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Discussion Starter #1
Hi all,

I've got a 1981 Sebring Commuta-Van running at 24V, whose battery charger system is nonfunctional. I am considering purchasing a charger system, which would consist of a number of solar charge controllers powered by a shared DC power supply running off of a 110V extension cord. The current batteries are only 38AH; they are Yuasa SLA Deep-Cycle batteries. Given the bulk charge rate is 9.5A per cell, the 12V charge controller would be a good match. Four cells will draw 562A, hence the DC power supply selection. I would plan to leave the charge controllers in place on each battery, and mount the DC power supply in the vehicle, so an extension cord would be used to top off the batteries.

My question is: does this make sense? Would the float charge attained by the chargers be close enough to justify foregoing a balancer?

The circuit when the 4 cells are connected has two packs at 24V running in parallel, with a relay opening or closing the circuit to a series-wound 220A DC motor with a 200A fuse.

I have other questions related to the project which I will be posting in other relevant places on the forum.
Thanks in advance!
 

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You only need a 3 mile range?

I would get the car tested and working before committing to some sort of solar charge controller


Also it sounds like a bad idea, maybe good for an experiment but sounds like a lot of potential failure points

Also your c-van is normally 72 volts
A citivan is normally 48volts which via contactors could be configured into 24 volts
 

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Discussion Starter #3
You only need a 3 mile range?

I would get the car tested and working before committing to some sort of solar charge controller


Also it sounds like a bad idea, maybe good for an experiment but sounds like a lot of potential failure points

Also your c-van is normally 72 volts
A citivan is normally 48volts which via contactors could be configured into 24 volts
It is working, I've done a few loops around the lot. And yes, the objective is to go back and forth between two adjacent buildings (up 50' of elevation as well).
I know the C-Van was at 72V, but I've had a terminal blow on the battery pack running at 36/72V so I am running at the lower speed as I find it adequate for what we need. I may bump it back up to 36V and run it only in speed 2 to extend the range. The original motor control system functions as it ought to, but other parts of the accessory circuit are a bit wonky.
 

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One thing I notice, however, is that there is no capacitor or Schottky diode across the terminals of the motor, and wonder whether I blew the battery by not adequately polishing the terminals when assembling the 36/72V pack, causing runaway resisitive heating, or by coasting downhill with the car in gear, and then closing the circuit, I caused some kind of transient discharge current to surge through and blow the terminal. The 200A fuse was unharmed. Could it have been both factors? After blowing the terminal, the cable end it was hooked up to felt warm to the touch, unlike any other component in the system. Perhaps bumping it up to 72V was what caused the improper contact to blow.
 

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Quick update:

I purchased and installed a series of solar cell charge controllers (1 for each battery), in order to control input current based on cell voltage. I then attached one to a 30A 24VDC power supply. It worked as intended, up until it fried the power supply. I took it apart and can see that one of the MOSFETS has melted a bit and the resistivity on the full-bridge rectifier seems abnormal, but I'll have to de-solder the components to check.

I want to try this again, but use an LM338 as a constant 5A current source between the 24V bus and each charge controller. I had mistakenly assumed that a 10A charge controller would limit its current draw to 10A, and had also made sure that short circuit and overcurrent protection were featured in the power supply, but the setup did not work as intended. Any suggestions on this plan going forward?
 
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