JohnGarziglia
New Member
I have a question on alternator charging of LiFePO4 batteries which hopefully does not plow through ground already discussed in other posts. Apologies for the length of the question but I wanted to give adequate details.
The alternator in the OEM setup in my motorhome is connected to the house lead acid batteries through a merge solenoid which is controlled by Spyder electronics allowing for: (1) the alternator to charge the house batteries once the chassis batteries are full; (2) allowing for a shore connection or the generator to charge the chassis batteries once the house batteries are full; and (3) bridging the house and chassis batteries together to allow for an emergency start of either the engine or the generator. For the exact specs of this OEM setup, see: https://liferebooted.net/2018-phaeton-40ih/Spyder-Battery-Merge-Spec.pdf.
Here is the setup I am contemplating. I intend to install LiFePO4 batteries in place of the OEM lead acid house batteries. In order to keep from burning out the alternator, I will install a Precision Circuits, Inc. Li-BIM 225 (https://www.precisioncircuitsinc.com/wp-content/uploads/2019/10/00-10041-26x-Li-BIM-Rev1.pdf) in accord with its specifications in place of the merge solenoid. The Spyder controls of the merge solenoid described in the link in the above paragraph will be decommissioned. Instead the dash switch for manually connecting the batteries together in an emergency start situation, which previously went through the Spyder controls, will go directly to the appropriate connections on the Li-BIM 225 along with a 12 volts ignition connection.
But, as the literature for the Li-BIM 225 states, the alternator connected through the Li-BIM 225 will not fully charge the LiFePO4 house batteries. In addition, due to the cycling characteristics of the Li-BIM 225, it will charge the house batteries for only a portion of a drive, disconnecting the charge to keep the alternator from overheating.
Is there any reason why I could also not install two 30-amp DC-to-DC chargers between the alternator and the LiFePO4 house batteries to allow the alternator to continue charging the house batteries at a lower current when the Li-BIM-225 disconnects? This would allow for a fast charging of the LiFePO4 batteries with a high current (the motorhome has a 250-amp alternator) for an initial time period, and then when the Li-BIM 225 disconnects the alternator from the LiFePO4 house batteries keeping the alternator from overheating, the charging of the LiFePO4 house batteries would continue at no more than 60 amps through the DC-to-DC charger.
I have not seen anyone else use both a Li-BIM 225 battery isolation manager, and DC-to-DC chargers, with an alternator. Is there any reason this setup should not work – am I missing something? Any observations and advice are much appreciated.
The alternator in the OEM setup in my motorhome is connected to the house lead acid batteries through a merge solenoid which is controlled by Spyder electronics allowing for: (1) the alternator to charge the house batteries once the chassis batteries are full; (2) allowing for a shore connection or the generator to charge the chassis batteries once the house batteries are full; and (3) bridging the house and chassis batteries together to allow for an emergency start of either the engine or the generator. For the exact specs of this OEM setup, see: https://liferebooted.net/2018-phaeton-40ih/Spyder-Battery-Merge-Spec.pdf.
Here is the setup I am contemplating. I intend to install LiFePO4 batteries in place of the OEM lead acid house batteries. In order to keep from burning out the alternator, I will install a Precision Circuits, Inc. Li-BIM 225 (https://www.precisioncircuitsinc.com/wp-content/uploads/2019/10/00-10041-26x-Li-BIM-Rev1.pdf) in accord with its specifications in place of the merge solenoid. The Spyder controls of the merge solenoid described in the link in the above paragraph will be decommissioned. Instead the dash switch for manually connecting the batteries together in an emergency start situation, which previously went through the Spyder controls, will go directly to the appropriate connections on the Li-BIM 225 along with a 12 volts ignition connection.
But, as the literature for the Li-BIM 225 states, the alternator connected through the Li-BIM 225 will not fully charge the LiFePO4 house batteries. In addition, due to the cycling characteristics of the Li-BIM 225, it will charge the house batteries for only a portion of a drive, disconnecting the charge to keep the alternator from overheating.
Is there any reason why I could also not install two 30-amp DC-to-DC chargers between the alternator and the LiFePO4 house batteries to allow the alternator to continue charging the house batteries at a lower current when the Li-BIM-225 disconnects? This would allow for a fast charging of the LiFePO4 batteries with a high current (the motorhome has a 250-amp alternator) for an initial time period, and then when the Li-BIM 225 disconnects the alternator from the LiFePO4 house batteries keeping the alternator from overheating, the charging of the LiFePO4 house batteries would continue at no more than 60 amps through the DC-to-DC charger.
I have not seen anyone else use both a Li-BIM 225 battery isolation manager, and DC-to-DC chargers, with an alternator. Is there any reason this setup should not work – am I missing something? Any observations and advice are much appreciated.