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Discussion Starter · #1 ·
My 12v regular stock location starting battery went bad. I see no reason to replace it with a 50+lbs starting battery since its no longer starting an ICE. Would a small ATV, lawnmower, or Marine deep cycle battery be a better choice for running my lights and other onboard 12v stuff? They are 15lbs instead of 65.

Worst case it would be running:
-Headlights
-gauges
-blower motor for heat and AC
-AC condesner/radiator fan
-radio

Couldn't be any more than 50amps if I had everything on which probably wouldnt happen any way.

Anyone had luck using one of these style batteries? Any size recommendations?

Thanks
 

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My 12v regular stock location starting battery went bad. I see no reason to replace it with a 50+lbs starting battery since its no longer starting an ICE. Would a small ATV, lawnmower, or Marine deep cycle battery be a better choice for running my lights and other onboard 12v stuff? They are 15lbs instead of 65.

Worst case it would be running:
-Headlights
-gauges
-blower motor for heat and AC
-AC condesner/radiator fan
-radio

Couldn't be any more than 50amps if I had everything on which probably wouldnt happen any way.

Anyone had luck using one of these style batteries? Any size recommendations?

Thanks
Since my car is lithium powered I did the same for the starting battery... I used a 4S3P headway pack because I need some extra power for the stereo. However you could probably get by with a 4S1P pack if you have a dc/dc converter. It cost more than a LA battery but it's much lighter and should outlast the vehicle.

 

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One option I like is the Zappy scooter size battery. It is a common AGM battery used in uninterruptible power supplies and alarm system. A couple of common part numbers are UB12220 and UB12180 (18 and 22 amp hour versions of this 12v battery.) They have a footprint of about 7 inches by 3 inches and stand a little less than 7 inches tall. They are generally available for $40 to $50.
 

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Discussion Starter · #4 ·
The lithium cells look pretty cool but I spent all of my cash just buying the ev so the small $40 agm is probably a better choice for now. Its too early for me to get addicted to lithium.

thanks
 

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Discussion Starter · #6 ·
they sure did everything they could to make that look like an engine block. I guess they didn't the public to panic when they opened the hood.

I think I may have found what killed the battery. There is a light on the dash that comes on when the power cord is plugged in. I bet that bulb is draining the 12v battery when the traction pack is plugged in charging. The headlights seemed a little dim to me like the 12v was in bad shape. But I haven't had the car for long and its my first EV so I had nothing to compare it to.

Probably should get a cheap trickle charger to keep the 12v battery full when charging the 144v pack. That would be way better/safer than having the DC to DC converter on while charging correct?
 

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This is an issue I am grappling with right now.

dc-dc on while charging or separate 12v charger for aux batt?

I think I have settled on small aux smart charger.

Good idea?

-I should add the reasoning is that the power used by the dc-dc might keep the charger on instead of letting it shut off.
 

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Discussion Starter · #8 ·
Looking around at the small AGMs for scooters. I'm finding that the 40ah batteries are about 25lbs. The smallest marine starting/deep cycle batteries are about 40lbs.

If I am drawing an average of 35amps with a 30amp DC to DC converter helping out, would I be asking too much from a 40ah AGM?

I dont want to murder a small $80 batt or my DC converter just to save 15lbs.
 

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I run my DC to DC converter all the time but you do need to consider your charger before going that route. It is possible for the DC to DC to interfere with charger shutdown, if the charger is designed to shut off due to very low current at the finish voltage.

Since my Manzanita Micro PFC shuts down 1 hour after reaching target voltage (based on time at finish voltage, not current) leaving the DC to DC on doesn't cause any interference.

I still recommend a small 12 volt back-up battery. If the DC to DC converter fails and you don't have one everything will shut down instantly, even your lighting.
 

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If I am drawing an average of 35amps with a 30amp DC to DC converter helping out, would I be asking too much from a 40ah AGM?
How could you possibly pull 35 amps??

Are you running air conditioning?

Here are amp loads as tested by somebody from a 1980 bmw, so they should be somewhat representative of the average car on a dark rainy night:

Park and tail Lights .... 2.1 A
Headlight Low Beam ... 10.4 A (Single Headlights 50/55 Watt Halogen)
Headlight High Beam ... 10.8 A ( " " " " )
Heater fan ............... 4.5/6.2/8 A (speeds 1,2 and 3)
Wipers .... 3.5 - 4.7 A (more current wiping one direction than the other!)

With everything on high its around 25A. This still leaves another 5amps for the radio, cooling pump, vacuum pump, etc. Led lights can help a bit, but you can see the running lights only pull 2A. Led headlights would do a lot.

Obviously, the radio can be turned off and the fan down to low or med.

Lights, wipers, and fan on low is 21amps.
 

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Discussion Starter · #11 ·
I found similar numbers and rounded up to be safe. The car does have AC with a pretty large electric fan for the AC condenser. I figured I would use 35amps as a good safe estimate. Its probably not near that on a regular basis.
 

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Looking at the new Nissan Leaf they seem to have the same problem with suppling heavy dc start up loads
I would think with a 24 kWh pack that it would have no problems with high loads assuming that it has even a halfway decent 5c discharge.

On a related note, what kind of amps does the alternator of a typical small car put outr. I think converting to a lithium pack would be cool, discharge would be a piece of cake given the huge selection of 20C+ packs, but charging since you usually can't do over 2C would be an issue.
 

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I found similar numbers and rounded up to be safe. The car does have AC with a pretty large electric fan for the AC condenser. I figured I would use 35amps as a good safe estimate. Its probably not near that on a regular basis.
I believe in rounding up -to a point.

It is highly unlikely you will run the air-conditioning AND the wipers AND the lights at the same time.

Hot day: air conditioning, no lights or wipers.
Dry night: lights only.
Wet night: lights, wipers, fan, no air conditioning.

If you want to be sure, you can put an amp meter on the circuits and see what they draw.
 
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