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Old 03-05-2020, 22:53   #1
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Battery wiring plan - constructive input requested

I am planning on installing a new battery wiring plan. Since this subject is new to me, I would appreciate constructive input on anything that looks like an issue or should be changed.

In particular, I need to find a better BMS than the one I have here. It came with the batteries, but w/o specifications or documentation. Ideally I'd find one that would allow for cutting off charging or load independently, depending upon whether a cell voltage is too high /too low. Right now the BMS, if tripped, would cut out all loads and chargers. The chargers would be cutoff directly from the BMS. The loads would be cutoff indirectly through the Battery Protect.

Will the MPPTs be harmed if the DC connection is cutoff by the BMS, but the MPPTs are still connected to the solar panels?

Do I need to add a manual switch to the chargers to ensure shore power and MPPTs are not both on at the same time?

Other than the windlass, most of the wire runs are no more than 5-10ft. I am expecting to use 1/0 AWG on the thicker wire shown, and 10 AWG on the medium wire shown.


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Old 04-05-2020, 06:29   #2
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Re: Battery wiring plan - constructive input requested

*Theorectical* in that I am in design and testing.

For BMS you may want to look at:

REC d.o.o. BMS
123BMS

Both are discussed in various threads here.

MPPTs need to be disconnected on the solar panel side before the battery side. I believe Victron discusses this.

All charge sources can work concurrently. You can vary setpoints to determine lead charger.
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Old 05-05-2020, 10:28   #3
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Re: Battery wiring plan - constructive input requested

The 123BMS solution looks very interesting, although pricey.

I continue to hear conflicting information from knowledgeable people about whether solar panels need to be disconnected from the controller before the disconnecting DC. To your point, this is what I heard from Victron:
Quote:
This shouldn't hurt the controller, but it can cause a short voltage peak if there was still current flowing into the batteries. The unit is not designed to have the battery disconnected under load/charge.

The recommended way is to use the https://www.victronenergy.com/cables...e-on-off-cable for the 100/20, or the remote on/off terminal on the larger models. this is only possible if your BMS has (charge enable) control outputs.

Please note that although a BMS can disconnect a battery, under normal circumstances this shouldn't happen. The battery should be charged to a voltage where the BMS doesn't disconnect, and also discharged not too far so the battery doesn't disconnect on 'low cell alarm'.

The only reason a BMS can disconnect at 'normal charging voltage' is when a battery is out of balance, this should really only happen with new batteries, or batteries that haven't been used for a while.

To 'pre-balance' batteries it's a good idea to keep them charging to the prescribed voltage at low current for a while, this gives the BMS some time to get the cells balanced. The battery manual might have information about this.
On the other hand, the knowledgeable folks at PKYS.com said not to worry about it.
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Old 05-05-2020, 20:41   #4
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Re: Battery wiring plan - constructive input requested

you need a engine battery switch between engine battery and engine.

the inverter needs a battery switch and fuse.

what opens the charge bus during an overvoltage? that needs a switch / bp protect or simular as well.

what shuts off the inverter for low battery?

what is the 1,2,all swtich doing? I hope that's not so you can charge the house from the engine? the bp protect states it's only one for direction. you can't put that switch to all and have current comming back from the engine.
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Old 05-05-2020, 20:50   #5
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Re: Battery wiring plan - constructive input requested

the victron conrollers raise voltage when disconnected. like 16v out their output.

if it's by itself it's probably fine. but I had a victron 75/15 and a dc to dc charger on the same charge bus. so when the charge bus opened. the victron went to 16v. and then the dc to dc saw 16 volt on the "battery" and freaked out alarming. and I could not find any to reset it... I fixed it by junking the dc to dc for a different one that didn't freak out.

the charge bus also opens when the batteries are cold. so more often then you think. well where I live anyways.
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Old 06-05-2020, 20:37   #6
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Re: Battery wiring plan - constructive input requested

Good points, thanks.

The 1/2/both battery switch is existing, which is a big reason that I included it as-is. I have no intent of connecting the batteries through "both". What I suppose I really need to do is just replace the existing switch with two separate single-battery switches, each for just one battery. With that I would connect the starter and alternator through the starter battery switch.

I'm not quite sure what to do with the inverter. Victron has said that the battery protect can't connect to an inverter, except where the BP directs a remote inverter switch. If I connect the inverter to the battery switch then it is also connected to the BP.

Charge bus is directly shut off via the BMS. I might add the 65A Victron Battery Protect there as well, installed backwards for the charger. I'm thinking I should also add three hard switches, one for each charge source.

Victron has a cable to plug into the controller ve.direct port to properly turn off the the solar controller. In lieu of that cable, the controller seems to ship with a small jumper across the two middle contacts of the ve.direct port. it may be that just open-circuiting those two contacts will do the same thing as the cable. A test may be in order.
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