Charging identical batteries

[boguing]

Re: Nearly...

Haven't borrowed the ammeter yet, but just musing...

I don't (and I might be being completely stupid here) see what the difference between a typical boat setup and mine is. Is a marine alternator a bit more clever?

It seems to me that the problem is that the alternator is activated by the ignition key, and as the starter motor takes it gulp of Amps, the alternator (being a bit dim) thinks 'hey what a big drain - I'll throw out as many Amps as I can'. A second later, the drain disappears and the alternator drops down to very little current. Edit. Point is that it didn't really need to do that big surge.

If that's right, then my plan c might be to put the alternator sensor to the battery which is not attached to the starter. That way it'll never notice the starter drain.

Or that's all rubbish, it's not the way that the regulator works?

 

[boguing]

Re: Nearly...

Doh.

Just had a chat with folks at the pub. Light bulb moment.

Alternators are stupid. It'll just sit there making power even if nobody wants it. What a waste of energy. Why not just switch off the coils and save the engine power that's turning it?

Yet another plan to hatch Baldrick. As far as you lot are concerned, I'm up to d now. In reality it's probably z.

 

[Guest]

Re: Nearly...

[ QUOTE ]
Haven't borrowed the ammeter yet, but just musing...

I don't (and I might be being completely stupid here) see what the difference between a typical boat setup and mine is. Is a marine alternator a bit more clever?

It seems to me that the problem is that the alternator is activated by the ignition key, and as the starter motor takes it gulp of Amps, the alternator (being a bit dim) thinks 'hey what a big drain - I'll throw out as many Amps as I can'. A second later, the drain disappears and the alternator drops down to very little current. Edit. Point is that it didn't really need to do that big surge.

If that's right, then my plan c might be to put the alternator sensor to the battery which is not attached to the starter. That way it'll never notice the starter drain.

Or that's all rubbish, it's not the way that the regulator works?

[/ QUOTE ]

The difference is that I am talking NOT connecting to engine powered alternator ... I only use mine of a 240V mains battery charger.

As to switching the alt. off when charge is up etc. - could be a way to ruin your diodes in alternator controller ... even on a those alt's that have protection built in.

 

[boguing]

Re: Nearly...

Nigel, thanks.

Yep, you made that clear earlier - I forgot.

I think that the Maplin splitter will be saved for another project. Manual switching to protect the device from high/low volts/current is the only option. Shame, because it was to be all automatic.

Now digits will have to be extended (to work the switches).

The real annoyance is that an inverter would get around all of this - I just can't abide the idea of raising 12+ to 240 and then stepping it back down to 12 finite. Waste of energy /creativity!

 

[Guest]

Re: Nearly...

[ QUOTE ]
Nigel, thanks.

Yep, you made that clear earlier - I forgot.

I think that the Maplin splitter will be saved for another project. Manual switching to protect the device from high/low volts/current is the only option. Shame, because it was to be all automatic.

Now digits will have to be extended (to work the switches).

The real annoyance is that an inverter would get around all of this - I just can't abide the idea of raising 12+ to 240 and then stepping it back down to 12 finite. Waste of energy /creativity!

[/ QUOTE ]

Used with a standard charger - its magic !! Kept my two batts up all winter etc. In fact I never seen green indicator on my domestic before ... has been green for months now !!

 

[Danny]

Re: Alternatively...

[ QUOTE ]
So you'd rule out having domestic battery capacity larger than a single battery then?

[/ QUOTE ]No, I'd just prefer to have some way of isolating them from each other, if practical. The more of them you have in parallel the greater the chance of a failure in one of them and the more expensive the outcome if the others discharge through it.

I agree it's a small risk and, like so many other risks, it may be impractical to avoid it - but we should be aware of it all the same.

 

[pvb]

Re: Alternatively...

[ QUOTE ]
The more of them you have in parallel the greater the chance of a failure in one of them ....

[/ QUOTE ]How come?

 

[Danny]

Re: Alternatively...

[ QUOTE ]
[ QUOTE ]
The more of them you have in parallel the greater the chance of a failure in one of them ....

[/ QUOTE ]How come?

[/ QUOTE ]Statistics. If the MTBF for a battery is x years and you have y batteries then you'll likely get y failures in x years.

 

[pvb]

Ah, right...

[ QUOTE ]
Statistics. If the MTBF for a battery is x years and you have y batteries then you'll likely get y failures in x years.

[/ QUOTE ]Ah, right Danny, so following your unique brand of boating philosophy people should avoid twin-engined boats because they're twice as likely to break down? Oh, hang on, that can't be right, can it?

 

[Danny]

Re: Ah, right...

[ QUOTE ]
Ah, right Danny, so following your unique brand of boating philosophy people should avoid twin-engined boats because they're twice as likely to break down? Oh, hang on, that can't be right, can it?

[/ QUOTE ]Nope. Although a twin-engined boat will break down more often the problem is less serious because the other engine is still OK. In fact two engines are preferable because the chance of BOTH engines breaking down at the same time is fairly remote.

And following the same argument your 6 batteries must be preferable to 1 - so long as the failure of one of them doesn't affect the other 5.

OK Pvb - I admit it: it's more fun sailing than worrying about what can go wrong. Incidentally are all your 6 batteries the same size and type?

 

[pvb]

Re: Ah, right...

Glad to see your philosophy doesn't apply to engines!

Yes, my batteries are identical and all the same age, but I've previously used mixed lead-acid batteries in a big bank with no problems.

 

[Danny]

Re: Ah, right...

[ QUOTE ]
Glad to see your philosophy doesn't apply to engines!

[/ QUOTE ]It's not my philosophy - it's component failure impact analysis and applies to both engines and batteries. /forums/images/graemlins/smile.gif

 

[pvb]

Re: Ah, right...

I've never fully subscribed to the belief that the PBO forum largely consists of people who don't know what the f<span style="color:black">*c</span>k they're on about, but posts like yours do make me wonder if I need to review my position.

 

[Danny]

Re: Ah, right...

http://homepage.ntlworld.com/fast.electrics/parallelbats.pdf (OK - I know the article doesn't specifically refer to lead acid batteries)

Lighten up - I thought we just disagreed about something. If my comments about batteries are incorrect or unhelpful I apologise. They were based on knowledge gained nearly 40 years ago working at the Post Office Research Station when the GPO had telephone exchanges which were full of batteries.