Hey Everyone, I've seen lithium prices drop significantly on ebay; so, has anyone thought of just building a 240v-250v battery (if I remember, someone said this the voltage needed to charge the HV battery) to directly charge the HV battery. I am trying to avoid the expensive converter.
Yes it has been done before. A whole thread on it using a BMSplus or BMS2. For a Prius Generation 2 only. Planing CanView and BMS+ conversion with lithium | Page 41 | PriusChat Also this thread using a replacement OEM battery ECU YAPiP - recreating pEEf's approach | Page 9 | PriusChat Or Update and technical details on my PHEV project | PriusChat If you have a Generation 3 Prius or later I would stick with using a Converter.
I also miss topics on converting gen 3 Prius, why would you stick with DC-DC convertor, safety reasons or something else?
The battery ECU needs to be fooled. It is programmed to think that there is only a NIMh 6.5AH HV battery. The SOC becomes really low and starts the ICE to charge a HV battery that it thinks has a low SOC. Where in reality you have a 20ah lifepo4 battery connected in parallel. There is just no device available to fool the battery ECU for a Gen3. Possibly the design of the Gen3 makes it harder than generation 2.
Interesting, how does DC-DC converter fool SOC? With applying constant voltage? So building a higher voltage battery as OP stated wouldn't eliminate that?
The converter is a trickle charger about 16 amps at most. Every now and then the battery ECU does a SoC check based on voltage and adjusts SoC accordingly so converter gets under the radar being such a small current. Even so there are still times the converter will cause a DTC. The Prius 2nd generation will allow a 16 amp discrepancy between the current measured by the battery ECU and that measured by the inverter. If discrepancy in current exceeds 16 amps a DTC is usually thrown. The converter is connected so that the current is seen by the battery ECU going into the OEM HV battery. As instructed by Enginer. A second Lifepo4 HV battery is connected in parallel with the OEM HV battery and therefor current cannot be seen by the OEM battery ECU going into the OEM HV battery.
