Author Topic: I need a single cell charger for my forklift battery. So....  (Read 2076 times)

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Offline Watt

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I need a single cell charger for my forklift battery. So....
« on: September 26, 2013, 09:43:14 pm »
In IRC, we have discussed a need for a 2.5v charger to help exercise or nudge along a tired cell.  Thanks to Kurt and Madscientist, I was able to use a home wired transformer,caps and some rectifiers to add a some amps to several cells that were slow to increase SG with the array alone.  These cells took several weeks of charging and discharging to increase their capacity to match the rest of the otherwise better cells.  This is a rough method as I have to be there to monitor the voltage and switch the transformer on and off.  Also, the Kwh usage of the grid or running the transformer from the RE stuff adds up.  So...

I have an extra 230w solar panel.  This panel has the following specs. 29.3vmp 7.8Amp and Voc of 36.8v

What I'd like to do is let some factory smoke out of a few electronic devices to try and build a buck converter or as Kurt, in IRC suggests, a vibrator circuit rectified after a transformer for adding a bit of current to the one cell while the main array maintains the other cells as usual. 

The reason for the single cell device is to decrease the amount of absorb time and help minimize the often required equalize stage to bring this one cell closer the capacity of the other 23 cells.  It takes around 5kwh at 48v nominal to increase absorb stage long enough to bring the SG up on the one weak cell.  Each charge and discharge cycle seems to bring the one cell up but is costing near a full 50 gallon water heated amount of energy.  So, I'm thinking I might as well put this one solar panel to use and learn a bit in the process....

Here is the battery... 



Here is the transformer get up before the caps were installed on the input and I tapped the output for a few volts....  will get an updated picture soon....  Nothing fancy or nice about it, it's got a job to do, I don't care about looks really.



Will get a panel picture soon...
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Offline Watt

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Re: I need a single cell charger for my forklift battery. So....
« Reply #1 on: September 30, 2013, 08:26:50 pm »
In IRC, Ross suggested another way to use this solar panels output to charge a single cell. 
So I ordered 5 of these dc - dc converters off ebay to work in parallel. 



DC-DC Buck High Power 15A Buck Adjustable Step Down Converter 4-32V 12V to 1.2-32V

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Re: I need a single cell charger for my forklift battery. So....
« Reply #2 on: July 28, 2016, 02:24:45 am »
After some discussion in IRC and realizing that these converters will require their own power source, I ditched this idea for something better.  Individual cell monitors!
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Re: I need a single cell charger for my forklift battery. So....
« Reply #3 on: August 19, 2018, 11:11:56 pm »
So here they are.

The forklift batteries were working well and the monitor, along with some coding by RossW, set the stage for expanding. 24 - 1807Ah @ 20 AGM cells. With some spares.

The cell monitors are sitting on the cells and connected to a Raspberry pi2. We have also built a cell balancer from bits and pieces and controlled by a Raspberry pi3. The balancer has a 2V charge, 5A discharge and 2.5A discharge per cell option. All of it could have been controlled by one pi but, they were put together separately and down time for the monitors was not acceptable. I count on the monitors daily. The other picture is of the laziness in wiring.
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Re: I need a single cell charger for my forklift battery. So....
« Reply #4 on: August 20, 2018, 04:45:06 pm »
screenshot of the last 24hr progress with the balancer.
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Re: I need a single cell charger for my forklift battery. So....
« Reply #5 on: August 20, 2018, 10:16:03 pm »
graph of cells with resistance balancing off when net current is '0'. Gonna try balancing with resistance during 0 net current to see how much load is required over night.
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Re: I need a single cell charger for my forklift battery. So....
« Reply #6 on: August 26, 2018, 07:05:09 pm »
A week of the cells balancer active.
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Re: I need a single cell charger for my forklift battery. So....
« Reply #7 on: January 23, 2019, 12:04:54 pm »
Here is an updated graph showing the impact of monitoring.
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Re: I need a single cell charger for my forklift battery. So....
« Reply #8 on: January 23, 2019, 07:42:05 pm »
I need to do some more work to the balancer and add a little more load to help bring the cell voltage spikes in line a bit more. I also need to do a quicker poll to help prevent spikes. But, after 5 or so months, it is still working well as a system.
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