New Battery Recommendations

[Michael Hoff]

I have a 26C a Westerbeke 55A Alternator (new last year) and two Group 27 Deep Cycle 600 CCA flooded batteries, one installed in 2019, the other in 2023. Each battery esides in its own battery box and they are connected in parallel. I use the batteries interchangeably for starting and house use.  

The boat lives on a mooring without a solar panel. 

 

I day sail about 30+ times a year and might overnight once a season for one night if I can convince my wife. My electrical budget is modest: VHF, Chartplotter, Depth Sounder, Autopilot, automatic bilge pump, stereo and seldom used fresh water pump and shower sump pump. Since I mostly daysail I seldom use running lights, anchor lights, or interior lights. 

 

The boat has a Westerbeke 21. I usually motor less than an hour a day but occasionally motor up to about 3 hours if I have to. My power switch can choose #1, #2 or Both. I alternate between #1 and #2 on a daily basis. If I motor for a long period I sometimes choose Both. When motoring the Voltmeter on the panel maxes out at around 13 Volts @ 1900 rpm. Higher RPMs doesn’t move the meter. The meter on the distribution panel consistently reads about 11 Volts for both batteries and has for years – never 12 or more. Even though the boat starts reliably, it’s time to replace the 2019 and maybe both Group 27 Deep Cycle 600 CCA flooded batteries. 

 

Finally, here are my questions:

1.    Is the Westerbeke 55A alternator adequate to charge Deep Cycle 600 CCA flooded batteries, if I motor about 3 hours very occasionally and add a solar panel?

2.    Would I maintain a better state of charge with 400 CCA batteries – the minimum suggested by Westerbeke for cold climates?

3.    If I stay with Deep Cycle 600 CCA flooded batteries should I replace both or can I keep the 2023 battery? 

4.    Can I switch to AGM batteries without upgrading the alternator and adding additional equipment? 

5.    What batteries do you recommend for my application?

6.    What rating solar charger should I add? Any recommendations? 

Thanks in advance.

 

Mike Hoff

26C Evelyn May

Lake Tashmoo, Martha’s Vineyard

[Joe Valinoti]

Mike:  From what you said, I suspect that your batteries are not really in parallel due to having the battery switch you described.  However, you do have that ability in the “Both” position.

 

Joe Valinoti
S/V iL Gatto NS30U #221
Sea Harbour YC
Oriental, NC USA

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[Bob Gehrman]

Mike - 

Your questions are all good ones, with a lot of answers. I suggest a small book by John C. Payne, “Understanding Boat Batteries and Battery Charging” that will help you make a lot of decisions based on your specific needs and circumstances. 

The one aspect of the book given its age of 2003 is that PV charging is now much more widely available, cheap, and easy to install. Renogy is a manufacturer that makes pretty solid and economical products that I’ve had success with and has good information on their website. Most of your charging needs could probably be handled with a small solar array and a simple solar charge controller.

I installed (2) 100 watt panels and 30A controller for $250 last year while my boat was on the hard and it kept my 4 AGM batteries charged throughout the winter. I plan to use it every winter since I am remote from the boat and not worry about depleting the batteries for any reason.

Best of luck!

Bob Gehrman

NS36 #52 “Fortunate”

Greenwich Bay, Rhode Island

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[Ernie Abugov P/O NS22 o/b #56 "Moustaches"]

For what it's worth, on my NS 22 O/B, I had ONE Deka lead acid HOUSE battery that I also used to start the outboard. I would keep this battery topped up every winter (6 months on the hard) with a 5 watt solar trickle charger. Worked for years. NO charge controller needed. Two panels like what Bob is using (200 watts) will do the job with 4 batteries, in spades.

https://www.amazon.ca/Sunway-Solar-Maintainer-Powersports-Snowmobiles/dp/B07W97ZBXT/ref=sr_1_2_sspa?dib=eyJ2IjoiMSJ9.U7NQDN8cotL1TJr7FmlDKhoiwnUxdfPaMzVzY7Dg8U15IVRlfwnQ6Jl_Plf1015roKXkAv4tFVLsAV8vqvk2UM3hzyYJSC19iJRSZEE2t6X-KgmOkgYrCHeGpERBOGDNK-ZyI7osi3PToLhmQJsLZmrSf2g5LGbetn1aJb7wXz6ZbPt80ofbrpMODaAOqyEKJfZ70UfgbvZO25vdP0Ig5wMhYZMw6NVeGaZASjcHHY0u4qL0n9vt4hI2OjVFSsDyEMpaUSiue8M_WH2N0aA57TMG4JmU_NUZ_lB1mvnpHL0.zK_OoDbOVb8FVXqz1enShM7tsy5iepLQmgKF3q7UQ2o&dib_tag=se&hvadid=605194864446&hvdev=c&hvlocphy=9000932&hvnetw=g&hvqmt=e&hvrand=7348025882242589904&hvtargid=kwd-961000991474&hydadcr=10347_13533586&keywords=solar+trickle+charger+amazon&qid=1719319442&sr=8-2-spons&sp_csd=d2lkZ2V0TmFtZT1zcF9hdGY&psc=1

Ernie A. in Toronto

[Mark Powers La Reina 26C Vancouver, B.C.]

Mike,

Mike, I agree with Joe that what you have are two separate banks which can be combined when you put the switch to the Both position. In that setting it will be a parallel connection. When 2 12 volt batteries are hooked together in parallel the voltage stays the same but the amps hours of the two batteries are added to each other. If they are hooked together in series the amp hrs stay the same but the voltage doubles to 24 volts. 

Generally a battery will have two ratings: the Cold cranking amp (CCA) and a 20 hour amp rating given as amp hours. As long as you have batteries which have a high enough CCA to start the battery your next concern will be how many amp hours the batteries can deliver.  Sticking with a Deka battery as Ernie mention a quick search indicates a Deka DC27 Marine DeepCycle group 27 flooded battery is listed at 625 CCA and a 20 hour reserve of 90 amp hours.  

https://labatteries.com/product/00/dc27/Deka-DC27-Marine-Master-DeepCycle-Group-27-12-Volt-625-CCA180-RC

Recommended alternator sizing is the alternator should output approximately 25% of the battery capacity. The 20 group 27s have a combined capacity of 180 amp hours so the 55 amp alternator falls with in the recommended size. The charge acceptance rate of flooded lead acid, AGM and Gel batteries drops as the batteries reach about 70% full. At a 50% state of discharge a 90 amp hr battery might accept 20 or even 30 amps but by the time the battery is a 70% state of charge it might only take 10 amps and by 85% state of charge it might only take 5 amps.  What this means is it takes a long engine run time to fully charge those batteries. 

A solar panel or two would be a good addition to your system. Ideally you would like enough solar capacity to keep up with your daily needs. Unless you crank up the stern really high it is likely that your autopilot is the big draw on your system.  I have no idea how much it draws. You will want to look at the specs for it and multiply that by the daily usage to come up with daily amp hours. A rough guess would be that your total daily draw is in the 20 to 25 amps.

Probably starting to get to much detail here so I will try so stop myself. 

To keep your lead acid batteries happy you should not discharge them below 50% and you should try to bring them up to full charge as quickly and as often as you can. Solar is the best way to do that considering your usage. You can find charts that will show you how many amp hours or watts you can expect out of a solar panel in your area (maybe 15 to 20 amp hrs a day from  100 watt panel). If you are mostly day sailing you don't need to put back in the full daily draw because the panels will continue to work while you are away from the boat.  I will disagree with Ernie to the extent I think you should always have a controller for solar panels to protect the batteries. Spend the bit extra and get a MPPT style as opposed to a PMW. Try to find a location for mounting that gets the least amount of shade. 

Based on past experience it appears the two group 27 batteries meet your electrical needs.  You should replace both batteries. The banks are separate so you can get away with using batteries of different age but because you combine them at times it is better if they are the same age. To keep it simple I would suggest you stick with two group 27 flooded lead acid deep cycle. Just make sure you keep the water level topped up using distilled water. You can upgrade to AGM batteries without any changes. AGM and wet cells have to same charging requirements. If you go to GEL batteries you will need to change the charging rates.   

Two benefits of AGMs are a slightly faster charging rate and no off gassing during charging. If off gassing is not a concern I suspect you would be better off with flooded wet cells. I have AGMs because my batteries are under the quarter berths and I don't want the off gassing. If the batteries were in a back locker I would likely use flooded. I guess a third benefit of AGM batteries is that you don't have to top up the water. You do have to be careful with AGMs, most manufactures of AGMs tell you not to do a conditioning charge. Conditioning charges are over 15 volts an can boil the fluid out an an AGM.

You need to buy a digital multi meter and spend a little time learning how to use it. The readings you are getting from your current (pun intended) meters are wrong. I have added a chart showing voltage for lead acid batteries at various states of charge. If you search the internet you will find many such charts with slightly different numbers but generally a 12 volt battery at 11 volts is basically empty. You really don't want them to go below12 volts. Generally the charging voltage for lead acid batteries is 14.4 volts. For  Gel batteries it is lower. A fully charge and rested 12 battery will normally give 12.8 volts. You will want to check at the battery terminals. 

Your questions:

1: yes the 55 amp alternator is big enough and a bigger one is likely wasted.

2: CCA amps will not change the battery state of charge and going to 400 would not be a good move. If the batteries are a bit weak they may not put out enough to start the motor. 600+ CCA gives you a cushion.

3: Stay with the group 27 600 CCA deep cycle batteries. It is better to have the batteries both from the same manufacturing batch but at a minimum it they should be manufactured with 6 months of each other. If the budget does not allow replacing both you can have different ages because you generally don't combine them. 

4: AGM. You can with to AGM with no changes. I am not sure you will get enough benefit to justify the extra cost.  See my comments above.

5: Do you mean chemistry or maker? I suggest a good quality flooded deep cycle group 27. You won't need to change cables or battery tie downs. Good AGMs are expensive now and you might have to change the cable ends to connect to the battery posts. 

6: Very difficult to answer. Decent panels with combined capacity of 25 to 200 watt with 75 to 150 watts being your sweet spot between capacity, cost and size. Definitely MPPT controller for each panel.

Hope that helps.

Sorry no time to proof read.

Mark Powers

[Daniel Weinstein]

Mike-

You don't mention WHY you feel it is time to replace the batteries.  Are they not holding a charge or not providing enough amp-hours (voltage is dropping much fast than it used to)?   Most decent, properly maintained and not-abused flooded deep cycle batteries have lasted me 6 or more years, and my usage pattern is reasonably similar to yours.  Maybe it is worth testing them.  Lots of good info from others about replacement, so the only thought I'll add on that is when I last replaced my batteries, I decided to stay with flooded, since I found that all the solar charge regulators I've used tend to over charge slightly, causing me to add water about twice a season.  On a sealed or AGM battery, that can't be done and over time caused premature failure on the last one I owned.  One other item- at least once in the off season, you should put your batteries on a charger that has a desulfation cycle, which is a specific, short-duration overcharge cycle to remove sulfation.  My charger does it once every 45 days if I leave it connected (I choose not to).

Dan Weinstein
Look Farther, 30C #205
East Greenwich RI

[Michael Hoff]

Thanks to everyone for your responses.

First, to answer Dan’s question, I started the process of replacing the batteries because I was frequently getting a lost data message and losing my depthfinder. A Raytheon specialist went out to the boat and advised that the problem was probably caused by currency fluctuations, tested the batteries and found that they were both reading under 12V. Also, two batteries were installed in 2019, one had to be replaced in 2023, and the survivor has sustained 5 seasons of abuse (infrequent sustained use of the motor/alternator, no solar on the mooring). Even though the existing batteries reliably start the Westerbeke, the bottom line is better safe than sorry and time sailing is more important than money. Otherwise, who would own a boat?

The batteries are in the lazarette on the starboard side, too deep for me to replace myself without sustaining imminent bodily harm so a service tech will be replacing both today. I requested deep cycle but I’m getting two Dual Purpose flooded 80 amp, 650 CCA batteries because that’s what they’ve got. The Westerbeke 55A alternator should be able to help charge them when motoring, particularly since I typically alternate use of the batteries daily. Since my realistic dreams are limited to one night out in Tarpaulin Cove or Cuttyhunk a season, the Dual Purpose rather than Deep Cycle should be adequate and I’ll be satisfied to get 5 years out of them. To accomplish that I’m going to add a 75 - 150 watt solar panel and a MPPT controller on the mooring. 

Thanks one again. 

Mike Hoff

Evelyn May, 26C

Lake Tashmoo, Martha’s Vineyard

[Sprio]

OR, you go the other route with lifePo4 (lithium - supplied with internal BMS. drop-in replacement for lead acid). We all know what Li-ion meant for our portable power tools. The costs are about the same as high quality lead acid batteries nowadays. They do withstand discharging as low as 0%, and they will last 10 times longer (on paper). There are some drawbacks, but I'm just adding this suggestion to simplify your decision, :-) lol. Good luck!

www.rododopower.com is one of many suppliers.

mark h

n36#25

netherlands, europe

Op dinsdag 25 juni 2024 om 19:47:49 UTC+2 schreef Mark Powers La Reina 26C Vancouver, B.C.:

[Mark Powers La Reina 26C Vancouver, B.C.]

Mark, now you are stirring the pot. Going to lithium carries certain advantages however it is likely Michael would have to install an external regulator for the alternator.

Generally lithium like to operate between 10% and 90% state of charge. They are content living in a state of partial discharge and are lighter than lead acid. Some lithium batteries can’t take a high discharge rate so the manufacturers don’t recommend using them for engine starting. A person going with lithium batteries has to make sure the ones they buy will fit the purpose.

Mark Powers

[Sprio]

I do admit that I was just stirring the pot but i also think that it's good to know that there is an alternative for lead acid batteries that, on paper, should fit the needs of boaters and lasts a lot longer.

in case of mr Hoff, he actually could consider LifePo4 considering...

- He does not change the standard regulator on his alternator. He can't overcharge the lithium batteries because the standard regulators voltage is just too low. He won't fry his alternator because the standard regulator doesn't make the alternator work very hard. The standard regulator doesn't have any charging-stages, which is a good thing considering lifepo4 batteries. "Downside" is, that he won't be able to top up his lithium batteries with the alternator but I thought that he told us that he hasn't been topping up his lead acid batteries either. So, the downside might actually be a good thing, considering...

- He adds (sufficient) solar and an mppt charger that handles lifepo4. He was planning on adding solar anyway, so there are no extra costs here.

The real downside is, that the BMS in these drop-in lifepo4 units, shuts the battery off when it kicks in for protection. This is bad, especially when charging with the alternator. Over-discharging the batteries will also trigger the BMS to shut the unit off to protect it. There are ways to make sure the engine can be started on a remote location when this happens. One of those portable emergency start devices should do the trick.
I would also consider buying a shorepower charger and use it to truly top of the lifepo's every 6 months or so. That way the BMS can equalize cells properly.

Iit is true that lead acid battery are more KISS than lifepo4's but there are many advantages to consider lithium.

mark h

n36#25

netherlands

Op zaterdag 29 juni 2024 om 01:07:56 UTC+2 schreef Mark Powers La Reina 26C Vancouver, B.C.:

[Mark Powers La Reina 26C Vancouver, B.C.]

I agree there are many advantages to be had with lithium batteries. What is interesting is that at our last rendezvous the consensus was that lead acid batteries are great if you have enough solar panels to keep them fully charged on a regular basis. 

Here is a link to the Marine How to site.  https://marinehowto.com/category/electrical/batteries/

Rod "RC" Collins who creates the articles on the sites is of the opinion (speaking for customer experience) is that a small body alternator can be burnt out try to charge a lithium battery bank. He also states that the charging requirements for lithium are close to that of lead acid but not close enough and that you should have a regulator set up for lithium. His articles on "Easy LiFePo4 Conversion"  and "Drop in LiFePo4 Batteries - Be An Educated Consumer" are worthwhile reading. The second article starts out with the heading "Lead Is Dead (almost)".

Mark Powers