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CCA Battery Trouble Electric Scooter

I posted this on an EV Forum but haven’t had any response yet:

I have an eGo sit down electric scooter(,not a wheelchair thing, but like a simplified Vespa/bicycle cross). I keep having one of the two batteries(2-- 12 volt, 34ah, gell type, hooked together for 24 volts) failing. The dealer and the factory can figure it out, though they seem sincere in trying. They have replaced under warranty, a battery, twice.

One battery remains good: 12 volts, 366 CCA. The first failure was about 2 months after I got the bike, and the bad battery registered 12 volts, 188 CCa. The replacement lasted a week, and tested 12 volts, 235 CCA. The one old battery remained the same, 366 CCA.

What causes this drop in CCA’s, generally speaking, and what could be going wrong? I try to follow the directions and keep them charged up. Any ideas?

I am almost sure they are good when they get to me, as I have the right amount of power and range when new, until one begins to fail.

I meant to say, “the dealer can’t figure it out,” in line 4.

I also meant for this to be under “general discussion,”, so if anyone knows how to move it there, thanks.

I wonder if the problem is in the battery that you think is good and you aren’t replacing. If the internal resistance is lower than the other battery, it will receive full charge and the other battery will be discharged. Just a guess.

Have you tried moving the 366 CCA old battery to the trouble postion and putting the newer batter in the other battery position? When the combined 24 volt DC batteries are put under load, does the newer battery show a lower voltage than the 336 CCA battery? When the batteries are under charge, what is the voltage across each at the start and end of the charge cycle? Let us know the answers.

If I were troubleshooting these batteries, I would be measuring the Ah capacity of each battery at 20 amperes steady draw to an end point of 6-9 volts DC. It does take time (1-2 hours) to discharge the batteries at that rate but then you have an idea of what the battery is doing in application conditions. CCA measurement is for cranking over an engine. It says nothing about how long the battery can maintain that current.

Hope to be able to help.

That would be my bet too.

Like the others stated, I recommend you replace both batteries. There may be a bad cell in the battery that hasn’t been replaced. Then monitor the voltage across each battery as they charge up. The voltage should be close to the same on both batteries as they charge up.

The problem is the two batteries in series. There is no provision to balance the charge between the batteries. No two batteries have identical capacity. One battery always fills before the other and since the series connection forces both to have the same charge current. One battery gets chronic overcharge and the other undercharge. The problem is worsened if two new batteries are not fully charged separately before placing them in series.

One solution is to use a device called “Powerchek” which transfers current from one battery to the other to keep their voltage the same.

The other solution, which I use on my eGo, is two 12V chargers to charge each battery independently. I added a connector to gain access to the connection between the two batteries. So I have a 3 pin connector for two external 12V chargers.

I can still use the built in 24V charger if I need to charge away from home.
My current batteries are 5 years old and running strong.

I and others have talked to eGo about this, but they don’t want to change their design.

p.s.: I own one of the first 10 eGo’s made.

You’re looking at the wrong battery spec for your application. CCA’s are the amps available at below freezing. Unless you’re starting the electric scooter in a snowbank at -30 degrees, the CCA’s are meaningless.

What you want to look for in a battery for your application is the highest Reserve Capacity. This is the spec that dictates how long a battery will keep the electricals running in a vehicle in the event the charging system should fail. This is reflected in minutes on a battery. So a battery that has a reserve capacity of 120 will operate for two hours until it’s depleted and the volts drop below 12.5.

Look for a battery that has the highest reserve capacity. Not one with the highest CCA’s.


CCA is not meaningless. It does refer to the temperature corrected AMPABILITY . This is the same amp ability at normal temp with a offset based on chemical activity. Reserve capacity is not such a great number since it does not refer to the ability of the battery cell plates to handle amperage when the chemistry is slow due to temp(ie worst case scenario).
Reserve is kinda pointless since it refers not to drain rate(amps per second) which can damage low ampacity batteries by overheating the plates and causing them to warp and short. Which is why cca is a worst case scenario. Sorry but electrons dont lie. There are plenty of long time batteries out there that cannot do short or medium term high amps without internal damage. I deal with these batteries for computer server backup power supplies and reserve cap is useless if they cannot put out enough amps to keep the power inverter running the server shuts down due to lack of amps(a bad thing in my buisness).


Have they replaced the current controller? A bad one can cook the battery. The weakest battery fails first due to over heating(usually a manufacturing problem). The scooter motors may have a problem but the first place to look is the current control. This limits the power to the motors to keep them from burning out but a little too much current is more likely to cook the battery first. The motors are pretty durable.

If you read very carefully they limit the amp rate in this test. This limit is not really the design limit of the overall system for this scooter.
It is also not really a maximum rate test. Motors are different from lights they place hard inductive loads that by design often exceed the spec up to 3 times the rated limit. This is what kills the battery and why plates under triple design loads fail reserve test but pass on cca.

To circuitsmith:
Thanks for the information. I have two new batteries coming in I ordered. They are from a different company than eGo but the same specs. I want to use your advice and charge them separately each time I charge them, for months if need be, and see if that works. I have a good auto shut off 12 volt car charger I will use.
My question to you is: I know to unhook the white to white connector, which will separate the batteries into single 12 volt. I want to leave them in the scooter body. The question is, do I also have to unhook the connectors going to the charger and controller, or only the white to white and charge each separately that way.
Many thanks.

CCA is meaningless in a deep cycle application. NO lead acid battery will survive very long if discharged much more than 50% of its amp/hour capacity. If you run these scooters until the battery begins to sag, you are probably doing a 80% discharge and that will quickly kill ANY lead-acid battery. 30 or 40 very deep cycles like that and the batteries will be toast…


Sorry but this does not fit the fail profile. No account of battery sag was noted. Deep cycle does not meet the application unless the current controller is failed. See my previous posts. Deep discharge did not occur on one battery in series thus neither suffered from your posited issue. DD would affect both. CCA is relevant due to the short start and stop nature of these scooters. CCA reflects the sturdyness of the battery plates. You can make the plates thin and waffle weave and get great slow amp draw out of them. You can make the plates thick and distribute the heat of short cycles easily. You cannot do both.

I missed one point sorry for my own reply. The dealer replaced the battery to MANUFACTURER SPEC. All other issues aside they need to look at the current control system.

You don’t have to disconnect anything.
Be sure to keep the scooter turned off while charging.
Just connect the charger to one battery at a time.
The charger should have a trickle or float mode. Try to always charge at least a couple hours after it switches to trickle.
Later you can get a second charger.
You’ll be OK with balancing every fourth charge.

I own one of the first 10 EGo’s made. The problem is two batteries in series won’t automatically stay in balance. After awhile one gets undercharged and the other overcharged. It helps if they are periodically charged separately with a 12V charger. There is a device called a Powercheq you can attach to actively keep them balanced. ANother approach, the one I take, is to bring out the center connection to a separate jack and use 2 12V chargers. There are a few companies that make a 2 channel charger.

Here’s a shot of me on my electric bike and my wife on the EGo: