Batteries in parallel for reserve capacity

[Dave Mulder]

I am currently running 3 Humminbird Helix 9's in my boat. Near the end of a big day of fishing i am loosing power to the units. My current battery set up is one starting battery and one house battery for electronics which is a few years old, Not linked together (One optima blue top(AGM) and one conventional marine battery)



My question is....if I buy 2 new group 24 batteries with 120 min reserve capacity and hook them in parallel will ultimately double my reserve? As well with them being hooked together my Yamaha 115 should charge the batteries a bit while i am running around the lake?



Thanks Dave

[WallyWarrior]

You go positive to positive then neg to beg. Then hook stuff up to single battery. It will double the battery capacity. The worry would be that if you drain both will you have a way of starting your main?



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[JOHN L. HECKLSMILLER]

Dave: I have ran 2 batteries in parallel with my rig for over 30,00 miles on LOTW. I can honestly tell you that I have never had battery failure. ( https//www.walleycentral.com/forums/showthread.php?=5845370#post5845370 ) the purpose of 2 batteries in parallel is to give U more "Capacity" & it does its job! ( https//www.walleyecentral.com/forums...ictureid=22961 ) Set the Hook, CRJohn

[GBS]

Ditto -
Your motor will replace about the same amount of energy used as it did before. But now you are asking it to recharge two batteries - so depending on lots of factors, you may not get either fully recharged, so still would need a charger.

The thing about batteries - in general, for starting a motor, you want "CCA" - cold cranking amps. Meaning they can deliver a high amount in a very short period of time. For lower, but longer loads (like your HB's), you want RC (Reserve Capacity). In most batteries, you get in increase in one, at the expense of the other.

With changing to having the two batteries in parallel, IF they are the same specs as before, you will be pulling some additional energy out by staying out longer. So there is a potential for not having enough to start your motor at the end of the day. I'd shop for batteries that have a CCA at least as much as your current starting battery AND an RC for each that is higher than your current single battery.

Or keep your current setup, but exchange the single electronics battery for two smaller (or one larger), where the combined RC is higher than what you have now.

It's a juggling act between cost, weight, size and capacities....

You don't note which is which - but if you are using the Optima for your electronics, there may be the issue. Despite their promotion, they are pretty inferior for RC. You can find much cheaper, with higher RC, for less money.

[Dave Mulder]

Thanks for the comments. I recently was able to turn my optima starting battery sideways and push to the back of the compartment. This allowed me to get a new house battery with 210 min RC in the compartment. This is an additional 50% more RC than I had before. I believe I should be set from here on out.

[DW]

Originally Posted by Dave Mulder

I am currently running 3 Humminbird Helix 9's in my boat. Near the end of a big day of fishing i am loosing power to the units. My current battery set up is one starting battery and one house battery for electronics which is a few years old, Not linked together (One optima blue top(AGM) and one conventional marine battery)



My question is....if I buy 2 new group 24 batteries with 120 min reserve capacity and hook them in parallel will ultimately double my reserve? As well with them being hooked together my Yamaha 115 should charge the batteries a bit while i am running around the lake?



Thanks Dave

Three Helix 9 draw only 3 amps. If your house battery runs low with such minimal load then you have a bad battery. For that light load, you don’t need two batteries in parallel. One will suffice. Get one group 31 instead which provides a large reserve for your needs. A house battery should not be connected in parallel with your cranking battery so that you don’t risk depleting the cranking battery. If you want the ability to charge your house battery with your outboard, use a combiner instead of a parallel connection so you don’t deplete your cranking battery.