Batteries Hooked In Parallel Questions

[MY2SONS]

I was considering hooking my two identical 12V batteries up in parallel to double my battery capacity when running my electronics when the main engine isnt running and charging them. My question is this. Since theyre hooked in parallel ( positive to positive, negative to negative) would the doubled amp hours affect my electronics in any way such as overheating the wires, etc. Also, I have a 3 bank charger on my boat and if the batteries are hooked in parallel would they have to be isolated from each other when being charged? Im hooking an AP to the batteries in parallel too because its controlling the kicker and the kicker doesnt charge the batteries when its running.

[SeaCatMich]

Having the batteries connected will not affect your electronics. The electronics are going to draw the amps they need to run -- having two batteries in parallel just makes one big 12v battery with twice the amp hour capacity. With the same load, double batteries will provide twice the running time.

As for the charger, only hook it to one of the batteries in the pair. It will charge both of the batteries but will take twice as long.

You will also want the batteries in the paring to be identical for best results. Both should be of the same size and of the same type (starting, combo, deep cycle). If they are of different capacities the larger one will only charge to the capacity of the smaller battery. Since starting batteries and deep cycle discharge differently you don't want to mix them in a parallel setup.

I have a similar setup on my boat but I have two batteries in parallel for my electronics and a separate battery for each of my two 90 hp outboards. I charge the two batteries each night and they last the whole next day running all of my electronics (three Raymarine 7" displays, 1 GPS, 1 VHV, FishHawk X4, & Autopilot) for 8-12 hours. I run my electric downriggers off of the engine batteries as their draw is too high in my opinion to run off the house/electronics batteries.

[MY2SONS]

Having the batteries connected will not affect your electronics. The electronics are going to draw the amps they need to run -- having two batteries in parallel just makes one big 12v battery with twice the amp hour capacity. With the same load, double batteries will provide twice the running time.

As for the charger, only hook it to one of the batteries in the pair. It will charge both of the batteries but will take twice as long.

You will also want the batteries in the paring to be identical for best results. Both should be of the same size and of the same type (starting, combo, deep cycle). If they are of different capacities the larger one will only charge to the capacity of the smaller battery. Since starting batteries and deep cycle discharge differently you don't want to mix them in a parallel setup.

I have a similar setup on my boat but I have two batteries in parallel for my electronics and a separate battery for each of my two 90 hp outboards. I charge the two batteries each night and they last the whole next day running all of my electronics (three Raymarine 7" displays, 1 GPS, 1 VHV, FishHawk X4, & Autopilot) for 8-12 hours. I run my electric downriggers off of the engine batteries as their draw is too high in my opinion to run off the house/electronics batteries.

My boat has a 3 bank charger. One for each of the deep cycle batteries that are used for the electronics, and one for the starting battery. Can the two banks still be used for the two batteries in parallel?

[SeaCatMich]

My boat has a 3 bank charger. One for each of the deep cycle batteries that are used for the electronics, and one for the starting battery. Can the two banks still be used for the two batteries in parallel?

No, I made the mistake of doing that on my setup and it was bad. When you connect two batteries in parallel they become one big battery and should only have one charger lead connected. You could disconnect one of the lines between the batteries to isolate them when charging and have a charger line going to each battery. When the charger is not running having the leads connected will not make any difference -- just don't forget to uncouple the batteries before turning it on.

[MY2SONS]

No, I made the mistake of doing that on my setup and it was bad. When you connect two batteries in parallel they become one big battery and should only have one charger lead connected. You could disconnect one of the lines between the batteries to isolate them when charging and have a charger line going to each battery. When the charger is not running having the leads connected will not make any difference -- just don't forget to uncouple the batteries before turning it on.

Thanks for the advice. That helps a lot.

[1mainiac]

Ryan is correct and you may also need to consider some of the triple bank charger setups are isolated internally to allow you to charge 2 batteries in series at at 12v ea. Any load bank will be based off the weakest battery so hooking a new battery to a old tired battery will only give you the power of two old tired batteries.

[MY2SONS]

Ryan is correct and you may also need to consider some of the triple bank charger setups are isolated internally to allow you to charge 2 batteries in series at at 12v ea. Any load bank will be based off the weakest battery so hooking a new battery to a old tired battery will only give you the power of two old tired batteries.

Tbe two batteries in parallel are brand new.

[MY2SONS]

Ryan is correct and you may also need to consider some of the triple bank charger setups are isolated internally to allow you to charge 2 batteries in series at at 12v ea. Any load bank will be based off the weakest battery so hooking a new battery to a old tired battery will only give you the power of two old tired batteries.

Does it usually specify if the batteries are isolated internally on the charger? Ill have to dig up the paperwork on the unit to see if I can find anything on it. Appreciate the advice.