Solar Controller compatability

Turrama · #1 (**permalink**) 10-12-2011

Hi everybody just registered and would like some advice if possible.
I'm in the process of refurbishing a small tri for family holidays.
I've fitted new eletric loads throughout the boat and I'm upgrading the electrical system.
The boat has a small 60amp alternator /8hp diesel and 2 x solar panels.
I've fitted a Blue Sea add-a-battery kit and a Victron 602 to monitor battery performance.
I will be installing 1 x (AGM) 100ah house battery and 1 x start battery.

I installed the automatic charging relay on the add-a-battery kit to charge the start battery before combining with the house battery for charging.

I would like to install a multi stage solar controller to charge the house battery before charging the start battery.

I'm expecting to have a charged start battery after anchoring and supporting the house battery with the solar system while on the hook.

Do I need to manually switch between systems at engine start and shut down or will both systems allow for each other?

mitiempo · #2 (**permalink**) 10-13-2011

Welcome to Sailnet

Ideally the charging should go first to the house battery - the battery that will always need the most charge. The solar output can also go the the house battery and the ACR will take care of the start battery. The start battery will never need much charging as long as its use is limited to engine starts.

Are both batteries AGM? Are they the same size?

The charge outputs with an ACR should go to the largest battery or bank - which is never the start battery. The ACR is dual sensing so the change needed is to switch the alternator output to the house battery.

You don't say what wattage the solar panels are.

The controller, which should be an MPPT controller, should also go to the house bank, the ACR taking care of the start battery here as well.

The Victron monitor is a good choice.

I, and many others are not fans of the Blue Seas switch in the kit (Dual Circuit Plus) because it doesn't give you the option of using the house battery to start without combining the banks. If one battery is too weak for an engine start the last thing you should do is combine it with a good battery - especially with AGM batteries and their high acceptance rate - one result could be 2 batteries that will not start the engine as the good equalizes quickly with the bad.

Manual switching will not be required.

Turrama · #3 (**permalink**) 10-13-2011

Thanks Brian,
I guess I held back a few details to keep it simple.
I am thinking of using an 80ah Expanded Calcium Grid (EXG) battery for the start battery.
This will have a dual role to start the engine and to run the freedom anchor whinch with the deck hose pump. (both these units will only being running while the engine is going).

Therefore the auto relay has been connected to the start battery to allow re charging immediately after anchoring.

I agree the battery combination is a trap and would only be useful if the battery state of charge is marginally different.

The existing controller is an 8 amp shunt type and I would like to upgrade to achieve charge efficiency.

The solar panels are in storage at the back of the shed so not sure of the capacity.

Good to hear an MPP controller will look after itself, I was wondering if the auto relay would see the solar controller voltage on the house battery rather than the true battery state of charge and get confused.
I suppose it does not really matter (the engine will be delivering a stronger charge anyway)
as long as the controller takes over after the engine is shut down.
Cheers
Peter

mitiempo · #4 (**permalink**) 10-13-2011

Peter

When an ACR is used the charging should go to the largest battery or bank to avoid chattering of the relay.

Your choice of different battery technologies, combined with the use of an ACR, which parallels the batteries during charging, is not a good idea. As the chart below shows (from a Xantrex TrueCharge manual) calcium batteries and agm batteries have very different absorption voltages. ACR's should only be used between batteries requiring the same charging voltages. If the alternator and solar controller are set for agm voltages the start battery will not get a full charge, shortening its life. If set for the start (calcium) battery the house (agm) battery will have a very short life.

An Echo Charge instead of an ACR would be a better choice with different battery technologies.

Turrama · #5 (**permalink**) 10-13-2011

Well that's torn it !
What about if I use calcium batteries of the same size for both house and start?

mitiempo · #6 (**permalink**) 10-13-2011

Or agm for both, or the best value, good flooded batteries for both.

Turrama · #7 (**permalink**) 10-13-2011

Thanks Brian
I had based my battery selection on the idea that AGM would not stand up to cranking the diesel and that sealed was better than battery fumes inside the cabin.
Which way would you go agm or calcium ?

mitiempo · #8 (**permalink**) 10-13-2011

I would go flooded as a first choice, 2 golf carts in series for the house bank and a 12 volt for starting. 2 golf carts will give you a house bank of between 225 and 240 AH.

Flooded are very close to agm in charge voltages so they could be mixed.

If being sealed is important either 2 agm or an agm and a sealed flooded battery for starting.

Almost any battery will start an 8 hp diesel - I have a Yanmar YSE-8.

Turrama · #9 (**permalink**) 10-13-2011

Brian,
Thanks for your time and information.
I need to nut this out further but i will follow your advice.
cheers
Peter

Turrama · #10 (**permalink**) 10-25-2011

I think I might have a solution.

I am planning a 2 battery system that will incorporate 2 x KW 80w panels charging through the Blue Sky SB2512i mppt regulator to a 105a/h deca seamate AGM battery.

The AGM will be the primary battery and there will be 100a/h flooded cell auxillary battery to provide CCA capacity for engine start and anchor winch.

The Blue Sky regulator has a dual battery function that will combine the auxilary battery once the prime battery charge setpoint has been reached.

Noting the absorption voltage for AGM is 14.3v and 14.4v for flooded therefore these batteries will be compatible when combined.

As noted previously on the engine side I have a 60A alternator charging through a Blue Seas automatic charging relay (ACR) this will perform a similar function to the Blue Sky regulator in that it allows one battery to receive charge until a set point is reached and then both batteries are combined.
The 60A alternator will charge the start / anchor winch flooded cell battery as the prime before combining both batteries for charging. (this will ensure the start battery is always ready for an emergency)

Therefore the primary battery when the solar system is charging will be the AGM and the primary battery when the alternator is charging will be the flooded acid battery.

I understand from the Blue Sky distributor that the solar system can remain connected while the alternator is charging.