Re: [electricboats] Recommendation for Charging 12v House Battery from 48v Bank

I use a Victron 75/15 Smart MPPT controller to charge a 12v LiFePO4 domestic service bank. Works well for me.

On Fri, 26 Jan 2024, 02:56 , <kurtphone@gmail.com> wrote:

I use a Victron mppt smart solar controller from the 48V main bank to the 12V house bank. It's smart, switchable and has a configurable charge profile with bluetooth control and monitoring. 

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Re: [electricboats] Recommendation for Charging 12v House Battery from 48v Bank

I agree with Kurt's suggestion: a MPPT charger will be a good option. I am using EPEver mppt chargers to keep my 12Vdc and 24Vdc battery banks charged from my 96Vdc main energy storage bank. This has been working great for close to 2 years now.

The only issue with most MPPT chargers: if you were to disconnect the 12Vdc battery and keep the 48Vdc connected, most MPPT chargers would be destroyed, as they do not have protection for this situation. I have killed one of my chargers due to that already.

Jerome

On Thu, Jan 25, 2024 at 2:56 PM <kurtphone@gmail.com> wrote:

I use a Victron mppt smart solar controller from the 48V main bank to the 12V house bank. It's smart, switchable and has a configurable charge profile with bluetooth control and monitoring. 

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Re: [electricboats] Recommendation for Charging 12v House Battery from 48v Bank

I also use a dc-dc charger. It provides a  steady 13.4 volts to the house battery, which is good and guarantees  that there is always a reliable  12volt supply. What it doesn't  do is provide the occasional bulk and absorption  charge the battery needs from time to time. I believe  there are DC-DC generators that can provide  this as well 

On Thu, Jan 25, 2024, 1:18 p.m. Reuben Trane via groups.io <rjtrane=me.com@groups.io> wrote:

I have a 48v battery charged from solar and a 12v AGM battery in the bow for windlass and local 12v needs. I use a DC/DC charger. Works perfectly. If interested I can get you brand and info. 

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Re: [electricboats] Recommendation for Charging 12v House Battery from 48v Bank

I have a 48v battery charged from solar and a 12v AGM battery in the bow for windlass and local 12v needs. I use a DC/DC charger. Works perfectly. If interested I can get you brand and info. 

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Re: [electricboats] Recommendation for Charging 12v House Battery from 48v Bank

I use a Victron mppt smart solar controller from the 48V main bank to the 12V house bank. It’s smart, switchable and has a configurable charge profile with bluetooth control and monitoring. 

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Re: [electricboats] Recommendation for Charging 12v House Battery from 48v Bank

I have a 48V battery bank and a 12V house.  Been running this setup for 4 years now and no issues.

I use an MPPT (Victron SmartSolar 100/20).  Connect your 48V battery to the MPPT PV input.  The MPPT sees your 48V or 52V bank as solar and it outputs proper charging voltage for your battery type.  You can set charge voltages, and all the charging parameters.  MPPT's are designed to do exactly that, so much better than a converter.  Chances are you already have a Victron unit for your solar arrays, if so you can use the same Victron Connect app to read the house battery unit as well.

Additional tip.  I charge the 48V bank at the dock (shore power) as well as solar when cruising (using another  MPPT).  To prevent our 12V loads discharging our 48V bank when at sea or dock and end up without a motor, we use a switch to the victron unit remote connector.  This is not very well documented or understood, but the VE. Direct connector can be used to turn the unit on or off without requiring the VE.Direct cable or unit.  Connect Pin 2 to GND will switch the MPPT charger off.  Switch that connection to open and the unit starts charging.

Keep in mind that the 48V whether connected through a DC-DC or MPPT, the 12V battery is being maintained all the time from your 48V hence draining your 48V bank, unless you have a 12V disconnect or a charger disconnect.  

In my case, at the dock, a relay opens when we have shore power, and allows the MPPT to charge the house battery.  When shore power is removed (when at sea), the relay closes and the MPPT for our 2V house is off.  We use minimal 12v loads and monitor the house battery level.  I also installed a bypass switch that I can manually through open if needed (after confirming sufficient reserve in the 48V bank).  So at sea, if the 12V is starting to get low, we flip the switch and the MPPT starts charging our house battery from our 48V.  Very nice and peace of mind, no worries about the house loads draining our 48V bank while sleeping, anchor light staying on, etc..

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Re: [electricboats] Recommendation for Charging 12v House Battery from 48v Bank

I had the same issue. I have a 48 to 12v converter, but they say not to use it for battery charging. So I ran a 50w solar panel for that one battery. I am researching if I can put 48v into the solar controller to charge the house battery. I hate to fry a controller just to test it. So, im thinking I'll connect the battery and the 48-12 converter to the house circuitry and since it only puts out 12v, the solar panel will top off the battery to 14 volts.

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