Fuel Economy, Hypermiling, EcoModding News and Forum - EcoModder.com - View Single Post - DIY "Mild" Plug-in Prius Project: Grid-powering the 12v side w/ deep cycle batteries

unixrocks · 08-16-2010, 07:30 AM

Ok taking another look at the DIY charger I think the only thing needed to make this viable as a onboard charger is the addition of a relay between the + terminal of the battery and the final leg of the charger to keep the charger from sucking power from the battery when its not on. A diode wont do because the circuit wouldnt be able to tell what the current voltage is on the battery but relays are pretty cheap anyways.

Other than the relay addition and the upgrade to a 16V Transformer I think the circuit would work fine.

If my thinking is right the resting voltage on this battery is 14.7-14.9V. So switching off the converter the battery should be able to handle the electronics just fine for short trips. (50AH means 300watt load would give it about 2.5 hours of run time)

When the battery gets low (too bad the energy screen dont show the system voltage - would have to rig a voltage meter but I think I saw one that plugs into the cigarette lighter somewhere) switching on the converter would essentially trickle charge the battery and provide power to the system until you can plug in again.

Now....anyone know where that converter is and which wire to put a switch inline on to turn the thing off and on?

And in re-reading the previous posts it seems like this isnt even neccesary since the converter wont kick in until the voltage on the battery gets low which as was pointed out in an earlier post this is a mild discharge (13.8 is about 35% discharge which is fine for this battery) so in theory all you should have to do is put this battery in, charge at night and see instant gains and just when its going into the "time to charge it zone" the converter will kick in and trickle charge it at 13.8V while running the electronics.....in theory anyways. Was I reading that right about the converter not kicking on until it sees 13.8V?

Another bonus is this battery is AGM so it wont vent - especially not at the low voltages the converter throws at it. The only drawback is the battery is a bit wide so not sure how great it would fit in the stock battery holder.

08-16-2010, 07:30 AM	#65 (permalink)
unixrocks EcoModding Lurker Join Date: Aug 2010 Location: USA Posts: 20 Thanks: 1 Thanked 1 Time in 1 Post	Ok taking another look at the DIY charger I think the only thing needed to make this viable as a onboard charger is the addition of a relay between the + terminal of the battery and the final leg of the charger to keep the charger from sucking power from the battery when its not on. A diode wont do because the circuit wouldnt be able to tell what the current voltage is on the battery but relays are pretty cheap anyways. Other than the relay addition and the upgrade to a 16V Transformer I think the circuit would work fine. If my thinking is right the resting voltage on this battery is 14.7-14.9V. So switching off the converter the battery should be able to handle the electronics just fine for short trips. (50AH means 300watt load would give it about 2.5 hours of run time) When the battery gets low (too bad the energy screen dont show the system voltage - would have to rig a voltage meter but I think I saw one that plugs into the cigarette lighter somewhere) switching on the converter would essentially trickle charge the battery and provide power to the system until you can plug in again. Now....anyone know where that converter is and which wire to put a switch inline on to turn the thing off and on? And in re-reading the previous posts it seems like this isnt even neccesary since the converter wont kick in until the voltage on the battery gets low which as was pointed out in an earlier post this is a mild discharge (13.8 is about 35% discharge which is fine for this battery) so in theory all you should have to do is put this battery in, charge at night and see instant gains and just when its going into the "time to charge it zone" the converter will kick in and trickle charge it at 13.8V while running the electronics.....in theory anyways. Was I reading that right about the converter not kicking on until it sees 13.8V? Another bonus is this battery is AGM so it wont vent - especially not at the low voltages the converter throws at it. The only drawback is the battery is a bit wide so not sure how great it would fit in the stock battery holder. Last edited by unixrocks; 08-16-2010 at 07:39 AM..