M915 Electrical 911

[wreckerman893]

We got Jeremy's (Bighurt) M915 running Wednesday but now we are having electrical problems.....I knew the system was 12/24 volts but I did not know that the batteries were where the voltage was split.

We may have fried something and we need expert advise tomorrow when we try to fix it. I am thinking maybe a breaker but there may be a didode or some other protection device that I don't know about.

If anyone has any ideas PM me a phone number we can contact you at or I will send you mine.

Thanks from Elmo and the rest of us.

 

[StreetbikeDepot]

So it sounds like you hooked up the 12 volt power feed to the last battery in series? The best thing to do is hook it up correctly to the first battery in series and see what works and what doesnt. I would be more concerned with the charging system. Those truck have a Neece-Leville alternator that outputs 12v (14v, 85 amp) with an integral regulator/rectifier but it also has an external 3 phase regulator/rectifier on the backside to output 24v. On the 12v side of the system there are output diodes and a diode trio you could have knocked them out, if that is the case you need to find an alternator shop.

I'm not sure if the truck was power up with 24v to the 12v side so plan on replacing any bulbs that tried to power up with 24v(not that big of a deal) and you will need to make sure that the fuel shutoff solenoid is ok (I would imagine that it would have survived the hit).

 

[NDT]

The only diodes are internal to the alternator. The 8 gauge wire that enters the battery box is the 12 volt feed to the 12 V electrical system bus in the dash circuit breaker cabinet. PM sent with phone # for tomorrow. If you have smoked the alternator, replace it with a more available 12 V only alternator. The second pair of batteries will power the starter for many days with needing a charge.

 

[StreetbikeDepot]

Jeremy has my number, give me a call at the shop tomorrow if you need any advise. Those alternators are really common (except for the external 24v R/R portion but it should be ok) most alternator shops should have the parts in stock to fix it, mine did.

 

[R Racing]

You have to run the first 2 batteries in parellel and take the 12V off of that . Then you run the second set of batteries in in series from the 12v and parellel to each other for the 24v . I have pictures if you need them .Jeremy has my # I will be around in the AM if he needs a diagram or mor pictures. U can see the 8 gauge wire on the 2nd set of Batteries on the + 12v and the - to the 24V side in the pictures.

Jim

 

[StreetbikeDepot]

FYI....if the 4 battery set up is confusing, just remember that the extra set of batteries that is hooked up parallel (+ to + and - to -) is only to raise the amperage and on the 915 you do not need 4 batteries it will work just fine with two batteries in series. I only run two batteries in mine and have not had an issue with starting.

So with only two batteries in series theoretically 12v can get pulled from either battery as long as the ground source is pulled from the same battery (isolated ground, which is not the case with the 915). If you try to get power from the outside positive and the outside negative you will get 24v. So in your case the 12v and the 24v system both share the sme ground......you need to make sure your connecting your 12v + lead to the battery that has the ground connected to the chassis.

 

[wreckerman893]

Thanks to all that replied.....I think he got it squared away.....we got the batteries secured and the cover is in place now. We are now doing some small things and getting the brake/tail/signal lights working correctly.

If all is well Jeremy and Brandi should be exfiltrating the LZ early this afternoon.

 

[R Racing]

Great !!