Outboard Charging coils

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terrick

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Hi Folks
I have a Mariner 4hp 2stroke with a charging coil charging an 80ah battery (should have been smaller but the chandlers gave me this big one by mistake!) I want to run a Lowrance 3500 chart plotter but worried about spiking. Do I need some sort of voltage regulator
 
Should be no problem... The output is regulated to charge the battery, and the battery also acts like a very big capacitor and will iron out most electrical noise.
 
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Should be no problem... The output is regulated to charge the battery, and the battery also acts like a very big capacitor and will iron out most electrical noise.

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I would not be so sure about that. My experience of battery charging from small outboards is that it is just a rectified output from "lighting coils". It is in no way regulated and the open circuit volts (ie no load) can rise considerably above 12volts. It is true that the battery acts as a large capacitor so provided it is connected then it will prevent the voltage rising to unacceptable levels, especially with such a large battery but it is important to guard against ever attempting to use any sensitive equipment with the engine running and the battery disconnected. I did some severe damage to my auto pilot by accidentally doing that!

I cannot agree with the statement that the battery will iron out most electrical noise either. My VHF RT is virtually unusable if the outboard is running due to the level of electrical noise. It may of course be due to the ignition system and it may be possible to reduce it by taking the power from the engine directly to the battery and keeping the other wiring well separated from it. I have not investigated.

However provided these things are kept in mind then I would not expect too much trouble and if the output from a small Mariner is in any way superior to other brands, which I doubt, I stand corrected
 
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Hi Folks
I have a Mariner 4hp 2stroke with a charging coil charging an 80ah battery (should have been smaller but the chandlers gave me this big one by mistake!) I want to run a Lowrance 3500 chart plotter but worried about spiking. Do I need some sort of voltage regulator

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The Lowrance has been measured by a member on the Lowrance Plotters group at aboit 800mA on full wack ... down to barely 400mA on saver screen etc.(figs are approx.)

So your 80 A/hr battery will run that plotter for a whole day without any problem and still leave enough for bedtime lighting. Just in case you are worried about running both - charging and plotter together ... such that you disconnect charging and only connect when plotter is off ... (don't forget that antena has power on it as well !! even when plotter is switched off ....)
 
VicS, true, no load volts could vary, but with an 80Ah battery connected across it that should not be an issue. The noise I was referring to was alternator noise, not ignition / RF noise - the battery is big enough to iron out any spikes the alternator may generate. The power supply section of the chartplotter should easily cope with any ignition noise... VHF is another matter entirely! Intelligent comments tho! /forums/images/graemlins/smile.gif
 
You can minimise the problem of spikes of voltage by taking your power to the plotter from a point as close to the battery as possible. (for both positive and negative) any wires carrying both charge current and plotter power can mutually interfere depending on length resistance and inductance of the cables.
You can also minimise spikes by feeding the power to the plotter through or around a ferrite rod or ring. and using a bypass acapacitor of about .1 microfarrad from plotter input to ground.
These will minimmise spikes but not make the voltage safe if it rises above 14volts. However it should not rise above 14volts unless the battery is disconnected or fails in some way. ie the battery should soak up excess voltage.
As always your best bet is to fit an amp meter to monitor charge current and a voltmeter to check battery charge. olewill
 
Thanks for all your help. I have set the plotter up so I can tell how many volts it's receiving and with a 5w solar panel conected to the battery it can reach just over 13v when I first switch the plotter on then settles back to about 11.5v. I've wired the outboard direct to the battery so there's little chance of the battery being bypassed. Lowrance recommend that the plotter and it's receiver cables should be wired away from other electrical stuff so they go straight back to the battery and not to the main switch board.
 
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11.5 sounds like a nearly flat battery or a fault in the wiring. 12.5 volts would be a bit healthier. Can you accurately measure the voltage at the battery

[/ QUOTE ] The rule of thumb I use is that the voltage of a rested battery ie one that has been neither on charge nor in use for 12 hours is that 12.7v is fully charged, 12.5 is ok 12.2 is half charged and 11.7v is effectively flat, if measured with a digital multimeter

A reading of 11.5v when supplying a plotter indicates as you say either a flat battery or a very poor connection somewhere.
 
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Just check you have a regulator on the outboard, not all of them have them

[/ QUOTE ] I'll stick my neck out and say it wont have!
 
many years ago i bought a rectifier from a guy who used to make them in a garden shed and had an advert in PBO. With this fitted to the lighting coil on a Yamaha 8hp outboard I had It charged the battery fine but fried two brandnew VHFs before I realized there was a problem.(From then on only charged with everything switched off,not ideal)

Back then A vhf radio was about 2 weeks pay for me so I was very lucky the chandler took them back. When I took the second one back he commented that he had sold over a hundred and only had two "faulty ones"returned. (both mine)

I think modern outboards charging coil outputs are regulated but its worth checking.
 
I'll be very surprised if you find the output regulated on a small outboard. The output, which is intended for battery charging, is so small that there is no need. May be different on larger ones. Provided the battery is connected that will hold the volts down to a level that will do no harm. Absolutely no trouble with an Evinrude 6HP except that on a sail boat it is not run enough or fast enough to keep the battery charged (hence the purchase of small solar panel)
 
Im not very electrically minded so could you tell me how to check with a multimeter?

On my fairly new 4hp Suzuki i tried a digital multimeter connected it onto one wire between outboard and battery(Is that in series I think)I noticed that with a fully charged battery it was reading less amps than with a partially flat battery.Does this indicate that the output is regulated? It never got up to the 5 amps claimed by Suzuki,I think about 4 was as good as I got ,still better than nothing.
 
That all sounds Ok to me. You selected the 10 or 20 amp range on the meter (which probably also involved plugging the +ve lead into a dedicated socket)

You disconnected one wire between battery and outboard and connected one of the meter leads to the disconnected battery terminal and the other to the disconnected outboard terminal. That'll be in series.

As the battery charges the current will fall, just like it does if you use an old fashioned unregulated non automatic battery charger. I don't think what you have observed indicates any form of regulation.
Charging a battery you are never going to get the full 5 amps, infact I am surprised that you got as many as 4, because the voltage of the battery is always opposing the flow. You probably would, at least you should, if you just put a simple load on the outboard eg a number of lights totalling 60 watts or more

Now try monitoring the volts. Reconnect the outboard and battery as normal. Switch the meter back to its 20 volt DC range (not forgetting to put the +ve lead in its normal socket) and connect it accros the battery. You should get 12.7 volts from a "fully" charged battery that has rested for 12 hours (12.8v if you are lucky). 12.2v would be about half charged and 11.7 flat but I already said that.

Now start the engine, rev it up and you should see the volts rise, and they should slowly continue to rise as the battery charges. It will be a slow process charging with only 3 to 4 amps but eventually after many hours the volts should get to 14 or just above when fully charged. It might continue above that sort of figure if the battery is not huge which will indicate that the output is not regulated but with your 80 Ah battery it may not any way.

Now try measuring the volts from the outboard with the battery, and any other load disconnected. I think you will find that the volts produced is very speed dependent falling below 12 at idle and rising to well above 14 at high revs. A high voltage will confirm that it is not regulated. Thats what fried my Autohelm and your VHFs. I'm surprised about the VHFs though if the battery was connected. If the volts rises to a steady figure between 13.8 and 14.4 but goes no higher even with the engine at full revs then I will have to concede that it is regulated.

BTW be very careful if you have been using your multimeter for measuring amps. I promise you one day you'll forget to switch back to volts and connect it up to use as a voltmeter with the result that at the very least you'll blow the internal fuse (I bought a packet of those from Maplin) or wreck the meter totally. I've done that to several including a digital AVO!

I hope that helps. You will I think benefit from reading some of the basics on http://www.tb-training.co.uk/cover.html
 
many thanks for that.I have stored your post as a word document so I can print a copy to take over the boat.

At first with the new outboard I switched everything off but forgot a few times with no ill effect so I charge with the instruments on now.i will still do the tests out of interest.Cheers
 
I don't think the battery's flat because it's one of those with a little porthole in the top that shows green when fully charge and I've never had it any other colour than green! The plotter and receiver came supplied with there own common cable (sort of mini NMEA cable) which is powered straight back to the battery. The fuse holder for this has given problems in the past (bad contacts) so, may be, I need to have another look.
 
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I don't think the battery's flat because it's one of those with a little porthole in the top

[/ QUOTE ] Do not forget that indicator is only on one cell. That's ok when the battery is newish but you can have a situation where you have a dud cell but the one with the indicator is still ok.

Some fuse holders are very poor so if that has given trouble before suspect it again. Anyway check the battery with a digital multimeter (and a hydrometer if you have one and can access the electrolye). You can double check the fuse holder with a voltmeter across it while there is load on. There should be no more than a tiny fraction of a volt across it. Ideally none at all.
 
It's OK VicS your neck is safe even if you are not quite right /forums/images/graemlins/smile.gif

Just before Xmas I did a lot of sussing re power on one of my boats, it has a 9.9 Yamaha high thrust (magnificent motor by the way)

It does have charging coil and a regulator onboard. My machanic bloke said some do and some don't. Very generally old ones can charge but don't have regulators. Around the early 90's regulators arrived on some of the top end models and lately most have them fitted.

NOTE: He also said the range of options you get these days means some come stripped down with the minimum and won't even charge right up to the flash model which charges, rectifies, regulates and may even wipe your bum.

Basically you need to check the model closely (my one had 8 different optioned models in the same year) or as he said "those bloody little letters after the model on the plate".

FYI - My Yam 9.9 High Thrust now puts out 5.5 to 6 amps when at 2/3rd throttle and the 2 wires out the front of the cover go direct to the battery. Now we found the broken wire that is.
 
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