# Double batteries for pickup?

**URL:** <https://community.cartalk.com/t/double-batteries-for-pickup/9293>\
**Category:** Maintenance/Repairs\
**Created:** [January 11, 2008, 11:53pm UTC](https://community.cartalk.com/t/double-batteries-for-pickup/9293 "2008-01-11T23:53:07Z")\
**Posts on this page:** 7\
**Page:** 1

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**Author:** ![Adriver](https://avatars.discourse-cdn.com/v4/letter/a/cc9497/32.png) [@Adriver](https://community.cartalk.com/u/Adriver)\
**Post date:** [January 11, 2008, 11:53pm UTC](https://community.cartalk.com/t/double-batteries-for-pickup/9293/1 "2008-01-11T23:53:07Z")

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I’ve got a great '95 Silverado 3/4 ton pickup that carries a camper out into the wilds of Oregon. It is rigged for two batteries and I recently replaced one of them. How much will I gain by replacing the second battery–is it worth the cost? I do value reliablility due to the places I take the truck.

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**Author:** ![mcparadise](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/mcparadise/32/32_2.png) [@mcparadise](https://community.cartalk.com/u/mcparadise)\
**Post date:** [January 11, 2008, 11:59pm UTC](https://community.cartalk.com/t/double-batteries-for-pickup/9293/2 "2008-01-11T23:59:43Z")

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Have the second battery “load tested.” If it passes, keep it. If it fails, get a new one. The load test is the best test of a battery’s ability to start your vehicle.

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**Author:** ![Joseph\_E\_Meehan](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/joseph_e_meehan/32/21_2.png) [@Joseph\_E\_Meehan](https://community.cartalk.com/u/Joseph_E_Meehan)\
**Post date:** [January 12, 2008, 12:32am UTC](https://community.cartalk.com/t/double-batteries-for-pickup/9293/3 "2008-01-12T00:32:23Z")

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```
What is the battery setup? Are they both being used in parallel with no switching between them? Are they separated electrically where one functions for the engine and the other for the camper?
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<div class="post-metadata">

**Author:** ![Adriver](https://avatars.discourse-cdn.com/v4/letter/a/cc9497/32.png) [@Adriver](https://community.cartalk.com/u/Adriver)\
**Post date:** [January 12, 2008, 12:59am UTC](https://community.cartalk.com/t/double-batteries-for-pickup/9293/4 "2008-01-12T00:59:27Z")

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they are rigged in parallel

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**Author:** ![Opera\_House](https://avatars.discourse-cdn.com/v4/letter/o/9dc877/32.png) [@Opera\_House](https://community.cartalk.com/u/Opera_House)\
**Post date:** [January 12, 2008, 4:40am UTC](https://community.cartalk.com/t/double-batteries-for-pickup/9293/5 "2008-01-12T04:40:47Z")

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In parallel operation the batteries need to match each other by age. The older battery may not get a full charge. A couple year old battery has probably already lost 50% of its capacity. A deep discharge below 80% is hard on an auto battery if you run a lot of things in the camper. I have a camp that runs off my vehicle battery. Just plug the house into the car.

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**Author:** ![mr\_josh](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/mr_josh/32/3008_2.png) [@mr\_josh](https://community.cartalk.com/u/mr_josh)\
**Post date:** [January 12, 2008, 9:43am UTC](https://community.cartalk.com/t/double-batteries-for-pickup/9293/6 "2008-01-12T09:43:01Z")

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But they are rigged in parallel with an isolator, correct? If it is a factory setup, there is assuredly an isolator (think big diode) in the circuit to keep one battery from discharging in to another.

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<div class="post-metadata">

**Author:** ![Adriver](https://avatars.discourse-cdn.com/v4/letter/a/cc9497/32.png) [@Adriver](https://community.cartalk.com/u/Adriver)\
**Post date:** [January 12, 2008, 11:08pm UTC](https://community.cartalk.com/t/double-batteries-for-pickup/9293/7 "2008-01-12T23:08:53Z")

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thanks, but did you reallly mean plug the house into the car?