[PSUBS-MAILIST] batteries

Sun Oct 29 17:22:03 EDT 2017

So, 36 VDC, 155 A, copper wire, length 5.5 m.

Wire size 2 AWG gives 898.434 mV (2.5%), Voltage at end of circuit 35.102 V, power loss 139.257 W.

2 AWG would be your minimum, with efficiency improving as you get larger from there.

Sean

-------- Original Message --------
On Oct 29, 2017, 14:10, Rick Patton via Personal_Submersibles wrote:

> Sean,
> I have about 8' from battery to selector switch and then about 10' from switch to pos buss so around 18'.
>
> On Sun, Oct 29, 2017 at 12:21 AM, Sean T. Stevenson via Personal_Submersibles <personal_submersibles at psubs.org> wrote:
>
>> Rick, what is the length of the wire run? Sizing a cable appropriately involves keeping the overall voltage drop in the circuit to 2.5% - 3% of the nominal source value, maximum, and of course, lower is better. This is dependent on length, so for a longer run you need a bigger cable, etc. There are calculators available for this purpose. One of my favourites is an Android app called "ElectroDroid". There are also online tools.
>>
>> Sean
>>
>> Sent from ProtonMail mobile
>>
>> -------- Original Message --------
>>
>> On Oct 28, 2017, 13:27, Rick Patton via Personal_Submersibles < personal_submersibles at psubs.org> wrote:
>>
>>> I am trying to size my wire for the 36v side from where the power comes into the sub to selector switch to hot buss bar and was wondering if that was something that someone could answer. Also I was told by Minn-Kota that they recommend group 27 marine batteries.
>>> I have a couple of deep cycle (marine batteries) on my boat and they are 550 cca and 125 amps reserve capacity.
>>> My plan is to run all three Minn-kota thrusters off of one side at a time and their max draw is 46 amps max so there is 138 amps if all three thrusters are wide open. I doubt I would ever have all three maxed for more than short spurts but want to be repaired for the worst case scenario like if I am bucking a strong current.
>>> I also will be running 6 outside LED lights off the same bank and though I can dim them and selectively use them, all on at max would be about a 16.6 amp draw as well. Now most of the time I will be using the thrusters at minimal draw and not all 3 at the same time and the 6 lights will probably never all be on at the same time.
>>> If everything was wide open, I would be pulling about 155 amps from a bank that has a reserve capacity of 125 so it would deplete the bank rather fast and may even damage the batteries due to a quick drain? So,,, first question...would 2 OTT wire be sufficient from battery source to bus bar as long as I am not running full tilt on everythig and second... since I have to stick with a lead acid system due to design, can I get a group 27 battery that can deliver much more than the 125 amps I have on my boat?
>>> I also have the option of putting the battery selector switch on both banks if I have to but would rather deplete one bank at a time if can.
>>> Comments appreciated.
>>> Rick
>>
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