Modifying house bank etc best practice

Discussion in 'OnBoard Electronics & Controls' started by 5teve, Nov 14, 2017.

1. Joined: Nov 2017
Posts: 23
Likes: 1, Points: 3
Location: Perth, Australia

5teveJunior Member

Hi guys

First time poster long time lurker.

I'm just in the process of fixing the mess(es) that the previous owner of my boat made and am just moving on to the battery side at the moment.

Current configuration is 2 cranks for port engine 2 cranks for starboard engine and 4 batteries for house. These are split into 2 boxes, house on port side and cranks batteries x4 on starboard (under rear deck) all batteries are same 100ah dual purpose batteries.

I want to reconfigure to give more house, so use the existing 8 batteries as house and add 3 new batteries, 1 crank for each side and 1 small Genset crank

My dilemma is that using the existing boxes the house will be split into 2x 4 battery boxes and there will be approx 3m of cable between the boxes to continue the paralleling. Is this going to be an issue? I was looking for maybe 95mm2 cable between boxes as I may run an inverter at some point.

Steve

2. Joined: May 2009
Posts: 2,521
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Location: South Africa Little Brak River

BertKuSenior Member

95 mm2 means max at 5 to 6 Ampere (depending how hot the surrounding area will be > 30 Degrees Celcius) If the cables get cooled up to 7 Ampere. (per mm2)
3 meter at 95 mm2 means approx 0.0000566 Ohm (at 25 degrees Celcius) and at a current of 100 Ampere only approx 5 milli Volt (o.00566) drop. I have used copper welding cable which I then tinned at the ends and after the connection is soldered onto the cable then to sealed with a product called liquid insulation. It depends totally what your current will be between the 2 battery sets. How good the connectors are and the resistance from cable to connector. That will normally add to the problem of higher voltage drop between the 2 points. You need to give us more details of what will be flowing between your batteries it will be easier to suggest solutions.

3. Joined: Nov 2017
Posts: 23
Likes: 1, Points: 3
Location: Perth, Australia

5teveJunior Member

Hi Bert

Thanks for the calcs. I'm just really wanting to do a sanity check as to whether laying out the house bank in this manner was likely to cause issues with charging and for want of a better description balance of the batteries.

I normally terminate using crimp terminals but then heat with a torch and solder to the cable so connection should be ok. Cable will not be cooled unless the bilge is full.. then I have bigger issues!

Regarding loads, normal house loads initially so lighting (all led) radio, pumps etc, nothing over about 20amp individually. However the plan is to get an inverter at some point (hard wired) looking at a 2kw inverter so we can run TV and kettle without starting the Genset. I'm guessing that could pull upwards of 200a or close.

System is 12v and batteries Re 100ah each so would give 800ah capacity or about 400ah usable without pushing them too hard

I have a 60a mains charger, and will have solar reinstated once I've worked this out.

Steve

4. Joined: May 2009
Posts: 2,521
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Location: South Africa Little Brak River

BertKuSenior Member

I would concentrate on the connections, that the area is sufficient not to lose energy in the connection to the battery and have it properly soldered with a 150 watt iron. Bear in mind that solder creep's up, solder it not horizontal but vertical up, so that not to much solder makes the cable end stiff. The solder will flow into the connector. I don't know whether the Dutch TU in Delft sells the panels which also generate when the sky is overcast. Remember your solar race in Australia this year, whereby the Dutch both cars came first, because the rest all got stuck due to overcast and were delayed by an hour. Bert

5. Joined: Nov 2016
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NidzaSenior Member

If the cable is not tinned when manufactured (which means each little wire inside is tinned so they keep flexibility without breaking the tin/solder) isn't it better for the end of not tinned cable just to use closed crimp connector and to seal it with heat shrink tube which contains glue on the inner wall? When you solder the hole cable end with connector it will be stiff and will break and the moisture can get inside again if not sealed. Crimp connection is not ideal, but is it really less reliable than unpredictable tin in time? When I said open and closed terminal I meant on these differences:

closed
Ring Terminal, Crimp,16-6, M6, 16mm² - automotiveconnectors.com http://www.automotiveconnectors.com/ring-terminal-crimp16-6-m6-16mm.html

open
Solderless Crimp Terminal Non-Insulated Ring Lug 323174 Amp | West Florida Components https://www.westfloridacomponents.com/J569APH09/Solderless+Crimp+Terminal+Non-Insulated+Ring+Lug+323174+Amp.html

6. Joined: May 2009
Posts: 2,521
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Location: South Africa Little Brak River

BertKuSenior Member

I never use a torch on soldering a 8mm internal diameter slug, but have a 150 watt soldering iron and only use closed ring terminal which I let the solder flow from top/ vertical and not horizontal. Thereafter I use Star Brite electrical liquid tape. you may have a point I cannot proof otherwise, but crimping is developed for speeding up and like all sales people they come up with believable reasons to sell their product more. I love to see tests done that crimping is more effective on long term then solder. You may be right, I think is a preference matter. Bert

7. Joined: Nov 2016
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NidzaSenior Member

Well, both of us has a point, I do agree with you about tests, I would also like to see some more detailed tests. From my experience, I have encountered military standard connectors of both types - designed for crimping and designed for soldering contacts, well odd if soldering is completely unreliable, but in that specific case the vibration was not the issue and that is the spec. which should be compared between those two types. You are right that the quality of crimp connection is completely dependable of crimping tool quality, there should be no compromise. I presume that StarBrite product is neither worse either better than heat shrink tube with glue according to description, but I have never used it though. It should be compared polyolefin (heatshrink tube material) vs material used by StarBrite. Anyway, you can make exotic shapes covering with StartBrite, that is a plus.

I did encounter cracked soldered contacts, but hard to tell the exact reason, also I did encounter bad crimped contacts, but the reason was almost always due to bad crimping (bad crimp tool, human error (this can be for both), not tested after crimping, but also low quality crimp terminals). One note about soldering, due to ecology most solder/tin today is without the lead. Then again, car industry and military are still using lead solder because without lead it is harder to achieve same quality of soldered contact, especially when soldering from hand.

I tend to agree with you that it is a preference matter without detailed test shown, so for now, my personal choice would be crimping with good quality crimping tool and good quality crimp terminals (and "waterproof" insulation).

I apologize to the OP for going away from his original question. I do agree with BertKu's answers.

8. Joined: May 2009
Posts: 2,521
Likes: 47, Points: 58, Legacy Rep: 223
Location: South Africa Little Brak River

BertKuSenior Member

I fully agree with you, but I use start brite and heat-shrink sleeve which seals is nicely when it is not yet dry with the heat gun. Probably the same result one has when using some silicone glue. Nizda it is important for the OP to get this information and we thank you for that. Most of the time breakdowns are due to bad connections, thus we thank you for the above. Bert

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