Added a second battery, drained both! (BATTERY HELP)

[Miitch]

Below is a sketch (pardon my lack of artistic skills) of my new battery set up. Original battery, positive wired to a on/off switch, negative ran straight to boat electronics. I added a second battery which I just wired in parallel to the original. Both were fully charged upon installation. I checked that electronics were working, then turned the kill switch off, and left it for the night. Next morning, boat was almost completely dead - wouldn’t even start.
Am I missing something? Should I replace the existing on/off switch with a 1, 2, 1&2, switch?? Would this set up work if I wired both battery positives to the kill switch??
Trying to add power for an upcoming speaker upgrade I’m doing.

 

[Troch1]

Below is a sketch (pardon my lack of artistic skills) of my new battery set up. Original battery, positive wired to a on/off switch, negative ran straight to boat electronics. I added a second battery which I just wired in parallel to the original. Both were fully charged upon installation. I checked that electronics were working, then turned the kill switch off, and left it for the night. Next morning, boat was almost completely dead - wouldn’t even start.
Am I missing something? Should I replace the existing on/off switch with a 1, 2, 1&2, switch?? Would this set up work if I wired both battery positives to the kill switch??
Trying to add power for an upcoming speaker upgrade I’m doing.
View attachment 128348

Pretty sure you just created a 24v single battery with your setup. Remove the positive connecting wire that links the two batteries. Get yourself a two battery switch and wire both positives to that. Then you link one leg on the switch to the engine and the other leg to your “house” items (stereo, bilge, lights).

 

[blthlt]

You made a larger battery by wiring them in parallel. If you turned the kill switch off, everything should be isolated from the battery(s) which should stop things from running dead. Are you trying to have a house and a start battery setup?

 

[VitaminSea]

IMO, yes you need a A & B switch as you inquired about.
Wiring two batteries in parallel without a charger will drain them.
There are others on here who can explain this better than I.

 

[blthlt]

https://jetboaters.net/threads/add-a-battery-mod.28505/post-466841 follow this link to a Dual Switch w/ DVSR setup.

 

[Miitch]

You made a larger battery by wiring them in parallel. If you turned the kill switch off, everything should be isolated from the battery(s) which should stop things from running dead. Are you trying to have a house and a start battery setup?

My goal was just to have a “larger battery”. Just so it didn’t die while anchored playing the music through the new speakers. The switch was off, and then the next morning both batteries were dead. So a new 3 way switch is the way to go ??

 

[ChrisM]

This is what Chaparral equipped my boat with. The yellow section at 4 O'clock is the combine battery setting. The black box below the switch is an auto charging isolator, it will charge the battery in need, then the other.


BLUE SEA SYSTEMS Mini “Add-A-Battery” System | West Marine


Add-A-Battery Kit - 120A - Blue Sea Systems

 

[Inthrustwetrust]

My goal was just to have a “larger battery”. Just so it didn’t die while anchored playing the music through the new speakers. The switch was off, and then the next morning both batteries were dead. So a new 3 way switch is the way to go ??

I would 3 way switch and leave one as a start battery and one as a house battery to power the toys. Depending on your sound system and batteries. While it may not be your desired outcome, having a isolated start ensures you have a good battery to start the engine. If you go the “giant battery” way you run the risk of draining both batteries and being stuck.

Ideal situation is get a high capacity battery for your house. You also want to get a good battery tender/charger, these boats have stators that don’t have the power to fully top off a drained battery (which a amp pushing some power will do) I got a Noko mini genius, $150 ish on amazon.

 

[Miitch]

Thanks everyone for the Quick reply! On vacation this week and now I don’t have to spend it looking at my boat in the driveway I have ordered a 3 way switch. Hopefully it’s all set up by the end of the week!

 

[Miitch]

I would 3 way switch and leave one as a start battery and one as a house battery to power the toys. Depending on your sound system and batteries. While it may not be your desired outcome, having a isolated start ensures you have a good battery to start the engine. If you go the “giant battery” way you run the risk of draining both batteries and being stuck.

Ideal situation is get a high capacity battery for your house. You also want to get a good battery tender/charger, these boats have stators that don’t have the power to fully top off a drained battery (which a amp pushing some power will do) I got a Noko mini genius, $150 ish on amazon.

This three way switch is the route I am going to take. Both batteries are trickle charging Right now outside of the boat. The amp is only ~500 watts. boat is small, only 4 speakers. So shouldn’t really drain it but better safe than sorry. If I do this, will both batteries be charged when driving the boat on the A+B battery setting on the switch??

 

[AZMark]

Yes both will charge if the switch is combined.

Something was wrong with your setup to drain like that. Either your existing battery was already in bad shape or something got wired wrong. I’d figure that out before moving on.

 

[AZMark]

Good idea to also move either your boat ground or your hot to the opposite battery.

 

[blthlt]

looks like per his diagram the engine was the thing that was isolated, not the load off the batteries.

 

[Miitch]

Yes both will charge if the switch is combined.

Something was wrong with your setup to drain like that. Either your existing battery was already in bad shape or something got wired wrong. I’d figure that out before moving on.

I have both batteries being charged separately right now. Hopefully if there’s an issue with one holding a charge, I’ll notice it.

 

[ChrisM]

Read the description for the (ACR) on the second link I posted above for the 120A setup.

 

[biffdotorg]

Pretty sure you just created a 24v single battery with your setup. Remove the positive connecting wire that links the two batteries. Get yourself a two battery switch and wire both positives to that. Then you link one leg on the switch to the engine and the other leg to your “house” items (stereo, bilge, lights).

Agreed, that a battery switch with ACR is the best route to go to isolate your batteries. But no, this is the way you would wire two batteries together to double the amperage but keep the same voltage. His diagram is parallel. If wired in series (pos to neg) you would double the voltage but keep the same amperage. With a switch and only two batteries, you would not do this, but it would be correct without a switch (minus protection from draining your starting battery). There is no real reason he should have burned up both with a stock system, unless something was left on and drained it.

Even with a battery switch, some will take their house bank and put multiple batteries on in Parallel to multiply the amperage, but keep it at 12v. You would have to have thousands of watts to justify that though.

I run a two bank switch with a group 27 on each bank. And I run a 1000w amp off of that one battery all weekend without issue.
I run the same pair of group 27 in Series on my boat lift, as it is 24v, and it allows my 5000lb lift to run most of the summer on 1-2 charges, as the motor runs more efficiently than a 12v with double the amperage.

Good luck!

 

[212s]

Something was wrong with your setup to drain like that. Either your existing battery was already in bad shape or something got wired wrong. I’d figure that out before moving on.

I agree something was wrong with the wiring - simply adding a second battery in parallel should not cause any issues unless the original battery setup had draining problems. Most likely something is still drawing power with the power switch off and you connected something wrong.

Having a dual battery setup with the ability to have a separate house and start battery is the best option as the start battery is always isolated so you can always start your engine. But simply having dual batteries of the same type in parallel (1 bank) works to double power reserve and can be charged as a single bank without issue. If you have 2 batteries of different type, it's best to charge them separately.

 

[blthlt]

My goal was just to have a “larger battery”. Just so it didn’t die while anchored playing the music through the new speakers. The switch was off, and then the next morning both batteries were dead. So a new 3 way switch is the way to go ??

My recommendation is to have 2 batteries. 1 for the radio and other power needs (12v outlet, lights, etc..) and 1 battery for starting ONLY. Using a dual battery switch, that has the option to have the batteries separated or combined. That way you can have just the house battery running while sitting at the sand bar without ever the chance of running your starting battery dead. Once ready to leave, you can combine them to charge both while under way. And to make it all easier, a DVSR will make all this automatic for you.

 

[Miitch]

*UPDATE* thanks to everyone for the quick fix! I love this forum. I appreciate all the responses.

I was able to order a new switch (3 way) yesterday on Amazon and had it delivered today! Installed the switch and did what was mentioned above. Both batteries are wired via negative terminals, both batteries are wired to the three way switch. House appliances are all on one battery, engine is on the other.

 

[blthlt]

Keep in mind that if this switch doesn't have an OFF position you'll have potential issues with any parasitic draw. This is a 4 way that shows the OFF. Cant tell in your photo if you have that option or not.