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LiFePO Shore Power Supply Setup


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I'm looking for an AC-DC power supply for use with a LiFePO battery bank I'm building for the boat. I've found a couple Kepco lab supplies that'll do the job but they seem very expensive for the application.

General setup is inspired by Stan Honey: http://honeynav.com/category/lfp-battery-sailing-marine-electrical/

The goal is to have the power supply do double duty:

1) Power DC loads (Max ~20A Intermittent, 10A continuous) while the boat is connected to shore power with the Battery disconnected.

2) Charge the Lithium Bank at 20-40 Amps at a fixed bulk voltage when manually connected and/or connected via relay controlled by battery monitor.

Reason for this setup is to allow the lithium bank to sit at partial (30-70%) state of charge when shore power is available. Schematic attached for those who are curious.

Mariah1 LiFePO Schematic.pdf

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An Iota would do that for pretty cheap: https://www.iotaengineering.com/products/dls-power-converters-battery-chargers#t=ablProducts&sort=relevancy&layout=card&numberOfResults=50

But why?  Just leave the lithium bank in service and set the battery charger to 13.2V (assuming 12V boat - adjust accordingly for higher voltage).  This will draw your batteries down to ~50% and keep them there permanently while they operate the DC systems.

If you have solar, then set the controller the same way and let solar do the work instead of the charger.

We do this all the time.

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General consensus seems to indicate it's best not to float LiFePO and I would rather not run the fridge and other small house loads on the battery and cycle it from 70-30% while I'm away from the boat during the week. 

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1 hour ago, climenuts said:

General consensus seems to indicate it's best not to float LiFePO and I would rather not run the fridge and other small house loads on the battery and cycle it from 70-30% while I'm away from the boat during the week. 

You can float them, you just don't want to float them at high SOC. I float mine at 13.25V, corresponding to 60-70% SOC with no harm done. When I get to the boat, the first thing I do is kick off a bulk charge and by the time I'm ready to go they're topped up. 

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“Battle Born” and the like assure us that their products can simply be “dropped in.”  But I have been somewhat disappointed with the results.  I think what is going on is that the (existing) cheap shore power charger arbitrarily shuts off the “bulk” phase too soon and the LiFePO’s never get charged more than about 80%.  A very cheap way to achieve the same result!  Except there’s no way to get to 100% SOC via shore power. Unless I’m wrong and it’s something else.  

And as far as I can discern, the Victron battery monitor arbitrarily resets to “100%” whenever the bulk charging stops, regardless of how many coulombs went in.  Which confuses things.  I.e. the batteries go into low voltage shut-down when the Victron reads around “40% SOC.”  

I guess I had better get around to finishing my solar installation.  Actually a bit embarrassed to install the “tower of power” while the boat is sitting in the marina.  

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I'm mainly doing this replacement for the weight savings and rarely need more than 30% SOC for a weekend in the summer and 50% SOC in the winter so cycling between 30-80% is fine with me. If I know I'll be sitting somewhere for 3+ days I don't mind a bit of tinkering with the alternator controller or shore power app to get it to 95% or so. It's highly unlikely that I'll charge beyond 95% for anything other than top balancing.

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