Pairing 1 battery with starting battery?

[dre1965]

I was wondering if anyone paired a battery with their starting battery? Was wondering if a guy could put all his electronics and accessories on one battery, and on the other battery just for starting the engine, hook it up using the parallel technique? One of the reasons I ask is I only have a 4 bank charger, I have a 36V trolling motor. The original battery was only a 27 series with like 700 CCA and it's not big enough for my engine (250 ProXS), came with the boat when I bought it and it worked for a little over a year. I could not believe it was only a 27 series, just took for granted it was a 31 series with more CCA's. Thanks in advance

[Texas Rig]

You could go 2 different ways. If you parallel a second battery to your cranking battery you will have basically 1 large 12 volt source to crank and run you accessories and your 4 bank charger will charge all batteries. The important thing to remember is to match batteries when you parallel. If you don't parallel and dedicate one battery to only crank then it's not critical for that battery to be on the 4 bank charger as the motor will keep it charged while on the water. The battery running the accessories should be on the 4 bank charger. Also, by not doing the parallel arrangement, the 2 batteries do not need to match. The cranking battery has high CCA's and the accessory battery is deep cycle. During storage, put a small battery tender on the dedicated cranking battery.

[grey goose 01]

This is what I had my installer do since I'm running 4 graphs

[KRC18D]

I used a switch and paralleled 2 group 31. One to crank the motor and the other to run the graphs/power pole. Had a single group 31 before and it left me stranded a couple of times when I was running everything all day.

[Saffie]

I got a 3 way battery selector switch and have 2 batteries connected to it. One is my cranking battery and the other one is for accessories like pumps and graphs. With the I can turn all power off, switch just the cranking battery on, can combine the the 2 batteries (like a jumper for cranking the engine) or just have battery 2 for cranking the outboard.

[kdubracing]

You could go 2 different ways. If you parallel a second battery to your cranking battery you will have basically 1 large 12 volt source to crank and run you accessories and your 4 bank charger will charge all batteries. The important thing to remember is to match batteries when you parallel. If you don't parallel and dedicate one battery to only crank then it's not critical for that battery to be on the 4 bank charger as the motor will keep it charged while on the water. The battery running the accessories should be on the 4 bank charger. Also, by not doing the parallel arrangement, the 2 batteries do not need to match. The cranking battery has high CCA's and the accessory battery is deep cycle. During storage, put a small battery tender on the dedicated cranking battery.

I am looking at getting a second battery to run parallel. When you say match batteries, what exactly do you mean? Do you mean same type (starting vs. deep cycle or AGM vs. flooded), same CCA, same exact battery?

[Texas Rig]

I am looking at getting a second battery to run parallel. When you say match batteries, what exactly do you mean? Do you mean same type (starting vs. deep cycle or AGM vs. flooded), same CCA, same exact battery?

Yes, I would match the type....for example if your current cranking battery is a dual purpose flooded then I would parallel with the same type. Matching exact size (CCA or RC) is not that critical. What is important is adding a new battery to one that has some age and trying to charge both with a single bank from the charger. An older battery will need more amps than the new battery and the charger could overcharge the new battery to get the older battery topped off. If you have separate charger circuits to the parallel set that would be best because the charger would charge both independently.

[kdubracing]

Yes, I would match the type....for example if your current cranking battery is a dual purpose flooded then I would parallel with the same type. Matching exact size (CCA or RC) is not that critical. What is important is adding a new battery to one that has some age and trying to charge both with a single bank from the charger. An older battery will need more amps than the new battery and the charger could overcharge the new battery to get the older battery topped off. If you have separate charger circuits to the parallel set that would be best because the charger would charge both independently.

Makes sense, and along my thinking. Now, the question on the charger. I have a 4-bank Minn Kota onboard. 3 banks on the trolling motor batteries and 1 on the cranking. I also have a few normal Battery Tenders laying around. The cranking battery is only a year or two old, and I am probably going to add the exact battery for the second. Would I be better off just leaving on the 1 bank onboard, or adding pigtails to the second battery and attaching the Battery Tender when charging? Would having 2 different chargers on a parallel circuit matter? I may be overthinking it, but I have either option easily available, so just trying to figure what is best.

[wmitch2]

There's a few options you have, but the first thing you should do is Match the Batteries. Same brand, series, CCA and RA. I'd start off NEW. Then they are the same for sure. You can use your 4-Band charger and put one set on either of the 2 batteries. It will take a bit longer since it's charging 2 batteries. You also can put all your motor on one battery and all the rest on the other. Remember, when paralleling batteries, the Voltage stays the same and the AMPS double. Also, when running the big motor, the alternator will still charge both batteries. There other options besides adding a 5th battery too. Look at Troll Bridge. It will charge the TM batteries as you run, and automatically jump the start battery if it's low.

http://www.yandina.com/troll36info.htm

[1BADAIR]

If they are hooked up parallel then hooking and graphs to one and the engine to the other isn’t needed. Both loads are still pulling from both battery’s