Battery charger

[Jason F]

Hello,
My battery charger died and I'm buying a new one. I have 2 12v batteries in parallel. I need 20 amps and the old one had 2 positive 10 amp leads and one negative. (Xantrex TC 20+) Both positives were on one + terminal and the negative was on the the - terminal of the same battery. The new ones I'm seeing (ProSport 12 Gen 3 Heavy Duty Recreational Series On-Board Marine Battery Charger - 12 Amp - 2 Bank) are two 10 amp banks with 2 pos 2 neg cables. Can I hook both positives to the same terminal and both negatives to the negative same terminal or should I put one + and one - on each of the batteries? Or am I totally out in left field?
Thank you
Jason

 

[LeslieTroyer]

I like the Pro Mariner/ Sterling chargers. MaineSail has very competive pricing at marinehowto.com
Les

 

[Ron20324]

Use the positive of one battery, neg of the other.

 

[Jason F]

Thank you Les. I'll look at those. So with the ProMariner 63120 ProNauticP Series 1220P with 3 positive leads and one negative would I put all three of the positives on one + terminal?

 

[LeslieTroyer]

If you want to charge house and start batteries connect each positive battery to one of the chargers output. Then put a jumper from the terminal with the house battery to the third output on the charger. Don't forget to put 30 amp fuses at the battery end of the cables.

Les

 

[Stu Jackson]

RTFM

Wiring a new charger From Maine Sail:
https://marinehowto.com/installing-a-marine-battery-charger/
https://marinehowto.com/installing-a-marine-battery-charger/

and

https://forums.sailboatowners.com/index.php?threads/1-both-2-off-switches-thoughts-musings.137615/

If you have a combiner or ACR then you only need to go to the house bank. You didn't say.

 

[Jason F]

Will do Ron, thank you.

 

[Jason F]

Stu, I have a 1, 2 and both switch

 

[Jason F]

And I found the manuals on line.

 

[jssailem]

MaineSail has very competive pricing at marinehowto.com

 

[jssailem]

Jason,
A read of MaineSail's site will lead you to explore the 1/2/both switch. Stu and MaineSail have shared a wealth of info on this forum regarding the features and human hazards associated with this switch set up. As your now entering the world of marine electrical connections, I would encourage you to read the info and make informed decisions for your boat.

 

[Jason F]

Thank you for the info John, I'll go take a look

 

[Benny17441]

If you have the batteries connected to a 1,2,Both,Off switch it would be best to connect one set of leads to one battery (+ and-) and the other set to 2nd battery. That way it would not matter in what position would the switch be allowing both batteries to be charged when connected to shore power. The battery charger will divert most of the charging current to the battery that needs it the most but will charge both. A 20A charger may send 10A to each equally discharged battery or perhaps send 20A to a single discharged battery. If you just connect the leads to a single battery it would require for the battery switch to be set at both for the second battery to receive charge. If you use the alternating method of using a different single battery per outing to keep the 2nd in reserve then at the end of the day you may have a partially discharged battery and a fully charged one. Electricity flows like water and if you combine both batteries the charge from the full one will flow towards the discharged one. Not a big deal but I find it best to let the charger just deal with one discharged battery.

 

[Jason F]

I did some additional research and settled on the Pro Mariner 20 amp duel. It actually has a separate positive and negative for each battery. Way different than what I had before. I've been running it for the last few weeks and it works great. Thank you all for the input.

 

[Benny17441]

I did some additional research and settled on the Pro Mariner 20 amp duel. It actually has a separate positive and negative for each battery. Way different than what I had before. I've been running it for the last few weeks and it works great. Thank you all for the input.

Excellent choice, we have one and it has been our experience that it will charge batteries faster than our previous 30A unit. Having individual leads to each battery will insure charge to both as soon as you plug in to shorepower and flip the ac breaker.