How to charge 6 volt golf cart batteries with 12 volt charger

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Join Date: Oct 2016

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6v Golf Cart Battery setup, Charging / Maintenance Q's

Ok. I'm going to purchase my two Sams Club Duracel 6V (GC2) this week. I'm also buying Victron SmartShunt to monitor my battery health. The only thing left is proper care and feeding of the system while camping and when in storage.

I read this thread battery charger recommendation needed. It looks like I can leave the batteries in the 12V setup and charge them like a single 12v battery. There might be a chance for the two 6V batteries to get out of voltage balance, but it doesn't seem to be a big worry.

So, while camping....

I can't find details on my 2017 Grey Wolf 26DBH to understand if the inverter will work well to charge the system with a generator running for 3hrs. Or if I should use a stand alone charger connected to the generator.

In storage....

I'll pull the batteries and bring them home with me, so I can keep them under constant maintenance charge. Again, they will be setup on a 12V config to be able to use my 12V BatteryMinder.

My BatteryMinder is labeled as Battery Charger, Battery Maintainer. I don't know if this would be a charging option when camping. Not sure it by 'Battery Charger' do they mean "if you wait long enough, it will charge a 50% battery".

FYI, my generator max is 900W.

Looking for advice on how I'll charge/maintain and if the products I'm using are the correct and work good enough. Don't need 'perfect', 'Best', or 'Top of the line'. Looking for Good Enough at the moment.

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connect the 6 volt batteries in series and then consider them as a single 12 volt battery. if there were minor voltage differences between the two batteries i do not think it would be significant as the voltages from the two batteries get added together and are presented as on 12 volt voltage. nothing is going to know that the individual battery voltage differ a bit.

there is always a lot of talk about using battery minders, etc. i have no experience with them. but i do know that if you remove all loads from the batteries while in storage (ie take one of the cables off the battery) they will keep their charge for many months. if just seems to be a hassle to me to be removing the batteries and connecting those battery maintainers. make sure you have a fully charged battery before you go into storage. take you generator over, reconnect the batteries, plug the shore power cord into the generator, and run it for a couple of hours. let the onboard converter do the recharging. you'll accomplish two things. recharge the batteries and exercise the generator. others my have other ideas / suggestions. listen to all of them and then pick the strategy that you feel comfortable with.

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Quote:

Originally Posted by AtlCamper

There might be a chance for the two 6V batteries to get out of voltage balance, but it doesn't seem to be a big worry.

Cell balance with a Lead Acid battery is not as troublesome as it can be with Lithium batteries.

The cells in series (you have six of them with two 6 v batteries in series) in lead acid batteries continue to pass current when they reach a full state of charge which allows those cells that haven't reached 100% SOC yet to keep charging.

In a Lithium battery, when one or more cells in the series connection reach 100% SOC, ALL flow of current stops and those cells that are less than 100% SOC get no more charge. To solve this a BMS provides cell balancing in the most commonly used batteries in the RV world. It does this by continuing to charge the low cells while slowing or stopping charge to the cells that have higher SOC. This is a somewhat simplified description but lets just say that the issue is handled by a designed in device. No operator input required.

Your converter will only see ONE big 12 volt battery if you have two 6 volt batteries in series and many modern converters incorporate an Equalization mode which provides a mild overcharge condition to help bring the low cells up to full.

Simple rule:

Two batteries in series = voltage becomes the sum of the individual battery voltage but the capacity (Ah) remains the same.

Two batteries in parallel = Same voltage as the individual batteries (which must be the same) and the capacity doubles.

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I have/use battery Tenders since 1983 with wet or AGM batterys and they last for years. The batterys and the Tenders.

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Re:- 6v Golf Cart Battery setup, Charging

I have also heard that charging directly from a portable Generator with 12 volt charging capabilities (My Honda 2200i has 12 volt direct connection)is better than either a stand-alone 120 volt AC charger plugged into a Generator or going thru the RV converter while connected to the Generator for getting charge back into a discharged Battery.

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Quote:

Originally Posted by Sparkyone

I have also heard that charging directly from a portable Generator with 12 volt charging capabilities (My Honda 2200i has 12 volt direct connection)is better than either a stand-alone 120 volt AC charger plugged into a Generator or going thru the RV converter while connected to the Generator for getting charge back into a discharged Battery.

The so called "charging port" on generators puts out less than 10 amps on almost all of them.

Better off to just plug RV into generator and let converter charge.

Rather than buying a separate charger just upgrade the wire running from converter to battery(s) to a larger gauge so it can carry the output of the converter without a large voltage drop.

Factory wire is most likely a #8 awg and the best move is to upgrade to the largest gauge wire that will fit in the lug at the converter.

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I guess I'll be looking at the wiring for the converter this weekend. I mentioned over in another thread that the SmartShunt is out of stock everywhere right now. Companies are getting shipments, just not large numbers and frequency is unknown. I have pre-ordered one and will be waiting 10 days to see if they get SmartShunt in. If they don't, I'll have to look at an alternative.

I can get the Victron 710 and add on a bluetooth board for $155. I'm trying to avoid having a display since that will mean installation will take longer trying to get the wires ran to the rest of my controls (water pump, hot water heater, slideout and awning controls, etc).

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Quote:

Originally Posted by TitanMike

Simple rule:

Two batteries in series = voltage becomes the sum of the individual battery voltage but the capacity (Ah) remains the same.

Since FLA batteries should not be discharged below 50%, do 2 6V 215AH GC2s (Sam's Club Duracells) provide 215AH of usable capacity? Or only 107AH?

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Quote:

Originally Posted by chriscowles

Since FLA batteries should not be discharged below 50%, do 2 6V 215AH GC2s (Sam's Club Duracells) provide 215AH of usable capacity? Or only 107AH?

I like to think of it this way. You can double to voltage or double the Ah, not both. Using 6v batteries, you need to double the voltage so it's seem like a 12v battery to the camper. So your Ah stays the same, 215. Of which 107Ah is usable without damaging the battery.

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Quote:

Originally Posted by AtlCamper

I like to think of it this way. You can double to voltage or double the Ah, not both. Using 6v batteries, you need to double the voltage so it's seem like a 12v battery to the camper. So your Ah stays the same, 215. Of which 107Ah is usable without damaging the battery.

Thanks for the clarification.

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Quote:

Originally Posted by AtlCamper

I like to think of it this way. You can double to voltage or double the Ah, not both. Using 6v batteries, you need to double the voltage so it's seem like a 12v battery to the camper. So your Ah stays the same, 215. Of which 107Ah is usable without damaging the battery.

My two 6v 225ah golf cart batteries will deliver 12v 225ah/2 useable ah = 112ah. Two deep cycle 12v 90ah batteries will deliver 12v 180ah/2 = 90ah useable, if they are true deep cycle batteries, like Trojan. Otherwise they will Discharge faster, I don�t know that calculation.

Anybody? TitanMike?

SamTummo

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Quote:

Originally Posted by samTummo

My two 6v 225ah golf cart batteries will deliver 12v 225ah/2 useable ah = 112ah. Two deep cycle 12v 90ah batteries will deliver 12v 180ah/2 = 90ah useable, if they are true deep cycle batteries, like Trojan. Otherwise they will Discharge faster, I don�t know that calculation.

Anybody? TitanMike?

SamTummo

How do you calculate 112ah of use? Furnace uses xxah for 8 hours, how long will that last?

SamTummo

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If the converter is a factory original, while your replacing the wiring you might want to consider upgrading the converter itself. I put a Progressive Dynamics 55 amp unit in my trailer and it does an excellent job of charging and maintaining the battery. Higher end converters like that will automatically apply a boost, normal or bulk charge as needed plus a scheduled equalization charge. This will charge your batteries faster than the typical original equipment converter and prevent the possibility of overcharging and boiling away the electrolyte.
Lots of threads about this here, worth a perusal.

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Quote:

Originally Posted by samTummo

How do you calculate 112ah of use? Furnace uses xxah for 8 hours, how long will that last?

SamTummo

Example:
Furnace draws 6 amps while running. Runs for 30 mins per hour.
6 (amps) x 1/2 (hours) = 3 ah x 8 (hours) = 24 ah
That would be a little over 1/5 of your 112 ah battery capacity.

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Thank you. Makes sense.
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You're Welcome !

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2007 Surveyor SV230 - 200 Watts Solar/MPPT Controller - 230 AH Battery Bank (Two-GC2) - 600 watt PSW Inverter - (2) 2000 watt Inverter Generators - LED Lighting
2009 F150 - 5.4 Litre with Tow Package

Boon Docking 99% of the time.