15.2v charging seems a bit high while driving

[mav47]

The BMS determines when the 12V Battery is charging. It is not a constantly charging.

When you see the 15.2V you cannot make the assumption that the BMS is charging the battery with that voltage.

I am not making that assumption: I measured at the battery terminals and compared it to the reading of my in-dash voltage meter in the DC plug. The difference between both readings never exceeded 0.1V, so my dash voltage meter reading equals battery terminal voltage.

And to me this makes sense: the 12V battery is directly tied into the 12V system in the vehicle and the BMS appears to set the system (=charging) voltage coming from the DC-DC converter. (or the alternator on ICE vehicles).

The BMS keeps track of the battery's State of Charge (SOC) by reading current IN vs current OUT through the current sensor that connects the battery negative terminal to the ground. Which is why you need to "reset" the BMS when you install a new battery. I understand the default SOC target to be between 60 and 80%.

In the end, the BMS simply controls charging current into the battery by changing the system voltage with a likely cap somewhere in the mid 15V range.

Once the SOC target is reached, the BMS will lower the system voltage so the battery does not take charging current anymore.

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[mav47]

Mav47, keep us posted on how the AMG battery does. I plan to replace my hybrid battery with a AMG when needed. Can you share the AMG battery model you purchased?

In these forums I did not find a single "GROUP TYPE" for the proper battery in the Maverick Hybrid. Various owners put an H5 type battery in their Hybrid, but had to cut off two tabs that keep the battery in place. I didn't like that idea as I feel the battery should be safely held in case of collisions, etc.

Someone in this forum (sorry, cannot find the post, otherwise I'd link it) posted a link to this website, which was helpful.

As it turns out, after measuring the proper battery size for the Maverick Hybrid is:

GROUP 140R (=BCI code, most common in US)
LN1 (seems to be a Yuasa Japanese code)
H4 (DIN code, so European designation)

And it bolts right in.

I found that 50Ah AGM versions of this battery type listed around 570CCA and 80RC (=reserve capacity, which is likely more important for the hybrid than CCA)

Compare that to the OEM flooded chemistry battery that came with the truck: 45Ah, 65RC.

I bought one of these Group 140R/LN1/H4 UPLus AGM batteries on Amazon: https://www.amazon.com/dp/B0CM3GZWXX?th=1, but do note that they only showed Qty 20 in stock and now they don't show H4 as available anymore (only H5, H6 are currently listed, but that may change again). Was a bit of a gamble, but the company behind these batteries is a big one so I thought I'd try it for $134 minus a 10% coupon and including shipping. Most all these AGM batteries are made overseas anyways, I think you can have just as much good or bad luck with a better known brand one.

That UPlus battery came shipped in GREAT packaging, well protected and seems well made. I think it will be fine.

An alternative I looked at is that LN1 AC Delco that was listed above by @uga , also at RockAuto https://www.rockauto.com/en/moreinfo.php?pk=8878472

I think you likely cannot go wrong as long as you buy a battery of this group 140R size and as long at it is an AGM battery.

I'll post if my luck with this UPlus battery changes

 

[AzureBlueBill]

Hook up a volt meter to almost any properly operating 12 volt car/truck. You'll usually see around 15 volts when it is running. Been this way almost forever.

 

[Builder]

Great info and interesting read; puts my mind somewhat at ease regarding the 15.2v read. I’ll stick with the OEM 12v until I can’t. I’ll probably put an AGM in sooner rather than later based on the experiences within the MTC. This whole 12v battery issue is frustrating and should have been addressed by Ford by now. Thanks for all the input.

 

[Darnon]

I am not making that assumption: I measured at the battery terminals and compared it to the reading of my in-dash voltage meter in the DC plug. The difference between both readings never exceeded 0.1V, so my dash voltage meter reading equals battery terminal voltage.

And to me this makes sense: the 12V battery is directly tied into the 12V system in the vehicle and the BMS appears to set the system (=charging) voltage coming from the DC-DC converter. (or the alternator on ICE vehicles).

Yeah, there's nothing between the DC-DC converter and the battery that'd be further controlling the voltage/current. It's literally DC-DC converter > cable > 300A fuse > underhood junction box bus bar > battery cable (infamous for the soldered terminal failing) > 200A fuse at batt+ terminal > battery.

Also I know it's getting 15+ volts at the battery because that's where I tie in my amplifiers and had trouble with some going into overvoltage protection. Strangely, opening a door triggers it dropping the voltage commanded down.

Another quirk I noticed recently is that Key On but not Ready ('started') the DC-DC converter does seem to output some voltage; was seeing about 12.9V. I was under the impression that the HV contactor would be open still in that state, unless it's utilizing power from the pre-charge circuit?

 

[mav47]

Just spotted the same exact battery as that UPlus, but now with a different brand name. Ships from the same seller too:

MARXON Group 140R H4 LN1 Start and Stop Car Battery 12v 50AH 570CCA AGM BCI140R Maintenance Free Automotive Replacement Batteries https://a.co/d/i3N9F0J

Edit: now seems sold out too.

 

[MakinDoForNow]

Yeah, there's nothing between the DC-DC converter and the battery that'd be further controlling the voltage/current. It's literally DC-DC converter > cable > 300A fuse > underhood junction box bus bar > battery cable (infamous for the soldered terminal failing) > 200A fuse at batt+ terminal > battery.

Also I know it's getting 15+ volts at the battery because that's where I tie in my amplifiers and had trouble with some going into overvoltage protection. Strangely, opening a door triggers it dropping the voltage commanded down.

Another quirk I noticed recently is that Key On but not Ready ('started') the DC-DC converter does seem to output some voltage; was seeing about 12.9V. I was under the impression that the HV contactor would be open still in that state, unless it's utilizing power from the pre-charge circuit?

With key on but not Ready the contactor is closed and DCDC convertor is providing current (a screen may pop up showing extended auxillary power active or something similar) until the HVB SOC drops to 30-32% (don't remember which). It's possible the 12v time delay will turn off the auxillary power before the HVB drops to the cut off voltage.

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