I am think of adding a small DC-DC 24/12 converter to provide a float to my lead acid starter battery. My main leisure battery is 24v. I’m considering the 5A non-isolated at 12.7V output version and will connect it to the Smart Solar (24v) load output - so I can easily activate it.
Can the DC-DC converter tolerate its output being to a higher voltage source, for example when the alternator is running? Documentation does not mention reverse current protection nor warn against this application.
Normal dc/dc converter topology is usually proof against slightly elevated output voltages being applied (i.e. voltage being applied to the output). Little or no reverse current should flow, and the dc/dc will idle.
You should really be looking at the charger, not the converter. You should also get the isolated one if the 12V system is unable to tolerate 24V. In case it fails internally and you see 24V on the 12V side. The smallest 24/12V charger is 20A.
Thank you Owen. My set up is in a van that already has a shared ground, which is why I ignored the isolated version but I take your point as it may provide an additional layer of protection for certain failures.
Yeah, the MPPT non-isolated fault is common. Seeing the solar panel voltage on the output does a lot of damage. My boat has separate systems with no shared ground, all isolated, so it works for me, and the battery is protected from the MPPT output by using a battery protect to disconnect if the MPPT fails. A fault on the water could be fatal.
Ahh, so you’re using it for over-voltage protection? So I could also use a smaller 65A amp battery protect on the outlet of the DC-DC converter, to protect my 12V consumers, should the converter pass 24V in fault.
Yes, if you are going from 12V to 24V, the worst that can happen is the 24V side only sees 12V. But if there is a 24V battery on the other side, you can get 24V on the 12V system. If you want to drop down from 24V to 12V and you get a failure, you will 100% get 24V on the 12V system. A battery protect will disconnect if the voltage is too high going to the 12V.
You might also be able to bypass the feedback if you think it’s a problem by using the remote on the battery protect. It’s really up to you how much protection you need. An isolated charger will protect you from a lot of failures compared to a simple converter. It also gives you options like start voltage and rebulk settings you dont get with a converter. Have a look at the demo menu and see what will be lacking on the converter vs the charger.
It happens, yes. But its far from common. I would even go as far as saying those MPPTs failed due to not respecting the input voltage limit, so its user error. Ive also never saw an Orion fail shorted.