Golf Cart Battery Charging

[thomm225]

Do any of you disconnect from charging after your batteries are up to around say 13.5 volts? ( I have two 220ah 6 volt in series)

I read something saying you shouldn't charge them continuously due to heat buildup.

I disconnected from my 85 watts of solar this am as I'm not a liveaboard and use the boat mainly on the weekends.

My plan would be to resumes charging a day or so before I set sail for a few days.

I'll probably set the float to 13.5 volt charging with about 135 watts after I get things set

[donradcliffe]

It all depends on your solar controller and its settings. If you set the float to 13.4v (and verify that is what you get if it is a cheap Chinese controller), your batteries will be happier if you don't disconnect the solar. The controller will throttle back to current to what is actually used and there will be negligible heat generation. If you float at over 13.4, you will have to rewater your batteries more often..

[Dsanduril]

With standard LA batteries I wouldn't disconnect until after the batteries are completely charged, and that generally takes getting to 14.2-14.4V and a low tail current. At that point, if you want to disconnect then fine, although setting a low float voltage is how I run. You never know when plans might get interrupted and the boat sits longer than you expect and self-discharge rears its ugly head.

If you disconnect at 13.5 before you reach up into the absorption phase you run the risk of leaving lead sulfate on the positive plates, and the longer the sulfate sits there the larger the crystals grow, and the harder they become to get rid of, decreasing battery capacity.

[Nord Sal]

I'm guessing what you read was probably in reference to simple, old battery chargers that only had one setting and would cook your batteries if not removed after reaching a full state of charge.

Modern chargers and solar charge controllers will cycle your batteries through bulk and absorption phases, up at around 14.4± volts before dropping voltage to a float level around 13.5± volts after amperage at the absorption phase drops to a specified value (tail current.) You may be able to program your charge controller to match the specific recommendations of your battery manufacture, these values can differ somewhat from manufacture to manufacture even for the same battery chemistry.

You should be good if your charge controller goes thru all these charging phases rather than one that just maintains a high voltage. Your solar-powered charger essentially disconnects every night.

[thomm225]

Thanks all. I’ll go ahead and charge them up to 14.2 or so then set float to 13.4 volts. My pwm controllers don’t have an absorption phase so I may do that with a straight panel direct. My Victron has failed

[BMD21]

I use 2 ea Trojan golph cart batteries and a 3 stage battery charger. The charger will charge them to ~13.4 volts and then if they're not being used, let them float without a charge.



They float at 12.4 volts, as did their predecessors. My backup battery is a normal deep cycle 12 v and they float at 12.6-12.8. Any comments on either float voltage?


Boris

[Stu Jackson]

Originally Posted by thomm225

Thanks all. I’ll go ahead and charge them up to 14.2 or so then set float to 13.4 volts. My pwm controllers don’t have an absorption phase so I may do that with a straight panel direct. My Victron has failed

Please don't do that. First, 14.2 IS absorption voltage, regardless of what it's called. Second, straight panel direct will most likely be a much higher voltage than any batteries would "like", i.e., way above 14.2.

[Jim Cate]

fwif, Trojan says to use 14.8 V as absorbtion voltage for a full charge.

Jim

[thomm225]

Originally Posted by Stu Jackson

Please don't do that. First, 14.2 IS absorption voltage, regardless of what it's called. Second, straight panel direct will most likely be a much higher voltage than any batteries would "like", i.e., way above 14.2.

No, it drops to the voltage of the battery. You just have to monitor it and not leave it unattended. I usually have a 20 watt panel hooked to the batteries directly when I'm actually out cruising. ( but my not have to now with these 220 ah golf cart batteries)

I've done it quite a bit over the years, but as it turns out I was able to set my old PWM controller float to 14.3 volts and watched it climb to about that and stay for a while.

But since I did my 3 mile run (jog, walk, crawl depending), pushups, and pullups today I was beat and didn't stay long.

Before I left I set the Float to 13.4 Volts and put the smaller panel into the lazarette locker leaving just my 65 watt panel hooked up.

The 65 watt panel is the one on my Aft locker you see in all my videos and many pictures. That thing has been used and abused over many years maybe 8 or 9 years.

Cost was $76.00. I soldered 14 gauge wires to it and that has been my main panel since around 2012. I also have two 20 watt panels and a 50 watt Renogy that will get hooked up to the controller I just received tonight.

These pwm controllers are cheap but tough.

https://www.amazon.com/dp/B08L8TBCK6...roduct_details

[thomm225]

Originally Posted by BMD21

I use 2 ea Trojan golph cart batteries and a 3 stage battery charger. The charger will charge them to ~13.4 volts and then if they're not being used, let them float without a charge.



They float at 12.4 volts, as did their predecessors. My backup battery is a normal deep cycle 12 v and they float at 12.6-12.8. Any comments on either float voltage?


Boris

When I start to cruise long distance, I'll go with a 12 volt backup as you have.

[thomm225]

Originally Posted by Jim Cate

fwif, Trojan says to use 14.8 V as absorbtion voltage for a full charge.

Jim

I think my Victron used to go up to 14.6 maybe during the absorption phase (default setting) but not positive since I can't find the chart with a quick search.

I think I destroyed my Victron 75/15 by all the switching and swapping of panels that I do and with it's technology I think it got confused etc and that possibly didn't help things or I simply hit the wrong wire to the wrong voltage by accident.

The fuse was blown and it has never been right since ......but maybe I'll get another one with the bluetooth connect next year.

[Bowdrie]

You might be able to contact the manufacturer of your batts and find out the rate of self-discharge.
Once batts are fully charged they only need enough input voltage to overcome the self-discharge rate, and their internal cell resistance.
For the "typical" flooded batt, that's ~2.17>2.2 volts per cell.
Adjustments should be made for temp,, in cold weather you can float a bit higher,, their are charts for that.
The lower you can float and still maintain a full charge the better.
Each 1/10 of a volt above optimum float doubles the currant,, and that causes grid corrosion on the positive plates, which is harder on batt life than sulfating of the negative plates from undercharging.
US Battery has a good website, with lots of info about charging and floating.

[Celestialsailor]

Get a MPPT charge controller. Your batteries will be much happier.

[thomm225]

So the method I used on the batteries I had that lasted the longest was to charged them to 14.4 volts then unplug for days at a time or until I was about to use them again.

The controller had no float except 14.4 volts which is where it stopped and stayed so I would unplug from the controller.

I'm still seeing best practice on golf cart batteries is to unplug from the charger (this on multiple sites) when not in use so I may still do that as I'm not a liveaboard or continuous cruiser.

The wires from my controller to the batteries have those large battery style alligator clips so there is no problem to unplug.

[roverhi]

If you suspect the charge controller, best to unplug. Had a wonky charger and had to constantly add water to the batteries. Eventually fried the batteries. Got a new batteries and MPPT controller and no problems with leaving the batteries on the solar charge. If you don't have a controller, better to disconnect the panel as it will quickly fry the batteries if the panel has too much wattage. Without a controller, the solar panel has to be sized to the battery capacity to keep from overcharging.