Appreciate advice or schematic on assembly of starting battery, DC to DC charger and solar house battery's. Problem - if solar will charge house battery ( victron MPPT ), how is possible to charge same time start battery and than when engine start, start battery will charge house battery. Isolated or non isolated charger ?
Will shore power effect this type of setup ?

Hi Krys
I hope this answer will be relevant.
I have a small boat with two lead acid batteries : one as a start and one as a house.
My aim from the start was to simplify my system and that meant removing stuff , not adding.
I have no high tech batteries or B.M.S.
My starting line for simplicity is to use as little power as I can get away with.
I have no DC to DC charger.
RE; Will shore power effect this type of setup ? By shore power I guess you mean mains supply ( 230Volts) to outlets for electric kettles and such. In that case there should be no problem with the 12 volt system in my diagram.
If you use shore power to top up batteries I would suggest clipping the charger to the battery you want to charge and NOT using a switching system. You can fit an automatic charge selector between the charger and the two batteries but my advice is DON'T.
Here is my diagram.




Part 1. The alternator is capable of charging the Start and house battery through an automatic charge selector.
it will charge the start battery first (so you will always have start charged( then switch to charging the house battery.
The start and house batteries are completely isolated except for the automatic charge selector.
This means that one battery cannot drain into the other through and 1-2--both- off switch. That beast went into the bin.

Part 2. A small solar panel tops up the engine battery when boat is standing for any time.
In actual use the engine charges the engine battery quite quickly, then selects the house battery.

Part 3. a slightly larger solar panel keeps the house battery topped up.

If I ever need a BOTH battery situation I have jumper leads to bridge the two batteries for the job. Have never needed that though.

here is what an automatic charge selector looks like. $20 on Temu.
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Voltmeters are these niffty units.

Gary

Go to the Victron website and have a look at their DC DC chargers, probably the Orion XS DC-DC Battery Chargers, and this should answer your questions.
I installed a Redarc dual input dc dc charger a few years back and it was a game changer - my batteries have never been so happy.
I have a lead acid start battery and Lithium house bank with solar and wind charging.
Shore power will have no effect, you need a separate charger for this.

Hi, I have had success with Victron MPPT to house and victron ciryx battery combiner connecting start and house, obtainable for lead to lead and lead to lithium, whichever chemistry you have.

I asked a similar question and did some experimenting with my setup.

Your engine will probably do a good job of keeping your cranking battery charged, likelihood is it only needs a quick top-up after starting the motor (you live in Brisbane yeah, so no sub-10 degrees C cranking like we have in victoria....)

What I found was that the engine/alternator was bad at was charging the house battery during the half-hour after a sail when the house battery has been comprehensively drained by 8-10 hours running lights, autopilot etc etc.

Your solar controller will take care of this problem by 1. doing a better job of charging the battery than the alternator ever will and 2. preventing your house battery getting so badly drained - at least during daylight hours.

You then always have the house batter to crank in an emergency.

Happy to have my understanding corrected - I haven't bitten the bullet on a charge controller yet but I did change my mains charger to charge the house battery from shore power, rather than the engine battery.

Probably seperate solar and mppt for startup battery would be simple ( disconnect when engine starts allowing startup and DC DC house charging )

Select to expand quote

Kryspen said..
Probably seperate solar and mppt for startup battery would be simple ( disconnect when engine starts allowing startup and DC DC house charging )

NO

Just get a decent DC DC charger and any charging problems will be solved with no switching required.

Select to expand quote

Lazzz said..

Kryspen said..
Probably seperate solar and mppt for startup battery would be simple ( disconnect when engine starts allowing startup and DC DC house charging )

NO

Just get a decent DC DC charger and any charging problems will be solved with no switching required.

Probably victron DC to DC . Already have Victron MPPT , stick to the brand .

Select to expand quote

Kryspen said..

Lazzz said..

Kryspen said..
Probably seperate solar and mppt for startup battery would be simple ( disconnect when engine starts allowing startup and DC DC house charging )

NO

Just get a decent DC DC charger and any charging problems will be solved with no switching required.

Probably victron DC to DC . Already have Victron MPPT , stick to the brand .

They are good stuff!!

I have a couple of their Mppt controllers & other stuff & will soon be getting one of their inverters. FWIW I have now come around to the thinking that their products are worth the extra $$

No affiliation but I have bought several items from these guys - great service: www.solar4rvs.com.au/victron-12v-to-12v-orion-xs-12-12-50a-dc-dc-emc-improved

Another excellent supplier is Preston off grid solar.

Hi Krys
can you post a sketch wiring diagram of what you have in mind?

gary