ampage

[OceanSprint]

My outboard has a 6 amp alternator. With it i can direct that ampage at either my starter battery or my domestic. My halfords top ofthe range battery charger can only give out 2 amps max.

My question is, does it harm batterries to put 6 amps into them ?

 

[Rigger Mortice]

My outboard has a 6 amp alternator. With it i can direct that ampage at either my starter battery or my domestic. My halfords top ofthe range battery charger can only give out 2 amps max.

My question is, does it harm batterries to *** 6 amps into them ?

You don't say what the capacity of the batteries is but it is far more likely that you are undercharging both batteries rather than overcharging either one or both. With that setup two batteries is overkill.

 

[OceanSprint]

Starter is 45amp hours and domestic is 75 amp hour. But not sure whatyou mean by overkill. Its on a 24 foot yacht with a full set of electronics and internal / external lights, etc.

 

[VicS]

You dont say what the outboard is or if the "alternator" output is regulated or not. Most modern ones are although older ones are often not.

If it is regulated there will be no problems with overcharging and the batteries will only take what they need. Your car alternator can probably deliver a maximum of 55 amps or more but it does not overcharge the battery does it?

Generally with outboard charging "alternators" the problem is more likely to be undercharging unless you run at fairly high revs for prolonged periods esp if you are powering loads of electronics and esp lights.


It the long term you will more likely to be looking as methods of reducing power consumption eg with LED lighting and supplementing your outboard charging with a solar panel.

( My outboard gives 5 amps but really quite inadequate even with modest power consumption . Until I fitted a small solar panel I used to have to take the battery home for charging periodically)

Not quite sure how you consider a 2 amp battery charger to be "top of the range" .. it's just a baby suitable for little more than maintenance charging.

 

[OceanSprint]

Thanks for the considered reply. In answer,

Not sure if it is regulated. Could this happen inside the outboard as there is nothing outside. I will have to look atthe manual. It is a Yamaha 9.9 hp GEL something.

Top of hte range, cos itwas top of the price. Says it does lots of things very intelligently, which is more than i can.

 

[Rigger Mortice]

Starter is 45amp hours and domestic is 75 amp hour. But not sure whatyou mean by overkill. Its on a 24 foot yacht with a full set of electronics and internal / external lights, etc.

Your likely problem is one of undercharging , not overcharging.

Without knowing what electronics you have and how they are used it's impossible to say how long the batteries will keep going. However. if you were to get them down to 50% capacity you would need to put 60Ah back in. With your outboard only producing 6 amps (and that will be flat out in ideal conditions, so it is likely to be less than 6amps in the real world) it is going to take an absolute minimum of 10 hours to recharge...and that assumes that you are not using any of your electronic gizmo's during that time.
Add to that that an outboard starter motor doesn't really use much power and, in any event, you can easily resort to manual starting.

For those reasons I would say that you have too much battery capacity as it is likely to never be properly charged.

 

[VicS]

Thanks for the considered reply. In answer,

Not sure if it is regulated. Could this happen inside the outboard as there is nothing outside. I will have to look atthe manual. It is a Yamaha 9.9 hp GEL something.

Top of hte range, cos itwas top of the price. Says it does lots of things very intelligently, which is more than i can.

Id guess that a Yamaha 9.9 would have a regulated output. Certainly a recent one does. The regulator is combined with the rectifier and is part of the engine power head assembly.

Halfords most expensive battery charger currently listed on the website is a Ctek MSX10 at £130 . It has a max output of 10 amps. Ctek actually offer chargers up to 25 (or 30 ??) amps IIRC

The one with highest output is a Ring workshop charger with an output of 20 amps and priced at £70

 

[Stemar]

As others have said, it sounds as though under charging is far more likely to be a problem than over. From memory, batteries are unlikely to be damaged by being charged at 10% of their capacity, so the OB is unlikely to be an issue.

I have a 24 footer with an inboard diesel, but the best investment I ever made for her was a couple of 20w solar panels and a clever controller that throws 90% of the panels's output at the starter battery until it burps, then charges the domestic one. In summer they keep up with our power usage at anchor as long as we don't use our (rather inefficient) cold box and even in winter, they replace my weekend's usage over the next week. Worth thinking about IMHO.

 

[OceanSprint]

Many thanks. I do have a small solar panel, but i don' t trust the controller. I have had episodes where i ve left it for several weeks, including very clear days, and thwe battery seems worse off than if i leave it isolated.

 

[Rigger Mortice]

Many thanks. I do have a small solar panel, but i don' t trust the controller. I have had episodes where i ve left it for several weeks, including very clear days, and thwe battery seems worse off than if i leave it isolated.

What size is your panel?

 

[nigelmercier]

Halfords most expensive battery charger currently listed on the website is a Ctek MSX10 at £130 . It has a max output of 10 amps...

Just over £100 on Amazon: http://amzn.to/1nhWzmS

This size should be sufficient to fully charge from 50% overnight.

 

[William_H]

If OP has doubts about the solar panel regulator then he should try connecting solar directly to the battery. A small panel is unlikely to harm a big battery without regulation.
A mains charger rated at 2 amps is likely to need a long time to recharge the batteries from say 50%.
What OP needs is an amp meter so he can see exactly how much current is going into the batteries. (and a volt meter to see how the battery is coping with discharge) While both the mains charger and o/b charger might be rated at 2 and 6 amps respectively that is a max and does not reflect what the batteries take as a charge. This is usually much less especially after a period of charging. good luck olewill

 

[CreakyDecks]

You aren't going to damage a battery by charging it with six amps, car alternators might put ten times that into them just after starting the car. What you should be wary of is continuing to charge your batteries when they are already fully charged. That will cause them to give off gas, which is a bad thing. Putting aside the small danger of an explosion, the batteries will dry out and be permanently damaged. I had a motorbike that did that because the regulator was knackered. It used to go through a battery a year! (I know, I should have fixed it but batteries were a tenth the price of the regulator )

 

[AngusMcDoon]

My outboard has a 6 amp alternator. With it i can direct that ampage at either my starter battery or my domestic. My halfords top ofthe range battery charger can only give out 2 amps max. My question is, does it harm batterries to put 6 amps into them ?

With 2 batteries and a 10hp o/b engine you do not need separate starting and domestic batteries. 2 domestics in parallel is the normal arrangement. This is because the cold cranking amps output with this arrangement, although lower than a dedicated starting battery, is ample. My 10hp electric start o/b engine's supply goes through a 50A fuse, so you can see how low its starting current is compared to a diesel engine of the same power output. Because the starting current needed is so low if, the batteries are a bit down, the engine will still start fine, and finally, a 10hp o/b is dead easy to start by hand from cold anyway if the batteries won't do it.

I have 2 75Ah capacity batteries installed, a 12A output from the engine and a 30W solar panel. I run all the usual electronics, tillerpilot and a compressor coolbox. Never run out of Ah yet in over 10 years with careful use and LED lights. It's the bog standard arrangement all Dragonfly trimarans use that don't have an inboard and we all seem to cope despite the naysayers saying our batteries will be permanently flat.

 

[Spi D]

As a rule of thumb the charger should be at least 10% of the battery capacity - in your case 7.5 A if charging one at a time.

For all intelligent chargers (runs throug a number of stages, time depending on battery state) it is important that you allow it to complete the stages.

As an example - 7 stages:

 

[OceanSprint]

The charger i have has 7 stages, but never seems to get out of the 2 amp stage. But i have just read the customer reviews for it - a halfords smartcharger 100. Wish i had read the reviews before buying it! Agree with all of them.

I must admit i like my starter /domestic set up. It keeps the 2 functions apart, andwith my 1-2-both switch, along with a switch board i made, i can select either battery to do either job, or connect them in parrallel.