Trolling Motor Batteries, On Board Charger Size & Wiring

[Bay_Fisherman]

I am going to be adding a Minn Kota Riptide ST 101 lb. trolling motor (36v) and an onboard charger to my 22' Sportsman Masters w/ a Yamaha F150. I had a few questions regarding the number of banks and wiring that I will need on the onboard charger and was looking at getting some feedback from you all.

Currently, I have 2 batteries (1 Starting / 1 House for Elect. W/ Stereo & (2) 6.5" Speakers and Lowrance HDS 7 hooked up to it) and a perko switch. I am looking at buying 3 new batteries just for the trolling motor. This will give me a total of 5 batteries now (1 starting / 1 House / 3 for the trolling motor. My question is how many bank charger am I going to need and how would you wire it? I understand that I will now have a total of 5 banks if I am thinking through everything correctly. Would you all go 2 seperate chargers, 1 (3) bank 10 amp for the trolling motor batteries, and (1) 2 bank charger for the Starting battery and house battery or (1) 5 Bank Charger for everything? Also if there is an alternative in the number of bank chargers and wiring would you please let me know. I am no electrician by any means so please excuse my ignorance if this is completely wrong. Any feedback would be appreciated. Thanks for the help.


Chris

 

[Silvertip]

Re: Trolling Motor Batteries, On Board Charger Size & Wiring

You do not want a five bank charger because it would be horrendously expensive and if one bank takes a dump chances are another would go with it. So my suggestion is to use one three bank for the 36 volt system and one dual bank for the starting/house system. Below is a diagram illustrating the 36 volt wiring for the troller.

WARNING: When making charger connections make darned certain you keep the outputs paired so the POS and NEG leads for output #1 go to battery #1, POS and NEG leads for output #2 go to battery #2 and POS and NEG leads for output #3 go to battery #3. Battery numbering used here is for reference only. It doesn't matter which battery the outputs go to as long as they remain paired on the same battery.

OUTPUT is a key consideration when selecting the charger. A 10 amp charger may be a TOTAL of 10 amps so divide that by 3 which is 3.3 amps per output. Not a good thing for a troller battery bank. You want a minimum of 5 amps PER OUTPUT with 6 to 8 amps or more preferred.




Here is wiring for a a dual bank charger in a 24 volt system. Wiring for a 36 volt system follows the same convention. One output to each battery. The charger for the starting and house batteries would have a two bank charger, again, with one output going to each battery.



There is one other option where you would have a three bank for the troller and a single output charger for the starting and house batteries. That - however would require leaving the Perko switch set to BOTH to charge both of those batteries. Not an ideal situation. That single output charger would be connected to the COM terminal on the switch.

 

[fishrdan]

Re: Trolling Motor Batteries, On Board Charger Size & Wiring

^^^ very good post by ST! I too would go with a 3-bank for the TM batteries, and then a 2-bank for the start and house battery.

How quick are you going to want to turn the boat around after fishing? A 5 amp/bank charger could take a long time to recharge the batteries, 20 hours or so if the batts are heavily depleted. A 10 amp/bank charge would cut that time in half.

How far are the batteries going to be located away from the trolling motor, or trolling motor plug? You need to select the right gauge of wire, depending on the total length of wire.

Go to genuinedealz.com for all your wiring and crimp connectors for the project, good prices on "marine" wiring and quick shipping. They can also terminate your wires for a nominal fee, if you know the exact length of wires needed.

 

[Bay_Fisherman]

Re: Trolling Motor Batteries, On Board Charger Size & Wiring

Thanks ST and FishrDan for the responses. After reviewing what both of you said let me provide you with a little more detail about the layout and what I was thinking.

All 5 of the batteries will be located in the center console. The trolling motor will be mounted on the bow and plug into the trolling motor plug that comes standard on the boat.

The onboard chargers that I was looking at was the Dual Pro Sportsman Dual Bank SS2 (Two 10-Amp Banks, 20 Amps Total) for the house and starting batteries and the Dual Pro Sportsman 3 Bank SS3 (Three 10-Amp Banks, 30 Amps Total) for the troller batteries.

The batteries that I was looking at buying were the Optima Blue Top D27M. After reading the specs. on the battery Optima recommends 10 amps maximum for constant voltage charging.

I have got a few differing opinions on hooking a 2 bank charger to the house and starting battery with some recommending to just let the engine charge those 2 batteries. Also others have stated to go with the 3 Bank (5 Amp Per Bank, 15 Amps Total) charger instead of the (3) (10-Amp Banks, 30 Amps Total) for the troller batteries because the (3 Bank-5 Amp Per Bank) will provide a slower more consistent charge and provide longer battery life. I realize that if I went that route it would take twice as long to fully re-charge the batteries. I am normally just fishing on the weekends and I would not intend to completely deplete the batteries all the way down. Thoughts?

Also I had a few other questions. What do you all think about going with a 2 Bank-5 Amp Per Bank instead of the 2 Bank- 10 Amp Per Bank charger for the house and starting battery based on the theory that the engine will be charge these 2 batteries for the most part and they would require minimal charging. Do you all think that the (3) (10-Amp Banks, 30 Amps Total) will be too much for the troller batteries and reduce their lifespan since I will be pushing the max recommended charging amps to the batteries? Should I move a step down to the (3) (5-Amp Banks, 15 Amps Total) charger?

If you all could provide me with some feedback I would greatly appreciate it.

 

[Silvertip]

Re: Trolling Motor Batteries, On Board Charger Size & Wiring

Here is my opinion on both the battery selection and charging "rate".
1) While many folks seem to feel that spending more money on a battery somehow makes that battery better, I feel all it does is make your wallet lighter. The key to battery selection depends on the current draw of the troller. A 101# motor draws about 46 amps at maximum. So look at the label on the batteries you are considering for the RESERVE CAPACITY number. This is usually specified as xxx @ either 23 or 25 amps. In other words if the label says 175 minutes @ 25 amps, that means the battery can deliver 25 amps for 175 minutes before it is no longer able to do so. That does not mean the battery is dead, but its power will drop rapidly after that point is reached. Without getting into who has the best prices, I've bought lots of flooded, deep cycle batteries over the years and I find that my local farm store (Fleet Farm in Minnesota) has group 27 deep cycles with reserve capacities in 175 - 200 minute range on a daily basis for about $79.00. Cabelas, just up the street from me has a number of Optima and other so called "Hi-Tech" batteries that have nearly double the price tag and no better specs. So are they a better battery? I contend that they are not but that is based on length of service and run time. Any boat that appeared in my yard was fitted with a new battery from my farm store. That battery was in perfect working order when the boat went to a new owner anywhere from three to five years later. It all depends on maintenance and charging the batteries immediately after use -- not just before you intend to leave on a trip. Now on to chargers.

2) A flooded deep cycle battery can be charged at a rate (amps) that is 20% of its capacity. A 100 A/Hr battery can be charged at a 20 amp rate. Hi-Tech batteries have varying charge profiles that may require a charger with selectable profiles. Slow charging does not make a battery last longer -- it just takes longer to charge it. Besides, most on-board chargers these days are "smart" in that they know when to cut the charge back and when to turn themselves off. So buying a low output charger to charge three troller batteries that you may need charged in a hurry does not make economic sense. In other words, get the job done so I can go fishing again.

3) Since your boat has a Perko switch for the starting and house batteries the engine would likely keep them topped off just fine provided you used the switch to your advantage. Not knowing the alternator output of your engine (or what engine you have) would determine whether this is possible. Since you need a 101# troller, I would assume you have a pretty large outboard which would have a substantial alternator so a dual bank charger might not be needed. But that all depends on how discharged the house battery gets. Remember, even if the engine alternator has a 40 amp output, if you ran the house battery down to where you sucked 80 amps out of it, you would need to run wide open for over two hours to replace that current. So only you can determine whether or not you need a dual bank. My thoughts are that a dual, five amp unit would be fine for the house and engine. Or just a single for the house battery since the engine start battery would rarely be significantly discharged and you could flip the switch to start it on the house battery. And if that didn't work, a set of jumper cables attached to one of the troller batteries would jump the start battery. Lots of options in that regard. But -- use the KISS principle.