Charging question

[tollycraft]

I installed a second fishfinder in my boat which is networked to my other fishfider. The new one is quite a bit more powerfull at 8000 watts. Problem, when I went out on the water for the first time all was working well untill I shut down one engine to troll and I then lost the bottom readout on both (their networked so that was expected, if one didn't work neither would the other). I returned and put in a separate fuse buss and wired it directly to the battery and now only run the 2 fishfinfers on that fuse buss (which is what I should of done in the first place). Now, I havn't had the chance to go out since but believe the problem is solved. I have three batteries hooked up in series, when I ran only one engine while parked at the dock all worked fine (the fishfinders),but when I checked all three batteries I got different readings. Example, while running the port engine I got 13.5 Volts on one battery, 13.5 Volts on another and 14.5 on the third. Whe I ran the starboard engine only, again I got 13.5 Volts on two batteries and 14.5 on a different battery. Two batteries are new last year and one is new this year. I used a load tester on all three and all are good. I can't understand the one Volt difference. Maybe I'm concerned about nothing here but just can't understand why. Electronics are certainly not my strong point so I'm at a loss. Should I be concerned here or can someone give me an answer.

 

[Sea Gull]

Well, since you are running 12v (nominal) batteries you probably don't have them in series. This would result in a 36v circuit. It is also more normal to have two separate battery banks one associated with each of your engines. One of those banks might have two 12v batteries in parallel (still 12volts but double the amps). This is born out by your report that as you run each engine, one of the batteries indicates that it is being charged. Your problem may be in the connection between that third battery and its mate. At least that is where I would start.

Can you be more specific about your setup? It would help give a more specific answer.

 

[Asureyez]

8 Kilo watts! Sheesh my whole 46ft boat runs on less, and that includes two AC units all my electronics etc. You're gonna need a LOT of battery power for that sucka

 

[tollycraft]

Well, since you are running 12v (nominal) batteries you probably don't have them in series. This would result in a 36v circuit. It is also more normal to have two separate battery banks one associated with each of your engines. One of those banks might have two 12v batteries in parallel (still 12volts but double the amps). This is born out by your report that as you run each engine, one of the batteries indicates that it is being charged. Your problem may be in the connection between that third battery and its mate. At least that is where I would start.

Can you be more specific about your setup? It would help give a more specific answer.

My mistake, all three are hooked up in parallel. I think you hit the problem on the head. I know I should have (but didn't) check the connections on all the batteries. They all looked good but that doesn't mean anything. I will start there. Thanks for the advise.

 

[Kurt]

From experience with this I know that all battery storage capacities in parallel should be rated the same

 

[tollycraft]

From experience with this I know that all battery storage capacities in parallel should be rated the same

I agree.

 

[tollycraft]

Thanks all for the imput. I found the issue. Two of the batteries are hooked in parallel, one is not. One battery is dedicated to the port engine and can still be started with the battery switch off. The other two are house batteries and start the starboard engine. I now have the batteries labeled (should have known this in the first place, which batteries do what, duh) So, the explanation is simple now, when the port engine is running it's showing a charge of 14.2 volts and the others stay at about 13.4. (as they are not charging) When I'm just running the starboard engine, both the other batteries are showing 13.8 plus while the while the port engine drops engine drops in voltage. The only time all three are tied together is when I hit the emergency start button. Took a while to solve but I feel better now. Only posting this that in the event someone has a similiar problem with voltage differences, this is a place to start. This was one of those things that I should have taken the time to varify when I got the boat but didn't. Just another example of knowing your boat better.