Originally Posted by Duke 48
I am sure the answers to my questions are buried somewhere in this forum, but I have read so much about batteries, solar charging, alternators and AC chargers, the waters just keep getting more muddy.
My current plan:
- use two group 31 AGM 12 V batteries in parallel for the house bank.
- use a group 24 battery for the starting battery, could be either a standard lead acid or an AGM. (Daily load: 115 to 125 AH) (6 Volt batteries will not fit in the available space.)
- Solar -- Already have two 80 Watt and two 55 Watt panels. (Panels are 12 Volt.)
- Alternator -- Standard 55 amp.
- AC charger -- to be determined.
- Would it be better to set the system up using all AMG Batteries or to save some money and use a standard battery for the starting battery?
- What parameters should the AC charger have to satisfy the charging needs?
Your help in clearing up the water
will be greatly appreciated.
Whatever you do I would get a small 2-5watt trickle charging solar panel for the starting battery and leave it mostly separate from the house system. A panel that small doesn't even need a regulator
. This panel is to maintain the starting battery thru long periods disuse. It may be able to keep the battery changed if the engine is only started once a day or less.
IF the trickle charger can't keep up with the starting requirements either mount a second small alternator on the engine for it or get an echo charger (about $140). Personally I would go for the second alternator for redundancy.
For the house side it kinda depends on what you are going to do.
If you are not going to live aboard then the AC charger is not so important, you have plenty of solar wattage to keep up with weekend use, the solar panels will have 5 week days to make up whatever you took out over the weekend. Even if you take the boat out for 2-3 evenings a week plus all weekend the panels should be able to keep up. To get the most out of them get an MPPT
If you are living aboard
the situation changes. Then you need to consider how much time you will be at the dock
. If you are living at the dock
or coastal cruising and spending most nights in a marina, then an AC charger makes more sense. If you are spending 4 or more nights a week living aboard
at anchor or underway on passage
then you need to be looking at upgrading the solar panels and batteries, not getting a high end charger.
If you are spending 3 or 4 nights a week with AC available, then it would be a toss up to me, I would wait and see if I had problems with the amount of power I was consuming.
If you are not currently sure exactly how much you are going to be on the boat, try a wait and see approach.
If you are going cruising away from developed countries, get flooded batteries, you don't want to mix and match and gels and AGM's are not very available in developing places.
My understanding is that gels and AGM's do not have the life expectancy of flooded and they are more expensive. The tradeoff is that flooded require periodic maintenance
: you want to check electrolyte levels and densities monthly, top up with distilled water and equalize every 6mo or whenever there is a disparity between cell densities of >.020. I suspect the reason for the difference in life expectancies is that the gel and AGM batteries are manufactured as maintenance-free batteries when really they are reduced maintenance
batteries, though how you would maintain them if you had access is something for a battery scientist to explain.
If you are staying in the developed world then AGM's will decrease the maintenance load at the cost of replacing them more often at higher cost.
Check this link for a long-term cruiser's take on the battery choice issue:Systems
Get a small panel to maintain the starting battery.
Get an MPPT
controller for the solar panels.
Cruising away from the developed world:
Get flooded batteries.
Get a jug of distilled water and a good battery density meter
Make sure you have some means of doing an equalization
Cruising the developed world:
Get whatever batteries suit your fancy
Make sure your controller will deliver the appropriate voltages for the type of battery you have chosen.
Wait and see how you actually use the boat before investing in a charger that may see little use.