How do I charge my 6 volt batteries ??

[tasdevil]

I bought two 6 volt golf cart batteries ( simple lead-acid connected in series) to power the trolling motor I use for dock manoeuvring.After three days the voltage was down so I connected to my charger - a Lewco Marine 1220. Nothing happened, electrolyte remained at 1.12 or lower.

I had the batteries replaced and checked the electrolyte before re-installing. At 1.225, the instructions said to recharge; so I did with a standard auto charger set to 2 amps. Thirty six hours later , the reading has'nt changed??

Are there any sailing Farradays out there who can tell me :
What's going on ?
What have I done wrong ?
What should I be doing?.....

 

[Don S/V ILLusion]

Either of two things is happening - one of the batteries has a bad cell ( should be obvious with your hydrometer) or the charger is bad (have you checked it's output voltage?).

 

[Rich Stidger]

You should know that a truly defective flooded lead acid battery right out of the box is very rare. I agree with Don above that you have a charging issue.

A 2 A battery charger will NOT recharge these batteries. 2A is a "float" rate that will maintain charge only. You need to use a charger that can output 20-30 A to perform a charge. The Lewco Marine 1220 looks like it should do the job nicely IF it is working properly.

You should verify with a voltmeter and an ammeter that the charger has a voltage of 13.8 to 14.4 volts when charging and that the charging current is at least 5% of the total capacity of the batteries. For standard golf cart batteries of 220 AH, this would be about 11 A.

Verifying the state of charge with a hydrometer is a good idea, but you need to use a quality calibrated hydrometer. The $6 ones with floating balls, indicators, or a float with colored bands won't cut it. Buy a good industrial quality hydrometer and it will last for your lifetime or until you drop it. I use and would recommend the hydrometers and thermometers made by the Francis L. Freas Glass Works. See the link below:

http://www.freasglass.com/

Be sure to correct the hydrometer readings for temperature.

A new battery that measures sg of 1.225 is about 75% charged and IMO that is about normal for a new battery delivered out of stock. You are correct that it needs to be charged before use.

A battery that reads sg of 1.12 is under 6% charged and is virtually dead. Flooded lead acid batteries do not like to be left discharged because they will sulfate and become un-usable. Keep them charged all the time. And for the best life, don't discharge the batteries more than 50%.

 

[Joseph Shirley]

You asked how you charge 6 volt batteries. Are you trying to charge them as 6 volt batteries with a charger set on 6 volts? If you have 2 6 volt batteries in series you have one 12 volt battery from the pos of one 6 volt to rthe neg of the other. It should be charged as a 12 volt battery. If you have been trying to charge a 12 volt battery with a 6 volt charger you are wasting your time. Note that everyone has been talking about 12 volt values.

Good Luck

Joe S

 

[Stu Jackson]

Assumptions are the mothers of f-ups, but I think we have to give him the benefit of the doubt that he understands that two 6V golf carts batteries are one 12V bank for his TROLLING MOTOR. I haven't seen any 6V trolling motors, have you? Sounds like the charger isn't putting out, too small or fried or one bank or cell is dead.

 

[tasdevil]

Thanx for the help - yours espeically Rich -I think I'm getting on the right track .I've exchanged the batteries so dead cells seem unlikely, which leaves the charger.It's a Lewco Marine which is a good unit and charges my two house batteries satisfactorilly . So what's left would be the charge rate.
I have been using the recommended #2 setting up till now but I would doubt that this puts out more than 5 amps. So is this the problem ? Should I charge my 6volt series combo separately from the house bank , and set it to maybe 15 or 20 amps ?

 

[Rich Stidger]

I am not familiar with the Lewco charger, but I would charge the two GC's in series SEPARATE from any other batteries and be sure that the charger is enabled to put out it's full charging current.

Flooded golf cart batteries can easily accept 20-30% of their capacity in amps. For your 220AH golf cart bank, that would be 44-66A. Your charger probably can't put out that much so you are completely safe to enable the charger for it's maximum. As the batteries charge, the charge current will taper off. As a rule of thumb, when the charging current drops to 2-3% of the bank capacity (4.4-6.6A in your case) the batteries are fully charged.

I routinely charge my 460AH golf cart bank at initial currents of up to 70-80A, and I have been told by Trojan (one deep cycle battery manufacturer) that they can accept twice that without any problems. The operative word here is initial. The batteries will naturally taper the charging current as they become charged, and the charger must allow this taper to occur.

One last item- Verify that the connections of the charger to the batteries are good. An initial high rate of charge current is a good indication of good connections.

 

[Stu Jackson]

Rich, good points but let's be careful with definitions:

taper - the reduced output of a CHARGER without controlled three stage charging

acceptance - ability of the BATTERY bank to absorb current from the charger