JACK FELL Posted February 4, 2017 Report Share Posted February 4, 2017 I HAVE JUST PURCHASED A BANK OF NEW DEEP CYCLE BATTERIES. THEY ARE ATTACHED TO A MASTERVOLT INVERTER/CHARGER. ALL THE POSITIVE STRAPS ARE A DIAMETER OF APPROX. 16MM. I AM FITTING NEGATIVE STRAPS OF SAME DIAMETER EXCEPT FOR ONE (200mm long) WHICH IS IN MY TOOL BOX BUT IS ONLY APPROX 7MM DIAMETER. BEING ON THE NEGATIVE SIDE OF THE CIRCUIT IS THIS GOING TO BE DETRIMENTAL?? Link to comment Share on other sites More sharing options...
MHS Posted February 4, 2017 Report Share Posted February 4, 2017 (edited) It is better to have all cables of the same size and length. How big is your battery bank? Do you know what size your cables are in mm2? Sound like 35mm2. Your smaller cable sounds much too small and will potentially be dangerous. Edited February 4, 2017 by MHS Link to comment Share on other sites More sharing options...
WotEver Posted February 4, 2017 Report Share Posted February 4, 2017 ... IS THIS GOING TO BE DETRIMENTAL?? YES. Link to comment Share on other sites More sharing options...
nicknorman Posted February 4, 2017 Report Share Posted February 4, 2017 (edited) I HAVE JUST PURCHASED A BANK OF NEW DEEP CYCLE BATTERIES. THEY ARE ATTACHED TO A MASTERVOLT INVERTER/CHARGER. ALL THE POSITIVE STRAPS ARE A DIAMETER OF APPROX. 16MM. I AM FITTING NEGATIVE STRAPS OF SAME DIAMETER EXCEPT FOR ONE (200mm long) WHICH IS IN MY TOOL BOX BUT IS ONLY APPROX 7MM DIAMETER. BEING ON THE NEGATIVE SIDE OF THE CIRCUIT IS THIS GOING TO BE DETRIMENTAL?? YES Oh and 16mm is too small unless your mastervolt Combi is a very small one. Oh but wait a minute, you say diameter, do you mean diameter? Normally we talk about the cross sectional area of the cable (not including the insulation. So can you be more precise - 16mm diameter or area? Including or excluding the insulation? Edited February 4, 2017 by nicknorman Link to comment Share on other sites More sharing options...
MtB Posted February 4, 2017 Report Share Posted February 4, 2017 I HAVE JUST PURCHASED A BANK OF NEW DEEP CYCLE BATTERIES. THEY ARE ATTACHED TO A MASTERVOLT INVERTER/CHARGER. ALL THE POSITIVE STRAPS ARE A DIAMETER OF APPROX. 16MM. I AM FITTING NEGATIVE STRAPS OF SAME DIAMETER EXCEPT FOR ONE (200mm long) WHICH IS IN MY TOOL BOX BUT IS ONLY APPROX 7MM DIAMETER. BEING ON THE NEGATIVE SIDE OF THE CIRCUIT IS THIS GOING TO BE DETRIMENTAL?? NO NEED TO SHOUT... As others have said, yes, but how detrimental depends on the maximum inverter power you will ever use. What rating is it? Welcome to the forum, by the way! Link to comment Share on other sites More sharing options...
Guest Posted February 4, 2017 Report Share Posted February 4, 2017 NO NEED TO SHOUT... As others have said, yes, but how detrimental depends on the maximum inverter power you will ever use. What rating is it? Welcome to the forum, by the way! He wasn't shouting he was typing in block capitals. Much easier to read on a phone screen with mince pies like mine. Yes welcome to the forum. Link to comment Share on other sites More sharing options...
WotEver Posted February 4, 2017 Report Share Posted February 4, 2017 He wasn't shouting he was typing in block capitals. But that is the equivalent of SHOUTING... Link to comment Share on other sites More sharing options...
cereal tiller Posted February 4, 2017 Report Share Posted February 4, 2017 But that is the equivalent of SHOUTING... SHUSH ! Link to comment Share on other sites More sharing options...
Guest Posted February 4, 2017 Report Share Posted February 4, 2017 But that is the equivalent of SHOUTING... It used to be. With more people using phones these days, many things will change. Replies will tend to be more curt too, like this one Link to comment Share on other sites More sharing options...
MtB Posted February 4, 2017 Report Share Posted February 4, 2017 It used to be. With more people using phones these days, many things will change. Replies will tend to be more curt too, like this one Disagree. Lots of people read this forum and post without using caps. It's not necessary and its poor internet etiquette. Link to comment Share on other sites More sharing options...
Guest Posted February 4, 2017 Report Share Posted February 4, 2017 (edited) Disagree. Lots of people read this forum and post without using caps. It's not necessary and its poor internet etiquette. To disagree is your privilege. Maybe not necessary for you, but not everybody has eyes like mine. Many things are poor "internet Etiquette" yet this one gets picked on with boring monotony. Why? Edited February 4, 2017 by Guest Link to comment Share on other sites More sharing options...
MHS Posted February 4, 2017 Report Share Posted February 4, 2017 (edited) YES Oh and 16mm is too small unless your mastervolt Combi is a very small one. Oh but wait a minute, you say diameter, do you mean diameter? Normally we talk about the cross sectional area of the cable (not including the insulation. So can you be more precise - 16mm diameter or area? Including or excluding the insulation? I'm assuming they're 16mm diameter including insulation, so say 12mm diameter copper. That's approx 35mm2. So the single 7mm diameter cable is say 5mm diameter copper or approx 15mm2. Definitely not going to be sufficient. Edited February 5, 2017 by MHS Link to comment Share on other sites More sharing options...
PaulJ Posted February 4, 2017 Report Share Posted February 4, 2017 This picture shows why you really dont want to use undersized cables on an inverter. Cables are 25mm squared, was fused (way too big a fuse ) , tidily installed and had even been in use for quite a while. I would check the manual (should be easy to find one on the Mastervolt site) and follow Mastervolts install instructions for your size of inverter. Link to comment Share on other sites More sharing options...
MtB Posted February 4, 2017 Report Share Posted February 4, 2017 I'm assuming they're 16mm diameter including insulation, so say 12mm diameter copper. That's approx 35mm2. So the single 7mm diameter cable is say 5mm diameter copper or approx 15mm2. Definitely. It going to be sufficient. Actually its impossible to say without knowing the maximum current the link will carry, and the voltage drop the user finds acceptable. Link to comment Share on other sites More sharing options...
stegra Posted February 4, 2017 Report Share Posted February 4, 2017 This picture shows why you really dont want to use undersized cables on an inverter. Cables are 25mm squared, was fused (way too big a fuse ) , tidily installed and had even been in use for quite a while. I would check the manual (should be easy to find one on the Mastervolt site) and follow Mastervolts install instructions for your size of inverter. You're not kidding! Link to comment Share on other sites More sharing options...
MHS Posted February 5, 2017 Report Share Posted February 5, 2017 (edited) Actually its impossible to say without knowing the maximum current the link will carry, and the voltage drop the user finds acceptable. I have edited my previous post. Auto correct managed to add a full stop and remove one important word "Not" BSS recommends 25mm2 as a minimum. No point going smaller than that. Edited February 5, 2017 by MHS Link to comment Share on other sites More sharing options...
The Bagdad Boatman (waits) Posted February 5, 2017 Report Share Posted February 5, 2017 Try to make all your straps the same length. They can go the shortest way and work the first battery too hard. Link to comment Share on other sites More sharing options...
Chewbacka Posted February 5, 2017 Report Share Posted February 5, 2017 The op described his cable as 7mm diameter. Assuming that is the copper diameter it will be 35mm2. The max current capacity of that cable depends upon how good the ventilation is and the ambient temperature - cable current rating is based upon the cable overheating. Anyway assuming it is in the engine space which is warm to hot and assuming the cable is in free air, I would guess the max current will be about 80A. 80A at 12V is 960W, so an inverter over 1000W will overload the cable, not to mention the other DC loads on your boat. You need to consider if the cable is big enough. Also the main fuse must be below the 'weakest' cable capacity in your circuit, so check that as well. Link to comment Share on other sites More sharing options...
Keeping Up Posted February 5, 2017 Report Share Posted February 5, 2017 The op described his cable as 7mm diameter. Assuming that is the copper diameter it will be 35mm2. The max current capacity of that cable depends upon how good the ventilation is and the ambient temperature - cable current rating is based upon the cable overheating. Anyway assuming it is in the engine space which is warm to hot and assuming the cable is in free air, I would guess the max current will be about 80A. 80A at 12V is 960W, so an inverter over 1000W will overload the cable, not to mention the other DC loads on your boat. You need to consider if the cable is big enough. Also the main fuse must be below the 'weakest' cable capacity in your circuit, so check that as well. This seems an unduly pessimistic rating, even in a poorly ventilated engine space, given that 35 Sq mm cable is nominally rated at 240 amps. Link to comment Share on other sites More sharing options...
JACK FELL Posted February 5, 2017 Author Report Share Posted February 5, 2017 GOOD DAY TO ALL RESPONDENTS, THANKS FOR ALL THE RESPONSES TO MY QUESTION RE. BATTERY STRAPS. I LIVE AND LEARN!! SOOOO, 1) TO MIKE THE BOILERMAN. I EXPECTED MOST, IF NOT ALL, THE RECIPIENTS OF MY QUERY WOULD BE BOATERS AND IF AN UPPER CASE CORRESPONDENCE WITHOUT EXPLETIVES IS YOUR WORST EXPERIENCE THEN YOU ARE DOING VERY WELL YES, CATWEASEL, YOU ARE RIGHT LOTS OF SMALL SCREENS BEING USED. 2) THANKS TO ALL WHO GAVE A POSITIVE NO NONSENSE "DON'T DO IT" REPLY. PROBLEM NOW SORTED. Link to comment Share on other sites More sharing options...
Guest Posted February 5, 2017 Report Share Posted February 5, 2017 GOOD DAY TO ALL RESPONDENTS, THANKS FOR ALL THE RESPONSES TO MY QUESTION RE. BATTERY STRAPS. I LIVE AND LEARN!! SOOOO, 1) TO MIKE THE BOILERMAN. I EXPECTED MOST, IF NOT ALL, THE RECIPIENTS OF MY QUERY WOULD BE BOATERS AND IF AN UPPER CASE CORRESPONDENCE WITHOUT EXPLETIVES IS YOUR WORST EXPERIENCE THEN YOU ARE DOING VERY WELL YES, CATWEASEL, YOU ARE RIGHT LOTS OF SMALL SCREENS BEING USED. 2) THANKS TO ALL WHO GAVE A POSITIVE NO NONSENSE "DON'T DO IT" REPLY. PROBLEM NOW SORTED. Those are the main points. Thanks for the conclusion, many people don't bother. Link to comment Share on other sites More sharing options...
Chewbacka Posted February 5, 2017 Report Share Posted February 5, 2017 (edited) This seems an unduly pessimistic rating, even in a poorly ventilated engine space, given that 35 Sq mm cable is nominally rated at 240 amps. According to AEI 2 cables close together in free air are rated at 162A, But at an ambient temperature of 60C the current should be derated by 0.5 giving 81A. Obviously this is a continuous rating which is not probable on a boat, and 60C is possibly a bit high for the engine compartment, in which case the op can adjust up if justified. http://www.aeicables.co.uk/literature/CurrentRatings.pdf Edited February 5, 2017 by Chewbacka Link to comment Share on other sites More sharing options...
MHS Posted February 5, 2017 Report Share Posted February 5, 2017 The op described his cable as 7mm diameter. Assuming that is the copper diameter it will be 35mm2.. Area of a circle is 2x radius x pi (or diameter x pi) So it would be 7x 3.1415 = 22m2 Link to comment Share on other sites More sharing options...
MtB Posted February 5, 2017 Report Share Posted February 5, 2017 Area of a circle is 2x radius x pi (or diameter x pi) So it would be 7x 3.1415 = 22m2 Which skool did you go to?!! 1 Link to comment Share on other sites More sharing options...
David Mack Posted February 5, 2017 Report Share Posted February 5, 2017 Area of a circle is 2x radius x pi (or diameter x pi) So it would be 7x 3.1415 = 22m2 No, that's the circumference. Area is πr2 Link to comment Share on other sites More sharing options...
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