How to improve engine charging?

[chrisbitz]

ok, I have an update, but I'm afraid it will be very unsatisfactory...

I got to the boat at twilight on friday, and before doing anything else, I opened the battery box, disconnected the negative wire (assuming that removing one wire would completely isolate it from the circuit) and measured the voltage on the posts.

18.7 volts????????

I'm guessing that relates to the solar charger, but I thought disconnecting only the negative wire would work to completely isolate it from any external influences?

the Nasa Battery monitor was saying a valid 12.7v or something like that, but I was so confused by everything, and the sudden darkness, that I turned on the electric and lights and heater, and didn't take any more measurements!

Why was the battery saying 18v, when the NASA was saying a more likely voltage? To my shame, the only other thing I can think of was the volt meter was saying the battery was low, but still, would a low battery in a volt meter show such a crazily different voltage?

Thanks for all the advice!

 

[Cappen Boidseye]

Well my portable intelligent battery charger, through various stages, takes the battery up to capacity, finishing up by a fixed voltage charge at 14.4 volts, once it thinks the battery is full it allows the batteries to drop back to around 13.8 volts and continues to keep the batteries there in it's "float charge" phase.
If I leave the batteries off charge they drop back to somwhere around 12.7 to 12.8 volts (I think- from memory). To me that is a happy and fully charged battery voltage. Mine haven't seen any charge or discharge since the end of September so I would imagine they will have self-discharged slightly, hopefully still over 12.5 volts.
As they are domestic type batteries, calcium flavoured, I have read that they should be taken to a higher maximum voltage when charging but my charger doesn't have the appropriate button.

During my Scottish West coast sailing week even though I did a lot of motoring due to lack of wind I found that I was getting down through my stock of currents. Too many electronic doodads, the autohelm and the occasional chill for the fridge were taking out more amps than the pathetic little alternator seems to be able to put back. I think my alternator is only a 14 amp alternator, it only seems to charge when I have the throttle in "thrap" mode, as in full cruising revs. As I was motor sailing I had been dropping the revs back so that with motor and sails I was doing my normal speed through the water so as not to waste fuel. With the throttle backed off like that the alternator just wasn't putting anything back into the battery. OK it was doing something because the fridge was working but there was nothing left for the battery top up unless I drove the engine hard. Is this normal? or do I need a better charging circuit? Or could a 130 watt solar panel be the answer? I am thinking about replacing the peltier cooled fridge with a Waeco compressor driven fridge and getting one of those panels before next year, would that be wise?

Sorry, long reply / comment!

 

[William_H]

Almost certainly if you measured 18volts witha portable digital volt meter then the voltmeter is inaccurate due to low 9v internal battery. Put a new battery in and see if that changes anything. The meter uses a voltage reference device. It compares the measured voltage with the reference. However if the supply voltage to the reference is low then the reference goes low. Typically there is enough power in the 9v battery to give a useable reading. But over reads.
Re Cappen Boidseye. I think if he gets rid of his Peltier type fridg and fits a compressor type his power supply problems will be over or at least a lot less.
A 14 amp alternator is unusual. (unless it is a fit on an outboard motor.) A bigger alternator or change of pulley sizes to give more alternator speed and or a better (smart) regulator might help. good luck olewill

ok, I have an update, but I'm afraid it will be very unsatisfactory...

I got to the boat at twilight on friday, and before doing anything else, I opened the battery box, disconnected the negative wire (assuming that removing one wire would completely isolate it from the circuit) and measured the voltage on the posts.

18.7 volts????????

I'm guessing that relates to the solar charger, but I thought disconnecting only the negative wire would work to completely isolate it from any external influences?

the Nasa Battery monitor was saying a valid 12.7v or something like that, but I was so confused by everything, and the sudden darkness, that I turned on the electric and lights and heater, and didn't take any more measurements!

Why was the battery saying 18v, when the NASA was saying a more likely voltage? To my shame, the only other thing I can think of was the volt meter was saying the battery was low, but still, would a low battery in a volt meter show such a crazily different voltage?

Thanks for all the advice!

 

[Stemar]

Re Cappen Boidseye. I think if he gets rid of his Peltier type fridg and fits a compressor type his power supply problems will be over or at least a lot less.
A 14 amp alternator is unusual. (unless it is a fit on an outboard motor.) A bigger alternator or change of pulley sizes to give more alternator speed and or a better (smart) regulator might help. good luck olewill

I'd suggest that a 14v alternator and a fridge are basically incompatible. Peltier effect fridges and any sort of limited power supply are incompatible as well (I know, I've got one. 6amps to cool a couple of bottles of white and harden the butter - and no thermostat!)

Adding solar panels will help, the more & bigger the merrier, but don't forget the controller. Do your research on that - they aren't all equal. I've seen it suggested that, in the UK, you can expect around 25% of your panels' wattage per day, so my 40w's worth give me about 10 amp hours on average. More on a sunny day in July, a hellava lot less on a dull day on December, but even then, they keep the batteries topped up between visits.

 

[chrisbitz]

I've seen it suggested that, in the UK, you can expect around 25% of your panels' wattage per day, so my 40w's worth give me about 10 amp hours on average. More on a sunny day in July, a hellava lot less on a dull day on December, but even then, they keep the batteries topped up between visits.

I've just installed 2x20w panels, and from sunday PM when I leave the boat to Friday PM, I'm noticing about 10A +-3A has been put into the battery. that's with dull december days.

I can't wait to see what a July week does!

 

[jac]

I've just installed 2x20w panels, and from sunday PM when I leave the boat to Friday PM, I'm noticing about 10A +-3A has been put into the battery. that's with dull december days.

I can't wait to see what a July week does!

Probably around 60ah in the 5 days if you're lucky. How much of that they can take will depend on how discharged they were. I hope you have a regulator!

 

[Cappen Boidseye]

My engine is a 3 cylinder 18 bhp Perkins diesel, I will check the alternator details, but it is awfee wee!
I am looking at investing in a flexible 130 watt panel with controller, not cheap but looking at the cheaper options, they don't have controllers and seem to be prone to corrosion when you look at the reviews. I would rather spend the extra in the hope of getting reasonable quality before throwing salt water at it!

http://www.amazon.co.uk/flexible-ch...40&sr=8-3-fkmr1&keywords=130+watt+solar+panel


Oh, according to http://www.perkins.it/103-07co.pdf it is a 14 Amp alternator, a cute little thing!

Having priced Waeco compressor coolers, maybe I will end up just with a decent peltier cooled fridge from Waeco (must be better than the Halfords thing II have got now! rather than a compressor powered beast, just too pricey! I need to give it a lot of thought before committing myself.

 

[William_H]

Cappen Boidseye. No don't buy another Peltier type. I don't believe that a "good" one will be much better than what you have. I tink your first move should be to replace the alternator with a more typical 40 or 60 amp one. ie from a car breaker second hand. You may be able to find something with similar mountings.
Yes a solar panel would help give charge while you are away from the boat. I have used one for 30years as only power source on the little boat and that is only 5watt. However if I had an inboard engine with alternator I would not bother with solar. This especially if you use the boat often. Anyway that is up to you.
Do however save your money for a compressor fridge. I have a CF 25 more as a freezer for the car and it works well and draws about 3 amps with on off cycle depending on temp selected and ambient. However the insulation is not very well done. ie I can feel the base outside icy cold so I sit it on foam. good luck olewill

 

[Pete7]

Oh, according to http://www.perkins.it/103-07co.pdf it is a 14 Amp alternator, a cute little thing!

Suggest you start with checking the output voltage of that alternator, 14AH is dreadful but if the voltage is low too you are on a hiding to nothing.

The Waeco fridges are excellent, froze my sandwiches the first time I used our CF18. Now sold because we fitted a similar sized compressor unit to the coolbox. Peeps were fighting over it on e bay and I think it sold for 2/3rds of the purchase price after 5 years. Yes I would buy another and the insulated cover that goes over them as an extra.

Solar would deffinately help and great time of year to buy a decent sized panel.

Pete