# Iota DC/DC converter shorting plug mod



## F16bmathis (Jun 6, 2008)

I found I could cut the green wire on the Iota 45 shorting plug and use a 12V relay to engage max charging while the truck is powered.

With the shorting plug out, it trickle charges the 12V battery. With the shorting plug in, it charges at the full capacity, around 14V. Cutting the green wire and putting a 12V relay across it connected to the ignition on signal allows it to only max charge when the ignition key is on.

Previously, I had the Iota set to only trickle charge with the ignition on. Worked great in summer, but with headlights on both morning and night, and traffic backing up on the highway (lots of braking vacuum) my 12V battery went down to about 9 by the time I got home. So I left the ignition key on to charge the battery while I started to charge my pack. I have the Mini BMS system installed, so in this configuration, it thought I was driving and would not shut off the charger. Luckily I was in the garage and heard the buzzer going off before I overcharged my pack.

Rule #1- Never leave the ignition on when charging!


----------



## EVfun (Mar 14, 2010)

What pins does the Iota plug hook together? I can't find my plug and am considering the same thing.


----------



## gdirwin (Apr 7, 2009)

I also do this, and it works well - this makes the DC/DC work just like the ICE alternator - you get about 14.5V and everything is nice/bright.

Seems strange that your BMS will not shut off the charger when the ignition is on - Iif you are driving, then the BMS low-voltage limit may limit the accelerator (for example) but why would it prevent you from charging? Perhaps a limit on a system with regen? Can you explain more?


----------



## F16bmathis (Jun 6, 2008)

EVfun said:


> What pins does the Iota plug hook together? I can't find my plug and am considering the same thing.


I'll have to go look and see. I'll repost later today. Its a four pin telephone style jack.


----------



## F16bmathis (Jun 6, 2008)

gdirwin said:


> I also do this, and it works well - this makes the DC/DC work just like the ICE alternator - you get about 14.5V and everything is nice/bright.
> 
> Seems strange that your BMS will not shut off the charger when the ignition is on - Iif you are driving, then the BMS low-voltage limit may limit the accelerator (for example) but why would it prevent you from charging? Perhaps a limit on a system with regen? Can you explain more?


Sure, its the Mini BMS advertised on this web site. Its a great system, love it. Its designed so a green LED is lit when the battery voltage is anywhere in the "good" range, high or low. If the voltage starts to go too high (when charging) the green light goes out. Also if the battery voltage goes too low (when driving) the green light goes out. Either way, with the green light out, it sounds a buzzer. 

If the ignition key is off, it assumes your charging and sends a signal to shut off the charger. If the ignition key is on, it assumes your driving and can send a signal to limit the amps the controller puts out.

I was trying to charge my 12V battery while also charging the main pack, so I had the ignition key on. The buzzer let me know something was wrong, as it will normally go off after a second when charging and the batteries become full and the charger is shut off.

A red LED shows you the cell is shunting. This feature can be disabled by cutting the resistor off.

I blew one module when connecting it up. I had connected the last module to the main cable heading to the shut-off switch, but didn't realize I had my charger installed on that connection, so when I connected the module, it sent the 144V from the charged caps in the charger, back to the pack via a module. Second attempt, I connected the main cable to the battery pack first!


----------



## gdirwin (Apr 7, 2009)

F16bmathis said:


> ...Either way, with the green light out, it sounds a buzzer.
> 
> If the ignition key is off, it assumes your charging and sends a signal to shut off the charger. If the ignition key is on, it assumes your driving and can send a signal to limit the amps the controller puts out.


Still doesn't make sense - is there only 1 signal (to the buzzer) that indicates the cells are within the normal range? Or are there 2 signals - one to shut off the charger, and a 2nd signal to limit the controller amps...


----------



## dimitri (May 16, 2008)

gdirwin said:


> Still doesn't make sense - is there only 1 signal (to the buzzer) that indicates the cells are within the normal range? Or are there 2 signals - one to shut off the charger, and a 2nd signal to limit the controller amps...


This behavior is by design. 2 separate relays are used, one for LVC and one for HVC. HVC is latching and uses Ignition as a reset to unlatch HVC relay, hence the Ignition being on would inhibit HVC function.

The manual clearly states not to charge with Ignition on.

Of course MiniBMS is very flexible, so instead of Ignition you could wire a push button for BMS reset, if you wanted to charge with Ignition on for some reason. I just didn't see such reason when designing the system, so I used Ignition as a reset signal.

Hope this makes sense now.


----------



## dimitri (May 16, 2008)

F16bmathis said:


> So I left the ignition key on to charge the battery while I started to charge my pack. I have the Mini BMS system installed, so in this configuration, it thought I was driving and would not shut off the charger. Luckily I was in the garage and heard the buzzer going off before I overcharged my pack.
> 
> Rule #1- Never leave the ignition on when charging!


Since you have adjustable charger, why not dial it down so it stops on its own when all cells reach shunting level? This way BMS will only shut it off in case of unforseen events.

Sorry, I didn't mean to hijack the main purpose of this thread. I have same IOTA DC-DC and I never had the plug in it. Sounds like your 12V battery is either too small or dying, maybe it would make sense to fix the battery as well.


----------



## gdirwin (Apr 7, 2009)

I understand now- thanks for the explanation.

Perhaps you could use a switch on the fuel door - ie if you close the fuel door (to indicate you are finished charging) then the latching relay would get reset. 

It may be simpler to use the ignition 12V signal to inhibit charging directly (through an AC relay on the charger input).

Or simpler yet, do nothing and remember to never charge with the ignition on...


----------



## tomofreno (Mar 3, 2009)

> Since you have adjustable charger, why not dial it down so it stops on its own when all cells reach shunting level?


 I have found this isn't very reliable with my Manzanita, unless you charge to something like 90-95% capacity at the highest cell temperature and highest charge current you will use and lower capacity at all other settings, due to variation in hitting the charger limit voltage with cell temperature and charging current. For example, I have observed about a 20Ah difference in charge into the pack with about a 10 F difference in cell temperature, when charging is ended by the charger hitting its preset voltage limit then timing out. In addition, if the starting SOC is too low, there may not be sufficient time for the charger to time out after hitting the voltage limit, before overcharging. Good to have the minibms there to cut it off. Also good to check it yourself near the end of charge just in case. As much redundancy as you can get. Thought I would just give this warning - now back to the advertised topic.


----------



## F16bmathis (Jun 6, 2008)

dimitri said:


> Since you have adjustable charger, why not dial it down so it stops on its own when all cells reach shunting level? This way BMS will only shut it off in case of unforseen events.
> 
> Sorry, I didn't mean to hijack the main purpose of this thread. I have same IOTA DC-DC and I never had the plug in it. Sounds like your 12V battery is either too small or dying, maybe it would make sense to fix the battery as well.


I do have it dialed in so it usually stops before the bms kicks in, but I was wanting to get the batteries level as I have one from another source. MiniBMS seems to have leveled them pretty good.

My Iota has worked great all summer, but now as I use headlights, vacuum pump and everything to and from work, the battery seems to be getting lower every day. Could be a bad battery. Its been overcharged cause as usual I read the manual then forgot about it, then plugged the shorting plug in and let it cook during an auto show. Good thing I was able to hear it sizzling and feel the heat. Left it unplugged after that. Seems to work pretty good with the shorting plug helping out so far...


----------



## F16bmathis (Jun 6, 2008)

EVfun said:


> What pins does the Iota plug hook together? I can't find my plug and am considering the same thing.


Looking at the pin side, with the locking lever on the bottom, the wires are green, black, green, black. Its a four pin phone style jack.

Leave the black looped, and install a 12V relay betwen the green wires to open them when the car is not running.

I'm keeping an eye on the battery to ensure I don't overcharge, shouldn't happen as I use alot of accessory juice.


----------



## EVfun (Mar 14, 2010)

Thank you, I want to be sure I understand you. You are looking at the end you plug into the Iota, with the lock lever down, right? There are 2 loops of wire, one green and one black and you listed the colors (green, black, green, black) from left to right, correct? 

I'm thinking I need a little Lithium battery for my 12 volt system and bumping it up will bring the charge voltage closer to 3.6 volts. Without bumping the voltage up my Iota wouldn't quite get them to 3.4 volts per cell. I'm planning to use 4, 10 amp hour Headway cells in the Buggy because it will need a 12 volt battery or the Zilla (every 1400 lb. car needs a Zilla, right) will freak out when I hit the headlights.


----------



## F16bmathis (Jun 6, 2008)

EVfun said:


> Thank you, I want to be sure I understand you. You are looking at the end you plug into the Iota, with the lock lever down, right? There are 2 loops of wire, one green and one black and you listed the colors (green, black, green, black) from left to right, correct?
> 
> I'm thinking I need a little Lithium battery for my 12 volt system and bumping it up will bring the charge voltage closer to 3.6 volts. Without bumping the voltage up my Iota wouldn't quite get them to 3.4 volts per cell. I'm planning to use 4, 10 amp hour Headway cells in the Buggy because it will need a 12 volt battery or the Zilla (every 1400 lb. car needs a Zilla, right) will freak out when I hit the headlights.


Yup! Mine can now handle headlights, heat at full blast, radio and everything else, maybe even widsheild wipers too!!


----------

