Minn Kota MK440PC battery charger question

[Jeff Homan]

I have one of these 4 bank chargers in my BassCat. I have 3- 111 amp K-2 Energy Pro Lithium batteries for my trolling motor & a 31 AGM for my cranking / electronics. I have three of the K-2 smart chargers, can I just pull a fuse on the three legs from the minnkota going to the K-2s if I don't want to use it to charge the K-2s and still use the one leg to charge the AGM? If I'm going to fish the next day I use the Minnkota to charge them all because the K-2 smart chargers are only 4 amp chargers. If I'm going to be a day or two between trips I would like to use the smart chargers for the K-2 & the MinnKota for the AGM.

[bruce']

You can just pull the fuses,
I would leave them and just use the charger, As needed.

[Jeff Homan]

Thanks, gotta figure something out, may put a waterproof toggle switch on each of the three legs from the MinnKota to the K-2's so I can just cut those legs off when I want to use the smart chargers.

[Ann-Marie]

With the Trollbridge36-LITHIUM your AGM charging sources (alternator or shore power) will charge all 3 Lithium batteries (I'm assuming they are running a 36 volt motor). Then any time your main motor is running all the trolling batteries will be getting a charge, in most cases making you independent of shore power

[wmitch2]

With the Trollbridge36-LITHIUM your AGM charging sources (alternator or shore power) will charge all 3 Lithium batteries (I'm assuming they are running a 36 volt motor). Then any time your main motor is running all the trolling batteries will be getting a charge, in most cases making you independent of shore power

^^^ THIS^^^

[bobcoy]

Are you afraid you might plug both chargers in at the same time? If only one is used at a time I doubt you need to disconnect anything. Maybe an engineer could give you a more informed opinion. Bob
Addendum: I asked Minn Kota if it was ok to leave my DC to DC charger hooked up when I installed my 460PC charger. He said as long as both were not being used at the same time it is not a problem I think that is the same situation.

[Jeff Homan]

No I would like to be able to charge the AGM using the MinnKota charger while using the three K-2 smart chargers to charge all three lithiums at the same time. From what I have read, the MinnKota will charge the Lithiums if its set on the AGM setting, but will cut off before the lithiums reach their full voltage charge. The K-2 smart chargers are made specifically to charge the lithiums to their full voltage charge. The K-2 chargers are 4 amp chargers, so if I'm fishing the next day, I'll have to charge the lithiums with the MinnKota as it's 10 amps per bank.

[bobcoy]

You will have to alter your plan then. Can't have both chargers going to your Lithiums at the same time. If you need to top of your Lithiums just put your K-2 chargers on after your turn off your Minn Kota. It cant take long to top them off. I use the Minn Kota 460 PC and get over 96%. For me that 4% is meaningless and the batteries are happy being less than 100%. If you are running short on power by the end of the day I guess you have to use the additional chargers. Bob

[Lou r Pitcher]

DPDT switch (at the proper current rating) is your friend.

[Jeff Homan]

DPDT switch (at the proper current rating) is your friend.

That was my original thought.

[Ann-Marie]

Until someone can come with an explanation why you can't have multiple chargers working in parallel I'll continue to use them.
Both chargers switch to maintenance level after reaching 14.2 volts and I know the Lithium batteries are fully charged because the voltage suddenly rises at end of charge when the BatteryManagementSystem cuts them off.

All these experts repeat the myth but can't give you a reason why you shouldn't use multiple chargers. I can see if they are high current outputs that would exceed the maximum charging rate of the battery(ies) that would be justified.

[bobcoy]

Would the chargers be able to tell what the actual state of charge is with all different charger outputs? With Jeffs situation his 2 chargers are not going to hurt anything except they may shut down thinking the batteries are charged before they are. With other value chargers combined it might be over the .2C limit on AGM's . I noted that an engineer's opinion was warranted and now we have one. Bob

[Lou r Pitcher]

One of the undesirable results of combining multiple charger's outputs is that safe AC leakage currents would add and possibly reach unacceptable and unsafe thresholds.

Another undesirable outcome for an agm chemistry battery possibly occurs if some agm compatible charger models were to overpressure/venti the sealed battery if they were combined charging the same battery. When both charger models include a normal carefully time limited overvoltage equalization/plate cleaning period they could apply it in a staggered or sequentially staged manner causing the electrolyte to excessively gas.

[bobcoy]

Now we have 2

[Ann-Marie]

Would the chargers be able to tell what the actual state of charge is with all different charger outputs? With Jeffs situation his 2 chargers are not going to hurt anything except they may shut down thinking the batteries are charged before they are. With other value chargers combined it might be over the .2C limit on AGM's . I noted that an engineer's opinion was warranted and now we have one. Bob

Argument 1 rejected:- While it is true that no two (even identical) chargers will have the same threshold voltages for state of charge there is no reason why they should. Each charger is charging a battery and responds to the voltage it sees. It doesn't know or have to know that there is another charger changing the voltage, it just responds to the current status quo. If one charger decides the battery is charged and drops back to maintenance, the battery voltage may drop slightly but it doesn't suddenly drop to maintenance levels. The remaining charger will continue its charging program until complete.

Argument 2 accepted:- Of course you would make sure that the combined output of the charges dosen't exceed the maximum "C" rating limit.

Engineer count back to one. :)

[Ann-Marie]

One of the undesirable results of combining multiple charger's outputs is that safe AC leakage currents would add and possibly reach unacceptable and unsafe thresholds.

Another undesirable outcome for an agm chemistry battery possibly occurs if some agm compatible charger models were to overpressure/venti the sealed battery if they were combined charging the same battery. When both charger models include a normal carefully time limited overvoltage equalization/plate cleaning period they could apply it in a staggered or sequentially staged manner causing the electrolyte to excessively gas.

Argument 1 rejected:- DUH if your charger has AC leakage it should be repaired or replaced. This is unrelated to using two chargers, it applies to all situations.

Argument 2 rejected:- Matching charging profile of multiple chargers to the battery(ies) being charged applies to all charging situations. The profile will set the allowable charge current in response to the current stage set by battery voltage. With multiple chargers each one will see a higher voltage that it would had there been only one charger so they will cut back to follow the profile earlier. There will be many occasions when one charger cuts back before the other and essentially stops charging until the other matches the profile voltage at which stage both continue the program - albeit at a lower current that it would have if a single charger.

It is obvious from the above that two 10 amp chargers will not charge a battery twice as fast as a single since under numerous conditions one will abdicate for periods in later stages and leave the job to the other.

Argument 3:- Acknowledged - if both chargers have equalization timers that will not be synchronized there would be twice as many equalization episodes which should not do any harm so long as they don't follow each other in direct sequence.

I'm not yet convinced that there are any pertinent reasons to justify the paranoia about using multiple chargers. It is one of those Internet myths that gets handed down year after year without ever stopping to ask WHY.

And then there were none. :)

[bobcoy]

OK, back to the amateur. Since the AGM setting on the Minn Kota does not include an equalization stage, and total amperage does not violate any of the batteries limits there should be no risk of damage to any of his batteries. What remains is whether he gets a faster 100% charge of all 4 batteries batteries. I hope I have understood all the info provided here. Please let me know if do not have the grasp. If so Jeff should be good to go with everything hooked up and powered up(no switches). Jeff if you do it separately as you stated and then all at once after you run them for a day, please let us know if one way is better than the other. Thanks for all the professional information. Bob

[Lou r Pitcher]

Any Ac powered charger sold in the US market will have amounts of measurable AC leakage that must meet legal or industry standards such as UIL, possibly Good Housekeeping, city of LA and others requiring they are carefully designed, monitored and qa'ed providing the buyer a safety margin. Combining chargers reduces that safety margin when ac leakage currents are in phase and add.

[Jeff Homan]

I have never run all (4) chargers at once. If I am going fishing the next day after going today, I simply run the MinnKota 4 bank charger to get them all up over night. If I have days between trips I use the MinnKota to bring them all up over night, then I unplug it, and plug up the (3) K-2 smart chargers to top off the K-2 Lithiums until they go to green light. My real question was, if it would be ok to pull a fuse from each of the three legs going from the MinnKota to the K-2 Lithiums to stop current from going from the MinnKota to the Lithiums, so I could then use the K-2 Smart Chargers to charge the Lithiums at the same time that I charge the AGM with one leg of the MinnKota.

[H-D Dad]

Yes