# 7 TH 12v Battery **URL:** \ **Category:** GEM Forum\ **Created:** [January 31, 2021, 12:23am UTC](https://community.electricforum.com/t/7-th-12v-battery/20736 "2021-01-31T00:23:43Z")\ **Posts on this page:** 14\ **Page:** 1
**Author:** ![jm1361](https://avatars.discourse-cdn.com/v4/letter/j/7ea924/32.png) [@jm1361](https://community.electricforum.com/u/jm1361)\ **Post date:** [January 31, 2021, 12:23am UTC](https://community.electricforum.com/t/7-th-12v-battery/20736/1 "2021-01-31T00:23:43Z")
Can we add a battery between controller and motor so only motor sees extra voltage or is it better between contactor and controller then the controller also sees extra volts any want to weigh in on this before I try it and damage something Thanks for your input ---
**Author:** ![Inwo](https://yyz2.discourse-cdn.com/flex030/user_avatar/community.electricforum.com/inwo/32/1067_2.png) [@Inwo](https://community.electricforum.com/u/Inwo)\ **Post date:** [January 31, 2021, 2:00am UTC](https://community.electricforum.com/t/7-th-12v-battery/20736/2 "2021-01-31T02:00:26Z")
Between contactor and controller. The controller output is chopped. Ie. Pwm. ---
**Author:** ![jm1361](https://avatars.discourse-cdn.com/v4/letter/j/7ea924/32.png) [@jm1361](https://community.electricforum.com/u/jm1361)\ **Post date:** [January 31, 2021, 3:20am UTC](https://community.electricforum.com/t/7-th-12v-battery/20736/3 "2021-01-31T03:20:11Z")
thanks for response I don’t know what you mean by chopped. Is there a down side putting it between controller and motor ---
**Author:** ![JarJarJava](https://yyz2.discourse-cdn.com/flex030/user_avatar/community.electricforum.com/jarjarjava/32/15158_2.png) [@JarJarJava](https://community.electricforum.com/u/JarJarJava)\ **Post date:** [January 31, 2021, 8:15am UTC](https://community.electricforum.com/t/7-th-12v-battery/20736/4 "2021-01-31T08:15:20Z")
About a year and half ago I became the first person AFAI&DK to test this out for Dave (@Inwo ). He had an old idea on sticking an extra battery between the contactor and the controller and it sounded interesting to me. As a bonus it’s also been a test of a mixed battery system as the GEM it’s installed in has 6 FLA mains and a 4s lifepo pack as the extra battery. It’s been rock solid. Seriously, it’s been flawless. I’ve put a bit shy of 4k miles on it since installing that pack. Here’s the install and testing thread: > [@LiFePo4 "7th battery" on a lead bottom GEM](https://community.electricforum.com/t/lifepo4-7th-battery-on-a-lead-bottom-gem/16591): > > This was an idea that Dave @Inwo came up with at some point in the past and I was the first ̶i̶d̶i̶o̶t̶ scientific pioneer willing to test it… … Adding an extra battery after the main contactor, so that only the high amperage terminals on the controller see the extra voltage. Translation, no voltage shunt needed for control power and that somehow changes how the controller sees things and the car performs and I’m gonna let Dave explain that part because he’s an electronics genius and I just f… ---
**Author:** ![Inwo](https://yyz2.discourse-cdn.com/flex030/user_avatar/community.electricforum.com/inwo/32/1067_2.png) [@Inwo](https://community.electricforum.com/u/Inwo)\ **Post date:** [January 31, 2021, 1:29pm UTC](https://community.electricforum.com/t/7-th-12v-battery/20736/5 "2021-01-31T13:29:13Z")
Tnx for the update. I still have a few LiFePo4 cells on the shelf and enough balancers and chargers to build kits. To be honest, forgot all about this, and can’t recall if anyone else followed you. ---
**Author:** ![Inwo](https://yyz2.discourse-cdn.com/flex030/user_avatar/community.electricforum.com/inwo/32/1067_2.png) [@Inwo](https://community.electricforum.com/u/Inwo)\ **Post date:** [January 31, 2021, 1:41pm UTC](https://community.electricforum.com/t/7-th-12v-battery/20736/6 "2021-01-31T13:41:46Z")
> [@jm1361](#): > > what you mean by chopped PWM is the way a controller controls the average voltage and current to the motor. Originally the only way was to put a resistor in series with motor. This was very inefficient and used as much battery capacity as the motor. Now with fast solid state switches, mosfets usually, the controller can turn the motor off and on 1,000s of times per second. The relation of the on time versus off time sets motor speed. Picture turning a light switch on and off so fast that the strobing isn’t noticed. In fact that’s what dimmer switches do with a much simpler device. A triac triggers 120 times a second at a certain point in the rising and falling 60hz sine wave. ![image](https://canada1.discourse-cdn.com/flex030/uploads/electricforum/original/2X/3/31c335433a6432fca43af0455d070dbc720d34d7.png) ---
**Author:** ![jm1361](https://avatars.discourse-cdn.com/v4/letter/j/7ea924/32.png) [@jm1361](https://community.electricforum.com/u/jm1361)\ **Post date:** [January 31, 2021, 1:56pm UTC](https://community.electricforum.com/t/7-th-12v-battery/20736/7 "2021-01-31T13:56:09Z")
Thanks for explanation I would be willing to be the second what does this kit contain and what will it coast me { dimensions ---
**Author:** ![Inwo](https://yyz2.discourse-cdn.com/flex030/user_avatar/community.electricforum.com/inwo/32/1067_2.png) [@Inwo](https://community.electricforum.com/u/Inwo)\ **Post date:** [January 31, 2021, 6:48pm UTC](https://community.electricforum.com/t/7-th-12v-battery/20736/8 "2021-01-31T18:48:48Z")
Depends on what you need. Batteries x 4 for 12v = $200 I’ll throw in the balance boards. 12v charger $100. You will need to clamp the batteries together as they need pressure end to end of the 4 pack, to keep them from expanding. Else for $50 I’ll band them and test charge them. $50 S&H So, $350 or $400 $200 for just the 4 cells. + S+H ---
**Author:** ![JarJarJava](https://yyz2.discourse-cdn.com/flex030/user_avatar/community.electricforum.com/jarjarjava/32/15158_2.png) [@JarJarJava](https://community.electricforum.com/u/JarJarJava)\ **Post date:** [February 1, 2021, 4:08pm UTC](https://community.electricforum.com/t/7-th-12v-battery/20736/9 "2021-02-01T16:08:22Z")
I haven’t heard of anyone else doing it the way we did Dave. I wonder if 6-8 of the green cells would fit in a power wheels. Probably better to get something with more density, space is kind of at a premium. ---
**Author:** ![Inwo](https://yyz2.discourse-cdn.com/flex030/user_avatar/community.electricforum.com/inwo/32/1067_2.png) [@Inwo](https://community.electricforum.com/u/Inwo)\ **Post date:** [February 1, 2021, 5:52pm UTC](https://community.electricforum.com/t/7-th-12v-battery/20736/10 "2021-02-01T17:52:23Z")
4 does 12v. 8s for 24v. ---
**Author:** ![Old\_Houseboater](https://yyz2.discourse-cdn.com/flex030/user_avatar/community.electricforum.com/old_houseboater/32/544_2.png) [@Old\_Houseboater](https://community.electricforum.com/u/Old_Houseboater)\ **Post date:** [February 1, 2021, 10:35pm UTC](https://community.electricforum.com/t/7-th-12v-battery/20736/11 "2021-02-01T22:35:24Z")
This works good for me > [@84 volt instalation in pictures](https://community.electricforum.com/t/84-volt-instalation-in-pictures/18970): > > 84 volt install in my 2000 e825 4 seater. What say you? ---
**Author:** ![jm1361](https://avatars.discourse-cdn.com/v4/letter/j/7ea924/32.png) [@jm1361](https://community.electricforum.com/u/jm1361)\ **Post date:** [March 2, 2021, 12:53pm UTC](https://community.electricforum.com/t/7-th-12v-battery/20736/12 "2021-03-02T12:53:10Z")
Finally got around to trying out INWO idea using materials on hand, have to say he is the man Added 7th T1275 Battery as suggested to my 2015 E2 I now get 2.5 miles per bar at 33 mph with quick response. Noticed a sweat burnt odder can’t tell where it is coming from could it be from Battery gasses ---
**Author:** ![JarJarJava](https://yyz2.discourse-cdn.com/flex030/user_avatar/community.electricforum.com/jarjarjava/32/15158_2.png) [@JarJarJava](https://community.electricforum.com/u/JarJarJava)\ **Post date:** [March 2, 2021, 3:27pm UTC](https://community.electricforum.com/t/7-th-12v-battery/20736/13 "2021-03-02T15:27:10Z")
Mmmm… love a good car-bq… Start with the motor, see if the smell is coming from there. Could be oil and grime burning off. It’s not uncommon for the transmission seal to leak a bit. ---
**Author:** ![jm1361](https://avatars.discourse-cdn.com/v4/letter/j/7ea924/32.png) [@jm1361](https://community.electricforum.com/u/jm1361)\ **Post date:** [March 2, 2021, 10:49pm UTC](https://community.electricforum.com/t/7-th-12v-battery/20736/14 "2021-03-02T22:49:12Z")
ok found the problem unrelated to added voltage seems bad connection at 250A fuse between bat 3 and bat 4