Solar Controller compatability - Page 2 - SailNet Community
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post #11 of 14 Old 10-25-2011
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Originally Posted by Turrama View Post
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.
I would not advise you to use your windlass off the starting battery. Wire the windlass to the house bank and double the size of it if you plan to spend time cruising. A single 100Ah battery will have 50 usable Ah's from 100% state of charge and only 30Ah's when cycling between 50% and 80% when off crusing. AGM batteries like to be recharged to 100% as often as possible so the solar is a good idea.

There is no such thing as "recharging the start battery first" with the ACR. It is a dual sensing device that automatically combines when a voltage of about 13.2V is present at either bank. If you are going to have a "dedicated" start battery I would use it as a dedicated start battery not a windlass and starting battery.

With a solar panel you will spend a lot of time "combined" and I generally don't like mixing battery types in this scenario. AGM and wet cells accept current very differently. As Brian said an Echo Charge would be a better choice if mixing types but then you REALLY DO NOT want to run your alt to the start bank or use a windlass off it.

Keep in mind that your Blue Sky will NOT combine the banks. It will divert a max of up to 2A to a second battery. Also I think that feature is only available in the iX models not the i models IIRC? You don't need that feature as you already have an ACR that will turn on an combine the banks when 13.2V is reached.

Like Brian has said you'll be best served to feed all charge sources to the house bank and also feed your windlass there especially with the Blue Sea DCP switch which does not allow you to choose a second or reserve bank when or if you need it..

Starting an 8HP diesel can be done with even the smallest of personal watercraft battery and AGM's make great starting batteries.

A 100Ah house bank is very small by today's standards but we don't know what you'll be using off it so it may be okay for a day or so....

-Maine Sail / CS-36T

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post #12 of 14 Old 10-25-2011 Thread Starter
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Hi Mainesail,
The boat is a piver nimble tri that is constrained by space and load carrying capability so increasing the house bank is not an alternative without serious modification to the layout.

On your advice I may need to look at 2 x AGMs.
I was considering wet cell to cope with 80-100A draw from the anchor winch even though this will be offset by the alternator charging during this operation.

I've received the following advice from the Blue Sky rep indicating the SB2512i does combine batteries using the 2A auxillary circuit.

"The auxiliary output is essentially a high side switch to battery plus. There is a 2A current limiter in the 2A charge output as shown in the auxiliary output “equivalent circuit” in the manual. The purpose of the auxiliary battery charge function is to maintain an infrequently used battery and not to charge a battery that is regularly deeply discharged.

The way the auxiliary battery charge function operates is that when the primary battery need all the available charge current (i.e., controller in Bulk), the aux charge is off. Once primary battery voltage rises to the charge voltage setpoint (at which time primary battery charge current need to be reduced to control battery voltage) the aux charge output turns on connecting the two batteries together through the 2A current limiter. Both batteries are then held at the Accp voltage setpoint until the primary battery is charged at which time the controller switches to Float and both batteries are then held at the Float voltage setpoint. The aux output is always off in Equalize "
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post #13 of 14 Old 10-25-2011
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While the auxiliary charge function of the Blue Sky is a nice feature in some situations it is irrelevant if you are using a Blue Seas ACR, as posted by Maine Sail. When the ACR senses a charge voltage at either battery and from any source it will parallel the batteries.

The windlass should be run off the house bank - usually much larger than the start bank.

I also agree with Maine that the house bank should be doubled in size if there is any but a few lights run off of it and you are cruising.

As posted any battery will start an 8 hp diesel.

You would be better in my opinion to buy 2 batteries of the same type and parallel them for a larger bank to be used for both house loads and engine starting. Run all charging outputs to this bank. Buy a small emergency battery, charge it with an Echo Charge and use a simple 1-2-both switch. I would skip the ACR and the Dual circuit switch. It is both a simpler system and one more suited to your use.

Living aboard in Victoria Harbour
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post #14 of 14 Old 10-25-2011 Thread Starter
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I was hoping to use the ACR as this has recently been installed but I see the sense in your advice.
Reconfirms the old adage about boating being akin to standing in a cold shower and tearing up $100 notes.
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