I have read the different comments on using Costco Batteries in my 2002 Gem. Does anyone have any recent results? I left my batteries plugged in for 3 months while I was away and they now will not hold a charge. Tried charging each one with a charger and still no luck. So I need to replace all 6 thanks
You can use the Group 27 batts which are cheaper, but they will not last as long nor have the same range. If you do not use it everyday for long commutes you may get away with using Group 27 or 31. My Gem gets light use and I use Group 31 Interstate industrial batts. My local dealer also supplies the local colleges & municipalities that use Gems with the same battery. They are not the same as a marine deep cell, which is what you will find at Costco in their cheaper deep cells. Interstate happens to have a warehouse store near me that sells to the public. They also test them for free with their fancy tester. I was able to get some “blemish” batts at my location for $40 each. They get them randomly so you have to ask about them.
So while the OEM batts are the best, they are costly. If you use your car heavily, they are probably worth the expense. They are gel and do not require monthly water checks.
The next choice would be “GC” or golf cart batteries. These are also the proper batteries and well suited for the job but not as cheap as marine deep cells. These are usually flooded wet cells and have required maintenance.
If you are trying to save a few bucks and do not use your car much, the Group 31/27 may work for you at the cost of less life & range. They also have required maintenance as they will be flooded wet cells.
What ever you buy, learn what is required of the battery so it will preform at it’s best and get you the longest life. This is very important as it seems that the Gem’s go can through a costly pack every 3 to 5 years.
[B]One last thing… the search function is your friend here. There are many, many threads here on what batteries to buy and why.[/B]
I decided to go with the Gem Gel Batteries.
Nice choice. Expensive but they should serve you well. I assume you have your charger set to the correct charging profile for the gel cells. If you treat them right you should be rolling strong for many years. 
I did not know I needed to match the charger to the battery type. I have a Zivan charger. How am I supposed to change the profile?
What type of batteries were in the GEM originally? This is important because the profiles are different. “F” is the setting for flooded batteries while “C” is the setting for gel batteries. There is a small selector switch on the top of the charger. It may be covered by a seal. Check this before going further. The flooded setting may overcharge gel batteries. Also, look for a small label on the charger saying “micro upgraded.” This indicates that important software updates have been completed.
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