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New Victron 12/1600/70 Inverter Charger


butty lark

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Just bought a new version of this inverter charger. The previous version had a 6 slot terminal block inside with the first two dedicated to + then - voltage sensing wire. Although there is now an 8 slot terminal block in the same place the first two slots are the temp sensing leaving the 6 remaining. Nowhere can I see any reference to this slot in the new manual, I am losing 0.35v across the connections to the battery and had been told "do it in software", not very helpful as it needs a PC and I have only a Mac. Any advice?

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Perhaps the answer is to address the fundamental problem of voltage drop in the wiring, rather than trying to compensate for it in some way. We have a Mastervolt Combi and it neither has nor needs remote voltage sensing.

 

You say you have 0.35v drop, but at what current is that? If it is at a very high current then fair enough, and it won't significant impact charging because as the current decreases as charging progresses, so does the voltage drop. If that voltage drop is at a modest current then you need to address the inadequate wiring. What is the size and length of the cabling between the batteries and inverter / charger?

Edited by nicknorman
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Perhaps the answer is to address the fundamental problem of voltage drop in the wiring, rather than trying to compensate for it in some way. We have a Mastervolt Combi and it neither has nor needs remote voltage sensing.

 

You say you have 0.35v drop, but at what current is that? If it is at a very high current then fair enough, and it won't significant impact charging because as the current decreases as charging progresses, so does the voltage drop. If that voltage drop is at a modest current then you need to address the inadequate wiring. What is the size and length of the cabling between the batteries and inverter / charger?

Charging is quite modest 90 amps max into 420 amphrs batt. have a 2.5m run from batts to charger and cannot reduce. Used 35mm cable and reduced connections to min. Could take out fuses otherwise little flexibility. Need to compensate. Worked fine on the old sterling. But tricky with the 21st centruy black box approach taken by Victron. Have to get a PC.

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35mm is too small for a 2.5m length (presumably 5m round trip) to a 1600w inverter. I'd use 70mm.

 

The thing is, the voltage drop you mention will only happen at that high initial charging current. As the batteries approach fully charged there will be less and less, and eventually virtually no voltage drop. So if you raise the voltage to cater for the drop at high current, you will end up with a high charge voltage towards the end of the charge which (depending on the type of battery and what the voltage actually is) might be a bad thing.

 

By using too small cable you waste power during charge and, perhaps more importantly, waste battery power when the inverter is working.

 

Edit: just checked the Victron manual, it recommends 70mm for 1.5 to 5 metre cable runs for your model of Combi.

Edited by nicknorman
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The thing is, the voltage drop you mention will only happen at that high initial charging current. As the batteries approach fully charged there will be less and less, and eventually virtually no voltage drop. So if you raise the voltage to cater for the drop at high current, you will end up with a high charge voltage towards the end of the charge which (depending on the type of battery and what the voltage actually is) might be a bad thing.

Thanks for saying that before I had a chance to

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35mm is too small for a 2.5m length (presumably 5m round trip) to a 1600w inverter. I'd use 70mm.

 

The thing is, the voltage drop you mention will only happen at that high initial charging current. As the batteries approach fully charged there will be less and less, and eventually virtually no voltage drop. So if you raise the voltage to cater for the drop at high current, you will end up with a high charge voltage towards the end of the charge which (depending on the type of battery and what the voltage actually is) might be a bad thing.

 

By using too small cable you waste power during charge and, perhaps more importantly, waste battery power when the inverter is working.

 

Edit: just checked the Victron manual, it recommends 70mm for 1.5 to 5 metre cable runs for your model of Combi.

Good point on rising voltage. Not sure how Victron expect to cope with this as they claim without a hard wire for battery sensing though.

Did the calcs some time ago. There is a lot of difference between a run of 1.5 and 5 m. At 2.5 m (round trip) my calcs showed a 0.1v drop at 90 amps and .05 amps at 40 amps. (The cable was 50mm. Not 35 as stated earlier.) It does go through a Mega fuse, and I guess I am losing volts across these connections especially if they get corroded. I will give it all a good clean. Not sure if the fuse is needed, most chargers are internally fused these days. Any comments?

Edited by butty lark
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35mm is too small for a 2.5m length (presumably 5m round trip) to a 1600w inverter. I'd use 70mm.

 

The thing is, the voltage drop you mention will only happen at that high initial charging current. As the batteries approach fully charged there will be less and less, and eventually virtually no voltage drop. So if you raise the voltage to cater for the drop at high current, you will end up with a high charge voltage towards the end of the charge which (depending on the type of battery and what the voltage actually is) might be a bad thing.

 

By using too small cable you waste power during charge and, perhaps more importantly, waste battery power when the inverter is working.

 

Edit: just checked the Victron manual, it recommends 70mm for 1.5 to 5 metre cable runs for your model of Combi.

Thanks. Good point on wasting battery power on inverter usage, it does seem overly heavy. I have work to do.

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Good point on rising voltage. Not sure how Victron expect to cope with this as they claim without a hard wire for battery sensing though.

Did the calcs some time ago. There is a lot of difference between a run of 1.5 and 5 m. At 2.5 m (round trip) my calcs showed a 0.1v drop at 90 amps and .05 amps at 40 amps. (The cable was 50mm. Not 35 as stated earlier.) It does go through a Mega fuse, and I guess I am losing volts across these connections especially if they get corroded. I will give it all a good clean. Not sure if the fuse is needed, most chargers are internally fused these days. Any comments?

No you should definitely fuse the +ve lead, preferably near the battery end. The Victron manual mentions the need for a fuse but anyway you don't want to have fat cable connected to battery +ve unfused. A short circuit would be catastrophic.

 

Do the cables go through some sort of battery isolator? If so, that may be a source of voltage drop and it is not necessary. The fused +ve cable can be connected direct to the battery +ve.

 

Battery sensing isn't really necessary. Even if there is 0.3v drop at 70A this doesn't really matter too much. The batteries will still get fully charged, and at the right voltage towards the end of the charge. The charger's regulation is fairly soft and so the charger's output won't be up at the regulated voltage until quite late in the charge process anyway. The main reason for needing adequate cabling is for when the device is working as an inverter. If you have 0.35v drop when acting as a charger, it is going to be a lot more (double) when the inverter is chucking out 1600w.

Edited by nicknorman
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No you should definitely fuse the +ve lead, preferably near the battery end. The Victron manual mentions the need for a fuse but anyway you don't want to have fat cable connected to battery +ve unfused. A short circuit would be catastrophic.

 

Do the cables go through some sort of battery isolator? If so, that may be a source of voltage drop and it is not necessary. The fused +ve cable can be connected direct to the battery +ve.

 

Battery sensing isn't really necessary. Even if there is 0.3v drop at 70A this doesn't really matter too much. The batteries will still get fully charged, and at the right voltage towards the end of the charge. The charger's regulation is fairly soft and so the charger's output won't be up at the regulated voltage until quite late in the charge process anyway. The main reason for needing adequate cabling is for when the device is working as an inverter. If you have 0.35v drop when acting as a charger, it is going to be a lot more (double) when the inverter is chucking out 1600w.

Thanks. Very helpful.

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The victron inverter does things even when switched off as evidenced by the big spark you get when you connect it to the battery, presumably charging some capacitorish thing, so isn't an isolator a good idea?

It has big capacitors as you say. But why does that mean it needs an isolator?

 

An isolator is not required by the installation instructions. An isolator is not required by the BSS rules. Our installation (which is a mastervolt, but same idea) doesn't have an isolator and I have never felt the need for one. They are just a source of voltage drop. If I want to de-power the Combi for some reason, I just disconnect the fuse. But I've only wanted to do that once in 6 years when I swapped out leisure batteries for Trojans.

 

Those "capacitorish" things either work properly or fail. If they fail short circuit then the fuse will blow. Anyway an isolator only helps if you are there at the time something goes wrong, and have the wherewithal to operate the isolator.

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That big spark will also occur in the contacts of an isolator each time it's switched on, rapidly burning them and causing a high resistance.

I got round this by wiring a pre-charge resistor in parallel with the isolator, with a push button switch. Press for 10 seconds to charge the capacitors before switching on.

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