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Originally Posted by kenfrank
I checked all of the batteries, had 2 loose connections. Fixed that.
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Good start.
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On the batteries pack the last battery the neg- post gets hot and smokes. What could be causing this?
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If the connection is tight, my first guess would be some corrosion. If you remove the cable and use an emery cloth sanding block to shine up the battery post and the battery cable lug (the side that touches the battery post is the only side that needs to be shiny), then put the cable back on the battery post and tighten it up - it should not heat up any more.
The other end of the cable may also be the problem. If that connection is corroded, it will heat up the whole cable and the battery post as well. The smoke may be the plastic on the cable, or the varnish on the copper wires. Either way, it's too hot!
If the hot cable is connected to the fuse, the fuse holder will be hot as well. The way a fuse triggers is based on heat (current * current * number of seconds) so heating up the fuse may cause it to trip when there is not really too much current flowing through it. And DC fuses are usually expensive.
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The wire coming off of the dc-dc convertor +V1 one end goes to the 250 amp breaker to the + postive side of battery pack has a fuse in it that keeps blowing out.
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The fuse for the DC-DC converter blows, right?
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The other wire coming off of the +V1 went to -neg side of the big 300amp fuse.
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The other wire comes of the -V, right? I've heard of DC-DC converter fuses failing when you accelerate hard. Putting a diode (rated for at least twice the current you expect the converter to use) between the +V1 and the breaker should fix that (allowing current into the converter, but not back out). If you are still burning fuses, some people have had success adding an inductor. The size depends on how big the capacitors are in your converter and how much your battery voltage sags. There is still some debate how much the inductor helps, if at all.
But if V1 is connected to both the positive and negative of your pack, it obviously won't work.
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Now nothing works. What am I doing wrong? Any sugestions?
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If 'nothing works' means the contactors do not close, then your DC-DC converter may have failed. It is a common problem in EVs. You can test that by wiring a 12V battery to your 12V system and see if some things work again.
Some EV conversions have a small lithium 12V battery pack that they use instead of a DC-DC converter. It avoids some problems, but requires another charger and a separate battery.