Hi
Please bare with me as i am not an expert in electronics and battery-technology. I am very interested in these topics but don't have knowledge deep enough to answer this question:

A contractor installed a lift in my house. It's battery-operated and from what i saw its 6x12v/9Ah lead-acid (sealed) batteries. They are setup as 3x(12V+12V) --> 3 groups in parallel of 2 serial 12V-Batteries.
The contractor attached a consumer (approx 100mA constant draw) to a SINGLE of these batteries. (you'll see it in the attached picture on the top battery)
It seems that the batteries charge as a whole package (the charger outputs 28V). The lift is parked on this charging-station maybe 23h/per day, but it can happen that it remains outside a charger for a whole night (because somebody did not park it properly).

After six months of usage, the performance of the lift dropped drastically. It can barely make it to the top. Red battery light comes up after only a few minutes of operation.

I have the following meassures i can provide, everything other is within the casing i cannot open:
- Single battery voltage (where the consumer is): 11.89V
- Battery-conectors of the lift (where it's charged): 25.2V
- Charger (as stated before): 28V
These readings are in the full state, minutes after moving it off a charger


What are your thoughts about this setup, especially about the uneven loading of the batteries with this radio-receiver attached to 12V?

Thanks a lot, also for being nice about my amateur question!
Chris--> i guess i got the cabling of the motor and charging-connectors wrong, but on my only picture of the batteries these cables are hidden behind a cover...


Disclaimer: I already posted this with the same information on circuitoverflow, but it was closed due to missing information. But i simply cannot provide much more than this because i can't open the lift. I am in the situation that the contractor doesn't want to replace the batteries or optimize the wiring because "it's all installed correctly". The reason it broke down is according to him that "we did not park the lift for days in a charging-station and therefore the batteries are run low and cannot be charged anymore".

 

Welcome to AAC!
1) If a battery is showing only 11.89V fresh off the charger then it is probably damaged and needs replacing.
2) I would disagree that "it's all installed correctly", even if that's what the installation instructions say. A constant 100mA load on just one of two series-connected batteries is almost guaranteed to lead to problems (unless the charger is a balanced type), particularly if the battery capacity is only 9Ah.

I already posted this with the same information on circuitoverflow, but it was closed due to missing information.

The closure seems unjustified. You should have better luck here.

 

Your concerns about unbalanced loading as you describe are correct. You've now seen the consequence.
A better solution would be to power the 12V load from a a 24V-to-12V converter installed across the entire bank.

 

some cheap Pb SO₄ might come in bad condition - if they have been at storage for a long period under not monitored conditions
the gel batteries have limited I/O rates that may be incompatible with your setup
etc. ...

 

It is also very likely that the supplied Batteries are just barely adequate for the job
and are therefore being continuously abused, beyond their rated-capacity,
even under completely ordinary circumstances.

No mention was made as to the Current being demanded of these Batteries,
or the Batteries' factory recommended ratings.
.
.
.

 

unless the charger is a balanced type

how can i figure this out? wouldn't speak the 28V of the charger-ports and the 25V of the charging-connector speak against this?

No mention was made as to the Current being demanded of these Batteries,
or the Batteries' factory recommended ratings.

I agree, for now that's a black-box for me. The batteries are built-in and i have not seen them from the side, i only saw 9Ah per 12V-Battery on the datasheet. But i don't know anything about the rating.
What i wonder: In my memory, lead-batteries are suffering the memory-effect quite quickly. If the battery - under normal circumstances and ignoring the uneven load for a moment - gets used a bit (let's say 50%) and then charged to 100% again, isn't that pretty bad as well?

i googled a bit for better chemistries. What about replacing them with lifepo4? As i see it the only challenge would be heating the batteries that they are never charged below 0 celsius?! Any other thoughts on this type? Or other ideas?

 

Hi
Please bare with me as i am not an expert in electronics and battery-technology. I am very interested in these topics but don't have knowledge deep enough to answer this question:

A contractor installed a lift in my house. It's battery-operated and from what i saw its 6x12v/9Ah lead-acid (sealed) batteries. They are setup as 3x(12V+12V) --> 3 groups in parallel of 2 serial 12V-Batteries.
The contractor attached a consumer (approx 100mA constant draw) to a SINGLE of these batteries. (you'll see it in the attached picture on the top battery)
It seems that the batteries charge as a whole package (the charger outputs 28V). The lift is parked on this charging-station maybe 23h/per day, but it can happen that it remains outside a charger for a whole night (because somebody did not park it properly).

After six months of usage, the performance of the lift dropped drastically. It can barely make it to the top. Red battery light comes up after only a few minutes of operation.

I have the following meassures i can provide, everything other is within the casing i cannot open:
- Single battery voltage (where the consumer is): 11.89V
- Battery-conectors of the lift (where it's charged): 25.2V
- Charger (as stated before): 28V
These readings are in the full state, minutes after moving it off a charger


What are your thoughts about this setup, especially about the uneven loading of the batteries with this radio-receiver attached to 12V?

Thanks a lot, also for being nice about my amateur question!
ChrisView attachment 277704View attachment 277705--> i guess i got the cabling of the motor and charging-connectors wrong, but on my only picture of the batteries these cables are hidden behind a cover...


Disclaimer: I already posted this with the same information on circuitoverflow, but it was closed due to missing information. But i simply cannot provide much more than this because i can't open the lift. I am in the situation that the contractor doesn't want to replace the batteries or optimize the wiring because "it's all installed correctly". The reason it broke down is according to him that "we did not park the lift for days in a charging-station and therefore the batteries are run low and cannot be charged anymore".

Hi C2,
It is true that if these type of batteries are allowed to go low voltage, say 10V each, they can be damaged.
If you are able to disconnect each battery so you can test it, [Make sure you carefully mark each lead before disconnecting] then you may be able to figure out which batteries need replacing, to balance your system.
Bad batteries will affect the good ones.
This is a complicated subject, good luck.
Camerart

 

how can i figure this out? wouldn't speak the 28V of the charger-ports and the 25V of the charging-connector speak against this?

Those figures indicate that the two batteries are charged in series. At the very least, a balanced charger would need direct connections to both terminals of both batteries to monitor their individual voltages so that, if necessary, the charging of one battery could be reduced/stopped while charging of the other one continued. You really need to have the datasheet of the charger to know what its functions are.

 

LifePo4's are a good choice, but quite expensive when compared to SLA ( Sealed-Lead-Acid ).
They have the bonus of more power per cubic-inch of volume.
Probably the biggest problem that your setup has is
Batteries that are simply way too small for the application.
.
.
.

 

Adding an active balancer should keep the batteries in balance even when not on the charger. I wanted to suggest the ones on ebay, but most are for banks of single cells, not banks of 12v batteries. So you need something like this:
https://www.victronenergy.com/batteries/battery-balancer
https://www.aliexpress.com/i/32991400751.html
With the latter you need one module per battery bank, while the Victron handles both with one box, so not much more expensive. I'd consider adding jumpers so the batteries are in parallel sets of 3. I'm pretty sure that's more normal, and will save buying balancers for each string.