Charging options for GEM

Having charger and battery issues with 2002 e825

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A bit more information would be helpful.

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No shift! This new format sent me elsewhere and sent the message becor I finished. I CANMKT SEE THE MESSAGE SCREEN WHEN MY KEYBOARD IS UP ON MY PHONE OR TABLET, so I’m typing blind. Will respond when I get bat k to my laptop and can see what I’m doingt

Back at laptop. Now I can see what I type.

Background on this topic and my status:

This is rather long, but…

Bought 2002 e825 back in October 2016 thinking it had fresh Odyssey batteries (installation date stamped 4/16) and that all was working fine. I was wrong.


Noticed charger was not charging to 100%, only 90% and voltage dropped to 80% or less if left overnight. Tried this several times before seeking help from this forum.

On advice from Old Houseboater (OH) I checked batteries as per OH instructions. One battery was toast, one weak, 4 okay. Called Odyssey and learned the manufacture date stamp location and then found my “fresh” batteries had varying dates from 2010 to 2012. Also learned the batteries in my GEM were CRANKING BATTERIES and NOT recommended by Odyssey for anything but CRANKING. Also learned that these $320 each batteries had warranty of only ONE YEAR… and then only for manufacturing defects, NOT PERFORMANCE!

LESSON 2: DON"T BUY ODYSSEY BATTERIES, too high priced with little warranty even if you buy the correct ones for the application.


LESSON 3: While folks on this forum are ready and willing to help, they often assume us newbies know more than we do, especially when it come to terminology and battery type/model designations. For example, “go to blank and get a blank brand and blank model number.” Several recommendations were for model numbers that didn’t exist or were the wrong ones for GEM application. One was actually a CRANKING battery.

LESSON 4: BE SURE YOU UNDERSTAND WHAT THE FORUM MEMBER IS TRYING TO SAY BEFORE ACTING ON ADVICE. Bad or misunderstood advice is bad. Good advice misunderstood is worse! Communication is a two way street.

Can’t afford new set of batteries, especially here in middle of winter in NC mountains, so I asked OH about replacing bad/weak Odyssey with comparable batteries just to run diagnostics as per service manual he provided. (THANKS, OH!). OH advised that would likely be okay but not to try to fully charge the old bad/weak battery and then run diagnostics… that would taint diagnostics.

Now to get to preliminary diagnostics and the CHARGING OPTIONS:


Charged each battery individually to full charge using regular car charger. Multimeter showing pack at 76.6v. Battery status on GEM gage showing 100%.

Left cutoff switch ON and check charge status with meter 15 hours later. Pack was down to 74.3. GEM gage showed 80%.

Recharged with car charger. Multimeter showing 76.6v, GEM gage showing 100%.

Left cutoff switch OFF and checked charge status 18 hours later. Pack was only down to 76.1v. GEM gage showing 90%



After finding I had a drain in the system and not wanting to go into full service manual diagnostic routine until I had correct batteries installed, I started to check status of charger. It’s a Zivan NG1 with the setting dial for different type batteries. Attaching multimeter to output terminals on top, I got a reading of 75.4v. with the charger not connected. Connecting the charger, the reading did not change. Fan came on, charger seemed to make some humming noise, but voltage began to slowing drop.

LESSON 5: CHARGER IS NOT CHARGING AND MAY ACTUALLY BE CAUSING DRAIN. I will check this when I get correct batteries… I want to get THAT variable stable before doing actual diagnosis.


Inadvertently, I left the multimeter connected to the +/- leads on top of charger and the CUT OFF SWITCH UNDER THE REAR SEAT TURNED ON and began charging each battery with car charger. I had previously had the cut off switch OFF as per OH instructions.

With the cut off switch ON and my car charger connected to one battery, the multimeter showed the voltage for the pack climb steadily from 74.5 to 77.6 over a period of several hours. Tried this several times with similar results to the “drain” test. Battery pack held voltage with switch off, drained with switch on. Each battery also tested at 12.6 to 12.8 volts. BUT THE POINT IS:


It’s not a fancy, high powered charger. Just a five year old Schumacher model SSC 1500a. Yet it charged to pack as indicated!!



With the Zivan not working, I cannot compare the results from it to that from the old Schumacher. The Schumacher took about ten hours to bring the pack from 74.5 to 77.6.

Any and all comments are welcome!! Sorry for length :slight_smile:

Are you saying that all batteries charged with your charger connected to only one?
No, that will not happen. It’s fine to charge 6 times to get the pack charged.
As far as leaving the switch “on”, makes no difference. Just good practice to turn it off when working on car.

I’m saying EXACTLY that. With switch off, only the battery with the charger connected to it will charge, rather quickly. With the switch ON all batteries charge. State of charge on my car charger will show the charge for the battery connected to the charger, usually in the 12.5 to 15.3 range depending on status before connecting charger. The multimeter connected to either to the output terminals of the Zivan charger OR connected to the breaker for positive and the negative into controller from the battery pack will show status of the pack, usually around 74.5 before turning on the car charger and up to 79.9 with car charger running. After disconnecting car charger, multimeter will gradually drop back to 76.3 and stabilize. It will stay at that level for a few hours if switch is cut off, gradually dropping about .5v over 15 or so hours. If switch is left on, the reading at multimeter will drop to 74.5 over same amount of time (the drain). I understand you say that will not happen. IT DOES! It charges to the same level as cutting cutoff switch off and charging each battery individually… AND IT DOES SO IN ABOUT THE SAME TIME AS IT TAKES TO CHARGE EACH INDIVIDUALLY. As far as switch on/off not making any difference, it does: switch off- one battery connected to Schumacher charges. Switch on- all batteries charge.

This is why I posed the question of CHARGING OPTIONS.

QUESTION: I have checked the output side of the Zivan charger with my multimeter. It shows the charge status when first connected but no increase when I plug in the Zivan. When I turn on the Schumacher attached to just one battery with cut off switch ON, the meter (attached to the output leads on the Zivan) shows an immediate but slow increase in the voltage until it reaches as high as 79.9 where it levels out. I assume the lack of increase when the Zivan is running to mean the Zivan is not charging. Is this right? The Zivan, if working, should show an increase in voltage just as the Schumacher does. You say that the charging with the car charger connected to one battery with the cut off switch ON cannot happen. Have you tried it??

I’m a newbie to electric cars kinda wandering in the dark here, but what I have observed is accurate and I hope accurately communicated and understood.

I am having same experience. Anyone explain why/how

Some have said it’s not possible. It is on mine.

That would be me!
Good luck.

“Good luck” seems to imply you don’t believe what I’m experiencing. A review of my detailed posts on what I’ve experienced is covered above. Perhaps Old Houseboater can comment. I’m experiencing what some have said is impossible. The question, WHY?

How many miles are you getting when you only charging one battery?

A reading of the previous posts, above, will provide a background for understanding the situation. I have mess on my hands and am trying to determine where the problems are. The charging issue came out of left field and surprised me. Thus my post. I have described the situation accurately and am hoping someone can help me understand why/how the car charger is charging the entire pack. As I have described, the car charger is charging the pack even with the Zivan charge not connected to a.c. power.

It is not charging the pack. That’s why I asked how many miles.
Just because you increase the pack voltage does not mean it’s charging.
You asked why not. Why is the sky blue? It just doesn’t work that way.
Yes, I have charged a single battery in a series string. No it does not charge the others.
I don’t doubt your volt readings. Only your conclusion.

Not arguing here, just trying to understand. If the packs charge goes from 74.5 to 79.9 and stays there, what is that called if not charging? If the charge from individual batteries goes up in the process, what Is happening if not charging. How do you measure “charging” if not by reading voltage ? What am I missing?

Voltage can be an indication of charge in a properly working system.
It is not an absolute indication of the power available from the battery.
If your batteries are balanced and in good condition a reading of 84 volts will be a good indication of full charge.
Be assured that you can not input 12 volts and output 72 volts for long, without an electronic method of conversion.
It’s highly unlikely that anything in the stock Gem is capable of this. IMHO

I tried this method. I left main disconnect on, I charged one battery at 20 amps for 30 mins. It did nothing on the other batteries voltage (in fact they actually dropped a bit from the built in charger’s run earlier). I have a 2002, I believe my charger is failing or is not setup for flooded. What would be a good replacement for flooded batteries? Charging up each battery is too much work. I’m doing it right now but I wouldn’t want to do this too many times.

Right now the built in will charge it up but the charge is dropping off really quick. I replaced one bad battery but it was only about a year old. I think the charger is not topping them off which ruined one battery. It is the Niven NG1 and there is no dial inside to adjust.

If you’re checking charge at the main disconnect that would be the total charge, but I would think you would need to check the charge at each battery to see if it’s making a difference. It didn’t for me. You’re probably just charging one battery and that does effect the overall charge but you don’t have consistent voltage throughout the series. I turned the key on when I had one battery charged up with external charger and before it read 85 percent, it then read 95 percent. But it did nothing to the other 5 batteries. I think Inwo is correct, have to charge individually.

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I agree with David: pack voltage can be mis leading. Pack voltage combined with cold cranking Amps ( a test that places a load in the battery) and tells you it’s true strength.

Any chance you guys are millenniums?

Think of voltage as “Facebook friends"
Think of cold cranking amps as " real friends”

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What you are saying makes perfect sense. But what I reported in the details above happened and happened repeatedly. At least half a dozen cycles while I tried to make sense of of it. The voltage increased on the pack and on individual batteries when the external regular old automotive charger was hooked up to one battery but the cutoff switch under the rear seat was on ON. Always assumed voltage was a measure of the state of charge. A resistance tester showed all six batteries now in car were “ok” when load tested after full charge… or whatever you call it when the pack is showing 79.9v. My initial thought was that the Zivan, when plugged in with the old Schumacher also connected to one battery and the cut off switch ON was somehow working WITH the Schumacher. However, when I got the same results with the Zivan unplugged… I assumed the Zivan was adding nothing to the system. If I take a multimeter reading at the +/- terminals on top of the Zivan, I get a reading of 75v, plus or minus a half volt, regardless of whether the Zivan is plugged in or not. If I connect the Schumacher to one battery and leave the cut off switch to ON, The reading at the out put of the Zivan does not change. However, if I take the reading with the negative probe of the meter at the negative output terminal of the Zivan and the positive probe on the positive post at the the breaker switch, I get an immediate reading of 74.5v to 75.5v that begins to climb and has reached as high as 81v. The pack holds this reading. Just reporting observations and seeking explanations for how this is occurring.

Since voltage is apparently an unreliable way to test the charge state of batteries, how would you recommend I measure the output of the Zivan and the actual charge state of the batteries. I cannot road test so I cannot provide you with any “miles driven” information.

Thanks for your help and I hope you understand I am not intentionally trying to be difficult. I’m pretty good with fixing up old motorcycles and cars and did okay refurbishing an old EZGO golf cart. This GEM has not been a GEM :frowning:

I know I need different batteries. Current ones are Odyssey PC1700 and I now know they are cranking batteries, not deep cycle cart batteries. I also have not run the complete diagnostics as per manual.

Run the pack down by leaving the lights on or some other load.
Check pack voltage at the B- and B+ not at some unknown place.
When down to 72 volts check each battery voltage while still under load. Then charge each one to 14 volts or more.