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Discussion Starter · #1 ·
Anyone running the new 40/50 4 stroke with a lithium ion cranking battery? The Tohatsu manual recommends the following. Seems more than a little overboard, when compared to other engines of this size. I know it has to do with the electronics /ecu and all of that. Was really hoping to NOT have to put a 30 lb dedicated cranking battery in the boat, not to mention the cost.

Recommended battery: 12V 100AH/5HR, 850 (Cold Cranking Amps (CCA), In case of cold whether: 12V120AH/5HR (1000CCA)).
 

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Recommended battery: 12V 100AH/5HR, 850 (Cold Cranking Amps (CCA), In case of cold whether: 12V120AH/5HR (1000CCA)).
That's about what my Suzuki DF200A recommends so I would think it is overkill. I've forgotten the details of the post I found on this but call Relion and I'm sure they can tell you which of thier batteries provide the same real world capability as a 100Ah AGM
 

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Discussion Starter · #3 ·
10-4 Halfshell, I'll touch base with them also. I have an email in to Tohatsu as well hoping to get some clarification on these specs. Your right these numbers are typical for much larger engines.
 

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Your right these numbers are typical for much larger engines.
The Tohatsu engine's fuel system is low voltage intolerant, and thus they recommend big ass starting batteries. You can remove the anti-siphon valve from your fuel tank and/or add an electric fuel supply pump to compensate for that to use a smaller battery like with any other outboard. Your experience may vary.
 

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The Tohatsu engine's fuel system is low voltage intolerant, and thus they recommend big ass starting batteries.
It seems like that would favor a lithium battery since they maintain 13.6v down to 20% or 0% discharge depending on your reference, as opposed to a lead acid or AGM that goes down less than 12.6v after about 80% DoD. I wonder if thier literature recommends such a large conventional battery to compensate for typical discharge of lead batteries.
 

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My Lithium Ion ship’s battery died after 8 months while running with a Tohatsu 50 4 stroke
 

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Discussion Starter · #7 ·
The Tohatsu engine's fuel system is low voltage intolerant, and thus they recommend big ass starting batteries. You can remove the anti-siphon valve from your fuel tank and/or add an electric fuel supply pump to compensate for that to use a smaller battery like with any other outboard. Your experience may vary.
Good info, thank you. I didn't know the reason, I was under the impression it was because of the ecu / electrical BS.
 

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Discussion Starter · #8 ·
My Lithium Ion ship’s battery died after 8 months while running with a Tohatsu 50 4 stroke
Can you elaborate on this a little Stevie, details and the long term solution please?
 

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We installed a small gray West Marine AGM cranking battery. Charge it regularly. The weight is maybe 9 pounds more than the Lithium Ion.

There was a very good charger for the Lithium Ion as well.
 

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I have a 50 AH lithium ion battery for a 30 Tohatsu with a second one for the 24v TM. One is the house and starting battery, the other in series for the TM. No problems in over a year. I don't use the skiff as often as some do, since I fish outside too.
 
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Discussion Starter · #11 ·
Outside?? Also, what brand are the batteries you are using?
 

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Outside- in the ocean. Greenlife batteries, 15# each.
 
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What size lithium cranking battery are you using? You're probably have alternator charging issues with that battery so be mindful of that when you push it back into the garage.

The real question is why? You can build a battery that will give you the 1000 CCA and still weigh 10 pounds but you're not saving yourself any trouble unless for some reason you park a mile away and carry your batteries to and from your boat.
 

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My batteries are in the stern, only place I can put them. Every pound back there increases draft.
 
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Discussion Starter · #15 ·
My batteries are in the stern, only place I can put them. Every pound back there increases draft.
And ........its because its what you want.
 

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Discussion Starter · #16 ·
We installed a small gray West Marine AGM cranking battery. Charge it regularly. The weight is maybe 9 pounds more than the Lithium Ion.

There was a very good charger for the Lithium Ion as well.
I looked through the batteries at West Marine, I didn't see one that might have been the one you were referencing. When you get a chance if its not too much trouble, can you give me a little more info on this battery? If I have to go this direction it would be very helpful.
 

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What size lithium cranking battery are you using? You're probably have alternator charging issues with that battery so be mindful of that when you push it back into the garage.

The real question is why? You can build a battery that will give you the 1000 CCA and still weigh 10 pounds but you're not saving yourself any trouble unless for some reason you park a mile away and carry your batteries to and from your boat.
The battery that is used for cranking and house recharges from the alternator and depending on how much I run to get back to the ramp it's sometimes fully charged. I usually charge them every night after fishing, the non-house battery sometimes takes 2 hours to charge.
 

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A friend of mine has 1 x 100AH for the cranking battery and 3 x 50Ah for his 36v trolling motor in his Egret. He gets by by 3 x Ah for 36V because the 36v trolling motor is actually more efficient than a 24v; 50Ah may not work well for a 24v.

Never a problem in 3 years and his electronics and livewells run better. These are Relion LiFEP04 with a PowerMania charger.

I have 3 x Full River 105Ah AGM in my boat which weigh 67lbs each (total 201 lbs) and costs a little over $1000 total. Without a doubt, I'm going all LiFEP04 in my next skiff. Price difference vs good AGM is much less than a carbon kevlar or all epoxy resin hull for the same weight savings.
 

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The battery that is used for cranking and house recharges from the alternator and depending on how much I run to get back to the ramp it's sometimes fully charged. I usually charge them every night after fishing, the non-house battery sometimes takes 2 hours to charge.
I don't know the specifics of your charging set up but my MFS50A does not like the lithium cranking batteries without a charging controller.
 
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