Realistic expectations for my house batteries - Page 14 - SailNet Community
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post #131 of 138 Old 04-22-2019
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Re: Realistic expectations for my house batteries

Handling lead batteries is something you shouldn't have to do much. Last time I had time I had to do it I paid the yard guy to lift them from the cabin sole up to the berth and place them in their compartment. The rest I was able to do with a halyard and a winch. Having said that.. I suppose smaller and lighter makes more sense. But geometry rules and not all batts will work for the designated space/volume. My compartment is 20.25" x 24.5". I could make the 20.25" a few inches larger but I have to move my heater. 2 8Ds fit nicely and the AGM start batt lives close by.

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post #132 of 138 Old 04-23-2019
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Re: Realistic expectations for my house batteries

Pricing of quality bare LFP cells likely will not fall, demand in fact is rising faster than supply can expand.

Protective gear with BMS functionality will fall, ideally open hardware designs, open source firmware, compatible with a range of cells brands and sizes, and user-configurable setpoints.

Which will force packaged-system vendors to be more competitive unless they just want to "skim the cream" at the top end.
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post #133 of 138 Old 04-23-2019
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Re: Realistic expectations for my house batteries

@Maine Sail write up is amazingly detailed. I'm only about half way through, but have learned a ton already. For starters, I did not realize there were amperage discharge limitations in many pre-packaged LFP batteries, as low as 50 amps. I was thinking about the ReLioN brand, so I looked it up. They have a 100amp discharge. I need to understand this more.

Hopefully, I have many more years before needing to replace my Gels again. Maybe enough time to build my own system. My batts were new last year. However, I doubt I'll wait until the are in desperate need. My bank is simply too small at 400ah.

When folks say their LA banks last 8-10 years, I bet they simply have so much capacity, they can't really tell they've lost a bunch of it. I got 8 years out of a Gel bank, which was still working fine, it just had notably lower capacity.
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post #134 of 138 Old 04-23-2019
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Re: Realistic expectations for my house batteries

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Originally Posted by Minnewaska View Post
@Maine Sail write up is amazingly detailed. I'm only about half way through, but have learned a ton already. For starters, I did not realize there were amperage discharge limitations in many pre-packaged LFP batteries, as low as 50 amps. I was thinking about the ReLioN brand, so I looked it up. They have a 100amp discharge. I need to understand this more.

Hopefully, I have many more years before needing to replace my Gels again. Maybe enough time to build my own system. My batts were new last year. However, I doubt I'll wait until the are in desperate need. My bank is simply too small at 400ah.

When folks say their LA banks last 8-10 years, I bet they simply have so much capacity, they can't really tell they've lost a bunch of it. I got 8 years out of a Gel bank, which was still working fine, it just had notably lower capacity.
I suspect cycling the batteries shortens their service life. If true it makes sense to set up a large amp capacity and not draw it down too much keeping it topped up with a high output alternator and alternate charging sources. I also think (guess) that keeping batt temps lower then higher improves their service life. I could be wrong about this and I would like read what others think of this approach.

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post #135 of 138 Old 04-23-2019
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Re: Realistic expectations for my house batteries

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I suspect cycling the batteries shortens their service life. If true it makes sense to set up a large amp capacity and not draw it down too much keeping it topped up with a high output alternator and alternate charging sources. I also think (guess) that keeping batt temps lower then higher improves their service life. I could be wrong about this and I would like read what others think of this approach.
The deeper you discharge the battery the more you reduce the number of charge cycles available. It's why I tend to switch to Electro-sailing mode when I see my EP bank has dropped to 75% from the initial 100% full charge. I never wait until it has dropped to 50% which is often quoted as acceptable for lead acid. Specs for my 8A4D batteries say that discharging by 25% results in over 1000 cycles while discharging to 50% reduces that to 500 cycles.

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Last edited by mbianka; 04-23-2019 at 10:14 AM.
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post #136 of 138 Old 04-23-2019
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Re: Realistic expectations for my house batteries

Yes informal anecdotes about battery life rarely include the %SoH data when replacement EoL was determined.

Many if not most just keep running until failure.

But there are top-notch FLA banks that safely get 13 even 15 years, but they weren't picked up at big box retail.
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post #137 of 138 Old 04-25-2019
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Re: Realistic expectations for my house batteries

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Originally Posted by Minnewaska View Post
... For starters, I did not realize there were amperage discharge limitations in many pre-packaged LFP batteries, as low as 50 amps. I was thinking about the ReLioN brand, so I looked it up. They have a 100amp discharge.
Likewise I'm researching and learning about LFP batteries. Honestly I'm a hard-sell because am a big believer in 2V industrial FLA, but trying to be open.

I'm having discussions with a manufacturer in China. They quote 2000 cycles at 100% discharge, per their factory testing. They will build a bank to your specs and requirements. So this is what they've come back to me asking (which coincides with what Minnewaska says above):

"About the LiFePO4 battery packs you requirements of 12V 1000ah , we would like to know more:
1, Do you have request to dimensions?
1, Could you please tell us the application to use?
3, Do you have request to max. discharge current and charge curret? So we can make right BMS protection system for you.

Only knowing all your specific, so we can make right solution for you and quote the best price for you.

Lithium battery can be customized form your request, we can follow your request to design, including dimension, max. discharge current and charge current,"
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post #138 of 138 Old 04-25-2019
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Re: Realistic expectations for my house batteries

High on my list of expectations is that they be maintenance free. This means I don't have to add water and possibly deal with leaking batter acid if I used sealed batteries. Using sealed batteries means you don't need a traditional batter box and the batts can be placed in any orientation where you can fit them. Of course you will want to limit long wire runs.

Batteries of all types seem to be happiest and life longer when the are not deeply discharged before recharging. Therefore you want to limit the amount of amps you draw and add alt charging sources which prevent (hopefully) deep discharging. If you have a deep discharge you'll want a high amp charging device such as a smart regulated high output alternator.

So the approach involves... controlling and limiting your amp draw.... having alt charging sources to be replenishing used amps and a high output source for charging quickly when needed.

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