Battery Help

[Joel_34]

Background: My 2014 350 SLX has a SureShade, table that raises from floor and engine hatch cover that have all slowed down. First the Sureshade stopped working, then the table, and now my hatch cover moves slower and slower. There are 5 batteries: 1 each to start the 2 inboard engines, 2 deep cycle and one long red battery. I thought the red battery was the house battery and the others for the engines. The red battery shows 12 volts. The deep cycles show only around 8 volts.
Questions:
1) what is difference between red battery and deep cycles? Are they all "house" batteries?
2) obviously the 8 volts is a problem. How do I know if it is batteries or charger? Since red battery is at 12 volts the charger must be working and replace batteries?

 

[Craig]

Picture? Red battery sounds like a 4 or 8D.
When we're batteries last replaced?

 

[dwna1a]

Optima Red Top? A photo would be great for understanding what you have.

 

[Stee6043]

One of these guys is a cheap tool to add to your box. Can test batteries, chargers and alternators.

https://www.amazon.com/Neiko-40510A...520133&sprefix=battery+tester,aps,185&sr=8-14

 

[paulswagelock]

Ok, so that battery needs replaced. But you need to do some research on your batteries and charger and how it is connected to the batteries. Do you plug into shore power every day?

 

[Joel_34]

I will grab a photo this morning. Yes I plug into shore power everyday. I bought this boat June last year so not sure of battery age. The two in question have a yellow sticker that says “8/16” so assuming that is correct, 4.5 years old. Can’t tell on the red one. Picture soon!

 

[Joel_34]

One of these guys is a cheap tool to add to your box. Can test batteries, chargers and alternators.

https://www.amazon.com/Neiko-40510A-Volt-Battery-Tester/dp/B07B3R4TS6/ref=sr_1_14?crid=1QH704YXL83S5&dchild=1&keywords=battery+tester&qid=1614520133&sprefix=battery+tester,aps,185&sr=8-14

Ordered!

 

[Joel_34]

Here are the pictures... appreciate everyone’s opinions and help!

 

[Craig]

Can't say I'm familiar with that. Kinda looks like a lith ion battery. Do you have a bow thruster?

 

[paulswagelock]

Ok, so the red one is a 4d or 8d. 12v is low. A good battery at rest should hover around 12.7 volts.
So you have some options. The first thing you need to do is figure out what each battery powers so you understand what the needs are for the battery. Second you need to understand what the battery charger connects directly to. Third you need to diagram the ACRs to see what they connect for charging.
A simple test is to turn all battery switches off. Document voltage at all 5 batteries. Then turn on charger and document voltage again at all 5. The charger should send the voltage up to the range of 13.4-14.5 volts. Second, shut off charger, turn all battery switches back on but make sure no load is turned on. Measure all battery voltages. Then start motors, bump idle up to 1800 rpm, then measure all battery voltages. the combination of these two tests will at least let us know what charges from where if everything is working. Best plan would be to trace wires and draw out the connections.

 

[Joel_34]

Can't say I'm familiar with that. Kinda looks like a lith ion battery. Do you have a bow thruster?

No bow thruster.

 

[techmitch]

One of these guys is a cheap tool to add to your box. Can test batteries, chargers and alternators.

https://www.amazon.com/Neiko-40510A-Volt-Battery-Tester/dp/B07B3R4TS6/ref=sr_1_14?crid=1QH704YXL83S5&dchild=1&keywords=battery+tester&qid=1614520133&sprefix=battery+tester,aps,185&sr=8-14

That tester is too small for most marine applications. It only applies 100 amp load,
(you need at least 200) and it even says right on the front of it "for under 200 cid (3.6L) use".

 

[Stee6043]

That tester is too small for most marine applications. It only applies 100 amp load,
(you need at least 200) and it even says right on the front of it "for under 200 cid (3.6L) use".

Worked fine for finding two bad group 31 batteries on my boat. And diagnosing a bad bank on my 40A charger. So...there's that I guess

 

[techmitch]

Worked fine for finding two bad group 31 batteries on my boat. And diagnosing a bad bank on my 40A charger. So...there's that I guess

I understand completely but keep in mind, a borderline battery may pass with that tester but will fail with the correct tester as a correct test would be 200 amps for 10 seconds.