Complicated charging question

[Brownhouse]

on my sailboat I am replacing house batteries with Lifepo4 and leaving lead acid for engine starter. I have three modes of charging, shore power, alternator, and solar. There is a selector switch, I will connect alternator wire to lead acid battery then to a victron dc to dc converter then to selecting switch, I have an mppt controller for the solar. My current shore power charger, very old, has bank 1 and bank 2 wiring. This last component is where I’m looking for help as well as overall design opinions, feels like I may have overlooked something? Thanks for any help.

 

[mopat]

There's a lot missing from your post but could your mppt controller function as your shore power charger?

 

[Brownhouse]

There is a single set of input terminals on the mppt controller that now have 8 gauge wire from the solar panels so I don't think another set of cables will fit but if that is a consideration could I run the shore power through its' own mppt?

 

[wholybee]

I am not following, what is the selector switch for? I would recommend against trying to use your old shore charger through any sort of mppt or other converter. If your shore charger is not Lifepo4 capable, you need a new one.

 

[mikefitz]

Most shore power chargers will have a charge profile , whilst not ideal, could charge the lithium batteries OK, perhaps needing user intervention when the charge voltage reaches target, absorption value. ( turning the charger off).

I presume the two bank outputs on the charger are intended for starter and house battery.

One option would be to use the shore charger to charge the starter battery only , and let the DC to DC converter charge the lithium.
(I assume the Victron unit is a charger rather than just a voltage converter).

Using a MPPT solar controller fed from an unknown type of source may carry a risk of damage.

Its not clear how the selector switch is to be used but the alternator must always 'see' a lead acid battery load.

A diagram of the intended system and a specification of the shore charger would be useful.

Mike

 

[Brownhouse]

The selector switch is for away from the dock pos. 1 is for house batteries and pos. 2 is for engine starting batteries, agreed I need a new charger for the shore power input, any recommendations. Thanks

 

[Radio Waves]

Get rid of the old selector switch and simply install an ACR automatic charge relay). It will connect the batteries when it senses a charge current and disconnect when it senses a draw. This is how in installed on my Trawler. However, i am also replacing agm with lifepo, i am not 100% sure this acr alone will do the trick. i just am not sure the charge voltage are the same for lifepo and lead - however i am pretty sure they are. seems like you have a dc to dc anyway.

 

[wholybee]

Get out a piece of paper and start drawing. There are many ways to skin a cat (not that I recommend harming kitties)

You need to decide, are your charging sources going to connect to the Lifepo4, or the Lead acid? Then whatever they will not be connected to needs to be charged via an ACR, DC-DC charger, or isolator. You might not connect each source the same. For example, my solar is connected directly to my Lifepo4. My alternator is connected to my Lead. A DC-DC charger allows the alternator to charge the Lifepo4 as well as the Lead. For the rare instance it is needed, I have a battery combiner switch, which could allow my lifepo4 to assist starting, or allow the lifepo4 to charge the Lead, or if the Lifepo4 completely goes south my Lead could run my house.

If you have or get a 2 bank charger, make sure that it supports different chemistries on each bank, or opt for a single bank charger and a dc-dc charger to charge the other bank.