A *SIMPLE* battery charging question (I hope)

[Timleech]

I have a work boat which gets occasional use and currently doesn't have the alternator connected; also an electric start pressure washer with dead alternator; as well as several batteries about the place which need occasional charging to keep them alive.

I have a basic 'garage type' charger, probably just a tapped transformer and rectifier, which has 5 switchable charging settings.

Is there a straightforward, easy charging/maintenance regime I should follow to maximise the lives of the batteries? At the moment I usually set the charger on no.4, & leave it on until the rate has dropped to an amp or three, though the ammeter is rather unreliable.

 

Thanks

Tim

[chris w]

"Garage-type" chargers are designed to charge starter batteries, viz: heavy current out of battery for a few seconds. A couple of AH used. Quick recharge.

 

They will, of course, eventually charge a deeply-discharged battery like a domestic battery but will eventually damage it as the output from these chargers is just constant voltage rather than constant current as in the bulk stage of multistage chargers. They also charge typically at lower voltages than multistage chargers and so take an age to get any real charge into the batteries.

 

So they are OK in emergency but not OK as the regular charging regime.

 

Chris

[smileypete]

I have a work boat which gets occasional use and currently doesn't have the alternator connected; also an electric start pressure washer with dead alternator; as well as several batteries about the place which need occasional charging to keep them alive.

I have a basic 'garage type' charger, probably just a tapped transformer and rectifier, which has 5 switchable charging settings.

Is there a straightforward, easy charging/maintenance regime I should follow to maximise the lives of the batteries? At the moment I usually set the charger on no.4, & leave it on until the rate has dropped to an amp or three, though the ammeter is rather unreliable.

 

Sounds good, although I'd check the charge voltage at the end of charge is around 14.4V to 14.8V.

 

If the charge voltage is low, the charge current may fall to a low level even though the battery isn't fully charged.

 

Another reasonable way of checking how they're charging is to see if the acid in each cell of the battery is bubbling/gassing some.

 

Low charge current and gassing cells should mean the battery is pretty well charged.

 

There's a good battery FAQ at www.batteryfaq.org

 

Edit: One thing worth a mention is to switch off the charger before disconnecting the leads from the battery.

 

cheers,

Pete.

Edited March 22, 2008 by smileypete

[chris w]

Sounds good, although I'd check the charge voltage at the end of charge is around 14.4V to 14.8V.

 

cheers,

Pete.

 

Car-type chargers don't usually charge at a voltage as high as this, which is one of the fundamental problems with them for use with a domestic battery. They tend to be around 13.8v.

 

Chris

[Timleech]

Car-type chargers don't usually charge at a voltage as high as this, which is one of the fundamental problems with them for use with a domestic battery. They tend to be around 13.8v.

 

Chris

 

It is, as I said, a garage (ie commercial) type charger, with switchable charge rate although electrically no doubt very crude. I'm pretty sure the available voltage goes higher than that, I'll check tomorrow.

 

Tim

[chris w]

It is, as I said, a garage (ie commercial) type charger, with switchable charge rate although electrically no doubt very crude. I'm pretty sure the available voltage goes higher than that, I'll check tomorrow.

 

Tim

 

But what does "switchable charge rate" mean? Current or voltage? If you are going to use this device as your main charger, you do risk damaging your batteries. The charge mechanism is very crude and not like a multistage charger; it won't have the bulk (constant current) stage.

 

Chris

[Timleech]

Car-type chargers don't usually charge at a voltage as high as this, which is one of the fundamental problems with them for use with a domestic battery. They tend to be around 13.8v.

 

Chris

 

I just checked the open circuit voltages on my charger, around 15V on position 4, and 17V on position 5.

I've charged several batts at the end of last week, more maintenance than because they were discharged. Checked the voltages on them today, at least 24 hours since the last was disconnected, all but one were showing around 12.9V.

 

Tim

[chris w]

I just checked the open circuit voltages on my charger, around 15V on position 4, and 17V on position 5.

I've charged several batts at the end of last week, more maintenance than because they were discharged. Checked the voltages on them today, at least 24 hours since the last was disconnected, all but one were showing around 12.9V.

 

Tim

 

As you say that's the "open circuit" voltage. It bears no relation to what the actual charge voltage will be on load. The difference will be due to the internal resistance of the charger which, for a simple transformer type, will be relatively high.

 

You will sulphate up the batteries eventually by using this kind of charger.

 

Chris

[Timleech]

Sounds good, although I'd check the charge voltage at the end of charge is around 14.4V to 14.8V.

 

Just had a (not deeply discharged) battery on charge for a few hours, the final voltage was 14.9

 

There's a good battery FAQ at www.batteryfaq.org

 

cheers,

Pete.

 

 

Thanks, looks interesting

 

As you say that's the "open circuit" voltage. It bears no relation to what the actual charge voltage will be on load. The difference will be due to the internal resistance of the charger which, for a simple transformer type, will be relatively high.

 

You will sulphate up the batteries eventually by using this kind of charger.

 

Chris

 

Doesn't the internal resistance depend on the particluar transformer, rectifier etc? any particular reason why it should be high?

 

I was hoping for constructive tips on how to make best use of what I have available, not to simply be told it's rubbish

 

Don't forget we're not talking about heavy usage here, just putting back odd bits of engine starting, bilge pumping etc and maintaining unused batteries.

 

Cheers

 

Tim

[Dylan]

I keep a couple of "spare" leisure batteries on a permanent float using a cheap horrible old Helfords charger and a couple of large wire wound resistors in series which hold the charging voltage at 13.5 volts. I think they are around 4 ohms each but can check. I give them a zap now and again without the resistors for a few hours which sees over 15 volts. Dead crude but effective and cost less than a quid (already had the charger). Someone else on here had the idea some time ago.

[chris w]

I was hoping for constructive tips on how to make best use of what I have available, not to simply be told it's rubbish

 

Tim

 

I've given my view on your chargers and I would in no way recommend them. If you choose to ignore the advice that's your perogative. BTW, if the final on-load voltage is 14.9v I trust they are not sealed batteries or you're going to get a big bang one day.

 

Chris

[Timleech]

I've given my view on your chargers and I would in no way recommend them. If you choose to ignore the advice that's your perogative. BTW, if the final on-load voltage is 14.9v I trust they are not sealed batteries or you're going to get a big bang one day.

 

Chris

 

Your view seemed to be based on the voltage being too low, now it's too high.

No, they're not sealed batteries, maybe a constructive comment would have been to turn it down for sealed batteries?

 

Tim

[smileypete]

Just had a (not deeply discharged) battery on charge for a few hours, the final voltage was 14.9

Sounds good.

 

You could get exactly the same result with a few hundred quids worth of a super duper adaptive desulphating multi stage charger if you really wanted to.

 

cheers,

Pete.

[chris w]

Pete must be right and we're all total idiots for buying multistage chargers at £300, when all the time a cheap Halfords car charger would have done it for £30........... thank God for Pete. I sit at the feet of the master and learn.

 

Tim.... my only constructve comment is.... don't do it. It will all end in tears.

 

Chris

[Timleech]

Pete must be right and we're all total idiots for buying multistage chargers at £300, when all the time a cheap Halfords car charger would have done it for £30........... thank God for Pete. I sit at the feet of the master and learn.

 

Tim.... my only constructve comment is.... don't do it. It will all end in tears.

 

Chris

 

 

OK, what is the fundamental difference between using a simple charger, with a little care, and charging with a bog standard alternator with its inbuilt regulator?

Genuine question, I'm interested in the answer.

 

Tim

[chris w]

OK, what is the fundamental difference between using a simple charger, with a little care, and charging with a bog standard alternator with its inbuilt regulator?

Genuine question, I'm interested in the answer.

 

Tim

 

Nothing really. Both are constant voltage devices and BOTH are bad for your domestic batteries. That's one of the reasons why one fits an alternator controller.

 

Chris

[Gibbo]

If you charge them up say every 4 or 5 days or so, and leave them on charge until you get to about 14.9/15.0 volts that will be fine.

 

A reasonable charge regime similar to what a clever charger would be doing anyway.

 

Gibbo

[Timleech]

If you charge them up say every 4 or 5 days or so, and leave them on charge until you get to about 14.9/15.0 volts that will be fine.

 

A reasonable charge regime similar to what a clever charger would be doing anyway.

 

Gibbo

 

Thanks for that, it's reassuring that I need no longer lie awake at night, worrying about the tears in which it'll all end

 

Tim