I run the Costco Interstate group 27 deep cycle on my 55lbs 12V Minn Kota. It has been great for last 1.5 years and saved me well over $88 in gas and motor hours. My record is 5 hours of trolling at 50% throttle and it still wasn't dead.

I can't justify the Optima price. Roll with the Interstates. I charge with the Cabelas Pro Mariner 8 amp dual bank charger. Costco will take the batteries back if you are displeased.

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Based on what I saw on the Interstate site, the group 27s are only 4 lbs more each or 8 lbs total. I would go group 27. There are some temperature advantages in very cold weather for some battery types. I don’t think I’d go Blue top since they seem to be Dual Purpose not deep cycle. I would consider AGM deep cycles though.

 

Thanks for your replies. I found a pair of VMAX MR127-100 12V 100AH AGM Deep Cycle Group 27 batteries on Amazon for just under $500. Have any of you used these and if so, how well do they perform?
DC

 

These are all really tough questions to answer definitively. Tons of grey area. The Interstate and VMAX are both batteries with very good reputations.

For an electric trolling motor, it's all about battery capacity: the amp hour rating. I believe the group 27 Interstate is 96 Ah, the VMAX 100Ah: basically the same size. A Terrova draws 56 amps @ 24V under full load but lots of folks figure out ways to avoid running anywhere near full load. Regardless, I would never consider anything smaller than a group 27 for an electric trolling motor, and even group 27s are going to be quite limited in the number of hours you can run at full load (56 Amps with a 96 Ah battery is a totally dead battery in only an hour and a half if running at full load).

Costco reputation is to be pretty darn forgiving on warranties, so a factor worth considering. Deep discharge applications are really tough on batteries, so warranty tends to be much shorter on deep cycle batteries than start batteries.

As far as AGM vs. flooded, AGMs are better in confined spaces since they don't breathe into the space until they overheat, so they tend not to corrode things around them. And AGMs can be mounted at angles, unlike flooded cell. Both flooded cell and AGM have the same USCG and ABYC ventilation requirements since both can, and do, ventilate explosive hydrogen into the atmosphere: be very careful about putting any battery in a confined box without adequate ventilation. Biggest mistake I see regularly is folks buying AGMs and mounting them in an enclosed space: this is a real (not just theoretical) explosion hazard.

The faster you can get those batteries on a charger after using them, the longer they will last. I'd spend my money first on a good charger (ProMariner 20 is good choice), and if you will be away from power, buy a nice Honda generator. If you buy great quality batteries, but run them down and let them sit for any time with a large discharge, that is what kills your batteries. So having a plan to get them on a sufficiently sized quality charger ASAP will be the best thing you can do to ensure your batteries will last.

 

Thanks!
Since the price difference between the Costco Interstate 27s and the VMAX AGM 27s is about $300, I guess I'll just go with the Costco units. Also can be obtained locally. My mounting location is on the bow, on either side, right in front of the windshield,in MinnKota Powercenter boxes. These are, of course. well ventilated. I'm using #10-guage marine wire, run doubled between the two batteries, negative to positive, because it's a longer run (12'), and single from the MinnKota plug to the remaining + -- terminal on each battery (6'). I don't use this boat in the ocean, so don't tend to take any water over the bow. I always charge as soon as I return home after a day out. I took your advice, Positize, from a previous post, on the minimum charger capacity of 10 amps per bank.
Great responses, as always. THANKS!
DC

These are all really tough questions to answer definitively. Tons of grey area. The Interstate and VMAX are both batteries with very good reputations.

For an electric trolling motor, it's all about battery capacity: the amp hour rating. I believe the group 27 Interstate is 96 Ah, the VMAX 100Ah: basically the same size.

Costco reputation is to be pretty darn forgiving on warranties, so a factor worth considering. Deep discharge applications are really tough on batteries, so warranty tends to be much shorter on deep cycle batteries than start batteries.

As far as AGM vs. flooded, AGMs are better in confined spaces since they don't breathe into the space until they overheat, so they tend not to corrode things around them. And AGMs can be mounted at angles, unlike flooded cell. Both flooded cell and AGM have the same USCG and ABYC ventilation requirements since both can, and do, ventilate explosive hydrogen into the atmosphere: be very careful about putting any battery in a confined box without adequate ventilation. Biggest mistake I see regularly is folks buying AGMs and mounting them in an enclosed space: this is a real (not just theoretical) explosion hazard.

 

Be careful on the 10 awg: only good for 30 amps. Yes you can double up the 10 awg to double the current capacity, but you'll need to do it everywhere. And when I double up, I always derate by 20% because it is so difficult in marine applications to get equal flow (due to inevitable corrosion), so that doubled 10 awg would be good for 48A, not 60A. If you decide not to double up your wires, you'll need at least 6 awg for the 56A Terrova (assuming you buy 90 degree C rated THHN wire, or better). Keep in mind the current is the same in all the loop (Kirchoff's current law), so there will be up to 60 amps everywhere.

And if you are worried about voltage loss in that 12 feet (about .6 volts in 12 feet), then bump up to 4 AWG (about .4 volts loss in 12'). I don't expect that .6 volts (out of 24V total) will be a big problem for the Terrova, but have not looked at their specs. This is the beauty of 24V circuits: it cuts the current in half (over 12V), so you get half the voltage loss, but then you also reduce the percentage loss in the wire another 50%, so the percentage voltage loss is 25% (compared to 12V): in general I don't worry about longer runs in 24V circuits (which is why virtually all DC commercial controls are 24V, not 12V).

Highly recommend you run in conduit, and be absolutely sure to include a 60 Amp breaker since big wire makes very hot connections (= fire hazard) if it shorts out.

 

At a minimum the group 27 is what you need. Another battery option that lasted me almost 10 years on 2 are Everstart deep cycles ones sold at Walmart. The first one lasted 7 years and I sold the boat 3 years into the last half. I never charged it, removed from the boat in the winter, added water or did any of the things I know I should & still didn't do. It was parked every fall & always started the boat which always sat outside. Like clock work the next spring it had enough voltage to go.

I took out the (2nd) boat battery since I sold the boat, and the last year it's been charged by solar & runs my mighty mule gate opener. It's outside & has been in the elements all winter. I had to use a home charger as the solar couldn't keep up. Again I absolutely abused and neglected these and they won't die. I think they (Walmart) also so this in a group 29 which provides you additional boost of RC & CCA.

One thing Positize didn't mention and this is also extremely important. Try to limit running them down to a deep discharge state. If you use 20 - 30 percent of the battery capacity and it's recharged, compared to running and using 75 percent of the battery before it's recharged. The deeper the discharge, the harder it is on the battery and a deep discharge overall will eat away at its overall service life - performance. there are also limits to how many times there discharged.

To help mitigate the deep discharge, one option is If you have a larger battery with additional RC capacity. This will help if you have electronics that pull a moderate amount. In essence a continuous 30 amp draw for 2 hours on a group 24 which has for example a 120 RC capacity will affect it's overall battery condition way more when you compare this to a group 31 with a 210 RC capacity with the same 30 amp draw for 2 hours. The deep discharge on the bigger battery will not be as severe simply because it has more RC capacity & can absorb this amp pull. .

In essence the goal is you don't want to be at the bottom of the voltage range with any battery if possible. The bigger the battery helps with negate this simply because it has more storage-capacity. The same goes for the daily charging after each use.

The blue top is the wrong battery. I would stick with the wet cell ones or buy any agm from interstate or others. There all really good & ive seen on average you can get up to 7 years on a wet or 10 on a agm or even more.

 

Thanks!
I ended up going with the group 27 Deep Cycle flooded batteries that Les Scwab sells (Johnson Controls). They had the best Ah rating of all the ones I was considering (120 Ah), and their service at the store here, in my experience, is the best.
I rarely use the Terrova at full-power, and even then, only briefly. If I need to go faster without the big motor running I use my 9.9 HP Yamaha kicker. I usually use the Terrova in "Spot Lock" mode, to stay in one place, and at low speed to get close to the shore in a lake while maintaining enough control to keep the hull from contacting the rocky bank.
Positize did mention that deeply discharging batteries will shorten their life, and I'd heard that elsewhere. Thanks for underlining that.
BTW, Is the "RC" rating the same as the Ah rating? I assume RC stands for reserve capacity? I never saw any group 24 batteries rated as high as 120 Ah.
I finished the system and it is working well. Thanks to all who contributed here. Terrific resource.
DC

 

The RC is a measurement of service life before the battery is drained. The higher the number, the better. For you the group 27 is good enough.

This is only an example & reference only as I'm not picking any brand and I'm not using real numbers in any of this.

Group 24 has a RC of 105
Group 27 has a RC of 150
Group 29 has a RC of 175
Group 31 has a RC of 250

You take the RC and amp draw. The higher the RC, the longer the battery will last before it is discharged beyond its use

30 amps draw (again fake times & equations).

Group 24 - will last 30 minutes
Group 27 will last 1 hour
Group 29 will last 1.5 hours
Group 31 will last 2 hours


Obviously no one uses 30 amps forever, as you mentioned in a trolling motor capacity from a fully charged batter to when it's discharged beyond use. The faster you go. The more amp you use. The slower you go, the less amps you use. The Larger battery with more RC means it will last longer at stated draw for a specific amount of time. This is the only measurement I really pay attention to when you talking about a trolling motor situation or when I'm curious as to how long it will last.

I'm not sure how to or what the formula is needed to convert the AH formula & truthfully it does not matter in your application. The group 27 is going to be just fine for what need. If possible in the off season, get them batteries inside & set them on a wood block. Don't store them on bare concrete, keep them from freezing & buy some of the battery corrosion prohibitor spray from Napa auto.

If you spray the battery terminals with this red tacky stuff that will help stop terminal & post corrosion that will be more prevalent as the batteries age.

 

I have a Minn Kota MK-230PC (2 Bank) Precision On-Board Charger and 2 V-Max 100Ah Batt . I have run 12 hrs steady trolling for Kokanee . Still power to spare wen I quit . Batt's recharge in less than 8 hrs or less with the Honda 2k . $600 total for Batt's and charger . I know many guys that go cheap on batt's and can't make it thru a full day of fishing on Odell and their batt's don't get a full recharge overnight . I've been down the cheap road and can tell you it's cost less in the long run to pay for the good stuff up front . Kind of like 2' Itish .

 

Thanks for the info on your experience with the VMAX batteries.
DC

 

I'll give my two cents since I tend to go overboard on minor details.

I was looking for the best batteries at 50lbs. Trying to keep weight low as possible for my 24v minn kota 80#. Reserve capacity being the most important number for a trolling motor.

#1 was an Interstate (Not Costco, they are different.) SRM27. 50lbs, 160 minutes reserve. I weighed mine when I got them home and they were 50.3lbs each. So far they are working great.

#2 was Deka Marine Master Group 27. 53lbs, 175 minutes reserve. Weighed them and they were actually around 55lbs.

#3 was Trojan SCS150. 50lbs, 150 minutes reserve. I feel like they are the most robust batteries, but cost and the smaller reserve made me pass.

Just my input. I weighed various batteries. I had Interstate SRM29's that were 60lbs a piece and would let me fish 2 FULL days on a charge. So overall I shaved about 20lbs and still can fish a full day to day and a half. Maximum power/amp draw is the same.

 

Nice! Your evaluation of the "strength-to-weight" ratio is interesting. So, is Costco selling a downgraded version of the Interstate group 27s?
DC

 

One sleazy thing to look for when you are buying batteries is that some companies play games with their RC rating.

It is 'generally' defined that RC means the number of minutes a battery will run with a 25A load until it reaches 10.5 volts. That is the RC25 rating of a battery, shortened to RC. But I have seen companies that spec RC using 20A load instead (an RC20 rating), which will inflate the number of minutes, making the battery look better than it really is. And I have seen examples of voltages less than 10.5 used. All sleazy specsmanship.

Due to Puekert's law, the Amp Hours is really a better measure of the way most of us use our marine batteries. The Ah is the number of amps a battery can provide constantly for 20 hours until it reaches 10.5 volts - and I have NOT yet seen people mess with Ah numbers to achieve artificially raised results.

My reasoning is simple why Ah is a better comparison spec than RC. Say we have a fairly run-of-the-mill group 24 battery with a 100Ah rating: that means it will provide 5 amps continuously for 20 hours. But the RC of that same battery answers the question: how long will it last at 25A load. And almost NONE of us have continuous 25A loads, so it is not a practical measurement in terms of most real use. A 5A continuous load is more in the ballpark for most of us than a 25A load - and so is easier to practically apply. Ah and RC are highly interrelated, but due to Peukert's law, if you don't understand exponential math, it is very difficult to intuitively correlate the two. In the above example with a 100Ah battery, if you run it at 25A continuously (the amperage used for RC), that 100 Ah would NOT mean you could run that battery for 4 hours - due to Peukert's law, it would be substantially less time than that - say around 2 hours. I do exponential conversions daily for my work, and still have to use a spreadsheet.

So bottom line is you are better off comparing Ah than RC of batteries because
1) There are some sleazy RC specs out there
2) Ah is a better measure of how most of us use our batteries anyhow
3) Batteries that have no Ah spec tend to not actually be deep cycle batteries - so having an Ah number is an indicator you are really looking at a deep cycle battery. You'll find RC specs for start batteries, but will rarely (never?) find Ah for start batteries.

BTW - the weight of a battery is a very good first order approximation of its load rating. That simple. Heavier lead acid batteries last longer than lighter ones. Especially true for deep cycle batteries since they are all of very similar construction. Start batteries have varying constructions, but deep cycles are mostly the same technology, so there is just no way to get more load rating with (substantially) lighter lead-acid batteries. So in the end, you could just compare the weight of deep cycle batteries and have a good idea which one will provide more load rating - 10% load rating differences across brands are not that significant, but lifetime longevity and warranty are probably more important when comparing equal weight batteries across brands.