Long term battery tenders and water level

Wayfun

I'm new to golf carts and I recently picked up a '91 CC DS for use in FL. It has new batteries and I want to do what I can't properly maintain them. In the spring I will have to leave the cart on my lot through the summer and fall unattended. The dealer told me to just charge it up and disconnect the cables and leave it. He said it "should" hold enough charge over the 7 months.
I'm thinking he it would be better to attach a battery tender but I'm concerned that the water level may not hold. Should I be concerned? Is this the right strategy?

Thanks,
Dennis

BGW

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Olman

Dennis---I bought my cart in June and bought a Save-A-Battery charger/maintainer to go with it. If I am not on the cart, it is on the maintainer. I haven't had to add water to the pack yet.

Volt_Ampere

If you have access to electrical power, I would get a battery tender for it. The batteries do not hold enough charge over 7 months to prevent some sulphation damage. I leave my car on a tender all winter in Colorado and all summer in Arizona. Worth the cost as it will greatly extend the life of your batteries.

Sergio

Your dealer gave you the safest option.

If you use a battery maintainer type device, make sure you put the cart on TOW and then disconnect the negative cable from the pack.

If you leave the pack connected, the OBC will still try to charge the batteries and will eventually go into shutdown mode, no big deal, but disconnecting the cable will eliminate the OBC drain from the batteries.

I don't have anything against battery maintainers, they are a good idea. My issue is with the "totally unattended" aspect of using them.

Electrolysis, not heat, is the main cause of water loss in the batteries. If a single cell out of 24 of them goes bad, the other batteries will raise their voltage to compensate the "total" voltage level of the battery maintainer. If that takes them above gassing voltage, they will go dry eventually.

Wayfun

Thanks Sergio, I hadn't thought of a bad cell condition. Is there a table that would show voltage loss over time? I'm just concerned about the voltage dropping too far. I guess it works because there are dozens of carts in our neighborhood that set unattended for 7 to 9 months a year.

Sergio

The self discharge rate is slight different for each battery, You would need to check the web site for your particular battery.

I just noticed that You would be storing it during summer in FL, the rate of discharge would be a lot faster at 80F, and 7 months is a long time.

The best option in this case would be to disconnect the pack from the cart and leave it plugged to the maintainer.

Also, don't add water right before you disconnect the pack. You want to have at least 3 to 5 discharge/charge cycles after you add water before disconnecting the pack.

One of the possible side effects of keeping the batteries for a prolonged time in a battery maintainer is stratification of the electrolyte. Sulfuric acid has a higher density than water, which causes the acid formed at the plates during charging to flow downward and collect at the bottom of the battery.

My personal opinion is that the way the OBC behaves is better for the batteries in the long run as the gaseous reaction causes a convection current which mix the electrolyte and resolves the stratification issue.

I have no personal experience in keeping a cart unused for that long, so go with whatever the method that other folks are using, but if possible, have someone check the batteries once every month or two.

joesam

Before I got a battery maintainer, my original plan for long term storage was going to be using my OEM charger, turned on about once a week for an hour. I live in a "Smart Home" and it would have been easy to program the outside plug to turn on and off once per week. Trouble is...the stupid OBC prevents that from working. Turning AC on and off does not restart the OEM charger. Only pulling and replacing the cart's charger plug does that. I know the OBC is supposed to turn itself on and off as needed - but it happens so infrequently I've never seen it. And I guess I just don't trust what I can't see. Not sure what the impact of a big charger would be with a dead cell, when it does turn itself on (but it couldn't be good).

I never thought (or knew) about acid stratification, but long term storage with no charger in HOT temps has killed the battery packs of a few of my Phoenix buddies' carts. So a maintainer is your most logical option, I suspect.

Olman

I found this in the literature on my charger:

"The way our units work starts when the charger is plugged in. The
microprocessor immediately checks for a good battery before it turns itself
on. This eliminates the problem with sparks, short circuits and possible fire.
If our unit sees the correct polarity, correct battery type, correct battery
voltage, and a battery it can charge it will go into it’s first stage, Bulk Charge
Mode. This mode does 80% of the charging and with our 50 watt output it
performs twice as efficiently as many other charger and much faster than
most of the maintainers on the market. Once the battery reaches it’s 80%
level the charger changes into Absorption Mode. This is where it slows
down the charging rate so as not to overcharge the battery with a minimum
of electrolyte loss or battery damage due to overcharging. It is virtually
impossible to overcharge with this type of system. Once fully charged we
switch into Maintenance Mode which feeds the battery just enough to keep
it fully charged. The charger stays in this mode most of the time but
periodically switches into pulse mode where it basically cleans the battery
plates, and de-stratifies the electrolyte helping to equalizing the cells. This
process reduces sulfurization which improves battery life."

According to this, the unit periodically de-stratifies the electrolite.

Sergio

Joesam:
One solution would be to use something like these cheap inside the charger, directly connected to the AC input (Before the Charger Relay).

You then just have to run the sense wire through the Normally Open contacts of the Fan relay. If power goes out, it simulates the DC cord from the charger being unplugged from the Cart.

Fan relays are rated for continuous duty.

Olman:

That sounds like a pretty good charger/maintainer, still if a breaker goes off during a storm, it is nice to have someone checking the batteries occasionally.

I guess my point was if you can have someone checking the Cart, there are a lot more options on how to maintain the batteries.

Volt_Ampere

I wouldn't want to use a charger to maintain the batteries for 7 months without being able to add water to them. The charger will gas the batteries. The maintainer really doesn't gas them much.