Supplementing with solar

[kennharriet]

We have been on the north BC Coast the past three weeks. We are minimalists with power needs but our house batteries get down to 12.3v -12.0v daily unless we are traveling and recharging each day. We have a Victron charge controller, two 85 AH AGM house batteries and a lead acid start battery. Our biggest overnight power draw is the Engel cooler that makes ice for the ice chest. For future planning, what makes the most sense? Is there a small flexible solar panel that would help us get through a couple days at anchor? Should we look at going with higher amp hour house batteries. Thanks in advance. Ken

[WCF]

85ahx2 AGM means you have 85ah total available if you are keeping within the safe 50% discharge.

That means that one lightweight 100ah LiFePO4 battery (which can be discharged 100%) will increase your available power by 15ah.

If you are going for long periods without charging, you will have to do the math on your average loads and what you expect to get from solar. The typical 50 and 100 watt flexible panels don't add much in the Pacific Northwest in my experience. A battery monitor and shunt helps a lot with figuring this out.

If you want a budget LiFePO4 option, I have had good luck with Li Time, and their new "mini" 100ah battery solves a lot of packaging issues: https://amzn.to/3oRVqJK

[kennharriet]

We are right on the edge so maybe another 15 AH would do it. Would be happy to get two days at anchor without running the motor. I did not realize that 2-85 Ah batteries only provided a total of 85 ah. The 100 Ah Li battery you suggest is less than what I paid for the AGMs.

[thataway]

[WCF]

I agree with Thataway; I don't discharge mine the last 10% (Even if the potential for damage is debatable, having a BMS freak out from having 0 voltage is a risk.) I was just parroting theoretical differences in AGM vs LiFePO4

I would think 15ah is still probably cutting it very close; taking a belt and suspenders approach might be safer since you already have the solar controller. A 100w or 150w flexible panel even from a reputable brand is a fraction of what a battery costs... And then I would still go for a 200Ah if you can swing it.

Your fridge is probably bigger and working harder than mine, but I get by with just the 100ah LiFePO4. I can go 48 hours with no charging: Running the fridge near freezing, phone chargers, the radio occasionally, and LED lights.

[jkidd]

Switching to Lithium would probably be a good idea but, That still means you have to be able to put back the amps you have used in order to be ready for the next night. I have 2 130 watt folding panels that I use for over landing. They are
made by Overland Solar out of Boise Idaho and the model is Bugout 130. They fold up to 8" X 23" X 2.5". Deployed they are 5.5' X 23" X 1/4" and have d rings around the edges so they can be hung off the side of the boat or on top or on the Bimini or on top of the dingy. If aimed towards the sun they can put back 10 amps per panel in good conditions. They are not cheap $630 per panel they will give you the ability to move them to get the best sun and store them in a small space.

[Marco Flamingo]

I've had good luck with flexible panels, which is why I like them. I have one on my CD that is attached with SNADS and a little spacer to provide ventilation under the panels. If you don't haul toys on top, there is plenty of room for flexible panels and they can be much less intrusive than flat panels. I've towed the boat at +65mph, so I know that the panel will stay in place while boating.

I just bought a 120 amp LiFePO4 to give me 100A usable. Same physical size as a Group 27 lead acid at less than half the weight. I've no freezer (I consider that decadent, as I wear a hair shirt when onboard the Limpet.)

Mark

[kennharriet]

Just an update where I landed after input from others. The objective is to go at least 48 hrs without charging with the Honda 90 outboard. I am adding one additional Vmax 85 ah AGM so will have three 85 ah AGMs in parallel for house batteries and another as the start battery, with a Yadina Controller 100 Combiner. This will provide 255 ah or about 128 useable ah with a 50% drawdown. Certainly a down side is the weight of four AGMs.

I did get advice from a couple sources to avoid use of Lithium batteries, especially with the charge coming from a Honda 90 outboard. One of those sources was an ABYC certified marine electrical engineer and the other was the Smart Shore Marine Tech Support who sell the Yadina Combiner. I don’t completely understand the reasoning as it seems several are taking advantage of the benefits of Lithium. For now I’ll stick with the AGMs because I have them but would sure like to learn more about lithiums. Ken

[Captain Starbucks]

Can you please share what the Yandina tech told you? 3 days ago, one of their techs told me to go lithium with their Combiner 100L. I'm planning on replacing my Blue Seas ACR and lead acid house battery with a 100L and 100AH LiFePo4 this fall.

[WCF]

Just for the record: I ignored any discussion of your outboard's charging ability as your goal was power without charging. I don't have any stake in this, but, If you have an older outboard with a relatively little charging ability, I can see an argument for just adding more AGM.

The formula I have been using (Obviously not right for everyone) for an OB that makes around 40A maximum is:

- Smallest possible (G24) flooded start battery that meets OB mfg's requirements
- 20A DC to DC charger with a manual switch (only charge when OB is running at higher RPMs and start battery is fully charged, only charge above freezing)
- Inexpensive LiFe4PO house battery as mentioned
- Shunt and monitor on house battery to keep track of SOC and loads

[kennharriet]

Captain Starbuck and WCF: Jim Usery is the name of the tech who advised me against using Lithium batteries. In my case with a new Honda BF 90 that puts out 40-44 amps it would be detrimental to the outboard starter at some point and not adequately charge the lithium battery unless consistently running 4,500-5,000 rpm. He said he spends alot of time consulting with frustrated folks on the bass pro circuit running lithium batteries. He said the Yandina Combiner 100L was designed for lithium batteries charged by a larger motor putting out much higher amperage than a Honda 90.
I got the same advice from an electrical engineer who specializes in marine electrical systems. He is the one who suggested the best way in my case to go 48hrs with out charging is to add an AGM in parallel to increase the useable amp hours. His name is Mac Fraley @ BoatDoctorNW@gmail.com
Here is a cut and paste from his response to me:
Hi Ken,
“Thanks for reaching out. Sorry to hear you had to cut your trip short. You really only have one option and that's to add more AGM batteries to your house bank. Because you are charging off of the outboard's alternator, which is not externally regulated, you can't go lithium. If you did put a lithium house bank in, you run a very good chance of overworking the alternator and potentially destroying it.

The quickest and most cost effective route would be to add an AGM battery in parallel to the battery that's already on the house bank. Now, if that house battery bank is more than a few years old with a bunch of cycles on it, you may consider replacing the existing battery as well. Although if it's in good condition, it's fine to add the same brand/model in parallel for the additional battery.

Lastly, solar will help the cause, but I think you'll see enough of an improvement on your battery life with the additional battery that you don't need to worry about it.”

I’m just a retired wildland fire guy enjoying retirement trying to figure out how to spend more time at anchor. I do enjoy learning all I can about electrical systems. Thanks for the input and discussion. Ken

[WCF]

I think this response presupposes you would just be adding lithium with an ACR or switch rather than DC-DC charging.

My setup does have a problem, and I appreciate that this consultant's response made me dig a bit more: I see a consensus on other boat and non-marine forums that a 20A DC-DC may be a little too much for long term reliability of a 40A alternator.

I'll be setting the current-limiting feature of my DC-DC charger and will only pull 10A to my house battery.

I'll report back when I burn up my alternator for another mea culpa.

[kennharriet]

Meant to say detrimental to outboard alternator in previous post. Not starter.

[colbysmith]

[Marco Flamingo]

The first one I bought was Unisolar. Very flexible, maybe too flexible. But I remember the name because I was so impressed with output that I bought a second. The one on my CD16 is less flexible, which actually makes it easier to attatch. It is shown in my photo album, but I don't remember the brand. I generally gamble by purchasing cheapo generic.