I've got five Deka Batteries in the boat. Two connected in parallel for starting and electronics and 3 connected in series for the trolling motor. They are connected to a Minn Kota MK 440D on board charging unit.

I noticed that one of the indicator lights on the charger is solid yellow and has been for over a week.

Nothing in the manual addresses this.

So does anyone know if it's a bad battery or something wrong with the charger?

I am getting low voltage alarms when starting the main motor after using the electronics for a while.

I had the same problem, I had an inline fuse block that was bad. I changed the block(not just the fuse itself) and my problem is fixed. The block had a little burn mark on the inside.

Thanks. I checked the fuse and it was good. If I pull the fuse the light goes to red.

You need to check the fuse block. Not the fuse. Mine had a small burn mark on it and my light was staying yellow and actually not charging my battery. Once I changed the fuse block problem solved.

Possible bad bank, bad battery? Change out the bank not greening up with another to see if it's the battery.

Just went and checked and now it's charging.

If a battery gets to low it will create the same issue as a bad battery.

OWNERS MANUAL, page 5, lower left: Yellow Light (not flshing) = Charging in bulk mode. Maybe look again?
Note that MK doesn't have any illustrations of two batteries charged in parallel on one bank output. That's because chargers can't do this. One set of leads can't deliver charge current to two masters....

I do not recommend leaving 2 batteries connected in parallel. Doing so will insure that the poorer performing battery (that discharges faster) will pull down the better battery. in other words, one batter will kill the other in time. Also, when a battery goes to FAIL, it will have such an impact on the other battery that you may likely not have enough power remaining to get your outboard started. I'm guessing you want reliability and redundancy, but what you've done accomplishes quite the opposite.

There's a reason that main battery switches have a "1" (only) and "2" (only) position! There some options on the details of how a proper redundancy/reliability system should be set up, but NONE permit the two boat/motor batteries to simply be connected in parallel.

If you don't want to use a battery switch, connect the outboard to one battery. What else you may or may not connect to that battery is a personal choice. I would connect the standard boat harness to this battery also (pumps, etc.). The second system battery could power all electronics and auxiliary lighting, for instance. This setup helps avoid one failing battery from killing the second battery simply because they are now isolated. You could use jumper cables briefly between the two batteries for a stranded boat starting scenario and hope for the best. I'm not a fan of this configuration due to its weaknesses.


Battery Switch Option: This configuration is my favorite, but there are multiple ways it can be done. Connect everything (+ lead for boat/outboard/electronics/lighting loads) to the "Load" terminal of a battery switch. Connect one battery + to BAT 1 and the other battery + to BAT 2. All grounds connect to both batteries. If Battery 1 gives you trouble, you can switch to BAT 2 for a fresh fully charged backup battery to start your outboard, then switch back to BAT 1 to charge it. Your BAT switch must have a "combine" feature so that it combines both batteries momentarily as you switch between batteries. (Most do this.) Never turn the switch OFF while an outboard is running. This typically results in electrical damage for most motors - I'm not an expert on details about any exclusions, but its safer to just never do it.

You'll need 5 banks of battery charger capability to wire as described above. MK never intended for two batteries to be connected to one bank. The light was yellow a long time probably because it was having trouble charging a poor battery in parallel with what will soon be a second poor battery. Since you already have a 4 bank, you could add a single bank, but the parallel battery connection configuration you have now will have to go.

flippin, I hate to short circuit your post but perko switches with dual capability also include an all position, this connects both batteries in parallel.

you can charge dual batteries from one charger link while both are connected, it results in half the amperage going to each (more or less) and takes twice as long to charge if not longer due to very low battery.

get ya a perko switch like above, hook each to it as instructed in directions, connect your charger leg via a 30 amp rocker switch dpdt (double pole double throw, on off on) using a fuse to each battery, you will just have to switch the charger over once one battery is charged. use the perko to isolate the batteries for charging.

this allows you to run on both, charge individually. charger switch can be on underside of console or somewhere out of the way and dry as possible.

pm me streetwalker if ya need help with hookup, I will do a diagram for ya.

Connect the charger to the battery`s via the perko switch would be the easiest.

I don't think Flippin suggested there wasn't an all position. You would be hard pressed to find a 2 battery switch that did not have an "all" or "combine" switch.

There are pros and cons to paralleling two batteries.
Flippin does a good job explaining the cons , which usually out weigh the pros on a bass boat compared to a diesel truck that HAS to have two parallel batteries to start the engine.

I also agree that the charger is not designed to charge two batteries in parallel. You can get away with it with for a while with new batteries, but it is downhill from there.

In the end you are all correct, a switch is the best solution.

Some engines have auxiliary charging leads that can charge the 2nd battery after the primary battery is charged on the fly.

To the OP, it is most likely that one (possibly both) of the batteries is defective and the charger cannot achieve the voltage level necessary to communicate to the charger that they battery(ies) are charged and that it needs to shut down. The batteries need to be separated (unparalleled) and a volt meter or load tester used to check things out, including the charger's capabilities for that bank.
If wet cells, chances are one or both batteries are low on water due to excessive charging.

Good luck to all.

I am very aware that most battery switches have a "BOTH" setting. The trick is knowing the most intelligent way to use the switch and why the various settings are offered. My post was already getting long, so I didn't quite cover everything in the detail level I'm accustomed to using. I never said a user should not use a "BOTH" selection on a battery switch. I said that 2 batteries should not be left connected in parallel continuously. I should have clarified that "BOTH" is best used only temporarily when you need to get extra power to start your outboard. Using BOTH setting is like connecting two batteries with jumper cables. I highly suggest that if BOTH is used in a starting-problem scenario that the switch be moved back to a single battery position, usually the primary starting battery so that it can be recharged.

As a battery ages and begins to falter, individual cells lose their ability to reach a full charge voltage no matter how long a charger is connected, or what amperage is used. If you attach such an aging battery in parallel to a good/new battery, then the older battery will begin to immediately degrade the new battery - the low cell voltage on the old battery will discharge the new battery, pulling it's charge level and voltage down in the process. This is why normal operation should be to select a single battery, not "BOTH". If connected all day (on BOTH) you can find yourself with one bad battery that won't start an outboard and what used to be a good battery now discharged by the bad battery. You'll be sitting there with TWO batteries in such poor state of charge that they can't even start the outboard together. If those same two batteries are used when the boat is generally operated on "1" or "2", you later have the option to temporarily switch to "BOTH" and fire right up to go home.

You're also correct that you can rig up a DPDT circuit so that two batteries can be charged with one charge circuit. However, the owner loses something in that process. Many chargers have a cycle they follow that includes a periodic desulfation and maintenance mode. Having N charger outputs for N+1 batteries means that one battery doesn't get the level of care that the others do. Many would be prone to forget to flip the switch to insure both batteries get adequate charge. If someone wants to run 5 batteries, they'll replace them less often and have less trouble if they use 5 charger circuits. The most common way to get this is a 2 bank charger and a 3 bank charger. While there are some 5 bank chargers, the cost is premium and replacement units are not readily available. Two and 3 bank units are common, so that's the most sensible solution not requiring the owner to remember to flip a switch from time to time.

LOSTTEXAN is correct that some outboards offer two independent charging circuits that can be connected to a dual battery setup even when a battery switch is used and set to "1" or "2". That's an ideal setup as it gives you the best chance of never being stranded because of inadequate starting power.

This is not that complicated. Streetwalker get your battery`s load tested.

The problems ARE more complicated when keeping multiple batteries connected in parallel. Even if he gets the batteries load tested and they both pass the test, the two of them aren't exactly equal. One will draw the other down to some extent if they are placed in parallel and left that way. Once the poorer battery gets worse, it will drain the good battery even more rapidly and more deeply. One day he will eventually have two batteries, neither of which will get his engine started to get home.

If one battery is bad and he replaces it, again the two are not equal. The older battery will degrade the new battery, and the problem cycle eventually happens again in the future. The newer battery will die sooner because it too will eventually be degraded by the remaining older battery.

By all means do as you wish. I'll keep my properly configured electrical system in place and add another year to my ~37 year streak of never being stranded on the water. I do carry tools and jumper cables just in case, but I always seem to be using them to help "that other guy" who is stranded.