Battery taken out when 4wding

[TheMuGuy]

Hey everyone, I was out 4wding last night and I turnt my car off and it wouldn't start back up because the battery was dead so we chucked the battery out of my brothers car into mine to start it then quickly changed the batterys back over, was this safe to do? eg. could've it broken anything being out? was only out for 30 seconds or less while engine was on, this is in my 1995 Isuzu Mu

Thank you

[geeves]

not a wise thing to do as the battery provides a resiviour for alternator current and doing this can blow an alternator. You would know by now if this had happened. Much better to use jumper leads.
Why did the battery go flat?

[TheMuGuy]

Not sure why it went flat turnt off the car and turnt the spotties and lights off at the same time, then tried to start her and just didn't turn over, we didn't have jumper leads on us at the time, then on our way home my car just stopped lights turnt off same with motor and battery was dead flat

[TheMuGuy]

May aswell ask on this thread instead of starting a new one, also would anyone know the Stock height for a 95 Isuzu Mu? I understand that suspension will sagg over the years ( Centre of Hub to top of guard)

[geeves]

test your alternator
start by charging battery and reinstalling. Clean the battery terminals at the same time. Ive had a white oxide before that was a very good insulator. Before starting the car check voltage at the battery This should be slightly over 12 but anything over 11.5 is ok. Turn headlights on and retest. It shouldnt drop more than 0.1 volts. Any more and you have a dud battery. Turn lights off and start car. At idle it should be between 12 and 14v Rev and hold at 1500rpm You should have 14.5v Any less and your alternator needs attention. Rev to 3000 It should remain at 14.5 If it increases beyond this the voltage regulator needs changing. If its low at the first test but ok at second its probably just brushes but low on both will be either alternator or charge relay (blue one) If it stays at 12 do the relay first

[TheMuGuy]

Tested and its at 13V when off 12.8 on idle when revving it's still 12.8, so thinking I do need a new alternator, I'm thinking the alternator was already broken as battery went flat for no reason as was driving with just normal head lights on whole time and radio off, is there a place online to buy a alternator at a good price or would my best bet be just going to a wrecker? Thank you so much for your help

[geeves]

try the charge relay first its cheaper and easier

[TheMuGuy]

How do I check if it's the relay?

[geeves]

Change it with a spare. The only catch is that its rare for them to fail on there own. Most common failure is alternator regulator fails causing alternator to go high volts which cooks the charge relay. This can take a few minutes so enoufgh time to test it