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Wiring up a battery charger indirectly

dankenning

By dankenning
in Boat Equipment

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dankenning Engager

dankenning

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I've just bought a 10a battery charger (thanks for your help choosing one). I was about to embark on wiring it up through the bulkhead to the battery bank next to the engine but ran out of light. Then I thought why not connect it directly to the battery cables inside the boat which are right next to the charger. Is there any reason why I can't do this, the battery cables are much bigger than I needed and connect to opposing sides of the bank. Thanks in advance for bmx advice.

 

Sorry, should read any advice, i'm writing from a phone.

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I've just bought a 10a battery charger (thanks for your help choosing one). I was about to embark on wiring it up through the bulkhead to the battery bank next to the engine but ran out of light. Then I thought why not connect it directly to the battery cables inside the boat which are right next to the charger. Is there any reason why I can't do this, the battery cables are much bigger than I needed and connect to opposing sides of the bank. Thanks in advance for bmx advice.

 

Sorry, should read any advice, i'm writing from a phone.

Exactly how my charger is wired: Back fed through the main battery cables with a suitable fuse incorporated. Minimal volt drop,less cable hanging around. Been good for 7 years now.

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Thanks for the reply. Can you tell me where the fuse is fitted?

The fuse is fitted in the positive cable from the charger output (thinner cable), where it terminates to the much thicker cable. This protects the charger wiring in the event of a fault.

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blackrose Veteran II

blackrose

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The fuse is fitted in the positive cable from the charger output (thinner cable), where it terminates to the much thicker cable. This protects the charger wiring in the event of a fault.

 

Shouldn't the fuse be fitted as close to the batteries as possible/practical?

Edited by blackrose
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Shouldn't the fuse be fitted as close to the batteries as possible/practical?

I wired mine thus:

Large cable via 250 Amp megalink fuse from battery via isolator to consumer unit. The positive and negative charger wires join the large battery cables at the consumer unit. The smaller positive charger cable has a suitable fuse wired in. My reasoning is that the 250 Amp megalink will protect the large battery cable in the event of a fault. The smaller charger cable is protected by a suitable fuse, and NOT the megalink (my charger fuse is 45A IIRC.) By back feeding down the large cable I am avoiding volt drop and unnecessary cables.

 

I agree the battery cable should be fused as near to the battery as possible.

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The fuses needs matching to the thinner ones.

Aye true. It is the cables that need protecting. Electronic devices will fail long before the fuse has popped.

 

In this instance the fuse at the charger end needs to protect the charger cable,the fuse at the battery end needs to protect the battery cable (otherwise it wouldn't be possible to draw a decent current from the batteries.)

 

Sorry about crap drawing,but this is how I wired my 30Amp charger.

Edited forgot to show isolator, which is between 150 Amp fuse and battery.

 

setup.jpg

Edited by Guest
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blackrose Veteran II

blackrose

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You only have two fuses there because you have 2 different size cables, is that right?

 

My Sterling came with a big fuse in a perspex box for the negative side which is connects thick and thin cables at the charger connection - I'm not really sure what it's for? I also put 50 amp fuses in each output cable near the batteries.

 

I don't know how far the OP is thinking of connecting his charger from the batteries, but if he's doing it indirectly like you will any extra distance result in any voltage drop or will the thicker cables he's connecting to compensate? I ask as it's only a 10amp charger so he'd want to get everything he can from it.

Edited by blackrose
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You only have two fuses there because you have 2 different size cables, is that right?

 

My Sterling came with a big fuse in a perspex box for the negative side which is connects thick and thin cables at the charger connection - I'm not really sure what it's for? I also put 50 amp fuses in each output cable near the batteries.

Yes Mike, the charger is effectively back feeding down the large battery cable. I could see no point in running from the cabin, all the way back to the batteries with a fresh cable, when there is a huge one just below the consumer unit, right next to the charger. I simply connected the charger to that busbar (via a fuse of course.)

 

Hopefully Gibbo will confirm or otherwise, but IIRC the negative fuse is for the USA market. In the UK we don't normally fuse in the negative side; unless things have changed of course! (It is 7 years since I wired our boat.)

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blackrose Veteran II

blackrose

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Right, it's wired up, humming away and the voltage is slowly climbing. I connected the positive to the protected side of the mega fuse (from the batteries) via an in line car type fuse. The negative is connected to the main negative busbar. Thanks for your help.

 

The humming is probably the cooling fan (assuming it has one). Once it's gone onto float that should stop.

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