Adding another battery
- Thread starter Lazy1
- Start date
Lazy 1...would you mind posting your energy calculation? It appears you and I are in very similar situations trying to figure out a new solar setup with similar electrical requirements and battery. However I probably have a few less electrical items then you at this point. I too have begun to narrow it down to a 30 watt panel w/ Victron MPPT 75/10 controller based off of Gene's setup.
Thanks...
Zinger88
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Thanks...
Zinger88
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Gene,
As noted previously, I'm planning on using only one 30 watt panel and Victron MPPT 75/10 controller to recharge my 81 amp hour house battery. Trying to keep this as simple as possible so can you provide some advice on the cable specs (size & length) you utilized to go from your solar panels to controller and controller to battery? I'm assuming you used the bus bars prior to controller since you have two solar panels? This may be a dumb question...but with only one solar panel can I wire directly from panel to controller and then straight from controller to battery? Did you fabricate your own cable lengths and connectors or did you purchase them prefab'd?
Thanks in advance!
Zinger88
~~ _/) ~
As noted previously, I'm planning on using only one 30 watt panel and Victron MPPT 75/10 controller to recharge my 81 amp hour house battery. Trying to keep this as simple as possible so can you provide some advice on the cable specs (size & length) you utilized to go from your solar panels to controller and controller to battery? I'm assuming you used the bus bars prior to controller since you have two solar panels? This may be a dumb question...but with only one solar panel can I wire directly from panel to controller and then straight from controller to battery? Did you fabricate your own cable lengths and connectors or did you purchase them prefab'd?
Thanks in advance!
Zinger88
~~ _/) ~
The bus bars by the MPPT are not needed for one panel and not absolutely necessary for running two panels in parallel.
However it does make the series easier to modify or reverse engineer.
From what I have been seeing there is no need to go larger than 14 ga. for this size system between MPPT and battery and my panel came with remarkably thin wires, maybe 16 or 18? DC power is lossy so distance is somewhat important, keep it under 10 feet-ish between each of PV-MPPT-Battery.
I got 10 ft of 12 ga., 25 ft of 14 ga., and 25ft. of 16 ga. to rewire my setup all tinned copper even though I am fresh water trailered.
I expect to have a lot of spare wire.
However it does make the series easier to modify or reverse engineer.
From what I have been seeing there is no need to go larger than 14 ga. for this size system between MPPT and battery and my panel came with remarkably thin wires, maybe 16 or 18? DC power is lossy so distance is somewhat important, keep it under 10 feet-ish between each of PV-MPPT-Battery.
I got 10 ft of 12 ga., 25 ft of 14 ga., and 25ft. of 16 ga. to rewire my setup all tinned copper even though I am fresh water trailered.
I expect to have a lot of spare wire.
Correct.
Bus bars were necessary in my case, because the controller has only one PV+ and one PV- terminal, each of which are too small for more than one cable. No need for bus bars with one panel, though.
I used prefab cables from the panel manufacturer (Renogy) like THESE. They are 10AWG, which is probably overkill for 1.6A panels, but that's what Renogy panels are wired with, which was fine with me. The thicker the better, and the shorter the better, as far as I'm concerned.
By the way, have you bought your controller yet?
If not, I recommend getting one with built-in Bluetooth. Mine was not, so I had to buy and add a Bluetooth dongle (black thingy in the top left of my pic). You don't "need" Bluetooth, but you WILL like it. The Victron controller app is WONDERFUL.
If not, I recommend getting one with built-in Bluetooth. Mine was not, so I had to buy and add a Bluetooth dongle (black thingy in the top left of my pic). You don't "need" Bluetooth, but you WILL like it. The Victron controller app is WONDERFUL.
Thanks Gene and Lazy1. And yes...I'll be purchasing the controller w/ built-in bluetooth. I like the idea of being able to monitor my battery and charging via Victron's app on iphone. Plans are to mount PV on the stern rail and run cable to controller mounted near battery which is located behind cabin cooler step on MkII. Hopefully I can get out to the boat this week to measure needed cable lengths. OK....so 10 AWG for PV->Controller, but what size recommended for Controller ->Battery? Distance should only less than 2' for that run.
@Zinger88: You'd be fine with 14 AWG for the full run. 10 AWG is overkill, but would give you lots of headroom for future expansion if ever needed. The rule of thumb I've heard is to target <= 3% voltage drop for systems you really care about. (e.g. see Marine Wire Size and Ampacity | West Marine).
An online voltage-drop calculator will work out the numbers for you. E.g., at 12v, 2.5A, 12 feet total, I get 0.5% voltage drop.
Voltage Drop Calculator
This free voltage drop calculator estimates the voltage drop of an electrical circuit based on the wire size, distance, and anticipated load current.
www.calculator.net
So if you already have 10 AWG wire and yellow crimp connectors, I say use that for the full system. If you want to save a little, you'd be totally fine with 12 or 14. FWIW - I used 10 and 12 for my 100w system, which is quite a bit larger than the 30w you're looking at.
I was searching thru old post's regarding solar connectors/plugs and found this by CaptDon01. Unfortunately he's no longer on the forum but he did state that he'd used it for a few years w/ no issues. Has anyone else utilized a 2-pin polarized plug and socket cable connector like this as a thru-deck plug for solar setup?
Where to connect Solar Panel on a small system?
They're rated for 3A which I would assume would work with my 30 Watt panel which is a 1.6A?
Sea-Dog Polarized Connectors
Where to connect Solar Panel on a small system?
They're rated for 3A which I would assume would work with my 30 Watt panel which is a 1.6A?
Sea-Dog Polarized Connectors
I'm just looking at all options at this point and was thinking of using the thru-deck plug more as a way of being able to quickly disconnect the solar panel and stow away if I wanted to. For those who currently have MC4 connectors...how difficult (or easy) is it to disconnect/reconnect them?
Disconnecting MC-4's only takes a few seconds. Maybe a bit more than a trailer plug, but only marginally.
I haven't ordered my panel yet...which one did you get? I was considering the Renogy...