No worries on the battery charger.. as you mentioned it is the time, and the only time you will feel a pinch here is if you are really pulling the batteries down and don’t have enough time for the charge cycle to complete before the next outing.
I will suggest you get a hydrometer and check the gravity on the batteries regularly until you can bench mark how they are doing. What you will be looking for is overall specific gravity, and a balance between the cells. At least once a month you will want to run an equalizing charge on your batteries, in the noco manual it is called repair mode, this will correct the main problem you will have which is stratified electrolyte, this mode will not only increase the overall gravity but will balance the cells. I’ve seen a lot of people not do equalizing charges on their FLA batteries and then complain there is not enough capacity and add more batteries (huge weight gain) and still not have the capacity they are looking for. Fun fact, FLA deep cycle batteries typically need about 8-12 cycles from new before they reach full capacity. You will also notice in the fine print of the noco charger user guide it mentions a “typical” discharge which is 50% or rated capacity, so a 100Ah battery is only capable of 50Ah of discharge without degridating the life span of the battery. Typical life span of a FLA battery is 500 cycles. Again, this gravity / equalizing charge can be bench marked and you can develop a schedule over time to how often you need to do it.
The batteries; I think if you can change out that start only battery to the SRM-27 battery that you bought it would be good. Our engines don’t draw a lot of cranking amps in the first place and the specs on the SRM 27 (stick with the group 27’s) look pretty good, 88 Ah rating so you’ll have 44Ah’s for each battery. Be sure and pick up a jump starter pack to keep on board just in case you or someone else needs it. I only run a group 24 start battery because it is a dedicated start battery, your situation is a bit different though and you may want to alternate your batteries for deep cycle usage.
In addition, I’d put one of these smart shunts on each of your house batteries, they’re about $100 bucks and are configurable to any battery chemistry and Ah rating, then you will know for sure how much power is left in each battery SOC or state of charge, how many Ah’s & KWh’s you have used, and voltage of the battery etc. They are very small and connect via the Bluetooth Victron app which is free. And you will see current flow in each direction in real time, so when you are at the sand bar / beach you will see negative or minus current and when you are underway you will see current without a — in front of it meaning current flowing into your battery from the engines, and the SOC will update in real time. I know you are on a budget, but these things are priceless in that you will KNOW how much battery power you are using. I suppose you could put just one of them on the main ground between the batteries and ground, as long as you just were to use one battery you’d know what you did to that battery without having to guesstimate the useage of the other battery if you switch over to it. Myself, I want to have one battery that is reserved for engine starting only.
The SmartShunt is an all-in-one battery monitor, only without a display. Your phone acts as the display. The SmartShunt connects via Bluetooth to the...
www.victronenergy.com
This information will be valuable down the road if you ever decide you need more capacity, your usage sounds like you might be a candidate for a LFP battery which are expensive but well worth the performance and weight savings. But that is well down the road.
