question

I have a 24v domestic all Victron Lithium battery management system and four of the Smart 100Ah LiFePo4's that have to dump a charge voltage to two lead acid batteries. This is done through the VE Bus and switches the voltage between the two sets of batteries. I have had to fit a Sterling Power Pro Ultra Battery to Battery 24v-24v charger to deal with this. WHY? I wanted this system to be all Victron as if it was a 12 volt system a BMS 12/200 would have done the job, but Victron don't do this for a 24 volt system.. I know I could have fitted a Buck Boost at £500.00 but its a shame I had to go for a Sterling Power product.. I still have a problem which is when the engine is at low revs you can hear the engine fluctuating as it switches on and off and it uses a fan which I wonder how reliable it will be. Hope someone can help! Del  