep up.

Nigel calder has a good discussion of various battery chemistries in the bible. gel-cells, for example, take *very* unkindly to over-charging.

AGMs are in a similar boat, but are a bit more forgiving, as the water in the adjacent paste can migrate to that spot, whereas a gel-cell will turn into white powder, and remain so. wet-cells are, obviously, bullet-proof, but not maintenance-free. You also run into trouble if they can be turned upside down and the acid is free to mix with the salt water producing chlorine gas. AGMs can also accept charge a bit faster than gel-cells, and can handle (I think) a slightly higher voltage. AGMs are also less susceptible to the buildup of sulfate crystals). All-in-all, I decided that AGMs worked best for my use-case.

A good friend of mine who takes absurdly good care of his boat, and is one of the most meticulous people I know, uses wet-cells. A properly-maintained wet-cell (ie proper water/charge, occasional reconditioning, and management of any precipitated sulfate crystals) is bullet-proof, reliable, and long-lived -- it's just easy to screw things up.

HTH,
Harrison

[Terra Nova]

Originally Posted by tedsherrin

...30' boat200Ah house bank35' boat300Ah house bank40' boat400Ah house bank45' boat500Ah house bank50' boat600Ah house bank

House banks should be sized based on electrical usage, not boat length.

Originally Posted by tedsherrin

...I can go for four 120 AH AGM batteries with the separate 120 wet cell for a reserve...

Don't mix battery types.

[Rustic Charm]

Originally Posted by kungfoo

Nigel calder has a good discussion of various battery chemistries in the bible. gel-cells, for example, take *very* unkindly to over-charging.

AGMs are in a similar boat, but are a bit more forgiving, as the water in the adjacent paste can migrate to that spot, whereas a gel-cell will turn into white powder, and remain so. wet-cells are, obviously, bullet-proof, but not maintenance-free. You also run into trouble if they can be turned upside down and the acid is free to mix with the salt water producing chlorine gas. AGMs can also accept charge a bit faster than gel-cells, and can handle (I think) a slightly higher voltage. AGMs are also less susceptible to the buildup of sulfate crystals). All-in-all, I decided that AGMs worked best for my use-case.

A good friend of mine who takes absurdly good care of his boat, and is one of the most meticulous people I know, uses wet-cells. A properly-maintained wet-cell (ie proper water/charge, occasional reconditioning, and management of any precipitated sulfate crystals) is bullet-proof, reliable, and long-lived -- it's just easy to screw things up.

HTH,
Harrison

Seems a bit of an oxy moron to say on the one hand wet cells are bullet proof but then are high in maintenance and it's easy to screw things up.

I'm not sure about the US, but certaily in Australia cat 3 cruising vessel's are required to have either AGM's, Gel or completely sealed wet cells. Not that I'll ever have a vessel capable of being enrolled in such a race. There are too many other problems I'd have to get over, including that my bilges empty into the cockpit which isn't allowed.

But in the three years, I've had my wet cells (and I don't know how old they are) I've struggled constantly to keep water in them. Could just be that they are physically damaged. But in any case I just don't want the high maintance hassel with them.

[Rustic Charm]

Originally Posted by Terra Nova

House banks should be sized based on electrical usage, not boat length.
Don't mix battery types.

There giving boat length so I can compare to my own 36 footer that's all. I havn't been able to work out my usage completely yet, so knowing the size of their vessels helps a bit.

'Don't mix battery types', why not, if like I said, their not connected in the same bank? The reserve is separate to the AGM House Bank and charged through an ACR. What will be the problem with a separate 'reserve' for an emergency that is not an AGM?

[kungfoo]

Originally Posted by tedsherrin

Seems a bit of an oxy moron to say on the one hand wet cells are bullet proof but then are high in maintenance and it's easy to screw things up.

Of course, I should clarify: wet-cells are easy to screw up (permitting to remain under-charged for too long, for example). That being said, screw-ups can be addressed much more readily. Adding water, chemically dissolving the sulfate crystals, adding a pulse-desulfator, etc.

But in the three years, I've had my wet cells (and I don't know how old they are) I've struggled constantly to keep water in them. Could just be that they are physically damaged. But in any case I just don't want the high maintance hassel with them.

What voltage is your alternator set to? Do you have a proper 3/4 stage charging system for when you're in port? Is that charging system adjusted for the voltage recommendations of your battery manufacturer?

[zboss]

Originally Posted by tedsherrin

But in the three years, I've had my wet cells (and I don't know how old they are) I've struggled constantly to keep water in them. Could just be that they are physically damaged. But in any case I just don't want the high maintance hassel with them.

I bought water miser caps with our new Trojan wet cells last year. As of 310 days operating, I have had to add water 3 times.

Water Miser Battery Vent Caps

We have 520 amp hours but I wish I had double, which gives us 260 usable. However, I wish we had closer to twice that usable. So when the prices come down the next cells will be lithium.

[kungfoo]

Originally Posted by tedsherrin

There giving boat length so I can compare to my own 36 footer that's all. I havn't been able to work out my usage completely yet, so knowing the size of their vessels helps a bit.

'Don't mix battery types', why not, if like I said, their not connected in the same bank? The reserve is separate to the AGM House Bank and charged through an ACR. What will be the problem with a separate 'reserve' for an emergency that is not an AGM?

Different battery chemistries require different voltage-curves for charging. If you over-charge a gel cell or AGM, you lose water that can't be replaced, for example.

[Terra Nova]

It sounds like they are being overcharged.

[Rustic Charm]

Originally Posted by zboss

I bought water miser caps with our new Trojan wet cells last year. As of 310 days operating, I have had to add water 3 times.

Water Miser Battery Vent Caps

We have 520 amp hours but I wish I had double, which gives us 260 usable. However, I wish we had closer to twice that usable. So when the prices come down the next cells will be lithium.

The water miser caps are interesting. I wish i knew about them when I purchased the boat three years ago.

You want over 1000 ah's? How would you charge that much? What are you using in your boat to use that much power?

[Velella99]

I would be very careful to work out an energy budget and then throw in another 20%. The two large drains on batteries are (as one learned person has said above) autopilot and refrigeration. The former's demand can vary hugely depending on sea state and swell. We have a hydraulic system and when it's correcting ahead of a quartering sea the draw is huge and pulls 15 amps for about 5-10 percent of the time and even more of the sea is less swell and more wave. I've pulled the steering system right down from tiller to rudder gudgeon and addressed all sources of friction. In regard to refrigeration, I've been frustrated just how many times my two Engels cycle. I've compared this in other yachts and it's a consistent phenomena. It drives me nuts as we decided to go 'proprietary' to avoid this very issue. The big thing for me however is to understand battery charging better. We have an 80 amp alternator but with long days of sailing we top up batteries using a 2KVA generator. My charging system seems to regulate the AC charger input. I can have the wind generator screaming in 10-15A and as that rises the demand on the AC battery charger reduces. Our analogue radar draws 20A on 'blast' mode and 0.5A on standby and we use it at night only to intermittently track threats. HF is 25+ amps but that's barely used. Inverter is 1500W and purposely rarely used as we've inverted in 12V tools other than the microwave and charging my battery power tools. All lighting has been converted to LED. Oops I've been raving...

[mitiempo]

Originally Posted by Cheechako

Just keep in mind, even if you have a huge battery bank... sooner or later you are going to have to refill all those amps!

Only if you use more AH. For a given usage the charging is the same regardless of how large the bank is. The difference is they will last longer as you are using a smaller percentage of the bank. The other bonus is a larger reserve when needed.

[mitiempo]

Originally Posted by tedsherrin

.... or completely sealed wet cells.

But in the three years, I've had my wet cells (and I don't know how old they are) I've struggled constantly to keep water in them. Could just be that they are physically damaged. But in any case I just don't want the high maintance hassel with them.

If you are adding a large amount of distilled water to your batteries constantly there is something wrong with the charging system. Temperature compensation or just the charging voltage it is an issue. Agm batteries are fussier - if you are not charging them properly they will not survive anywhere near as long as flooded batteries will in the same conditions.

Best to make sure your charging system is matched properly to the battery type you have - including an external regulator for the alternator with temp sensor for the batteries - ideally for the alt as well.

Sealed flooded batteries are the worst choice - they go through liquid as fast as non-sealed flooded batteries, you just are not able to replace them.

Racing rules do not in any way take into account the maintenance or longevity of batteries - they are just to avoid the rare chance of an acid spill.

[Rustic Charm]

Originally Posted by mitiempo

If you are adding a large amount of distilled water to your batteries constantly there is something wrong with the charging system. Temperature compensation or just the charging voltage it is an issue. Agm batteries are fussier - if you are not charging them properly they will not survive anywhere near as long as flooded batteries will in the same conditions.

Best to make sure your charging system is matched properly to the battery type you have - including an external regulator for the alternator with temp sensor for the batteries - ideally for the alt as well.

Sealed flooded batteries are the worst choice - they go through liquid as fast as non-sealed flooded batteries, you just are not able to replace them.

Racing rules do not in any way take into account the maintenance or longevity of batteries - they are just to avoid the rare chance of an acid spill.

I never thought of a regulator for the alternator. I assumed it's own regulator would be sufficient. I presume my Blueseas ACR doesn't 'regulate'?

[mitiempo]

Originally Posted by tedsherrin

I never thought of a regulator for the alternator. I assumed it's own regulator would be sufficient. I presume my Blueseas ACR doesn't 'regulate'?

Blue Seas ACR or any other ACR parallels the batteries - no control over voltage.

[Ex-Calif]

Originally Posted by tedsherrin

I want maintenance free batteries and whether I get AGM or Maintance free wet cell,the prices are very similar. Exide 120AH I've been quote $285 each. A wet cell is $245. So I don't think they are that expensive.

As for life cycles and partial charging, well seems there is a lot of debate about that and if I make sure I have the means to keep them charged, e.g upgrading my solar for when it's on mooring and with my 90amp alternator for when I'm cuising, then a 480 AH bank should keep up.

You've described your uasge of the boat as somewhat weekend warrior, some long weekends and an annunal 4 weeks cruise.

Maintenance free batteries make total sense!

Adjust the charging curve for AGM and drive on!

Originally Posted by kungfoo

Nigel calder has a good discussion of various battery chemistries in the bible. gel-cells, for example, take *very* unkindly to over-charging.

Nigel is correct and Nigel put the latest thinking in the last revision of his book. There is no seciton on LiFoP04 batteries, there are pretty smart chargers these days.

But the world has moved on 10 years.

Originally Posted by kungfoo

Of course, I should clarify: wet-cells are easy to screw up (permitting to remain under-charged for too long, for example). That being said, screw-ups can be addressed much more readily. Adding water, chemically dissolving the sulfate crystals, adding a pulse-desulfator, etc.

If you have time and want to maintain wet cells they are probably best. If you have a life and need maintenance free you get AGM.

Liveabords can turn their batteries into science projects - have at it. Most of us have to do other things.

Originally Posted by kungfoo

What voltage is your alternator set to? Do you have a proper 3/4 stage charging system for when you're in port? Is that charging system adjusted for the voltage recommendations of your battery manufacturer?

Good question but he's always in port. Except when he's not.

Originally Posted by tedsherrin

Seems a bit of an oxy moron to say on the one hand wet cells are bullet proof but then are high in maintenance and it's easy to screw things up.

<snip>

But in the three years, I've had my wet cells (and I don't know how old they are) I've struggled constantly to keep water in them. Could just be that they are physically damaged. But in any case I just don't want the high maintance hassel with them.

Millions(?) of AGMs out there. Tons of flooded wets. can't we all just get along?

Adjust the charge cycle for the battery type and enjoy life.

Originally Posted by kungfoo

Different battery chemistries require different voltage-curves for charging. If you over-charge a gel cell or AGM, you lose water that can't be replaced, for example.

You can screw up any kind of battery if you try hard.

Originally Posted by mitiempo

Only if you use more AH. For a given usage the charging is the same regardless of how large the bank is. The difference is they will last longer as you are using a smaller percentage of the bank. The other bonus is a larger reserve when needed.

This is where I think Ted's got it right - For the type of usage he plans he could go 600-800-1,000 a/h (as we all could) and I am convinced a "shallower" discharge cycle is one of the singular "better" things one can do for their bank.

So big banks dishcarge less for a given a/h budget. But you gotta balance that with how often (calendar) you draw heavily from the batteries.

Ted may deep draw his batts 3-6 long weekends a year and during his 4-week holiday.

This is when he can run the engine some to keep up with the bulk charge phase.

The rest of the time a bigger bank is sitting there doing little work yet getting old in years...