lithium conversion questions

[DonTom]

If you mean this things, yes there is one but it shows a voltage on both sides.

That's a common DC circuit breaker. The little thingy right above the words "42 volts DC" will popout when it trips. Simply push it back into reset.

-Don- Roll, AZ (rest stop)

 

[tombuchanan]

I finally took a trip to test how the lithium conversion worked and discovered a problem. When the dc to dc charger is topping off the batteries with more than 14 volts, my 12 volt navigation system and tv will lose power and then restart every couple minutes. I ended up having to turn the charger on only at night when I wasn't using those. Now that I'm home, I changed the maximum voltage of the charger to 13.5 to avoid having to do this. I understand this won't charge the lithiums all the way but I think its more inconvenient to have to manually switch it on and off.

 

[Gary RV_Wizard]

Seems to me you want the DC-DC unit only on the path to the house batteries and not feeding the entire chassis 12v system. Is your nav & tv using house or chassis 12v? And is it a 12v tv, or is the 12v on some sort of control/relay circuit?

Most vehicle electronics can tolerate 14.4v because that's the typical max alternator output, but even that voltage probably shortens the life is sustained very long.

 

[Mark_K5LXP]

my 12 volt navigation system and tv will lose power and then restart every couple minutes.

There's more than one piece of affected equipment there so I'd be looking at what powers these. 14.4V is not an unexpected voltage in a mobile environment so I'd be looking for what's interrupting the power to these devices.

Mark B.
Albuquerque, NM

 

[Isaac-1]

I would be taking voltage measurements too, something does not seem right, in Lithium mode it should not be outputting more than 14.2-14.4 VDC, which matches the maximum output voltage of many automotive alternators, and it is common for some alternators to output 14.4VDC or even slightly higher for the first couple of minutes after they start up.

 

[tombuchanan]

Isaac, don't you think that even if a generator outputs 14.4 initially, that voltage would be dropped by the lead batteries it is going into. I think that is the difference here, the lithiums allow a higher voltage. Mark, the dc to dc connects to the batteries which are connected to everything that runs on the 12 volts like the lights, nav, and tvs. I don't see how a set of lead acids would pass on 14.4. Don't you think their internal resistance would always drop that down to the 13's? Gary, for the dc to dc charger not to be on the same circuit as the house, I'd have to put a switch in there which leads to a similar work around I'm using now where I turn the DC to DC on only when I'm not using the nav and tvs.

 

[Mark_K5LXP]

even if a generator outputs 14.4 initially, that voltage would be dropped by the lead batteries it is going into

If the batteries were low then you would be right, the converter would likely be in constant current mode and terminal voltage in the 13's but not if the batteries are near full or full. 14.4 is absorb voltage and part of the expected charge profile that is normally held there for a few hours. If the batteries are >80% charged the current will be low, and if presented, voltage well into the 15V range would still not result in much change in accepted current.

Mark B.
Albuquerque, NM

 

[Isaac-1]

Mark pretty much covered it, my thought is if a voltage source either alternator or converter were to have an output voltage of 14.4VDC or higher even briefly, and the issue is overvoltage shutdown of the devices, that there are corner case situations that would occur time to time that would set this off even with lead acid batteries, as this voltage would be raising the voltage on the bus, particularly in case of a nearly fully charged lead acid battery