The 12V battery is not used to start the engine so you don't need a high cranking power. What it mostly needs to do is to provide enough power to the main contactor to connect the high voltage to the rest of the system and each relay coil uses less than one amp (DC resistance is in the 20 ohm region). So as long as the 12V battery can provide a couple of amps you are good.
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Bear in mind too that a lithium battery can sustain a much deeper AH drawdown than a lead battery, so it isn't unusual to use a lower AH rated lithium battery to replace a lead one. For UPS's a 17AH lead battery can be usefully replaced by a 10AH lithium for the same runtime expectancy, since the lad battery voltage will have started to tail off once past the 50% capacity remaining level.
So using a 20AH lithium replacement for the OEM 40AH AGM doesn't sound unreasonable.
A more critical factor however is whether the BMS in the lithium battery can service the peak current demand from the load else the BMS could abruptly shut off the output so that's worth checking on batteries you want to consider using.
So using a 20AH lithium replacement for the OEM 40AH AGM doesn't sound unreasonable.
A more critical factor however is whether the BMS in the lithium battery can service the peak current demand from the load else the BMS could abruptly shut off the output so that's worth checking on batteries you want to consider using.
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Thanks. Similar, but here’s what comes up for my year.
https://www.oreillyauto.com/detail/c/acdelco/acdelco-battery/acd0/b24ragm
But still, the positive terminal post is on the wrong side, left when it’s supposed to be right. Yours has the positive terminal postOn the correct side, but more capacity than my car needs. Should I go with yours?
Thanks. If I’m near pepboys I will check it out.
20AH can provide 1 amp for 20 hours or 2 amps for 10 hours so it should be plenty. We hardly drive the car for more than 10 hours continuously for the last 6 years except once from SF to LA for about 6 hours.
michael8554
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I didn't replace the original 12V battery on my 2014 until 2023, after I'd realised how crucial it was to starting the car.
It had only done 31K miles and was reading 12.14V off-load.
So is it the age, the mileage, or the number of starts that matter ?
I replaced with:
"We hardly drive the car for more than 10 hours continuously for the last 6 years "
Once the PHEV is ON the 12V is charged from the traction battery, so is not being drained as you drive.
You can check if that is happening by measuring the volts when ON, should go up to approx 14v.
It had only done 31K miles and was reading 12.14V off-load.
So is it the age, the mileage, or the number of starts that matter ?
I replaced with:
Optima Yellow Top Battery YTS 2.7 R (Reversed) (8073-176) (D51R) YTS2.7R YTR2.7 AGM
Cost £140"We hardly drive the car for more than 10 hours continuously for the last 6 years "
Once the PHEV is ON the 12V is charged from the traction battery, so is not being drained as you drive.
You can check if that is happening by measuring the volts when ON, should go up to approx 14v.
I replaced the one in my 2019 early this year with the yellow top also. Original battery was regularly reading 11.8-9v in the car. Being a used vehicle and not knowing the history of use I figured better do that than find one cold night you can fire up. Been there with a regular car years ago, not fun at 2AM and parked with limited access to the engine bay.
Turns out tho that after putting that OEM battery on a smart charger and running a few regen cycles, it now hold up voltage just fine, but its just a spare now if I need it for anything.
I expect what kills these is the light use so they sulphate over time (esp if run down listening to the radio etc) and/or perhaps the electrolyte gets weak.
Funny thing tho is the new yellow top will also read down at 11.9v if I've not used the car for a week so for me that shows the daily top-up charge isn't keeping up with whatever is draining it.
When running the charge voltage hist 14.4-14.7v and once the battery is charged that'll drop down to the 13.2v range, at least that's what I've observed on the USB/voltmeter I installed in the dash.
The 12v Li battery read 14.4 V in my voltage meter at the cigarette lighter plug while running. Idle at about 12.4 to 12.6V.
michael8554
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I've just read an article on the PHEV that suggests that Lithium 12V Aux Battery replacements can fail at sub-freezing temperatures, leaving the car stranded due to neither the EV or ICE systems being able to power up.
Because of this some Lithium AGM replacements have a built in heater, though it's not clear where the power for that comes from !
Because of this some Lithium AGM replacements have a built in heater, though it's not clear where the power for that comes from !
The lithium 12v battery is supposed to start even at -20 degree Celsius versus lead acid or AGM battery.
michael8554
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The problem is that "Low Temp" Lithium batteries can work down to -20.
But most become troublesome below 32F freezing point.
If the spec isn't checked you have a problem Houston.
But most become troublesome below 32F freezing point.
If the spec isn't checked you have a problem Houston.
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No problem for 2 years so far, freezing or not freezing. if one didn't check before buying, it will be problems for any battery. Al those Tesla's lithium battery running cars would have been dead.
