House Battery Upgrade Help

[gouldx]

Hi all—

I'm wanting to upgrade the house battery bank on my Yamaha 30 (v-berth engine), but despite my research I'm still pretty confused and could use some guidance.

Currently, I have a West Marine group 27 flooded starter battery and a Duracell (Batteries+) group 27 flooded house battery. 80ah, I believe. They're charged most of the time by shore power via a ProNautic 12-20p, and 200w of solar running through a Victron 100/20 MPPT. I'm unsure of the alternator's specs, but I'm guessing it's original to the boat and the Yanmar YSM12 engine. We don't usually have a large energy expense, and we can typically stay out for a couple nights without issue, as long as the sun cooperates and we turn the fridge off at night, but I'd like to have more capacity to work with for longer trips that involve more sailing and less motoring.

Here are the issues that have me stumped right now:

1. Having everything located up in the v-berth area makes it difficult to place larger/more batteries anywhere near the chargers, so I'll probably need to find something low-profile and/or sealed, so it can go in the limited space under the settees. I measured, and I can just fit two group 31 batteries on their sides, but I haven't found a non-sealed battery that fits the space.

2. I was thinking AGM, but then I started reading on here that I probably don't have the proper charging system to support the needs of AGM, and that my setup could be detrimental for the longevity and/or safety of those batteries. Am I correct about this, given the equipment listed above?

3. Placing batteries half a boat away from the charging components has me questioning cable sizes and prices. If I already have a dedicated starter battery and a portable backup jump-start battery, do I really need to account for the potential draw of the starter when I size the cables?

Is there something else I'm not thinking of? Probably! I'll take whatever advice I can get, though.

Thanks in advance.

Collin

 

[Tally Ho]

No experience with your boat, but when I wanted to upgrade the batts on on O’Day 322, I went with a pair of Duracell 6-volt Golf cart batteries. They are 215 ah batteries, @ 6 volts..so 215 ah @ 22 volts when wired in series. I have spent a few consecutive nights on the hook, with my fridge on, and not had a problem. And I don’t have a start battery or solar…


As info, after these were installed, I added a fuse to the positive terminal.

Mine are located in a settee, which is vented. I have not had any issues with the locstion.

I understand your Yamaha is laid out very differently…and I would want to keep the batteries near the engine, charger and solar MPPT charger. I would be looking at the adjacent settees, or other lockers in or near the bow.

Just out of curiosity, where is the distribution panel?

Greg

 

[Scott T-Bird]

I'm not understanding everything you are saying. What is a v-berth engine? Is your engine actually at the bow? I've never even heard of anything like that. How is it that you have a dedicated start battery? What is the switching arrangement? Your 80 ah house battery is very small. No wonder you want to increase the capacity. That is virtually nothing for a weekend trip.

Unless you want to revamp your entire system, an AGM house bank won't be helpful. For that matter, AGM batteries are still very expensive and I believe the current thinking is that LiFePo4 is now the preferred option for an upgraded system ... but you still need to revamp everything. There is soooo much to consider that this brief response can't possibly summarize the arguments. Do your best to read everything you can about the pros/cons of AGM vs lithium if you are interested in those options. Personally, I'm sold on my next upgrade will be to lithium and definitely not AGM.

Your battery cables are most critical (based on sizing) between the start battery and the engine. The cables from charging sources to the batteries are typically less size in my experience. Still, the closer the better. I don't understand why you would have difficulty locating the charger near the batts if you can figure out a better space to put the charger. I'm not really understanding the battery compartment location. Isn't it really unusual to locate batteries up in the v-berth? That's pretty poor from a weight balance perspective. My batteries are mid-ships (under stbd settee), which even seems pretty far forward to me, but maybe a good location afterall.

FLA golf cart batts may be your best option. I would be looking for about 200 ah total, which gives you just 100 ah available capacity (50% max discharge).

 

[gouldx]

I appreciate the replies. It sounds like I should probably look into golf cart batteries, or possibly relocating the charging equipment to a more central location but here are some answers to your questions:

@Tally Ho good call on the terminal fuse--I was planning to do the same after reading some advice from MaineSail. The DC panel, by the way, is on the opposite end of the settees, toward the stern (see attached sketch).

@Scott T-Bird Yes, the engine is in the bow, as are the existing batteries (typical for Yamahas of this vintage). There are molded battery compartments under the v-berth on either side of the engine bay that are about maxed out right now, volume-wise, with the group 27s. The AC and solar chargers are both located in that forward area as well. Not my design, but it is what it is. I appreciate the input about cable sizing to/from the charger

When I say a dedicated starter battery, I simply mean that "battery 1" on my switch is solely used to start the engine. If the engine isn't running, I use battery 2 is for everything else, which isn't much, but yes, it could use an upgrade. I will look further into LiFePO4, but I had been (so far) put off by the price and my own misconception that AGMs would be more of a drop-in solution vs a system-wide refit.

I've been reading through this guide: Drop-In LiFePo4- Be an Educated Consumer , including the decision flow "Is Your Vessel a Good Match for Drop-In Batteries?". I don't have an inverter, windlass, thruster, etc., but it appears my ProNautic and Victron chargers support LiFePO4. If I'm reading things correctly, then I think that just leaves the alternator as an issue, but that opens up a whole new can of worms. So... golf cart?

 

[Ward H]

I agree with the golf cart battery idea. I have the same GC2 Duracell batteries that @Tally Ho has I think mine are 230 Ah and it's 12V, not 22V. Greg has a typo I believe.
I bought my Duracell GC2s from BatteriesPlus in 2018. This year they will be 7 yrs old. My battery monitor still gives them a 90% State Of Health. And they have twice been drained way to low. Once to 10v and once to 5v. each time they appear to have bounced back with no sign of damage or shortened life. We'll see how they make out this season.

@Scott T-Bird s idea of moving the charger is a good idea. Try for 2 GC2s and the charger midship. Keep the starting battery closer to the engine. Might a take a little bit of rewiring.

 

[dlochner]

If you are reading MaineSail's drop-in LFP article, then you know that drop-in is in name only. There is much to be considered and added to even a simple LFP system.

You didn't mention the type of sailing you do, long cruises, short cruises, or day sail.

AGMs don't like to be left in a partial state of charge for long periods. They make good starting batteries because a starting battery is not deeply discharged when starting, as a result they are quickly recharged. If I recall correctly Optima batteries can be placed in any position. A group 24 should be fine for starting.

The key to AGMs living a long life is frequent recharges to 100% SOC and not discharging below 50%. Unlike LFPs AGMs have a long recharge time, up to 5 to 6 hours from 50% to 100% SOC. If you are going to be off-grid for more than a week, this will be an issue, once a season will shorten the battery life a little, more than that and the cycle life will be shortened. Having adequate solar, i.e., enough to meet most or all of the daily power needs will mitigate the issue. Longer periods at low SOCs is more damaging than Long periods at a high SOC. Because you get to a dock with shore power, recharging to 100% SOC is not an issue, unless you go for extended cruises.

The 200 watts of solar will on average provide about 600 wh (50ah) of power a day. How much more do you need? The alternator on the engine is probably a 50a Hitachi that is internally regulated. It will do quite well at recharging the start battery and if you motor a long ways, it will help the house battery.

To get the most benefit from a LFP battery the off grid charging system will need to be beefed up. That can be a lot of expense. The 20a Pronautic is fine for at the dock charging because it can charge over night. There will also be additional expenses for fusing, alternator protection, and charging the start battery.

Moving the battery to the main cabin may be an option. The distance from the chargers to the batteries can be managed by increasing the wire size. At 20 amps, this shouldn't be much of an issue. Likewise the wire size from the battery to the battery switch would need to be increased. At 20 amps of charging capacity you are limited to a bank of about 200ah, that will give you a .1C charging rate. A group 31 has about 100ah. A group 31 AGM can handle at least .2C charging which your charger can provide.

 

[jssailem]

Not far north of us is a Battery supplier, Dyno. I have been using their batteries on my boat since 2015.
Specifically one they make the 30tmx. Fits in a group 27 sized space.

This one has given me the most bang for the buck.

Dyno Battery - Premium Quality Battery Manufacturing - Made in the USA

65 lbs. 12 volts 135 Amp Hrs $160-$175 a batttery. Pick up at the warehouse in Seattle or order them through Fisheries.

 

[gouldx]

Thanks all--this has been illuminating.

@Ward H Unfortunately, it appears the golf cart batteries will be too tall for my available spaces.

@dlochner Lots to think about here. I really appreciate the detail you've provided. To answer your question about the type of sailing we do, we are currently moored on a channel in the Columbia River, so a fair amount of motoring is inevitable, and we are not generally out more than a couple nights at a time. Our solar setup runs at a slight deficit when the fridge cycles on, but recovers the charge shortly after it cycles off again. I don't mind turning the fridge off at night, but it would be nice if we didn't have to, and if we felt more secure on cloudy days.

This project is primarily about getting prepped for longer cruises (let's say 4-5 nights without the guarantee of shore power), and a potential move back up to Puget Sound in the next couple years. We have relatively minimal energy needs (my budget spreadsheet is eluding me at the moment). LED lighting, basic depth/log, iPad/phone charging, and the aforementioned cold plate fridge. 200ah is about what I was targeting; I'm just challenged by available space/layout, and trying to understand my options.

@jssailem That's an intriguing package--I'll have to do some more measuring, but even one of those Dynos would be an improvement. Thanks for sharing.

 

[JBP-PA]

I would simply replace the house battery with a LFP drop-in. They cost the same as AGM and provide nearly twice the capacity. You already have a Victron charge controller and 200W of solar, use that to charge the LFP house bank. Keep the starter battery as lead acid and keep the alternator connected to the starter battery. If you ever need to charge one side from the other, you could pick up a DC-DC charger. You can get a Victron Orion 12V-12V 18A for a little over $100 dollars.

 

[Scott T-Bird]

I would simply replace the house battery with a LFP drop-in. They cost the same as AGM and provide nearly twice the capacity. You already have a Victron charge controller and 200W of solar, use that to charge the LFP house bank. Keep the starter battery as lead acid and keep the alternator connected to the starter battery. If you ever need to charge one side from the other, you could pick up a DC-DC charger. You can get a Victron Orion 12V-12V 18A for a little over $100 dollars.

Pretty good idea, I think. I'd like to see if there is a reason why this idea doesn't work. Just to share some comparison. Maine Sail seems to recommend Epoch lithium batteries. Going on their website I see a 12v / 120 ah model for $799. You can count on at least 75% discharge (I think full discharge is not a good idea), that gives you 90 ah capacity for $799.

Enersys is a well-regarded maker of AGM marine batteries sold as 3 different brands (identical batteries): Odyssey, Northstar & X2Power. I found X2Power is sold exclusively by BatteriesPlus and had the best price for 12v / 90 ah model for $450 now. Based on 50% max discharge, the useable capacity is 45 ah for $450.

So lithium is say $8.88 /ah and AGM is $10.00 / ah. That may be a small difference but when comparing the pros and cons for very similar-sized batteries (basically GRP 27) there is significant increase in capacity for far less weight. If I'm not mistaken, there are probably far more cycles in the lithium battery.

Another advantage is that if you decide in 2 years you want another lithium battery for greater capacity, there is no problem in just adding one. I believe that with LA batteries, you basically should buy both at the same time, so it may not be a good idea to simply add another AGM battery after using the first one for a few years. I'll acknowledge that may be an arguable point.

I agree that the height of golf cart 6v batteries can be a problem in the battery compartment. I had that issue in my Starwind and the modification to make space wasn't something I was willing to do. It sounds like @gouldx only has space for 2 Grp 27 batteries and if he wants to make a house bank with 2 batteries (leaving the start battery where it is), he would need to make space somewhere outside the v-berth area.

 

[gouldx]

@JBP-PA That’s a very intriguing idea that I hadn’t at all considered. Let me make sure I have it correct. To use a lithium battery in place of my current flooded house battery I would need to:

• Replace my current 1/2/All battery switch with separate switches for start & house banks, which would disconnect the alternator from the house bank to make sure it only feeds the start battery.
• Use the Victron MPPT only with the house bank.
• Optionally (seems like a good idea), use a DC-DC charger to allow the alternator to charge the house bank via the start battery if the solar isn’t keeping up on its own.
• I’m a little unsure how the shore power charger fits in. I’m assuming I would be unable to continue using it for both banks at once, given the difference in battery technology, so connect it to the start battery and use the DC-DC charger to get power to the house bank at the dock?

How did I do? Does this sound about right?

@Scott T-Bird You’re right about that $/ah advantage for LiFePO4. I was thinking lithium would require a larger investment in a holistic system revamp, but if JBP-PA’s idea could work, then lithium seems doable without too much fuss.

 

[Scott T-Bird]

@Scott T-Bird You’re right about that $/ah advantage for LiFePO4. I was thinking lithium would require a larger investment in a holistic system revamp, but if JBP-PA’s idea could work, then lithium seems doable without too much fuss.

Actually, I was looked a bit more carefully at the Epoch web site and the Grp 27 battery looks like the worst of the options. I don't know why it is so expensive but it is advertised as "dual purpose". It appears that you can buy 2 grp 24 batteries for the same $800 and can get almost double the capacity - 105 ah x 2 = 210 ah or about 150 ah available.

I was wondering why the 300 ah version also appeared to be a so much more economical - one 300 ah battery could replace the pair of 4D AGM batteries that I have. Something about that GRP 27 batt doesn't seem right. Perhaps it has something to do with that "cranking amps" capacity, which you won't need if you have a dedicated start battery. With our engines, we need very little cranking power anyway.

 

[JBP-PA]

@gouldx , that is close to what I would think would work. Everyone's needs are different though.
I wouldn't replace your existing 1/2/All switch, just get a second one. Think of one as your "house" switch and the other as your "motoring" switch. The house switch would almost always be set to the LFP house battery, and the motoring switch would almost always be set to the FLA starter battery. No more switching back and forth to start the motor.

Also I'd connect the shore charger to the house battery for the fridge and what not. Your starter battery should rarely need charging other than the alternator. In those rare cases it does, you can use the battery switches to connect the LFP house battery to the starter battery. A LFP battery will charge a lead acid battery (mostly, good enough to start your engine).

With regard to the DC-DC charger it depends on your fridge. If your 200W solar can keep up with your needs for your time frame, I might just skip the DC-DC charger until you decide you need it. You could get a manual Victron Orion 12/12 9A for $65. It's not automatic, you have to turn it on when you need it. If that would be too much hassle, the Bluetooth automatic programmable ones look like $160.

With regard to the LFP battery, top of the line batteries are nice, but you pay a premium and prices & features are still changing fairly rapidly. You can get a run of the mill battery from a well known brand like Li-Time for under $3/Ah that might only last 5 years instead of 10, but by that time battery tech. will have changed and you could buy 2 or 3 for the price of a top end battery. That said, if you want top of the line, get a replaceable BMS. LFP cells can (in theory) last a decade or more and tens of thousands of charge cycles, but the BMS is still just electronics. I know Custom Marine Products sells them.

Can you fit a group 31 case? It seems like group 31 cases offer the best price and features. Bluetooth charge monitoring is nice. You can also now get 140Ah or 150Ah batteries in a group 31 case, but these are not pervasive yet. If you can't fit a group 31, Li-Time does sell a 100Ah group 24 case and a 100Ah mini case.

 

[Tally Ho]

I agree with the golf cart battery idea. I have the same GC2 Duracell batteries that @Tally Ho has I think mine are 230 Ah and it's 12V, not 22V. Greg has a typo I believe.

Yup…. Should say @12 V.

Good catch.

Greg

 

[gouldx]

@JBP-PA When you say "replaceable BMS," are you talking about an external BMS, or something else? I'm leaning toward a couple of Epoch's group 24 105ah LFPs (they're offering a 10% discount, which puts them not too far off from the Li-Time models). They say they have an internal BMS... I guess I'm not sure of the difference. I looked on Custom Marine Products' site, but couldn't find what you mentioned.

Thanks again,

Collin

 

[JBP-PA]

You can get internal, replaceable BMS. They are expensive.

Lithium Marine Batteries For Boats - 2024 Lithium Battery Technology And Bluetooth To Phone App And Easily Removable BMS

 

[JBP-PA]

Those epoch group 24's look nice. Everything you need: self heating, blutooth, high density 105Ah in group 24 package. With a pair you get 200A continuous, 400A cranking for 10 seconds. All for $400 each, less than $4/Ah. Very nice.

 

[dlochner]

Just a word of caution, if anyone is going to do a LFP conversion on their own there is a lot of research that should be done first. There are multiple ways of installing LFP batteries and setting up the charging system, it just isn't as simple as drop in the new batteries and go sailing. Drop in LFP batteries are drop in in size only. LFP batteries have a few quirks that are quite unlike LA batteries.

There are several good sources for information about LFP installations. MaineSails site, MarineHowTo.com is one, Pacific Energy Systems has a number of informative videos on YouTube on electrical systems. MaineSail has a FB group on Drop-in LiFePO4 batteries. For battery reviews, Panbo.com is a good source.

If changing battery chemistry is on the table, the place to start is the kind of sailing the owner has in mind and the amount of power required for those loads. For many, plain old LA batteries are just fine and require little to no changes to the electrical system.

 

[Justin_NSA]

I went thru similar trials and tribulations when I was replacing my flooded batteries. Golf cart batts just wouldn't fit. I ended up with AGM batteries. My charging system has a setting for them. No more maintenance.

 

[gouldx]

@JBP-PA The Epochs seem like winners, and should fit on their sides under my settees. Thank you for taking the time to look everything up and help me verify!

@dlochner I appreciate the cautionary note. Standard LA batteries pose difficulties for my boat, due to the uncommon layout (forward engine) and lack of space for batteries that can't be laid on their sides. I've been doing a lot of reading and received some good advice on here, and it seems like the best plan is decoupling my start battery (LA) and new house bank (LFP looks like the way to go), so that the alternator is only connected to the start battery, and my existing, LFP-friendly solar and shore chargers are powering the house. I may add, per @JBP-PA's suggestion, a Victron DC-DC charger, if it proves necessary. We have pretty modest energy needs on the house side (no inverter, windlass, thruster, etc.), and I will be taking MaineSail's Drop-In LFP article's advice on fusing, but if you see any potential flaws or safety issues I'm all ears.

@Justin_NSA I was thinking AGM, originally, but since different battery tech would require changes to my system anyway, I've been convinced LFP is the way to go in my particular situation.

Thanks again, everybody!