Gabriël Posted December 11, 2017 Share Posted December 11, 2017 the big moment has come [hehehe] so i now have the icc and bmv702 - the icc is already running. just before attaching the bmv702 i'd like to run this one by the gurus on the forum. 1st off my wiring for the batteries are as in the diagram. from the shunt i have a rj11, see image, running to the bmv702 and from there the ve direct to usb can communicate with my pc and the icc. my question is how do i correctly attach the shunt at the battery end for it to measure midpoint voltage on this 48v system? any other tips are also welcome - like for instance how to upgrade my axpert 5kva to the latest firm/software... thanks guys in Christ gabriel Quote Link to comment Share on other sites More sharing options...
Chris Hobson Posted December 11, 2017 Share Posted December 11, 2017 Hi Gabriel Three things: The shunt needs to be as close to the negative terminal of the battery bank as possible. The further it is the greater the likelihood of introducing errors in voltage readings. Nice thick battery cables will negate this but still try and get as close as you can to the negative terminal. The shunt must be installed correctly. It has a battery side and a load side - check and make sure you get it the right way round. The mid-point probe is a important piece of kit and therefore make sure you are actually measuring the midpoint. Your diagram does not show a battery disconnect. This may just be an omission on your diagram. If you don't have one get one soon. I have just been to a client who has lost an Axpert due to not having a proper battery disconnect and therefore does not have an adequate shutdown procedure. Quote Link to comment Share on other sites More sharing options...
___ Posted December 11, 2017 Share Posted December 11, 2017 1 hour ago, Chris Hobson said: The shunt needs to be as close to the negative terminal of the battery bank as possible. Any voltage drop between the battery and the shunt will reflect in voltage readings, though in my experience, you have to be really sloppy to get it wrong. Just follow best practices and even if it's a meter away it should be fine. 1 hour ago, Chris Hobson said: The mid-point probe is a important piece of kit and therefore make sure you are actually measuring the midpoint. Make sure your battery inter-links are thick enough. Or double-up on that one right in the middle. At full load there will be a slight drop across that link and your midpoint will be pushed slightly to one side. Use the fuses that came with the BMV in both lines. And then just follow the instructions (also in the box). There's two terminals on the shunt where you connect the main and auxiliary (aka midpoint) connections. Leave the RJ-12 disconnected until the installation is complete, that's the last thing you plug in. If you have a fuse in your battery line (you should), place it on the positive side. That way you avoid another voltage drop across the fuse. Remember to configure your charge efficiency and Peukert factor for lead acid batteries. I can't remember what good values are for lead acid, it's been too long since I had to do it. Also set the Charged Voltage setting to something above floating voltage, eg I had mine set to 28V on my 24V system, and the tail current to something that fits your batteries, with my AGMs 1% worked well (so if charge current dropped to under 2 amps on my 200Ah batteries, at a voltage of 28V or more, it would reset to 100%). It will start at 100% SoC regardless of what the actual battery state is (it has no way of knowing at this point). Charge the batteries fully, and I mean fully, so the BMV is synced. The BMV comes calibrated for zero current out of the box, so normally you don't have to calibrate that. But it is also explained in the manual. Chris Hobson 1 Quote Link to comment Share on other sites More sharing options...
Gabriël Posted December 12, 2017 Author Share Posted December 12, 2017 thanks @Chris Hobson and @plonkster ! 8 hours ago, Chris Hobson said: The mid-point probe is a important piece of kit aaaaaaaaaaaaaaaaaargh, just as i thought i had everything together.... how much are they and where do i get one 8 hours ago, Chris Hobson said: battery disconnect ditto 9 hours ago, Chris Hobson said: adequate shutdown procedure thanks for pointing this out chris, it is indeed important for emergency purposes! ok, now here is a christmas wish-list for the guys in the pre-solar phase: what they need is a comprehensive guide as to the setup - not just what some fly-by nite or whatever solar 'expert' tells them in order to sell off some extra stock. for the longer i look into this the more distant the illusive ROI gets - although what you gain is a degree of independence. enjoy your day! Quote Link to comment Share on other sites More sharing options...
Chris Hobson Posted December 12, 2017 Share Posted December 12, 2017 15 minutes ago, gabriel said: aaaaaaaaaaaaaaaaaargh, just as i thought i had everything together.... how much are they and where do i get one It not something separate if you bought a BMV 702 then it comes with the BMV. (It is one of what they describe "positive supply cables"). One measures the voltage of the whole bank and one measures the midpoint. The battery disconnect I will try make a plan for you. Do you have a PostNet or Pick 'n Pay in Vredendal? The ROI does not need to be ludicrous. I am about to embark on my 2nd phase, the first phase having paid for itself. Gabriël 1 Quote Link to comment Share on other sites More sharing options...
Gabriël Posted December 12, 2017 Author Share Posted December 12, 2017 thanks @Chris Hobson, you are about to make my day [NOT ala clint eastwood ] - i'll message postage data as the two cables look the same [image] i believe i should connect both as indicated on the bmv702 quick install guide, i.e. going from the shunt b1 and b2 to the position as indicated by you on the diagram??? Quote Link to comment Share on other sites More sharing options...
Chris Hobson Posted December 12, 2017 Share Posted December 12, 2017 Jip B1 to positive of the entire bank B2 to the midpoint. Quote Link to comment Share on other sites More sharing options...
Gabriël Posted December 12, 2017 Author Share Posted December 12, 2017 i.e. like such Quote Link to comment Share on other sites More sharing options...
Chris Hobson Posted December 12, 2017 Share Posted December 12, 2017 28 minutes ago, gabriel said: i.e. like such 100% Gabriël 1 Quote Link to comment Share on other sites More sharing options...
___ Posted December 12, 2017 Share Posted December 12, 2017 5 hours ago, gabriel said: These cables are also used with other Victron kit (but doesn't always ship with it). For example, the VEBus BMS needs such a wire to power the BMS, but there isn't one in the box. In my case, I removed my midpoint wire (no need to monitor that when you have built-balancers, and lithiums don't care so much about it anyway) and redeployed it to power the BMS :-) Quote Link to comment Share on other sites More sharing options...
Gabriël Posted March 17, 2018 Author Share Posted March 17, 2018 On 12/12/2017 at 1:41 PM, plonkster said: I removed my midpoint wire (no need to monitor that when you have built-balancers is a 'built-balancer' the same as the ha02 battery balancer? and if so what will i do with the midpoint wire? regards Quote Link to comment Share on other sites More sharing options...
___ Posted March 17, 2018 Share Posted March 17, 2018 3 hours ago, gabriel said: built-balancer For some reason, I sometimes think words but my hands don't type them. Buffer overrun. I meant to say built-in balancers. Lithium batteries often have built-in balancers. The batteries I have have passive balancers that operate at the top, ie as one cell fills up it starts bypassing it so that the other cells fill up slowly. It can only pass a small amount of current so it takes a while for balancing to happen, typically a few days of charging to 100%. I'd keep the midpoint monitoring for lead acids. Unbalanced cells on Lithium is not a big issue. Unbalanced cells on lead acid WITH a balancer is a big issue. Chris Hobson and Gabriël 1 1 Quote Link to comment Share on other sites More sharing options...
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