CHAINING BATTERIES

[cpuzone]

IS IT SAFE TO CHAIN TWO BATTERIES TOGETHER FOR A 1974 115 MERC. AS I UNDERSTAND IT I WOULD CONNECT THE POS OF ONE BATTERY TO THE NEG OF ANOTHER AND THEN CONNECT THE MOTORS CABLES TO THE THE TWO (POS/NEG) POSTS REMAINING ON EACH BATTERY.<br />IS THERE A DISADVANTAGE TO DOING THIS?<br />THANKS FOR TH HELP IN ADVANCE.<br /><br />RANDY

 

[Nikko]

Re: CHAINING BATTERIES

You're describing a series connection for your batteries. This will result in 24 Volts between the free +ve cable and the free -ve cable. I don't think you want this.<br /><br /><br />If you run the batteries in parallel (+ve from bat.#1 to +ve on bat#2 to +ve term. on motor and -ve from bat.#1 to -ve on bat.#2 to -ve on motor) you'll get 12V to the motor and a deeper reserve of power.<br /><br />Good luck<br />Nikko

 

[LubeDude]

Re: CHAINING BATTERIES

If you do it as you describe, you will have 24 volts and will fry all of your electrical components. <br /><br />What is your reasoning for doing it in the first place?

 

[Stephan-HB]

Re: CHAINING BATTERIES

Why will you do that????<br />If you make it as your discription says you will have 24 Volts!!! If you will take a 2nd Batterie for save, if one faills you have to make two different circuts. Even a Backup-Batterie with a manual Switch?

 

[timmathis]

Re: CHAINING BATTERIES

Is the reason you want to do this due to slow cranking?

 

[JasonJ]

Re: CHAINING BATTERIES

When it is cold out, I will often use a pair of shortened jumper cables and hook my deep cycle trolling battery to my starting battery to get my main motor to start more quickly. If this is what you are talking about, you have to hook your batteries in parallel (+ to +, - to -), or you will end up with the previously mentioned 24 volts. the proper way to go about this is to have your two batteries connected to an A, B, Both switch, something I plan on doing one of these years on my rig. My cable technique works fine for the time being.<br /><br />You don't really want to do a permanent hook-up of the two batteries unless they are the same age, brand, and cranking amps. Otherwise, one will want to always draw on the other. FWIW, trucks with larger diesel engines use permanently connected duel batteries, so we know it is done reliably.

 

[ZodFutMk2]

Re: CHAINING BATTERIES

Quote:<br />You don't really want to do a permanent hook-up of the two batteries unless they are the same age, brand, and cranking amps. Otherwise, one will want to always draw on the other. FWIW, trucks with larger diesel engines use permanently connected duel batteries, so we know it is done reliably.<br /><br />Absolutely! Incorrect battery match isn't good on the engine electrical system, either.

 

[LubeDude]

Re: CHAINING BATTERIES

Well, I guess CPUzone is on vacation.<br /><br />What I do in my bass boat is that I have two trojan Deep cycles which I bought at the same time that have the same manufacture dates wired together, +-+, ---, These are for my trolling motor. I then bought nice long battery cables and hooked the + side of the pair to the + side of my starting battery, then I put one of those tighten to connect battery switch ends on the - post, (My starting battery has both style hook-ups on it), then connected the ground cable. If I ever have any problems, I can tighten the switch and be able to start the boat, then unscrew the switch and not draw down the trolling batterys. Havnt had to use it yet, but I have the piece of mind that if I have a problem, Im good to go.

 

[Nikko]

Re: CHAINING BATTERIES

Interesting observation about having the batteries the same when doing a parallel connection. <br /><br />While I agree it's nice to have them the same, I'm not convinced it really makes much of a difference. Even if the batteries are different their load's will average and each battery will take/give what it can. <br /><br />On charging, when one battery hits full charge and if the other one is still in need of a charge, it will continue to charge. When both are full, neither will charge anymore. <br /><br />When the system requests power from the batteries, it will make the request through the battery cables and each battery will delver what it's capable of and for as long as it can. <br /><br />If one battery is charged more than the other , it will discharge until the charges in the two batteries are equal at which point they will diminish equally.<br /><br />I'm not saying it's not a good idea to have similar batteries in a system, but it's certainly not imperative. However, if you have one "good" battery and one "bad" batery in a system, the good one will constaly try and compmensate for the bad one and it's lifespan will be shortened. This is why it's a good idea to replace batteries as a set.<br /><br />Nikko

 

[LubeDude]

Re: CHAINING BATTERIES

Originally posted by Nikko:<br /> <br />While I agree it's nice to have them the same, I'm not convinced it really makes much of a difference.<br /> If you have one "good" battery and one "bad" batery in a system, the good one will constaly try and compensate for the bad one and it's lifespan will be shortened. This is why it's a good idea to replace batteries as a set.<br /><br />Nikko

Sounds like you are convinced to me.

 

[Nikko]

Re: CHAINING BATTERIES

...yeah, I guess it does <br /><br />I know it's better to have the same batteries, what I tried to say was that I don't think it's imperative or critical to have the same batteries. And I certainly don't think mis-matched batteries will do any harm to a charging/electrical system. The system may not be as effieicnt as it could be, but it won't get damaged.<br /><br />But I guess I never really said that <br /><br />Nikko