Numax Charger "Keep Connected"?

[NorthwichTrader]

I've bought this charger from eBay

 

http://www.ebay.co.uk/itm/161020578241?ru=http%3A%2F%2Fwww.ebay.co.uk%2Fsch%2Fi.html%3F_from%3DR40%26_sacat%3D0%26_nkw%3D161020578241%26_rdc%3D1

 

Would it come to any harm if I bolted it to the batteries, keeping it permenantly connected?

 

If, no, could I leave it permenantly switched on, or would it be best to unplug it for engine start-up?

 

Many thanks,

Stuart

[by'eck]

Absolutely not as long as you don't actually bolt it to the batteries

[Tony Brooks]

One small caveat. If you suspect a cell might be starting to short out/fail I would advise that you only have it turned on while you are in attendance. That way you will notice the tarnished brass and "bad eggs" smell before the cell explodes.

[Phil Ambrose]

We have always had our Numax connected, hard wired so to speak, it was advertised as being fit and forget. I should add we live aboard and I do check my batteries on a very regular basis, topping up, checking the SG etc etc.

Phil

[Kae]

Mine is hard wired to the 12v electrics for both leisure and starter bank (correctly fused too).

No problem at all and when I'm on shorepower, I use it as a "fit and forget" charger.

[John Williamson 1955]

I've got a similar one hard wired to my leisure batteries, but there's a fuse (for safety) and a switch in the circuit just in case. I turn the switch off before I start the engine partly for my own peace of mind, but also because if I don't it gets confused and sulks when it gets plugged back into the shore supply.

[ditchcrawler]

I've bought this charger from eBay

 

http://www.ebay.co.uk/itm/161020578241?ru=http%3A%2F%2Fwww.ebay.co.uk%2Fsch%2Fi.html%3F_from%3DR40%26_sacat%3D0%26_nkw%3D161020578241%26_rdc%3D1

 

Would it come to any harm if I bolted it to the batteries, keeping it permenantly connected?

 

If, no, could I leave it permenantly switched on, or would it be best to unplug it for engine start-up?

 

Many thanks,

Stuart

I do hope you have a 24 volt system

[PaulG]

I've bought this charger from eBay

 

http://www.ebay.co.uk/itm/161020578241?ru=http%3A%2F%2Fwww.ebay.co.uk%2Fsch%2Fi.html%3F_from%3DR40%26_sacat%3D0%26_nkw%3D161020578241%26_rdc%3D1

 

Would it come to any harm if I bolted it to the batteries, keeping it permenantly connected?

 

If, no, could I leave it permenantly switched on, or would it be best to unplug it for engine start-up?

 

Many thanks,

Stuart

Personally I would replace the croc clips with some ring terminals and connect to the battery posts.

Mount the charger as close to your batteries as is practically possible.

I'd also install an inline fuse in the +24V line, (or both if you want to, they're cheap enough). Mount the fuses so that they are easily accessible.

Make sure that the DC cables are as short as possible and clipped up at intervals so that the insulation can't chafe though with engine vibration.

If you're not familiar with soldering, you can get crimp terminals in various sizes to suit the cable size.

If in doubt, get an electrician to do it for you.

Personally I always turn my charger off before starting the engine. May not be necessary, but could be expensive to discover otherwise!

[nebulae]

I have one of these chargers. If the charger is left connected permanently and the boat is left unattended for a few weeks,with the mains not connected,it does seem to drain the batteries.Should it do this?.(Mine was supplied by Midland Chandlers)

[richardf]

Mine doesn't do this

[Phil Ambrose]

Nor does mine.

Phil

[Kae]

Mine neither. There is no current flow in the charger leads when the charger itself is switched off (verified with a DC clamp meter).

[nebulae]

Thanks for the reasurance .Will try again. I now wonder if there was another reason why the batteries discharged!

[NorthwichTrader]

Wow, and thank-you for that response, brilliant!

Can I ask what size fuses would you fit? Is one in each cable best?

Thanks again,

Stuart

[smileypete]

Nearest available size above 12A, in the positive, at the battery end. 15A blade fuse would do nicely.

 

If charge current metering is wanted then a self contained ammeter could be added, something like:

 

http://cpc.farnell.com/hobut/f3pam602-20a/ammeter-0-to-20a/dp/PM11550?Ntt=PM11550

http://www.ebay.co.uk/itm/Ammeter-12A-Black-1-3-4-BSA-Triumph-AJS-Norton-/131039455284 (not cheap but nice for vintage eng panel )

 

Thanks for the reasurance .Will try again. I now wonder if there was another reason why the batteries discharged!

 

A DC clamp ammeter/multimeter (aka 'clamp meter') may help:

 

http://www.canalworld.net/forums/index.php?showtopic=69198&page=3#entry1378873

 

One small caveat. If you suspect a cell might be starting to short out/fail I would advise that you only have it turned on while you are in attendance. That way you will notice the tarnished brass and "bad eggs" smell before the cell explodes.

 

Good point, though one thing about 24v is that if a cell goes short, the others only get about 10% over voltage instead of 20% with a 12V setup. Still not ideal but not so bad.

 

cheers, Pete.

~smpt~

Edited September 2, 2014 by smileypete

[NorthwichTrader]

Nearest available size above 12A, in the positive, at the battery end. 15A blade fuse would do nicely.

 

If charge current metering is wanted then a self contained ammeter could be added, something like:

 

http://www.ebay.co.uk/itm/Ammeter-12A-Black-1-3-4-BSA-Triumph-AJS-Norton-/131039455284

 

cheers, Pete.

~smpt~

Thanks, Pete, Norton Ammeter purchased!

When you say battery end for the the fuse, I'm taking that you mean somewhere between the battery and the charger? Or are you meaning, 'get that fuse as close to the battery terminal as is practical? On the wire from the charger to the battery, of course?

A bit late to ask now, but what information and diagnoses/observations can I determine from this ammeter?

[smileypete]

Thanks, Pete, Norton Ammeter purchased!

When you say battery end for the the fuse, I'm taking that you mean somewhere between the battery and the charger? Or are you meaning, 'get that fuse as close to the battery terminal as is practical? On the wire from the charger to the battery, of course?

A bit late to ask now, but what information and diagnoses/observations can I determine from this ammeter?

 

Well, as near to the batt end of the charger positive cable as practicable, but not in the batt box itself due to risk of explosive batt gases.

 

With the ammeter, if there's no loads on but reading stays high and doesn't tail off, it could be a batt is failing as Tony pointed out in post #3, in which case it's well worth checking things further, like batts getting rather warm and/or excessive need for topping up.

 

Probably not such a big danger with a 12A charger, but put a high power charge source on like a big alt or solar controller, and the batts could really cook.

 

cheers, Pete.

~smpt~

Edited September 2, 2014 by smileypete

[NorthwichTrader]

Thanks, Pete, I get it...so what might it read whilst the batteries are on full charge, and what might I be looking for when they are in standby/float AND in good condition?

Sorry to winkle out every detail...it's so much easier for me to move on, once I've tied up the brain niggles and boxed it away!

Very many thanks,

Stuart

[smileypete]

Thanks, Pete, I get it...so what might it read whilst the batteries are on full charge, and what might I be looking for when they are in standby/float AND in good condition?

Sorry to winkle out every detail...it's so much easier for me to move on, once I've tied up the brain niggles and boxed it away!

Very many thanks,

Stuart

 

No problem, when in good nick the current should tail off to to less than 1-2% of capacity in Ah.

 

cheers, Pete.

~smpt~

Edited September 2, 2014 by smileypete

[NorthwichTrader]

Thanks, Pete,

So, to ease my aching head, IF I had 2 x 100 Ah batteries, I'd have 200 Ah (would I?) at 24v which, in good condition and on float charge, should read around 2-4 amps on my ammeter...is that correct?

Also, how would i fit this meter into my system, as it is so far? Which, 240 aside, consists of 2 x 12v batteries (24v), a starter motor, and an earth strap, with soon to add a hard-wired numax charger (until we get organised for a combi unit)!

[smileypete]

Should read less than 2-4 amps when fully charged for 200Ah, probably much less for new batts in practice but may go up as batts age.

 

Ammeter can go in the positive batt charger lead, probably has 1/4" blade terminals that take matching female crimp connectors.

 

cheers, Pete.

~smpt~

Edited September 3, 2014 by smileypete

[NorthwichTrader]

You're brilliant, Pete, thank-you so much! I owe so many people a beer on here! I wish it were possible!

[nicknorman]

Thanks, Pete,

So, to ease my aching head, IF I had 2 x 100 Ah batteries, I'd have 200 Ah (would I?) at 24v which, in good condition and on float charge, should read around 2-4 amps on my ammeter...is that correct?

Also, how would i fit this meter into my system, as it is so far? Which, 240 aside, consists of 2 x 12v batteries (24v), a starter motor, and an earth strap, with soon to add a hard-wired numax charger (until we get organised for a combi unit)!

If you have 2 x 12v 100AH batteries in series to give 24v, you still have 100AH total. Although of course in terms of energy storage, 100AH at 24v is "worth" twice 100AH at 12v. If you 2x24v 100AH batteries in parallel, you have 200AH.

 

Regarding the ammeter reading, when the charger goes to float mode at the end of the charge period, its voltage will drop to around 13.25 volts and in that mode, the charge current will be virtually zero. Just before it goes into float mode (at the end of the absorption phase) it should be reading an amp or so which indicates the batteries are fully charged. Some chargers (don't know if this one is like this) have a habit of going in to float prematurely and never really fully charging the batteries, at least not until many hours or days at float, so it will be worth getting a handle on the current at which the charger changes to float.

[PaulG]

If you 2x24v 100AH batteries in parallel, you have 200AH.

That's not quite right in practice.

 

If you use the "50% discharge rule" you actually get more capacity than you would expect from summing the capacity of the individual batteries, due to our old friend Mr Peukert:

 

http://www.smartgauge.co.uk/morepeukert.html

[nicknorman]

That's not quite right in practice.

 

If you use the "50% discharge rule" you actually get more capacity than you would expect from summing the capacity of the individual batteries, due to our old friend Mr Peukert:

 

http://www.smartgauge.co.uk/morepeukert.html

Not really true in practice. Firstly because in general the intervals between charge are long enough such that if the average discharge current is taken over say 20 hrs, it is low. Doubling the bank size makes it even lower but due to the fact the Peukert is an exponential formula, the difference is minute. You are on a very flat part of the curve. And secondly because Peukert doesn't affect the ultimate battery capacity. If you take a high current out for a short time (boiling an electric kettle say), once that process is over Peukert doesn't mean you have used up more capacity than if you took the same charge out but much more slowly. The "lost" charge is still in there, it just takes some time to get it out.

 

Peukert only affects the time to run to flat presuming the discharge rate is maintained until that point. If a high current is maintained until "flat" and the batteries then left for a few hours, the "lost" charge will be recovered eventually.