On Board Chargers....Helpppp

Well I decided to start here since I come here with truck problems figured why not bring the boat into it as well lol. So here's the deal, in the near future I am planning to pick up two deep cycles to wire up in parallel to run my 12v trolling motor with double the capacity. With that I'm planning to pick up an on board charger so I don't have to pull the damn things out of the boat to charge them anymore. So a few questions, being that I will have 2 batteries in parallel would I need to get a 2 or 3 bank charger to charge both trolling motor batteries and my cranking battery? My thought was that since it will still be a 12V system it would be considered just a single bank and a 2 bank charger would take care of all 3 batteries. Is this correct? and if so, will charging the batteries while they are in parallel like that hurt either the batteries and or the charger? or will it just take longer to charge them? Now all of that said and if my thoughts are correct, what brand/amperage do you guys recommend for a charger? Any input is greatly appreciated!

 

Hey Travis. I was cruising this section and think I can help. I build boats for a living, so I deal with this on a regular basis. If you have a cranking battery and a set of paralleled batteries for your trolling motor, you will need a 2 bank charger. You would connect 1 of the charger leads to one of the paralleled batteries and the other to the cranking battery. Charging batteries in parallel isn't detrimental to the batteries it just takes longer seeing that you have essentially just doubled your reserve capacity. Depending on equipment connected to your cranking battery, they aren't typically difficult to maintain. It is used to start the engine, then the engine usually generates enough surplus output current to charge the battery through the cranking leads while underway. As far as what type and amperage charger to get, there are a ton of options to choose from. The amperage rating on a charger indicates the total amperage that can be delivered to all connected batteries. The higher the rating, the quicker you can charge more batteries, to a certain point. All batteries types have thresholds for cell charging rates, that if exceeded, will damage the battery. The good thing is the companies that make the chargers know this and won't allow the leads to deliver more than necessary. But they don't keep the consumers from buying more than they can use. If you are going to use the boat during the day and charge the batteries overnight to go out the next day, I would recommend a 12A or 15A prewired, waterproof charger. They are pretty much plug and play. The ones I use at work are a little bit more expensive but they are bulletproof. They are smart chargers which charge and condition all connected batteries. They even allow you to select the type of battery being charged to maximize the life of the battery. This is the one we use for the smaller boats:

https://www.promariner.com/en/44012

I hope this helps. Happy boating.

Don