My wife retired on 12/30/22. Her car, a 2013 Lexus ES350 has been sitting in the garage and only driven a couple of short trips for the last month. I have a spare Schumacher SC 1355 1.5 amp maintainer and would like to use it to keep the battery charged as her car has a lot of parasitic drain on the battery. I’m a bit hesitant to use it thinking it might do some damage to the electronics in the car over a period of time. I’ve used these maintainers for years on my motorcycle and riding mower with never a problem but her car has so much electronics I’m wary it might cause some sort of electrical gremlins to show up and do some damage over time. The maintainer is supposed to be a ‘smart’ maintainer so I feel it will be OK but I thought I would ask here before I hook it up.
Battery maintainer and sensitive electronics
- Thread starter gman2304
- Start date
An automotive electrical engineer will design the circuits appropriately for all expected use conditions, which includes the use of a maintainer.
In other words, if a battery maintainer causes damage to some electrical component of your Lexus ES350, the engineer who designed it was incompetent.
In other words, if a battery maintainer causes damage to some electrical component of your Lexus ES350, the engineer who designed it was incompetent.
No electrical device is 100% fail safe, not even a well designed one. A battery charger can potentially fail in some way and potentially damage the electronics on a car. It is probably a tiny risk, but still a risk.
It could be beneficial to power the charger through a surge suppressor so that lightning strikes or other voltage spikes don't reach the car electronics.
It could be beneficial to power the charger through a surge suppressor so that lightning strikes or other voltage spikes don't reach the car electronics.
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I put my el cheapo black and decker charger on our 2019 Toyota all the time. It has all the nanny's - Toyota sensing 2.0, the JBL system, etc. My guess is far more elctronics than your much older Lexus. No ill affect so far.
I figure the alternator can dump 100A up to 14.5 volts into the same system on its own, surely it can handle a couple amps from a charger - no?
I figure the alternator can dump 100A up to 14.5 volts into the same system on its own, surely it can handle a couple amps from a charger - no?
Automotive electronics are supposed to be designed to handle a load dump. A load dump results in a lot more voltage than you'll ever get from a battery maintainer.
Load dump - Wikipedia
I use several different types of maintainers for my vehicle batteries and I think you'll be just fine. I also believe that the Schumacher is well made as is mine and is reverse polarity protected. I installed a Schumacher mountable maintainer 1.5v in my vehicle so I can just plug-in without opening the hood. I installed my own(proper grade)long extension cord to feed down into the grill area(each vehicle is different) so I can just plug-&-go.
This is the one that I recently bought to replace the 21 yr old Schumacher Maintainer that didn't work any longer. It's similar in size to my old one but waaaaay lighter.
This is the one that I recently bought to replace the 21 yr old Schumacher Maintainer that didn't work any longer. It's similar in size to my old one but waaaaay lighter.
The owners handbook for my car explicitly addresses this issue of potential damage to electronics by stating the maximum safe charging voltage with the battery connected to the car should not exceed 14.8 volts. I would have thought other cars are similar. I'd measure the voltage with the maintainer hooked up. It should be much lower than that when float charging.
I have used CTEK battery maintainers on electronics rich Corvettes and sensitive amateur radio equipment for years without damage or harm. In fact, General Motors sells them with their brand logos as factory accessories.
I don't know anything about the unit you own, but I do know CTEK units can be safely used.
I don't know anything about the unit you own, but I do know CTEK units can be safely used.
It is NOT the Lexus engineer's job, but the maintainer's engineer job to design it not to damage any circuitry.
I would use a maintainer, not a cheap one, preferably one of the smart ones so that there will be no overcharging.
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Electrically speaking, the 12V bus in a vehicle is a dirty, nasty place--and a battery maintainer won't make it any dirtier or nastier.
One thing that IS a concern IHMO is that battery maintainers should have a fuse on the output wire, so that an internal fault or short in the maintainer won't cause it to go up in flames due to the huge amount of fault current available from a car battery. This may be a UL requirement; the $9 Harbor Freight battery maintainer I use has a small box on the output wires near the battery clamps, and I suspect that there is a fuse inside, even if it's just a circuit board trace that functions as a fuse.
f355spider
$50 Site Donor 2024
You will be fine. I have used maintainers for years on all my vehicles for years without issue.
Update: I hooked up the little Schumacher 1.5 amp battery maintainer yesterday at 09:00 am and it indicated (amber charging light) charging all day and when I went to bed at midnight last night it was still charging. Got up at 7 am and it had the green charged light on indicating it had gone into float mode. I checked the battery voltage a couple of times and it’s been consistently indicating 12.66 volts. The manual indicates the desulfation feature takes 8 to 10 hours to complete so it having charged 15 plus hours I’m assuming it has desulfated as well. The manual states if desulfation fails, the red light will come on indicating it had aborted this step. No red light display so I feel all was well in each mode. I’ll probably let it float a few days and drive it this weekend. 
Assuming a battery temperature of around 77F that float voltage is too low. It won't keep up with the parasitic drain. Are you sure it does not occasionally get up to 13.x volts in float mode?I checked the battery voltage a couple of times and it’s been consistently indicating 12.66 volts.
Battery Charging Basics
www.batterytender.com
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f355spider
$50 Site Donor 2024
Agreed, seems a little low. I'm not an expert for sure, but 12.66 won't get the battery fully charged. Most battery tenders will bring a battery up to 13.2 to 13.8vt float voltage, that I have observed. And if it has a temperature compensation sensor, and AGM setting, it can even go over 14vt in cold weather.Assuming a battery temperature of around 77F that float voltage is too low. It won't keep up with the parasitic drain. Are you sure it does not occasionally get up to 13.x volts in float mode?
Battery Charging Basics
I recently discovered one of my really old Battery Minder "wall wart" battery tenders only floated at 12.6 volts. I tossed it in the garbage. Not sure if it had always been doing that, or recently failed. I hadn't used it in years.
