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parallel 12v system questions

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I am trying to make my rig a little cleaner. First is the wireing.

I run a HB 587, a Minn Kota 12v 70 pdv2, 2 digitroll2 riggers and a troll master. Off of a set of batteries in the bow with no charging system

currently I just switch batteries when 1 goes low but I need to reste the riggers when do.

If I run a parallel system how will this affect my run time?

How do I charge a parallel system?

I saw a skimatic that showed red on one BATT and Black obn the other. Is this correct. Also I rarley ever change Batteries on the water when I not using the trolling motor.

So should I just leave it be and keep a seperate fully charged BAttery for a back up?

Thanks Steve

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Red to black will add voltage making it 24v probably not what you want. Its always a good idea to have an isolated batterys to not ruin both if one goes down. If you parallel the battery's red to red black to common ground make sure your charging system can handle the load. I have a large agm battery with a large amp hour rating for handling many discharge/recharge cycles and an isolated starting battery. My battery switch will parallel them if I need an extra boost if for some reason the starting battery is dead.

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To combine two 12v batteries into one big 12v battery, you connect the terminals of each battery positive to positive and negative to negative. Then hook your equipment to one of them just like you would with a single battery. Same for charging -- connect the pos lead to the pos terminal and the neg lead to the neg terminal.

This will give you a battery system with twice the power capacity of a single battery. So if each battery individually has 1000 units of power you get 2000 total when combined. If you use 80% of the combined battery, you will still have 400 units left. In the same situation with two separate batteries and you use 80% of each, each would only have 200 units each remaining. 200 might not be enough for the battery to be of any use as a spare battery. By connecting the pair of batteries with the 400 units remaining though, it is more likely to be useful.

If you do go with a pair of batteries in parallel, they should be identical to each other -- same architecture, capacity... I'd even go as far as brand & model. If not you will have trouble in getting them fully charged and drawing power evenly from them. Also, charging will take twice as long for the two with one charger compared to being able to use a charger per battery with separate batteries -- although I have not had an issue with getting the pair I have connected in parallel charged overnight.

I run my electronics off the pair of "house" batteries I have in parallel -- 3 LCD multi function displays, GPS, radar (not on all the time), VHF radio, X4 FishHawk, and the stereo. I run my downriggers and the autopilot off of the engine batteries. The autopilot hydraulic pump is running all the time when trolling and is a relatively high draw. The downriggers are of course intermittent use but again a reasonably high draw when used. Neither are affected by electrical interference that could be introduced by the outboards.

To charge all 4 batteries (1 per 90 hp Honda, 2 house) I have a Guest onboard charger that I try to plug in each night to top off all of them. On occasion when I do an overnight trip and don't have "shore" power, the house batteries have generally lasted for two days with no problems. Last year I installed a gizzmo that is supposed to take the charging output from either of my Honda outboards and charge all of the batteries. It either isn't hooked up right or is broken... as it isn't working. I'm planning on redoing/checking its install this weekend. I also picked up a small 2000 watt gas generator to take along as a 110v power source for the onboard charger... just in case.

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I have not seen a 70# 12v trolling motor. If it is a 70# Powerdrive V2 it is most likely 24v. If this is the case the trolling motor needs to be the only thing on those batteries and they need to be wired in serires. It is possible to power other things off of them but your asking for electrical issues and NMEA regulations strictly prohibit this without the use of a 24v to 12v converter which are pricey.

So confirm what voltage your electric trolling motor is and if you do have all that other stuff wired to those batteries and your trolling motor is 24V, the Humminbird, trollmaster, downriggers, and whatever else you have wired in the bow there needs to be redone to the battery in the back.

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I am thinking the same as Hondam that the trolling motor is 24v and nothing else should be wired to those batteries. All of the higher power trolling motors are 24 or 36v because the amp draw would be too high at 12v. I just looked up the PDV2 it is 24v as is all the 70lb thrust models on the fresh water list.

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Best and easiest solution in my opinion to solve what you are looking to do, install a 4 way battery switch (Off-1-2-Both). IT will tidy up your wiring and give you the option to change how your using your batteries with a flip of a switch.

Also if your running batteries in pairs they should be of similar age and composition (Twins if possible) if you want to get the most out of them as far as longevity and performance.

When installing the switch put all of your load on the common terminal, and a battery on each source post. Make sure to run a cable to each neg terminal on the batteries to establish a common ground.

When attaching your loads to the back of the battery switch it is recommended that no more then 4 connections be made at any one terminal. Therefore it would be best to install a power post or buss bar with a short lead to the switch to provide an adequate and reliable connection. Trying to put all those wires on the back of the switch is a common mistake and which both can make it a pain on yourself trying to maneuver all those wires and get the switch secured down and connection reliability suffers.

Notice how I wired this switch only 4 wires going to it with 2 going to batteries and 2 going to distribution points.


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