battery protection

[bwbutler]

I own a sailing catamaran that we will be leaving in GA for the hurricane season. We want to have some kind of dehumidification on the boat but shore power will not be available. We have 1000w of solar on the boat and about 400 ah of battery storage, but I do not want to risk totally depleting the batteries in the event that the solar cannot meet needs for a few days. I anticipate a dehumidifier load of about 600 w. My question is if there is a component that I can install that will disable the inverter and associated load in the event the batteries are depleted below a specified level and then reset when solar begins recharging the batteries?

 

[sailingcal21]

An Voltage Sensitive Relay would do the trick. Or perhaps you solar charge controller or inverter has a battery protect function.

Need to know what type of batteries and system voltage. Charge controller and inverter would be helpful as well.

 

[sunshine_eggo]

I own a sailing catamaran that we will be leaving in GA for the hurricane season. We want to have some kind of dehumidification on the boat but shore power will not be available. We have 1000w of solar on the boat and about 400 ah of battery storage, but I do not want to risk totally depleting the batteries in the event that the solar cannot meet needs for a few days. I anticipate a dehumidifier load of about 600 w. My question is if there is a component that I can install that will disable the inverter and associated load in the event the batteries are depleted below a specified level and then reset when solar begins recharging the batteries?

600W on only 1000W of solar may be a big ask.

Need more information:

Brand and model of inverter
Brand and model of MPPT
Chemistry and capacity of batteries
Anticipated solar performance, i.e., will panels be flat or tilted, shaded or no shade with good exposure from sunrise to sunset?

 

[bwbutler]

Wemjust bought the boat so dont have all of the information. We are not at the boat right now, but the batteries are lifepo and the controllers are victron, dont have the model numbers. Not sure of the inverter. The panels are flat and are located on top of the cabin, in a fairly exposed position. Will have more info in a week when we are back at the boat.

 

[bwbutler]

The batteries are ampere time 200 ah lifepo. there are three of them. They come with internal BMS. Maybe the BMS will prevent the possible damaging discharge. Just trying to understand system needs and possibly power a dehumidifier a few hours each day.

 

[sunshine_eggo]

The BMS will protect the batteries, but it can also prevent the solar from working once the BMS has tripped. The MPPT is powered by the battery. If the battery is disconnected due to low voltage protection, the MPPT can't receive power from the battery.

600Ah * 12V = 7200Wh = about 10 hours of run time on your 600W humidifier.

Assuming your 1000W can harvest about 2000Wh/day (flat panels, winter sun) - that's a little over 3 hours of run time daily with batteries finishing the day fully charged.

The simple solution may be to have a timer that only allows the humidifier to run from say 10:30am to 1:30pm.

I personally use a wi-fi connected outlet that I can control remotely. It's on a timer that turns on the water heater for a couple hours a day. This allows me to leave the water heater filled when I winterize the RV. If you have internet access at the boat, this might be an option for you.

 

[sailingcal21]

Sounds like a relatively current system. I suspect that the Victron controllers will have an adjustable battery protect function that you can use with a simple relay to shut down loads should the battery voltage get too low. One cool thing about the Victron MPPT controllers is they have an adaptive battery protection algorithm that may prove helpful. It's not prudent to use the battery's BMS for this function.

The good news it that you have LFP batteries which can take a good bit of abuse as compared to FLA.

Once you post the system component part numbers more guidance can be provided.

 

[Bluedog225]

I’ve often thought a dead simple electronic timer powered by the battery bank would be the way to go. No (slight) chance of it losing time due to power outage.

I imagine the dehumidifier will have high [edit] locked rotor amps.

 

[sunshine_eggo]

Sounds like a relatively current system. I suspect that the Victron controllers will have an adjustable battery protect function that you can use with a simple relay to shut down loads should the battery voltage get too low.

That would probably work. Got any suggestions for a realy?

One cool thing about the Victron MPPT controllers is they have an adaptive battery protection algorithm that may prove helpful. It's not prudent to use the battery's BMS for this function.

Please elaborate. I don't see how the MPPT adaptive battery protection in any way applies to this scenario, LFP in general or a BMS specifically.

I’ve often thought a dead simple electronic timer powered by the battery bank would be the way to go. No (slight) chance of it losing time due to power outage.

I imagine the dehumidifier will have high [edit] locked rotor amps.

Most Victrons are LF inverters with good surge, so I doubt that will be an issue, but it's definitely a detail to sort out.

 

[sunshine]

I own a sailing catamaran that we will be leaving in GA for the hurricane season. We want to have some kind of dehumidification on the boat but shore power will not be available.

I don't have a boat and would realise that there is a difference between the GA shoreline and outback Australia However my experience with drying corn was that the highest humidity is at night. Rendering solar not very suitable for this application.
Save the battery for the dehumidifiers above the keels....the bilge pumps!