I’ve been lurking in the background on the forum for a little while. It seems like there’s a wealth of knowledge on this subject so maybe I can acquire some . I am digging for information on installation of a Minn Kota power drive 70 on a 19 ft Sundance skiff with a 70 horsepower 2003 Suzuki the issue I’m concerned about is I would like to go with lithium 24 volt system for my batteries but I do not have the option of plugging in when I returned to the dock so I would like to attempt to charge my trolling motor batteries as well as my starting battery from the motors alternator from what I can determine the alternator puts out 27 amps at 3,000 RPM approximately five of that is utilized by the motor systems and the only Electronics I run are a single depth sounder. Does anyone know if this application is even possible to complete utilizing a DC to DC charger. I don’t want to burn out my alternator. Even if I’m just extending my trolling motor run time and have to every few trips remove the trolling motor battery for charging at home, that was sort of the purpose of my going with 24 volt 50 amp hour lithium knowing that I can always add another to extend my run time and they only way about 22 lb so removing them for charging is a pain in the neck but it’s not the hardest task. Any Guidance would be greatly appreciated
Common DC-DC chargers, including those offered by Victron, are expressly battery-to-battery chargers, so they require a battery on the input side with that battery being charged by the alternator. They are not to be connected directly to an alternator.
There are alternator-to-battery chargers available from various manufacturers; Sterling Power comes to mind for that as a fairly reputable brand.
Personally, while I’m a huge proponent of LFP, I’d never advise that it be the only chemistry onboard any kind of vehicle - instead, I’d always advise having even a small Pb starter battery onboard that could hopefully at least help get you home in the event that the BMS of the LFP battery decides it needs to shut down. If you have a small Pb starter battery being charged by your alternator, you could then put a small battery-to-battery charger between it and your LFP battery to keep the LFP battery charged while underway.
Your alternator is very low-output relatively speaking, so you’d either need a very small Orion-Tr Smart or you could use an Orion XS1400 with its output current dialed down substantially.
My two cents… YMMV and all that, and if in doubt have a chat with one of your local marine electricians.
I appreciate the quick response I have extremely limited knowledge on lithiums and they’re charging systems or what they require other than what I’ve been able to pick up reading online I do have a group 27 lead acid as a starting battery and I was aware that whatever charging system I use hooks to the lead acid and the charger then feeds my 24 volt lithiums. I was looking at a victron Orion 12/ 24/ 15 amp unit but with my limited knowledge I didn’t know if was just going to pull down my starting battery to charge the lithiums until the starting battery hit the set limit for shut down and then nothing. I’ve tried reaching out to my local dealers I’ve got some response but nothing detailed.
Aha, okay… yeah, so you’re certainly onto a better track there, I didn’t understand that you do still have a Pb starting battery.
I wouldn’t personally suggest a 12/24-15 because to deliver 15A on the 24vNom side it’s going to be pulling ~32-35A from the 12vNom side, which is already over the maximum output of your alternator and, too, a general rule of thumb is to never exceed half the rated maximum output of your alternator as a continuous load. That varies by alternator manufacturer and design, some alternators -especially marine alternators- can handle more than half their maximum as a continuous, but that will be up to you deep-diving the alternator specs. Either way though, the 12/24-15 will be too much for the alternator you have no matter what.
You might be able to squeak by with an Orion-Tr Smart 12/24-10, but I think even that might be pushing it especially since you mention the alternator is already supplying ~5A to other loads; I’m not usually one to push the XS series, but in this case I think the XS1400 might be your best bet, since that one you can dramatically dial down the current that it’s pulling from the input side, which you can’t do on the Orion-Tr Smarts (or let the XS1400 dial itself down if it sees input voltage dropping due to the alternator not keeping up with its load).
Have a look at the user and installation manual of the XS1400 to get a sense of how it works / its configurability and see if that might work for you: Manual - Orion XS 1400 DC-DC battery charger
Justin I just did a quick peek at that Orion component you just recommend it and holy cow that thing can be dialed all the way down to 1 amp on the input side I didn’t realize that was a possibility I’m going to read into it thoroughly from here out but I really appreciate it that might be just what the doctor ordered if my alternator is only putting out about 20 amps after motor consumption and I can dial that unit down below 10 amps that might just increase my run time on the trolling motor batteries without killing the alternator and the cost is not much different than the other chargers I was looking at