Cheap diy dual battery setup

[TabarnaCarl]

Hi

I just brought a 12v cooler. I already had a small bluetti eb3a, but it's kinda not enough to power the cooler for 12 hours.

I'm looking to do a cheap diy dual battery setup. I have a 2 doors and I do "OvErLaNd" stuff, so space is important. I found a deep cycle battery that will fit in the aux battery location (aux battery already deleted)

-Cooler is a bodega 40quart, 60 watts 5amp
-Deep cycle battery I've found to fit in the aux battery location is 30ah

Other than a smart battery isolator and couple inline fuse, what would I need ?
I've read I might need a DC to DC charger ?
Anything else I should know with our "smart alternator" ?

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[THAW]

A battery isolator won't charge a deep cycle AGM battery optimally, causing shorter battery life. A DC-DC charger is a better solution, but it's typically more expensive and has a slightly larger footprint. A DC-DC charger is required if the second battery is lithium-ion.

Which 30Ah battery fits in the AUX (ESS) battery box? FYI, 30Ah is less than your BLUETTI, which is about 37Ah.

 

[rcitone]

Similar use case. I bought a LifePo4 battery and a cheap Amazon DC-DC charger (15v 5A constant output). The charger is controlled by a switch. I monitor the Voltage of the battery manually to determine when to turn on charger.

 

[THAW]

FYI, 30Ah is less than your BLUETTI, which is about 37Ah.

@TabarnaCarl, I read the wrong BLUETTI spec; your power station is about 22Ah, so a 30Ah battery does have a meaningfully higher capacity.

 

[TabarnaCarl]

@TabarnaCarl, I read the wrong BLUETTI spec; your power station is about 22Ah, so a 30Ah battery does have a meaningfully higher capacity.

Where did you found that ? I couldn't found any info on the ah of my eb3a even in the bluetti website

 

[TabarnaCarl]

A battery isolator won't charge a deep cycle AGM battery optimally, causing shorter battery life. A DC-DC charger is a better solution, but it's typically more expensive and has a slightly larger footprint. A DC-DC charger is required if the second battery is lithium-ion.

Which 30Ah battery fits in the AUX (ESS) battery box? FYI, 30Ah is less than your BLUETTI, which is about 37Ah.

https://a.co/d/856HnHo

 

[THAW]

Where did you found that ? I couldn't found any info on the ah of my eb3a even in the bluetti website

https://www.bluettipower.com/products/bluetti-eb3a-portable-power-station

I converted the 268Wh spec to Ah by dividing by 12V.

 

[THAW]

https://a.co/d/856HnHo

That's a LiFePO4 battery, so you should definitely use a DC-DC charger.

 

[TabarnaCarl]

https://www.bluettipower.com/products/bluetti-eb3a-portable-power-station

I converted the 268Wh spec to Ah by dividing by 12V.

My math wasn't mathing

 

[Ratbert]

That's a LiFePO4 battery, so you should definitely use a DC-DC charger.

I was going to question why someone that's concerned about space and capacity would be looking at an AGM battery. It's good to know a LiFePO4 (possibly?) fits in that small space!

 

[THAW]

I was going to question why someone that's concerned about space and capacity would be looking at an AGM battery. It's good to know a LiFePO4 (possibly?) fits in that small space!

I don't have the inside dimensions of the AUX (ESS) battery box handy, but the AUX14 battery standard is 5.9" L x 3.4" W x 5.7" H whereas the linked 30Ah LiFePO4 battery is 7.2" L x 3.3" W x 6.9" H.

If the 30Ah LiFePO4 doesn't fit in the factory enclosure, there's likely room to strap the battery in the AUX (ESS) battery location without the box (though for safety sake, it might be wise to protect it in some way from potential puncture damage).

Also, I would expect the 30Ah LiFePO4 battery to degrade faster than average due to engine bay heat.

 

[TabarnaCarl]

I don't have the inside dimensions of the AUX (ESS) battery box handy, but the AUX14 battery standard is 5.9" L x 3.4" W x 5.7" H whereas the linked 30Ah LiFePO4 battery is 7.2" L x 3.3" W x 6.9" H.

If the 30Ah LiFePO4 doesn't fit in the factory enclosure, there's likely room to strap the battery in the AUX (ESS) battery location without the box (though for safety sake, it might be wise to protect it in some way from potential puncture damage).

Also, I would expect the 30Ah LiFePO4 battery to degrade faster than average due to engine bay heat.

Well the factory aux battery wasn't strap at all....

 

[Ratbert]

Also, I would expect the 30Ah LiFePO4 battery to degrade faster than average due to engine bay heat.

Those batteries typically have 2 to 5k cycles in them. Degrading one that's only used when overlanding would most likely never be noticed.

 

[THAW]

I measured the inside of my AUX (ESS) battery box at about 6 and-a-quarter inches "long", 3 and-a-half inches "wide", and 6 and-a-half inches high. So, I'm skeptical the Amazon 30Ah LiFePO4 battery will fit it. But in this case, I'd be happy to be proven wrong!

 

[TabarnaCarl]

I measured the inside of my AUX (ESS) battery box at about 6 and-a-quarter inches "long", 3 and-a-half inches "wide", and 6 and-a-half inches high. So, I'm skeptical the Amazon 30Ah LiFePO4 battery will fit it. But in this case, I'd be happy to be proven wrong!

I didn't measure the aux battery box, but I measured my aux battery and dimensions are 5 3/4 x 5 5/8 x 3 3/8...

Been 2-3 years since I did the aux battery delete but I think the battery was a little loose in the box...

Thanks for your info, I might try to find another battery or I'll find a way to make it fit

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