Originally Posted by Boatwright
I'm in the middle of planning & designing an updated DC system for our Hinterhoeller Niagara 35. We are looking forward to several years of summer cruising on the northern Great Lakes
The basic design parameter is KISS with 5 - 7 days between re-supply:
1) LED lighting
2) 100# Ice Chest with good insulation
. (I removed a 110 volt cold plate system if anyone is interested.)
3) 400 AH golf cart battery bank. Separate starting battery.
4) 100 Amp Alternator on Volvo MD11C diesel auxiliary.
5) DC energy budget maximum of 80 AH/day - 20% of battery capacity, with average budget less than 50 AH/day.
6) Experience with solar panels has been poor, leaving the system chronically undercharged, with sulphated batteries at the end of the season.
7) Would like to avoid the expense and complication of a genset.
Considering the above and acknowledging that engine driven alternators with conventional regulators are poor house battery chargers, I'm looking at the newer Sterling Alternator to Battery Charger/Regulator/Isolator.
, experience, and opinions would be appreciated.
The MD11C was fitted with a bunch of different alts over the years some Bosch, some Valeo and some Delco. The most common ones I see on the MD11 today are Delco's.
Keep in mind that you will be cycling in the most charge inefficient
SOC range of your bank. As such the bulk stage, alternator at full bore, will be very short. The bank will come up to target voltage quite quickly and then become "voltage limited".
From the point the bank meets target limiting voltage it is the battery that dictates the speed of charging. Only raising the voltage limit, eg; going from 14.2V to 14.8V, can change the amount of current
that can flow into the battery at a specific SOC. Once voltage limited you are at the mercy of the batteries charge acceptance rate.
It will still take many, many, many hours of absorption charging to get to 100% SOC, so unless you are running the engine for 4 - 7+ hours you will still be technically
under charging the bank by relying on an alternator.
If you are only going 5-7 days between a "re-supply
", which I am assuming
is a 100% SOC dock
side charge, then you are likely chasing your tail on this one and throwing money
at an issue that really is not much of one, which can be drastically improved upon.
This is where a well sized solar system comes in very handy, in providing a finish charge. Let the alt do bulk and early absorption and solar do the rest. This combo (or a generator for bulk & early absorption) will net you as close to 100% SOC each day as your going to get.
Your described usage does not necessarily warrant an external regulator, unless you need to boost the voltage to 14.8V or so for your particular batteries. If this is the case, and you need to boost to 14.8V, and your alt run times are generally under 4 hours, a replacement $13.00 internal Delco regulator would be a better deal than a $450.00 Sterling A2B especially when you may be able to attain 100% SOC every 5-7 days..
Delco internal regulators come in many different voltage limits some as high as 15V and some as low as 13.8V, and everywhere in-between. Without knowing your regulators voltage limiting set point it is really hard to say if spending the money on the Sterling A2B is going to be an improvement or not. When shallow cycling in a low Coulombic efficiency range it is not necessarily the amperage of the alternator but the voltage limit that really matters, as you will be voltage limited most of the time....
Sure the Sterling can boost
voltage to the bank, but can only do what I call a quasi-float. If your internal reg is set to say 14.8V to 15.0V, as many Delco's are, then the Sterling A2B can only drop the voltage by about .2V - .5V +/- across the device during float (passes through internal diodes). The A2B works best with a stock reg set to 13.8V to 14.0V. Again knowing your alts voltage limit would tell us a lot more.
The least expensive option, for performance external regulation, is to simply open up the Delco, bypass the reg, and tap into the the alts field brush. Most any good alt shop would charge about $30.00 - $50.00 to do that on a Delco. You will then be able to use a Balmar or other external regulator to control the alternator and you can save in excess of $100.00, and get true field control through external regulation.
As for poor experiences with solar, something was likely under sized or the settings or controller were not optimal for the bank or optimally programmed. A 50W panel is not really a suitable size for a cruising boat other than for a mooring
recharging or if you are very, very light on DC loads.. For solar to work optimally you need to have enough current to overcome daily loads, during sun up hours, to even begin putting energy back into the bank. In other words if you are using 4A and the solar panel can only produce 2.2A then you are only slowing the discharging of the bank
by 2.2A. If you are consuming 4A and the solar is pumping out 6.5A now you are charging
Unless you are running an alt for upwards of 4-7 hours, or a Honda gen, it takes lots of time to fully charge lead acid batteries. Even with a Sterling A2B you are not going to see 100% SOC very often relying solely on an alternator or even a Honda gen.
Anything below attaining 100% SOC, as regularly as is humanly possible, is where sulfation is not being reconverted. The longer the sulfate goes, before being reconverted, and we now have clusters and hard lead sulfate being formed and decaying Ah capacity.
Alternators are great for bulk and early absorption but on sailboats they are rarely run long enough to fully charge the bank regardless of the method of field control. What can help is fully charging the batts every 5-7 days, at their max allowable absorption voltage, and then hitting them for 30 minutes to hour or so with an equalizing voltage (as long as they can be EQ'd).