Battery charger

[richardf]

Last year a bought a cheapish 30A Numax charger - it has performed well just connected to my leisure batteries (2), but there looks to be a spare connection and it has been suggested (in the absence of instructions!) that this can be connected to the starter battery.

 

I only have a vague understanding of chargers, but I was under the impression that the charging current varied with relation to the state of the batteries. So if I have one set nicely charged and (say) the starter battery needing charge badly, how does the charger compensate for this - is there no way it can overcharge the other bank?

[Nickhlx]

Last year a bought a cheapish 30A Numax charger - it has performed well just connected to my leisure batteries (2), but there looks to be a spare connection and it has been suggested (in the absence of instructions!) that this can be connected to the starter battery.

 

I only have a vague understanding of chargers, but I was under the impression that the charging current varied with relation to the state of the batteries. So if I have one set nicely charged and (say) the starter battery needing charge badly, how does the charger compensate for this - is there no way it can overcharge the other bank?

 

I would say that if separate terminals exist then it will be safe to connect and will "manage" things correctly - sooner or later someone will connect up both and I am sure that they would either make it very plain that this shouldn't be done if it couldn't cope, or there would be some sort of circuit within to prevent damage. If in doubt you could connect up the starter battery via a fuse - e.g. a 5A one - as it is possibly a low / trickle charge of around 13.8V at up to 2A which could be left on for a long period without damage, especially on wet cell lead acids.

 

 

Perhaps a manual is downloadable on-line, or ring one of the distributors ?

 

Nick

Edited March 2, 2012 by Nickhlx

[jonathanA]

there was another thread about chargers and someone said they had a numax charger - might be worth a PM to that poster for a copy of the relevant bit of the manual or some advice at least.

 

thread was http://www.canalworld.net/forums/index.php?showtopic=44951 if this works

[blackrose]

Last year a bought a cheapish 30A Numax charger - it has performed well just connected to my leisure batteries (2), but there looks to be a spare connection and it has been suggested (in the absence of instructions!) that this can be connected to the starter battery.

 

I only have a vague understanding of chargers, but I was under the impression that the charging current varied with relation to the state of the batteries. So if I have one set nicely charged and (say) the starter battery needing charge badly, how does the charger compensate for this - is there no way it can overcharge the other bank?

 

If your charger has 2 output terminals then you should connect one to your domestic battery bank and the other to your start battery. Assuming this is a proper 3 stage marine battery charger it will not overcharge or undercharge either bank.

 

However, if you only want to charge one battery bank (in this case your domestics), you should link both terminals together and connect the combined terminals to your domestic bank. You shouldn't leave an output terminal unconnected. This is also the case for battery chargers with 3 output terminals - link all three together and connect it to the single bank you want to charge.

 

By only connecting one of the output terminals to the domestic bank and leaving the other one(s) unconnected, you won't be using your charger to it's optimum efficiency.

Edited March 2, 2012 by blackrose

[smileypete]

Last year a bought a cheapish 30A Numax charger - it has performed well just connected to my leisure batteries (2), but there looks to be a spare connection and it has been suggested (in the absence of instructions!) that this can be connected to the starter battery.

I wouldn't assume there's two independent outputs, the terminals could be connected together internally.

 

The charger cable(s) should be fused at the battery end, to the cable rating or charger output, whichever is lower.

 

Think this one through, carefully

 

Do you just want to maintain the starter battery while you're away, and are there any loads like bilge pumps connected to it?

 

cheers,

Pete.

Edited March 3, 2012 by smileypete

[blackrose]

I wouldn't assume there's two independent outputs, the terminals could be connected together internally.

 

 

Why would Numax do that Pete? Wouldn't that be the same as manufacturing the charger with one terminal?

[Arthur Brown]

Seriously I'd suggest that you read the manual! If it didn't come with one then look for a download! The connectors may be different chargers that you can parallel for one batery or separate for two batteries.

[smileypete]

Why would Numax do that Pete? Wouldn't that be the same as manufacturing the charger with one terminal?

Well, they certainly could.

 

I guess a diode/continuity/resistance check across the two +ve terminals with the charger fully disconnected might shed some light.

 

There's been a couple of threads about this but no definitive answer so far...

 

cheers,

Pete.

Edited March 3, 2012 by smileypete