Sustainable Electrical Setups for Older Motors

[lent0n]

I have a 1975 Evinrude 75hp that puts out 12.8V-13V to charge the battery, I'm told this is to be expected from the older motors. My only prior experience was with a 93 johnson that had an all in one regulator/rectifier. My current setup is the little universal 3 wire.

My main goal is to have consistent accessory usage while the boat is running without putting too much effort on the main cranking battery.

My current accessories are
- Speedo
- Tach
- Voltmeter
- USB Charger
- Stereo (old sony aftermarket deck)
- LED Nav Lights (only at night)
- Spotlights (very rarely used)
- Power Tilt/Trim

Because I'm only getting max .5-.6V extra from the motor, I was thinking about integrating a second battery that receives any extra charge from the motor and has a solar trickle charge running to it so that it can top up when it's not in use.

The system would look like this

Main Battery Lines from motor
||
House Battery -> Bilge Pump & Tilt/Trim
||
Smart Battery Isolator Switch like this one https://a.co/d/03kcqtR would set it up to 15 second delay so it doesn't switch when the power trim is in use.
||
Second Battery -> All remaining accessories
||
20 watt solar panel

I don't go fishing and generally just go out for cruises with friends that are an hour long tops and we'll go island hopping but I don't run any accessories while the motor is off.

I think this setup will provide a stable charging situation for the house battery and reasonable flexibility with the second battery that's able to get topped up from the motor charge but also a small solar panel to help it keep up when it's under heavier load

Open to feedback and thoughts!

 

[That old Mercury]

Hi
You really need to know the state of discharge on both of your batteries are at the end of the day.
Do you have a battery percentage meter you can put on both of the batteries one at a time?
They are pretty cheap to buy.
Also what type of charger are you using now? And how long does it take to top off the most used battery?

 

[racerone]

Wrong----It should charge the battery at about 14 / 15 volts just like any other motor.----What reading in ohms do you get on the 2 yellow wires from stator ???

 

[lent0n]

Hi
You really need to know the state of discharge on both of your batteries are at the end of the day.
Do you have a battery percentage meter you can put on both of the batteries one at a time?
They are pretty cheap to buy.
Also what type of charger are you using now? And how long does it take to top off the most used battery?

I have two voltmeters so could split them between the two, but the switch would show those levels if I needed to see them. Presently I just have the one battery in the system, but I have a spare truck battery and another marine battery to use.

 

[lent0n]

Wrong----It should charge the battery at about 14 / 15 volts just like any other motor.----What reading in ohms do you get on the 2 yellow wires from stator ???

I couldn't seem to find a straightforward guide online to test them which seems a little odd. I can go out and test pretty easily though.

If I understand correctly though.

1. Touch multimeter leads together to get a baseline reading
2. Test resistance between the two yellow stator wires that would go to the rectifier, subtract the baseline reading to get ohm reading.
3. Test stator leads to the ground as well.

I'm not sure what values I should be hoping for other than avoiding an outright short, some guidance there would help for sure!

If it makes any difference I use a fluke meter, and I do have a DVA adaptor tucked away somewhere.

I did notice last night that the positive battery post on the boat is cracked and a tight fit is crucial, I'm just waiting on a new one to show up today.

 

[dingbat]

Like water, there are two components to electricity, Voltage and Current

Voltage is the equal to pressure
Current is equal to flow

If you want to power your "accessories, you need to calculate current demand over time (flow) to power them.

Voltage is important, but not for this exercise

 

[That old Mercury]

I have two voltmeters so could split them between the two, but the switch would show those levels if I needed to see them. Presently I just have the one battery in the system, but I have a spare truck battery and another marine battery to use.

For solar charging to meet your demands you need to know where you are starting from, thats why i asked if you knew how discharged your battery was getting.
On this link it has a calculator about half way down the page.
Enter your battery Amp hour and solar panel you are looking at 20 Watt.
And how many solar hours it will be getting.

Solar Panel Charge Time Calculator For 12V Batteries (100W-500W Panels)

How long will a 100W, 200W, 300W, 400W, or 500W take to charge? Most of the resources on solar panel charge time you find are quite complex. We’re going to simplify the whole thing. In the end, you should be able to adequately calculate solar charge time for any 12V battery. We will help you ...

thegreenwatt.com

 

[lent0n]

Wrong----It should charge the battery at about 14 / 15 volts just like any other motor.----What reading in ohms do you get on the 2 yellow wires from stator ???

.6 ohms off the two main leads to the rectifier OL on both to grounds. The multimeter leads zero'd out so there was no resistance to subtract

 

[racerone]

.6 is good so perhaps a bad rectifier or bad battery.

 

[lent0n]

I would be replacing the stator.

You could've added a 'hate to be the bearer of bad news' hahahaha.

Present budget is tight, since there's no presence of melted insulation and everything else is otherwise running strong. Would it be safe to say that as long as there's a charge topping the battery up, stave off the accessories and leave it for a winter/spring job? There's about 6-8 weeks of the season left where I'm at.

 

[racerone]

Read 6 ohms at first and edited the post.

 

[lent0n]

Read 6 ohms at first and edited the post.

No worries! Rectifier is likely not the issue as I swapped it and had the same issue. I have a spare marine battery I can try, I'll put it on the trickle tonight.

I also went through the whole charge system from stator to rectifier and cleaned all the connections and there was a fair bit of build-up, the cable end at the battery had quite a bit of build up that went up the cable as well, so I'm going to replace the cable end as well as replace the broken terminal clamp and see how that works. Next step will be swapping out the battery.

 

[ESGWheel]

... and leave it for a winter/spring job? There's about 6-8 weeks of the season left where I'm at.

I think this is the best idea.
Let me explain: what you are looking to achieve is fine but trying to rush into it in the time remaining seems counterproductive. And given the budget constraints better to research it as thoroughly as possible during off season (there is a LOT good info about dual batteries and solar on this forum and elsewhere). And when you have a design in hand based on that research, post it and let folks provide their help. By doing this I suspect you will have a more holistic and solid solution that you can the plan for in terms of both the purchases needed and the installations required.

 

[lent0n]

I think this is the best idea.
Let me explain: what you are looking to achieve is fine but trying to rush into it in the time remaining seems counterproductive. And given the budget constraints better to research it as thoroughly as possible during off season (there is a LOT good info about dual batteries and solar on this forum and elsewhere). And when you have a design in hand based on that research, post it and let folks provide their help. By doing this I suspect you will have a more holistic and solid solution that you can the plan for in terms of both the purchases needed and the installations required.

Definitely! I'm not into rushing at this point, accessories are exactly that, accessories. Although now I'm more confused at my low charge situation, will try swapping to my backup battery and see if that resolves it with the clean/new terminal connections

 

[ESGWheel]

Awesome! And certainly investigate issue you currently have as they are the priority prior to modifications. So, focus on that, post what you find and folks will be able to help sort thru the issues in the next weeks. One quick thought: make sure your Multimeter is up to par. Whenever I have a suspect reading that do not make sense, I break out a spare and double check the readings. You can get a spare for free at Harbor Freight with the right coupon or just buy one for less than a Hamilton.

 

[lent0n]

Awesome! And certainly investigate issue you currently have as they are the priority prior to modifications. So, focus on that, post what you find and folks will be able to help sort thru the issues in the next weeks. One quick thought: make sure your Multimeter is up to par. Whenever I have a suspect reading that do not make sense, I break out a spare and double check the readings. You can get a spare for free at Harbor Freight with the right coupon or just buy one for less than a Hamilton.

We don't have such things in Canada, but I have a very good fluke meter, I'll borrow a second one from my mechanic this weekend and see if it yields anything different. Ultimately want to avoid blowing a stator for no reason

 

[racerone]

Your location?

 

[lent0n]

Your location?

Ottawa, Ontario

 

[airshot]

Do you have a good deep cycle battery for all your accessories to run off of?
I have a group 29 deep cycle lead acid battery that runs everything except the engine start and trim. I can be on the water all day, with gps, fish finder, radio, aerator for bait well and accessories plugs and barely run the battery down after all day ! Actually I have been on the water for two full days before the battery showed any real drop in its charge. What type of battery are you using and is it in good condition ?

 

[racerone]

evinrudeparts.ca-----Good source for parts.