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Electronics expert help needed

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Old 06-27-2016, 06:35 PM
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golf4two
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Default Electronics expert help needed

This question pertains to my electric golf cart but the manufacturer(s) have not been of help so I hope it's ok to post here.

The cart has six 8 volt batteries in series for a total of 24 volts. An "on board computer" controls the external charger.

I also have a 24 volt fan. I have been running off 3 batteries at a time, switching between sets periodically. The charging system reads all 6 as a whole pack so the 3 used get undercharged and the other 3 overcharged.

If I set up two sets of three batteries in series and connect them in parallel (pos to pos and neg to neg) I should still get a total of 24 volts and so be using all 6 batteries simultaneously. Am I correct or will the primary (6 battery) series connection cause that configuration to be 48 volts?

Are there any downsides to this proposed configuration?

Getting at all the components and making all hookups just to try it is a major PITA so an expert opinion would be greatly appreciated.

TIA
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Old 06-28-2016, 05:14 AM
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Six 8v batteries in series provides 48 volts. Three 8v batteries in series provides 24 volts. Parallel another three and amp/hours doubles but voltage remains at 24. Are you certain this cart is supposed to run on 24 volts and not 48??
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Old 06-28-2016, 06:42 AM
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Not sure I am getting this but it sounds as if you want to connect 2 packs of 3 in series batteries in parallel, while at the same time maintaining the primary 6 batteries in series connection. This would ground both 3 packs, and they would aggressively discharge. Saw this done years ago with a novice, some jumper cables, two 12 volt car batteries and a fundamental misunderstanding of how to connect. Results were blown cell caps and battery acid everywhere. Hopefully this is not what you are proposing. If so please don't. Buy another 24 v fan, wire it parallel to the first if it is the same resistance and connect both to the 48v system or wire each fan separately to its own 3 in series pack (would be what I would do to avoid risk of blowing fan with lower resistance regardless of value listed). More airflow, and all 6 batteries discharged.

Also either your cart runs on 48 V or the 6 batteries are not wired in series, your second statement is confusing.

Last edited by dspeers; 06-28-2016 at 06:47 AM.
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Old 06-28-2016, 09:20 AM
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golf4two
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The cart runs on 48V. Fan runs on 24V. Two packs of 3 in parallel would still be 24V for the fan. However, the 48V path must remain for the cart and the 24V packs would be in that path so the result would still be 48V. What I need is a voltage reducer if there is such a thing for those voltages.
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Old 06-29-2016, 12:12 PM
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dspeers
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Draw the circuit, the positive of the first parallel pack would connect to the positive of the second parallel pack, which because all 6 are also connected in series the positive of the first battery in the second pack is connected to the negative of the last battery in the first completing a closed circuit and shorting out the first 3 batteries. Same holds true of the joint negative of the two parallel packs which would short out the second pack.

I apologize, I misspoke when I suggested you wire 2 fans in parallel, they would both see 48 V with 1/2 amperage. You could wire 2 fans in series or yes they do make 48 to 24 volt step down transformers. You can Google same. Still think two fans each with its own isolated 3 battery circuit works best.
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Old 06-29-2016, 05:13 PM
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Originally Posted by dspeers View Post
Draw the circuit, the positive of the first parallel pack would connect to the positive of the second parallel pack, which because all 6 are also connected in series the positive of the first battery in the second pack is connected to the negative of the last battery in the first completing a closed circuit and shorting out the first 3 batteries. Same holds true of the joint negative of the two parallel packs which would short out the second pack.

I apologize, I misspoke when I suggested you wire 2 fans in parallel, they would both see 48 V with 1/2 amperage. You could wire 2 fans in series or yes they do make 48 to 24 volt step down transformers. You can Google same. Still think two fans each with its own isolated 3 battery circuit works best.
OUCH....good thing I didn't try it! Thank you very much for that insight. After some considerable searching found a suitable transformer on Amazon. The current fan is quite wide, roof mounted, and has several louvered vents for both driver and passenger, much like the a/c vents in an automobile. Mounting two fans wouldn't be feasible. Thanks again.
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