12v battery drain question

[justinwvu]

I experienced the low state of charge warning on my 2021 F150 lariat powerboost last month. I researched and found through this forum that it was a common problem.

I bought the OBDlink MX+ and found my charge was about 30%, I tried some long drives, leaving it running with fan on 5 and could only get up to the mid 30s. I ended up using a 6A trickle charger for about 4 hours (unfortunately connected straight to the negative terminal and not on the other side of the BMS monitor) and the next day the OBD showed no changed in my state of charge (Likely due to the error in how I had attached to the wrong side of the BMS monitor) I did some more research, charged again for about 5 hours with the same 6amp trickle charge until the charger showed fully charged - this time on the vehicle side of the BMS monitor and my OBD showed 65% charged (Likely didn’t show 100% due to my error charging the previous day). Anyway, after sitting overnight battery was back down to around 40% after being 65% so i decided the battery was on its way out and ordered a replacement.

I replaced with a X2 https://www.batteriesplus.com/produ...WgjP2N6NqDP_lD-xLh3UWwE7D7AAUNevhZKpRaV9Ut_g2 battery.

I did the BMS reset procedure (high beams 5x, then brake 3x) and it showed 90% charged so i thought all was good yesterday.

Today, i get in my truck and it is already showing the charge is down to 78%. What gives? Is my truck doing something weird and draining my batteries or is this a normal level of drop for a brand new battery? Truck was sitting in my garage since yesterday around 40 degrees in the garage.

Here is a photo of my OBDlink app just a bit ago after I did a short errand.

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[Gros Ventre]

You still on the OEM battery?

 

[Je1279]

I experienced the low state of charge warning on my 2021 F150 lariat powerboost last month. I researched and found through this forum that it was a common problem.

I bought the OBDlink MX+ and found my charge was about 30%, I tried some long drives, leaving it running with fan on 5 and could only get up to the mid 30s. I ended up using a 6A trickle charger for about 4 hours (unfortunately connected straight to the negative terminal and not on the other side of the BMS monitor) and the next day the OBD showed no changed in my state of charge (Likely due to the error in how I had attached to the wrong side of the BMS monitor) I did some more research, charged again for about 5 hours with the same 6amp trickle charge until the charger showed fully charged - this time on the vehicle side of the BMS monitor and my OBD showed 65% charged (Likely didn’t show 100% due to my error charging the previous day). Anyway, after sitting overnight battery was back down to around 40% after being 65% so i decided the battery was on its way out and ordered a replacement.

I replaced with a X2 https://www.batteriesplus.com/produ...WgjP2N6NqDP_lD-xLh3UWwE7D7AAUNevhZKpRaV9Ut_g2 battery.

I did the BMS reset procedure (high beams 5x, then brake 3x) and it showed 90% charged so i thought all was good yesterday.

Today, i get in my truck and it is already showing the charge is down to 78%. What gives? Is my truck doing something weird and draining my batteries or is this a normal level of drop for a brand new battery? Truck was sitting in my garage since yesterday around 40 degrees in the garage.

Here is a photo of my OBDlink app just a bit ago after I did a short errand.

I replaced my factory battery with a freshly charged EverStart Platinum AGM H7 a couple weeks ago. I don't pay attention to the state of charge so I can't help you there, but I haven't received a single low battery notification from FordPass since the change (and it's been in the teens, 20's and low 30's here). Did you receive the recent software update that modified the battery charging strategy?

 

[justinwvu]

I replaced my factory battery with a freshly charged EverStart Platinum AGM H7 a couple weeks ago. I don't pay attention to the state of charge so I can't help you there, but I haven't received a single low battery notification from FordPass since the change (and it's been in the teens, 20's and low 30's here). Did you receive the recent software update that modified the battery charging strategy?

Pretty sure that my truck is all up-to-date on software

 

[justinwvu]

You still on the OEM battery?

No, I replaced the battery yesterday, there’s a link in my initial post.

 

[Je1279]

Pretty sure that my truck is all up-to-date on software

I received that update the day after I installed the new battery. Because of this, I'm not sure which (or a combination of the two) made the difference, but I was previously receiving the low battery notification every 2-3 days. I would try charging the new battery up to 100% with your charger and resetting the BMS one more time after that to see if it makes any difference.

 

[Gros Ventre]

No, I replaced the battery yesterday, there’s a link in my initial post.

K, follow things for a bit and see what happens. My take is problems will disappear.Keep things posted.

 

[justinwvu]

K, follow things for a bit and see what happens. My take is problems will disappear.Keep things posted.

Yeah, after posting this thread I was thinking that it’s possible the BMS just had to update itself for the new battery and perhaps the 90% that it gave me right after the install was just a default reading for a new battery install. As I understand the BMS system- it will update itself after sitting idle for eight hours

 

[Baz]

I had my main battery replaced under warranty about 6 months ago and with the temps dropping I have noticed the approach detection (lighting & running board deploying) are not as sensitive. So I did hook up my charger and everything returned to normal.

I am wondering if it has to do with the auxiliary battery SOC....
I know that with those batteries connected in parallel they don't technically charge one another but will equalize...

Here is the procedure from the workshop manual to check the aux battery.... my dealer will be checking both of mine next week.

 

[justinwvu]

I kind of forgot about the auxiliary battery. I have no idea how it interacts with the main battery so maybe you’re right.

I have not investigated it in anyway

are the auxiliary batteries the exactly the same as the one under the hood? If so, maybe I should just replace that stupid thing as well.

The longer I own this powerboost the more of a pain its becoming.

 

[Baz]

I kind of forgot about the auxiliary battery. I have no idea how it interacts with the main battery so maybe you’re right.

I have not investigated it in anyway

are the auxiliary batteries the exactly the same as the one under the hood? If so, maybe I should just replace that stupid thing as well.

The longer I own this powerboost the more of a pain its becoming.

No, the aux battery is not the same as the underhood battery... it is a 7.5 ah battery

There is a lot of info on the forum about how the powerboosts multiple batteries & BMS operate..

 

[justinwvu]

No, the aux battery is not the same as the underhood battery... it is a 7.5 ah battery

There is a lot of info on the forum about how the powerboosts multiple batteries & BMS operate..

I’m sure there is, I’ll have to research that a bit.

 

[Gros Ventre]

I’m sure there is, I’ll have to research that a bit.

The Aux battery is there to support truck electronics during the start cycle. There is a contactor that separates the start system, Main battery, starter and a few others from the rest of the truck's electrical system. This is because the battery voltage droops to as low as 10.5VDC during starting. This happens because of the high current draw on the battery and represents the I^2*R losses inside the battery. This is a normal characteristic of any battery.When starting is completed the contactor closes and the two batteries are paralleled. When paralleled the two batteries will quickly come to an equal terminal voltage (state of charge) condition. After that they share loads, if necessary, in proportion to their amp-hour capacity.

 

[justinwvu]

Just an update to my post. I got in my truck this morning to take kids to school and battery had gone from about 77% to 74%. I had gotten in and out of my truck a couple times to get some things out of it so the lights came on so that 3% drop seems to make sense. I drove and let the truck idle while I ran some errands, and the battery went from about 74 to 79% by the end of my hour of driving/idling. (Man, I really wish I could disable the two horn beeps when I leave the truck running and take my keys with me.)

I did observe that the fan speed on 5 seems to have no effect on my amperage to the battery. If I had my fan on auto, it did not seem to matter as I usually was getting either 5 or 7 A in OBDLink with either fan setting.

here is my OBDLink at the end of my morning drive.


I suspect the initial drop in my battery state of charge on day one was the BMS system recalibrating and perhaps taking into account the auxiliary battery. I’ll continue to monitor.

 

[Baz]

Just an update to my post. I got in my truck this morning to take kids to school and battery had gone from about 77% to 74%. I had gotten in and out of my truck a couple times to get some things out of it so the lights came on so that 3% drop seems to make sense. I drove and let the truck idle while I ran some errands, and the battery went from about 74 to 79% by the end of my hour of driving/idling. (Man, I really wish I could disable the two horn beeps when I leave the truck running and take my keys with me.)

I did observe that the fan speed on 5 seems to have no effect on my amperage to the battery. If I had my fan on auto, it did not seem to matter as I usually was getting either 5 or 7 A in OBDLink with either fan setting.

here is my OBDLink at the end of my morning drive.


I suspect the initial drop in my battery state of charge on day one was the BMS system recalibrating and perhaps taking into account the auxiliary battery. I’ll continue to monitor.

You can get rid of the two horn honk when getting out of the truck with the FOB... Changes can be made with Forscan... very easy...

Do you have the OBDlink EX or MX+?

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