Best way to charge batteries

[NBE]

Just recently replaced my trolling motor (went from 24V to 12V) and now have two batteries (deep cycle for trolling motor and regular for cranking an 80's model 50hp Merc) separated by a West Marine battery combiner (50 amp) as recommended in this forum. Although the combiner seems to be working fine as far as maintaining the charge of the batteries while out on the water, I still want to hook up my charger (external Sears charger with one positive and one negative) when I get back to make sure they are fully charged. My battery charger has the normal switch for 12V-10A and 12V-2A charging and a selector switch for for battery type, either deep cycle or all others. I plan on using the 2 amp rate mostly but was wondering which battery type should I select. For instance, if I hook the charger up to the trolling motor battery I normally would use the deep cycle setting. Now that I have the combiner inline, I am thinking that while charging the trolling motor battery (at home) the combiner is also letting the starting battery charge. If that is the case, would having the charger on deep cycle setting hurt the starting battery? Which battery should I hook up to with this system (if the combiner does let both charge at the same time) and what battery type setting should I go with on the charger? What is the best way to make sure both batteries are maintained as well as possible other than what I am doing? Thanks in advance for your help!

 

[Drowned Rat]

Re: Best way to charge batteries

Hi Brad E. I would not charge two different types of batteries at the same time. It will work, but it's not good on the batts. They will charge unevenly, or it will shut down before one of the batteries is fully charged. Also, be carefull charging 2 batts. at once with that Sears charger especially on the 10A mode. The charger can overheat and/or the automatic feature can fail and overcharge your batteries. I'm not sure which model charger you have, but most of them are only designed to charge one battery at a time. It should tell you so in the manual. Hope this helps.

 

[NBE]

Re: Best way to charge batteries

This is my first time charging after installing the battery combiner. I used to disconnect all of the battery cables when I got back from a trip but had kind of gotten out of that habit the last couple of trips. I think the simplest thing to do is just disconnect all of the cables and charge the batteries one at a time when needed. I wasn't really sure what the combiner was doing when I started to charge at home but thought that it was probably letting both charge at the same time. Wasn't sure if it only charges one at a time with the weakest first, both at the same time, or what. I guess I could check this with a voltmeter but as I said above I will probably just disconnect and do one at a time. As far as the charger, I haven't used and don't plan to ever use the 10A rate on my boat batteries if I can help it. So far the charger has worked fine since I bought it a few years ago but I do keep a close eye on it when it is being used. The battery combiner seems to be all that it is advertised to be as my trolling motor acted like it could run for days on my last trip. When I hooked up the charger initially after this last trip it indicated the battery needed minimal charging. At this point I definitely would recommend the combiner to anyone interested in one. Thanks!

 

[Boatist]

Re: Best way to charge batteries

Brad E<br />I would not use any setting other than the 10 amp unless your charging a motor cycle or lawn mower battery. Car and motor home alternators nearly all over 100 amps now and they charge deep cycle batteries just fine. Dont charge the battery when it is 110 degrees in the shade and the boat is out in the sun. As long as your charger is automatic when battery reaches full charge the charger will taper to near zero anyway. The danger of useing the 2 amp setting is it takes so long to fully charge your battery you may never reach full charge. A run down group 27 will take almost 24 hour to recharge at 10 amps. At 2 amps it will takes days. Better to get it charged up quickly.<br /><br />I do not belive your battery combiner will connect the batteries if you connect to your house battery. To be sure hook up the charger to your house battery and then go and put a meter on your starting battery. If it over 12.8 volts then charger is charging both. Charge voltage should be in the 13.8 to 14.8 range.<br /><br />Most important is to charge ASAP after discharge and to fully charge. Charge at least once a month weather your use battery or not. <br /><br />I use a 10 amp automatic charger and a 65 amp alternator to charge both my batteries thru a battery isolator and have never had a battery not last 6 years.<br /><br /> http://www.uuhome.de/william.darden/carfaq.htm

 

[Cricket Too]

Re: Best way to charge batteries

I agree with Boatist, there is no reason to not use the 10 amp setting. 10 amps to a car or marine battery is nothing, as was mentioned, your car is charging it's battery between 60 and 100 amps from the alternator. Proffessional battery chargers don't even go as low as 10 amps, I think their lowest setting is 30 or 35 amps. Using the 2 amp is a waste of time on a 12 Volt car or marine battery.

 

[Cricket Too]

Re: Best way to charge batteries

Hey guys, just realized my charger has a 50 amp "start" setting. Would I be able to use this for charging my batt. since an engine will charge it with this amperage or higher?

 

[Drowned Rat]

Re: Best way to charge batteries

NO! Do not use the 50A start feature to charge your batteries. That setting is to be used for only 20 to 30 seconds at a time. Anything more and it will overheat, and trip the breaker if it has one. Otherwise it will just catch on fire or fry your batteries or both.

 

[NBE]

Re: Best way to charge batteries

Thanks for the feedback! Maybe it was something I had retained from my childhood (meaning maybe poorer quality batteries or something back then perhaps?) but I had heard from somewhere long ago that a slow trickle charge was better if the battery does not need much charging. Maybe I heard to use it when just maintaining the charge and got confused......don't know. The battery combiner did an excellent job of keeping both batteries charged and I was just wanting to "top them off", if needed, to make sure they are maintained in good order. Regardless, out with the old and in with the new. What you all have said makes perfect sense to me and I certainly have no problems using the 10A setting from now on. That is exactly why I wrote in......to learn. Thanks for your help and take some time to take a kid fishing with you! Pass the knowledge!

 

[Boatist]

Re: Best way to charge batteries

Brad E<br />Only time I would use the 50 amp starter circuit would be in a life threating emergency. I seen the high amp starter circuits blow output diodes in the alternator and other electronic equipment on your car.<br />Cheap trickle charger are usually not regulated or automatic. I think your 2 amp is. It is ok to use it but your 10 amp automatic should taper to zero at the same voltage and just take less time.