Which Onboard Charger?

**gabowman** · 02-04-2010, 08:31 AM

Every time I go fishing and get home, I immediately hook up my charger to the two batteries that runs my trolling motor...which I always leave hooked up in parallel. The motor always keeps the cranking battery charged so I never need to charge it but if I ever do, charging with my portable wont be a problem.

My question is....I always charge the 2 batteries in parallel set on 2 amps with my portable charger and they are fully charged the next morning. So....if I decided to add an onboard charger how powerful of a charger would you guys recommend? Another question, with my current setup, with a lead hooked to the cranking battery and another lead hooked to the trolling batteries what happens when the cranking batt gets a full charge but more charging is still needed on the trolling batteries? Does all onboard chargers automatically switch to just maintaining the batteries (trickle charging) so you never need to unhook the charger before your next fishing trip? Thx.

**TnT** · 02-04-2010, 08:44 AM

Most on board chargers have a "Transfer on Demand" feature. Mine is only a 2 bank with 5 amps on each bank. What this does is once 1 battery is fully charged, the 5 amps that was being delivered to that battery is transferred to the other battery giving it a 10 charge until fully charged. It distributes 100% of its available charging amps to any one bank or combination of all battery banks. All unused charging amps are Transferred-on-Demand to batteries on board requiring additional amps. Some chargers do not have this feature and they have a fixed amp limit per bank...Hope this helps.

**CatFan** · 02-04-2010, 08:56 AM

Get at least 5A per bank, preferably 10A. The more quickly you get the battery charged (up to a point) the longer the battery will last. Most onboard chargers are actually 3 individual chargers that don't care what the other banks are doing. Some now have the ability to charge whatever battery needs it.

Onboards do not operate as trickle chargers when the battery is charged, they are float-mode chargers. Float-mode maintains a low charhing voltage to reduce gassing while monitoring the battery current draw, while trickle chargers are typically around 2A fixed current which can boil a battery dry.

A 2A charger will struggle to charge two batteries in parallel. As they age, losses during charging increase until 1A per battery won't do much but make the battery warm. You should charge at 10A if that's available, or even 15A if your charger can do it. Don't trust a charger that says automatic or manual. These things will destroy more batteries than anything else. Use a charger that says "Smart Charger" or "3 or 4 Stage Charger" to get full charges and longer battery life.

**Don G** · 02-04-2010, 09:27 AM

I have had good luck with these chargers & they are made in the USA

Pro Charging Systems

**Barnacle Bill** · 02-04-2010, 09:38 AM

Catfan is right on. When you get home from fishing, plug it in and forget it until time to go again.

**rnvinc** · 02-04-2010, 10:19 AM

I have the BPS XPS 5-5 chargers...I think they are actually made by Pro-Mariner...for BPS...

**TnT** · 02-04-2010, 10:36 AM

Originally Posted by rnvinc

I have the BPS XPS 5-5 chargers...I think they are actually made by Pro-Mariner...for BPS...

How warm does your charger get when it is actually charging? I just put that same charger in my boat yesterday.

**Barnacle Bill** · 02-04-2010, 11:01 AM

Originally Posted by TnT

How warm does your charger get when it is actually charging? I just put that same charger in my boat yesterday.

I use the 5-5-5 and it is normal for them to get pretty warm.

**rnvinc** · 02-04-2010, 06:26 PM

No so warm that you can't touch it..but pretty warm....

**WE16** · 02-04-2010, 08:29 PM

Originally Posted by TnT

How warm does your charger get when it is actually charging? I just put that same charger in my boat yesterday.

I have the XPS 4/4 and it gets uncomfortably hot.
I never have any problem with the charger not being able to charge the trolling motor battery back up overnight. Since the start battery is usually close to full charge, the trolling motor battery should be getting 8 amps of charge. I get back from fishing, plug the charger in and leave it. Ready to go any time.

After many years if working around batteries and chargers, I like to keep the charging amps as low as possible but still charge overnight. I am not an engineer, just the guy who for the last 30 years had to clean up the mess after batteries got hot, melded down, and exploded from being charged to fast. Heat from weather or charging is a battery worst enemy

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