Need a LOWER output alternator. Will a 97/98 alternator work in a 99??
#1
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Newbie
Joined: Dec 2022
Posts: 23
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From: Oregon
Year: 1999
Model: Cherokee (XJ)
Engine: 4.0
Need a LOWER output alternator. Will a 97/98 alternator work in a 99??
I'm in kind of an odd situation in that I need a LOWER output alternator for my 99XJ (to play nice with the BMS of a lithium battery) and I see that the 98/99 is rated at 90amps. However, the 99 has a plug and the 97/98 seems to have two studs. Are these the same charging systems just with a different method of attaching to the CPU or are they different in some way that makes them incompatible? It would be great if I could just strip the plug wires and use the earlier alternator. Having a hard time finding information so any replies are much appreciated. I'm also wondering if a 117A alternator ever actually reaches max output. If it's only charging at 90 or below in real life then I'm good already!
#2
Others can help more than me , but I think it will be ok as long as you make the plugs compatible (by cutting & joining)
They are Denso 90A and they are regulated by the PCM, so as long as the systems are similar, it should work, but ur wise to research
However, I am thinking it may be better to consider another dual battery controller that can cope ??
They are Denso 90A and they are regulated by the PCM, so as long as the systems are similar, it should work, but ur wise to research
However, I am thinking it may be better to consider another dual battery controller that can cope ??
#3
Senior Member
Joined: Dec 2018
Posts: 704
Likes: 374
From: Harrisburg,Pa.
Year: 1999
Model: Cherokee (XJ)
Engine: 4.0L
The alternator will only put out what the total system requirements are...It doesn't magically throw out the full amperage unless there's something calling for that much draw... Not sure what you're doing but the biggest factor for the lithium battery charging system upgrade is the temperature sensor and some type of charging cut-off if you're retrofitting it...
#4
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Newbie
Joined: Dec 2022
Posts: 23
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From: Oregon
Year: 1999
Model: Cherokee (XJ)
Engine: 4.0
Unfortunately dual battery costs me more weight and space than I can afford, and fortunately this battery is rated for the use, just need to keep the alternator within spec.
#5
Thread Starter
Newbie
Joined: Dec 2022
Posts: 23
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From: Oregon
Year: 1999
Model: Cherokee (XJ)
Engine: 4.0
The alternator will only put out what the total system requirements are...It doesn't magically throw out the full amperage unless there's something calling for that much draw... Not sure what you're doing but the biggest factor for the lithium battery charging system upgrade is the temperature sensor and some type of charging cut-off if you're retrofitting it...
#6
Full alternator output capability is usually rated at 6000 rpm. You'd need to measure the crank and alternator pull diameters to figure out what that translates to in engine rpm. I think the alternator pulley is 2-1/4" and the balancer is 7" which would mean full output capability around 2000 rpm. You're saying the full rated output of the alternator is higher than your bcm can handle? I would expect the BCM to only pull as much current as it needs to charge. PCM will control the alternator output current to maintain the voltage.
#7
Thread Starter
Newbie
Joined: Dec 2022
Posts: 23
Likes: 2
From: Oregon
Year: 1999
Model: Cherokee (XJ)
Engine: 4.0
Full alternator output capability is usually rated at 6000 rpm. You'd need to measure the crank and alternator pull diameters to figure out what that translates to in engine rpm. I think the alternator pulley is 2-1/4" and the balancer is 7" which would mean full output capability around 2000 rpm. You're saying the full rated output of the alternator is higher than your bcm can handle? I would expect the BCM to only pull as much current as it needs to charge. PCM will control the alternator output current to maintain the voltage.
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