DC to DC chargers

[brad_tate]

Hi all,

I am planning to install a DC to DC charger in my boat so I can charge my deep cycle battery when on the water and would appreciate any advice your have. I have a single standard 12v Century starter battery and a single 12v deep cycle battery (Besco I think) in my boat. The starter currently powers the 60HP Yamaha 2-stroke, bilge pump, fish finder and navigation lights. The deep cycle powers the Minn-Kota electric and the live bait well. In future I plan to add LED lighting off the deep cycle. Normal battery maintenance is via a Ctek mains charger.

The Sterling Pro Charge B BBW1220 looks like a pretty good unit to charge the deep cycle whilst I'm on the water. The Ctek 250S dual is cheaper but doesn't look like it's designed for marine use, so I'm currently leaning to the Sterling. Installation of the Sterling looks very straightforward and pretty much set 'n forget.

Does anyone have any feedback on either device above, or an alternate?

Any particular tips or gotchas?

Should I move the fish finder etc to the deep cycle, or just leave well enough alone there?

Thanks, Brad.

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[batfishing]

If you want to contact us tomorrow Roadrunner Parts, we are a sponsor on here. I will be happy to go through the units with you.

Options are:

DC to DC charger

Or

Voltage Sensitive Relay. VSR

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[stevemid]

Does your boat normally sit on a trailer? What is your charging regime? Any particular problem you are trying to solve?

Normally you'd want to protect your start battery from being discharged by accessories to the point where it wouldn't start your motor. How much night fishing you do and the type of nav lights you have and how much your sounder draws all figure in to this.

Normally (again) if all your start battery has to do is start the engine, and the engine starts quickly, then you'd have left over charging capacity off the motor's alternator, which could be usefully directed to the trolling motor battery, to give that battery the excess amps which would be otherwise wasted once the start battery has been topped up.

I would guess that under your current setup your sounder and nav lights may be consuming much of the excess output, since 60 hp motor alternators don't put out a lot; but there may still be some left over.

Given that your setup is not normal, you'd have to think through the pros and cons of making it normal. This would include doing an inventory of your charging and discharging rates under normal usage. For example, at the end of a typical outing, how much capacity has been drawn from each battery? How much has the alternator put back in? How much capacity is left in each battery? This analysis will let you know if you are damaging the batteries and whether you are at risk of a no-start situation. This IMO is the main 2 issues I'd be concerned with in the first instance.

DC chargers from what I have read are mainly useful as Multi-stage chargers which when coupled with high output alternators do a good job of giving deep cycle batteries a full charge - something they can't get from a typical alternator. This is especially useful to campers and off roaders. I am assuming that if your boat normally sits in the shed in between trips and that if your deep cycle sits on the charger the whole time that your deep cycle is getting fully topped up so I don't think, given my assumptions that you'd get much benefit from a DC charger. But then the way you are currently "load balancing" I'm also not sure a VSR would do much good either.

My advice would be to do the inventory: the capacity of your batteries, how much night fishing you do, how much your appliances draw, and whether you have analogue or LED nav lights all adds into the final recommendation. Bottom line though is that you shouldn't be regularly discharging a deep cycle battery more than 50% and a start battery more than 20%, or you will shorten their life. Lastly, you should never risk not being able to start your motor.

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Edited July 4, 2014 by stevemid

[brad_tate]

Thanks for the feedback, all very much appreciated.

Yes, my boat is normally out of the water on a charger. I typically charge my deep cycle battery fully after each fishing trip, and also charge both the deep cycle and starter battery every 6 months regardless. Once a year I charge each on a Recond cycle. The boat is not in a shed so I don't leave the deep cycle on permanent float charge.

I've only just installed the bait well, and am using the deep cycle so it can't affect the starter battery - as you said, first priority is being able to start the motor. We also periodically go away for a week at a time, sometimes unpowered, but even when powered, we leave the boat in the water for the week, so charging from AC is difficult.

The intention with the DC-DC charger is to keep the deep cycle topped up continuously when on the water. For the longer trips it will ensure I don't run out of power, and even for the shorter trips it will lessen the amount I draw down from the deep cycle - i.e. always near the top of the charge. My understanding is this will also prolong the life of the battery. I can't charge the deep cycle straight off the alternator or just connect it in series with the starter battery as my understanding is that will damage the deep cycle.

Thanks, Brad.

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[stevemid]

Assuming both batteries are 12V you could charge both with the altternator using either a 1,2 Both switch or a VSR. IMO you don't need a DC charger to do that. nTalk to the guys at Roadrunner, see what they say. Your motor doesn't put out a hell of a lot of charge.m This discussion is pertinent. Especially for your week away: http://www.thehulltruth.com/boating-forum/190787-how-do-i-improve-charging-ablity-yamaha-150-2-stroke.html

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[brad_tate]

Thanks again, great advice. I did speak to the Roadrunner guys today, and they were very helpful. They're a bit out of my way but I will do the k's to support such a good sponsor. They went through the VSR and straight charge options, but what I took away is that they now prefer the DC-DC option. It is more expensive but seems to give better results.

I was very interested in the thread about the Yamaha alternator output. My motor is a 2009 model so I am hoping it has a stronger output than the older models - will do some more digging here. I'm pretty comfortable with the Sterling option so will go down that path in the next month or three and will post an update to let you know how it goes.

Again, thanks for all the feedback, Brad.

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[stevemid]

6A. http://www.yamaha-motor.com.au/products/marine-outboard/2-stroke-mid-power/11-60f

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[batfishing]

Brad, looking at that link above, that is a low output alternator, one thing I would suggest first is putting a multimeter over the battery with the engine running, do this in the water, because I suggest you try and check with an engine rpm of 1,000 - 2,000RPM, then see what voltage you are getting at the battery.

If you let me know that, I will check the specs on a few more DC to DC chargers as well as the one you have researched

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[brad_tate]

Hi all,

I picked up my boat from the guys at Hunts Marine last week, and on their advice I have connected the live well to the main (crank) battery not the deep cycle. Their view is that a) powering anything else as well as the Minn-Kota from the deep cycle will potentially damage the battery; and incur a lot of extra expense to put in a new circuit, bus etc (est 10 hrs labour). This wasn't what I expected but I am happy to take their expert advice. As always their work was first class, so no complaints there.

I am still interested in pursuing the DC-DC charger for my longer trips, installing lighting down the track and making the deep cycle available as an emergency option to start the motor, so will take your advice and measure my normal voltage under power (to assess the current from the alternator) and calculate my current draw so I know what I can expect from my main battery. I will let you know how I go.

Thanks, Brad

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[brad_tate]

Hi all,

I installed my Sterling DC-DC charger today and next Sat we head off for a week away so it will be a good test for it. I'll let you know how it goes.

Regards, Brad

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[antonywardle]

are you back yet?

How'd it go?

[brad_tate]

Just got back from a week at Stuart's Point yesterday, spent 5 days on the water (4-5 hours/day). I had no problems with the deep cycle emptying, but I was down to 1 bar on the iPilot by day 5. That's not dissimilar to previous trips without the Sterling.

So at the moment I am not sure - I was expecting to keep the deep cycle more charged than that, but I may have been using the motor more this time than previously (I certainly didn't ration my use). Perhaps on a longer trip it would show the value better. We're planning to go down to Tuross in either late Feb or early May for a week so will see how it goes then. Testing certainly showed it was working fine, so no problems there.

The trip back to Sydney wasn't without incident however, so when I have a chance to crop a couple of photos I'll post about that. Suffice it to say I am glad I have comprehensive insurance on my boat, and it wasn't my fault!

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