jnaumov

Help with electric motor battery selection and charging

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Hey gents, 

Hoping I can get some advice. I’ve just ordered a brand new 510 Stealth Hornet with a Mercury 115HP Pro XS. The next six weeks is going to be the longest wait of my life! Anyway, I’ve been told I should run an 80lb Minn Kota which of course means running a 24v battery system. 

I’ve been looking around and as much as I’d love to go lithium (LiFePO4) batteries, I don’t think think they’re at a price point I can justify just yet. With that being said, I was looking to run 2 x 120Ah AGM batteries. 

Question #1: 

Is 120Ah an appropriately sized battery for my boat setup? Granted I don’t do any offshore fishing so I wont be spending time in any raging currents for hours. I mainly fish, rivers, creeks, estuaries and the odd calm day in the bay. But I will occasionally do a solid 7-8 hours on the water. 

Obviously going to a 24v system I need to get a 24v charger. From what I’ve heard about 12v systems, you need to pick a charger with an amp output at least 10% of the battery amp hour rating. For example, to charge a 100Ah battery, your charger should be able to charge at 10amps. 

Question #2:

Is this is the same theory with 24v systems? If I’m going to run 2 x 120Ah batteries in 24v, would I need a 24v charger with an amp output of at least 12amps?

I know I can still charge the batteries separately with a 12v charger but I want to be able to hook it all up, start charging and go to bed, ready to fish the next day. 

Sorry for the novel in advance. 

Cheers

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Well done on the new boat.

I have a 510 Frontier and use a 55lb minkota. 

Works fin in all the conditions that I fish.

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im running an 80lb on my 5m horizon and im using 2 x 105AH AGM batteries which are connected to a Pro Mariner on board charger. all i do is plug the charger into an extension lead when i get home. My boat is 5 years old and ive never even taken the battery box lids off my battery boxes.

For your 510 i would definitely run a 80lb lecky 

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10 minutes ago, sydney south said:

Well done on the new boat.

I have a 510 Frontier and use a 55lb minkota. 

Works fin in all the conditions that I fish.

Interesting... what size outboard do you have? And what size battery/how long does it last until it needs a charge?

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2 x 120Ah will be plenty for an 80lbs leccy.
 

You can use a 12v charger for a 24v set up just charge them in series (positive to battery A, negative to battery B). Just make sure they are the same battery and same level or charge (voltmeter helps). 12amp+ charger will be fine.

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28 minutes ago, flatheadluke said:

2 x 120Ah will be plenty for an 80lbs leccy.
 

You can use a 12v charger for a 24v set up just charge them in series (positive to battery A, negative to battery B). Just make sure they are the same battery and same level or charge (voltmeter helps). 12amp+ charger will be fine.

Flat-Luke............  if you have a 12volt charger you MUST charge each battery to 12 v separately OR use 2 x 12v chargers (1 on each battery)  OR use a 24v charger across both batteries (in series)

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Posted (edited)
14 minutes ago, dmck said:

Flat-Luke............  if you have a 12volt charger you MUST charge each battery to 12 v separately OR use 2 x 12v chargers (1 on each battery)  OR use a 24v charger across both batteries (in series)

Yep, if you want charge them off the one 12v charger they need to be in parallel via a connecting lead (+ to + and - to -)  attach the charger lead to the positive of one and the negative of the other other battery, that way they will charge evenly. As dmck said you will need a 24v charger to charge them in series 

Edited by wcurrall
Misprint

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On 3/2/2020 at 1:35 PM, jnaumov said:

Interesting... what size outboard do you have? And what size battery/how long does it last until it needs a charge?

Always get a full day. 

Charges overnight. 

Have a 115 etec.

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Good questions!

I run an 80lb Motorguide and have the 120mAh batteries setup as 24v..

Short explanation = I charge everything from solar panels on the roof and being a 12v system, I run a thick cable between the two batteries (with Anderson plugs) so they when the cable is pulled apart, the batteries are back to being individuals at 12v.

Longer explanation = I've built an ss316 chassis at the transom to house Neutrik connectors that are connected to the 4 batteries on the boat. 1 main, 1 accessories, 2 for the Motorguide. When at home I plug in the charge controllers to the panel and each battery is looked after. The 2 batteries for the Motorguide need to be disconnected from each other before this or you'll start hurting things.

I didn't want to go to a 24v charger as I had the 12v solar in place and apart from their purchase price I now charge the boat plus a multitude of other things at home from the Sun.

Cheers,

TC.

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