I just got a 36 volt trolling motor and need to upgrade the batteries. While comparing the different ratings between Optima and West Marine  AGM batteries, I noticed the WM batteries had a far higher Amp Hour rating. Why is that? Same price range, same size, but about 25% more amp hours. Thanks

Are they both using the 20-hour rate?

 

And then there's weight.

 

This West Marine.East Penn Group 31 weighs 69 pounds.

www.westmarine.com/buy/west-marine--group-31-dual-purpose-agm-battery-105-amp-hours--15020258?recordNum=3

 

This Optima Group 31 weighs 61 pounds.

www.batteriesplus.com/productdetails/battery/marine-and-boat/deep-cycle/bci-group-31m/opt8052=161

 

One is $340 and one is $360.

 

Or, you can get a Group 31 Duracell AGM from BatteriesPlus for $240 minus 10% if you order online and pick it up. It's also made by East Penn/Deka and has a 105 AH 20-hr rating. They weight 67.5. I have 3 of them.

www.batteriesplus.com/productdetails/battery/marine-and-boat/deep-cycle/bci-group-31m/sli31dtmagmdc

 

Mine came with rope handles, but compare the nearly identical cases of the Duracell and the West Marine. The Duracell has a 30-mo warranty. West Marine is 18.

23 hours ago, mram10us said:

I just got a 36 volt trolling motor and need to upgrade the batteries. While comparing the different ratings between Optima and West Marine  AGM batteries, I noticed the WM batteries had a far higher Amp Hour rating. Why is that? Same price range, same size, but about 25% more amp hours. Thanks

Part numbers?

18 hours ago, Johnbt said:

Are they both using the 20-hour rate?

 

And then there's weight.

 

This West Marine.East Penn Group 31 weighs 69 pounds.

www.westmarine.com/buy/west-marine--group-31-dual-purpose-agm-battery-105-amp-hours--15020258?recordNum=3

 

This Optima Group 31 weighs 61 pounds.

www.batteriesplus.com/productdetails/battery/marine-and-boat/deep-cycle/bci-group-31m/opt8052=161

 

One is $340 and one is $360.

 

Or, you can get a Group 31 Duracell AGM from BatteriesPlus for $240 minus 10% if you order online and pick it up. It's also made by East Penn/Deka and has a 105 AH 20-hr rating. They weight 67.5. I have 3 of them.

www.batteriesplus.com/productdetails/battery/marine-and-boat/deep-cycle/bci-group-31m/sli31dtmagmdc

 

Mine came with rope handles, but compare the nearly identical cases of the Duracell and the West Marine. The Duracell has a 30-mo warranty. West Marine is 18.

I'll check out the duracell, thanks. I can get the optima d34m for $250ish, so it's hard to pass it up.

18 hours ago, Michigander said:

Part numbers?

Model # 15020233  and SKU: 9016-103

The Blue Top D34M only has a C20 of 55 Ah. Will that keep you on the water long enough?

 

www.optimabatteries.com/products/bluetop-d34m

 

"Weight     43.50

C20 Capacity    55.00 Ah"

VMAX MR137-120 marine deep cycle is 120ah, 75 lbs approx $290

XTR137, 137ah, 77 lbs, $350

NorthStar gr31 marine deep cycle is 120ah, 75 lbs,  approx $375

Tom

PS, you do not want a dual purpose AGM battery for TM’s in series.

I only look at reserve capacity for trolling motor batteries.  I have Optima blue tops 34 DMs on my boat with a 36 volt Minn Kota.  They will be 5 years old in a few months.  They are just now showing signs of loosing some power but not enough to keep me from fishing as long as I want to.  I msy replace them with AGMs from Sam’s club when necessary.

4 hours ago, mram10us said:

I'll check out the duracell, thanks. I can get the optima d34m for $250ish, so it's hard to pass it up.

Model # 15020233  and SKU: 9016-103

You can get the Duracell group 31 at Sam's for 179$

Great info guys. They are fitting in a specific location that only the D34 is short enough to fit in. I wish the others would fit

On 1/29/2021 at 4:26 PM, Jig Man said:

I only look at reserve capacity for trolling motor batteries.  I have Optima blue tops 34 DMs on my boat with a 36 volt Minn Kota.  They will be 5 years old in a few months.  They are just now showing signs of loosing some power but not enough to keep me from fishing as long as I want to.  I msy replace them with AGMs from Sam’s club when necessary.

You have the same setup I will, so do you have an issue with running out of juice after a couple days with no charge? 

Got this all setup with the 3 34dms and they ran 2 days on one charge and still had plenty left. Very pleased. Thanks guys

On 2/2/2021 at 8:48 PM, mram10us said:

Great info guys. They are fitting in a specific location that only the D34 is short enough to fit in. I wish the others would fit

You have the same setup I will, so do you have an issue with running out of juice after a couple days with no charge? 

I’m sure that they would have when new.  However I  never go two days without a recharge.  That is only going to shorten the battery life.

On 2/17/2021 at 4:43 PM, Jig Man said:

I’m sure that they would have when new.  However I  never go two days without a recharge.  That is only going to shorten the battery life.

I thought batteries want to drain almost all the way before being charged to full for longest life? What am I missing?

1 minute ago, mram10us said:

I thought batteries want to drain almost all the way before being charged to full for longest life? What am I missing?

Lithium - ya, you can drain them almost to the bone.

AGM - I wouldn't take it lower than 35%

Old fashioned Lead-Acid - never below half-charge.

The ratings aren't all the same across technologies.  AGM's are done.  No reason for them.  Price performance sucks.  Either buy el cheapos or step up to lithiums.

too late  got the agms a couple weeks ago.