On the new catamaran, we have gone with 750AH of AGM batteries (hurts me to say but we couldn’t justify throwing out the existing batteries and going Lithium straight away). These will be charged with:
- 2000W of Sunpower solar panels out the back.
- An Onan 11KVA genset hooked up to two Victron Multiplus 80A/2000W Charger/Inverters
- Two 115A Mitsubishi alternators that come with the Volvo Engines, which I’ve been told are excellent alternators.
- No wind generator this time!
One of the useful additions I did to my previous boat was install a pair of Mastervolt Alpha Pro regulators, hooked up to the standard alternators to provide intelligent 3 phase charging; making the alternators much more efficient, whilst providing an added level of protection for the batteries. After putting in a bit more research waiting impatiently for our new Saba to be built, I’ve looked at three solutions:
Installing two Wakespeed WS500 regulators (http://wakespeed.com/products.html).
Seabits(https://seabits.com/wakespeed-ws-500-regulator-review/), Panbo (https://www.panbo.com/how-wakespeeds-ws500-alternator-regulator-solves-complex-charging-issues-a-new-approach/), Ghost and Catamaran Impi all use this solution and I rate their experience highly. This solution requires that I get the alternators modified to bypass their internal regulators. However there are a few internet posts suggesting that Volvo take a dim view of these alterations, vis-a-vis their warranty.
My second option is to leave the alternators as is and use a couple of Sterling DC to DC chargers to charge the house batteries.
My third option is to install a couple of VRC-200 Charge Reference Controllers (http://nordkyndesign.com/product/nordkyn-electronics-vrc-200-charge-reference-controller/) from Nordkyn Designs, a small New Zealand outfit. The beauty of this solution is that I don’t have to modify the alternators, their reference engine is the same Volvo D Series engine as isused on our Saba 50 Catamaran, and this option is also the cheapest one. It’s quite a clever solution, using the voltage sensing input on the alternator to drive intelligent 3 phase charging. In talking to Eric from Nordkyn Designs, he suggests hooking each of the VRC-200 units (NZ$475) to a Victron Argo FET Battery Isolator ($140US each) to charge all three battery banks from each alternator, eliminating the possibility of a flat starter battery causing any grief. One running engine will start the other, even with a near-dead battery.
All three options provide intelligent 3 stage charging for the house batteries. They also work for both AGM and Lithium Batteries. I’m leaning towards Nordkyn Design’s solution because of its simplicity and seamless integration.
To complete my solution, we will install a Victron BatteryProtect after the house bank to ensure my batteries don’t drop below 50%, even if it means turning off the boat power. I will set up an alarm on the Victron monitoring so that we know when it is approaching this low SOC.
Talking of power monitoring, Victron also has some interesting upgrades that we will take advantage of. We want to hook up all our battery monitoring to a Cerbo GX and it’s companion screen – the GX Touch 50. We can connect our two Multiplus 80A/2000W Charger/Inverters, MPPT Controllers and BMV-712 Battery Monitor, as well as some temperature probes for the engine rooms, to give us a complete view of all our power usage and generation. These units supersede the GX Colour Controller we had on our last boat. We can hook this Cerbo GX up to Victron’s VRM solution to allow us to see what’s going on when we are onshore or travelling away from the boat.
My plan is to buy all the necessary parts in the USA and take them with me to La Rochelle, where I have the whole winter to install stuff and get it working.