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I have a 24v domestic Lithium battery system and the Smart LiFePo4's have to dump a charge voltage to another battery. The starter battery is a 12v system so I have to carry two 12v LA batteries in parallel to allow this to happen. I would like this voltage to be regulated to a 12v charging voltage through a Cyrix battery combiner so it will charge the starter battery when the Lithium batteries are full. Hope you can Help
You could use a DC-DC Buck / Boost converter for this.
Hi. This isn't a direct answer, just a coupla ways to workaround it:
I use an Orion DC/DC converter to drop to 12V. Supposedly adjustable V (never tried), just single stage, but enough to maintain a starter batt. I would normally use that for 12V loads.
If you have an inverter, just a tiny cheapy batt charger on a gpo will satisfy. I do that with a $5 timer set for sun time.
But ha, my starter batts are also used for lights, etc. and are 900Ah @ 12V. The Orion is switched off while I 'use up' (suck the last life from) some old Pb's. Yeh I know, always best to keep the starter batts separate, but the Orion (or jumper leads) are backup from the 48V house bank.
Just sayin though, while you await Victron to expand the product range. Frightening already :)
Hi Kirby, I think the DC-DC Buck / Boost converter can only take a input of 12 volts and give a output of 24v and I need it the other way round.
I need it to take the charging voltage of 28.1 going in (when the smart lithium's can't take a charge) and give me a 14.5 voltage going out so it still charges the Starter lead acid battery..
Thanks for your help!
Del
Thanks John, but I want to keep the system all Victron as the batteries are very expensive and I don't want to damage them.
Thanks again!
Del
Noble sentiment. My Orion is a Victron product, my ac batt charger just an old 'unmentionable' brand I've had likely 40 years. If I needed another it would be a blue one.
You could also do what you want with a small pwm or mppt charge controller. Blue preferred of course, but sometimes I head for the spares bin.
Seems you have a few options..
Hi Kirby/John, Thanks again! I have just seen the price of the Buck-Boost DC-DC Converter and its £500.00 so the Orion DC/DC Converter seems to be the better option at £55.00. Do both these products put a charging voltage into the 12v lead acid starter battery (ie 14.5v)?
Its much appreciated!
Del
The Orion is a pretty simple device. It's a dc/dc converter and comes in a few sizes. Adjustable V (no charge program), but would suffice to float a non-cycling bank. Adjustable via screwdriver? ( I haven't tried). Mine has a pair of 'remote' terminals that I expect could be used to operate a timer or remote switch for convenience. Even via a signal from your Li's when they're full?
But it all depends on what your 'starter' batts are being used for. If they just sit there 24/7 awaiting start duty, then it would seem silly adding high end kit. Maybe a weekly or monthly touch-up would suffice?
And if you do actually have an inverter giving ac from your Li's, then the options widen. A little blue ac sourced charger would work then too.
