Sea of Cortez LifePo4 Solutions

[svConcordia]

Folks ... While my thread may be betters suited for the beginner's corner, fellow boaters may better understand my challenge.
We have been commuter cruising our 43 foot Cape North Cutter Concordia in the Sea of Cortez for three years now. The first two years we were able to visit the boat twice, with one trip earmarked as "maintenance," which meant the wet cell (4 6v 240ah golf cart batteries) took about 1.5 gallons of distilled water each visit (about 6 month interval). Work and an emergency room visit precluded all trips to Guaymas in 2019 and assuming our March plans go forward, Concordia will have been on the hard with no visitors for 16 months. So, yeah, pretty sure the house bank is done. As our commuter cruising habits are likely to continue for another four to five years - and we don't want to continue wasting wet cell batteries - we are looking to replace with LifePo4 batteries, but need the community's guidance. Details about the ship's currents system:

• Charging System
  • Three 100 watt Renogy Monocrystalline Photovoltaic PV Solar Panels
  • Victron MPPT 100/30 with VE. Direct Bluetooth Dongle
  • 50 amp engine mounted alternator (no smart charging, stock alternator for Bukh DV-36)
  • 30 amp smart charger (when shore power is available)
• Major Demands
  • Raymarine autopilot
  • Radar
  • Frigoboat 12v Refrigeration
  • Inverter (usually runs a hand mixer, shop vac, electric drill)

In general, the 480ah wet cell system has been adequate during offshore passages. The proposed plan is to replace the house bank with a 380 to 400 ah system (e.g. 8 3.2v 190ah or 200ah, wired in series and parallel). Questions:

• Battery Management System n' stuff: I'm a bit bewildered on which BMS to pair with this system and whether there are any conflicts/opportunities with the Victron MPPT. In another thread, there seemed to be a discussion over BMS that networks with the Victron.
  • Does the BMS matter in relation to the MPPT?
  • Is there an advantage with a BMS that networks with the MPPT?
  • Anything else that needs to go into battery box or connected to the system? 12v relay terminal?
• Storage: Baja is an extreme environment and Concorida will go for months without a visitor and temps can run well into the 100s.
  • While there is a minor current draw while away (I leave a radio and some 12v fans running), what happens when it is left alone for a year and no major load?
  • If there interior of the boat is 100+ degrees, is there any safety or system risks? Should I build a battery box that incorporates a 12v fan?
  • Is there a BMS that can be programmed to place a periodic load on bank (and is this important)?
  • Or should I plan on hauling the house bank home ... even though it will be a 16 hour drive?

Really appreciate any advise, including thoughts/direction on alternatives.
Thanks

 

[Picasso]

Contact these guys, http://www.pomcube.com/ major battery/inverter mfg out of China not in the US yet but has the cheapest life4 batts you can find down in Mexico and designed for the heat of Baja. I have played with the netzero from them. nice build quality.

Or the stay everything 12v easy way is BattleBorn, it has a good amount of marine users the battery is sealed for "life"

You will want to get a controller for your alternator, 30amp shore smart charger? might be lead acid profile only?

 

[nibs]

If the boat is on the hard, why not disconnect the batteries when you leave her?
You are overcharging the batts, can you not set your controller to a lower voltage?
If it took 1.5 gallons to top up 4 golf cart batteries, the plates were exposed and therefore compromised.

 

[svConcordia]

If the boat is on the hard, why not disconnect the batteries when you leave her?
You are overcharging the batts, can you not set your controller to a lower voltage?
If it took 1.5 gallons to top up 4 golf cart batteries, the plates were exposed and therefore compromised.

Nibs - Yes. The golf cart batteries have been compromised. I'm fully expecting that a substantial amount of the plate will be exposed when opening the fill ports (in the past, they were just below the surface). Don't recall if I can set the Victron to a lower voltage.

As for a full disconnect, I've been considering that as well for a couple of reasons.
1) Am I better off to have the cells held at 100% for, say, six months with a very minimal load on them vs. disconnecting and have them potentially run down to zero? EG is the degradation between the two about the same?
2) If leaving them plugged is better, am I offsetting the the anticipated degradation if the system is exposed to say, 6 months of summer temps with 8 hours in excess of 100 degrees every day?

 

[nibs]

They will definitely do better disconnected. As long as they are fully charged. They do not start sulfating until they are at or below 12.2 Volts.
New batts on store shelves do fine in storage for a year or two.

 

[backwash]

....delete

 

[nibs]

OP said
"Concordia will have been on the hard with no visitors for 16 months. "
I said
"If the boat is on the hard"
My advice would have been very different if the boat was afloat.

Sailed around Partida Island, La Paz, Cabo etc in 1980, man have Cabo and La Paz changed, they are big cities now.

 

[svConcordia]

OP said
"Concordia will have been on the hard with no visitors for 16 months. "
I said
"If the boat is on the hard"
My advice would have been very different if the boat was afloat.

Sailed around Partida Island, La Paz, Cabo etc in 1980, man have Cabo and La Paz changed, they are big cities now.

They have definitely grown up. Cabo and La Paz are not what they were in the 80s. I think I'll go the disconnect route and sort through more frequent trips to recharge.

 

[FilterGuy]

I think I'll go the disconnect route and sort through more frequent trips to recharge.

The good news is the LiFePO has a very low self-discharge rate and can tolerate partial charge *much* better than any lead-acid so you should be able to go many months if needed.

In your description, the only thing that concerned me is the high temp. "6 months of summer temps with 8 hours in excess of 100 degrees every day?" Is it hotter in the boat? If so, you may want to leave them hooked up (with the solar) and run some vent fans to try to keep the temp a bit lower. I am guessing you leave the radio on to discourage things from walking away.... so there is another reason to leave them hooked up. The main thing 100deg will do is accelerate the ageing....but I don't have a good handle on how much it will accelerate the process.

 

[svConcordia]

The good news is the LiFePO has a very low self-discharge rate and can tolerate partial charge *much* better than any lead-acid so you should be able to go many months if needed.

In your description, the only thing that concerned me is the high temp. "6 months of summer temps with 8 hours in excess of 100 degrees every day?" Is it hotter in the boat? If so, you may want to leave them hooked up (with the solar) and run some vent fans to try to keep the temp a bit lower. I am guessing you leave the radio on to discourage things from walking away.... so there is another reason to leave them hooked up. The main thing 100deg will do is accelerate the ageing....but I don't have a good handle on how much it will accelerate the process.

I leave the cabin fans on to circulate air within the boat during storage. It also places a small load on the batteries, which are fed by three 100w panels. The radio is mostly just to add another load on batteries (though I don't know if it matters for the wet cell batteries). As for the temperature: International Station Meteorological Climate Summary for Guaymas has six months with average temperatures over 90 degrees F: May, June , July, August, Sept. and October. May and October are 90 and 91, respectively, with the others at 96, 97, 96 and 96, respectively. When we relocate her to Puerto Penasco, this hot weather window shrinks slightly, with 89 degrees at June 13 to Oct. 3 and a peak of 95 in mid-August. As the hull and deck are light color, my presumption is the interior temperature is at or near the outdoor temperature. One option I have thought of is to equip the LiFEPo battery with fans and a heat sink. The fans would be on a temperature switch. While this would remove heat, I don't know if would lead to the batteries being less than the ambient temperature. Thoughts?

 

[FilterGuy]

I leave the cabin fans on to circulate air within the boat during storage. It also places a small load on the batteries, which are fed by three 100w panels. The radio is mostly just to add another load on batteries (though I don't know if it matters for the wet cell batteries).

If the fans are keeping the cabin temp from getting hotter than the outside, then I would say keep them. If not, I would say you might be better off just disconnecting the batteries while you are gone. The cells typically have ~2%/month or less self discharge. If the bms is taking any power it would be more than that but even at 5% it would take 20 months to drain them from 100% to 0%. By disconnecting them, you are not actively charging or discharging while they are warm and this is probably better.

Note: There is some debate about the proper 'storage' of batteries. A lot of the cell manufactures say to store them at ~50 SOC. However other folks say it is better to start at a high SOC and let them self-discharge down so they don't get too deeply discharged.

As for the temperature: International Station Meteorological Climate Summary for Guaymas has six months with average temperatures over 90 degrees F: May, June , July, August, Sept. and October. May and October are 90 and 91, respectively, with the others at 96, 97, 96 and 96, respectively. When we relocate her to Puerto Penasco, this hot weather window shrinks slightly, with 89 degrees at June 13 to Oct. 3 and a peak of 95 in mid-August. As the hull and deck are light color, my presumption is the interior temperature is at or near the outdoor temperature. One option I have thought of is to equip the LiFEPo battery with fans and a heat sink. The fans would be on a temperature switch. While this would remove heat, I don't know if would lead to the batteries being less than the ambient temperature. Thoughts?

The fans would not reduce the temp below ambient. The primary purpose for fans would be if the cabin temp was hotter than outside, you could vent the cabin to keep it closer to the outside temp.

This area of keeping the batteries cool is not something I have had to deal with (My installations are all in cooler climes and I have to keep them warm) It sounds like the batteries will be in an *average* temp of 100 or less and you are not putting any significant load on them. From what I understand, This storage temp is certainly not good, but my gut is telling me it is on the cusp between not good and bad. If it was just a little cooler, I would definitely say the easiest thing would be to just live with the slight lifetime degradation.

I have a few ideas about active cooling that I am pondering. If I decide I think the ideas might have merit I'll post them.

 

[FilterGuy]

BTW: How cool does it get at night?

 

[svConcordia]

BTW: How cool does it get at night?

In the middle of summer the night-time low (at about 6 a.m.) is about 10 degrees less than the daytime high. Humidity will reach 90 percent throughout the summer. Thanks!

 

[FilterGuy]

Ok..... not much cooling at night.

 

[FilterGuy]

@astronom on this thread said he was looking at a Peltier heating system. The interesting thing about a Peltier module is that if you reverse the current it becomes a cooling element.

Here is a Youtube vid that gives a 101 on Peltier:

You could use a Peltier, heat sink and Fan to create a cooler for a insulated battery box.

A few comments:
The cooling efficiency is horrible, but if you arn't there,who cares? You have a whole solar bank of unused power.
The humidity could be a big problem if any of the cool surface is exposed.
I don't know if they still make them, but they used to make 'coolers' that had this built in..... that might make an interesting battery box.

 

[FilterGuy]

Take a look at this. (It uses a peltier)
https://www.amazon.com/Igloo-Iceless-Thermoelectric-Cooler-26-Quart/dp/B007ZYIFQ0/

(If you search for "Plug in car cooler" you will find a bunch of these.

Drill holes for the wires and this cooler could be your battery case that also cools the batteries.

Note: if you do this, you definitely want vent fans from the cabin to the outside. It will generate a fair amount of heat in the cabin. (The ideal situation would be to vent the hot exhaust from the cooler to the outside.

You also might want to rig a thermostat inside that cuts it off around 70 deg just so it does not work more than it has too. (It might not be able to get it that cold anyway) You could also set it up to only cool in the day when power is being generated.

NOTE: I have not done this. It is just an idea I had that might be worth exploring.

 

[svConcordia]

@astronom on this thread said he was looking at a Peltier heating system. The interesting thing about a Peltier module is that if you reverse the current it becomes a cooling element.

Here is a Youtube vid that gives a 101 on Peltier:

You could use a Peltier, heat sink and Fan to create a cooler for a insulated battery box.

A few comments:
The cooling efficiency is horrible, but if you arn't their, who cares? You have a whole solar bank of unused power.
The humidity could be a big problem if any of the cool surface is exposed.
I don't know if they still make them, but they used to make 'coolers' that had this built in..... that might make an interesting battery box.

That is a genius solution. The version he displayed on the video is available on ebay for under $30. Not sure if the energy demand can be accommodated the planned house bank.

Working current: 10A
- Working voltage: 12V
- Power: 72w

 

[FilterGuy]

Yup, that is a lot of power.... but it feels like there may be a solution in there somewhere. Even if it only ran a few hours a day it might make all the difference in the world. If the batteries stayed under 90F, I would not worry at all.

 

[FilterGuy]

BTW: There is good reason not to let it get too cool: Condensation.

All of that frost in this picture is moisture that came out of the air.


I poked around on dew point and found this:
https://weatherstreet.com/weatherquestions/What_is_dewpoint_temperature.htm

While relative humidity is (as its name suggests) a relative measure of how humid the air is, the dewpoint temperature is an absolute measure of how much water vapor is in the air. In very warm, humid conditions, the dewpoint temperature often reaches 75 to 77 degrees F, and sometimes exceeds 80 degrees. No matter how hot the temperature gets, a dewpoint temperature of (say) 75 deg. F always represents the same amount of water vapor in the air in absolute terms (but different relative humidities).

So, if the mean temp of the box was in the low 80s you would only have to worry about condensation on the cooling element. If the cooling element is in a sealed box, you only have to worry about the moisture in the air when you close up the box. Meanwhile, I would not worry at all about batteries in the low 80s.

 

[FilterGuy]

One more thing: There are lower power peltier modules.... I would *guess* a 5 amp module would do what you need if the box is very well insulated.... we are only trying to get the temperature down 10-15 degrees. Also, if you set it up to only run when you have solar, it would not drain the battery but still provide the cooling during the heat of the day.