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jimmyant

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Posts: 76
Reply with quote  #1 
Thinking of switching out my dual 930 CCA start batteries for 2 new Deep cycle AGM batteries.
The AGM batteries have a good CCA rating of more than 1000 each so should be good as start batteries as well.
More battery power storage needed than I have now with the start batteries hence the reason for change  - want to run a refrigerator and some electronics over night.
I understand that AGM batteries may need a higher charging voltage than normal start batteries.
Can anyone advise if this is correct, and further, if the Etec charging system can produce the necessary charging requirements for AGM batteries.
Will I have any problems if I make the change?

Any help and advice appreciated!

Still loving my 200 HO G2. The power and economy is unbeatable. 500 hrs on the clock plus well support by a local dealer who is an absolute legend. 

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Extreme 745
G2 200HO
E200XHAGF
S/N 05493356
mead

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Posts: 776
Reply with quote  #2 
Cranking batteries are designed to deliver high current needed for the initial inrush of current demand during cranking.
Deep cycle batteries are designed to deliver high current but at a slower rate as needed by a trolling motor.
Thousands of boats use deep cycle batteries as the cranking battery and they work.....but in certain conditions such as very cold weather there will be a measurable loss cranking power. Does the boat operator notice this? Usually not.
The Etech starting system is designed to operate in some of the most unfavorable conditions, so deep cycle batteries do not exhibit the same loss of cranking power as may be noticed in the high compression 4 strokes.
I guess the other question is, why are you considering the change? Are you trying to correct a problem or are you trying to have the engine batteries do too much for other systems in the boat?
jimmyant

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Posts: 76
Reply with quote  #3 
Hi Mead,
Thanks for the quick reply.
I want to have more power available to run stuff on my boat overnight - my two start batteries are getting dragged down too far. As well as not having enough reserve of power, they will also be quickly damaged by expending more than 80% of their capacity.
So deep cycle batteries will give me the capacity I need. The batteries I am looking at have more more Ahrs available.
Yes, I understand the deep cycle batteries are not primarily designed for start operations, hence my choice of deep cycle battery also has a CCA rating well above the needs on the motor. Batteries each have a CCA rating of over 1000 compared with the text book Etec requirements of more around 700CCA for our warm conditions in New Zealand 😉.
My concern is more about how the motor can recharge the deep cycle batteries as I understand that AGM batteries need a higher charge voltage than lead/acid batteries? Be good to confirm that and to understand if my Etec can do the job satisfactorily.
Also asking from the awesome knowledgeable people on this site if there could be any other problems running twin Deep cycle batteries.

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Extreme 745
G2 200HO
E200XHAGF
S/N 05493356
mead

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Posts: 776
Reply with quote  #4 
AGM batteries and the Evinrude charging system are compatible.  The Evinrude charging system will regulate as is necessary.
almost forgot. Evinrude has been charging AGM deep cycle batteries for years now when the Aux battery charging cable is installed.
jimmyant

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Posts: 76
Reply with quote  #5 
Thanks Mead.
jimh - if you read this, would love to get your very technical electrical views as well please 😉

Cheers


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Extreme 745
G2 200HO
E200XHAGF
S/N 05493356
tmd11111

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Posts: 85
Reply with quote  #6 
Been running Duracell AGM's for over 3 years now.  Their dual purpose so can be used as deep cycle and cranking.  Also charging profile is almost identical as lead acid so no need for a different charger.
jimh

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Posts: 6,394
Reply with quote  #7 
I don’t have a concern with the batteries under discussion being deep-cycle or AGM construction. With their CCA rating there is no worry about starting any E-TEC engine.

My concern is for the use to run refrigeration over night (12-hours) while the engine is not running. That sounds like a large load. I recommend isolating the refrigerator load to one battery, and retaining the other without overnight discharge so it will be able to start the engine.

Another worry is the depth of discharge on the battery that runs the refrigerator. I assume that a deep cycle AGM that can deliver over 1,000-Amperes sustained peak current will be a large battery with an energy storage capacity of probably 80-Ampere-hours. That is a lot of electrical energy for the E-TEC engine alternator to replenish on a daily or routine basis.

Although Evinrude rates the alternator at 50-Amperes output, I don’t think it is reasonable to expect the alternator is intended or designed or capable of delivering 50-Amperes continuously for every hour it is running. The limit is not in the horsepower available, but in the wiring and diodes and heat dissipation in the alternator which is inside and encased and encapsulated in the EMM. A battery charger rated to deliver a continuous 50-Amperes would probably be built with heavier everything than what you see in the E-TEC. Keeping a big 80 to100-Ampere-hour battery—or worse two 100-Ampere-hour batteries in parallel—recharged after running a refrigerator all night on a routine basis was probably not what Evinrude had in mind for the EMM when they designed its alternator and battery charging circuits.

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sly_karma

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Posts: 16
Reply with quote  #8 
Agree on isolating the house battery especially given the substantial fridge load. And that load will presumably be drawing during the day as well; the charging system will be working very hard to get in front. Isolation can be done with a battery switch but better to automate it with an automatic charging relay (ACR) like Blue Seas. The ACR prevents operator from forgetting to set the switch to isolate the designated starting battery.
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1980 Lund 19.5 Royale
jimh

Registered:
Posts: 6,394
Reply with quote  #9 
KARMA makes a good point. If while the E-TEC is running is has to recharge its starting battery, recharge the deeply discharged house battery, AND supply high current to keep the refrigerator cold, the alternator is being asked to perform an extraordinary task.

Cruising boats with battery-operated refrigerators tend to use really huge banks of multiple batteries that are completely isolated from the engine starting battery. They also use completely isolated belt-driven alternators running off their propulsion engine to charge those battery banks separate from the cranking battery.

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