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Old 08-21-2015, 11:32 PM   #1
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Battery Upgrade Question

I have some questions for anyone who has upgraded their batteries to Lifelines AGMs with over 300AH capacity.

Did you also upgrade the wire from the Sprinter battery to the House batteries that goes through the BIM?

If you have the big batteries and haven't upgraded the wire to the BIM have you had any issues with the wiring or the alternator?

In my 2013 model Interstate this wire is only 4 gauge, with a 150Amp fuse; adequate for the stock two Lifeline GPL-24T, 12V with combined capacity of 160AH.

I'm planning to upgrade with four GPL-4CT, 6V with 440AH capacity. My concern is that the stock 4 gauge wire and BIM rating of 200Amps will not be able to safely handle the charge current that the house batteries could draw from the Sprinter battery/alternator when they are significantly depleted, like 50% DOD.

The charging section of the Lifeline Technical manual says the low impedance of their AGM batteries can tolerate in-rush currents at very high levels. With a 440AH house pack that is depleted to 50% DOD it could easily take in the full capacity of my Sprinter alternator, likely about 200Amps.

BTW - From the wiring diagrams in the 2015 Owners manual Airstream has upgraded the wire to the BIM to 1/0 gauge wire and the capacity of BIM to 225Amps.

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Old 08-22-2015, 01:36 AM   #2
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Quote:
Originally Posted by Boxster1971 View Post
I have some questions for anyone who has upgraded their batteries to Lifelines AGMs with over 300AH capacity.

Did you also upgrade the wire from the Sprinter battery to the House batteries that goes through the BIM?

If you have the big batteries and haven't upgraded the wire to the BIM have you had any issues with the wiring or the alternator?

In my 2013 model Interstate this wire is only 4 gauge, with a 150Amp fuse; adequate for the stock two Lifeline GPL-24T, 12V with combined capacity of 160AH.

I'm planning to upgrade with four GPL-4CT, 6V with 440AH capacity. My concern is that the stock 4 gauge wire and BIM rating of 200Amps will not be able to safely handle the charge current that the house batteries could draw from the Sprinter battery/alternator when they are significantly depleted, like 50% DOD.

The charging section of the Lifeline Technical manual says the low impedance of their AGM batteries can tolerate in-rush currents at very high levels. With a 440AH house pack that is depleted to 50% DOD it could easily take in the full capacity of my Sprinter alternator, likely about 200Amps.

BTW - From the wiring diagrams in the 2015 Owners manual Airstream has upgraded the wire to the BIM to 1/0 gauge wire and the capacity of BIM to 225Amps.

Thanks,
- - Mike
With a 440 amp/hour Lifeline battery bank, I typically use 2/0 class K welding cable and a 300 amp class T fuse for the inverter. In the short distances of the AI, you can safely use 1/0 cable and a 200 amp class T fuse.

Remember that the fuse is to protect the wire and not the device, but larger wire capacity is always beneficial, as long as the circuit protection is upgraded at the same time.

I always use class T fusing rather then the smaller, less effective fusing that Airstream uses to provide greater amperage interrupt capacity (AIC). A class T fuse usually has a 20,000 amp AIC, while the ANL or ANN type fuses that come with your AI have a 4000-6000 amp AIC rating. Dead shorts in a battery or heavy gauge cable can easily exceed a transient 10,000 amp draw.

ABYC marine electrical specifications (E-11) call for class T fuse use over any other fuse type in most heavy DC applications.

Better safe than sorry.
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Old 08-22-2015, 10:43 AM   #3
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Thanks Lew. I was planning on heavy wire like 2/0 and a 300Amp Class T fuse for the inverter.

The wire I'm talking about is the one from the Sprinter battery under the driver's seat floor that runs nearly the entire length of the van along the roadside floor and then connects to the BIM relay. This wire provides house battery charging when driving.


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Old 08-22-2015, 10:45 AM   #4
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Originally Posted by Boxster1971 View Post
Thanks Lew. I was planning on heavy wire like 2/0 and a 300Amp Class T fuse for the inverter.

The wire I'm talking about is the one from the Sprinter battery under the driver's seat floor that runs nearly the entire length of the van along the roadside floor and then connects to the BIM relay. This wire provides house battery charging when driving.


- - Mike
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1/0 with a 200 amp fuse should have all the capacity you need for the BIM application.
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Old 08-22-2015, 11:59 AM   #5
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1/0 with a 200 amp fuse should have all the capacity you need for the BIM application.
Thanks, I agree - but mine only has a 4 gauge wire and 150 amp fuse. That's all Airstream installed in 2013. Will that be adequate or does it need to be upgraded? Do you upgrade the wire from the Sprinter battery to the BIM when you upgrade to 440AH AGMs on older Interstates?

I'm not sure when Airstream made the upgrade to 1/0 and 200Amp fuse, for sure it's on the 2015 models.
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Old 08-22-2015, 01:12 PM   #6
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The 150 amp fuse on a 4AWG cable seems excessive. I would keep the 4 AWG and downgrade the fuse to 50 amps. I doubt that you will see more charging amperage from your alternator thru the BIM than that.

We use a 50 amp marine breaker on our 4AWG solar charge lines. That would also work well.


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Old 08-22-2015, 01:51 PM   #7
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Thanks Lew - great advice as usual.


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Old 08-22-2015, 06:15 PM   #8
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This discussion is going to make me take another look under the lounge......my 2013-late year construction.....came with 200 amp fuses. I did not check wire gage while under there the last time.

Hmmmmmmm



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Old 08-23-2015, 12:38 PM   #9
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Mine was an early 2013 model that I bought in Oct 2012, so maybe they made the change during that model year. I've verified the wire size from my Sprinter battery to the BIM as 4ga, same as the 2011 wiring diagram I found. For some strange reason Airstream would not send me the Main DC wiring diagram when they sent me seven other wiring diagrams for my 2013. I even asked for all diagrams a second time and was told the ones they didn't send me were for Airstream in house use only. Now they include the wiring diagrams in the owner's manual.

But I haven't verified the fuse size at the Sprinter battery. However I'd imagine it's a 150 amp fuse as most sources I've read say 150 amp fuse is OK to protect 4ga wire. This was the last source I found on Blue Sea's web site.
http://assets.bluesea.com/files/reso.../980006450.pdf



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