Inverters, solar panels and battery bank ?'s

[Blowncar]

Currently I have 2 battery banks (32v) on my 52C. I do not have an inverter but i'm looking for a simple (if possible) system to power my fridge and a few low power items while underway. I prefer it to be stand alone battery bank. I have a tuna tower with a hard top roughly 3'x5' i'd like to place the panels on top of so they would be out of sight and the batteries underneath in the lazarette.

Curious how many batteries (all 12v I imagine) i might need. If i want to run ac i'll run the genny so i don't think i need a huge reserve. Suggestions on which panels and inverter to consider? Also I'm looking for a schematic on how to wire it all up. thanks

 

[Pascal]

It really depends on your fridge and how old it is. The newer ones are much more efficient. I used to have 8 6 volts golf cart batteries as an inverter bank on my 53 giving me 18 hours mostly running an old GE fridge freezer. I bet the new fridge will use half of that whenever I put an inverter back in

Golf cart batteries are great for inverters.

Personally I would never use the existing banks for an inverter

 

[Blowncar]

My fridge is 2 years old so it's fairly efficient. I use golf type batteries already and really like them. I was thinking maybe 300w of panel(s) and 4 t875 8v batteries would be enough. So cal and mexico area so getting a full issue of sun isn't a problem. What size inverter would you suggest?

 

[Pascal]

Bigger is better as you won’t be pushing it as hard. Internal wiring and circuitry will be better able to handle the load and not near the limit. For just a fridge and a couple of low load outlet I’d use at least 2000w, ideally 3000

It also depends how you wire it to the boat. If you wire it as an independent source as if it was a second gen then size isn’t critical as long as you turn off breakers before switching not inverter. If you are going to use a built in automatic transfer switch you need an inverter big enough so that in pass thru mode the internal breaker doesn’t trip

Whatever you do, get a marine inverter, not an off grid or Rv unit. Marine inverter have circuitry that bond N to G in inverter mode only. When charging or when turned off, N to G are not tied together. This is becoming critical as marinas switch to GFCI pedestals

 

[Sandiego]

If you expect to run the genset daily based upon my experience I could suggest
Victron 3k Inverter/charger 24v around $1500
At least 400 watts of solar but 600 would be better to keep up with the regular loads during the day. My boat with a fridge and a chest freezer and some other light load consumes about 300 watts average during the daytime. Your solar even in Socal will not ever give you 100% rated and much less during the AM and later PM. Thus my suggestion for 600W.
Then take a look at Ampertime LiFePo. Batteries. About 400 AH should be enough to get you through 24+ hours with the solar recharging and the occasional run of the genset for cooking or hot water.

 

[Boatsb]

Victron supports a networked bms. Either canbus or ve.bus. they also do not support the batteries you suggested so if there is a problem your on your own.


I've pulled renogy and other batteries out of systems that were not working right. Don't cheap out on the batteries. The internal battery bms is not the way to go.

 

[scottinsydney]

The simple system we used before migrating to our 48v lithium house bank was.....

32v house bank > 20amp Newmar 32v to 12v converter > DC to DC charger > Single 12v lithium battery > 1200 watt inverter.

It worked like a charm for six years for all the AC lights, power outlets and 24/7 fridge. Solar panel / genset kept batteries topped up. DC to DC charger on lithium setting never depleted 32v bank.

Here is the DC to DC charger... https://enerdrive.com.au/product/12v-40a-dc2dc-battery-charger/

We now use the DC to DC charger to keep 12v lithium battery topped up for 12 volt electronics.

+++In both cases the 12 volt battery needs to be located beside the inverter or near the 12 v load.+++

PM me if you'd like a diagram.

 

[Blowncar]

great help thanks, learning

 

[metama]

A lot of the 300-400w panels are bigger then your hard top.

Calculate your AmpHour needs for your battery. For Lead/AGM batteries use half the Amp Hours, Li you can fully drain. I put a 24V alternator to charge the banks when running, just be careful with charging amps and very carful if you go lipo or something like that requiring a regulator.

I have 440 Amp Hours at 24V. Need more on my 53 with 5 people.

https://balmar.net/multi-stage-regulators/
https://balmar.net/6-series-alternators/

https://www.victronenergy.com/inverters-chargers

 

[Boatsb]

We did a whole boat system with 660 AH at 24 volts. It's a 53 carver and after a long night running AC he was down to about 20%.

The customer loves the way its fully integrated and will add the same to his next (larger) vessel too.

I spent a bit of time on the design. Actually did layouts and drawings along with projections of energy use. We were right on with our battery and charger needs.

I'm sure there's a lot of 'people who did a system or two that know better though. Just read the posts.