JoeS
Site Moderator
Posts: 4120
Joined: Thu Dec 15, 2011 5:47 am
Location: Silicon Valley, California

Re: 12v Battery - All You Ever Wanted To Know

Sun Oct 03, 2021 7:58 am

stoatwblr wrote:It's extremely harmful to store LiIon in deep discharged state (they occasionally ballon or even catch fire) or keep them float charged - they seem to prefer being stored at about 75-80%...
stoatwblrm, you are correct that we should avoid storing our lithium traction battery at either SoC extreme; however, I believe the recommended storage level for most Lithium chemistries is actually closer to 40%SoC (for example, ref: https://batteryuniversity.com/article/bu-702-how-to-store-batteries). This topic for EV primary batteries has been discussed extensively on just about every EV forum (including this one), so perhaps we should keep this thread focused on our i-MiEV 12v lead-acid battery. Thank you.
EVs: Two '12 Wht/Blu SE Prem., '13 TeslaMS85, three 156v CorbinSparrowsLi(NMC), 24v EcoScoot(LiFePO4)
EV Conversions: 156v '86 Ram PU, 144v '65 Saab96, 48v1kW bike
RIP(2021) ICE: Orig.Owner '67 Saab96V4, '88 IsuzuTrooper; '76 MBZ L206D RHD RV

stoatwblr
Posts: 16
Joined: Tue Sep 28, 2021 12:17 pm

Re: 12v Battery - All You Ever Wanted To Know

Mon Oct 11, 2021 9:20 am

JoeS wrote:This topic for EV primary batteries has been discussed extensively on just about every EV forum (including this one), so perhaps we should keep this thread focused on our i-MiEV 12v lead-acid battery. Thank you.

I'm interested from the POV of replacing the (ancient) 12V FLA in my 2012 imiev with a LiFePO4. I'm in southern UK so severe deep freezing isn't an issue but putting inside the cabin will allow a diesel heater under the snout - as the traction batteries seem to be down to around 60% I can't really afford to lose too much range on a 24 mile daily commute

The attractive part is that fully BMSed 22Ah units seem to only be about 25% more than FLA these days - and potentially small enough that they could share the battery tray with a webasto if heat issues are dealt with

JoeS
Site Moderator
Posts: 4120
Joined: Thu Dec 15, 2011 5:47 am
Location: Silicon Valley, California

Re: 12v Battery - All You Ever Wanted To Know

Mon Oct 11, 2021 2:25 pm

stoatwblr wrote:...I'm interested from the POV of replacing the (ancient) 12V FLA in my 2012 imiev with a LiFePO4...
Nowadays, I think that is a great idea! In the last couple of years there has been an explosion of "12v" LiFePO4 batteries on the market with integral BMS', and the prices continue getting better as the competition heats up. Here in the US, RV'ers, especially, have glommed onto them, appreciating the deeper cycling abilities compared to lead. I have heard glowing reports about, for example, a company called Battle Born and its superb BMS and the excellent matched cells that it uses, although they are rather pricey. (Disclosure: I have no financial interest in this company)

The key is a BMS that can handle a steady-state 14.4vdc (20°C) that the i-MiEV produces when driving and one that will NOT cut out open circuit if it's not happy at the high end. At the voltage low end we don't need to worry unless the dc-dc fails.

Does anyone know what the temperature profile is of the i-MiEV dc-dc, as I would be concerned that at very low temperatures the resulting voltage might be too high for a BMS?

If you can find a nice small battery with the appropriate terminal configuration, go for it! - and do let us know how things turn out.

Slightly off-topic -
I've recently been experimenting with paralleling '12v' LiFePO4 with Gel cells and am in the middle of daily testing using my solar trailer as an energy source and feeding an inverter to run my home refrigerators during daylight hours (long story as to why I would want to do that...). Monitoring the current in both directions for both the Gels and LiFePO4 to see how well they share. So far, so good - the Headway LiFePO4 cells stay wonderfully balanced using a Heltec capacitive balancer, I've limited the Aussie Plasmatronics solar regulator upper voltage to a conservative 13.50vdc (I may go up to 13.60v if all goes well), and the 12.20vdc low voltage shutoff has not happened, yet...
EVs: Two '12 Wht/Blu SE Prem., '13 TeslaMS85, three 156v CorbinSparrowsLi(NMC), 24v EcoScoot(LiFePO4)
EV Conversions: 156v '86 Ram PU, 144v '65 Saab96, 48v1kW bike
RIP(2021) ICE: Orig.Owner '67 Saab96V4, '88 IsuzuTrooper; '76 MBZ L206D RHD RV

barrylevine
Posts: 26
Joined: Fri Jul 01, 2016 11:22 am

Re: 12v Battery - All You Ever Wanted To Know

Mon Nov 15, 2021 1:14 pm

PV1 wrote:Both of my i-MiEVs have this quirk where if the car is locked, and I go to retrieve something out of it with the simple process of unlock doors with key fob, open a door, close it, and lock the car with the fob, I'll have a dead 12 volt battery within a week. If I unlock the doors with the fob, open a door, start the car, shut it off, close the door, and lock it with the fob, the car can sit for a month+ and be able to start without a jump. Whatever drains the battery, having the car fully cycled before locking the doors lets it power down successfully.


I'm in the process of dealing with a what was a dead 12V battery, and I thought it a good idea to check in the forum to learn a few things. I've a 2016 i-MiEV, and have always locked the doors with the fob. Mostly though, not going back to open the car and lock it with the fob again.
Recently, not driving much at all, but occasionally retrieving items from the car and relocking with the fob... and maybe with the i-MiEV sitting undriven for a week or more at a time (and with the original 5-year-old battery as well), this quirk revealed itself. The battery seems to take a charge now though, reads 12.6V on my multimeter.
So, Question 1: Is there any more info on this battery-draining quirk?
Question 2: I've seen some posts here about the relatively easy and longer life i-MiEV 12V batteries have. In my ICE cars, 5 years was pretty much the limit (likely imposed by the need to start an ICE in Boston winter weather). Do the i-MiEV's tend to do better?

Lic
Posts: 104
Joined: Mon Dec 28, 2015 2:11 pm
Location: Canada

Re: 12v Battery - All You Ever Wanted To Know

Fri Nov 19, 2021 10:38 pm

I installed lithium-titanate battery for 12v system. This battery could be charged up to 16v. I am wondering if it possible to charge it up to 15v or even 16v when car is charging main battery and charge it in regular way when car is in ready. I see 2 ways how to do it. First - connect 240v/12v to 16v power supply to charging inlet and to 12v battery. When I will charge car - lithium -titanate will charge too. Second - find out if there is line which measure voltage in 12v line and make car think that voltage of 12v is low (may be drop voltage by 2 diodes) and bypass those diodes when car is in ready. What do you think?

pbui19
Posts: 198
Joined: Tue Jan 07, 2014 12:17 pm

Re: 12v Battery - All You Ever Wanted To Know

Sat Nov 20, 2021 1:52 pm

Lic wrote:I installed lithium-titanate battery for 12v system. This battery could be charged up to 16v. I am wondering if it possible to charge it up to 15v or even 16v when car is charging main battery and charge it in regular way when car is in ready. I see 2 ways how to do it. First - connect 240v/12v to 16v power supply to charging inlet and to 12v battery. When I will charge car - lithium -titanate will charge too. Second - find out if there is line which measure voltage in 12v line and make car think that voltage of 12v is low (may be drop voltage by 2 diodes) and bypass those diodes when car is in ready. What do you think?


had to look up titanate battery. Please share model, price and where it was purchased. What's the goal to get higher than 14.1 charging voltage ? more capacity ?

pbui19
Posts: 198
Joined: Tue Jan 07, 2014 12:17 pm

Re: 12v Battery - All You Ever Wanted To Know

Sat Nov 20, 2021 2:04 pm

barrylevine wrote: So, Question 1: Is there any more info on this battery-draining quirk?
Question 2: I've seen some posts here about the relatively easy and longer life i-MiEV 12V batteries have. In my ICE cars, 5 years was pretty much the limit (likely imposed by the need to start an ICE in Boston winter weather). Do the i-MiEV's tend to do better?


we learned in the early days with our 2014 to always lock with pushing the lock button or turning the mechanical key, the 12-v was drained several occasion locking with the fob. So it's a habit now, I thought it had something to do with arming the alarm system.

I have one of those dash-board solar panel charging the iMiev, but then have to be sure to park in the sun. The 12v in the i definitely has an easier life: no cranking, no high temperature. But being lead, it still die. Replaced mine, once so far, with a cheapy HarborFreight SLA (~$60 ?)

barrylevine
Posts: 26
Joined: Fri Jul 01, 2016 11:22 am

Re: 12v Battery - All You Ever Wanted To Know

Sat Nov 20, 2021 4:52 pm

Thanks for your reply. I've been getting in the habit now of using the door lock button. But I hadn't considered using the door key. However, being a bit absent minded at times, I think now it would be better to habitually use the key (then there's no chance of inadvertently locking them in the car!)
Going to wait on the battery - new ones are rather pricey, and it seems to be holding charge quite well, reading 12.5V if sitting for a few days off the car charger. (But wait until the zero degree mornings!) Harbor Freight doesn't seem to be carrying anything that looks like a possible cheapo replacement these days. I'm keeping an eye open also for a low-priced Miata battery, since those will fit, albeit with lower height.

Lic
Posts: 104
Joined: Mon Dec 28, 2015 2:11 pm
Location: Canada

Re: 12v Battery - All You Ever Wanted To Know

Sun Nov 21, 2021 6:19 pm

pbui19 wrote:
Lic wrote:I installed lithium-titanate battery for 12v system. This battery could be charged up to 16v. I am wondering if it possible to charge it up to 15v or even 16v when car is charging main battery and charge it in regular way when car is in ready. I see 2 ways how to do it. First - connect 240v/12v to 16v power supply to charging inlet and to 12v battery. When I will charge car - lithium -titanate will charge too. Second - find out if there is line which measure voltage in 12v line and make car think that voltage of 12v is low (may be drop voltage by 2 diodes) and bypass those diodes when car is in ready. What do you think?


had to look up titanate battery. Please share model, price and where it was purchased. What's the goal to get higher than 14.1 charging voltage ? more capacity ?

I used toshiba scib battery modules from honda fit electric. I bought it used from ebay. Goal is to save main battery energy. If you will have 15v in 12v system dc-dc will not feed 12v system at all.

PV1
Site Moderator
Posts: 3146
Joined: Fri Apr 27, 2012 4:22 pm
Location: Pittsburgh, PA
Contact: Website

Re: 12v Battery - All You Ever Wanted To Know

Thu Nov 25, 2021 9:02 am

barrylevine wrote: So, Question 1: Is there any more info on this battery-draining quirk?
Question 2: I've seen some posts here about the relatively easy and longer life i-MiEV 12V batteries have. In my ICE cars, 5 years was pretty much the limit (likely imposed by the need to start an ICE in Boston winter weather). Do the i-MiEV's tend to do better?

Not that i have. Actually, after replacing the 12 volt batteries in both cars, I haven't really seen this return. Both cars have been sitting a lot lately and both started right up when needed.

I forget how long mine lasted, but I got at least 7 years out of them. My old Cavalier battery lasted 10 years.
"Bear" - 2012 Diamond White Pearl ES with QC
"Koorz" - 2012 Cool Silver Metallic ES with QC
"Photon" - 2017 Bolt EV LT in Orange with QC
2018 Tesla Model 3, LR AWD, MSM
Solar-powered since 10/10/2013

Return to “Batteries and Battery Management”