Sterling Battery Charger - temporarily adding a 4th battery?

[AndrewPalmer]

I have an inboard fitted Sterling battery charger with three outputs, and charging the engine, domestic and bow thruster batteries. It's a fancy piece of kit, and I understand it is carefully monitoring and charging the three batteries individually as required. I have recently acquired a second hand electric outboard, it's the simple 12V trolling type, not a fancy high powered lithium unit. Rather than bringing a separate battery charger to top up the outboard battery on board, I thought that I would be able to wire it into one of the existing battery charging outputs with an Andersen plug. My thinking was that although the battery characteristics would not the the same as whichever I added it to, the system would just treat it as an extra cell, and recognise the need to start charging and then stop when fully charged. As it would only be connected temporarily I did not see an issue with messing up the longer term automatic charging routine of the inboard battery. I was surprised however that immediately on connecting the extra battery, it blew the inline 10A fuse (I tried again with the same effect).

Can anyone advise what I am doing wrong? Maybe adding another battery in this way is just a complete no no?

 

[Alex_Blackwood]

I have an inboard fitted Sterling battery charger with three outputs, and charging the engine, domestic and bow thruster batteries. It's a fancy piece of kit, and I understand it is carefully monitoring and charging the three batteries individually as required. I have recently acquired a second hand electric outboard, it's the simple 12V trolling type, not a fancy high powered lithium unit. Rather than bringing a separate battery charger to top up the outboard battery on board, I thought that I would be able to wire it into one of the existing battery charging outputs with an Andersen plug. My thinking was that although the battery characteristics would not the the same as whichever I added it to, the system would just treat it as an extra cell, and recognise the need to start charging and then stop when fully charged. As it would only be connected temporarily I did not see an issue with messing up the longer term automatic charging routine of the inboard battery. I was surprised however that immediately on connecting the extra battery, it blew the inline 10A fuse (I tried again with the same effect).

Can anyone advise what I am doing wrong? Maybe adding another battery in this way is just a complete no no?

From the information you have given, which is minimal to say the least, I would hazard a guess that you have been sold a duff battery. Hope it wasn't a fellow club member!! I am assuming that the fuse referred to is in the charging circuit for the battery and not the power supply to the charger??
However as you haven't said what model of charger you have, what type or size of batteries you have. Where or what fuse you refer to, or how exactly you have made the connections. Perhaps a couple of pics. or a quick sketch would help. The above suggestion is a total guess but I would suspect the battery for the OB. Assuming that what connections you made were OK.
Edit: I wouldn't recommend what you are attempting in any case. I would suggest a separate charger or possibly a Battery to Battery charger from one of your existing batteries.

 

[PaulRainbow]

I have an inboard fitted Sterling battery charger with three outputs, and charging the engine, domestic and bow thruster batteries. It's a fancy piece of kit, and I understand it is carefully monitoring and charging the three batteries individually as required.

It doesn't work like that. It's a single charger, separated by some diodes.

I have recently acquired a second hand electric outboard, it's the simple 12V trolling type, not a fancy high powered lithium unit. Rather than bringing a separate battery charger to top up the outboard battery on board, I thought that I would be able to wire it into one of the existing battery charging outputs with an Andersen plug. My thinking was that although the battery characteristics would not the the same as whichever I added it to, the system would just treat it as an extra cell, and recognise the need to start charging and then stop when fully charged. As it would only be connected temporarily I did not see an issue with messing up the longer term automatic charging routine of the inboard battery. I was surprised however that immediately on connecting the extra battery, it blew the inline 10A fuse (I tried again with the same effect).

Can anyone advise what I am doing wrong? Maybe adding another battery in this way is just a complete no no?

Alex's questions are pertinent, but, you should be able to add an additional battery.

Turn the charger off and disconnect the easiest battery, connect the outboard battery in its place (make sure you observe the battery polarity), turn the charger back on. If a fuse blows the battery is faulty.

 

[B27]

I'd suggest re-checking the polarity of the additional battery.
I'd expect an expensive charger to current limit?

If the additional battery is very flat, then you could try charging it via a 12v bulb initially to limit the current until it's got some volts.

 

[PaulRainbow]

I'd suggest re-checking the polarity of the additional battery.
I'd expect an expensive charger to current limit?

It doesn't know how many batteries are connected, it can't limit current based on one battery in a bank.

If the additional battery is very flat, then you could try charging it via a 12v bulb initially to limit the current until it's got some volts.

Why would you limit the current, don't you want to charge it ?

 

[B27]

You'd limit the current to avoid blowing the fuse. Put a few Ah into the battery and check that it actually looks like a 12V battery not a 10V battery because it's got a shorted cell or something.

The DC output fuses are supposed to be 20% bigger than the charger max output?
So the charger should not blow the fuse? As you say the charger doesn't know what batteries are connect, nor does it know what loads are connected to the batteries. What happens with one of these chargers if you pull 200A into a microwave while the charger is on? Does the fuse blow or does the charger current limit?

Poking the new battery with a voltmeter should be the first thing. If it's much below 12v, trickle charge it before slapping it into the system.

I assume the OP turned off the charger before connecting the battery? Did the fuse blow when connecting the battery or when turning the charger back on?
If the fuse is simply less than the charger's max output, then no surprise it's blown with a flat battery connected, quite possible the fuse has been OK in normal use.

 

[PaulRainbow]

You'd limit the current to avoid blowing the fuse. Put a few Ah into the battery and check that it actually looks like a 12V battery not a 10V battery because it's got a shorted cell or something.

The charger is fused to allow it to output it's max rated charge current. The charger will also not be bothered if the battery has a shorted cell, it will see that as a flat battery and try to charge it at max current. The battery won't like it, it will boil and gas, but the charger won't blow any fuses.

The DC output fuses are supposed to be 20% bigger than the charger max output?
So the charger should not blow the fuse? As you say the charger doesn't know what batteries are connect, nor does it know what loads are connected to the batteries. What happens with one of these chargers if you pull 200A into a microwave while the charger is on? Does the fuse blow or does the charger current limit?

The microwave isn't connected to the batteries, it's 240v AC. The only way that can pull 200a from the batteries is by using an inverter and the charger won't care one little bit about 200a being drawn from the batteries, or even 300a, or more. It will put out it's max charging current and no fuses will blow.

Poking the new battery with a voltmeter should be the first thing. If it's much below 12v, trickle charge it before slapping it into the system.

So you turn up to your boat and the batteries are low, you take them off, take them home and trickle charge them ?

Of course you don't.

I assume the OP turned off the charger before connecting the battery? Did the fuse blow when connecting the battery or when turning the charger back on?

we don't have that information, but a healthy battery will not blow the fuses when it's connected, whether the charger is on or off. If it worked like that the fuses would blow every time a heavy load is turned on.

If the fuse is simply less than the charger's max output, then no surprise it's blown with a flat battery connected, quite possible the fuse has been OK in normal use.

Something else you don't know.

You really need to stop posting this ill informed misinformation.

 

[B27]

So why do you think the fuse blew?

 

[William_H]

It is not clear to me just where this fuse is? If it is in the between the charger and the boats battery then as said that is strange.
If the fuse is in the cable connecting the new O/B battery to the boat's battery then the current between the batteries can be very large initially. The boat battery can deliver a lot of amps the o/b battery if flat can take a lot of amps. As said fit a lamp between the 2 batteries to limit the current. But as said most important is to know the state of the o/b battery before you connect it up to another battery. As said also the o/b battery may be very low in charge or low in voltage due to bad cell. ol'will

 

[PaulRainbow]

So why do you think the fuse blew?

I don't know, because i don't know where the fuse is that blew.

 

[Alex_Blackwood]

I don't know, because i don't know where the fuse is that blew.

As I said originally. We don't have enough info. We can assume what we like from the OP but we are only guessing. I would go no further than Pauls original suggestion. It is second hand equipment, the battery, not the charger! He could have a flooded LA battery that has dried out, or something else entirely.
Offering all sorts of advice could be counter productive if not downright dangerous without us knowing what we are advising on.
I think, with all due respect that ol' Will is wrong in his placing of the fuse. Again assumption, but but I had imagined that Andrew had connected the OB battery in parallel with one of his existing batteries at the the charger terminals. But did he??
As for the cause of the fuse blowing I would immediately suspect a dead, or very near dead short being applied. I would imagine that the charger has an overload protection device, probably thermal, which would protect the charger from normal overload. as opposed to fault. BUT!!
We could ask why the original owner sold the OB?
I would seriously suggest that we await Andrews response before flying anymore kites in the air

 

[B27]

Re-reading the OP, the blowing fuse is 10A?
If that's in the battery line it's too small. ( I assume these multi-output chargers are somewhat more than 10Amp?)
If it's the mains fuse, there's probably a fault in the charger?

 

[Alex_Blackwood]

Re-reading the OP, the blowing fuse is 10A?
If that's in the battery line it's too small. ( I assume these multi-output chargers are somewhat more than 10Amp?)
If it's the mains fuse, there's probably a fault in the charger?

Your flying another kite, speculating. Don't! He has never said that the charger was faulty with his boat batteries, only when he connected the OB battery. We don't know how or where he did that. As I said we are assuming, or could be assuming all sorts. We just do not know. Facts, stick with them

 

[B27]

If we take it as 'fact' that the blowing fuse is 10 Amp, 'fact is', the OP needs to RTFM and check it's the recommended value.

Sticking to the known facts will often make very short threads.
Speculation on a forum should be seen as possible things to look into or think about to understand the situation.

Obviously if the OP chose to fit a bigger fuse, then the whole installation might need checking for wire gauge etc.

Maybe some people would like an non-practical boat owner forum, it could auto-reply to all threads, 'Call an engineer!'

 

[Alex_Blackwood]

If we take it as 'fact' that the blowing fuse is 10 Amp, 'fact is', the OP needs to RTFM and check it's the recommended value.

Sticking to the known facts will often make very short threads.
Speculation on a forum should be seen as possible things to look into or think about to understand the situation.

Obviously if the OP chose to fit a bigger fuse, then the whole installation might need checking for wire gauge etc.

Maybe some people would like an non-practical boat owner forum, it could auto-reply to all threads, 'Call an engineer!'

At least we agree on that

 

[PaulRainbow]

If we take it as 'fact' that the blowing fuse is 10 Amp, 'fact is', the OP needs to RTFM and check it's the recommended value.

Sticking to the known facts will often make very short threads.
Speculation on a forum should be seen as possible things to look into or think about to understand the situation.

Obviously if the OP chose to fit a bigger fuse, then the whole installation might need checking for wire gauge etc.

Maybe some people would like an non-practical boat owner forum, it could auto-reply to all threads, 'Call an engineer!'

Some people would like a forum where people don't post misinformation, speculation or things that they have read on the internet and not properly understood.

Bit of an ask though.

 

[Alex_Blackwood]

Some people would like a forum where people don't post misinformation, speculation or things that they have read on the internet and not properly understood.

Bit of an ask though.

Andrew did ask "Can anyone advise what I am doing wrong" This has been at the back of my mind since first reading the OP. A genuine question, seriously not being funny. Or speculating
Did he by any chance connect the OB battery to the incoming ac terminals? I know, unlikely. However he wouldn't be the first or the last to have done something similar. Even I can admit to having got connections and terminals crossed Would be interesting to know.

 

[PaulRainbow]

Andrew did ask "Can anyone advise what I am doing wrong" This has been at the back of my mind since first reading the OP. A genuine question, seriously not being funny. Or speculating
Did he by any chance connect the OB battery to the incoming ac terminals? I know, unlikely. However he wouldn't be the first or the last to have done something similar. Even I can admit to having got connections and terminals crossed Would be interesting to know.

It's a shame he hasn't been back to the forums since asking for help.

 

[Alex_Blackwood]

It's a shame he hasn't been back to the forums since asking for help.

Can't blame him. It scares me!

 

[AndrewPalmer]

Thanks everyone, here is a (sorry rather blurry) picture of the charger, and one of the battery.

The battery is brand new, works fine and charges with my home car charger, so I don't think that is the problem. Also it was only slightly discharged when we connected it, I would say not more than 10-20% depleted.

I notice now though that the charger is 20A, I did not think that it would be that much, and perhaps not surprising therefore that it blew the 10A fuse!

It looks like everyone concurs that in principle there should be no problem with wiring a connection to charge a 4th battery concurrently alongside one of the other three?