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Anyone have photos from inside the Fit EV Battery Case?

Posted: Mon Dec 23, 2019 9:14 pm
by Natalya
Hi everyone, I'm a first-generation Honda Insight owner, and I come to this forum in search of knowledge about Fit EV batteries. The old Insights all have suffered hybrid battery module failure due to their age, but some of us have replaced our old batteries with used Honda Fit EV batteries. The LTO chemistry the Fit EVs use is coincidentally mostly compatible with the electronics the old Insight uses to manage its hybrid battery pack.

The Fit EV battery modules come in pairs of two sub-packs bolted together. Each sub-pack has 12 Toshiba SCiB cells, so 24 cells per module. I'm running a pack that consists of 3 of these modules, so 72 cells, in my 2000 Honda Insight.

Each sub-pack has a circuit board on top (once you pop the cover off) that is connected via CAN bus to the ECM. The connection from each sub-pack to the main wiring harness is done with a little wire pigtail. There's a Honda part number written on the pig tail:


This number is similar to some 2017 model year Honda Accord Hybrid wire part numbers. For example, one of its wire harnesses has part number 1N310-5K1-N00. What I'm wondering is if someone could take a photo or two of the wire-harness side of one of these connectors. Sometimes Honda will re-use the same connector across different models of vehicle. The same one may for example have been used in the Accord Hybrid. A couple members of an Insight forum I participate in have gotten the Fit EV BMS (battery management system) to activate and read cell voltages using CAN readers, but they had to solder wires directly to the BMS to interface with it. Using wired connections would be greatly preferred, especially if we didn't have to cut the connectors up.

Some other questions we have about the Fit EV batteries are about how the batteries are cooled, how hot do they get, how are they installed, etc. The modules we've gotten aren't totally identical. Some of them have 4 mounting tabs on each side, others have 5. We don't know the reasons for any differences like that because we've never seen photos of one of the battery cases or photos from inside it or photos of the fans/ducts/etc used for cooling.

If anyone ever took photos like that, or if anyone still has a Fit EV and is willing to take such photos, it would be of immense help to us and we would be forever thankful.

- Natalya from Insight Central

Re: Anyone have photos from inside the Fit EV Battery Case?

Posted: Tue Dec 24, 2019 2:59 pm
by blownb310
Very interesting post. No one that I know of has ever gotten their hands on a used Fit EV battery for photos or otherwise. Where are you and others getting your used modules from? Is Honda selling them after dismantling the cars? If so, where please?

Re: Anyone have photos from inside the Fit EV Battery Case?

Posted: Tue Dec 24, 2019 11:55 pm
by Natalya

Re: Anyone have photos from inside the Fit EV Battery Case?

Posted: Wed Dec 25, 2019 11:46 am
by blownb310
Thank you Natalya. Regarding photos, unless someone here knows a Honda employee that is dismantling the cars, no one else is allowed to open a battery pack. Failures were extremely rare so even dealers won't have any experience with them.

Re: Anyone have photos from inside the Fit EV Battery Case?

Posted: Sun May 17, 2020 9:06 am
by VincentRapide
Nice to hear that I'm not allowed to open the case on my 24 cell 1.1 kwh FIT_EV module. :lol:

Someday I may open up the plastic case but as received it is a nice 60v (max) battery unit 24 cells in series. It can be split
(parallelled) to make a 30v pack. LTO chemistry means it is: (a) heavy (b) bulletproof, no fire hazard (c) safe operation at
below-freezing temps (d) lower voltages per cell compared to other chemistries and (e) near infinite charge cycles.

Installing these modules into a hybrid vehicle and expecting to connect the FIT BMS to that vehicle's system
seems highly unlikely to say the least. Does the hybrid actually have LTO cells? You can forget using any BMS
and just let the cells run alone, assuming you already have the cells all up to 2.4v (96% of absolute max). Then
monitor the cell voltages as you put mileage on the car. They should stay close for quite some time. Spotting
weak cells, if any, is what you want to do first. You can have a custom BMS made cheaply.

Factoid: some early ev and ebikes used Nickel Metal Hydride (NI-MH) ancient chemistry!