Amp hour ratings?

[mram10us]

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

[Johnbt]

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.

[Michigander]

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?

[mram10us]

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

[Johnbt]

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"

[WRB]

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.

[Jig Man]

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.

[Mjmj]

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$

[mram10us]

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? 

[mram10us]

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

[Jig Man]

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.

[mram10us]

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?

[MN Fisher]

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.

[Deephaven]

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.

[mram10us]

too late  got the agms a couple weeks ago.